//! Fast, side-effect-free status for shell prompts.

//!

//! Every snapshot and checkout writes a manifest of the working copy as it

//! was last seen: `size`, `mtime`, and BLAKE3 of each file. `quick_status`

//! walks the working copy and compares against that manifest, reading a

//! file's content only when its size or mtime changed, and records no

//! operation. Ahead/behind counts come from walking the store between the

//! local bookmark and its `origin` tracking state.

use super::*;

use std::time::UNIX_EPOCH;

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

pub struct PromptInfo {

    pub bookmark: String,

    /// Working-copy ChangeId prefix.

    pub change_id: String,

    pub heads: usize,

    pub dirty: bool,

    pub conflicted: bool,

    /// Changes local `main` has that `origin/main` lacks, when tracking exists.

    pub ahead: Option<usize>,

    pub behind: Option<usize>,

}

impl PromptInfo {

    /// The glyph for the working copy's state: `‼` conflicted, `✎` dirty,

    /// `✔` clean.

    pub fn state_glyph(&self) -> &'static str {

        if self.conflicted {

            "‼"

        } else if self.dirty {

            "✎"

        } else {

            "✔"

        }

    }

    /// The ANSI colour (SGR parameter) for the state: red, yellow, or cyan.

    pub fn state_color(&self) -> u8 {

        if self.conflicted {

            31

        } else if self.dirty {

            33

        } else {

            36

        }

    }

    /// `format` wrapped in the state colour. `guard` is `("\\[", "\\]")` for

    /// bash prompts, `("%{", "%}")` for zsh, or empty for raw output.

    pub fn format_colored(&self, fmt: &str, guard: (&str, &str)) -> String {

        format!(

            "{}\x1b[{}m{}{}{}\x1b[0m{}",

            guard.0,

            self.state_color(),

            guard.1,

            self.format(fmt),

            guard.0,

            guard.1

        )

    }

    /// Expand `%b` bookmark, `%c` change id, `%h` heads, `%d` dirty marker

    /// (`*`), `%x` conflict marker (`!`), `%a`/`%B` ahead/behind counts

    /// (empty when unknown), `%A`/`%D` `+n`/`-n` when non-zero, `%s` the

    /// state glyph, `%U`/`%O` `↑n`/`↓n` when non-zero, `%i` the repository

    /// icon, `%%` percent.

    pub fn format(&self, fmt: &str) -> String {

        let mut out = String::new();

        let mut chars = fmt.chars();

        while let Some(c) = chars.next() {

            if c != '%' {

                out.push(c);

                continue;

            }

            match chars.next() {

                Some('b') => out.push_str(&self.bookmark),

                Some('c') => out.push_str(&self.change_id),

                Some('h') => out.push_str(&self.heads.to_string()),

                Some('d') => {

                    if self.dirty {

                        out.push('*');

                    }

                }

                Some('x') => {

                    if self.conflicted {

                        out.push('!');

                    }

                }

                Some('a') => out.push_str(&self.ahead.map(|n| n.to_string()).unwrap_or_default()),

                Some('B') => out.push_str(&self.behind.map(|n| n.to_string()).unwrap_or_default()),

                Some('A') => {

                    if let Some(n) = self.ahead.filter(|n| *n > 0) {

                        out.push_str(&format!("+{n}"));

                    }

                }

                Some('D') => {

                    if let Some(n) = self.behind.filter(|n| *n > 0) {

                        out.push_str(&format!("-{n}"));

                    }

                }

                Some('s') => out.push_str(self.state_glyph()),

                Some('U') => {

                    if let Some(n) = self.ahead.filter(|n| *n > 0) {

                        out.push_str(&format!("↑{n}"));

                    }

                }

                Some('O') => {

                    if let Some(n) = self.behind.filter(|n| *n > 0) {

                        out.push_str(&format!("↓{n}"));

                    }

                }

                Some('i') => out.push_str(ICON),

                Some('%') => out.push('%'),

                Some(other) => {

                    out.push('%');

                    out.push(other);

                }

                None => out.push('%'),

            }

        }

        out

    }

}

/// Path → (size, mtime in nanoseconds, BLAKE3 hex) as last seen.

