mcp_methods/server/

workspace.rs

//! Workspace mode — two variants.
//!
//! **Github mode** (`Workspace::open`, the default when
//! `--workspace DIR` is set): the agent activates a GitHub repo via
//! `repo_management('org/repo')`, the binary clones it into the
//! workspace, and the active repo becomes the bound source root for
//! `read_source` / `grep` / `list_source`. Idle repos auto-sweep after
//! `--stale-after-days`. Layout:
//!   workspace/
//!     repos/<org>/<repo>/         — cloned source
//!     inventory.json              — per-repo access tracking
//!
//! **Local mode** (`Workspace::open_local`, the manifest-driven
//! `workspace: { kind: local, root: ... }` variant): the active source
//! root is a fixed local directory, not a clone target. `repo_management`
//! reports the active root and triggers rebuilds; an `set_root_dir`
//! tool can swap the root at runtime. Closes the `code_review_mcp_server`
//! use case from the kglite wishlist.
//!
//! Both modes fire the same [`PostActivateHook`] so downstream binaries
//! (kglite-mcp-server) layer their build step on top with one
//! registration point, and both honour the same `last_built_sha`
//! gating to skip pointless rebuilds.

#![allow(dead_code)]

use std::collections::BTreeMap;
use std::fs;
use std::path::{Path, PathBuf};
use std::process::Command;
use std::sync::{Arc, RwLock};
use std::time::SystemTime;

use anyhow::{anyhow, Context, Result};
use serde::{Deserialize, Serialize};
use serde_json::json;

/// Repo name format: ``org/repo``. Letters, digits, dots, hyphens, underscores.
fn validate_repo_name(name: &str) -> Result<()> {
    let mut parts = name.split('/');
    let org = parts.next().unwrap_or("");
    let repo = parts.next().unwrap_or("");
    if parts.next().is_some() || org.is_empty() || repo.is_empty() {
        return Err(anyhow!(
            "Invalid repo name {name:?}. Expected 'org/repo' (exactly one slash)."
        ));
    }
    let valid = |s: &str| {
        !s.is_empty()
            && s.chars()
                .all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '-' | '_'))
    };
    if !valid(org) || !valid(repo) {
        return Err(anyhow!(
            "Invalid repo name {name:?}. Letters/digits/dots/hyphens/underscores only."
        ));
    }
    Ok(())
}

/// Hook fired after a successful clone or update. Receives the absolute
/// path to the cloned repo and the org/repo name. Errors are logged but
/// don't abort the activation — the repo is still registered as active.
pub type PostActivateHook = Arc<dyn Fn(&Path, &str) -> Result<()> + Send + Sync>;

/// Optional hook that returns a short agent-facing summary appended to
/// the activation result message — the "graph ready" mini-map / opening
/// steer (e.g. `"Graph ready: 9,999 Functions · 656 Classes · 31k CALLS.
/// Open with graph_overview() → cypher_query; grep = literal text only."`).
///
/// Kept separate from [`PostActivateHook`] so adding it is a non-breaking
/// addition — existing consumers that register only the build hook are
/// unaffected. Receives the repo path + name; returns `Some(text)` to
/// append (blank-line separated), or `None` for the terse default
/// message. Called after a successful activation (skipped when the build
/// hook failed).
pub type ActivationSummaryHook = Arc<dyn Fn(&Path, &str) -> Option<String> + Send + Sync>;

/// Hook fired after a successful clone/update **when revisions were
/// requested** on the activation call (`repo_management(revs=…)` /
/// `set_root_dir(revs=…)`). Receives the repo path, the `org/repo` (or
/// synthetic local) name, and the resolved revspecs in **oldest→newest**
/// order — for a `Count(n)` request the final entry is always `HEAD`, so
/// a downstream multi-rev builder can merge oldest→newest with HEAD's
/// signature winning. Set via [`Workspace::with_post_activate_revs`].
///
/// Additive by design (mirrors [`ActivationSummaryHook`]): existing
/// consumers that register only the plain [`PostActivateHook`] are
/// unaffected. When revs are requested but this hook is *not* set, the
/// plain hook runs instead (a single-rev / HEAD build) and the resolved
/// list is not reported in the activation message.
pub type PostActivateRevsHook = Arc<dyn Fn(&Path, &str, &[String]) -> Result<()> + Send + Sync>;

/// A revisions request carried by the activation tools. `Count(n)`
/// resolves to the newest `n` **stable release** tags of the repo's
/// dominant tag family (plus `HEAD`); `List(revs)` is an explicit set of
/// git revspecs used verbatim. The untagged deserialization maps a JSON
/// integer to `Count` and a JSON array of strings to `List`, so the tool
/// arg accepts `int | [str]`. Resolution happens at activate time — see
/// [`Workspace::resolve_revs`].
#[derive(Debug, Clone, PartialEq, Eq, Deserialize, Serialize, schemars::JsonSchema)]
#[serde(untagged)]
pub enum RevsRequest {
    /// Last `n` **stable** release tags of the repo's dominant tag family,
    /// ordered oldest→newest with `HEAD` appended. Tags are classified
    /// into `(prefix, version, is_prerelease)` and grouped by prefix; the
    /// family with the most stable tags wins, so on a repo with several
    /// tag families (e.g. `apache-arrow-*`, `go/v*`, `r-*`) the release
    /// line is chosen, not an unrelated package family. Prereleases (rc,
    /// alpha, beta, dev, pre, preview) and non-version tags (e.g.
    /// `r-universe-release`) are excluded. See [`Workspace::resolve_revs`]
    /// for the full selection + fallback semantics.
    Count(usize),
    /// Explicit git revspecs (tags, branches, or SHAs), used as given.
    List(Vec<String>),
}

/// Per-repo inventory entry persisted in `inventory.json`.
#[derive(Debug, Clone, Serialize, Deserialize)]
struct InventoryEntry {
    cloned_at: String,
    last_accessed: String,
    #[serde(default)]
    access_count: u64,
    #[serde(default)]
    stale: bool,
    /// HEAD SHA at the time the post-activate hook last completed
    /// successfully. Drives auto-rebuild gating: when an `update=True`
    /// call ends with `action=="current"` AND the new HEAD matches this,
    /// the post-activate hook can be skipped. `serde(default)` keeps
    /// older inventory.json files (without this field) loading cleanly.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    last_built_sha: Option<String>,
    /// The revisions request last **successfully** built for this repo,
    /// when that build was a multi-rev (`revs=`) activation via the
    /// revs-aware hook. `None` when the last build was a plain
    /// (single-rev / HEAD) activation, or the revs hook was absent (the
    /// plain-hook fallback loads HEAD only, so it records no request).
    /// Two jobs: (1) the skip gate refuses to skip a plain re-activation
    /// when the last build was multi-rev (else the tool would report a
    /// plain activation while the live product is still the rev-set);
    /// (2) `update=True` with no explicit `revs` re-applies this stored
    /// request (re-resolving it so `HEAD`/`Count(n)` re-point). Additive:
    /// `serde(default)` keeps older inventory.json files (without this
    /// field) loading cleanly.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    last_built_revs: Option<RevsRequest>,
}

// `WorkspaceKind` is re-used from the manifest module so config and
// runtime share one enum — the values mean the same thing.
pub use crate::server::manifest::WorkspaceKind;

/// Workspace runtime state. Shared across MCP request clones via Arc.
#[derive(Clone)]
pub struct Workspace {
    inner: Arc<WorkspaceInner>,
}

struct WorkspaceInner {
    kind: WorkspaceKind,
    workspace_dir: PathBuf,
    stale_after_days: u32,
    state: RwLock<WorkspaceState>,
    post_activate: Option<PostActivateHook>,
    /// Optional summary hook (see [`ActivationSummaryHook`]). Set via
    /// [`Workspace::with_activation_summary`], `None` by default.
    activation_summary: Option<ActivationSummaryHook>,
    /// Optional revs-aware hook (see [`PostActivateRevsHook`]). Set via
    /// [`Workspace::with_post_activate_revs`], `None` by default. Called
    /// in place of `post_activate` only when the activation carried a
    /// revs request AND this hook is set.
    post_activate_revs: Option<PostActivateRevsHook>,
}

#[derive(Debug, Default)]
struct WorkspaceState {
    active_repo_name: Option<String>,
    active_repo_path: Option<PathBuf>,
    /// The name whose post-activate hook **most recently ran to
    /// completion in this process** — i.e. the root whose product is
    /// currently live. Deliberately NOT persisted: `last_built_sha`
    /// records that the git repo is at the built SHA (a cross-process
    /// fact), but the hook's *product* — the consumer's in-memory graph
    /// — lives only for the process lifetime. On a fresh process this is
    /// `None`, so the first activate re-fires the hook to rehydrate even
    /// when the persisted SHA already matches HEAD.
    ///
    /// Crucially this is a **single** name, not a set of every name ever
    /// hydrated. Many consumers keep a *single* active-graph slot that
    /// each activate overwrites, so "hook fired for X at some point" does
    /// NOT imply "X's product is still live". Only re-binding the
    /// currently-active root is safe to skip; an A→B→A swap must rebuild
    /// A because B overwrote the slot. Tracking one name makes the skip
    /// gate correct for single-slot and per-name consumers alike.
    active_built_name: Option<String>,
}

impl Workspace {
    /// Open a github-flavoured workspace (clone + track flow).
    pub fn open(
        workspace_dir: PathBuf,
        stale_after_days: u32,
        post_activate: Option<PostActivateHook>,
    ) -> Result<Self> {
        if !workspace_dir.is_dir() {
            fs::create_dir_all(&workspace_dir).with_context(|| {
                format!("failed to create workspace dir {}", workspace_dir.display())
            })?;
        }
        let repos_dir = workspace_dir.join("repos");
        if !repos_dir.is_dir() {
            fs::create_dir_all(&repos_dir)
                .with_context(|| format!("failed to create repos dir {}", repos_dir.display()))?;
        }
        let ws = Self {
            inner: Arc::new(WorkspaceInner {
                kind: WorkspaceKind::Github,
                workspace_dir,
                stale_after_days,
                state: RwLock::new(WorkspaceState::default()),
                post_activate,
                activation_summary: None,
                post_activate_revs: None,
            }),
        };
        ws.reconcile_inventory()?;
        Ok(ws)
    }

    /// Open a local-directory workspace.
    ///
    /// Binds `root` as the active source root immediately and fires the
    /// post-activate hook (subject to last-built-sha gating). `inventory.json`
    /// is kept under `<root>/.mcp-workspace/` so the local mode mirrors
    /// the same gating / fingerprinting infra without polluting the
    /// user's tree with a `repos/` directory.
    pub fn open_local(root: PathBuf, post_activate: Option<PostActivateHook>) -> Result<Self> {
        if !root.is_dir() {
            anyhow::bail!(
                "local workspace root does not exist or is not a directory: {}",
                root.display()
            );
        }
        let canon_root = root
            .canonicalize()
            .with_context(|| format!("failed to canonicalize local root {}", root.display()))?;
        // Store inventory under a hidden subdir so we don't litter the
        // user's repo. The "workspace dir" for local mode IS the root.
        let inv_dir = canon_root.join(".mcp-workspace");
        if !inv_dir.is_dir() {
            fs::create_dir_all(&inv_dir).with_context(|| {
                format!("failed to create local-workspace dir {}", inv_dir.display())
            })?;
        }
        let mut state = WorkspaceState::default();
        let synthetic_name = synthesize_local_name(&canon_root);
        state.active_repo_name = Some(synthetic_name);
        state.active_repo_path = Some(canon_root.clone());
        Ok(Self {
            inner: Arc::new(WorkspaceInner {
                kind: WorkspaceKind::Local,
                workspace_dir: canon_root,
                stale_after_days: u32::MAX, // sweeping is github-only
                state: RwLock::new(state),
                post_activate,
                activation_summary: None,
                post_activate_revs: None,
            }),
        })
    }

