//! Hunk a change from a pristine and a working copy.
use crate::changestore::ChangeStore;
use crate::diff;
pub use crate::diff::Algorithm;
use crate::path::{Components, components};
use crate::pristine::*;
use crate::small_string::SmallString;
use crate::working_copy::WorkingCopyRead;
use crate::{HashMap, HashSet};
use crate::{alive::retrieve, text_encoding::Encoding};
use crate::{change::*, changestore::FileMetadata};
use parking_lot::Mutex;
use std::collections::VecDeque;
use std::sync::Arc;

#[derive(Error)]
pub enum RecordError<C: std::error::Error + 'static, W: std::error::Error, T: GraphTxnT + TreeTxnT>
{
    #[error("Changestore error: {0}")]
    Changestore(C),
    #[error("Working copy error: {0}")]
    WorkingCopy(W),
    #[error("System time error: {0}")]
    SystemTimeError(#[from] std::time::SystemTimeError),
    #[error(transparent)]
    Txn(#[from] TxnErr<T::GraphError>),
    #[error(transparent)]
    Tree(#[from] TreeErr<T::TreeError>),
    #[error(transparent)]
    Diff(#[from] diff::DiffError<C, T>),
    #[error("Path not in repository: {0}")]
    PathNotInRepo(String),
    #[error(transparent)]
    Io(#[from] std::io::Error),
}

impl<C: std::error::Error, W: std::error::Error, T: GraphTxnT + TreeTxnT> std::fmt::Debug
    for RecordError<C, W, T>
{
    fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            RecordError::Changestore(e) => std::fmt::Debug::fmt(e, fmt),
            RecordError::WorkingCopy(e) => std::fmt::Debug::fmt(e, fmt),
            RecordError::SystemTimeError(e) => std::fmt::Debug::fmt(e, fmt),
            RecordError::Txn(e) => std::fmt::Debug::fmt(e, fmt),
            RecordError::Tree(e) => std::fmt::Debug::fmt(e, fmt),
            RecordError::Diff(e) => std::fmt::Debug::fmt(e, fmt),
            RecordError::PathNotInRepo(p) => write!(fmt, "Path not in repository: {}", p),
            RecordError::Io(e) => std::fmt::Debug::fmt(e, fmt),
        }
    }
}

impl<C: std::error::Error + 'static, W: std::error::Error + 'static, T: GraphTxnT + TreeTxnT>
    std::convert::From<crate::output::FileError<C, T>> for RecordError<C, W, T>
{
    fn from(e: crate::output::FileError<C, T>) -> Self {
        match e {
            crate::output::FileError::Changestore(e) => RecordError::Changestore(e),
            crate::output::FileError::Io(e) => RecordError::Io(e),
            crate::output::FileError::Txn(t) => RecordError::Txn(t),
        }
    }
}

/// A change in the process of being recorded. This is typically
/// created using `Builder::new`.
pub struct Builder {
    pub(crate) rec: Vec<Arc<Mutex<Recorded>>>,
    recorded_inodes: Arc<Mutex<HashMap<Inode, Position<Option<ChangeId>>>>>,
    deleted_vertices: Arc<Mutex<HashSet<Position<ChangeId>>>>,
    pub force_rediff: bool,
    pub ignore_missing: bool,
    pub contents: Arc<Mutex<Vec<u8>>>,
    new_root: Arc<Mutex<Option<(Position<Option<ChangeId>>, u64)>>>,
}

#[derive(Debug)]
struct Parent {
    basename: String,
    metadata: InodeMetadata,
    encoding: Option<Encoding>,
    parent: Position<Option<ChangeId>>,
}

/// The result of recording a change:
pub struct Recorded {
    /// The "byte contents" of the change.
    pub contents: Arc<Mutex<Vec<u8>>>,
    /// The current records, to be lated converted into change operations.
    pub actions: Vec<Hunk<Option<ChangeId>, LocalByte>>,
    /// The updates that need to be made to the ~tree~ and ~revtree~
    /// tables when this change is applied to the local repository.
    pub updatables: HashMap<usize, InodeUpdate>,
    /// The size of the largest file that was recorded in this change.
    pub largest_file: u64,
    /// Whether we have recorded binary files.
    pub has_binary_files: bool,
    /// Timestamp of the oldest changed file. If nothing changed,
    /// returns now().
    pub oldest_change: std::time::SystemTime,
    /// Redundant edges found during the comparison.
    pub redundant: Vec<crate::alive::Redundant>,
    /// Force a re-diff
    force_rediff: bool,
    deleted_vertices: Arc<Mutex<HashSet<Position<ChangeId>>>>,
    recorded_inodes: Arc<Mutex<HashMap<Inode, Position<Option<ChangeId>>>>>,
    new_root: Arc<Mutex<Option<(Position<Option<ChangeId>>, u64)>>>,
}

impl Default for Builder {
    fn default() -> Self {
        Self {
            rec: Vec::new(),
            recorded_inodes: Arc::new(Mutex::new(HashMap::default())),
            force_rediff: false,
            ignore_missing: false,
            deleted_vertices: Arc::new(Mutex::new(HashSet::default())),
            contents: Arc::new(Mutex::new(Vec::new())),
            new_root: Arc::new(Mutex::new(None)),
        }
    }
}

impl Builder {
    /// Initialise a `Builder`.
    pub fn new() -> Self {
        Self::default()
    }

    pub fn recorded(&mut self) -> Arc<Mutex<Recorded>> {
        let m = Arc::new(Mutex::new(self.recorded_()));
        self.rec.push(m.clone());
        m
    }

    fn recorded_(&self) -> Recorded {
        Recorded {
            contents: self.contents.clone(),
            actions: Vec::new(),
            updatables: HashMap::default(),
            largest_file: 0,
            has_binary_files: false,
            oldest_change: std::time::SystemTime::UNIX_EPOCH,
            redundant: Vec::new(),
            force_rediff: self.force_rediff,
            deleted_vertices: self.deleted_vertices.clone(),
            recorded_inodes: self.recorded_inodes.clone(),
            new_root: self.new_root.clone(),
        }
    }

    /// Finish the recording.
    pub fn finish(mut self) -> Recorded {
        if self.rec.is_empty() {
            self.recorded();
        }
        let mut it = self.rec.into_iter();
        let mut result = if let Ok(rec) = Arc::try_unwrap(it.next().unwrap()) {
            rec.into_inner()
        } else {
            unreachable!()
        };
        for rec in it {
            let rec = if let Ok(rec) = Arc::try_unwrap(rec) {
                rec.into_inner()
            } else {
                unreachable!()
            };
            let off = result.actions.len();
            result.actions.extend(rec.actions.into_iter());
            for (a, b) in rec.updatables {
                result.updatables.insert(a + off, b);
            }
            result.largest_file = result.largest_file.max(rec.largest_file);
            result.has_binary_files |= rec.has_binary_files;
            if result.oldest_change == std::time::UNIX_EPOCH
                || (rec.oldest_change > std::time::UNIX_EPOCH
                    && rec.oldest_change < result.oldest_change)
            {
                result.oldest_change = rec.oldest_change
            }
            result.redundant.extend(rec.redundant.into_iter())
        }
        debug!(
            "result = {:?}, updatables = {:?}",
            result.actions, result.updatables
        );
        result
    }
}

/// An account of the files that have been added, moved or deleted, as
/// returned by record, and used by apply (when applying a change
/// created locally) to update the trees and inodes databases.
#[derive(Debug, Hash, PartialEq, Eq)]
pub enum InodeUpdate {
    Add {
        /// Inode vertex in the graph.
        pos: ChangePosition,
        /// `Inode` added by this file addition.
        inode: Inode,
    },
    Deleted {
        /// `Inode` of the deleted file.
        inode: Inode,
    },
}

