//! §4.5 M5: materialization of STATEFUL group trigger templates.
//!
//! A group-owned cron / queue / email trigger is a TEMPLATE that is never
//! dispatched directly (the scheduler / queue consumer / email webhook all
//! filter `t.app_id IS NOT NULL`). Instead this reconciler expands each template
//! into an app-owned copy — `materialized_from = template.id` — for every
//! descendant app, and removes copies whose (app, template) pair no longer
//! inherits. The copy owns its per-app state (cron `last_fired_at`, the queue
//! advisory lock), so the unchanged dispatch paths work against it as if it were
//! hand-authored. An EMAIL copy is a verbatim byte-copy of the group template's
//! sealed inbound secret — the group resolved + sealed it against its own store
//! once at apply (shared-group-secret model), and email secrets are v0/no-AAD so
//! the ciphertext is portable across rows; no master key is needed here.
//!
//! Full-live like `rebuild_route_table`: called at the same chokepoints (apply,
//! app create/delete, group reparent). A precise create/delete diff (not
//! delete-all-then-recreate) preserves `last_fired_at` on unchanged cron copies;
//! a DISABLED cron template keeps its copies (their `enabled` is synced off)
//! rather than deleting them, so a later re-enable resumes from the preserved
//! `last_fired_at` instead of firing from a fresh reference.
//!
//! Returns per-app WARNINGS (e.g. a queue whose consumer slot is already taken)
//! — the caller surfaces them; materialization of the other pairs still
//! proceeds.

use std::collections::HashSet;

use picloud_shared::AppId;
use sqlx::PgPool;
use uuid::Uuid;

/// The stateful kinds that materialize (M5.2 cron; M5.4 queue; M5.5 email).
const MATERIALIZED_KINDS: &[&str] = &["cron", "queue", "email"];

/// Fixed advisory-lock key serializing all materialization reconcilers (§4.5
/// M5). Two reconcilers running concurrently (e.g. two parallel app-creates)
/// would otherwise (a) read `should` and `existing` at different READ-COMMITTED
/// snapshots — a copy created by one between the two reads could be spuriously
/// DELETEd by the other (a lost cron copy that only self-heals on the next
/// mutation), and (b) both pass the queue one-consumer check and double-fill a
/// slot. An xact-scoped advisory lock makes each reconcile atomic w.r.t. the
/// others; reconciles are infrequent + fast, so serializing is cheap.
const REMATERIALIZE_LOCK_KEY: i64 = 0x0004_0005_0041_054d; // "M5" materialize marker

/// (descendant app, source template, kind) that SHOULD have a materialized copy.
#[derive(sqlx::FromRow)]
struct ShouldRow {
    effective_app_id: Uuid,
    template_id: Uuid,
    kind: String,
    /// §11.6 D3: a `shared` queue template's copies drain the GROUP store as
    /// COMPETING consumers, so the one-consumer-per-(app, queue) slot check is
    /// skipped for them (each descendant intentionally gets a consumer).
    shared: bool,
}

/// Reconcile all materialized stateful-template copies. Idempotent; safe to call
/// on every tree/apply mutation. Best-effort per pair — a pair that can't
/// materialize (queue slot taken, missing email secret) yields a warning and is
/// skipped, not an error.
pub async fn rematerialize_stateful_templates(pool: &PgPool) -> Result<Vec<String>, sqlx::Error> {
    let mut tx = pool.begin().await?;

    // Serialize reconcilers (see REMATERIALIZE_LOCK_KEY): the lock is held until
    // this transaction commits, so the `should`/`existing` reads below are
    // snapshot-consistent relative to any other reconcile and the queue slot
    // check can't race.
    sqlx::query("SELECT pg_advisory_xact_lock($1)")
        .bind(REMATERIALIZE_LOCK_KEY)
        .execute(&mut *tx)
        .await?;

