//! In-memory content store — fast synchronous reads for story markdown.
//!
//! Backed by a `HashMap<story_id, markdown>` wrapped in a `Mutex`. In
//! non-test builds the store lives in a process-global `OnceLock`; in tests
//! each thread gets its own isolated copy via a `thread_local!` to avoid
//! cross-test pollution.
use std::collections::HashMap;
use std::sync::{Mutex, OnceLock};

/// Typed key for the in-memory content store.
///
/// Each variant maps to a distinct raw key namespace so that content written
/// under one variant is never visible under another — no raw `format!()`
/// key construction is needed at call sites outside `db/`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ContentKey<'a> {
    /// Main markdown body of a work item (story, bug, spike, refactor, epic).
    Story(&'a str),
    /// Gate failure output from the last failed agent run.
    GateOutput(&'a str),
    /// Consecutive abort-respawn counter.
    AbortRespawnCount(&'a str),
    /// Mergemaster re-spawn counter.
    MergeMasterSpawnCount(&'a str),
    /// Evidence that `run_tests` passed during an agent session.
    RunTestsOk(&'a str),
    /// Flag indicating a commit-recovery respawn is in progress.  Stored as
    /// a decimal string counting consecutive respawns that made NO file-edit
    /// progress (worktree diff byte-identical to the previous attempt).  Reset
    /// to "1" whenever a respawn produces a different diff fingerprint.
    CommitRecoveryPending(&'a str),
    /// Worktree diff byte-length captured at the last commit-recovery respawn
    /// trigger.  Used to detect whether the agent made any file-edit progress
    /// between consecutive session-boundary-clean exits.  Same byte length on
    /// two consecutive attempts → no progress → increment CommitRecoveryPending.
    CommitRecoveryDiffFingerprint(&'a str),
    /// Absolute count of commit-recovery respawns issued for a story since the
    /// last successful commit.  Increments every respawn regardless of whether
    /// the diff fingerprint changed.  Outer cap that catches the "agent flaps
    /// between different file edits each session but never commits" pattern
    /// where the progress-aware counter would never trigger.
    CommitRecoveryTotalAttempts(&'a str),
    /// Flag indicating a merge gate fixup coder session is in progress.
    ///
    /// Set when the merge gate fails with a self-evident-fix class of failure
    /// (fmt drift, clippy warning, missing doc) so the pipeline advance handler
    /// can route the fixup coder's completion directly back to merge instead of
    /// through the normal QA path (story 981).
    MergeFixupPending(&'a str),
    /// JSON-serialised `MergeFailureKind` written alongside `GateOutput` so the
    /// CRDT projection layer can reconstruct the typed kind on server restart
    /// without substring-scanning the gate output string (story 986).
    MergeFailureKind(&'a str),
    /// Flag set by the merge runner when a squash merge succeeds with
    /// `story_archived: true`.  Written before the CRDT job status is set to
    /// "completed" so the mergemaster agent exit handler in `spawn.rs` can
    /// distinguish a clean success from a transient crash (bug 1008).
    MergeSuccess(&'a str),
    /// JSON-serialised `MergeReport` written by the merge runner on successful
    /// completion.  Read by `get_merge_status` to surface gate output for the
    /// "completed" state without a separate MergeJob CRDT register (story 1036).
    MergeReport(&'a str),
    /// Flag written by spawn.rs when a coder session exits with a non-zero exit
    /// code (API error, network failure, or Claude-API-level budget exhaustion).
    /// Prevents the stuck-respawn counter from incrementing for forced exits —
    /// only self-exits with no file or read changes count toward the cap.
    /// Consumed (read + deleted) by the commit-recovery path in pipeline advance.
    CommitRecoveryForcedExit(&'a str),
    /// Cumulative set of files read across all commit-recovery sessions for a
    /// story, stored as a newline-separated sorted list.  Used to detect whether
    /// the agent made read-exploration progress even when the worktree diff did
    /// not grow (story 1089, AC2).  Cleared when a commit lands or the story blocks.
    CommitRecoveryReadSet(&'a str),
}