#[derive(Debug, Clone)]
struct RecordItem {
    v_papa: Position<Option<ChangeId>>,
    papa: Inode,
    inode: Inode,
    basename: String,
    full_path: String,
    metadata: InodeMetadata,
}

impl RecordItem {
    fn root() -> Self {
        RecordItem {
            inode: Inode::ROOT,
            papa: Inode::ROOT,
            v_papa: Position::OPTION_ROOT,
            basename: String::new(),
            full_path: String::new(),
            metadata: InodeMetadata::new(0, true),
        }
    }
}

/// Ignore inodes that are in another channel
fn get_inodes_<T: ChannelTxnT + TreeTxnT, C: ChangeStore, W: WorkingCopyRead>(
    txn: &ArcTxn<T>,
    channel: &ChannelRef<T>,
    inode: &Inode,
) -> Result<Option<Position<ChangeId>>, RecordError<C::Error, W::Error, T>> {
    let txn = txn.read();
    let channel = channel.r.read();
    Ok(get_inodes::<_, C, W>(&*txn, &*channel, inode)?.map(|x| *x))
}

fn get_inodes<'a, T: ChannelTxnT + TreeTxnT, C: ChangeStore, W: WorkingCopyRead>(
    txn: &'a T,
    channel: &T::Channel,
    inode: &Inode,
) -> Result<Option<&'a Position<ChangeId>>, RecordError<C::Error, W::Error, T>> {
    if let Some(vertex) = txn.get_inodes(inode, None)? {
        if let Some(e) = iter_adjacent(
            txn,
            txn.graph(channel),
            vertex.inode_vertex(),
            EdgeFlags::PARENT,
            EdgeFlags::all(),
        )?
        .next()
        {
            if e?.flag().is_parent() {
                return Ok(Some(vertex));
            }
        }
        Ok(None)
    } else {
        Ok(None)
    }
}

struct Tasks {
    stop: bool,
    t: VecDeque<(
        RecordItem,
        Position<ChangeId>,
        Arc<Mutex<Recorded>>,
        Option<Position<Option<ChangeId>>>,
    )>,
}

impl Builder {
    pub fn record<
        T,
        W: WorkingCopyRead + Clone + Send + Sync + 'static,
        C: ChangeStore + Clone + Send + 'static,
    >(
        &mut self,
        txn: ArcTxn<T>,
        diff_algorithm: diff::Algorithm,
        stop_early: bool,
        diff_separator: &regex::bytes::Regex,
        channel: ChannelRef<T>,
        working_copy: &W,
        changes: &C,
        prefix: &str,
        _n_workers: usize,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        T: ChannelMutTxnT + TreeTxnT + Send + Sync + 'static,
        T::Channel: Send + Sync,
        <W as WorkingCopyRead>::Error: 'static,
    {
        let work = Arc::new(Mutex::new(Tasks {
            t: VecDeque::new(),
            stop: false,
        }));
        let mut workers: Vec<std::thread::JoinHandle<_>> = Vec::new();
        for t in 0..0 {
            // n_workers - 1 {
            let working_copy = working_copy.clone();
            let changes = changes.clone();
            let channel = channel.clone();
            let work = work.clone();
            let txn = txn.clone();
            let sep: regex::bytes::Regex = diff_separator.clone();
            let cl = move || {
                loop {
                    let (w, stop) = {
                        let mut work = work.lock();
                        (work.t.pop_front(), work.stop)
                    };
                    if let Some((item, vertex, rec, new_papa)) = w {
                        // This parent has changed.
                        info!("record existing file {:?} on thread {:?}", item, t);
                        rec.lock().record_existing_file(
                            &txn,
                            diff_algorithm,
                            stop_early,
                            &sep,
                            &channel,
                            working_copy.clone(),
                            &changes,
                            &item,
                            new_papa,
                            vertex,
                        )?;
                    } else if stop {
                        info!("stop {:?}", t);
                        break;
                    } else {
                        info!("yield {:?}", t);
                        std::thread::park_timeout(std::time::Duration::from_secs(1));
                    }
                }
                Ok::<_, RecordError<C::Error, W::Error, T>>(())
            };
            workers.push(std::thread::spawn(cl.clone()))
        }
        info!("Starting to record");
        let now = std::time::Instant::now();
        let mut stack = vec![(RecordItem::root(), components(prefix))];
        while let Some((mut item, mut components)) = stack.pop() {
            debug!("stack.pop() = Some({:?})", item);

            // Check for moves and file conflicts.
            let vertex: Option<Position<Option<ChangeId>>> =
                self.recorded_inodes.lock().get(&item.inode).cloned();

            let mut root_vertices = Vec::new();

            let vertex = if let Some(vertex) = vertex {
                vertex
            } else if item.inode == Inode::ROOT {
                debug!("TAKING LOCK {}", line!());
                let txn = txn.read();
                debug!("TAKEN");
                let channel = channel.r.read();

                // Test for a "root" vertex below the null one.
                let f0 = EdgeFlags::FOLDER | EdgeFlags::BLOCK;
                let f1 = f0 | EdgeFlags::PSEUDO;
                self.recorded_inodes
                    .lock()
                    .insert(Inode::ROOT, Position::ROOT.to_option());
                let mut has_nonempty_root = false;
                for e in iter_adjacent(&*txn, txn.graph(&*channel), Vertex::ROOT, f0, f1)? {
                    let e = e?;
                    let child = txn.find_block(txn.graph(&*channel), e.dest()).unwrap();
                    if child.start == child.end {
                        // This is the "new" format, with multiple
                        // roots, and `grandchild` is one of the
                        // roots.
                        let grandchild =
                            iter_adjacent(&*txn, txn.graph(&*channel), *child, f0, f1)?
                                .next()
                                .unwrap()?
                                .dest();
                        root_vertices.push(grandchild);
                        self.delete_obsolete_children(
                            &*txn,
                            txn.graph(&channel),
                            working_copy,
                            changes,
                            &item.full_path,
                            grandchild,
                        )?;
                    } else {
                        // Single-root repository, we need to follow
                        // the root's children.
                        let mut name = vec![0; child.end - child.start];
                        changes
                            .get_contents(
                                |p| txn.get_external(&p).unwrap().map(From::from),
                                *child,
                                &mut name,
                            )
                            .map_err(RecordError::Changestore)?;
                        debug!("non-empty root {:?} {:?}", child, name);
                        has_nonempty_root = true
                    }
                }
                debug!("has_nonempty_root: {:?}", has_nonempty_root);
                debug!("root_vertices: {:?}", root_vertices);
                if has_nonempty_root && !root_vertices.is_empty() {
                    // This repository is mixed between "zero" roots,
                    // and new-style-roots.
                    root_vertices.push(Position::ROOT)
                }
                Position::ROOT.to_option()
            } else if let Some(vertex) = get_inodes_::<_, C, W>(&txn, &channel, &item.inode)? {
                {
                    let txn = txn.read();
                    let channel = channel.r.read();
                    let graph = txn.graph(&*channel);
                    self.delete_obsolete_children(
                        &*txn,
                        &graph,
                        working_copy,
                        changes,
                        &item.full_path,
                        vertex,
                    )?;
                }

                let rec = self.recorded();
                let new_papa = {
                    let mut recorded = self.recorded_inodes.lock();
                    recorded.insert(item.inode, vertex.to_option());
                    recorded.get(&item.papa).cloned()
                };
                let mut work = work.lock();
                work.t.push_back((item.clone(), vertex, rec, new_papa));
                std::mem::drop(work);
                for t in workers.iter() {
                    t.thread().unpark()
                }

                vertex.to_option()
            } else {
                let rec = self.recorded();
                debug!("TAKING LOCK {}", line!());
                let mut rec = rec.lock();
                match rec.add_file(working_copy, item.clone()) {
                    Ok(Some(vertex)) => {
                        // Path addition (maybe just a single directory).
                        self.recorded_inodes.lock().insert(item.inode, vertex);
                        vertex
                    }
                    _ => continue,
                }
            };

