//! 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_meta(&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,
            change_id,
            heads: heads.len(),
            dirty,
            conflicted,
            ahead,
            behind,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn placeholders_and_glyphs() {
        let clean = PromptInfo {
            bookmark: "main".into(),
            change_id: "658990aa".into(),
            heads: 1,
            dirty: false,
            conflicted: false,
            ahead: Some(0),
            behind: None,
        };
        assert_eq!(clean.format(DEFAULT_PROMPT_FORMAT), "main 658990aa");
        assert_eq!(clean.format(GLYPH_PROMPT_FORMAT), "⚛ main 658990aa ✔");
        let busy = PromptInfo {
            dirty: true,
            ahead: Some(2),
            behind: Some(3),
            ..clean.clone()
        };
        assert_eq!(busy.format(DEFAULT_PROMPT_FORMAT), "main 658990aa*+2-3");
        assert_eq!(busy.format(GLYPH_PROMPT_FORMAT), "⚛ main 658990aa ✎↑2↓3");
        let bad = PromptInfo {
            conflicted: true,
            ..busy.clone()
        };
        assert_eq!(bad.format("%s%x%d %h %a/%B %%"), "‼!* 1 2/3 %");
        assert_eq!(bad.state_color(), 31);
        assert_eq!(
            busy.format_colored("%b", ("\\[", "\\]")),
            "\\[\x1b[33m\\]main\\[\x1b[0m\\]"
        );
        assert_eq!(clean.format_colored("%b", ("", "")), "\x1b[36mmain\x1b[0m");
        assert_eq!(clean.format("%q"), "%q");
    }
}