//! Write operations for the pipeline — content, stage transitions, and deletions.
//!
//! Each function updates three layers atomically in order: the in-memory
//! content store, the CRDT (source of truth for metadata), and the SQLite
//! shadow table (via the background channel).
use super::content_store::{
    ContentKey, all_content_ids, delete_content, ensure_content_store, read_content, write_content,
};
use super::shadow_write::{PIPELINE_DB, PipelineWriteMsg};

/// Typed metadata for a pipeline item write.
///
/// Story 929: callers pass metadata explicitly — no YAML parsing.  Every
/// field is `Option`-typed; `None` means "leave unchanged" on update,
/// "use the default" on insert.
#[derive(Default, Clone, Debug)]
pub struct ItemMeta {
    pub name: Option<String>,
    pub agent: Option<String>,
    pub depends_on: Option<Vec<u32>>,
}

impl ItemMeta {
    /// Convenience constructor for the common "just set a name" case.
    #[cfg(test)]
    pub fn named(name: impl Into<String>) -> Self {
        Self {
            name: Some(name.into()),
            ..Self::default()
        }
    }
}

/// Normalise a stage string at the db boundary.
///
/// Accepts the clean post-934 vocabulary (passthrough) and the pre-934
/// directory-style strings (`"2_current"`, `"4_merge"`, etc.) by mapping
/// them to the clean form before handing off to `Stage::from_dir` (which
/// itself only accepts clean form after stage 6).  This keeps the public
/// db API tolerant for callers that still pass legacy strings while the
/// internal type stays strict.
fn normalise_stage_str(stage: &str) -> &str {
    match stage {
        "0_upcoming" => "upcoming",
        "1_backlog" => "backlog",
        "2_current" => "coding",
        "2_blocked" => "blocked",
        "3_qa" => "qa",
        "4_merge" => "merge",
        "4_merge_failure" => "merge_failure",
        "4_merge_failure_final" => "merge_failure_final",
        "5_done" => "done",
        "6_archived" => "archived",
        "7_frozen" => "frozen",
        "7_review_hold" => "review_hold",
        other => other,
    }
}

/// Write a pipeline item from in-memory content (no filesystem access).
///
/// This is the primary write path for the DB-backed pipeline.  It updates
/// the CRDT, the in-memory content store, and the SQLite shadow table.
///
/// The metadata in `meta` is authoritative: this function does NOT parse
/// `content` to extract front-matter fields.  Callers must pass typed
/// metadata explicitly via `ItemMeta`.
pub fn write_item_with_content(story_id: &str, stage: &str, content: &str, meta: ItemMeta) {
    let depends_on_json = meta
        .depends_on
        .as_ref()
        .and_then(|d| serde_json::to_string(d).ok());

    // Update in-memory content store.
    ensure_content_store();
    write_content(ContentKey::Story(story_id), content);

    // Primary: CRDT ops.
    let stage = normalise_stage_str(stage);
    let Some(typed_stage) = crate::pipeline_state::Stage::from_dir(stage) else {
        crate::slog!(
            "[db] write_item_with_content: unknown stage '{stage}' for {story_id}; skipping CRDT write"
        );
        return;
    };
    let merged_at_ts = matches!(typed_stage, crate::pipeline_state::Stage::Done { .. })
        .then(|| chrono::Utc::now().timestamp() as f64);
    crate::crdt_state::write_item(
        story_id,
        &typed_stage,
        meta.name.as_deref(),
        meta.agent.as_deref(),
        depends_on_json.as_deref(),
        merged_at_ts,
    );

    // Shadow: pipeline_items table (only when DB is initialised).
    if let Some(db) = PIPELINE_DB.get() {
        let msg = PipelineWriteMsg {
            story_id: story_id.to_string(),
            stage: stage.to_string(),
            name: meta.name,
            agent: meta.agent,
            retry_count: None,
            depends_on: depends_on_json,
            content: Some(content.to_string()),
        };
        let _ = db.tx.send(msg);
    }
}