            if root_vertices.is_empty() {
                // Move on to the next step.
                debug!("TAKING LOCK {}", line!());
                let txn = txn.read();
                let channel = channel.r.read();
                self.push_children::<_, _, C>(
                    &*txn,
                    &*channel,
                    working_copy,
                    &mut item,
                    &mut components,
                    vertex,
                    &mut stack,
                    prefix,
                    changes,
                )?;
            } else {
                for vertex in root_vertices {
                    let txn = txn.read();
                    let channel = channel.r.read();
                    if !vertex.change.is_root() {
                        let mut r = self.new_root.lock();
                        let age = txn
                            .get_changeset(txn.changes(&*channel), &vertex.change)?
                            .unwrap();
                        if let Some((_, a)) = *r {
                            if a < (*age).into() {
                                *r = Some((vertex.to_option(), (*age).into()))
                            }
                        } else {
                            *r = Some((vertex.to_option(), (*age).into()))
                        }
                    }
                    item.v_papa = vertex.to_option();
                    self.push_children::<_, _, C>(
                        &*txn,
                        &*channel,
                        working_copy,
                        &mut item,
                        &mut components,
                        vertex.to_option(),
                        &mut stack,
                        prefix,
                        changes,
                    )?;
                }
            }
        }

        info!("stop work");
        work.lock().stop = true;
        for t in workers.iter() {
            t.thread().unpark()
        }
        loop {
            let w = {
                let mut work = work.lock();
                debug!("waiting, stop = {:?}", work.stop);
                work.t.pop_front()
            };
            if let Some((item, vertex, rec, new_papa)) = w {
                // This parent has changed.
                info!("record existing file {:?}", item);
                rec.lock().record_existing_file(
                    &txn,
                    diff_algorithm,
                    stop_early,
                    diff_separator,
                    &channel,
                    working_copy.clone(),
                    changes,
                    &item,
                    new_papa,
                    vertex,
                )?;
            } else {
                break;
            }
        }
        for (n, t) in workers.into_iter().enumerate() {
            debug!("WAITING {:?}", n);
            match t.join() {
                Ok(x) => x?,
                Err(e) => {
                    warn!("Thread error {:?}", e);
                }
            }
        }
        crate::TIMERS.lock().unwrap().record += now.elapsed();

        txn.write().touch_channel(&mut channel.write(), None);
        info!("record done");
        Ok(())
    }

    pub fn record_single_thread<T, W: WorkingCopyRead + Clone, C: ChangeStore + Clone>(
        &mut self,
        txn: ArcTxn<T>,
        diff_algorithm: diff::Algorithm,
        stop_early: bool,
        diff_separator: &regex::bytes::Regex,
        channel: ChannelRef<T>,
        working_copy: &W,
        changes: &C,
        prefix: &str,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        T: ChannelMutTxnT + TreeTxnT,
        <W as WorkingCopyRead>::Error: 'static,
    {
        info!("Starting to record");
        let now = std::time::Instant::now();
        let mut stack = vec![(RecordItem::root(), components(prefix))];
        while let Some((mut item, mut components)) = stack.pop() {
            debug!("stack.pop() = Some({:?})", item);

            // Check for moves and file conflicts.
            let vertex: Option<Position<Option<ChangeId>>> =
                self.recorded_inodes.lock().get(&item.inode).cloned();

            let mut root_vertices = Vec::new();

            let vertex = if let Some(vertex) = vertex {
                vertex
            } else if item.inode == Inode::ROOT {
                debug!("TAKING LOCK {}", line!());
                let txn = txn.read();
                debug!("TAKEN");
                let channel = channel.r.read();

                // Test for a "root" vertex below the null one.
                let f0 = EdgeFlags::FOLDER | EdgeFlags::BLOCK;
                let f1 = f0 | EdgeFlags::PSEUDO;
                self.recorded_inodes
                    .lock()
                    .insert(Inode::ROOT, Position::ROOT.to_option());
                let mut has_nonempty_root = false;
                for e in iter_adjacent(&*txn, txn.graph(&*channel), Vertex::ROOT, f0, f1)? {
                    let e = e?;
                    let child = txn.find_block(txn.graph(&*channel), e.dest()).unwrap();
                    if child.start == child.end {
                        // This is the "new" format, with multiple
                        // roots, and `grandchild` is one of the
                        // roots.
                        let grandchild =
                            iter_adjacent(&*txn, txn.graph(&*channel), *child, f0, f1)?
                                .next()
                                .unwrap()?
                                .dest();
                        root_vertices.push(grandchild);
                        self.delete_obsolete_children(
                            &*txn,
                            txn.graph(&channel),
                            working_copy,
                            changes,
                            &item.full_path,
                            grandchild,
                        )?;
                    } else {
                        // Single-root repository, we need to follow
                        // the root's children.
                        let mut name = vec![0; child.end - child.start];
                        changes
                            .get_contents(
                                |p| txn.get_external(&p).unwrap().map(From::from),
                                *child,
                                &mut name,
                            )
                            .map_err(RecordError::Changestore)?;
                        debug!("non-empty root {:?} {:?}", child, name);
                        has_nonempty_root = true
                    }
                }
                debug!("has_nonempty_root: {:?}", has_nonempty_root);
                debug!("root_vertices: {:?}", root_vertices);
                if has_nonempty_root && !root_vertices.is_empty() {
                    // This repository is mixed between "zero" roots,
                    // and new-style-roots.
                    root_vertices.push(Position::ROOT)
                }
                Position::ROOT.to_option()
            } else if let Some(vertex) = get_inodes_::<_, C, W>(&txn, &channel, &item.inode)? {
                {
                    let txn = txn.read();
                    let channel = channel.r.read();
                    let graph = txn.graph(&*channel);
                    self.delete_obsolete_children(
                        &*txn,
                        &graph,
                        working_copy,
                        changes,
                        &item.full_path,
                        vertex,
                    )?;
                }

                let rec = self.recorded();
                let new_papa = {
                    let mut recorded = self.recorded_inodes.lock();
                    recorded.insert(item.inode, vertex.to_option());
                    recorded.get(&item.papa).cloned()
                };

                rec.lock().record_existing_file(
                    &txn,
                    diff_algorithm,
                    stop_early,
                    &diff_separator,
                    &channel,
                    working_copy.clone(),
                    changes,
                    &item,
                    new_papa,
                    vertex,
                )?;

                vertex.to_option()
            } else {
                let rec = self.recorded();
                debug!("TAKING LOCK {}", line!());
                let mut rec = rec.lock();
                match rec.add_file(working_copy, item.clone()) {
                    Ok(Some(vertex)) => {
                        // Path addition (maybe just a single directory).
                        self.recorded_inodes.lock().insert(item.inode, vertex);
                        vertex
                    }
                    _ => continue,
                }
            };

            if root_vertices.is_empty() {
                // Move on to the next step.
                debug!("TAKING LOCK {}", line!());
                let txn = txn.read();
                let channel = channel.r.read();
                self.push_children::<_, _, C>(
                    &*txn,
                    &*channel,
                    working_copy,
                    &mut item,
                    &mut components,
                    vertex,
                    &mut stack,
                    prefix,
                    changes,
                )?;
            } else {
                for vertex in root_vertices {
                    let txn = txn.read();
                    let channel = channel.r.read();
                    if !vertex.change.is_root() {
                        let mut r = self.new_root.lock();
                        let age = txn
                            .get_changeset(txn.changes(&*channel), &vertex.change)?
                            .unwrap();
                        if let Some((_, a)) = *r {
                            if a < (*age).into() {
                                *r = Some((vertex.to_option(), (*age).into()))
                            }
                        } else {
                            *r = Some((vertex.to_option(), (*age).into()))
                        }
                    }
                    item.v_papa = vertex.to_option();
                    self.push_children::<_, _, C>(
                        &*txn,
                        &*channel,
                        working_copy,
                        &mut item,
                        &mut components,
                        vertex.to_option(),
                        &mut stack,
                        prefix,
                        changes,
                    )?;
                }
            }
        }
        crate::TIMERS.lock().unwrap().record += now.elapsed();
        info!("record done");
        Ok(())
    }