impl<'a> ContentKey<'a> {
    /// Lower this typed key to the underlying storage string used by the
    /// CRDT content store (`{story_id}` for the base story, `{story_id}:<kind>`
    /// for per-purpose sub-keys). Internal — callers should use the typed
    /// `read_content` / `write_content` wrappers instead of touching strings.
    pub(super) fn as_raw_key(&self) -> String {
        match self {
            ContentKey::Story(id) => id.to_string(),
            ContentKey::GateOutput(id) => format!("{id}:gate_output"),
            ContentKey::AbortRespawnCount(id) => format!("{id}:abort_respawn_count"),
            ContentKey::MergeMasterSpawnCount(id) => format!("{id}:mergemaster_spawn_count"),
            ContentKey::RunTestsOk(id) => format!("{id}:run_tests_ok"),
            ContentKey::CommitRecoveryPending(id) => format!("{id}:commit_recovery_pending"),
            ContentKey::CommitRecoveryDiffFingerprint(id) => {
                format!("{id}:commit_recovery_diff_fingerprint")
            }
            ContentKey::CommitRecoveryTotalAttempts(id) => {
                format!("{id}:commit_recovery_total_attempts")
            }
            ContentKey::MergeFixupPending(id) => format!("{id}:merge_fixup_pending"),
            ContentKey::MergeFailureKind(id) => format!("{id}:merge_failure_kind"),
            ContentKey::MergeSuccess(id) => format!("{id}:merge_success"),
            ContentKey::MergeReport(id) => format!("{id}:merge_report"),
            ContentKey::CommitRecoveryForcedExit(id) => {
                format!("{id}:commit_recovery_forced_exit")
            }
            ContentKey::CommitRecoveryReadSet(id) => format!("{id}:commit_recovery_read_set"),
        }
    }
}

static CONTENT_STORE: OnceLock<Mutex<HashMap<String, String>>> = OnceLock::new();

#[cfg(test)]
thread_local! {
    /// Per-thread isolated content store used in tests to prevent cross-test pollution.
    pub(super) static CONTENT_STORE_TL: OnceLock<Mutex<HashMap<String, String>>> = const { OnceLock::new() };
}

#[cfg(not(test))]
/// Return a reference to the process-global content store, or `None` if not yet initialised.
pub(super) fn get_content_store() -> Option<&'static Mutex<HashMap<String, String>>> {
    CONTENT_STORE.get()
}

#[cfg(test)]
/// Return the thread-local content store for tests, falling back to the global store.
pub(super) fn get_content_store() -> Option<&'static Mutex<HashMap<String, String>>> {
    let tl = CONTENT_STORE_TL.with(|lock| {
        if lock.get().is_some() {
            Some(lock as *const OnceLock<Mutex<HashMap<String, String>>>)
        } else {
            None
        }
    });
    if let Some(ptr) = tl {
        // SAFETY: The thread-local lives as long as the thread, which outlives
        // any test using it.  We only need 'static for the return type.
        let lock = unsafe { &*ptr };
        lock.get()
    } else {
        CONTENT_STORE.get()
    }
}

/// Read content from the in-memory store by typed key.
pub fn read_content(key: ContentKey<'_>) -> Option<String> {
    let store = get_content_store()?;
    let map = store.lock().ok()?;
    map.get(&key.as_raw_key()).cloned()
}

/// Write (or overwrite) content in the in-memory store by typed key.
pub fn write_content(key: ContentKey<'_>, content: &str) {
    if let Some(store) = get_content_store()
        && let Ok(mut map) = store.lock()
    {
        map.insert(key.as_raw_key(), content.to_string());
    }
}

/// Remove an entry from the in-memory store by typed key.
pub fn delete_content(key: ContentKey<'_>) {
    if let Some(store) = get_content_store()
        && let Ok(mut map) = store.lock()
    {
        map.remove(&key.as_raw_key());
    }
}

