//! Inspection (spec §27): blame from atom keys, and bisect over

//! dependency-closed prefixes of the candidates between a good and a bad

//! state.

use super::*;

/// One line of `oxy blame`.

#[derive(Clone, Debug)]

pub struct BlameLine {

    pub line: usize,

    pub hash: ChangeHash,

    pub index: u32,

    pub change_id: ChangeId,

    pub author: String,

    pub when_ms: u64,

    pub text: Vec<u8>,

}

/// Where a bisect stands.

#[derive(Clone, Debug, PartialEq, Eq)]

pub enum BisectStep {

    /// More `good`/`bad` marks are needed before the search can start.

    NeedMarks { good: usize, bad: usize },

    /// A state is checked out for testing.

    Testing {

        heads: Vec<ChangeHash>,

        remaining: usize,

        steps_left: u32,

    },

    /// The first change whose inclusion makes the state bad.

    Found { culprit: ChangeHash },

    /// Every remaining candidate was skipped.

    Inconclusive { candidates: Vec<ChangeHash> },

}

#[derive(Clone, Debug, Default)]

struct BisectState {

    start: Vec<ChangeHash>,

    good: Vec<ChangeHash>,

    bad: Vec<ChangeHash>,

    candidates: Vec<ChangeHash>,

    lo: usize,

    hi: usize,

    /// The prefix length currently checked out for testing.

    testing: Option<usize>,

    skipped: Vec<usize>,

}

fn hashes_line(v: &[ChangeHash]) -> String {

    v.iter().map(|h| h.to_hex()).collect::<Vec<_>>().join(" ")

}

fn hashes_from(s: &str) -> Vec<ChangeHash> {

    s.split_whitespace()

        .filter_map(ObjectRef::from_hex)

        .collect()

}

impl Repo {

    /// The introducing change, author, and date of every line of `path` in

    /// the working copy's base state (spec §27).

    pub fn blame(&self, path: &str) -> Result<Vec<BlameLine>> {

        let snap = self.snapshot("oxy blame")?;

        self.blame_state(

            path,

            &snap.base,

            &snap.base_snapshot,

            "the working copy's base state",

        )

    }

    /// Blame `path` in the state with these heads (hosted repositories).

    pub fn blame_in(&self, path: &str, heads: &[ChangeHash]) -> Result<Vec<BlameLine>> {

        let state = self.load_state(heads)?;

        let snapshot = state.materialize();

        self.blame_state(path, &state, &snapshot, "that state")

    }

    fn blame_state(

        &self,

        path: &str,

        state: &crate::state::State,

        snapshot: &crate::state::Snapshot,

        what: &str,

    ) -> Result<Vec<BlameLine>> {

        let Some(f) = snapshot.files.get(path) else {

            return fail(format!("{path} is not in {what}"));

        };

        if !matches!(f.content, FileContent::Text { .. }) {

            return fail(format!("{path} is not a text file"));

        }

        let mut out = Vec::new();

        for (i, ((hash, index), text)) in state.live_lines(&f.node).into_iter().enumerate() {

            let meta = state.get(&hash);

            let author = match meta {

                Some(m) if !m.author.is_zero() => self

                    .store

                    .get_identity(&m.author)

                    .map(|id| id.name)

                    .unwrap_or_else(|_| m.author.short(12)),

                Some(m) => m

                    .message

                    .lines()

                    .rev()

                    .find_map(|l| l.strip_prefix("Git-Author: "))

                    .map(|a| a.split('<').next().unwrap_or(a).trim().to_string())

                    .unwrap_or_else(|| "unknown".into()),

                None => "unknown".into(),

            };

            out.push(BlameLine {

                line: i + 1,

                hash,

                index,

                change_id: meta.map(|m| m.change_id).unwrap_or(ChangeId([0; 16])),

                author,

                when_ms: meta.map(|m| m.hlc.wall_ms).unwrap_or(0),

                text,

            });

        }

        Ok(out)

    }

    // ------------------------------------------------------------ bisect

    fn bisect_dir(&self) -> PathBuf {

        self.oxy.join("bisect")