    fn delete_obsolete_children<T: GraphTxnT + TreeTxnT, W: WorkingCopyRead, C: ChangeStore>(
        &mut self,
        txn: &T,
        channel: &T::Graph,
        working_copy: &W,
        changes: &C,
        full_path: &str,
        v: Position<ChangeId>,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as WorkingCopyRead>::Error: 'static,
    {
        if self.ignore_missing {
            return Ok(());
        }
        let f0 = EdgeFlags::FOLDER | EdgeFlags::BLOCK;
        let f1 = f0 | EdgeFlags::PSEUDO;
        debug!("delete_obsolete_children, v = {:?}", v);
        for child in iter_adjacent(txn, channel, v.inode_vertex(), f0, f1)? {
            let child = child?;
            let child = txn.find_block(channel, child.dest()).unwrap();
            if child.start == child.end {
                // This is an empty name, i.e. the grandchild is a root vertex.
                continue;
            }
            for grandchild in iter_adjacent(txn, channel, *child, f0, f1)? {
                let grandchild = grandchild?;
                debug!("grandchild {:?}", grandchild);
                let needs_deletion =
                    if let Some(inode) = txn.get_revinodes(&grandchild.dest(), None)? {
                        debug!("inode = {:?} {:?}", inode, txn.get_revtree(inode, None));
                        if let Some(path) = crate::fs::inode_filename(txn, *inode)? {
                            working_copy.file_metadata(&path).is_err()
                        } else {
                            true
                        }
                    } else {
                        true
                    };
                if needs_deletion {
                    let mut name = vec![0; child.end - child.start];
                    changes
                        .get_contents(
                            |p| txn.get_external(&p).unwrap().map(From::from),
                            *child,
                            &mut name,
                        )
                        .map_err(RecordError::Changestore)?;
                    let mut full_path = full_path.to_string();
                    let meta = FileMetadata::read(&name);
                    if !full_path.is_empty() {
                        full_path.push('/');
                    }
                    full_path.push_str(meta.basename);
                    // delete recursively.
                    let rec = self.recorded();
                    let mut rec = rec.lock();
                    rec.record_deleted_file(
                        txn,
                        &channel,
                        working_copy,
                        &full_path,
                        grandchild.dest(),
                        changes,
                    )?
                }
            }
        }
        Ok(())
    }

    fn push_children<'a, T: ChannelTxnT + TreeTxnT, W: WorkingCopyRead, C: ChangeStore>(
        &mut self,
        txn: &T,
        channel: &T::Channel,
        working_copy: &W,
        item: &mut RecordItem,
        components: &mut Components<'a>,
        vertex: Position<Option<ChangeId>>,
        stack: &mut Vec<(RecordItem, Components<'a>)>,
        prefix: &str,
        changes: &C,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as crate::working_copy::WorkingCopyRead>::Error: 'static,
    {
        debug!("push_children, vertex = {:?}, item = {:?}", vertex, item);
        let comp = components.next();
        let full_path = item.full_path.clone();
        let fileid = OwnedPathId {
            parent_inode: item.inode,
            basename: SmallString::new(),
        };
        debug!("fileid = {:?}", fileid);
        let mut has_matching_children = false;
        for x in txn.iter_tree(&fileid, None)? {
            let (fileid_, child_inode) = x?;
            debug!("push_children {:?} {:?}", fileid_, child_inode);
            assert!(fileid_.parent_inode >= fileid.parent_inode);
            if fileid_.basename.is_empty() {
                continue;
            } else if fileid_.parent_inode > fileid.parent_inode {
                break;
            }
            if let Some(comp) = comp {
                if comp != fileid_.basename.as_str() {
                    continue;
                }
            }
            has_matching_children = true;
            let basename = fileid_.basename.as_str().to_string();
            let full_path = if full_path.is_empty() {
                basename.clone()
            } else {
                full_path.clone() + "/" + &basename
            };
            debug!("fileid_ {:?} child_inode {:?}", fileid_, child_inode);
            match working_copy.file_metadata(&full_path) {
                Ok(meta) => {
                    debug!("full_path = {:?}, meta = {:?}", full_path, meta);
                    stack.push((
                        RecordItem {
                            papa: item.inode,
                            inode: *child_inode,
                            v_papa: vertex,
                            basename,
                            full_path,
                            metadata: meta,
                        },
                        components.clone(),
                    ));
                }
                _ => {
                    if let Some(vertex) = get_inodes::<_, C, W>(txn, &channel, child_inode)? {
                        let rec = self.recorded();
                        let mut rec = rec.lock();
                        rec.record_deleted_file(
                            txn,
                            txn.graph(channel),
                            working_copy,
                            &full_path,
                            *vertex,
                            changes,
                        )?
                    }
                }
            }
        }
        if comp.is_some() && !has_matching_children {
            debug!("comp = {:?}", comp);
            return Err(RecordError::PathNotInRepo(prefix.to_string()));
        }
        debug!("push_children done");
        Ok(())
    }
}

fn modified_since_last_commit<T: ChannelTxnT, W: WorkingCopyRead>(
    txn: &T,
    channel: &T::Channel,
    working_copy: &W,
    prefix: &str,
) -> Result<bool, std::time::SystemTimeError> {
    match working_copy.modified_time(prefix) {
        Ok(last_modified) => {
            debug!(
                "last_modified = {:?}, channel.last = {:?}",
                last_modified
                    .duration_since(std::time::UNIX_EPOCH)?
                    .as_millis(),
                txn.last_modified(channel),
            );
            // Account for low-resolution filesystems, by truncating the
            // channel modification time if the file modification time is
            // a multiple of 1000.
            let last_mod = last_modified
                .duration_since(std::time::UNIX_EPOCH)?
                .as_millis() as u64;
            let channel_mod = (txn.last_modified(channel) / 1000) * 1000;

            debug!("recording = {:?}", last_mod >= channel_mod);
            Ok(last_mod >= channel_mod)
        }
        _ => Ok(true),
    }
}

impl Recorded {
    fn add_root_if_needed(
        &mut self,
        v_papa: Position<Option<ChangeId>>,
    ) -> Position<Option<ChangeId>> {
        let mut contents = self.contents.lock();
        if v_papa.change == Some(ChangeId::ROOT) {
            let mut new_root = self.new_root.lock();
            if let Some((pos, _)) = *new_root {
                pos
            } else {
                contents.push(0);
                let pos = ChangePosition(contents.len().into());
                contents.push(0);
                let pos2 = ChangePosition(contents.len().into());
                contents.push(0);
                debug!(
                    "add root if needed {:?} {:?}",
                    pos.0.as_u64(),
                    pos2.0.as_u64()
                );
                self.actions.push(Hunk::AddRoot {
                    name: Atom::NewVertex(NewVertex {
                        up_context: vec![v_papa],
                        down_context: vec![],
                        start: pos,
                        end: pos,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                        inode: v_papa,
                    }),
                    inode: Atom::NewVertex(NewVertex {
                        up_context: vec![Position { change: None, pos }],
                        down_context: vec![],
                        start: pos2,
                        end: pos2,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                        inode: v_papa,
                    }),
                });

                self.updatables.insert(
                    self.actions.len(),
                    InodeUpdate::Add {
                        inode: Inode::ROOT,
                        pos: pos2,
                    },
                );

                *new_root = Some((
                    Position {
                        change: None,
                        pos: pos2,
                    },
                    u64::MAX,
                ));
                Position {
                    change: None,
                    pos: pos2,
                }
            }
        } else {
            v_papa
        }
    }

    fn add_file<W: WorkingCopyRead>(
        &mut self,
        working_copy: &W,
        item: RecordItem,
    ) -> Result<Option<Position<Option<ChangeId>>>, W::Error> {
        debug!("record_file_addition {:?}", item);
        let meta = working_copy.file_metadata(&item.full_path)?;