/// Update only the stage of an existing item (used by move operations).
///
/// Reads current content from the in-memory store, updates the CRDT stage,
/// and persists the change.  Optionally modifies the content (e.g. to clear
/// front-matter fields).
pub fn move_item_stage(
    story_id: &str,
    new_stage: &str,
    content_transform: Option<&dyn Fn(&str) -> String>,
) {
    let current_content = read_content(ContentKey::Story(story_id));

    let content = match (&current_content, content_transform) {
        (Some(c), Some(transform)) => {
            let new_content = transform(c);
            write_content(ContentKey::Story(story_id), &new_content);
            Some(new_content)
        }
        (Some(c), None) => Some(c.clone()),
        _ => None,
    };

    // Story 929: metadata (name/agent/depends_on) is owned by the CRDT typed
    // registers — no need to re-derive it from the content body's YAML front
    // matter on every stage transition.  Pass `None` for those fields so
    // write_item leaves the existing registers untouched.
    let new_stage = normalise_stage_str(new_stage);
    let Some(typed_stage) = crate::pipeline_state::Stage::from_dir(new_stage) else {
        crate::slog!(
            "[db] move_item_stage: unknown stage '{new_stage}' for {story_id}; skipping CRDT write"
        );
        return;
    };
    let merged_at_ts = matches!(typed_stage, crate::pipeline_state::Stage::Done { .. })
        .then(|| chrono::Utc::now().timestamp() as f64);
    crate::crdt_state::write_item(story_id, &typed_stage, None, None, None, merged_at_ts);
    // Bug 780: stage transitions reset retry_count to 0.  retry_count tracks
    // attempts at THIS stage's work (coding, merging, qa); a fresh attempt at
    // a new stage is conceptually distinct from prior attempts at a different
    // stage.  `blocked` is preserved — that's a human-set signal that survives
    // transitions.
    crate::crdt_state::set_retry_count(story_id, 0);

    // Shadow table — read current metadata from the CRDT so the SQLite
    // mirror stays in sync.  Always reset retry_count to 0 on stage transition.
    if let Some(db) = PIPELINE_DB.get() {
        let view = crate::crdt_state::read_item(story_id);
        let name = view.as_ref().map(|v| v.name().to_string());
        let agent = view.as_ref().and_then(|v| v.agent().map(|a| a.to_string()));
        let depends_on = view
            .as_ref()
            .map(|v| v.depends_on())
            .filter(|d| !d.is_empty())
            .and_then(|d| serde_json::to_string(d).ok());
        let msg = PipelineWriteMsg {
            story_id: story_id.to_string(),
            stage: new_stage.to_string(),
            name,
            agent,
            retry_count: Some(0),
            depends_on,
            content,
        };
        let _ = db.tx.send(msg);
    }
}

/// Shadow-write the updated agent field for an existing pipeline item.
///
/// Called by [`crate::crdt_state::set_agent`] after the CRDT register is updated
/// so `pipeline_items.agent` stays in sync.  Reads the full current metadata from
/// the CRDT (stage, name, depends_on, retry_count) to avoid overwriting other
/// columns with stale values — only the `agent` column carries the new data.
pub fn sync_item_agent(story_id: &str) {
    let Some(db) = PIPELINE_DB.get() else {
        return;
    };
    let Some(view) = crate::crdt_state::read_item(story_id) else {
        return;
    };
    let stage = view.stage().dir_name().to_string();
    let name = Some(view.name().to_string());
    let agent = view.agent().map(|a| a.as_str().to_string());
    let depends_on = {
        let d = view.depends_on();
        if d.is_empty() {
            None
        } else {
            serde_json::to_string(d).ok()
        }
    };
    let retry_count = Some(i64::from(view.retry_count()));
    let msg = PipelineWriteMsg {
        story_id: story_id.to_string(),
        stage,
        name,
        agent,
        retry_count,
        depends_on,
        content: None,
    };
    let _ = db.tx.send(msg);
}

/// Delete a story from the shadow table (fire-and-forget).
pub fn delete_item(story_id: &str) {
    delete_content(ContentKey::Story(story_id));

    if let Some(db) = PIPELINE_DB.get() {
        // Reuse the channel with a special "deleted" stage marker.
        // The background task will handle it.
        // Actually, we send a delete message by abusing the write — we'll
        // just remove it by setting stage to "deleted".
        let msg = PipelineWriteMsg {
            story_id: story_id.to_string(),
            stage: "deleted".to_string(),
            name: None,
            agent: None,
            retry_count: None,
            depends_on: None,
            content: None,
        };
        let _ = db.tx.send(msg);
    }
}