/// One manifest entry: the file's stat, its content hash, and the stored

/// blob for an opaque file.

#[derive(Clone, Debug)]

pub(crate) struct ManifestEntry {

    pub size: u64,

    pub mtime_ns: u128,

    pub hash: String,

    pub blob: Option<ObjectRef>,

    /// The graph key (`State::graph_key`) of the base file this text file

    /// was found equal to, rendered, byte for byte.

    pub graph: Option<String>,

}

#[derive(Clone, Debug, Default)]

pub(crate) struct Manifest {

    /// When the manifest was written, for the racy-stat guard.

    pub written_ns: u128,

    pub entries: BTreeMap<String, ManifestEntry>,

}

pub(crate) fn mtime_ns(m: &fs::Metadata) -> u128 {

    m.modified()

        .ok()

        .and_then(|t| t.duration_since(UNIX_EPOCH).ok())

        .map(|d| d.as_nanos())

        .unwrap_or(0)

}

pub const DEFAULT_PROMPT_FORMAT: &str = "%b %c%d%x%A%D";

/// The repository icon for `%i` (an atom, for oxygen).

pub const ICON: &str = "⚛";

/// A format with glyphs: icon, bookmark, change id, state, ahead/behind.

pub const GLYPH_PROMPT_FORMAT: &str = "%i %b %c %s%U%O";

/// One manifest line per file: size, mtime in nanoseconds, hash, blob ref

/// or `-`, graph key or `-`, path.

fn manifest_line(

    path: &str,

    size: u64,

    mtime_ns: u128,

    hash: &str,

    blob: Option<ObjectRef>,

    graph: Option<&str>,

) -> String {

    format!(

        "{size}\t{mtime_ns}\t{hash}\t{}\t{}\t{path}\n",

        blob.map(|b| b.to_hex()).unwrap_or_else(|| "-".into()),

        graph.unwrap_or("-")

    )

}

impl Repo {

    pub(crate) fn manifest_path(&self) -> PathBuf {

        self.oxy

            .join("workspaces")

            .join(self.workspace.to_hex())

            .join("manifest")

    }

    /// Record the working copy as it is now (after a snapshot, commit, or

    /// checkout), with header lines saying whether the base state is

    /// conflicted and whether the working-copy change holds uncommitted work.

    pub(crate) fn write_manifest(&self, conflicted: bool, uncommitted: bool) -> Result<()> {

        let entries = self.walk_working_copy()?;

        self.write_manifest_entries(conflicted, uncommitted, &entries, &HashMap::new())

    }

    /// Write the manifest from entries already walked; `blobs` names the

    /// stored blob of each opaque path so the next walk can skip reading it.

    pub(crate) fn write_manifest_entries(

        &self,

        conflicted: bool,

        uncommitted: bool,

        entries: &BTreeMap<String, FsEntry>,

        blobs: &HashMap<String, ObjectRef>,

    ) -> Result<()> {

        let written = std::time::SystemTime::now()

            .duration_since(UNIX_EPOCH)

            .map(|d| d.as_nanos())

            .unwrap_or(0);

        let head = format!(

            "# conflicted={}\n# uncommitted={}\n",

            conflicted as u8, uncommitted as u8

        );

        let mut body = String::new();

        let mut newest_ns: u128 = 0;

        for (path, e) in entries {

            let full = self.root.join(path);

            let (size, mtime_ns) = match fs::symlink_metadata(&full) {

                Ok(m) => (m.len(), mtime_ns(&m)),

                Err(_) => (e.content.len() as u64, 0),

            };

            let hash = match &e.content_hash {

                Some(h) => h.clone(),

                None => blake3::hash(&e.content).to_hex().to_string(),

            };

            let blob = blobs.get(path).copied().or(e.blob);

            newest_ns = newest_ns.max(mtime_ns);

            body.push_str(&manifest_line(

                path,

                size,

                mtime_ns,

                &hash,

                blob,

                e.graph_key.as_deref(),

            ));