        // If we're inserting at the root, add an extra "root
        // directory" empty vertex.
        let item_v_papa = self.add_root_if_needed(item.v_papa);

        let mut contents = self.contents.lock();
        contents.push(0);
        let inode_pos = ChangePosition(contents.len().into());
        contents.push(0);
        let (contents_, encoding) = if meta.is_file() {
            let start = ChangePosition(contents.len().into());
            let encoding = working_copy.decode_file(&item.full_path, &mut contents)?;
            self.has_binary_files |= encoding.is_none();
            let end = ChangePosition(contents.len().into());
            self.largest_file = self.largest_file.max(end.0.as_u64() - start.0.as_u64());
            contents.push(0);
            if end > start {
                (
                    Some(Atom::NewVertex(NewVertex {
                        up_context: vec![Position {
                            change: None,
                            pos: inode_pos,
                        }],
                        down_context: vec![],
                        start,
                        end,
                        flag: EdgeFlags::BLOCK,
                        inode: Position {
                            change: None,
                            pos: inode_pos,
                        },
                    })),
                    encoding,
                )
            } else {
                (None, encoding)
            }
        } else {
            (None, None)
        };

        let name_start = ChangePosition(contents.len().into());
        let file_meta = FileMetadata {
            metadata: meta,
            basename: item.basename.as_str(),
            encoding: encoding.clone(),
        };
        file_meta.write(&mut contents);
        let name_end = ChangePosition(contents.len().into());
        debug!("name start {:?} end {:?}", name_start, name_end);
        contents.push(0);
        self.actions.push(Hunk::FileAdd {
            add_name: Atom::NewVertex(NewVertex {
                up_context: vec![item_v_papa],
                down_context: vec![],
                start: name_start,
                end: name_end,
                flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                inode: item.v_papa,
            }),
            add_inode: Atom::NewVertex(NewVertex {
                up_context: vec![Position {
                    change: None,
                    pos: name_end,
                }],
                down_context: vec![],
                start: inode_pos,
                end: inode_pos,
                flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                inode: item.v_papa,
            }),
            contents: contents_,
            path: item.full_path.clone(),
            encoding,
        });
        debug!("{:?}", self.actions.last().unwrap());
        self.updatables.insert(
            self.actions.len(),
            InodeUpdate::Add {
                inode: item.inode,
                pos: inode_pos,
            },
        );
        if meta.is_dir() {
            Ok(Some(Position {
                change: None,
                pos: inode_pos,
            }))
        } else {
            Ok(None)
        }
    }

    fn record_existing_file<T: ChannelTxnT + TreeTxnT, W: WorkingCopyRead + Clone, C: ChangeStore>(
        &mut self,
        txn: &ArcTxn<T>,
        diff_algorithm: diff::Algorithm,
        stop_early: bool,
        diff_sep: &regex::bytes::Regex,
        channel: &ChannelRef<T>,
        working_copy: W,
        changes: &C,
        item: &RecordItem,
        new_papa: Option<Position<Option<ChangeId>>>,
        vertex: Position<ChangeId>,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as crate::working_copy::WorkingCopyRead>::Error: 'static,
    {
        debug!(
            "record_existing_file {:?}: {:?} {:?} {:?}",
            item.full_path, item.inode, vertex, new_papa,
        );
        // Former parent(s) of vertex
        let (former_parents, is_deleted, encoding) = {
            let txn_ = txn.read();
            let channel_ = channel.read();
            collect_former_parents::<C, W, T>(changes, &*txn_, &*channel_, vertex)?
        };
        debug!(
            "record_existing_file: {:?} {:?} {:?}",
            item, former_parents, is_deleted,
        );
        match working_copy.file_metadata(&item.full_path) {
            Ok(new_meta) => self.record_nondeleted(
                txn,
                diff_algorithm,
                stop_early,
                diff_sep,
                channel,
                working_copy,
                changes,
                item,
                new_papa,
                vertex,
                new_meta,
                &former_parents,
                is_deleted,
                encoding,
            )?,
            _ => {
                debug!("calling record_deleted_file on {:?}", item.full_path);
                let txn_ = txn.read();
                let channel_ = channel.read();
                self.record_deleted_file(
                    &*txn_,
                    txn_.graph(&*channel_),
                    &working_copy,
                    &item.full_path,
                    vertex,
                    changes,
                )?
            }
        }
        Ok(())
    }

    fn record_nondeleted<T: ChannelTxnT + TreeTxnT, W: WorkingCopyRead + Clone, C: ChangeStore>(
        &mut self,
        txn: &ArcTxn<T>,
        diff_algorithm: diff::Algorithm,
        stop_early: bool,
        diff_sep: &regex::bytes::Regex,
        channel: &ChannelRef<T>,
        working_copy: W,
        changes: &C,
        item: &RecordItem,
        new_papa: Option<Position<Option<ChangeId>>>,
        vertex: Position<ChangeId>,
        new_meta: InodeMetadata,
        former_parents: &[Parent],
        is_deleted: bool,
        encoding: Option<Encoding>,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as crate::working_copy::WorkingCopyRead>::Error: 'static,
    {
        if former_parents.is_empty() {
            // This is the case where the inode exists both in the
            // graph and in the inode tables, but isn't alive in the
            // graph.
            //
            // This can happen (1) when outputting a tag that has this
            // file, after recording the deletion of the file, or (2)
            // when recording after applying, but before outputting,
            // but this is a misuse of the library.
            debug!("new_papa = {:?}", new_papa);
            let txn = txn.read();
            let channel = channel.read();
            self.record_moved_file::<_, _, W>(
                changes,
                &*txn,
                &*channel,
                &item,
                vertex,
                new_papa.unwrap(),
                encoding,
            )?
        } else if former_parents.len() > 1
            || former_parents[0].basename != item.basename
            || former_parents[0].metadata != item.metadata
            || former_parents[0].parent != item.v_papa
            || is_deleted
        {
            debug!("new_papa = {:?}", new_papa);
            let txn = txn.read();
            let channel = channel.read();
            self.record_moved_file::<_, _, W>(
                changes,
                &*txn,
                &*channel,
                &item,
                vertex,
                new_papa.unwrap(),
                former_parents[0].encoding.clone(),
            )?
        }
        if new_meta.is_file()
            && (self.force_rediff
                || modified_since_last_commit(
                    &*txn.read(),
                    &*channel.read(),
                    &working_copy,
                    &item.full_path,
                )?)
        {
            let mut ret = {
                let txn = txn.read();
                let channel = channel.read();
                retrieve(&*txn, txn.graph(&*channel), vertex, false)?
            };
            let mut b = Vec::new();
            let encoding = working_copy
                .decode_file(&item.full_path, &mut b)
                .map_err(RecordError::WorkingCopy)?;
            debug!("diffing…");
            let len = self.actions.len();
            self.diff(
                changes,
                txn,
                channel,
                diff_algorithm,
                stop_early,
                item.full_path.clone(),
                item.inode,
                vertex.to_option(),
                &mut ret,
                &b,
                &encoding,
                diff_sep,
            )?;
            if self.actions.len() > len {
                if let Ok(last_modified) = working_copy.modified_time(&item.full_path) {
                    if self.oldest_change == std::time::SystemTime::UNIX_EPOCH {
                        self.oldest_change = last_modified;
                    } else {
                        self.oldest_change = self.oldest_change.min(last_modified);
                    }
                }
            }
            debug!(
                "new actions: {:?}, total {:?}",
                &self.actions.len() - len,
                self.actions.len()
            );
        }
        Ok(())
    }

