package message

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

// StartLoops 启动到点分发、到期处理与小时清理循环。推送 worker 在握手时启动。
// 循环随 ctx 取消退出；停机等待由 L-03 调用 WaitLoops。
func (a *App) StartLoops(ctx context.Context) {
	a.loopWG.Add(3)
	go func() {
		defer a.loopWG.Done()
		a.dispatchLoop(ctx)
	}()
	go func() {
		defer a.loopWG.Done()
		a.expireLoop(ctx)
	}()
	go func() {
		defer a.loopWG.Done()
		a.purgeLoop(ctx)
	}()
}

// WaitLoops 等待 StartLoops 启动的 goroutine 退出。
func (a *App) WaitLoops() {
	a.loopWG.Wait()
}

func (a *App) dispatchLoop(ctx context.Context) {
	timer := time.NewTimer(time.Millisecond)
	defer timer.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-a.dispatchCh:
		case <-timer.C:
		}
		opCtx, cancel := context.WithTimeout(ctx, time.Second)
		nowMs := a.now().UnixMilli()
		if _, err := a.DispatchDue(opCtx, nowMs, 0); err != nil && ctx.Err() == nil {
			slog.Error("dispatch due", "err", err)
		}
		cancel()
		delay := time.Second
		if next, ok := a.earliestScheduled(ctx); ok {
			d := time.Until(time.UnixMilli(next))
			switch {
			case d < 0:
				d = 0
			case d > time.Minute:
				d = time.Minute
			}
			delay = d
		}
		if !timer.Stop() {
			select {
			case <-timer.C:
			default:
			}
		}
		timer.Reset(delay)
	}
}

func (a *App) expireLoop(ctx context.Context) {
	t := time.NewTicker(time.Second)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			opCtx, cancel := context.WithTimeout(ctx, time.Second)
			if err := a.ExpireOnce(opCtx, a.now().UnixMilli()); err != nil && ctx.Err() == nil {
				slog.Error("expire once", "err", err)
			}
			cancel()
		}
	}
}

func (a *App) purgeLoop(ctx context.Context) {
	t := time.NewTicker(time.Hour)
	defer t.Stop()
	run := func() {
		opCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
		if err := a.PurgeOnce(opCtx, a.now().UnixMilli()); err != nil && ctx.Err() == nil {
			slog.Error("purge once", "err", err)
		}
		cancel()
	}
	run()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			run()
		}
	}
}

func (a *App) earliestScheduled(ctx context.Context) (int64, bool) {
	if a.db == nil || a.db.Read == nil {
		return 0, false
	}
	var sendAt int64
	err := a.db.Read.QueryRowContext(ctx, `
SELECT MIN(send_at) FROM messages WHERE state = 'scheduled'`).Scan(&sendAt)
	if err != nil || sendAt == 0 {
		return 0, false
	}
	return sendAt, true
}