    /// Attach an [`ActivationSummaryHook`]. Call immediately after
    /// `open`/`open_local` (before the workspace is cloned into
    /// `ServerOptions`): it mutates the still-unique inner `Arc`. Calling
    /// it after the workspace has been cloned is a no-op with a warning —
    /// the summary simply won't be attached.
    pub fn with_activation_summary(mut self, hook: ActivationSummaryHook) -> Self {
        match Arc::get_mut(&mut self.inner) {
            Some(inner) => inner.activation_summary = Some(hook),
            None => tracing::warn!(
                "with_activation_summary called after the workspace was cloned; summary not attached"
            ),
        }
        self
    }

    /// Attach a [`PostActivateRevsHook`]. Call immediately after
    /// `open`/`open_local` (before the workspace is cloned into
    /// `ServerOptions`): it mutates the still-unique inner `Arc`, exactly
    /// like [`with_activation_summary`](Self::with_activation_summary).
    /// Calling it after the workspace has been cloned is a no-op with a
    /// warning. Additive — consumers that don't set it keep the plain
    /// single-rev activation behaviour.
    pub fn with_post_activate_revs(mut self, hook: PostActivateRevsHook) -> Self {
        match Arc::get_mut(&mut self.inner) {
            Some(inner) => inner.post_activate_revs = Some(hook),
            None => tracing::warn!(
                "with_post_activate_revs called after the workspace was cloned; revs hook not attached"
            ),
        }
        self
    }

    pub fn kind(&self) -> WorkspaceKind {
        self.inner.kind
    }

    pub fn workspace_dir(&self) -> &Path {
        &self.inner.workspace_dir
    }

    pub fn repos_dir(&self) -> PathBuf {
        self.inner.workspace_dir.join("repos")
    }

    fn inventory_path(&self) -> PathBuf {
        match self.inner.kind {
            WorkspaceKind::Github => self.inner.workspace_dir.join("inventory.json"),
            WorkspaceKind::Local => self
                .inner
                .workspace_dir
                .join(".mcp-workspace")
                .join("inventory.json"),
        }
    }

    /// Active repo's full org/repo name, or None if nothing is active.
    pub fn active_repo_name(&self) -> Option<String> {
        self.inner.state.read().unwrap().active_repo_name.clone()
    }

    /// Active repo's filesystem path, or None.
    pub fn active_repo_path(&self) -> Option<PathBuf> {
        self.inner.state.read().unwrap().active_repo_path.clone()
    }

    /// Default `org/repo` for the GitHub tools when the caller passes none.
    ///
    /// Github mode: the active repo — there the inventory key *is* the
    /// `org/repo`. Local mode: the active root's `origin` remote parsed
    /// to `org/repo`, or `None` when there's no GitHub remote. Crucially
    /// it is *never* the `local/<dir>` inventory key (see
    /// [`active_repo_name`](Self::active_repo_name)), which is a
    /// filesystem-derived key, not a valid repo slug.
    pub fn default_github_repo(&self) -> Option<String> {
        match self.inner.kind {
            WorkspaceKind::Github => self.active_repo_name(),
            WorkspaceKind::Local => self.active_repo_path().and_then(|p| parse_origin_repo(&p)),
        }
    }

    // ------------------------------------------------------------------
    // Inventory management
    // ------------------------------------------------------------------

    fn load_inventory(&self) -> BTreeMap<String, InventoryEntry> {
        let path = self.inventory_path();
        let Ok(text) = fs::read_to_string(&path) else {
            return BTreeMap::new();
        };
        serde_json::from_str(&text).unwrap_or_default()
    }

    fn save_inventory(&self, inv: &BTreeMap<String, InventoryEntry>) -> Result<()> {
        let path = self.inventory_path();
        let body = serde_json::to_string_pretty(inv).context("failed to serialise inventory")?;
        fs::write(&path, body).with_context(|| format!("failed to write {}", path.display()))?;
        Ok(())
    }

    fn reconcile_inventory(&self) -> Result<()> {
        let mut inv = self.load_inventory();
        let mut on_disk: Vec<String> = Vec::new();
        if self.repos_dir().is_dir() {
            for org_entry in fs::read_dir(self.repos_dir())? {
                let Ok(org_entry) = org_entry else { continue };
                if !org_entry.path().is_dir() {
                    continue;
                }
                let org = org_entry.file_name().to_string_lossy().into_owned();
                if org.starts_with('.') {
                    continue;
                }
                for repo_entry in fs::read_dir(org_entry.path())? {
                    let Ok(repo_entry) = repo_entry else { continue };
                    if !repo_entry.path().is_dir() {
                        continue;
                    }
                    let repo = repo_entry.file_name().to_string_lossy().into_owned();
                    if repo.starts_with('.') {
                        continue;
                    }
                    let rname = format!("{org}/{repo}");
                    on_disk.push(rname.clone());
                    inv.entry(rname).or_insert_with(|| {
                        let mtime = repo_entry
                            .metadata()
                            .ok()
                            .and_then(|m| m.modified().ok())
                            .map(format_iso)
                            .unwrap_or_else(now_iso);
                        InventoryEntry {
                            cloned_at: mtime.clone(),
                            last_accessed: mtime,
                            access_count: 0,
                            stale: false,
                            last_built_sha: None,
                            last_built_revs: None,
                        }
                    });
                }
            }
        }
        for (rname, entry) in inv.iter_mut() {
            if !on_disk.contains(rname) && !entry.stale {
                entry.stale = true;
            }
        }
        self.save_inventory(&inv)?;
        Ok(())
    }

    fn bump_access(&self, name: &str, action: &str) {
        let mut inv = self.load_inventory();
        let now = now_iso();
        let entry = inv
            .entry(name.to_string())
            .or_insert_with(|| InventoryEntry {
                cloned_at: now.clone(),
                last_accessed: now.clone(),
                access_count: 0,
                stale: false,
                last_built_sha: None,
                last_built_revs: None,
            });
        entry.last_accessed = now.clone();
        entry.access_count += 1;
        entry.stale = false;
        if action == "cloned" || entry.cloned_at.is_empty() {
            entry.cloned_at = now;
        }
        let _ = self.save_inventory(&inv);
    }

    fn mark_stale(&self, name: &str) {
        let mut inv = self.load_inventory();
        if let Some(entry) = inv.get_mut(name) {
            entry.stale = true;
            let _ = self.save_inventory(&inv);
        }
    }

    fn sweep_stale(&self) -> Vec<String> {
        // Local mode has nothing to sweep — the operator owns the root.
        if matches!(self.inner.kind, WorkspaceKind::Local) {
            return Vec::new();
        }
        let mut inv = self.load_inventory();
        let cutoff = SystemTime::now()
            - std::time::Duration::from_secs(self.inner.stale_after_days as u64 * 86_400);
        let active = self.active_repo_name();
        let mut swept: Vec<String> = Vec::new();
        for (rname, entry) in inv.iter_mut() {
            if entry.stale {
                continue;
            }
            if Some(rname.as_str()) == active.as_deref() {
                continue;
            }
            let last = parse_iso(&entry.last_accessed).unwrap_or(SystemTime::UNIX_EPOCH);
            if last >= cutoff {
                continue;
            }
            let parts: Vec<&str> = rname.splitn(2, '/').collect();
            if parts.len() != 2 {
                continue;
            }
            let repo_path = self.repos_dir().join(parts[0]).join(parts[1]);
            if repo_path.exists() {
                let _ = fs::remove_dir_all(&repo_path);
            }
            entry.stale = true;
            swept.push(rname.clone());
        }
        if !swept.is_empty() {
            let _ = self.save_inventory(&inv);
            self.prune_empty_org_dirs();
        }
        swept
    }

    fn prune_empty_org_dirs(&self) {
        let Ok(entries) = fs::read_dir(self.repos_dir()) else {
            return;
        };
        for entry in entries.flatten() {
            let path = entry.path();
            if !path.is_dir() {
                continue;
            }
            if let Ok(children) = fs::read_dir(&path) {
                let real: Vec<_> = children
                    .flatten()
                    .filter(|c| !c.file_name().to_string_lossy().starts_with('.'))
                    .collect();
                if real.is_empty() {
                    let _ = fs::remove_dir_all(&path);
                }
            }
        }
    }

    // ------------------------------------------------------------------
    // Git operations
    // ------------------------------------------------------------------

    /// Clone (if missing) or fast-forward (if cloned). Returns the
    /// action label, the repo path, and the new HEAD SHA after the op.
    ///
    /// Local-mode short-circuits: there's nothing to clone or fetch.
    /// The "SHA" is a cheap content fingerprint (recursive walk of file
    /// mtimes + sizes) so the auto-rebuild gate still works.
    fn clone_or_update(&self, name: &str) -> Result<(String, PathBuf, String)> {
        if matches!(self.inner.kind, WorkspaceKind::Local) {
            // Local mode tracks the *currently bound* root, not the
            // immutable configured `workspace_dir`. `set_root_dir` writes
            // the target to `active_repo_path` before calling `activate`;
            // this read picks that up so the fingerprint and the
            // post-activate hook fire against the new root, and so the
            // subsequent `active_repo_path` write in `activate` doesn't
            // clobber the just-set target back to `workspace_dir`. Falls
            // back to `workspace_dir` only if state is unset, which
            // shouldn't happen after `open_local` seeds it.
            let root = self
                .inner
                .state
                .read()
                .unwrap()
                .active_repo_path
                .clone()
                .unwrap_or_else(|| self.inner.workspace_dir.clone());
            let prev_sha = self.last_built_sha(name);
            let fingerprint = fingerprint_dir(&root);
            let action = match prev_sha {
                Some(p) if p == fingerprint => "current",
                None => "cloned", // first activation
                Some(_) => "updated",
            };
            return Ok((action.to_string(), root, fingerprint));
        }
        let parts: Vec<&str> = name.splitn(2, '/').collect();
        let repo_path = self.repos_dir().join(parts[0]).join(parts[1]);
        if !repo_path.exists() {
            fs::create_dir_all(repo_path.parent().unwrap()).ok();
            let url = format!("https://github.com/{name}.git");
            // Treeless clone (`--filter=tree:0`): keeps the FULL commit
            // history — so `git log -S` (pickaxe) and any rev walk work —
            // while fetching tree/blob objects lazily on demand, keeping
            // the initial transfer near a shallow clone's cost. `--tags`
            // pulls all tags up front so tag-scoped rev reads
            // (`read_source rev=v1.2.3`) resolve without a follow-up fetch.
            // (Was `--depth 1`, which truncated history and broke pickaxe.)
            let out = Command::new("git")
                .args([
                    "clone",
                    "--filter=tree:0",
                    "--tags",
                    &url,
                    repo_path.to_str().unwrap(),
                ])
                .output()
                .context("failed to spawn `git clone`")?;
            if !out.status.success() {
                anyhow::bail!(
                    "git clone failed: {}",
                    String::from_utf8_lossy(&out.stderr).trim()
                );
            }
            let sha = git_rev_parse(&repo_path, "HEAD")?;
            return Ok(("cloned".to_string(), repo_path, sha));
        }

        // Fetch + check head delta. Plain `git fetch origin --tags` (no
        // `--depth 1`) so the treeless clone stays history-complete and
        // newly-pushed tags become available for rev-scoped reads; blobs
        // are still fetched lazily. FETCH_HEAD records the remote's
        // default-branch tip, so the SHA-gate below is unchanged.
        Command::new("git")
            .args(["fetch", "origin", "--tags"])
            .current_dir(&repo_path)
            .output()
            .context("git fetch failed")?;
        let local = git_rev_parse(&repo_path, "HEAD")?;
        let remote = git_rev_parse(&repo_path, "FETCH_HEAD")?;
        if local != remote {
            Command::new("git")
                .args(["reset", "--hard", "FETCH_HEAD"])
                .current_dir(&repo_path)
                .output()
                .context("git reset failed")?;
            let sha = git_rev_parse(&repo_path, "HEAD")?;
            return Ok(("updated".to_string(), repo_path, sha));
        }
        Ok(("current".to_string(), repo_path, local))
    }