        }

        let p = self.manifest_path();

        // Leave an unchanged manifest alone when its stamp already trusts

        // every entry (none is within the racy window): rewriting it would

        // change nothing but the file, which editors watching the tree

        // (and subrepos inside it) take as a change.

        if let Ok(old) = fs::read_to_string(&p) {

            let old_written: Option<u128> = old.lines().find_map(|l| {

                l.strip_prefix("# written=")

                    .and_then(|v| v.trim().parse().ok())

            });

            let old_rest: String = old

                .lines()

                .filter(|l| !l.starts_with("# written="))

                .map(|l| format!("{l}\n"))

                .collect();

            if let Some(w) = old_written {

                if old_rest == format!("{head}{body}") && newest_ns + 2_000_000_000 < w {

                    return Ok(());

                }

            }

        }

        let text = format!("{head}# written={written}\n{body}");

        fs::create_dir_all(p.parent().unwrap())?;

        write_atomic(&p, text.as_bytes())

    }

    /// Change the header flags, and set the graph key of each path in

    /// `keys` (after a commit, the new base's keys of the files it holds as

    /// they are on disk).

    pub(crate) fn rewrite_manifest(

        &self,

        conflicted: bool,

        uncommitted: bool,

        keys: &HashMap<String, String>,

    ) -> Result<()> {

        let p = self.manifest_path();

        let text = match fs::read_to_string(&p) {

            Ok(t) => t,

            Err(_) => return self.write_manifest(conflicted, uncommitted),

        };

        let mut out = String::with_capacity(text.len());

        for line in text.lines() {

            if line.starts_with("# conflicted=") {

                out.push_str(&format!("# conflicted={}\n", conflicted as u8));

            } else if line.starts_with("# uncommitted=") {

                out.push_str(&format!("# uncommitted={}\n", uncommitted as u8));

            } else {

                let f: Vec<&str> = line.splitn(6, '\t').collect();

                match (f.len() == 6).then(|| keys.get(f[5])).flatten() {

                    Some(k) => out.push_str(&format!(

                        "{}\t{}\t{}\t{}\t{k}\t{}\n",

                        f[0], f[1], f[2], f[3], f[5]

                    )),

                    None => {

                        out.push_str(line);

                        out.push('\n');

                    }

                }

            }

        }

        write_atomic(&p, out.as_bytes())

    }

    /// Forget the manifest after an operation that changed the working-copy

    /// change without a snapshot (undo, rewrites); the prompt shows blank

    /// markers until the next snapshot.

    pub(crate) fn drop_manifest(&self) {

        let _ = fs::remove_file(self.manifest_path());

    }

    pub(crate) fn read_manifest(&self) -> Result<Option<(bool, bool, Manifest)>> {

        let text = match fs::read_to_string(self.manifest_path()) {

            Ok(t) => t,

            Err(e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(None),

            Err(e) => return Err(e.into()),

        };

        let mut out = Manifest::default();

        let mut conflicted = false;

        let mut uncommitted = false;

        for line in text.lines() {

            if let Some(v) = line.strip_prefix("# conflicted=") {

                conflicted = v.trim() == "1";

                continue;

            }

            if let Some(v) = line.strip_prefix("# uncommitted=") {

                uncommitted = v.trim() == "1";

                continue;

            }

            if let Some(v) = line.strip_prefix("# written=") {

                out.written_ns = v.trim().parse().unwrap_or(u128::MAX);

                continue;

            }

            let f: Vec<&str> = line.splitn(6, '\t').collect();

            if f.len() == 6 {

                out.entries.insert(

                    f[5].to_string(),

                    ManifestEntry {

                        size: f[0].parse().unwrap_or(0),

                        mtime_ns: f[1].parse().unwrap_or(0),

                        hash: f[2].to_string(),

                        blob: ObjectRef::from_hex(f[3]),

                        graph: (f[4] != "-").then(|| f[4].to_string()),

                    },

                );