    fn record_moved_file<T: ChannelTxnT + TreeTxnT, C: ChangeStore, W: WorkingCopyRead>(
        &mut self,
        changes: &C,
        txn: &T,
        channel: &T::Channel,
        item: &RecordItem,
        vertex: Position<ChangeId>,
        new_papa: Position<Option<ChangeId>>,
        encoding: Option<Encoding>,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as crate::working_copy::WorkingCopyRead>::Error: 'static,
    {
        debug!("record_moved_file {:?} {:?}", item, vertex);
        let basename = item.basename.as_str();
        let mut moved = collect_moved_edges::<_, _, W>(
            txn,
            changes,
            txn.graph(channel),
            new_papa,
            vertex,
            item.metadata,
            basename,
        )?;
        debug!("moved = {:#?}", moved);
        let is_resurrected = !moved.resurrect.is_empty();
        if is_resurrected {
            moved.resurrect.extend(moved.alive.drain(..));
            if !moved.need_new_name {
                moved.resurrect.extend(moved.edges.drain(..));
            }
            self.actions.push(Hunk::FileUndel {
                undel: Atom::EdgeMap(EdgeMap {
                    edges: moved.resurrect,
                    inode: item.v_papa,
                }),
                contents: None,
                path: item.full_path.clone(),
                encoding: encoding.clone(),
            });
        }

        let item_v_papa = if !moved.edges.is_empty() && moved.need_new_name {
            self.add_root_if_needed(item.v_papa)
        } else {
            item.v_papa
        };

        let mut contents = self.contents.lock();
        contents.push(0);
        let meta_start = ChangePosition(contents.len().into());
        FileMetadata {
            metadata: item.metadata,
            basename,
            encoding: encoding.clone(),
        }
        .write(&mut contents);
        let meta_end = ChangePosition(contents.len().into());
        contents.push(0);
        if !moved.edges.is_empty() {
            // If there was exactly one alive name, this is a regular
            // move, i.e. not a conflict.
            if moved.n_alive_names == 1 || (moved.need_new_name && !is_resurrected) {
                debug!("need_new_name {:?}", item.v_papa);
                let add = if moved.need_new_name && !is_resurrected {
                    moved.edges.extend(moved.alive.drain(..));
                    Atom::NewVertex(NewVertex {
                        up_context: vec![item_v_papa],
                        down_context: vec![vertex.to_option()],
                        start: meta_start,
                        end: meta_end,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                        inode: item_v_papa,
                    })
                } else {
                    Atom::EdgeMap(EdgeMap {
                        edges: moved.alive,
                        inode: item_v_papa,
                    })
                };
                self.actions.push(Hunk::FileMove {
                    del: Atom::EdgeMap(EdgeMap {
                        edges: moved.edges,
                        inode: item.v_papa,
                    }),
                    add,
                    path: crate::fs::find_path(changes, txn, channel, true, vertex)?
                        .unwrap()
                        .0
                        .join("/"),
                });
            } else {
                self.actions.push(Hunk::SolveNameConflict {
                    name: Atom::EdgeMap(EdgeMap {
                        edges: moved.edges,
                        inode: item.v_papa,
                    }),
                    path: item.full_path.clone(),
                });
                contents.truncate(meta_start.0.as_usize())
            }
        } else {
            contents.truncate(meta_start.0.as_usize())
        }
        Ok(())
    }

    pub fn take_updatables(&mut self) -> HashMap<usize, InodeUpdate> {
        std::mem::replace(&mut self.updatables, HashMap::default())
    }
    pub fn into_change<T: ChannelTxnT + DepsTxnT<DepsError = <T as GraphTxnT>::GraphError>>(
        self,
        txn: &T,
        channel: &ChannelRef<T>,
        header: crate::change::ChangeHeader,
    ) -> Result<
        crate::change::LocalChange<
            crate::change::Hunk<Option<Hash>, crate::change::Local>,
            crate::change::Author,
        >,
        crate::change::MakeChangeError<T>,
    > {
        let actions = self
            .actions
            .into_iter()
            .map(|rec| rec.globalize(txn).unwrap())
            .collect();
        let contents = if let Ok(c) = Arc::try_unwrap(self.contents) {
            c.into_inner()
        } else {
            unreachable!()
        };
        Ok(crate::change::LocalChange::make_change(
            txn,
            &channel,
            actions,
            contents,
            header,
            Vec::new(),
        )?)
    }
}

fn collect_former_parents<C: ChangeStore, W: WorkingCopyRead, T: ChannelTxnT + TreeTxnT>(
    changes: &C,
    txn: &T,
    channel: &T::Channel,
    vertex: Position<ChangeId>,
) -> Result<(Vec<Parent>, bool, Option<Encoding>), RecordError<C::Error, W::Error, T>>
where
    W::Error: 'static,
{
    let mut former_parents = Vec::new();
    let f0 = EdgeFlags::FOLDER | EdgeFlags::PARENT;
    let f1 = EdgeFlags::all();
    let mut is_deleted = true;
    let mut encoding_ = None;
    for name_ in iter_adjacent(txn, txn.graph(channel), vertex.inode_vertex(), f0, f1)? {
        debug!("name_ = {:?}", name_);
        let name_ = name_?;
        if !name_.flag().contains(EdgeFlags::PARENT) {
            debug!("continue");
            continue;
        }

        let name_dest = txn
            .find_block_end(txn.graph(channel), name_.dest())
            .unwrap();
        let mut meta = vec![0; name_dest.end - name_dest.start];
        let FileMetadata {
            basename,
            metadata,
            encoding,
        } = changes
            .get_file_meta(
                |p| txn.get_external(&p).unwrap().map(From::from),
                *name_dest,
                &mut meta,
            )
            .map_err(RecordError::Changestore)?;
        debug!(
            "former basename of {:?}: {:?} {:?}",
            vertex, basename, metadata
        );

        if name_.flag().contains(EdgeFlags::DELETED) {
            debug!("is_deleted {:?}", name_);
            is_deleted = true;
            if encoding_.is_none() {
                encoding_ = encoding
            }
            break;
        }
        if let Some(v_papa) = iter_adjacent(txn, txn.graph(channel), *name_dest, f0, f1)?.next() {
            let v_papa = v_papa?;
            if !v_papa.flag().contains(EdgeFlags::DELETED) {
                if encoding_.is_none() {
                    encoding_ = encoding.clone()
                }
                former_parents.push(Parent {
                    basename: basename.to_string(),
                    metadata,
                    encoding,
                    parent: v_papa.dest().to_option(),
                })
            }
        }
    }
    Ok((former_parents, is_deleted, encoding_))
}

#[derive(Debug)]
struct MovedEdges {
    edges: Vec<NewEdge<Option<ChangeId>>>,
    alive: Vec<NewEdge<Option<ChangeId>>>,
    resurrect: Vec<NewEdge<Option<ChangeId>>>,
    need_new_name: bool,
    n_alive_names: usize,
}

