package service

import (
	"context"
	"fmt"
	"log/slog"
	"strings"
	"sync"
	"time"

	"hyapp/pkg/appcode"
	"hyapp/pkg/logx"
	"hyapp/services/room-service/internal/room/outbox"
)

const (
	// outboxRetryExponentialBackoff 是房间事件补偿的默认策略，避免外部故障时每秒刷同一条错误。
	outboxRetryExponentialBackoff = "exponential_backoff"
	// outboxWorkerName 固定写入日志，便于后续按 worker 聚合检索。
	outboxWorkerName = "room_outbox"
	// robotOutboxWorkerName 固定标识机器人展示事件通道，避免和主 room_outbox 监控混淆。
	robotOutboxWorkerName = "room_robot_outbox"
)

// OutboxWorkerOptions 控制 room_outbox pending 事件的持续补偿循环。
type OutboxWorkerOptions struct {
	// PollInterval 是两轮 pending 扫描之间的间隔；非正数会被归一到安全默认值。
	PollInterval time.Duration
	// BatchSize 是单轮最多处理条数；非正数会被归一，避免全表扫描。
	BatchSize int
	// Concurrency 是本进程内独立抢占 pending outbox 的 worker 数；每条 worker 都依赖 MySQL SKIP LOCKED 隔离批次。
	Concurrency int
	// PublishTimeout 限制单条外部投递耗时，shutdown 时当前事件最多阻塞该时长。
	PublishTimeout time.Duration
	// RetryStrategy 当前只支持 exponential_backoff。
	RetryStrategy string
	// MaxRetryCount 是转入 failed 前允许的最大失败次数。
	MaxRetryCount int
	// InitialBackoff 是首次失败后的等待时间。
	InitialBackoff time.Duration
	// MaxBackoff 是指数退避上限。
	MaxBackoff time.Duration
	// WorkerID 写入 outbox worker_id，空值时使用节点 ID；并发启动时会自动带上序号。
	WorkerID string
	// WorkerName 写入日志 worker 字段，空值时使用主通道或机器人通道的稳定名称。
	WorkerName string
	// StaleDiscardAfter 只用于 robot outbox；超过该窗口的展示事件直接删除，不再补发 MQ/IM。
	StaleDiscardAfter time.Duration
	// CleanupInterval 控制 robot outbox 后台清理频率；非正数表示不启动清理。
	CleanupInterval time.Duration
	// CleanupActiveAfter 控制 pending/retryable/delivering 机器人展示事件的最大保留时长。
	CleanupActiveAfter time.Duration
	// CleanupTerminalAfter 控制 delivered/failed 机器人展示事件的最大保留时长。
	CleanupTerminalAfter time.Duration
	// CleanupBatchSize 控制单轮清理最多删除多少行，避免长事务拖慢主库。
	CleanupBatchSize int
}

func defaultOutboxWorkerOptions() OutboxWorkerOptions {
	// 默认值优先避免 busy loop、无限重试和日志污染。
	return OutboxWorkerOptions{
		PollInterval:   time.Second,
		BatchSize:      100,
		Concurrency:    1,
		PublishTimeout: 3 * time.Second,
		RetryStrategy:  outboxRetryExponentialBackoff,
		MaxRetryCount:  10,
		InitialBackoff: 5 * time.Second,
		MaxBackoff:     5 * time.Minute,
	}
}

func normalizeOutboxWorkerOptions(options OutboxWorkerOptions) OutboxWorkerOptions {
	// worker 层再次归一化，防止测试或手动构造绕过 config.Normalize。
	defaults := defaultOutboxWorkerOptions()
	if options.PollInterval <= 0 {
		// 非正间隔不能直接传给 ticker，否则会 panic 或形成忙循环。
		options.PollInterval = defaults.PollInterval
	}
	if options.BatchSize <= 0 {
		// 非正批量按安全默认值处理，避免 repository 扫描不受控。
		options.BatchSize = defaults.BatchSize
	}
	if options.Concurrency <= 0 {
		// 并发数为 0 等价于历史单 worker，避免老测试或手工构造配置意外关闭补偿。
		options.Concurrency = defaults.Concurrency
	}
	if options.PublishTimeout <= 0 {
		// 单条外部投递必须有 deadline，shutdown 才能等待有界。
		options.PublishTimeout = defaults.PublishTimeout
	}
	if options.MaxRetryCount <= 0 {
		options.MaxRetryCount = defaults.MaxRetryCount
	}
	if options.InitialBackoff <= 0 {
		options.InitialBackoff = defaults.InitialBackoff
	}
	if options.MaxBackoff <= 0 {
		options.MaxBackoff = defaults.MaxBackoff
	}
	if options.MaxBackoff < options.InitialBackoff {
		options.MaxBackoff = options.InitialBackoff
	}
	if options.CleanupBatchSize <= 0 && (options.CleanupActiveAfter > 0 || options.CleanupTerminalAfter > 0) {
		// robot outbox 清理开启时必须有批量上限；默认 5 万和线上一次性清理批量保持一致。
		options.CleanupBatchSize = 50000
	}
	options.RetryStrategy = strings.TrimSpace(options.RetryStrategy)
	if options.RetryStrategy == "" {
		// 空策略按指数退避处理，保持和配置默认值一致。
		options.RetryStrategy = defaults.RetryStrategy
	}

