package store

import (
	"context"
	"database/sql"
	"fmt"
	"time"

	"github.com/cosmic-clash/cosmic-clash/server/domain"
)

// ExpireStalledAllocationsSQL reclaims a match that has sat in
// ALLOCATING/PROCESS_READY/ASSIGNMENT_READY past the deadline -- its server
// crashed, was reclaimed by Agones as unhealthy, or otherwise never finished
// registering. Requeues every participant instead of just failing the match:
// task 8.50's own stated acceptance criterion is that "infrastructure-caused
// cases cannot penalise affected players", and a server-side failure here is
// exactly that, not player behaviour. FOR UPDATE SKIP LOCKED lets a second
// maintenance replica continue past whatever a concurrent one is already
// reclaiming rather than blocking on it.
const ExpireStalledAllocationsSQL = `WITH stalled AS (
    SELECT match_id FROM matches
    WHERE state IN ('ALLOCATING', 'PROCESS_READY', 'ASSIGNMENT_READY') AND created_at <= $1
    ORDER BY created_at, match_id
    LIMIT $2
    FOR UPDATE SKIP LOCKED
), failed AS (
    UPDATE matches SET state = 'FAILED', revision = revision + 1
    WHERE match_id IN (SELECT match_id FROM stalled)
    RETURNING match_id, revision
), released AS (
    UPDATE match_participants SET participation_active = FALSE
    WHERE match_id IN (SELECT match_id FROM failed) AND participation_active
    RETURNING ticket_id
), requeued AS (
    UPDATE queue_tickets SET state = 'QUEUED', expires_at = $3, revision = revision + 1
    WHERE ticket_id IN (SELECT ticket_id FROM released)
    RETURNING ticket_id
), events AS (
    INSERT INTO outbox (event_id, aggregate_type, aggregate_id, revision, event_type, payload)
    SELECT 'stalled-allocation:' || failed.match_id || ':' || failed.revision,
        'match', failed.match_id, failed.revision, 'state_changed',
        jsonb_build_object(
            'event', 'state_changed',
            'revision', failed.revision,
            'resource_id', failed.match_id,
            'occurred_at', $4,
            'state', 'FAILED',
            'match_id', failed.match_id,
            'player_ids', COALESCE((
                SELECT jsonb_agg(mp.player_id ORDER BY mp.player_id)
                FROM match_participants mp WHERE mp.match_id = failed.match_id
            ), '[]'::jsonb)
        )
    FROM failed
    ON CONFLICT DO NOTHING
)
SELECT (SELECT count(*) FROM failed), (SELECT count(*) FROM requeued), (SELECT count(*) FROM events)`

// ExpireStalledAllocations reclaims up to `limit` matches whose
// created_at is at or before `now - deadline` and are still stuck in one of
// the pre-live allocation states, failing the match and requeuing every
// participant's ticket with a fresh expiry rather than penalising them. It
// returns the number of matches reclaimed.
func ExpireStalledAllocations(ctx context.Context, db *sql.DB, now time.Time, deadline time.Duration, limit int) (int, error) {
	if db == nil || now.IsZero() || deadline <= 0 || limit < 1 || limit > 1000 {
		return 0, fmt.Errorf("invalid stalled-allocation maintenance arguments")
	}
	var matches, requeued, events int
	err := RunSerializable(ctx, db, DefaultSerializableAttempts, func(ctx context.Context, tx *sql.Tx) error {
		return tx.QueryRowContext(ctx, ExpireStalledAllocationsSQL, now.Add(-deadline), limit, now.Add(domain.QueueExpiryWindow), now).Scan(&matches, &requeued, &events)
	})
	if err != nil {
		return 0, err
	}
	if events != matches {
		return 0, fmt.Errorf("stalled-allocation outbox count %d does not match reclaimed matches %d", events, matches)
	}
	return matches, nil
}