    // Every (descendant app × ancestor-group stateful template) that should
    // exist — the all-apps `app_chain` CTE (each app × its ancestor chain) ⋈
    // group-owned stateful templates.
    let kinds: Vec<String> = MATERIALIZED_KINDS
        .iter()
        .map(|s| (*s).to_string())
        .collect();
    let should: Vec<ShouldRow> = sqlx::query_as(
        "WITH RECURSIVE app_chain AS ( \
             SELECT a.id AS effective_app_id, a.group_id AS owner_group, \
                    a.group_id AS next_group, 0 AS depth \
             FROM apps a WHERE a.group_id IS NOT NULL \
           UNION ALL \
             SELECT ac.effective_app_id, g.parent_id, g.parent_id, ac.depth + 1 \
             FROM groups g JOIN app_chain ac ON g.id = ac.next_group \
             WHERE ac.depth < 64 AND g.parent_id IS NOT NULL \
         ) \
         SELECT DISTINCT ac.effective_app_id, t.id AS template_id, t.kind, t.shared \
         FROM app_chain ac \
         JOIN triggers t ON t.group_id = ac.owner_group \
         WHERE t.group_id IS NOT NULL AND t.kind = ANY($1) \
           AND (t.enabled = TRUE OR t.kind = 'cron')",
    )
    .bind(&kinds)
    .fetch_all(&mut *tx)
    .await?;

    let should_set: HashSet<(Uuid, Uuid)> = should
        .iter()
        .map(|r| (r.effective_app_id, r.template_id))
        .collect();

    // Existing managed copies.
    let existing: Vec<(Uuid, Uuid)> = sqlx::query_as(
        "SELECT app_id, materialized_from FROM triggers WHERE materialized_from IS NOT NULL",
    )
    .fetch_all(&mut *tx)
    .await?;
    let existing_set: HashSet<(Uuid, Uuid)> = existing.iter().copied().collect();

    // Delete stale copies (template gone or app no longer a descendant).
    for (app_id, template_id) in &existing_set {
        if !should_set.contains(&(*app_id, *template_id)) {
            sqlx::query("DELETE FROM triggers WHERE app_id = $1 AND materialized_from = $2")
                .bind(app_id)
                .bind(template_id)
                .execute(&mut *tx)
                .await?;
        }
    }

    // Create missing copies.
    let mut warnings = Vec::new();
    for r in &should {
        if existing_set.contains(&(r.effective_app_id, r.template_id)) {
            continue;
        }
        if let Some(w) = materialize_one(
            &mut tx,
            r.effective_app_id,
            r.template_id,
            &r.kind,
            r.shared,
        )
        .await?
        {
            warnings.push(w);
        }
    }

    // Sync each CRON copy's `enabled` to its template's, in place. A cron
    // template's copies are kept across a disable (the `should` query includes
    // disabled cron templates), so a disable→re-enable toggles this flag rather
    // than delete+recreate — preserving each copy's per-app `last_fired_at` (and
    // its `created_at` reference). Without this, a re-enabled cron would reset to
    // a fresh reference and lose/shift its schedule state. Cron-only: queue/email
    // keep delete-on-disable so the queue one-consumer slot is freed on disable.
    sqlx::query(
        "UPDATE triggers c SET enabled = t.enabled \
         FROM triggers t \
         WHERE c.materialized_from = t.id AND t.kind = 'cron' AND c.enabled <> t.enabled",
    )
    .execute(&mut *tx)
    .await?;

    tx.commit().await?;
    Ok(warnings)
}

/// Create one app-owned copy of a group template + its per-kind detail. Returns
/// `Some(warning)` when the pair is intentionally skipped (e.g. a queue slot the
/// app already fills). `name` uses the column default (a fresh UUID) so it can't
/// collide with the app's own trigger names.
async fn materialize_one(
    tx: &mut sqlx::Transaction<'_, sqlx::Postgres>,
    app_id: Uuid,
    template_id: Uuid,
    kind: &str,
    shared: bool,
) -> Result<Option<String>, sqlx::Error> {
    // §M5.4: a per-app queue copy would violate the one-consumer-per-(app_id,
    // queue_name) invariant if the app already has a consumer on that queue —
    // skip with a warning. §11.6 D3: a SHARED queue copy drains the group store
    // as a competing consumer (a different store), so the slot check is skipped
    // — every descendant intentionally gets a consumer.
    if kind == "queue" && !shared {
        // Resolve the queue name so we can take the SAME per-(app, queue)
        // advisory lock the interactive `create_queue_trigger` uses. Without it,
        // this check-then-insert (serialized only against other reconcilers by
        // REMATERIALIZE_LOCK) could race an interactive consumer-create and
        // double-fill the slot — the two paths held different locks.
        let queue_name: Option<(String,)> =
            sqlx::query_as("SELECT queue_name FROM queue_trigger_details WHERE trigger_id = $1")
                .bind(template_id)
                .fetch_optional(&mut **tx)
                .await?;
        if let Some((queue_name,)) = queue_name {
            sqlx::query("SELECT pg_advisory_xact_lock($1)")
                .bind(crate::trigger_repo::advisory_lock_key(
                    AppId::from(app_id),
                    &queue_name,
                ))
                .execute(&mut **tx)
                .await?;
            let taken: Option<(Uuid,)> = sqlx::query_as(
                "SELECT t.id FROM triggers t \
                 JOIN queue_trigger_details d ON d.trigger_id = t.id \
                 WHERE t.app_id = $1 AND t.kind = 'queue' AND d.queue_name = $2",
            )
            .bind(app_id)
            .bind(&queue_name)
            .fetch_optional(&mut **tx)
            .await?;
            if taken.is_some() {
                return Ok(Some(format!(
                    "queue template not materialized for one app — it already has a \
                     consumer on that queue (app_id={app_id})"
                )));
            }
        }
    }

