//! §9 deliverable-verb base changes — one [`BaseChange`] per verb.
//!
//! Each verb authors a `tasks/<id>.md` diff at [`BaseChange::stage`], then
//! renders its §5 message at [`BaseChange::finalize`] by RE-READING the
//! post-`pre` tree (so a `create/pre` reassigned id, or a `pre` retitle, is
//! reflected). The impls are git-free — they read/write the worktree dir
//! directly, leaving the [`crate::lifecycle::Engine`]'s anvil the only git in
//! an op — and the clock and minted id are injected, so authoring is pure and
//! unit-testable on a plain temp dir.
//!
//! `claim`/`unclaim`/`close` are NAMED specializations of `update` (§9):
//! [`Occupancy`] fixes `claimant` (claim carries two guards — the already-claimed
//! refusal here, plus the §10 claim-blocker guard via [`crate::enforce`]),
//! [`Retire`] stages the file DELETION, [`Update`] applies a generic
//! [`FieldEdit`] list. Each mutating op runs the SAME op-keyed guard
//! ([`crate::enforce::gate`], §10/§15) for its own verb — `claim`/`close` via
//! their named [`crate::enforce::claim`]/[`crate::enforce::close`] spellings, the
//! rest (`unclaim`/`update`) directly — so a blocker on ANY op is honored.
//! They stay distinct ops because the op NAME is the §6 hook-dispatch key.
//!
//! The §10 guards run at [`BaseChange::stage`] — before the seal, so a refusal
//! aborts the op cleanly, and for `close` before any `close.pre` plugin (e.g.
//! delivery) squashes. The enforcement itself lives in [`crate::enforce`].

use std::fs;
use std::io;
use std::path::Path;

use crate::enforce;
use crate::lifecycle::BaseChange;
use crate::message::Message;
use crate::task::Task;
use crate::taskfile::{read_task, task_path, write_task};
use crate::verb::Verb;

// `create` (§9) — the only verb impl with a private helper — lives in a sibling
// module; re-exported so consumers keep reaching `crate::change::Create`.
#[path = "change_create.rs"]
mod create;
pub use create::Create;

/// `claim`/`unclaim` (§9): set or clear the one occupancy field. `claim` carries
/// the one hardcoded guard; `unclaim` is its symmetric clear. "Claimed" is the
/// derived view of `claimant`, so this is the only field either writes.
pub struct Occupancy {
    pub verb: Verb,
    pub id: String,
    pub claimant: Option<String>,
    pub actor: String,
    pub now: i64,
    /// The `-m` free commit-message narration (§5); occupancy edits no ball field.
    pub message: Option<String>,
    /// This checkout's root-commit identities (bl-0161), INJECTED at the CLI
    /// boundary — the SET of roots reachable from HEAD, since a multi-root repo
    /// answers to more than one. `claim` rejects only when the ball recorded a
    /// root that is NONE of these; read on `claim`, ignored on `unclaim`. Empty
    /// off a checkout with no code repo — a mismatch is then unprovable, so the
    /// guard passes (fail-open).
    pub current_roots: Vec<String>,
}

impl Occupancy {
    /// `claim`: take occupancy as `actor` (guarded against an existing claim).
    pub fn claim(id: String, actor: String, now: i64) -> Self {
        Self { verb: Verb::Claim, id, claimant: Some(actor.clone()), actor, now, message: None, current_roots: Vec::new() }
    }

    /// `unclaim`: release occupancy (clear `claimant`).
    pub fn unclaim(id: String, actor: String, now: i64) -> Self {
        Self { verb: Verb::Unclaim, id, claimant: None, actor, now, message: None, current_roots: Vec::new() }
    }
}

impl BaseChange for Occupancy {
    fn stage(&self, dir: &Path) -> io::Result<()> {
        let mut task = read_task(dir, &self.id)?;
        if self.verb == Verb::Claim {
            if let Some(who) = &task.claimant {
                return Err(io::Error::new(
                    io::ErrorKind::AlreadyExists,
                    format!("claim: {} is already claimed by {who}", self.id),
                ));
            }
            guard_repo(&task, &self.current_roots, &self.id)?;
            enforce::claim(&task, &self.id, dir)?;
        } else {
            enforce::gate(&task, Verb::Unclaim, &self.id, dir)?;
        }
        task.claimant.clone_from(&self.claimant);
        task.updated = self.now;
        write_task(dir, &self.id, &task)
    }

    fn finalize(&self, dir: &Path) -> io::Result<String> {
        finalize_titled(dir, self.verb, &self.actor, &self.id, self.message.as_deref())
    }
}

/// The bl-0161 admit test as a PURE predicate over a ball's recorded
/// [`Task::root_commit`] and this checkout's root SET — the ONE place the
/// this-project rule is spelled, shared by `claim`'s [`guard_repo`] and root-aware
/// `bl list`'s default scope (bl-5965), so list shows exactly what claim admits.
/// A ball is admitted when it recorded NO root (predates the guard, or born off
/// no code repo — unconstrained), when the checkout has NO roots (non-git dir,
/// pure task-list use — the mismatch is unprovable), or when the recorded root is
/// ANY of the checkout's (a multi-root repo answers to several; matching the whole
/// set means merging an unrelated history never flips identity). Every non-admit
/// is exactly one shape: recorded-root-present and in-none-of-the-set.
#[must_use]
pub(crate) fn admits(root_commit: Option<&str>, current_roots: &[String]) -> bool {
    root_commit.is_none_or(|recorded| current_roots.is_empty() || current_roots.iter().any(|r| r == recorded))
}