/// Delete a story from the shadow table, awaiting the SQLite write.
///
/// Unlike [`delete_item`], this function issues a direct `DELETE FROM
/// pipeline_items` via the shared pool and awaits the result — so the row
/// is gone before this function returns.  Use this from async call sites
/// where durability of the deletion matters (e.g. story deletion, startup
/// migration).  Falls back to the fire-and-forget channel when the shared
/// pool is not yet initialised.
pub async fn delete_item_sync(story_id: &str) {
    delete_content(ContentKey::Story(story_id));

    if let Some(pool) = super::shadow_write::get_shared_pool() {
        if let Err(e) = sqlx::query("DELETE FROM pipeline_items WHERE id = ?1")
            .bind(story_id)
            .execute(pool)
            .await
        {
            crate::slog_warn!(
                "[db] Synchronous delete from pipeline_items failed for '{}': {e}",
                story_id
            );
        }
    } else if let Some(db) = PIPELINE_DB.get() {
        let msg = PipelineWriteMsg {
            story_id: story_id.to_string(),
            stage: "deleted".to_string(),
            name: None,
            agent: None,
            retry_count: None,
            depends_on: None,
            content: None,
        };
        let _ = db.tx.send(msg);
    }
}

/// Sync the shadow table's `name` column after a CRDT name-register write.
///
/// Reads the current item from the CRDT (which already holds the new name after
/// `apply_and_persist`) and sends a `PipelineWriteMsg` so the SQLite mirror
/// stays in sync.  All other columns (stage, agent, retry_count, depends_on)
/// are preserved from the live CRDT view; `content` is left as `None` so the
/// UPSERT's `COALESCE` keeps the existing value.
///
/// No-ops if the DB is not initialised or the item is not in the CRDT.
pub fn sync_item_name(story_id: &str) {
    let Some(db) = PIPELINE_DB.get() else { return };
    let Some(view) = crate::crdt_state::read_item(story_id) else {
        return;
    };
    let depends_on = {
        let d = view.depends_on();
        if d.is_empty() {
            None
        } else {
            serde_json::to_string(d).ok()
        }
    };
    let msg = PipelineWriteMsg {
        story_id: story_id.to_string(),
        stage: view.stage().dir_name().to_string(),
        name: Some(view.name().to_string()),
        agent: view.agent().map(|a| a.to_string()),
        retry_count: Some(view.retry_count() as i64),
        depends_on,
        content: None,
    };
    let _ = db.tx.send(msg);
}

/// Sync the `depends_on` field of a pipeline item from the CRDT to the shadow table.
///
/// Called after [`crate::crdt_state::set_depends_on`] updates the CRDT register so
/// that the SQLite shadow table stays in lock-step.  Reads the full current view from
/// the CRDT (stage, name, agent, retry_count, depends_on) and sends a
/// [`PipelineWriteMsg`] over [`PIPELINE_DB`]`.tx`.  Pattern mirrors
/// [`move_item_stage`] lines 157-176.  No-op when the CRDT is uninitialised or the
/// story_id is not found.
pub fn sync_item_depends_on(story_id: &str) {
    let Some(db) = PIPELINE_DB.get() else {
        return;
    };
    let Some(view) = crate::crdt_state::read_item(story_id) else {
        return;
    };
    let depends_on = {
        let d = view.depends_on();
        if d.is_empty() {
            None
        } else {
            serde_json::to_string(d).ok()
        }
    };
    let msg = PipelineWriteMsg {
        story_id: story_id.to_string(),
        stage: view.stage().dir_name().to_string(),
        name: Some(view.name().to_string()),
        agent: view.agent().map(|a| a.to_string()),
        retry_count: Some(view.retry_count() as i64),
        depends_on,
        content: None,
    };
    let _ = db.tx.send(msg);
}

