package playlists

import (
	"context"
	"log/slog"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

// StartSystemPlaylistCron launches the in-process daily build loop in a
// goroutine. Caller passes a context that's cancelled on graceful shutdown.
//
// Lifecycle:
//  1. Clear any stale in_flight=true rows from a previously crashed process
//     (safe at startup: by definition, nothing is running yet).
//  2. Run once at startup so users catch up after a server restart without
//     waiting up to 24h.
//  3. Tick every 24h; runOnce on each tick.
//  4. Exit on context cancellation.
//
// Per-user errors are logged but don't halt the loop. Per-cycle errors (e.g.,
// "list active users" failed) are logged but the next tick still fires.
func StartSystemPlaylistCron(ctx context.Context, pool *pgxpool.Pool, logger *slog.Logger, dataDir string) {
	go func() {
		q := dbq.New(pool)
		if err := q.ClearStaleSystemPlaylistInFlight(ctx); err != nil {
			logger.Warn("system playlist cron: startup recovery failed", "err", err)
		}

		runOnce(ctx, pool, logger, dataDir)

		ticker := time.NewTicker(24 * time.Hour)
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				runOnce(ctx, pool, logger, dataDir)
			}
		}
	}()
}

func runOnce(ctx context.Context, pool *pgxpool.Pool, logger *slog.Logger, dataDir string) {
	q := dbq.New(pool)
	users, err := q.ListActiveUsersForSystemPlaylists(ctx)
	if err != nil {
		logger.Error("system playlist cron: list active users failed", "err", err)
		return
	}
	for _, userID := range users {
		if err := BuildSystemPlaylists(ctx, pool, logger, userID, time.Now(), dataDir); err != nil {
			logger.Warn("system playlist build failed in cron",
				"user_id", uuidStringPL(userID), "err", err)
		}
	}
}