    /// Resolve a [`RevsRequest`] against the git repo at `repo_path` into
    /// a concrete, ordered list of git revspecs.
    ///
    /// - `Count(n)`: the newest `n` **stable release** tags of the repo's
    ///   dominant tag family, **oldest→newest**, with `HEAD` appended as
    ///   the final (newest) rev. Selection (see [`select_family_tags`]):
    ///   every tag is classified into `(prefix, version, is_prerelease)`
    ///   by stripping a trailing version component; tags with no version
    ///   component (e.g. `r-universe-release`) are excluded. Tags are
    ///   grouped by prefix and the family with the most **stable**
    ///   (non-prerelease) tags is chosen; within it the newest `n` stable
    ///   tags (version-sorted) are taken. Prerelease markers (rc, alpha,
    ///   beta, dev, pre, preview — case-insensitive) never count as
    ///   releases. Fallback chain for degenerate repos: if the winning
    ///   family has no stable tags its prereleases are used; if no tag is
    ///   version-like at all, the raw `git tag --sort=-v:refname` top-`n`
    ///   is used. Errors only if the repo has no tags whatsoever. Fewer
    ///   than `n` matching tags is not an error — all available are used.
    /// - `List(revs)`: each revspec is validated with
    ///   `git rev-parse --verify <rev>^{commit}` and used verbatim (no
    ///   sort, no `HEAD` appended). Errors on the first unknown rev.
    ///
    /// The resolved list is deduplicated order-preserving on the label
    /// string (first occurrence wins) before being returned — see
    /// [`dedup_labels`] — so a downstream hook never receives duplicate
    /// revspecs (e.g. `revs=["HEAD","HEAD"]`). Dedup is on the label, not
    /// the resolved commit: two *different* revspecs that happen to point
    /// at the same commit are deliberately both kept, because labels are
    /// the graph-facing names a multi-rev builder attaches.
    ///
    /// A non-git `repo_path` surfaces as the `git tag` / `git rev-parse`
    /// failure with a clear message.
    fn resolve_revs(&self, repo_path: &Path, req: &RevsRequest) -> Result<Vec<String>> {
        let resolved = match req {
            RevsRequest::Count(n) => {
                let out = Command::new("git")
                    .args(["tag", "--sort=-v:refname"])
                    .current_dir(repo_path)
                    .output()
                    .context("failed to spawn `git tag`")?;
                if !out.status.success() {
                    anyhow::bail!(
                        "cannot resolve revs: `git tag` failed in {} (is it a git repo?): {}",
                        repo_path.display(),
                        String::from_utf8_lossy(&out.stderr).trim()
                    );
                }
                let tags: Vec<String> = String::from_utf8_lossy(&out.stdout)
                    .lines()
                    .map(|l| l.trim().to_string())
                    .filter(|l| !l.is_empty())
                    .collect();
                if tags.is_empty() {
                    anyhow::bail!(
                        "revs={n} requested but '{}' has no tags to resolve",
                        repo_path.display()
                    );
                }
                // Classify + pick the dominant release family's newest `n`
                // stable tags (oldest→newest). Falls back to the raw
                // version-sorted top-`n` when no tag is version-like.
                let mut chosen = select_family_tags(&tags, *n).unwrap_or_else(|| {
                    let mut raw: Vec<String> = tags.into_iter().take(*n).collect();
                    raw.reverse();
                    raw
                });
                // HEAD last so a multi-rev builder merges oldest→newest
                // with HEAD's signature winning.
                chosen.push("HEAD".to_string());
                chosen
            }
            RevsRequest::List(revs) => {
                if revs.is_empty() {
                    anyhow::bail!("revs list is empty — pass at least one revision");
                }
                for r in revs {
                    let out = Command::new("git")
                        .args([
                            "rev-parse",
                            "--verify",
                            "--quiet",
                            &format!("{r}^{{commit}}"),
                        ])
                        .current_dir(repo_path)
                        .output()
                        .context("failed to spawn `git rev-parse`")?;
                    if !out.status.success() {
                        anyhow::bail!("revision '{r}' does not exist in '{}'", repo_path.display());
                    }
                }
                revs.clone()
            }
        };
        Ok(dedup_labels(resolved))
    }

    /// Activate a repo: clone if needed, fast-forward, fire post-activate hook.
    ///
    /// Auto-rebuild gating: if `force_rebuild` is false AND no `revs` were
    /// requested AND the repo is already at the HEAD it was last built at
    /// (`action == "current"` AND `prev_built_sha == new_head`), the
    /// post-activate hook is skipped. This makes `repo_management(update=True)`
    /// cheap when upstream hasn't moved. Set `force_rebuild=true` to bypass
    /// (e.g. after upgrading the builder itself).
    ///
    /// When `revs` are requested the skip gate never applies — a
    /// revs-requested activation always fires the hook (see the gate
    /// comment below). If the revs-aware hook is set, it is called with
    /// the resolved revspecs; otherwise the plain hook runs (single-rev
    /// build) and the resolved list is not reported.
    ///
    /// On successful hook completion the new HEAD SHA is persisted to
    /// `inventory.json[name].last_built_sha`. If the hook fails the SHA
    /// is NOT recorded, so the next `update=True` re-attempts the build.
    fn activate(
        &self,
        name: &str,
        force_rebuild: bool,
        revs: Option<&RevsRequest>,
    ) -> Result<String> {
        let prev_built_sha = self.last_built_sha(name);
        let prev_built_revs = self.last_built_revs(name);
        let (action, repo_path, head_sha) = self.clone_or_update(name)?;
        // Resolve any requested revs before mutating active state, so a
        // bad request (no tags / unknown rev) returns a clean error with
        // the repo cloned-but-not-activated rather than half-bound.
        let resolved_revs = match revs {
            Some(req) => Some(self.resolve_revs(&repo_path, req)?),
            None => None,
        };
        self.bump_access(name, &action);
        let is_active_built = {
            let mut state = self.inner.state.write().unwrap();
            state.active_repo_name = Some(name.to_string());
            state.active_repo_path = Some(repo_path.clone());
            state.active_built_name.as_deref() == Some(name)
        };

        // The skip gate must be satisfied on BOTH axes: the git repo is
        // at its last-built SHA (persisted, cross-process) AND `name` is
        // the *currently active* built root in this process (in-memory).
        // Without the second axis a fresh process would inherit
        // `last_built_sha` from disk, skip the hook, and leave the
        // consumer's in-memory state (e.g. the code graph) empty —
        // activate would report success with nothing loaded. The axis
        // checks the *active* built name, not any name ever built, so an
        // A→B→A swap correctly rebuilds A: after activate(B) the live
        // slot holds B, so re-binding A must not skip (see the
        // `active_built_name` field doc).
        // Skip-gate / revs interaction: a revs-requested activation ALWAYS
        // fires the hook — the SHA-skip gate only applies to the plain
        // (no-revs) path (`resolved_revs.is_none()`). Rationale: the gate
        // keys off HEAD's SHA alone, which says nothing about which *set*
        // of revs a prior build loaded, so a rev-set request at the same
        // HEAD must rebuild. The tradeoff is that repeat `revs=` calls at
        // an unchanged HEAD re-parse every rev — acceptable for an
        // explicit multi-rev request.
        //
        // The plain path additionally requires `prev_built_revs.is_none()`
        // — a plain re-activation must NOT skip when the last build was
        // multi-rev. Without this the tool would report a plain activation
        // (and, downstream, the plain hook rebuilding a single-rev graph
        // was bypassed) while the live product is still the rev-set union.
        // A non-skip here means the plain hook runs and `record_built`
        // clears the stored request — resetting to a genuine plain graph.
        let already_built = !force_rebuild
            && resolved_revs.is_none()
            && prev_built_revs.is_none()
            && action == "current"
            && prev_built_sha.as_deref() == Some(head_sha.as_str())
            && is_active_built;
        let mut hook_skipped = false;
        // Tracks whether the revs-aware hook actually ran (revs requested
        // AND that hook set) — only then do we report the resolved list.
        let mut revs_hook_ran = false;
        let hook_ok = if already_built {
            hook_skipped = true;
            true
        } else if let (Some(resolved), Some(revs_hook)) =
            (resolved_revs.as_ref(), &self.inner.post_activate_revs)
        {
            revs_hook_ran = true;
            match revs_hook(&repo_path, name, resolved) {
                Ok(()) => true,
                Err(e) => {
                    tracing::warn!("post-activate revs hook for {name} failed: {e}");
                    false
                }
            }
        } else if let Some(hook) = &self.inner.post_activate {
            // No revs requested, or revs requested with no revs-hook set:
            // fall back to the plain single-rev (HEAD) build.
            match hook(&repo_path, name) {
                Ok(()) => true,
                Err(e) => {
                    tracing::warn!("post-activate hook for {name} failed: {e}");
                    false
                }
            }
        } else {
            // No hook configured — record the SHA so future calls can
            // see "no work to do" without consulting an empty store.
            true
        };
        if hook_ok {
            // Record the request that actually built: `Some` only when the
            // revs hook ran (a plain-hook fallback loads HEAD only, and a
            // cheap-skip / no-hook path built nothing new), so a plain
            // build clears any previously-stored request.
            let built_revs = if revs_hook_ran { revs } else { None };
            self.record_built(name, &head_sha, built_revs);
        }
        // Mark this name the currently-active built root only when the
        // hook actually ran this process (not on the cheap-skip path,
        // where it is already the active built name). A no-op "no hook
        // configured" activation also counts: there is no per-process
        // product to lose, so a future same-root skip is safe. This
        // *overwrites* any prior name — modelling that each activate
        // replaces the live product — so the next swap back rebuilds.
        if hook_ok && !hook_skipped {
            self.inner.state.write().unwrap().active_built_name = Some(name.to_string());
        }
        let verb = match action.as_str() {
            "cloned" => "Cloned",
            "updated" => "Updated",
            "current" => "Activated (already up to date)",
            other => other,
        };
        let suffix = if hook_skipped {
            " [build skipped: HEAD matches last-built SHA]"
        } else {
            ""
        };
        let mut base = format!("{verb} '{name}' at {}.{suffix}", repo_path.display());
        // Name the resolved revisions on their own line so agents see
        // exactly what got loaded. Only when the revs-hook actually ran
        // (revs requested AND hook set AND it succeeded) — a fallback to
        // the plain hook loads HEAD only, so claiming a rev-set would lie.
        if revs_hook_ran && hook_ok {
            if let Some(resolved) = &resolved_revs {
                base.push_str(&format!("\nrevs: {}", resolved.join(", ")));
            }
        }
        // Append the consumer's opening-steer mini-map, if configured.
        // Fired on any successful activation (fresh build or cheap-skip —
        // in both cases the in-memory product is live this process); the
        // hook recomputes the summary from that live state. Skipped only
        // when the build hook itself failed.
        let summary = if hook_ok {
            self.inner
                .activation_summary
                .as_ref()
                .and_then(|h| h(&repo_path, name))
        } else {
            None
        };
        Ok(match summary {
            Some(s) if !s.is_empty() => format!("{base}\n\n{s}"),
            _ => base,
        })
    }

    /// Record the outcome of a successful build: the HEAD SHA plus the
    /// revisions request that produced it (`Some` only for a multi-rev
    /// build via the revs hook; `None` for a plain / HEAD-only build,
    /// which *clears* any previously-stored request). Called only on hook
    /// success — a failed build records nothing, so the next `update` retries.
    fn record_built(&self, name: &str, sha: &str, revs: Option<&RevsRequest>) {
        let mut inv = self.load_inventory();
        if let Some(entry) = inv.get_mut(name) {
            entry.last_built_sha = Some(sha.to_string());
            entry.last_built_revs = revs.cloned();
            let _ = self.save_inventory(&inv);
        }
    }

    /// Read the SHA recorded after the last successful post-activate hook
    /// for the named repo. `None` if the repo was never built (or the
    /// hook last failed). Useful for downstream consumers gating
    /// "is the active graph up to date with the repo HEAD?" checks.
    pub fn last_built_sha(&self, name: &str) -> Option<String> {
        self.load_inventory()
            .get(name)
            .and_then(|e| e.last_built_sha.clone())
    }