    // Parent row: copy the template's settings, owned by the app, linked back.
    // `ON CONFLICT DO NOTHING` (against the (app_id, materialized_from) partial
    // unique index) makes this idempotent under concurrent reconciles — the
    // loser gets no RETURNING row and skips the detail insert.
    let new_id: Option<(Uuid,)> = sqlx::query_as(
        "INSERT INTO triggers ( \
            app_id, script_id, kind, enabled, dispatch_mode, \
            retry_max_attempts, retry_backoff, retry_base_ms, \
            registered_by_principal, materialized_from) \
         SELECT $1, script_id, kind, enabled, dispatch_mode, \
                retry_max_attempts, retry_backoff, retry_base_ms, \
                registered_by_principal, id \
         FROM triggers WHERE id = $2 \
         ON CONFLICT DO NOTHING RETURNING id",
    )
    .bind(app_id)
    .bind(template_id)
    .fetch_optional(&mut **tx)
    .await?;
    let Some(new_id) = new_id else {
        // A concurrent reconcile already created this copy.
        return Ok(None);
    };

    match kind {
        "cron" => {
            // A first-ever copy starts with last_fired_at NULL → its reference
            // is created_at (now), so it fires at the next scheduled slot, not
            // immediately. Re-enabling a previously-materialized template does
            // NOT hit this path — that copy is kept and its `enabled` synced, so
            // last_fired_at survives (see the enabled-sync UPDATE above).
            sqlx::query(
                "INSERT INTO cron_trigger_details (trigger_id, schedule, timezone) \
                 SELECT $1, schedule, timezone FROM cron_trigger_details WHERE trigger_id = $2",
            )
            .bind(new_id.0)
            .bind(template_id)
            .execute(&mut **tx)
            .await?;
        }
        "queue" => {
            sqlx::query(
                "INSERT INTO queue_trigger_details \
                    (trigger_id, queue_name, visibility_timeout_secs) \
                 SELECT $1, queue_name, visibility_timeout_secs \
                 FROM queue_trigger_details WHERE trigger_id = $2",
            )
            .bind(new_id.0)
            .bind(template_id)
            .execute(&mut **tx)
            .await?;
        }
        "email" => {
            // §M5.5: the group template sealed its inbound HMAC secret against
            // the GROUP's own store once at apply (shared-group-secret model).
            // The secret's AAD (§M5.5 / audit H-D1) is bound to the GROUP owner,
            // NOT this copy's row, so a verbatim byte-copy stays openable — the
            // inbound path recovers the group via `materialized_from`. Copy the
            // version verbatim too. Each copy has its own trigger_id (its own
            // inbound webhook URL).
            sqlx::query(
                "INSERT INTO email_trigger_details \
                    (trigger_id, inbound_secret_encrypted, inbound_secret_nonce, \
                     inbound_secret_version) \
                 SELECT $1, inbound_secret_encrypted, inbound_secret_nonce, \
                        inbound_secret_version \
                 FROM email_trigger_details WHERE trigger_id = $2",
            )
            .bind(new_id.0)
            .bind(template_id)
            .execute(&mut **tx)
            .await?;
        }
        _ => {}
    }
    Ok(None)
}