fn collect_moved_edges<T: GraphTxnT + TreeTxnT, C: ChangeStore, W: WorkingCopyRead>(
    txn: &T,
    changes: &C,
    channel: &T::Graph,
    parent_pos: Position<Option<ChangeId>>,
    current_pos: Position<ChangeId>,
    new_meta: InodeMetadata,
    name: &str,
) -> Result<MovedEdges, RecordError<C::Error, W::Error, T>>
where
    <W as crate::working_copy::WorkingCopyRead>::Error: 'static,
{
    debug!("collect_moved_edges {:?}", current_pos);
    let mut moved = MovedEdges {
        edges: Vec::new(),
        alive: Vec::new(),
        resurrect: Vec::new(),
        need_new_name: true,
        n_alive_names: 0,
    };
    let mut del_del = HashMap::default();
    let mut alive = HashMap::default();
    let mut previous_name = Vec::new();
    let mut last_alive_meta = None;
    let mut is_first_parent = true;
    for parent in iter_adjacent(
        txn,
        channel,
        current_pos.inode_vertex(),
        EdgeFlags::FOLDER | EdgeFlags::PARENT,
        EdgeFlags::all(),
    )? {
        let parent = parent?;
        if !parent
            .flag()
            .contains(EdgeFlags::FOLDER | EdgeFlags::PARENT)
        {
            continue;
        }
        debug!("parent = {:?}", parent);
        let mut parent_was_resurrected = false;
        if !parent.flag().contains(EdgeFlags::PSEUDO) {
            if parent.flag().contains(EdgeFlags::DELETED) {
                debug!("resurrecting parent");
                moved.resurrect.push(NewEdge {
                    previous: parent.flag() - EdgeFlags::PARENT,
                    flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                    from: parent.dest().to_option(),
                    to: current_pos.inode_vertex().to_option(),
                    introduced_by: Some(parent.introduced_by()),
                });
                parent_was_resurrected = true;
                let v = alive
                    .entry((parent.dest(), current_pos.inode_vertex()))
                    .or_insert_with(HashSet::new);
                v.insert(None);
            } else {
                let v = alive
                    .entry((parent.dest(), current_pos.inode_vertex()))
                    .or_insert_with(HashSet::new);
                v.insert(Some(parent.introduced_by()));
            }
        }
        debug!("parent_was_resurrected: {:?}", parent_was_resurrected);
        let parent_dest = txn.find_block_end(channel, parent.dest()).unwrap();
        previous_name.resize(parent_dest.end - parent_dest.start, 0);
        let FileMetadata {
            metadata: parent_meta,
            basename: parent_name,
            ..
        } = changes
            .get_file_meta(
                |p| txn.get_external(&p).unwrap().map(From::from),
                *parent_dest,
                &mut previous_name,
            )
            .map_err(RecordError::Changestore)?;
        debug!(
            "parent_dest {:?} {:?} {:?} {:?}",
            parent_dest, parent_meta, parent_name, name
        );
        let name_changed = parent_name != name;
        let mut meta_changed = new_meta != parent_meta;
        if cfg!(windows) && !meta_changed {
            if let Some(m) = last_alive_meta {
                meta_changed = new_meta != m
            }
        }
        let mut name_is_alive = false;
        for grandparent in iter_adjacent(
            txn,
            channel,
            *parent_dest,
            EdgeFlags::FOLDER | EdgeFlags::PARENT,
            EdgeFlags::all(),
        )? {
            let grandparent = grandparent?;
            if !grandparent
                .flag()
                .contains(EdgeFlags::FOLDER | EdgeFlags::PARENT)
                || grandparent.flag().contains(EdgeFlags::PSEUDO)
            {
                continue;
            }
            debug!("grandparent: {:?}", grandparent);
            let grandparent_dest = txn.find_block_end(channel, grandparent.dest()).unwrap();
            assert_eq!(grandparent_dest.start, grandparent_dest.end);
            debug!(
                "grandparent_dest {:?} {:?}, parent_pos = {:?}",
                grandparent_dest,
                std::str::from_utf8(&previous_name[2..]),
                parent_pos,
            );
            let grandparent_changed = if parent_pos.change == Some(ChangeId::ROOT) {
                // Because repos may have multiple roots there may be
                // a mismatch here.  The "no change" case when
                // `parent_pos` is a root vertex is when
                // `grandparent.dest()` is also a root vertex.
                !is_root_vertex(txn, channel, grandparent.dest())?
            } else {
                parent_pos != grandparent.dest().to_option()
            };
            debug!(
                "change = {:?} {:?} {:?}",
                grandparent_changed, name_changed, meta_changed
            );
            if !grandparent.flag().contains(EdgeFlags::DELETED) {
                name_is_alive = true
            }
            if grandparent.flag().contains(EdgeFlags::DELETED) {
                if !grandparent_changed && !name_changed && !meta_changed {
                    // We resurrect the name
                    (if parent_was_resurrected {
                        &mut moved.resurrect
                    } else {
                        &mut moved.alive
                    })
                    .push(NewEdge {
                        previous: grandparent.flag() - EdgeFlags::PARENT,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                        from: grandparent.dest().to_option(),
                        to: parent_dest.to_option(),
                        introduced_by: Some(grandparent.introduced_by()),
                    });
                    if !parent_was_resurrected && !parent.flag().contains(EdgeFlags::PSEUDO) {
                        moved.alive.push(NewEdge {
                            previous: parent.flag() - EdgeFlags::PARENT,
                            flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                            from: parent.dest().to_option(),
                            to: current_pos.inode_vertex().to_option(),
                            introduced_by: Some(parent.introduced_by()),
                        })
                    }
                    moved.need_new_name = false;
                    // We've found an alive parent, delete the others.
                    is_first_parent = false;
                } else {
                    // Clean up the extra deleted edges.
                    debug!("cleanup");
                    let v = del_del
                        .entry((grandparent.dest(), parent_dest))
                        .or_insert_with(HashSet::new);
                    v.insert(Some(grandparent.introduced_by()));
                }
            } else if grandparent_changed
                || name_changed
                || (meta_changed && cfg!(unix))
                || !is_first_parent
            {
                if !parent.flag().contains(EdgeFlags::PSEUDO) {
                    moved.edges.push(NewEdge {
                        previous: parent.flag() - EdgeFlags::PARENT - EdgeFlags::PSEUDO,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK | EdgeFlags::DELETED,
                        from: grandparent.dest().to_option(),
                        to: parent_dest.to_option(),
                        introduced_by: Some(grandparent.introduced_by()),
                    });
                    // The following extra edge is meant to allow
                    // detection of missing contexts in folders: indeed,
                    // if we didn't have it, we couldn't tell the
                    // difference between a convergent renaming or
                    // deletion and a conflict between a renaming and a
                    // deletion.\
                    if !parent_was_resurrected {
                        moved.alive.push(NewEdge {
                            previous: parent.flag() - EdgeFlags::PARENT,
                            flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                            from: parent.dest().to_option(),
                            to: current_pos.inode_vertex().to_option(),
                            introduced_by: Some(parent.introduced_by()),
                        })
                    }
                }
            } else {
                last_alive_meta = Some(new_meta);
                let v = alive
                    .entry((grandparent.dest(), *parent_dest))
                    .or_insert_with(HashSet::new);
                v.insert(Some(grandparent.introduced_by()));
                moved.need_new_name = false;
                // We've found an alive parent, delete the others.
                is_first_parent = false;
            }
        }
        if name_is_alive {
            moved.n_alive_names += 1
        }
    }

    for ((from, to), intro) in del_del {
        if intro.len() > 1 {
            for introduced_by in intro {
                if introduced_by.is_some() {
                    moved.edges.push(NewEdge {
                        previous: EdgeFlags::FOLDER | EdgeFlags::BLOCK | EdgeFlags::DELETED,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK | EdgeFlags::DELETED,
                        from: from.to_option(),
                        to: to.to_option(),
                        introduced_by,
                    })
                }
            }
        }
    }

    debug!("alive = {:#?}", alive);

    for ((from, to), intro) in alive {
        if intro.len() > 1 || !moved.resurrect.is_empty() {
            for introduced_by in intro {
                if introduced_by.is_some() {
                    moved.alive.push(NewEdge {
                        previous: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                        flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK,
                        from: from.to_option(),
                        to: to.to_option(),
                        introduced_by,
                    })
                }
            }
        }
    }