    /// Read the revisions request last successfully built for the named
    /// repo — `Some` when the last build was multi-rev (`revs=`), `None`
    /// for a plain / HEAD-only build or a never-built repo. Drives the
    /// rev-set-aware skip gate and the `update`-preserves-rev-set path.
    pub fn last_built_revs(&self, name: &str) -> Option<RevsRequest> {
        self.load_inventory()
            .get(name)
            .and_then(|e| e.last_built_revs.clone())
    }

    fn delete(&self, name: &str) -> Result<String> {
        let parts: Vec<&str> = name.splitn(2, '/').collect();
        if parts.len() != 2 {
            anyhow::bail!("Invalid repo name");
        }
        let repo_path = self.repos_dir().join(parts[0]).join(parts[1]);
        let mut deleted = Vec::new();
        if repo_path.exists() {
            fs::remove_dir_all(&repo_path).context("failed to remove repo dir")?;
            deleted.push("repo");
        }
        self.mark_stale(name);
        self.prune_empty_org_dirs();
        if deleted.is_empty() {
            return Ok(format!("Nothing to delete — '{name}' not found."));
        }
        let mut state = self.inner.state.write().unwrap();
        if state.active_repo_name.as_deref() == Some(name) {
            state.active_repo_name = None;
            state.active_repo_path = None;
            return Ok(format!(
                "Deleted {}. Active repo cleared.",
                deleted.join(", ")
            ));
        }
        Ok(format!("Deleted {}.", deleted.join(", ")))
    }

    fn list(&self) -> String {
        let inv = self.load_inventory();
        if inv.is_empty() {
            return "No repos cloned yet. Call repo_management('org/repo') to clone one."
                .to_string();
        }
        let active = self.active_repo_name();
        let mut live: Vec<String> = Vec::new();
        let mut stale_lines: Vec<String> = Vec::new();
        for (rname, entry) in &inv {
            let marker = if Some(rname.as_str()) == active.as_deref() {
                " [active]"
            } else {
                ""
            };
            let access = format!(
                "{} access{}, last {}",
                entry.access_count,
                if entry.access_count == 1 { "" } else { "es" },
                relative_time(&entry.last_accessed)
            );
            if entry.stale {
                stale_lines.push(format!(
                    "  {rname}  [STALE — re-fetch with repo_management('{rname}')]  ({access})"
                ));
            } else {
                live.push(format!("  {rname}{marker}  ({access})"));
            }
        }
        let mut out = String::new();
        if !live.is_empty() {
            out.push_str(&format!(
                "{} live repo(s):\n{}",
                live.len(),
                live.join("\n")
            ));
        }
        if !stale_lines.is_empty() {
            if !out.is_empty() {
                out.push_str("\n\n");
            }
            out.push_str(&format!(
                "{} stale repo(s):\n{}",
                stale_lines.len(),
                stale_lines.join("\n")
            ));
        }
        out
    }

    /// Public entry for the `repo_management` MCP tool.
    ///
    /// - `name`: `org/repo` to activate (None = list / refresh mode).
    /// - `delete`: remove the named repo + inventory entry. Github only.
    /// - `update`: refresh the active repo (auto-rebuild gated).
    /// - `force_rebuild`: with `update=true` (or initial activation),
    ///   re-run the post-activate hook even when the HEAD SHA matches
    ///   `last_built_sha`. Useful after the builder itself has been
    ///   upgraded.
    ///
    /// Local mode behaviour: `name` and `delete` are rejected; pass
    /// `update=true` (or no args after the initial activation) to
    /// re-fingerprint the root and rebuild if anything changed.
    pub fn repo_management(
        &self,
        name: Option<&str>,
        delete: bool,
        update: bool,
        force_rebuild: bool,
        revs: Option<&RevsRequest>,
    ) -> String {
        // Local mode: most github-only semantics are nonsensical here.
        if matches!(self.inner.kind, WorkspaceKind::Local) {
            if name.is_some() {
                return "Local-workspace mode does not accept a repo name. Use `set_root_dir(path)` \
                        to switch the active root, or pass `update=true` / `force_rebuild=true` \
                        to rebuild against the current root."
                    .to_string();
            }
            if delete {
                return "Local-workspace mode does not support `delete`. The root is owned by the \
                        operator; remove it manually."
                    .to_string();
            }
            let active = match self.active_repo_name() {
                Some(n) => n,
                None => return "No active local root.".to_string(),
            };
            // `update`: re-fingerprint and rebuild if anything changed.
            // `force_rebuild`: rebuild even when the fingerprint matches.
            // Either flag (or neither — initial bind path) routes through
            // `activate`; `activate` itself consults the gate using the
            // force flag plus the SHA comparison.
            let _ = update; // explicit: update is implicit in local mode
                            // A local `repo_management` call is always a refresh of the
                            // bound root, so when no explicit `revs` are passed re-apply
                            // the stored rev-set (if the last build was multi-rev) — a
                            // bare refresh must not silently collapse a rev-set graph to
                            // HEAD-only. Re-`set_root_dir` (which passes `revs` verbatim)
                            // is the way to reset back to a plain single-rev build.
            let effective = match revs {
                Some(r) => Some(r.clone()),
                None => self.last_built_revs(&active),
            };
            return self
                .activate(&active, force_rebuild, effective.as_ref())
                .unwrap_or_else(|e| format!("rebuild failed: {e}"));
        }

        let swept = self.sweep_stale();
        let prefix = if swept.is_empty() {
            String::new()
        } else {
            format!(
                "[Swept {} idle repo(s) (>{}d): {}]\n\n",
                swept.len(),
                self.inner.stale_after_days,
                swept.join(", ")
            )
        };

        if name.is_none() && !update {
            return prefix + &self.list();
        }

        if update {
            let Some(active) = self.active_repo_name() else {
                return prefix + "No active repository. Call repo_management('org/repo') first.";
            };
            // `update=True` refreshes the active repo. When no explicit
            // `revs` are passed, re-apply the stored rev-set (if the last
            // build was multi-rev) so a bare `update` after HEAD moves
            // re-resolves and rebuilds the SAME rev-set rather than
            // collapsing it to a single-rev HEAD build. An explicit `revs`
            // argument overrides; a plain re-activation (name path, not
            // `update`) still resets to plain.
            let effective = match revs {
                Some(r) => Some(r.clone()),
                None => self.last_built_revs(&active),
            };
            return prefix
                + &self
                    .activate(&active, force_rebuild, effective.as_ref())
                    .unwrap_or_else(|e| format!("update failed: {e}"));
        }

        let Some(name) = name else {
            return prefix + "Provide a repo name (e.g. repo_management('org/repo')).";
        };
        if let Err(e) = validate_repo_name(name) {
            return prefix + &e.to_string();
        }
        if delete {
            return prefix
                + &self
                    .delete(name)
                    .unwrap_or_else(|e| format!("delete failed: {e}"));
        }
        prefix
            + &self
                .activate(name, force_rebuild, revs)
                .unwrap_or_else(|e| format!("activate failed: {e}"))
    }

    /// Swap the active root (local mode only). Re-fires the post-activate
    /// hook against the new root. Errors if the workspace is github-flavoured.
    ///
    /// `revs` (optional): resolve revisions against the new root (which
    /// must be a git repo) and fire the revs-aware hook — see
    /// [`activate`](Self::activate) / [`RevsRequest`].
    pub fn set_root_dir(&self, new_root: &Path, revs: Option<&RevsRequest>) -> String {
        if !matches!(self.inner.kind, WorkspaceKind::Local) {
            return "set_root_dir is only valid in local-workspace mode.".to_string();
        }
        if !new_root.is_dir() {
            return format!(
                "Path does not exist or is not a directory: {}",
                new_root.display()
            );
        }
        let canon = match new_root.canonicalize() {
            Ok(p) => p,
            Err(e) => return format!("canonicalize failed: {e}"),
        };
        let synthetic = synthesize_local_name(&canon);
        {
            let mut state = self.inner.state.write().unwrap();
            state.active_repo_name = Some(synthetic.clone());
            state.active_repo_path = Some(canon.clone());
        }
        // Note: the WorkspaceInner.workspace_dir field is the path the
        // inventory is stored under. We keep the *original* one (from
        // open_local) so the inventory survives across root swaps.
        self.activate(&synthetic, false, revs)
            .unwrap_or_else(|e| format!("set_root_dir failed: {e}"))
    }
}

/// Deduplicate a resolved revspec list order-preserving, first
/// occurrence wins. Dedup is on the **label** string, not the resolved
/// commit: a downstream multi-rev builder attaches each label as a
/// graph-facing name, so two *different* labels pointing at the same
/// commit are deliberately kept — only literal repeats (e.g. a `HEAD`
/// that appears twice) collapse.
fn dedup_labels(revs: Vec<String>) -> Vec<String> {
    let mut seen = std::collections::HashSet::new();
    revs.into_iter()
        .filter(|r| seen.insert(r.clone()))
        .collect()
}

/// Prerelease markers recognised in a tag's trailing suffix
/// (case-insensitive, with an optional `-`/`.`/`_` separator). A tag
/// whose version is followed by one of these is never treated as a
/// stable release.
const PRERELEASE_MARKERS: &[&str] = &["rc", "alpha", "beta", "dev", "pre", "preview"];

/// A git tag decomposed into its release family `prefix`, numeric
/// `version` components, and whether it carries a prerelease marker.
/// Produced by [`classify_tag`]; consumed by [`select_family_tags`].
#[derive(Debug, Clone, PartialEq, Eq)]
struct ClassifiedTag {
    raw: String,
    prefix: String,
    version: Vec<u64>,
    is_prerelease: bool,
}

/// Classify a single tag into `(prefix, version, is_prerelease)` by
/// locating its trailing version component.
///
/// The version is the *first* `DIGITS(.DIGITS)*` run whose remainder is
/// empty or a recognised prerelease suffix; everything before it is the
/// family `prefix`. Taking the first *cleanly-parsing* run resolves both
/// tricky shapes: `arrow2-0.17.0` skips the `2` in `arrow2` (its
/// remainder `-0.17.0` isn't a recognised suffix, so that run is
/// rejected) and lands on `0.17.0`; while `v3.0.0-rc1` stops at `3.0.0`
/// (with `-rc1` recognised as a prerelease) rather than mistaking the
/// trailing `1` of `rc1` for a version. Returns `None` when the tag has
/// no version-like component at all (e.g. `r-universe-release`), so such
/// tags are excluded from family selection.
fn classify_tag(tag: &str) -> Option<ClassifiedTag> {
    let bytes = tag.as_bytes();
    for i in 0..bytes.len() {
        if !bytes[i].is_ascii_digit() {
            continue;
        }
        // Only consider the *start* of a digit run as a version start.
        if i > 0 && bytes[i - 1].is_ascii_digit() {
            continue;
        }
        if let Some((version, is_prerelease)) = parse_version_at(&tag[i..]) {
            return Some(ClassifiedTag {
                raw: tag.to_string(),
                prefix: tag[..i].to_string(),
                version,
                is_prerelease,
            });
        }
    }
    None
}

/// Parse `s` as `DIGITS(.DIGITS)*` optionally followed by a recognised
/// prerelease suffix. Returns the numeric components and whether a
/// prerelease marker follows. `None` if `s` doesn't start with a digit,
/// or carries an *unrecognised* trailing suffix (so the caller rejects
/// this candidate start and tries an earlier digit run).
fn parse_version_at(s: &str) -> Option<(Vec<u64>, bool)> {
    let bytes = s.as_bytes();
    let mut nums: Vec<u64> = Vec::new();
    let mut idx = 0usize;
    loop {
        let start = idx;
        while idx < bytes.len() && bytes[idx].is_ascii_digit() {
            idx += 1;
        }
        if idx == start {
            return None; // expected digits (leading, or after a '.')
        }
        nums.push(s[start..idx].parse().ok()?);
        // Continue only when a '.' is followed by another digit.
        if idx + 1 < bytes.len() && bytes[idx] == b'.' && bytes[idx + 1].is_ascii_digit() {
            idx += 1;
            continue;
        }
        break;
    }
    let rest = &s[idx..];
    if rest.is_empty() {
        return Some((nums, false));
    }
    // A single optional separator, then a recognised prerelease marker.
    let after_sep = rest
        .strip_prefix(|c| c == '-' || c == '.' || c == '_')
        .unwrap_or(rest);
    let lower = after_sep.to_ascii_lowercase();
    if PRERELEASE_MARKERS.iter().any(|m| lower.starts_with(m)) {
        Some((nums, true))
    } else {
        None
    }
}