    }

    fn bisect_load(&self) -> Result<Option<BisectState>> {

        let dir = self.bisect_dir();

        if !dir.join("start").exists() {

            return Ok(None);

        }

        let read = |name: &str| fs::read_to_string(dir.join(name)).unwrap_or_default();

        let nums: Vec<usize> = read("range")

            .split_whitespace()

            .filter_map(|n| n.parse().ok())

            .collect();

        Ok(Some(BisectState {

            start: hashes_from(&read("start")),

            good: hashes_from(&read("good")),

            bad: hashes_from(&read("bad")),

            candidates: hashes_from(&read("candidates")),

            lo: nums.first().copied().unwrap_or(0),

            hi: nums.get(1).copied().unwrap_or(0),

            testing: nums.get(2).copied().filter(|_| nums.len() > 2),

            skipped: read("skipped")

                .split_whitespace()

                .filter_map(|n| n.parse().ok())

                .collect(),

        }))

    }

    fn bisect_save(&self, st: &BisectState) -> Result<()> {

        let dir = self.bisect_dir();

        fs::create_dir_all(&dir)?;

        write_atomic(&dir.join("start"), hashes_line(&st.start).as_bytes())?;

        write_atomic(&dir.join("good"), hashes_line(&st.good).as_bytes())?;

        write_atomic(&dir.join("bad"), hashes_line(&st.bad).as_bytes())?;

        write_atomic(

            &dir.join("candidates"),

            hashes_line(&st.candidates).as_bytes(),

        )?;

        let mut range = format!("{} {}", st.lo, st.hi);

        if let Some(t) = st.testing {

            range.push_str(&format!(" {t}"));

        }

        write_atomic(&dir.join("range"), range.as_bytes())?;

        write_atomic(

            &dir.join("skipped"),

            st.skipped

                .iter()

                .map(|n| n.to_string())

                .collect::<Vec<_>>()

                .join(" ")

                .as_bytes(),

        )?;

        Ok(())

    }

    /// Begin a bisect: remembers the working copy's base to restore later.

    pub fn bisect_start(&self) -> Result<()> {

        if self.bisect_load()?.is_some() {

            return fail("a bisect is in progress; finish it or run `oxy bisect reset`");

        }

        let (_, wc) = self.working_copy()?;

        let start = self.load_state(&wc.deps)?.maximal(&wc.deps);

        self.bisect_save(&BisectState {

            start,

            ..Default::default()

        })

    }

    pub fn bisect_reset(&self) -> Result<()> {

        let Some(st) = self.bisect_load()? else {

            return fail("no bisect in progress");

        };

        self.checkout(&st.start, false, "oxy bisect reset")?;

        fs::remove_dir_all(self.bisect_dir())?;

        Ok(())

    }

    pub fn bisect_status(&self) -> Result<Option<BisectStep>> {

        let Some(st) = self.bisect_load()? else {

            return Ok(None);

        };

        Ok(Some(self.bisect_step(&st)))

    }

    fn bisect_step(&self, st: &BisectState) -> BisectStep {

        if st.candidates.is_empty() {

            return BisectStep::NeedMarks {

                good: st.good.len(),

                bad: st.bad.len(),

            };

        }

        if st.hi <= st.lo + 1 {

            return BisectStep::Found {

                culprit: st.candidates[st.lo],

            };

        }

        match st.testing {

            Some(_) => {

                let remaining = st.hi - st.lo;

                BisectStep::Testing {

                    heads: self.bisect_heads(st, st.testing.unwrap()),

                    remaining,

                    steps_left: (remaining as f64).log2().ceil() as u32,

                }

            }

            None => BisectStep::Inconclusive {

                candidates: st.candidates[st.lo..st.hi].to_vec(),

            },

        }

    }

    /// `good ∪ candidates[..k]`, as heads.

    fn bisect_heads(&self, st: &BisectState, k: usize) -> Vec<ChangeHash> {

        let mut all = st.good.clone();

        all.extend(st.candidates[..k].iter().copied());

        self.load_state(&all)

            .map(|s| s.maximal(&all))

            .unwrap_or(all)

    }

    /// Check out the midpoint of the open range, skipping indices marked

    /// untestable, and record it as the state under test.