/// Get the next available item number by scanning the CRDT state, the
/// in-memory content store, AND the tombstone set for the highest existing
/// number.
///
/// Tombstoned IDs are excluded from `read_all_typed` (their CRDT entry is
/// `is_deleted`) and from `all_content_ids` (their content row is cleared by
/// `evict_item`).  Without consulting the tombstone set, the allocator can
/// hand out a tombstoned numeric ID; `crdt_state::write_item` would then
/// silently reject the new entry while the content store and SQLite shadow
/// happily accept it, producing a split-brain half-write (bug 1001).
pub fn next_item_number() -> u32 {
    let mut max_num: u32 = 0;

    let parse_leading_digits = |s: &str| -> Option<u32> {
        let num_str: String = s.chars().take_while(|c| c.is_ascii_digit()).collect();
        num_str.parse::<u32>().ok()
    };

    // Scan CRDT items via typed projection.
    for item in crate::pipeline_state::read_all_typed() {
        if let Some(n) = parse_leading_digits(&item.story_id.0)
            && n > max_num
        {
            max_num = n;
        }
    }

    // Also scan the content store (might have items not yet in CRDT).
    for id in all_content_ids() {
        if let Some(n) = parse_leading_digits(&id)
            && n > max_num
        {
            max_num = n;
        }
    }

    // Also scan tombstones — a tombstoned ID still poisons that slot because
    // crdt_state::write_item rejects writes for tombstoned IDs.  Without this
    // pass, the next allocated ID can collide with a tombstone and produce
    // a half-write (bug 1001).
    for id in crate::crdt_state::tombstoned_ids() {
        if let Some(n) = parse_leading_digits(&id)
            && n > max_num
        {
            max_num = n;
        }
    }

    max_num + 1
}

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

    /// `shadow_write::init` spawns its background task on the calling runtime.
    /// Under `#[tokio::test]` that runtime is per-test and drops when the test
    /// ends, killing the task.  This OnceLock holds a multi-thread runtime that
    /// persists for the lifetime of the test binary so the write loop stays alive
    /// across all tests that share `PIPELINE_DB`.
    static SHADOW_RT: std::sync::OnceLock<tokio::runtime::Runtime> = std::sync::OnceLock::new();

    async fn ensure_shadow_db() {
        static INIT: std::sync::OnceLock<()> = std::sync::OnceLock::new();
        if INIT.get().is_some() {
            return;
        }
        let rt = SHADOW_RT.get_or_init(|| {
            tokio::runtime::Builder::new_multi_thread()
                .worker_threads(1)
                .enable_all()
                .build()
                .expect("shadow rt")
        });
        rt.spawn(async {
            static INNER: std::sync::OnceLock<()> = std::sync::OnceLock::new();
            if INNER.get().is_some() {
                return;
            }
            let tmp = tempfile::tempdir().expect("tmp");
            let db_path = tmp.path().join("pipeline.db");
            std::mem::forget(tmp);
            shadow_write::init(&db_path).await.expect("shadow init");
            let _ = INNER.set(());
        })
        .await
        .expect("shadow init task");
        let _ = INIT.set(());
    }

    /// Regression test for story 1097: `set_depends_on` must sync the shadow
    /// table.  Before the fix, the CRDT register was updated but the
    /// `pipeline_items.depends_on` column was never written.
    #[tokio::test]
    async fn set_depends_on_syncs_shadow_table() {
        crate::crdt_state::init_for_test();
        ensure_content_store();
        ensure_shadow_db().await;

        let story_id = "1097_story_depends_on_shadow_drift";

        // Insert the story so it exists in both the CRDT and the shadow table.
        write_item_with_content(
            story_id,
            "backlog",
            "---\nname: Depends On Shadow Drift\n---\n",
            ItemMeta::named("Depends On Shadow Drift"),
        );

        // Let the initial shadow write land.
        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        // This is the write under test: it must update the shadow table.
        let ok = crate::crdt_state::set_depends_on(story_id, &[1, 2]);
        assert!(ok, "set_depends_on must return true for an existing item");

        // Let the shadow write land.
        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        let pool = shadow_write::get_shared_pool().expect("pool must be initialised");
        let row: (Option<String>,) =
            sqlx::query_as("SELECT depends_on FROM pipeline_items WHERE id = ?1")
                .bind(story_id)
                .fetch_one(pool)
                .await
                .expect("row must exist in shadow table");

        assert_eq!(
            row.0.as_deref(),
            Some("[1,2]"),
            "pipeline_items.depends_on must reflect the set_depends_on call"
        );
    }
}