/// From a repo's tag list, choose the dominant **release family** and
/// return its newest `n` tags **oldest→newest** (HEAD is appended by the
/// caller, not here). Returns `None` when no tag is version-like, so the
/// caller can fall back to the raw version-sorted top-`n`.
///
/// Tags are classified ([`classify_tag`]) and grouped by prefix. The
/// family with the most **stable** (non-prerelease) tags wins; if no
/// family has any stable tag, the family with the most tags overall wins
/// and its prereleases are used. Within the winning family the newest
/// `n` tags in the applicable pool (stable if any exist, else
/// prerelease) are taken by descending version, then reversed to
/// oldest→newest. Deterministic: grouping iterates prefixes in sorted
/// order and the version/`raw` sort is total, so a given tag set always
/// resolves to the same list. Family ties are broken toward the
/// lexicographically-greatest prefix.
fn select_family_tags(tags: &[String], n: usize) -> Option<Vec<String>> {
    let classified: Vec<ClassifiedTag> = tags.iter().filter_map(|t| classify_tag(t)).collect();
    if classified.is_empty() {
        return None;
    }
    // Group by family prefix (BTreeMap → deterministic prefix order).
    let mut families: BTreeMap<String, Vec<&ClassifiedTag>> = BTreeMap::new();
    for c in &classified {
        families.entry(c.prefix.clone()).or_default().push(c);
    }
    let stable_count = |v: &Vec<&ClassifiedTag>| v.iter().filter(|c| !c.is_prerelease).count();
    let any_stable = families.values().any(|v| stable_count(v) > 0);
    // Prefer the family with the most stable tags; when nothing is
    // stable anywhere, prefer the family with the most tags overall.
    // `max_by` returns the last maximum, and BTreeMap yields ascending
    // prefixes, so ties resolve to the greatest prefix — deterministic.
    let chosen = families.values().max_by(|a, b| {
        if any_stable {
            stable_count(a).cmp(&stable_count(b))
        } else {
            a.len().cmp(&b.len())
        }
    })?;
    let mut pool: Vec<&ClassifiedTag> = if any_stable {
        chosen
            .iter()
            .copied()
            .filter(|c| !c.is_prerelease)
            .collect()
    } else {
        chosen.to_vec()
    };
    // Newest first: descending version, then descending raw for a total,
    // stable order on identical versions.
    pool.sort_by(|a, b| b.version.cmp(&a.version).then_with(|| b.raw.cmp(&a.raw)));
    let mut newest: Vec<String> = pool.into_iter().take(n).map(|c| c.raw.clone()).collect();
    newest.reverse(); // oldest→newest
    Some(newest)
}

/// Synthesise a stable "repo name" for a local workspace from its path.
/// Used as the inventory key so the same gating + persistence code paths
/// that github mode uses can apply to local mode unchanged.
fn synthesize_local_name(root: &Path) -> String {
    let name = root
        .file_name()
        .map(|s| s.to_string_lossy().into_owned())
        .unwrap_or_else(|| "local".to_string());
    format!("local/{name}")
}

/// Parse the `org/repo` slug from a local checkout's `origin` remote.
///
/// Shells out to `git -C <root> remote get-url origin` and parses both
/// canonical GitHub remote forms, stripping the trailing `.git`:
///   - `git@github.com:kkollsga/kglite.git`     → `kkollsga/kglite`
///   - `https://github.com/kkollsga/kglite.git` → `kkollsga/kglite`
///
/// Returns `None` for a non-git directory, a missing `origin` remote, or
/// a non-GitHub remote — so the GitHub tools fall back to their existing
/// empty-default path (ask the caller for `repo_name`).
fn parse_origin_repo(root: &Path) -> Option<String> {
    let out = Command::new("git")
        .arg("-C")
        .arg(root)
        .args(["remote", "get-url", "origin"])
        .output()
        .ok()?;
    if !out.status.success() {
        return None;
    }
    let url = String::from_utf8(out.stdout).ok()?;
    parse_github_remote(url.trim())
}

/// Pure-string half of [`parse_origin_repo`]: turn a GitHub remote URL
/// into `org/repo`, or `None` if it isn't a recognisable GitHub remote.
fn parse_github_remote(url: &str) -> Option<String> {
    // Accept both SSH (`git@github.com:org/repo`) and HTTPS
    // (`https://github.com/org/repo`) forms; everything after the host
    // separator is the path.
    let path = url
        .strip_prefix("git@github.com:")
        .or_else(|| url.strip_prefix("https://github.com/"))
        .or_else(|| url.strip_prefix("http://github.com/"))
        .or_else(|| url.strip_prefix("ssh://git@github.com/"))?;
    let path = path.strip_suffix(".git").unwrap_or(path);
    let path = path.trim_end_matches('/');
    // Must be exactly `org/repo` — both segments non-empty, one slash.
    let mut parts = path.split('/');
    let org = parts.next().filter(|s| !s.is_empty())?;
    let repo = parts.next().filter(|s| !s.is_empty())?;
    if parts.next().is_some() {
        return None;
    }
    Some(format!("{org}/{repo}"))
}

/// Cheap recursive content fingerprint of a directory tree. Walks files
/// (respecting common ignore patterns) and folds `(path, mtime, len)`
/// into a 64-bit hash, then hex-formats it. Good enough to detect
/// "did anything change?" for auto-rebuild gating — not cryptographic.
fn fingerprint_dir(root: &Path) -> String {
    use std::hash::{Hash, Hasher};
    let mut hasher = std::collections::hash_map::DefaultHasher::new();
    let walker = ignore::WalkBuilder::new(root)
        .standard_filters(true)
        .hidden(true)
        .git_ignore(true)
        .build();
    for entry in walker.flatten() {
        if !entry.path().is_file() {
            continue;
        }
        let Ok(meta) = entry.metadata() else { continue };
        let mtime = meta
            .modified()
            .ok()
            .and_then(|t| t.duration_since(SystemTime::UNIX_EPOCH).ok())
            .map(|d| d.as_secs())
            .unwrap_or(0);
        entry.path().to_string_lossy().hash(&mut hasher);
        mtime.hash(&mut hasher);
        meta.len().hash(&mut hasher);
    }
    format!("local-{:016x}", hasher.finish())
}

fn git_rev_parse(repo_path: &Path, refspec: &str) -> Result<String> {
    let out = Command::new("git")
        .args(["rev-parse", refspec])
        .current_dir(repo_path)
        .output()
        .context("git rev-parse failed")?;
    Ok(String::from_utf8_lossy(&out.stdout).trim().to_string())
}

fn now_iso() -> String {
    format_iso(SystemTime::now())
}

fn format_iso(t: SystemTime) -> String {
    let secs = t
        .duration_since(SystemTime::UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0);
    // Lightweight RFC3339-ish formatter. Drop sub-second precision; matches Python isoformat(timespec=seconds).
    chrono_lite::format_secs(secs)
}

fn parse_iso(s: &str) -> Option<SystemTime> {
    let secs = chrono_lite::parse_secs(s)?;
    SystemTime::UNIX_EPOCH.checked_add(std::time::Duration::from_secs(secs))
}

fn relative_time(iso: &str) -> String {
    let Some(t) = parse_iso(iso) else {
        return "unknown".to_string();
    };
    let now = SystemTime::now();
    let delta = now.duration_since(t).unwrap_or_default().as_secs();
    if delta < 3600 {
        "just now".to_string()
    } else if delta < 86_400 {
        format!("{}h ago", delta / 3600)
    } else {
        format!("{}d ago", delta / 86_400)
    }
}

/// Tiny self-contained ISO-8601 (seconds-precision) formatter so we
/// don't pull in `chrono` for a handful of timestamps.
mod chrono_lite {
    pub fn format_secs(secs: u64) -> String {
        // Civil-from-days algorithm (Howard Hinnant). Output: YYYY-MM-DDTHH:MM:SS.
        let days = (secs / 86_400) as i64;
        let time = secs % 86_400;
        let (y, mo, d) = days_to_civil(days + 719_468);
        let h = time / 3600;
        let m = (time / 60) % 60;
        let s = time % 60;
        format!("{y:04}-{mo:02}-{d:02}T{h:02}:{m:02}:{s:02}")
    }

    pub fn parse_secs(s: &str) -> Option<u64> {
        // Accept "YYYY-MM-DDTHH:MM:SS" (no zone) — same shape as format_secs output
        // and Python's datetime.isoformat(timespec="seconds").
        let bytes = s.as_bytes();
        if bytes.len() < 19 {
            return None;
        }
        let y: i64 = s.get(0..4)?.parse().ok()?;
        let mo: u32 = s.get(5..7)?.parse().ok()?;
        let d: u32 = s.get(8..10)?.parse().ok()?;
        let h: u64 = s.get(11..13)?.parse().ok()?;
        let m: u64 = s.get(14..16)?.parse().ok()?;
        let sc: u64 = s.get(17..19)?.parse().ok()?;
        let days = civil_to_days(y, mo, d) - 719_468;
        Some((days * 86_400) as u64 + h * 3600 + m * 60 + sc)
    }

    fn days_to_civil(z: i64) -> (i64, u32, u32) {
        let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
        let doe = (z - era * 146_097) as u64;
        let yoe = (doe - doe / 1460 + doe / 36_524 - doe / 146_096) / 365;
        let y = (yoe as i64) + era * 400;
        let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
        let mp = (5 * doy + 2) / 153;
        let d = (doy - (153 * mp + 2) / 5 + 1) as u32;
        let m = (if mp < 10 { mp + 3 } else { mp - 9 }) as u32;
        let y = if m <= 2 { y + 1 } else { y };
        (y, m, d)
    }

    fn civil_to_days(y: i64, m: u32, d: u32) -> i64 {
        let y = if m <= 2 { y - 1 } else { y };
        let era = if y >= 0 { y } else { y - 399 } / 400;
        let yoe = (y - era * 400) as u64;
        let doy = (153 * (if m > 2 { m - 3 } else { m + 9 }) as u64 + 2) / 5 + d as u64 - 1;
        let doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;
        era * 146_097 + doe as i64
    }
}

// silences unused-import-when-helper-only-via-json! macro check.
#[allow(dead_code)]
fn _json_keepalive() {
    let _ = json!({});
}

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

    #[test]
    fn validates_repo_names() {
        assert!(validate_repo_name("pydata/xarray").is_ok());
        assert!(validate_repo_name("my-org.x/repo_v2").is_ok());
        assert!(validate_repo_name("xarray").is_err());
        assert!(validate_repo_name("a/b/c").is_err());
        assert!(validate_repo_name("foo/bar; rm -rf").is_err());
    }

    #[test]
    fn open_creates_layout() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        assert!(ws.repos_dir().is_dir());
    }

    #[test]
    fn empty_list() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        let out = ws.repo_management(None, false, false, false, None);
        assert!(out.contains("No repos cloned yet"));
    }

    #[test]
    fn invalid_repo_name_rejected() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        let out = ws.repo_management(Some("bad name with spaces"), false, false, false, None);
        assert!(out.contains("Invalid repo name"));
    }

    #[test]
    fn delete_unknown() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        let out = ws.repo_management(Some("nope/none"), true, false, false, None);
        assert!(out.contains("Nothing to delete"));
    }

    #[test]
    fn iso_round_trip() {
        let now = SystemTime::now()
            .duration_since(SystemTime::UNIX_EPOCH)
            .unwrap()
            .as_secs();
        let s = chrono_lite::format_secs(now);
        let back = chrono_lite::parse_secs(&s).unwrap();
        assert_eq!(now, back);
    }