    fn bisect_advance(&self, st: &mut BisectState) -> Result<BisectStep> {

        if st.hi <= st.lo + 1 {

            st.testing = None;

            self.bisect_save(st)?;

            return Ok(BisectStep::Found {

                culprit: st.candidates[st.lo],

            });

        }

        let mid = st.lo + (st.hi - st.lo) / 2;

        // Try mid, then the nearest untried indices on either side.

        let mut order = vec![mid];

        for d in 1..(st.hi - st.lo) {

            if mid + d < st.hi {

                order.push(mid + d);

            }

            if mid > st.lo + d {

                order.push(mid - d);

            }

        }

        let Some(k) = order.into_iter().find(|k| !st.skipped.contains(k)) else {

            st.testing = None;

            self.bisect_save(st)?;

            return Ok(BisectStep::Inconclusive {

                candidates: st.candidates[st.lo..st.hi].to_vec(),

            });

        };

        let heads = self.bisect_heads(st, k);

        self.checkout(

            &heads,

            false,

            &format!("oxy bisect (testing {k} of {})", st.candidates.len()),

        )?;

        st.testing = Some(k);

        self.bisect_save(st)?;

        let remaining = st.hi - st.lo;

        Ok(BisectStep::Testing {

            heads,

            remaining,

            steps_left: (remaining as f64).log2().ceil() as u32,

        })

    }

    /// Mark states good or bad. With `changes`, before the search starts,

    /// they name known-good or known-bad states; without, the state under

    /// test gets the verdict. `None` for `good` means skip (untestable).

    pub fn bisect_mark(&self, good: Option<bool>, changes: &[ChangeHash]) -> Result<BisectStep> {

        let Some(mut st) = self.bisect_load()? else {

            return fail("no bisect in progress; run `oxy bisect start`");

        };

        if !changes.is_empty() {

            if !st.candidates.is_empty() {

                return fail("the search has started; mark the state under test with plain `oxy bisect good|bad`");

            }

            match good {

                Some(true) => st.good.extend(changes.iter().copied()),

                Some(false) => st.bad.extend(changes.iter().copied()),

                None => return fail("skip applies to the state under test"),

            }

            if st.good.is_empty() || st.bad.is_empty() {

                self.bisect_save(&st)?;

                return Ok(BisectStep::NeedMarks {

                    good: st.good.len(),

                    bad: st.bad.len(),

                });

            }

            let good_heads = self.load_state(&st.good)?.maximal(&st.good);

            let bad_heads = self.load_state(&st.bad)?.maximal(&st.bad);

            st.good = good_heads.clone();

            st.bad = bad_heads.clone();

            st.candidates = self.negotiate(&good_heads, &bad_heads)?;

            if st.candidates.is_empty() {

                return fail("the bad state adds nothing to the good state; nothing to bisect");

            }

            st.lo = 0;

            st.hi = st.candidates.len();

            return self.bisect_advance(&mut st);

        }

        let Some(k) = st.testing else {

            return fail("no state is under test; give `oxy bisect good|bad` a change or bookmark to start with");

        };

        match good {

            Some(true) => st.lo = k,

            Some(false) => st.hi = k,

            None => st.skipped.push(k),

        }

        self.bisect_advance(&mut st)

    }

    /// Automate with a command run in the working copy: exit 0 is good, 125

    /// skips, anything else is bad.

    pub fn bisect_run(&self, command: &[String]) -> Result<BisectStep> {

        let Some(st) = self.bisect_load()? else {

            return fail("no bisect in progress; run `oxy bisect start`");

        };

        if st.testing.is_none() {

            return Ok(self.bisect_step(&st));

        }

        loop {

            let status = std::process::Command::new(&command[0])

                .args(&command[1..])

                .current_dir(&self.root)

                .status()

                .map_err(|e| RepoError::Msg(format!("running {}: {e}", command[0])))?;

            let verdict = match status.code() {

                Some(0) => Some(true),

                Some(125) => None,

                _ => Some(false),

            };

            match self.bisect_mark(verdict, &[])? {

                BisectStep::Testing { .. } => continue,

                done => return Ok(done),

            }

        }

    }

}