/// The wrong-repo claim guard (bl-1ce7, generalized bl-0161): reject a claim the
/// shared [`admits`] test refuses. The recorded hash NAMES the project the ball
/// belongs to — identity is the git root commit, remote-free — so the message
/// points at the right checkout without a path or a remote. A shared-root
/// collision grants nothing: the claimant would already be working from that very
/// directory.
fn guard_repo(task: &Task, current_roots: &[String], id: &str) -> io::Result<()> {
    let recorded = task.root_commit.as_deref();
    if admits(recorded, current_roots) {
        return Ok(());
    }
    Err(io::Error::new(
        io::ErrorKind::PermissionDenied,
        format!(
            "claim: {id} belongs to the project rooted at {}, but this checkout is \
             rooted at {} — claim it from that project's checkout",
            recorded.unwrap_or_default(),
            current_roots.join(", ")
        ),
    ))
}

/// `update` (§9): the generic field/body edit. Applies an ordered [`FieldEdit`]
/// list and bumps `updated`; an unknown `state:`-style key rides through as a
/// [`FieldEdit::SetExtra`] like any other preserved field (§3). EVERY field is
/// overwriteable here — title, body, parent, priority, tags, extras, blockers —
/// so there is no create-only split; the ball-body edit rides `edits`
/// ([`FieldEdit::Body`]) while `message` is the `-m` commit narration (§5).
pub struct Update {
    pub id: String,
    pub actor: String,
    pub now: i64,
    pub edits: Vec<FieldEdit>,
    /// The `-m` free commit-message narration (§5); the subject is the title.
    pub message: Option<String>,
}

impl BaseChange for Update {
    fn stage(&self, dir: &Path) -> io::Result<()> {
        let mut task = read_task(dir, &self.id)?;
        enforce::gate(&task, Verb::Update, &self.id, dir)?;
        for edit in &self.edits {
            edit.apply(&mut task);
        }
        task.updated = self.now;
        write_task(dir, &self.id, &task)
    }

    fn finalize(&self, dir: &Path) -> io::Result<String> {
        finalize_titled(dir, Verb::Update, &self.actor, &self.id, self.message.as_deref())
    }

    /// `update` is the one base that can stage a byte-identical tree (zero
    /// effective edits + a same-second `updated` restamp), hitting the no-op
    /// seal — its `-m` must refuse to converge rather than drop (bl-cf93).
    fn narrated(&self) -> bool {
        self.message.is_some()
    }
}

// The field-edit vocabulary (one [`FieldEdit`] per overwriteable field, plus
// the `--edit` whole-buffer `Replace`) lives in a sibling module; re-exported
// so consumers keep reaching `crate::change::FieldEdit`.
#[path = "change_field.rs"]
mod field;
pub use field::FieldEdit;

/// `close` (§9): retire a ball — stage the `tasks/<id>.md` DELETION. The
/// `title` is captured before deletion so [`BaseChange::finalize`] can still
/// render a §5 subject once the file is gone. Closing is the ONLY retirement:
/// abandonment is the composite `unclaim` then `close` (the empty deliverable
/// makes the delivery a no-op), so a `--blocks close` gate guards every way a
/// ball can die.
pub struct Retire {
    pub id: String,
    pub title: String,
    pub actor: String,
    /// The `-m` free commit-message narration (§5); retire edits no ball field.
    pub message: Option<String>,
}

impl Retire {
    /// `close`: retire a ball.
    pub fn close(id: String, title: String, actor: String) -> Self {
        Self { id, title, actor, message: None }
    }
}

impl BaseChange for Retire {
    fn stage(&self, dir: &Path) -> io::Result<()> {
        let task = read_task(dir, &self.id)?;
        enforce::close(&task, &self.id, dir)?;
        fs::remove_file(task_path(dir, &self.id))
    }

    fn finalize(&self, _dir: &Path) -> io::Result<String> {
        commit_message(Verb::Close, &self.actor, &self.id, &self.title, self.message.as_deref())
    }
}

/// The shared `finalize` body for the three verbs whose file survives the op
/// (create/claim/unclaim/update): RE-READ the post-`pre` title from `id` and
/// render its §5 message. `close` ([`Retire`]) can't use it — the file is gone,
/// so its title was captured at construction.
fn finalize_titled(dir: &Path, verb: Verb, actor: &str, id: &str, message: Option<&str>) -> io::Result<String> {
    let title = read_task(dir, id)?.title;
    commit_message(verb, actor, id, &title, message)
}

/// Build and render the §5 message: the subject is ALWAYS the ball `title` (the
/// op rides the `bl-op` trailer, not a flavored subject), and `message` is the
/// optional `-m` free body. There is no subject override — the title IS the
/// subject, so `git log` reads naturally and the body is pure narration.
fn commit_message(verb: Verb, actor: &str, id: &str, title: &str, message: Option<&str>) -> io::Result<String> {
    Message {
        verb,
        actor: actor.to_string(),
        id: Some(id.to_string()),
        subject: title.to_string(),
        body: message.map(str::to_string),
    }
    .render()
}

#[cfg(test)]
#[path = "change_tests.rs"]
mod tests;