    #[test]
    fn last_built_sha_round_trip() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        // Seed an inventory entry directly (clone_or_update needs git).
        ws.bump_access("acme/widgets", "cloned");
        assert_eq!(ws.last_built_sha("acme/widgets"), None);
        ws.record_built("acme/widgets", "abc1234deadbeef", None);
        assert_eq!(
            ws.last_built_sha("acme/widgets").as_deref(),
            Some("abc1234deadbeef")
        );
        // Survives an Workspace::open re-read (proves persistence).
        let ws2 = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        assert_eq!(
            ws2.last_built_sha("acme/widgets").as_deref(),
            Some("abc1234deadbeef")
        );
    }

    #[test]
    fn inventory_loads_legacy_entries_without_sha_field() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        // Hand-craft an old-style inventory.json without `last_built_sha`.
        let legacy = r#"{
            "old/repo": {
                "cloned_at": "2024-01-01T00:00:00",
                "last_accessed": "2024-01-01T00:00:00",
                "access_count": 5,
                "stale": false
            }
        }"#;
        std::fs::write(dir.path().join("inventory.json"), legacy).unwrap();
        // Re-open and confirm graceful read.
        let ws2 = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        assert_eq!(ws2.last_built_sha("old/repo"), None);
        let _ = ws;
    }

    #[test]
    fn auto_rebuild_gate_skips_when_sha_matches() {
        use std::sync::atomic::{AtomicUsize, Ordering};
        let dir = tempfile::tempdir().unwrap();
        let calls = Arc::new(AtomicUsize::new(0));
        let calls_h = calls.clone();
        let hook: PostActivateHook = Arc::new(move |_path, _name| {
            calls_h.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        // Build a workspace pointing at a tempdir with a fake repo dir,
        // then simulate consecutive activates. We can't drive clone_or_update
        // without git, so test the gating directly by tracking the SHA
        // record-then-re-record case via Workspace::record_built +
        // last_built_sha — the same predicate `activate` uses.
        let ws = Workspace::open(dir.path().to_path_buf(), 7, Some(hook)).unwrap();
        // Seed inventory entry + initial sha record.
        ws.bump_access("acme/widgets", "cloned");
        ws.record_built("acme/widgets", "sha_one", None);
        assert_eq!(
            ws.last_built_sha("acme/widgets").as_deref(),
            Some("sha_one")
        );
        // Repeated record with the same value is idempotent (gating
        // logic uses last_built_sha as the source of truth).
        ws.record_built("acme/widgets", "sha_one", None);
        assert_eq!(
            ws.last_built_sha("acme/widgets").as_deref(),
            Some("sha_one")
        );
        // No hook calls have been driven directly — this test exercises
        // the persistence path that the gate consults.
        assert_eq!(calls.load(Ordering::SeqCst), 0);
    }

    #[test]
    fn local_workspace_binds_root_immediately() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open_local(dir.path().to_path_buf(), None).unwrap();
        assert_eq!(ws.kind(), WorkspaceKind::Local);
        assert!(ws.active_repo_path().is_some());
        assert!(ws.active_repo_name().unwrap().starts_with("local/"));
    }

    #[test]
    fn local_workspace_rejects_github_ops() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open_local(dir.path().to_path_buf(), None).unwrap();
        let out = ws.repo_management(Some("acme/widgets"), false, false, false, None);
        assert!(out.contains("does not accept a repo name"));
        let out = ws.repo_management(None, true, false, false, None);
        assert!(out.contains("does not support `delete`"));
    }

    #[test]
    fn local_workspace_update_rebuilds() {
        use std::sync::atomic::{AtomicUsize, Ordering};
        let dir = tempfile::tempdir().unwrap();
        // Drop a file so the fingerprint has something to hash.
        std::fs::write(dir.path().join("x.txt"), b"hi").unwrap();
        let calls = Arc::new(AtomicUsize::new(0));
        let calls_h = calls.clone();
        let hook: PostActivateHook = Arc::new(move |_p, _n| {
            calls_h.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        let ws = Workspace::open_local(dir.path().to_path_buf(), Some(hook)).unwrap();
        // First update: nothing built yet → hook fires.
        let _ = ws.repo_management(None, false, true, false, None);
        assert_eq!(calls.load(Ordering::SeqCst), 1);
        // Second update without changes → SHA matches → hook skipped.
        let out = ws.repo_management(None, false, true, false, None);
        assert_eq!(
            calls.load(Ordering::SeqCst),
            1,
            "auto-rebuild gate must skip"
        );
        assert!(out.contains("build skipped"));
    }

    #[test]
    fn parses_github_remote_forms() {
        assert_eq!(
            parse_github_remote("git@github.com:kkollsga/kglite.git").as_deref(),
            Some("kkollsga/kglite")
        );
        assert_eq!(
            parse_github_remote("https://github.com/kkollsga/kglite.git").as_deref(),
            Some("kkollsga/kglite")
        );
        // No .git suffix, trailing slash.
        assert_eq!(
            parse_github_remote("https://github.com/acme/widget/").as_deref(),
            Some("acme/widget")
        );
        assert_eq!(
            parse_github_remote("ssh://git@github.com/acme/widget.git").as_deref(),
            Some("acme/widget")
        );
        // Non-github / malformed → None.
        assert_eq!(
            parse_github_remote("https://gitlab.com/acme/widget.git"),
            None
        );
        assert_eq!(parse_github_remote("git@github.com:acme.git"), None);
        assert_eq!(parse_github_remote("not a url"), None);
    }

    #[test]
    fn local_default_github_repo_uses_origin_remote() {
        let dir = tempfile::tempdir().unwrap();
        let root = dir.path();
        // Stand up a real git repo with a faked origin so default_github_repo
        // exercises the actual `git remote get-url` path.
        let git = |args: &[&str]| {
            Command::new("git")
                .arg("-C")
                .arg(root)
                .args(args)
                .output()
                .unwrap()
        };
        if !git(&["init"]).status.success() {
            // git unavailable in this environment — skip rather than fail.
            return;
        }
        git(&[
            "remote",
            "add",
            "origin",
            "https://github.com/acme/widget.git",
        ]);
        let ws = Workspace::open_local(root.to_path_buf(), None).unwrap();
        assert_eq!(
            ws.default_github_repo().as_deref(),
            Some("acme/widget"),
            "local default repo must come from the origin remote, not the inventory key"
        );
        // The inventory key remains the synthetic local name.
        assert!(ws.active_repo_name().unwrap().starts_with("local/"));
    }

    #[test]
    fn local_default_github_repo_none_without_remote() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open_local(dir.path().to_path_buf(), None).unwrap();
        // No git remote → None, and crucially NOT Some("local/<dir>").
        let def = ws.default_github_repo();
        assert!(
            def.is_none(),
            "expected None for a non-git local root, got {def:?}"
        );
    }

    #[test]
    fn set_root_dir_only_in_local_mode() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        let out = ws.set_root_dir(dir.path(), None);
        assert!(out.contains("only valid in local-workspace"));
    }

    #[test]
    fn update_with_no_active_repo() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        let out = ws.repo_management(None, false, true, false, None);
        assert!(out.contains("No active repository"));
    }

    #[test]
    fn set_root_dir_updates_active_path() {
        let dir = tempfile::tempdir().unwrap();
        let child = dir.path().join("child");
        std::fs::create_dir_all(&child).unwrap();
        let ws = Workspace::open_local(dir.path().to_path_buf(), None).unwrap();
        let _ = ws.set_root_dir(&child, None);
        assert_eq!(
            ws.active_repo_path().unwrap(),
            child.canonicalize().unwrap(),
            "set_root_dir didn't update active_repo_path"
        );
    }

    #[test]
    fn set_root_dir_post_activate_fires_against_new_root() {
        let dir = tempfile::tempdir().unwrap();
        let child = dir.path().join("child");
        std::fs::create_dir_all(&child).unwrap();
        std::fs::write(child.join("a.txt"), b"hi").unwrap();
        let seen_path: Arc<std::sync::Mutex<Option<PathBuf>>> = Arc::new(Default::default());
        let seen = seen_path.clone();
        let hook: PostActivateHook = Arc::new(move |p, _n| {
            *seen.lock().unwrap() = Some(p.to_path_buf());
            Ok(())
        });
        let ws = Workspace::open_local(dir.path().to_path_buf(), Some(hook)).unwrap();
        let _ = ws.set_root_dir(&child, None);
        assert_eq!(
            seen_path.lock().unwrap().clone().unwrap(),
            child.canonicalize().unwrap(),
            "post_activate hook saw the wrong root after set_root_dir"
        );
    }

    #[test]
    fn activation_summary_appended_to_activate_message() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("a.txt"), b"x").unwrap();
        let summary: ActivationSummaryHook =
            Arc::new(|_p, _n| Some("Graph ready: 3 Functions.".to_string()));
        let ws = Workspace::open_local(dir.path().to_path_buf(), None)
            .unwrap()
            .with_activation_summary(summary);
        let out = ws.repo_management(None, false, true, false, None);
        assert!(
            out.contains("Graph ready: 3 Functions."),
            "activation message should include the summary; got: {out}"
        );
    }

    #[test]
    fn activation_summary_absent_when_not_configured() {
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("a.txt"), b"x").unwrap();
        let ws = Workspace::open_local(dir.path().to_path_buf(), None).unwrap();
        let out = ws.repo_management(None, false, true, false, None);
        assert!(!out.contains("Graph ready"));
        assert!(
            out.contains(" at "),
            "expected the terse default message; got: {out}"
        );
    }

    #[test]
    fn hook_fires_once_per_process_even_when_sha_matches() {
        use std::sync::atomic::{AtomicUsize, Ordering};
        // Local mode fingerprints the dir instead of a git SHA, so we can
        // drive the real `activate` path without git. A stable file keeps
        // the fingerprint constant across both simulated processes.
        let dir = tempfile::tempdir().unwrap();
        std::fs::write(dir.path().join("a.txt"), b"stable").unwrap();

        let calls = Arc::new(AtomicUsize::new(0));
        let make_hook = || -> PostActivateHook {
            let c = calls.clone();
            Arc::new(move |_p, _n| {
                c.fetch_add(1, Ordering::SeqCst);
                Ok(())
            })
        };

        // --- Process 1 ---------------------------------------------------
        let ws = Workspace::open_local(dir.path().to_path_buf(), Some(make_hook())).unwrap();
        // First activate (fingerprint not yet recorded) → hook fires.
        let _ = ws.repo_management(None, false, true, false, None);
        assert_eq!(
            calls.load(Ordering::SeqCst),
            1,
            "first activate must hydrate"
        );
        // Second activate, same process, unchanged fingerprint → cheap-skip.
        let out = ws.repo_management(None, false, true, false, None);
        assert_eq!(
            calls.load(Ordering::SeqCst),
            1,
            "repeat activate in same process must skip the hook"
        );
        assert!(
            out.contains("build skipped"),
            "expected skip suffix, got: {out}"
        );
        drop(ws);

        // --- Process 2 (restart) ----------------------------------------
        // Same dir → inventory.json + last_built_sha persist, but the
        // in-memory hydration set does not. The first activate here must
        // re-fire the hook to rehydrate the consumer's in-memory state.
        let ws2 = Workspace::open_local(dir.path().to_path_buf(), Some(make_hook())).unwrap();
        assert!(
            ws2.last_built_sha(&ws2.active_repo_name().unwrap())
                .is_some(),
            "sanity: last_built_sha should survive the restart"
        );
        let _ = ws2.repo_management(None, false, true, false, None);
        assert_eq!(
            calls.load(Ordering::SeqCst),
            2,
            "fresh process must re-fire the hook even when the SHA matches"
        );
    }

    #[test]
    fn a_b_a_swap_rebuilds_intervening_root() {
        // Regression for the single-slot-consumer stale-graph bug: an
        // A→B→A swap must rebuild A on the second bind, because activating
        // B overwrote the consumer's single live slot. Before the fix the
        // skip gate keyed off "A was hydrated at some point this process"
        // and wrongly skipped, leaving B's product live under A's name.
        use std::sync::atomic::{AtomicUsize, Ordering};
        let root = tempfile::tempdir().unwrap();
        let a = root.path().join("projA");
        let b = root.path().join("projB");
        std::fs::create_dir_all(&a).unwrap();
        std::fs::create_dir_all(&b).unwrap();
        // Stable, distinct contents so each root's fingerprint holds
        // constant across re-binds (so `action == "current"` on the
        // second bind of A — the exact condition the gate keys on).
        std::fs::write(a.join("a.txt"), b"alpha").unwrap();
        std::fs::write(b.join("b.txt"), b"beta").unwrap();

