use std::fmt::Write as _;
use std::path::{Path, PathBuf};
use std::sync::Arc;

use anyhow::Context as _;
use itertools::{Itertools as _, izip};
use re_chunk::Chunk;

// ---

#[derive(Debug, Clone, clap::Parser)]
pub struct CompareCommand {
    path_to_rrd1: String,
    path_to_rrd2: String,

    /// If specified, the comparison will focus purely on semantics, ignoring order.
    ///
    /// The Rerun data model is itself unordered, and because many of the internal pipelines are
    /// asynchronous by nature, it is very easy to end up with semantically identical, but
    /// differently ordered data.
    /// In most cases, the distinction is irrelevant, and you'd rather the comparison succeeds.
    #[clap(long, default_value_t = false)]
    unordered: bool,

    /// If specified, dumps both .rrd files as tables.
    #[clap(long, default_value_t = false)]
    full_dump: bool,

    /// If specified, the comparison will ignore chunks without components.
    #[clap(long, default_value_t = false)]
    ignore_chunks_without_components: bool,

    /// Timelines to ignore entirely during comparison (their presence, absence, and values).
    ///
    /// Useful when comparing recordings produced with different default-timeline settings,
    /// e.g. `--ignore-timeline log_tick` (which is opt-in).
    /// Can be specified multiple times.
    #[clap(long = "ignore-timeline", value_name = "TIMELINE")]
    ignore_timelines: Vec<String>,
}

impl CompareCommand {
    /// Checks whether two .rrd files are _similar_, i.e. not equal on a byte-level but
    /// functionally equivalent.
    ///
    /// Returns `Ok(())` if they match, or an error containing a detailed diff otherwise.
    pub fn run(&self) -> anyhow::Result<()> {
        let Self {
            path_to_rrd1,
            path_to_rrd2,
            unordered,
            full_dump,
            ignore_chunks_without_components,
            ignore_timelines,
        } = self;

        let ignore_timelines: Vec<re_chunk::TimelineName> = ignore_timelines
            .iter()
            .map(|name| name.as_str().into())
            .collect();

        re_log::debug!("Comparing {path_to_rrd1:?} to {path_to_rrd2:?}…");

        let path_to_rrd1 = PathBuf::from(path_to_rrd1);
        let path_to_rrd2 = PathBuf::from(path_to_rrd2);

        let (app_id1, chunks1) = load_chunks(&path_to_rrd1, *ignore_chunks_without_components)
            .with_context(|| format!("path: {path_to_rrd1:?}"))?;
        let (app_id2, chunks2) = load_chunks(&path_to_rrd2, *ignore_chunks_without_components)
            .with_context(|| format!("path: {path_to_rrd2:?}"))?;

        if *full_dump {
            println!("{app_id1}");
            for chunk in &chunks1 {
                println!("{chunk}");
            }

            println!("{app_id2}");
            for chunk in &chunks2 {
                println!("{chunk}");
            }
        }

        anyhow::ensure!(
            app_id1 == app_id2,
            "Application IDs do not match: '{app_id1}' vs. '{app_id2}'"
        );

        fn format_chunk(chunk: &Chunk) -> String {
            re_arrow_util::format_record_batch_opts(
                &chunk.to_record_batch().expect("Cannot fail in practice"),
                &re_arrow_util::RecordBatchFormatOpts {
                    width: Some(800),
                    max_cell_content_width: 100,
                    trim_field_names: false,
                    trim_metadata_keys: false,
                    trim_metadata_values: false,
                    ..Default::default()
                },
            )
            .to_string()
        }

        if *unordered {
            let mut chunks2_remaining = chunks2;
            let mut unmatched_chunks1 = Vec::new();

            for chunk1 in &chunks1 {
                if let Some(pos) = chunks2_remaining.iter().position(|chunk2| {
                    re_chunk::Chunk::ensure_similar_ignoring_timelines(
                        chunk1,
                        chunk2,
                        &ignore_timelines,
                    )
                    .is_ok()
                }) {
                    chunks2_remaining.swap_remove(pos);
                } else {
                    unmatched_chunks1.push(chunk1.clone());
                }
            }

            if !unmatched_chunks1.is_empty() || !chunks2_remaining.is_empty() {
                let mut error_msg = String::from("Unordered comparison failed:\n");