/// Ensure the in-memory content store is initialised.
///
/// In non-test builds: init-once via `OnceLock` (safe to call multiple times).
/// In test builds: always resets `CONTENT_STORE_TL` to an empty `HashMap` so
/// each test on the same thread starts with a clean store.
pub fn ensure_content_store() {
    #[cfg(not(test))]
    {
        let _ = CONTENT_STORE.set(Mutex::new(HashMap::new()));
    }

    #[cfg(test)]
    {
        CONTENT_STORE_TL.with(|lock| {
            if let Some(mutex) = lock.get() {
                // Already initialised on this thread — reset to empty so the
                // next test does not see content written by a previous test.
                mutex.lock().unwrap().clear();
            } else {
                let _ = lock.set(Mutex::new(HashMap::new()));
            }
        });
        crate::crdt_state::init_for_test();
    }
}

/// Return all story IDs present in the content store.
pub fn all_content_ids() -> Vec<String> {
    match get_content_store() {
        Some(store) => match store.lock() {
            Ok(map) => map.keys().cloned().collect(),
            Err(_) => Vec::new(),
        },
        None => Vec::new(),
    }
}

/// Initialise the content store from a pre-loaded map (used during DB startup).
pub(super) fn init_content_store(map: HashMap<String, String>) {
    let _ = CONTENT_STORE.set(Mutex::new(map));
}

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

    /// Regression: two sequential `ensure_content_store()` + write + read cycles
    /// in the same test body must not see each other's content.  Before the fix,
    /// `ensure_content_store()` was a no-op on the second call (OnceLock gating),
    /// so the second cycle could read items written in the first cycle.
    #[test]
    fn sequential_ensure_content_store_resets_state() {
        // ── Cycle 1 ──────────────────────────────────────────────────────────
        ensure_content_store();
        write_content(ContentKey::Story("1111_cycle1"), "cycle-one body");
        assert_eq!(
            read_content(ContentKey::Story("1111_cycle1")).as_deref(),
            Some("cycle-one body"),
            "cycle 1: item must be readable after write"
        );

        // ── Cycle 2: reset, write a different item ────────────────────────────
        ensure_content_store();
        // Cycle-1 item must no longer be visible.
        assert!(
            read_content(ContentKey::Story("1111_cycle1")).is_none(),
            "cycle 2: store must be empty; cycle-1 content must not bleed through"
        );
        write_content(ContentKey::Story("1111_cycle2"), "cycle-two body");
        assert_eq!(
            read_content(ContentKey::Story("1111_cycle2")).as_deref(),
            Some("cycle-two body"),
            "cycle 2: own item must be readable"
        );
        // And cycle-1 key must still be absent.
        assert!(
            read_content(ContentKey::Story("1111_cycle1")).is_none(),
            "cycle 2: cycle-1 content must remain absent after cycle-2 write"
        );
    }

    /// AC 2 regression: writing under `ContentKey::Story` is not visible under
    /// `ContentKey::GateOutput` (and vice versa).  The typed key namespace, not
    /// runtime substring matching, enforces the separation.
    #[test]
    fn wrong_key_variant_is_isolated() {
        ensure_content_store();
        let id = "9961_regression_key_isolation";

        write_content(ContentKey::Story(id), "story body");

        // A different variant for the same base id must not surface the story body.
        assert!(
            read_content(ContentKey::GateOutput(id)).is_none(),
            "GateOutput key must not read Story content"
        );
        assert!(
            read_content(ContentKey::RunTestsOk(id)).is_none(),
            "RunTestsOk key must not read Story content"
        );

        // The Story variant itself must still return the content.
        assert_eq!(
            read_content(ContentKey::Story(id)).as_deref(),
            Some("story body")
        );

        // Write under a second variant; reading under Story must still return
        // the original body, not the gate output.
        write_content(ContentKey::GateOutput(id), "gate failure text");
        assert_eq!(
            read_content(ContentKey::Story(id)).as_deref(),
            Some("story body"),
            "Story key must not be polluted by GateOutput write"
        );
        assert_eq!(
            read_content(ContentKey::GateOutput(id)).as_deref(),
            Some("gate failure text")
        );

        // Cleanup.
        delete_content(ContentKey::Story(id));
        delete_content(ContentKey::GateOutput(id));
    }
}