        // The hook records which root it last built into the single slot,
        // mirroring a single-active-graph consumer.
        let built: Arc<std::sync::Mutex<Option<PathBuf>>> = Arc::new(Default::default());
        let built_h = built.clone();
        let calls = Arc::new(AtomicUsize::new(0));
        let calls_h = calls.clone();
        let hook: PostActivateHook = Arc::new(move |p, _n| {
            *built_h.lock().unwrap() = Some(p.to_path_buf());
            calls_h.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });

        let ws = Workspace::open_local(a.clone(), Some(hook)).unwrap();
        // open_local binds A but doesn't fire the hook; first set_root_dir(A)
        // hydrates it.
        let _ = ws.set_root_dir(&a, None);
        assert_eq!(calls.load(Ordering::SeqCst), 1, "first bind of A hydrates");
        assert_eq!(
            built.lock().unwrap().clone(),
            Some(a.canonicalize().unwrap())
        );

        let _ = ws.set_root_dir(&b, None);
        assert_eq!(calls.load(Ordering::SeqCst), 2, "bind of B rebuilds");
        assert_eq!(
            built.lock().unwrap().clone(),
            Some(b.canonicalize().unwrap())
        );

        // The bug: re-binding A must rebuild (slot currently holds B), not
        // cheap-skip. The single slot must end up holding A again.
        let out = ws.set_root_dir(&a, None);
        assert_eq!(
            calls.load(Ordering::SeqCst),
            3,
            "A→B→A must rebuild A; the intervening B overwrote the live slot"
        );
        assert!(
            !out.contains("build skipped"),
            "re-bind of a non-active root must not skip; got: {out}"
        );
        assert_eq!(
            built.lock().unwrap().clone(),
            Some(a.canonicalize().unwrap()),
            "after A→B→A the live slot must hold A, not B"
        );

        // And an immediate re-bind of the *currently active* root (A→A)
        // still cheap-skips — the win the gate was added for is preserved.
        let out = ws.set_root_dir(&a, None);
        assert_eq!(
            calls.load(Ordering::SeqCst),
            3,
            "re-binding the already-active root must skip the hook"
        );
        assert!(
            out.contains("build skipped"),
            "expected skip suffix, got: {out}"
        );
    }

    // ------------------------------------------------------------------
    // revs (multi-revision activation)
    // ------------------------------------------------------------------

    /// Stand up a real git repo at a fresh tempdir with the given tags
    /// created in order (so version-sort ordering is exercised). Returns
    /// the tempdir (keep alive) + its path, or `None` if git is
    /// unavailable in the environment (test then skips).
    fn git_repo_with_tags(tags: &[&str]) -> Option<(tempfile::TempDir, PathBuf)> {
        let dir = tempfile::tempdir().unwrap();
        let root = dir.path().to_path_buf();
        let git = |args: &[&str]| {
            Command::new("git")
                .arg("-C")
                .arg(&root)
                .args(args)
                .output()
                .unwrap()
        };
        if !git(&["init"]).status.success() {
            return None; // git unavailable — caller skips.
        }
        git(&["config", "user.email", "t@example.com"]);
        git(&["config", "user.name", "Test"]);
        git(&["config", "commit.gpgsign", "false"]);
        for (i, tag) in tags.iter().enumerate() {
            std::fs::write(root.join("f.txt"), format!("rev {i}")).unwrap();
            git(&["add", "-A"]);
            assert!(
                git(&["commit", "-m", &format!("c{i}")]).status.success(),
                "git commit failed"
            );
            assert!(git(&["tag", tag]).status.success(), "git tag {tag} failed");
        }
        Some((dir, root))
    }

    // ---- tag classification (pure, no git) --------------------------

    #[test]
    fn classify_tag_extracts_prefix_version_prerelease() {
        let c = classify_tag("apache-arrow-25.0.0").unwrap();
        assert_eq!(c.prefix, "apache-arrow-");
        assert_eq!(c.version, vec![25, 0, 0]);
        assert!(!c.is_prerelease);

        // Prerelease markers with various separators, case-insensitive.
        for t in [
            "apache-arrow-25.0.0.dev",
            "apache-arrow-25.0.0-rc1",
            "apache-arrow-25.0.0-RC0",
            "v1.2.3-beta2",
            "v1.2.3_alpha",
            "v2.0.0-preview",
        ] {
            assert!(
                classify_tag(t).unwrap().is_prerelease,
                "{t} should be prerelease"
            );
        }

        // Distinct families keyed on prefix.
        assert_eq!(classify_tag("go/v18.0.0").unwrap().prefix, "go/v");
        assert_eq!(classify_tag("r-15.0.1").unwrap().prefix, "r-");
        assert_eq!(classify_tag("v1.2.3").unwrap().prefix, "v");

        // Last digit run wins: the `2` in `arrow2` is not the version.
        let c = classify_tag("arrow2-0.17.0").unwrap();
        assert_eq!(c.prefix, "arrow2-");
        assert_eq!(c.version, vec![0, 17, 0]);
    }

    #[test]
    fn classify_tag_excludes_non_version_tags() {
        assert_eq!(classify_tag("r-universe-release"), None);
        assert_eq!(classify_tag("latest"), None);
        assert_eq!(classify_tag("nightly"), None);
        // A version followed by an *unrecognised* suffix is not version-like.
        assert_eq!(classify_tag("v1.2.3-foobar"), None);
    }

    #[test]
    fn select_family_tags_picks_dominant_release_family_skipping_prereleases() {
        // Mirrors the apache/arrow shape: a large `apache-arrow-*` release
        // family (with newest entries being prereleases), plus unrelated
        // `r-*` / `go/v*` families and a rolling non-version pointer.
        let tags: Vec<String> = [
            "apache-arrow-22.0.0",
            "apache-arrow-23.0.0",
            "apache-arrow-24.0.0",
            "apache-arrow-25.0.0-rc0",
            "apache-arrow-25.0.0-rc1",
            "apache-arrow-25.0.0.dev",
            "go/v18.0.0",
            "r-15.0.1",
            "r-16.1.0",
            "r-universe-release",
        ]
        .iter()
        .map(|s| s.to_string())
        .collect();
        // Newest 2 STABLE of the dominant (apache-arrow-) family,
        // oldest→newest; the 25.0.0 prereleases and r-*/go/v* are excluded.
        let got = select_family_tags(&tags, 2).unwrap();
        assert_eq!(got, vec!["apache-arrow-23.0.0", "apache-arrow-24.0.0"]);
    }

    #[test]
    fn select_family_tags_fewer_stable_than_requested_uses_all_stable() {
        let tags: Vec<String> = ["v1.0.0", "v2.0.0", "v3.0.0-rc1"]
            .iter()
            .map(|s| s.to_string())
            .collect();
        // Only two stable; the rc is skipped even though it's newest.
        let got = select_family_tags(&tags, 5).unwrap();
        assert_eq!(got, vec!["v1.0.0", "v2.0.0"]);
    }

    #[test]
    fn select_family_tags_prerelease_only_family_falls_back_to_prereleases() {
        let tags: Vec<String> = ["v1.0.0-rc1", "v1.0.0-rc2", "v0.9.0-beta"]
            .iter()
            .map(|s| s.to_string())
            .collect();
        // No stable tag anywhere → newest prereleases of the family.
        let got = select_family_tags(&tags, 2).unwrap();
        assert_eq!(got, vec!["v1.0.0-rc1", "v1.0.0-rc2"]);
    }

    #[test]
    fn select_family_tags_no_version_like_tags_returns_none() {
        let tags: Vec<String> = ["latest", "nightly", "stable"]
            .iter()
            .map(|s| s.to_string())
            .collect();
        assert_eq!(select_family_tags(&tags, 3), None);
    }

    // ---- resolve_revs Count (git-gated) -----------------------------

    #[test]
    fn resolve_revs_count_falls_back_to_raw_when_no_version_tags() {
        // Non-version tags → the family selector yields None and
        // resolve_revs preserves the raw version-sorted top-n behaviour.
        let Some((_d, root)) = git_repo_with_tags(&["latest", "nightly", "stable"]) else {
            return;
        };
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        let resolved = ws.resolve_revs(&root, &RevsRequest::Count(2)).unwrap();
        // Exactly 2 tags + HEAD, HEAD last; contents come from raw top-n.
        assert_eq!(resolved.len(), 3);
        assert_eq!(resolved.last().unwrap(), "HEAD");
        assert!(resolved[..2].iter().all(|r| r != "HEAD"));
    }

    #[test]
    fn resolve_revs_count_skips_prereleases_of_dominant_family() {
        let Some((_d, root)) =
            git_repo_with_tags(&["v1.0.0", "v2.0.0", "v3.0.0-rc1", "v3.0.0.dev"])
        else {
            return;
        };
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        let resolved = ws.resolve_revs(&root, &RevsRequest::Count(2)).unwrap();
        // Newest 2 stable (v1.0.0, v2.0.0) oldest→newest, then HEAD —
        // the v3 prereleases are excluded.
        assert_eq!(resolved, vec!["v1.0.0", "v2.0.0", "HEAD"]);
    }

    #[test]
    fn resolve_revs_count_picks_newest_n_oldest_first_head_last() {
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0", "v1.1.0", "v2.0.0"]) else {
            return;
        };
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        let resolved = ws
            .resolve_revs(&root, &RevsRequest::Count(2))
            .expect("resolve should succeed");
        // Newest 2 = v2.0.0, v1.1.0 → oldest→newest → v1.1.0, v2.0.0, then HEAD.
        assert_eq!(resolved, vec!["v1.1.0", "v2.0.0", "HEAD"]);
    }

    #[test]
    fn resolve_revs_count_fewer_tags_than_requested_uses_all() {
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0", "v2.0.0"]) else {
            return;
        };
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        let resolved = ws.resolve_revs(&root, &RevsRequest::Count(10)).unwrap();
        assert_eq!(resolved, vec!["v1.0.0", "v2.0.0", "HEAD"]);
    }

    #[test]
    fn resolve_revs_count_errors_when_no_tags() {
        let Some((_d, root)) = git_repo_with_tags(&[]) else {
            return;
        };
        // Empty repo has no commits yet; make one commit but no tags.
        let git = |args: &[&str]| {
            Command::new("git")
                .arg("-C")
                .arg(&root)
                .args(args)
                .output()
                .unwrap()
        };
        std::fs::write(root.join("f.txt"), b"x").unwrap();
        git(&["add", "-A"]);
        git(&["commit", "-m", "c0"]);
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        let err = ws
            .resolve_revs(&root, &RevsRequest::Count(3))
            .expect_err("no tags → error");
        assert!(
            err.to_string().contains("no tags"),
            "expected a 'no tags' error, got: {err}"
        );
    }

    // ---- dedup of resolved revs -------------------------------------

    #[test]
    fn dedup_labels_is_order_preserving_first_wins() {
        assert_eq!(
            dedup_labels(vec!["HEAD".into(), "HEAD".into()]),
            vec!["HEAD"]
        );
        assert_eq!(
            dedup_labels(vec![
                "v1".into(),
                "v2".into(),
                "v1".into(),
                "v3".into(),
                "v2".into(),
            ]),
            vec!["v1", "v2", "v3"]
        );
        // Empty and already-unique lists pass through untouched.
        assert_eq!(dedup_labels(vec![]), Vec::<String>::new());
        assert_eq!(dedup_labels(vec!["a".into(), "b".into()]), vec!["a", "b"]);
    }