                if !unmatched_chunks1.is_empty() {
                    writeln!(
                        error_msg,
                        "\n{} chunk(s) from {path_to_rrd1:?} could not be matched:",
                        unmatched_chunks1.len()
                    )
                    .ok();
                    for chunk in &unmatched_chunks1 {
                        writeln!(error_msg, "{}", format_chunk(chunk)).ok();
                    }
                }

                if !chunks2_remaining.is_empty() {
                    writeln!(
                        error_msg,
                        "\n{} chunk(s) from {path_to_rrd2:?} could not be matched:",
                        chunks2_remaining.len()
                    )
                    .ok();
                    for chunk in &chunks2_remaining {
                        writeln!(error_msg, "{}", format_chunk(chunk)).ok();
                    }
                }

                anyhow::bail!(error_msg);
            }
        } else {
            anyhow::ensure!(
                chunks1.len() == chunks2.len(),
                "Number of Chunks does not match: '{}' vs. '{}'",
                re_format::format_uint(chunks1.len()),
                re_format::format_uint(chunks2.len()),
            );

            for (chunk1, chunk2) in izip!(chunks1, chunks2) {
                re_chunk::Chunk::ensure_similar_ignoring_timelines(
                    &chunk1,
                    &chunk2,
                    &ignore_timelines,
                )
                .with_context(|| {
                    format!(
                        "Chunks diff:\n{}",
                        similar_asserts::SimpleDiff::from_str(
                            &format_chunk(&chunk1),
                            &format_chunk(&chunk2),
                            &path_to_rrd1.display().to_string(),
                            &path_to_rrd2.display().to_string(),
                        ),
                    )
                })?;
            }
        }

        re_log::debug!("{path_to_rrd1:?} and {path_to_rrd2:?} are similar enough.");

        Ok(())
    }
}

/// Given a path to an rrd file, builds up a `ChunkStore` and returns its contents a stream of
/// `Chunk`s.
///
/// Fails if there are more than one data recordings present in the rrd file.
fn load_chunks(
    path_to_rrd: &Path,
    ignore_chunks_without_components: bool,
) -> anyhow::Result<(re_log_types::ApplicationId, Vec<Arc<re_chunk::Chunk>>)> {
    use re_entity_db::EntityDb;
    use re_log_types::StoreId;

    let rrd_file = std::fs::File::open(path_to_rrd).context("couldn't open rrd file contents")?;
    let rrd_file = std::io::BufReader::new(rrd_file);

    // TODO(#10730): if the legacy `StoreId` migration is removed from `Decoder`, this would break
    // the ability of `rrd compare` pre-0.25 rrds. If we want to keep the ability to migrate here,
    // then the pre-#10730 app id caching mechanism must somehow be ported here.
    // TODO(ab): For pre-0.25 legacy data with `StoreId` missing their application id, the migration
    // in `Decoder` requires `SetStoreInfo` to arrive before the corresponding `ArrowMsg`. Ideally
    // this tool would cache orphan `ArrowMsg` until a matching `SetStoreInfo` arrives.
    let mut stores: std::collections::HashMap<StoreId, EntityDb> = Default::default();
    let decoder = re_log_encoding::DecoderApp::decode_lazy(rrd_file);
    for msg in decoder {
        let msg = msg.context("decode rrd message")?;
        stores
            .entry(msg.store_id().clone())
            .or_insert_with(|| {
                let enable_viewer_indexes = false; // that would just slow us down for no reason
                re_entity_db::EntityDb::with_store_config(
                    msg.store_id().clone(),
                    enable_viewer_indexes,
                    // We must make sure not to do any store-side compaction during comparisons, or
                    // this will result in flaky roundtrips in some instances.
                    re_chunk_store::ChunkStoreConfig::ALL_DISABLED,
                )
            })
            .add_log_msg(&msg)
            .context("decode rrd file contents")?;
    }

    let mut stores = stores
        .values()
        .filter(|store| store.store_kind() == re_log_types::StoreKind::Recording)
        .collect_vec();

    anyhow::ensure!(!stores.is_empty(), "no data recording found in rrd file");
    anyhow::ensure!(
        stores.len() == 1,
        "more than one data recording found in rrd file"
    );

    #[expect(clippy::unwrap_used)] // safe, ensured above
    let store = stores.pop().unwrap();
    let engine = store.storage_engine();

    Ok((
        store.application_id().clone(),
        engine
            .store()
            .iter_physical_chunks()
            .filter_map(|c| {
                if ignore_chunks_without_components {
                    (c.num_components() > 0).then_some(c.clone())
                } else {
                    Some(c.clone())
                }
            })
            .collect_vec(),
    ))
}