    Ok(moved)
}

/// Is this vertex a (potentially deleted) "root vertex", i.e. a root
/// of the file hierarchy?
fn is_root_vertex<T: GraphTxnT>(
    txn: &T,
    channel: &T::Graph,
    v: Position<ChangeId>,
) -> Result<bool, TxnErr<T::GraphError>> {
    for parent in iter_adjacent(
        txn,
        channel,
        v.inode_vertex(),
        EdgeFlags::FOLDER | EdgeFlags::PARENT,
        EdgeFlags::all(),
    )? {
        let parent = parent?;
        if !parent.flag().contains(EdgeFlags::PARENT) {
            continue;
        }
        let p = parent.dest();
        let p = txn.find_block_end(channel, p).unwrap();
        if p.start == p.end {
            return Ok(true);
        } else {
            return Ok(false);
        }
    }
    Ok(false)
}

impl Recorded {
    fn record_deleted_file<T: GraphTxnT + TreeTxnT, W: WorkingCopyRead, C: ChangeStore>(
        &mut self,
        txn: &T,
        channel: &T::Graph,
        working_copy: &W,
        full_path: &str,
        current_vertex: Position<ChangeId>,
        changes: &C,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as WorkingCopyRead>::Error: 'static,
    {
        debug!("record_deleted_file {:?} {:?}", current_vertex, full_path);
        let mut stack = vec![(current_vertex.inode_vertex(), None)];
        let mut visited = HashSet::default();
        let mut full_path = std::borrow::Cow::Borrowed(full_path);
        while let Some((vertex, inode)) = stack.pop() {
            debug!("vertex {:?}, inode {:?}", vertex, inode);
            if let Some(path) = tree_path(txn, &vertex.start_pos())? {
                if working_copy.file_metadata(&path).is_ok() {
                    debug!("not deleting {:?}", path);
                    continue;
                }
                full_path = path.into()
            }

            // Kill this vertex
            if let Some(inode) = inode {
                self.delete_file_edge(txn, channel, vertex, inode)?
            } else if vertex.start == vertex.end {
                debug!("delete_recursively {:?}", vertex);
                // Killing an inode.
                {
                    let mut deleted_vertices = self.deleted_vertices.lock();
                    if !deleted_vertices.insert(vertex.start_pos()) {
                        continue;
                    }
                }
                if let Some(inode) = txn.get_revinodes(&vertex.start_pos(), None)? {
                    debug!(
                        "delete_recursively, vertex = {:?}, inode = {:?}",
                        vertex, inode
                    );
                    self.recorded_inodes
                        .lock()
                        .insert(*inode, vertex.start_pos().to_option());
                    self.updatables.insert(
                        self.actions.len() + 1,
                        InodeUpdate::Deleted { inode: *inode },
                    );
                }
                self.delete_inode_vertex::<_, _, W>(
                    changes,
                    txn,
                    channel,
                    vertex,
                    vertex.start_pos(),
                    &full_path,
                )?
            }

            // Move on to the descendants.
            for edge in iter_adjacent(
                txn,
                channel,
                vertex,
                EdgeFlags::empty(),
                EdgeFlags::all() - EdgeFlags::DELETED - EdgeFlags::PARENT,
            )? {
                let edge = edge?;
                debug!("delete_recursively, edge: {:?}", edge);
                let dest = txn
                    .find_block(channel, edge.dest())
                    .expect("delete_recursively, descendants");
                let inode = if inode.is_some() {
                    assert!(!edge.flag().contains(EdgeFlags::FOLDER));
                    inode
                } else if edge.flag().contains(EdgeFlags::FOLDER) {
                    None
                } else {
                    assert_eq!(vertex.start, vertex.end);
                    Some(vertex.start_pos())
                };
                if visited.insert(edge.dest()) {
                    stack.push((*dest, inode))
                }
            }
        }
        Ok(())
    }

    fn delete_inode_vertex<T: GraphTxnT + TreeTxnT, C: ChangeStore, W: WorkingCopyRead>(
        &mut self,
        changes: &C,
        txn: &T,
        channel: &T::Graph,
        vertex: Vertex<ChangeId>,
        inode: Position<ChangeId>,
        path: &str,
    ) -> Result<(), RecordError<C::Error, W::Error, T>>
    where
        <W as WorkingCopyRead>::Error: 'static,
    {
        debug!("delete_inode_vertex {:?}", path);
        let mut edges = Vec::new();
        let mut enc = None;
        let mut previous_name = Vec::new();
        for parent in iter_adjacent(
            txn,
            channel,
            vertex,
            EdgeFlags::FOLDER | EdgeFlags::PARENT,
            EdgeFlags::all(),
        )? {
            let parent = parent?;
            if !parent.flag().contains(EdgeFlags::PARENT) {
                continue;
            }
            assert!(parent.flag().contains(EdgeFlags::FOLDER));
            let parent_dest = txn.find_block_end(channel, parent.dest()).unwrap();
            if enc.is_none() {
                previous_name.resize(parent_dest.end - parent_dest.start, 0);
                let FileMetadata { encoding, .. } = changes
                    .get_file_meta(
                        |p| txn.get_external(&p).unwrap().map(From::from),
                        *parent_dest,
                        &mut previous_name,
                    )
                    .map_err(RecordError::Changestore)?;
                enc = Some(encoding);
            }

            for grandparent in iter_adjacent(
                txn,
                channel,
                *parent_dest,
                EdgeFlags::FOLDER | EdgeFlags::PARENT,
                EdgeFlags::all(),
            )? {
                let grandparent = grandparent?;
                if !grandparent.flag().contains(EdgeFlags::PARENT)
                    || grandparent.flag().contains(EdgeFlags::PSEUDO)
                {
                    continue;
                }
                assert!(grandparent.flag().contains(EdgeFlags::PARENT));
                assert!(grandparent.flag().contains(EdgeFlags::FOLDER));
                edges.push(NewEdge {
                    previous: grandparent.flag() - EdgeFlags::PARENT,
                    flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK | EdgeFlags::DELETED,
                    from: grandparent.dest().to_option(),
                    to: parent_dest.to_option(),
                    introduced_by: Some(grandparent.introduced_by()),
                });
            }
            if !parent.flag().contains(EdgeFlags::PSEUDO) {
                edges.push(NewEdge {
                    previous: parent.flag() - EdgeFlags::PARENT,
                    flag: EdgeFlags::FOLDER | EdgeFlags::BLOCK | EdgeFlags::DELETED,
                    from: parent.dest().to_option(),
                    to: vertex.to_option(),
                    introduced_by: Some(parent.introduced_by()),
                });
            }
        }
        debug!("deleting {:?}", edges);
        if !edges.is_empty() {
            self.actions.push(Hunk::FileDel {
                del: Atom::EdgeMap(EdgeMap {
                    edges,
                    inode: inode.to_option(),
                }),
                contents: None,
                path: path.to_string(),
                encoding: enc.unwrap(),
            })
        }
        Ok(())
    }

    fn delete_file_edge<T: GraphTxnT>(
        &mut self,
        txn: &T,
        channel: &T::Graph,
        to: Vertex<ChangeId>,
        inode: Position<ChangeId>,
    ) -> Result<(), TxnErr<T::GraphError>> {
        if let Some(Hunk::FileDel { contents, .. }) = self.actions.last_mut() {
            if contents.is_none() {
                *contents = Some(Atom::EdgeMap(EdgeMap {
                    edges: Vec::new(),
                    inode: inode.to_option(),
                }))
            }
            if let Some(Atom::EdgeMap(mut e)) = contents.take() {
                for parent in iter_adjacent(
                    txn,
                    channel,
                    to,
                    EdgeFlags::PARENT,
                    EdgeFlags::all() - EdgeFlags::DELETED,
                )? {
                    let parent = parent?;
                    if parent.flag().contains(EdgeFlags::PSEUDO) {
                        continue;
                    }
                    assert!(parent.flag().contains(EdgeFlags::PARENT));
                    assert!(!parent.flag().contains(EdgeFlags::FOLDER));
                    e.edges.push(NewEdge {
                        previous: parent.flag() - EdgeFlags::PARENT,
                        flag: (parent.flag() - EdgeFlags::PARENT) | EdgeFlags::DELETED,
                        from: parent.dest().to_option(),
                        to: to.to_option(),
                        introduced_by: Some(parent.introduced_by()),
                    })
                }
                if !e.edges.is_empty() {
                    *contents = Some(Atom::EdgeMap(e))
                }
            }
        } else {
            unreachable!()
        }
        Ok(())
    }
}