    #[test]
    fn resolve_revs_list_dedups_duplicate_revspecs() {
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0"]) else {
            return;
        };
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        // `["HEAD","HEAD"]` collapses to a single `HEAD`.
        let got = ws
            .resolve_revs(
                &root,
                &RevsRequest::List(vec!["HEAD".into(), "HEAD".into()]),
            )
            .unwrap();
        assert_eq!(got, vec!["HEAD"]);
        // First-occurrence order is preserved across mixed duplicates.
        let got = ws
            .resolve_revs(
                &root,
                &RevsRequest::List(vec!["v1.0.0".into(), "HEAD".into(), "v1.0.0".into()]),
            )
            .unwrap();
        assert_eq!(got, vec!["v1.0.0", "HEAD"]);
    }

    #[test]
    fn resolve_revs_list_validates_and_rejects_unknown() {
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0", "v1.1.0"]) else {
            return;
        };
        let ws = Workspace::open_local(root.clone(), None).unwrap();
        // Explicit list is used verbatim (no HEAD appended, no sort).
        let ok = ws
            .resolve_revs(
                &root,
                &RevsRequest::List(vec!["v1.1.0".into(), "v1.0.0".into()]),
            )
            .unwrap();
        assert_eq!(ok, vec!["v1.1.0", "v1.0.0"]);
        // An unknown rev is a clear error naming the bad rev.
        let err = ws
            .resolve_revs(&root, &RevsRequest::List(vec!["v9.9.9".into()]))
            .expect_err("unknown rev → error");
        assert!(
            err.to_string().contains("v9.9.9") && err.to_string().contains("does not exist"),
            "expected an unknown-rev error, got: {err}"
        );
    }

    #[test]
    fn revs_hook_receives_resolved_revs_and_plain_hook_untouched() {
        use std::sync::atomic::{AtomicUsize, Ordering};
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0", "v1.1.0", "v2.0.0"]) else {
            return;
        };
        let plain_calls = Arc::new(AtomicUsize::new(0));
        let seen_revs: Arc<std::sync::Mutex<Option<Vec<String>>>> = Arc::new(Default::default());
        let pc = plain_calls.clone();
        let plain: PostActivateHook = Arc::new(move |_p, _n| {
            pc.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        let sr = seen_revs.clone();
        let revs_hook: PostActivateRevsHook = Arc::new(move |_p, _n, revs| {
            *sr.lock().unwrap() = Some(revs.to_vec());
            Ok(())
        });
        let ws = Workspace::open_local(root.clone(), Some(plain))
            .unwrap()
            .with_post_activate_revs(revs_hook);
        let out = ws.repo_management(None, false, true, false, Some(&RevsRequest::Count(2)));
        // The revs-hook ran with the resolved list; the plain hook did NOT.
        assert_eq!(
            seen_revs.lock().unwrap().clone().unwrap(),
            vec!["v1.1.0", "v2.0.0", "HEAD"]
        );
        assert_eq!(
            plain_calls.load(Ordering::SeqCst),
            0,
            "plain hook must not fire when the revs-hook handled the request"
        );
        // The activation message names the resolved revs on one line.
        assert!(
            out.contains("revs: v1.1.0, v2.0.0, HEAD"),
            "activation message should list the resolved revs; got: {out}"
        );
    }

    #[test]
    fn plain_hook_used_and_no_revs_line_when_no_revs_requested() {
        use std::sync::atomic::{AtomicUsize, Ordering};
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0"]) else {
            return;
        };
        let plain_calls = Arc::new(AtomicUsize::new(0));
        let revs_seen = Arc::new(AtomicUsize::new(0));
        let pc = plain_calls.clone();
        let plain: PostActivateHook = Arc::new(move |_p, _n| {
            pc.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        let rs = revs_seen.clone();
        let revs_hook: PostActivateRevsHook = Arc::new(move |_p, _n, _revs| {
            rs.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        let ws = Workspace::open_local(root.clone(), Some(plain))
            .unwrap()
            .with_post_activate_revs(revs_hook);
        // No revs → plain hook fires, revs-hook untouched, no `revs:` line.
        let out = ws.repo_management(None, false, true, false, None);
        assert_eq!(plain_calls.load(Ordering::SeqCst), 1);
        assert_eq!(
            revs_seen.load(Ordering::SeqCst),
            0,
            "revs-hook must not fire when no revs were requested"
        );
        assert!(
            !out.contains("revs:"),
            "no revs line expected on a plain activation; got: {out}"
        );
    }

    #[test]
    fn revs_requested_without_revs_hook_falls_back_to_plain_no_revs_line() {
        use std::sync::atomic::{AtomicUsize, Ordering};
        let Some((_d, root)) = git_repo_with_tags(&["v1.0.0", "v2.0.0"]) else {
            return;
        };
        let plain_calls = Arc::new(AtomicUsize::new(0));
        let pc = plain_calls.clone();
        let plain: PostActivateHook = Arc::new(move |_p, _n| {
            pc.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        // No revs-hook attached: a revs request degrades to the plain
        // (HEAD-only) build and does NOT claim a rev-set in the message.
        let ws = Workspace::open_local(root.clone(), Some(plain)).unwrap();
        let out = ws.repo_management(None, false, true, false, Some(&RevsRequest::Count(1)));
        assert_eq!(plain_calls.load(Ordering::SeqCst), 1);
        assert!(
            !out.contains("revs:"),
            "must not report a rev-set when only the plain hook ran; got: {out}"
        );
    }

    // ---- rev-set-aware skip gate + stored-request persistence -------

    /// Build a local workspace over a git repo with tags, wired with both
    /// a plain and a revs hook, each incrementing a shared counter.
    /// Returns (workspace, tempdir-guard, root, plain_calls, revs_calls).
    #[allow(clippy::type_complexity)]
    fn ws_with_both_hooks(
        tags: &[&str],
    ) -> Option<(
        Workspace,
        tempfile::TempDir,
        PathBuf,
        Arc<std::sync::atomic::AtomicUsize>,
        Arc<std::sync::atomic::AtomicUsize>,
    )> {
        use std::sync::atomic::{AtomicUsize, Ordering};
        let (d, root) = git_repo_with_tags(tags)?;
        let plain_calls = Arc::new(AtomicUsize::new(0));
        let revs_calls = Arc::new(AtomicUsize::new(0));
        let pc = plain_calls.clone();
        let plain: PostActivateHook = Arc::new(move |_p, _n| {
            pc.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        let rc = revs_calls.clone();
        let revs_hook: PostActivateRevsHook = Arc::new(move |_p, _n, _r| {
            rc.fetch_add(1, Ordering::SeqCst);
            Ok(())
        });
        let ws = Workspace::open_local(root.clone(), Some(plain))
            .unwrap()
            .with_post_activate_revs(revs_hook);
        Some((ws, d, root, plain_calls, revs_calls))
    }

    #[test]
    fn plain_activation_after_revs_build_rebuilds_plain() {
        use std::sync::atomic::Ordering;
        let Some((ws, _d, root, plain_calls, revs_calls)) =
            ws_with_both_hooks(&["v1.0.0", "v2.0.0"])
        else {
            return;
        };
        // Multi-rev build first.
        let _ = ws.set_root_dir(&root, Some(&RevsRequest::Count(2)));
        assert_eq!(revs_calls.load(Ordering::SeqCst), 1);
        assert_eq!(plain_calls.load(Ordering::SeqCst), 0);
        // A plain re-bind at the SAME (unchanged) root must NOT cheap-skip
        // just because HEAD matches — the last build was multi-rev. It
        // rebuilds plain, and the message claims no rev-set.
        let out = ws.set_root_dir(&root, None);
        assert_eq!(
            plain_calls.load(Ordering::SeqCst),
            1,
            "plain re-activation after a revs build must fire the plain hook"
        );
        assert!(
            !out.contains("build skipped"),
            "must not skip a plain re-activation after a revs build; got: {out}"
        );
        assert!(
            !out.contains("revs:"),
            "plain rebuild must not claim revs; got: {out}"
        );
        // The stored request is cleared, so a further plain re-bind now
        // cheap-skips (proves the reset took).
        let out = ws.set_root_dir(&root, None);
        assert_eq!(
            plain_calls.load(Ordering::SeqCst),
            1,
            "second plain re-bind skips"
        );
        assert!(
            out.contains("build skipped"),
            "expected skip suffix; got: {out}"
        );
    }

    #[test]
    fn update_after_revs_build_reapplies_stored_revs() {
        use std::sync::atomic::Ordering;
        let Some((ws, _d, root, plain_calls, revs_calls)) =
            ws_with_both_hooks(&["v1.0.0", "v2.0.0"])
        else {
            return;
        };
        // Multi-rev build first.
        let _ = ws.set_root_dir(&root, Some(&RevsRequest::Count(2)));
        assert_eq!(revs_calls.load(Ordering::SeqCst), 1);
        // A bare `update` (no revs) must re-apply the stored rev-set —
        // re-firing the revs hook, not collapsing to a plain HEAD build.
        let out = ws.repo_management(None, false, true, false, None);
        assert_eq!(
            revs_calls.load(Ordering::SeqCst),
            2,
            "bare update must re-apply the stored rev-set"
        );
        assert_eq!(
            plain_calls.load(Ordering::SeqCst),
            0,
            "bare update after a revs build must not fall to the plain hook"
        );
        assert!(
            out.contains("revs:"),
            "re-applied update should list the revs; got: {out}"
        );
    }

    #[test]
    fn revs_activation_after_plain_build_always_rebuilds() {
        use std::sync::atomic::Ordering;
        let Some((ws, _d, root, plain_calls, revs_calls)) =
            ws_with_both_hooks(&["v1.0.0", "v2.0.0"])
        else {
            return;
        };
        // Plain build first.
        let _ = ws.set_root_dir(&root, None);
        assert_eq!(plain_calls.load(Ordering::SeqCst), 1);
        assert_eq!(revs_calls.load(Ordering::SeqCst), 0);
        // A revs request at the unchanged HEAD still always fires the revs
        // hook (revs requests are never skipped by the SHA gate).
        let _ = ws.set_root_dir(&root, Some(&RevsRequest::Count(2)));
        assert_eq!(
            revs_calls.load(Ordering::SeqCst),
            1,
            "a revs request must always rebuild, even at an unchanged HEAD"
        );
    }

    #[test]
    fn last_built_revs_round_trips_and_clears_on_plain_build() {
        let dir = tempfile::tempdir().unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        ws.bump_access("acme/widgets", "cloned");
        assert_eq!(ws.last_built_revs("acme/widgets"), None);
        // Record a multi-rev build.
        ws.record_built("acme/widgets", "sha1", Some(&RevsRequest::Count(3)));
        assert_eq!(
            ws.last_built_revs("acme/widgets"),
            Some(RevsRequest::Count(3))
        );
        // Survives a reopen (persisted to inventory.json).
        let ws2 = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        assert_eq!(
            ws2.last_built_revs("acme/widgets"),
            Some(RevsRequest::Count(3))
        );
        // A subsequent plain build clears the stored request.
        ws2.record_built("acme/widgets", "sha2", None);
        assert_eq!(ws2.last_built_revs("acme/widgets"), None);
        // A List request round-trips too.
        ws2.record_built(
            "acme/widgets",
            "sha3",
            Some(&RevsRequest::List(vec!["v1".into(), "v2".into()])),
        );
        assert_eq!(
            ws2.last_built_revs("acme/widgets"),
            Some(RevsRequest::List(vec!["v1".into(), "v2".into()]))
        );
    }

    #[test]
    fn inventory_loads_legacy_entries_without_revs_field() {
        // An entry carrying last_built_sha but no last_built_revs (an
        // inventory written before the field existed) loads cleanly with
        // the request defaulting to None.
        let dir = tempfile::tempdir().unwrap();
        let legacy = r#"{
            "old/repo": {
                "cloned_at": "2024-01-01T00:00:00",
                "last_accessed": "2024-01-01T00:00:00",
                "access_count": 5,
                "stale": false,
                "last_built_sha": "deadbeef"
            }
        }"#;
        std::fs::write(dir.path().join("inventory.json"), legacy).unwrap();
        let ws = Workspace::open(dir.path().to_path_buf(), 7, None).unwrap();
        assert_eq!(ws.last_built_sha("old/repo").as_deref(), Some("deadbeef"));
        assert_eq!(ws.last_built_revs("old/repo"), None);
    }
}