            }

        }

        Ok(Some((conflicted, uncommitted, out)))

    }

    /// Whether the working copy differs from the last manifest. Without a

    /// manifest the answer is `None`.

    pub fn quick_dirty(&self) -> Result<Option<bool>> {

        let Some((_, uncommitted, manifest)) = self.read_manifest()? else {

            return Ok(None);

        };

        if uncommitted {

            return Ok(Some(true));

        }

        let mut seen = 0usize;

        let nested = std::sync::Arc::new(std::sync::Mutex::new(Vec::new()));

        let wb = self.walker(&nested);

        for entry in wb.build() {

            let Ok(entry) = entry else { continue };

            let Some(ft) = entry.file_type() else {

                continue;

            };

            if ft.is_dir() {

                continue;

            }

            let rel: String = entry

                .path()

                .strip_prefix(&self.root)

                .unwrap()

                .components()

                .map(|c| c.as_os_str().to_string_lossy().to_string())

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

                .join("/");

            if !self.in_scope(&rel) {

                continue;

            }

            let Some(me) = manifest.entries.get(&rel) else {

                return Ok(Some(true));

            };

            seen += 1;

            let m = fs::symlink_metadata(entry.path())?;

            let now_mtime = mtime_ns(&m);

            if ft.is_symlink() {

                let target = fs::read_link(entry.path())?;

                if blake3::hash(target.to_string_lossy().as_bytes())

                    .to_hex()

                    .as_str()

                    != me.hash

                {

                    return Ok(Some(true));

                }

                continue;

            }

            if m.len() != me.size {

                return Ok(Some(true));

            }

            if now_mtime != me.mtime_ns

                && blake3::hash(&fs::read(entry.path())?).to_hex().as_str() != me.hash

            {

                return Ok(Some(true));

            }

        }

        if seen == manifest.entries.len() {

            return Ok(Some(false));

        }

        // Manifest entries the walk skipped: tracked files that ignore rules

        // hide. They count as present when still on disk and unchanged.

        for (rel, me) in &manifest.entries {

            let path = self.root.join(rel);

            let Ok(m) = fs::symlink_metadata(&path) else {

                return Ok(Some(true));

            };

            if m.file_type().is_symlink() {

                continue;

            }

            if m.len() != me.size

                || (mtime_ns(&m) != me.mtime_ns

                    && blake3::hash(&fs::read(&path)?).to_hex().as_str() != me.hash)

            {

                return Ok(Some(true));

            }

        }

        Ok(Some(false))

    }

    /// Prompt information without recording anything.

    pub fn quick_status(&self) -> Result<PromptInfo> {

        let view = self.view()?;

        let bookmark = self.config.bookmark.clone();

        let heads = self.heads_of(&view, &bookmark)?;

        let wc_hash = view.workspaces.get(&self.workspace).copied();

        let change_id = match wc_hash {

            Some(h) => self.store.get_change(&h)?.change_id.short(8),

            None => String::new(),

        };

        // Conflictedness was recorded by the last snapshot; without a

        // manifest (never snapshotted) both flags are unknown and shown clear.

        let manifest = self.read_manifest()?;

        let conflicted = manifest.as_ref().map(|(c, _, _)| *c).unwrap_or(false);

        let dirty = self.quick_dirty()?.unwrap_or(false);

        let (ahead, behind) = match view.remotes.get("origin").and_then(|b| b.get(&bookmark)) {

            Some(st) => {

                let remote_heads = self.store.get_state(st)?.heads;

                let ahead = self.negotiate(&remote_heads, &heads).map(|v| v.len()).ok();

                let behind = self.negotiate(&heads, &remote_heads).map(|v| v.len()).ok();

                (ahead, behind)

            }

            None => (None, None),

        };

        Ok(PromptInfo {

            bookmark,