	return options
}

// RunOutboxWorker 持续扫描 pending outbox；它不执行房间命令，只投递已持久化事件。
func (s *Service) RunOutboxWorker(ctx context.Context, options OutboxWorkerOptions) {
	s.runOutboxWorker(ctx, options, outboxWorkerName, s.ProcessPendingOutbox)
}

// RunRobotOutboxWorker 持续扫描机器人房间展示 outbox；它和主 room_outbox 完全分开抢占。
func (s *Service) RunRobotOutboxWorker(ctx context.Context, options OutboxWorkerOptions) {
	s.runOutboxWorker(ctx, options, robotOutboxWorkerName, s.ProcessPendingRobotOutbox)
}

func (s *Service) runOutboxWorker(ctx context.Context, options OutboxWorkerOptions, workerName string, process func(context.Context, OutboxWorkerOptions) error) {
	options = normalizeOutboxWorkerOptions(options)
	if options.RetryStrategy != outboxRetryExponentialBackoff {
		// 配置层会拒绝未知策略；这里兜底避免测试或手写构造静默改变语义。
		logx.Error(ctx, "worker_stopped", fmt.Errorf("unsupported retry_strategy"), slog.String("worker", workerName), slog.String("node_id", s.nodeID))
		return
	}
	if options.Concurrency == 1 {
		// 单 worker 保持历史 worker_id 和日志名称，避免线上排障查询字段无意义变化。
		options.WorkerID = firstNonEmpty(strings.TrimSpace(options.WorkerID), s.nodeID)
		options.WorkerName = firstNonEmpty(strings.TrimSpace(options.WorkerName), workerName)
		s.runOutboxWorkerLoop(ctx, options, process)
		return
	}

	var wg sync.WaitGroup
	for index := 1; index <= options.Concurrency; index++ {
		workerOptions := options
		// 多 worker 共用同一个进程上下文，但必须写不同 worker_id，方便从 delivering 记录定位卡住的协程。
		workerOptions.WorkerName = fmt.Sprintf("%s-%02d", workerName, index)
		workerOptions.WorkerID = fmt.Sprintf("%s/%s", s.nodeID, workerOptions.WorkerName)
		wg.Add(1)
		go func() {
			defer wg.Done()
			s.runOutboxWorkerLoop(ctx, workerOptions, process)
		}()
	}
	wg.Wait()
}

func (s *Service) runOutboxWorkerLoop(ctx context.Context, options OutboxWorkerOptions, process func(context.Context, OutboxWorkerOptions) error) {
	workerName := firstNonEmpty(strings.TrimSpace(options.WorkerName), outboxWorkerName)
	// 启动后先执行一轮，避免服务刚恢复时还要等一个 poll interval 才补偿历史事件。
	if err := process(ctx, options); err != nil && ctx.Err() == nil {
		logx.Error(ctx, "worker_batch_failed", err, slog.String("worker", workerName), slog.String("node_id", s.nodeID), slog.Int("batch_size", options.BatchSize))
	}

	ticker := time.NewTicker(options.PollInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if err := process(ctx, options); err != nil && ctx.Err() == nil {
				logx.Error(ctx, "worker_batch_failed", err, slog.String("worker", workerName), slog.String("node_id", s.nodeID), slog.Int("batch_size", options.BatchSize))
			}
		}
	}
}

// ProcessPendingOutbox 把待投递事件补偿性地推送给异步消费者。
func (s *Service) ProcessPendingOutbox(ctx context.Context, options OutboxWorkerOptions) error {
	workerName := firstNonEmpty(strings.TrimSpace(options.WorkerName), outboxWorkerName)
	return s.processPendingOutbox(ctx, options, workerName, false)
}

// ProcessPendingRobotOutbox 把机器人展示事件补偿性地推送给独立机器人异步消费者。
func (s *Service) ProcessPendingRobotOutbox(ctx context.Context, options OutboxWorkerOptions) error {
	workerName := firstNonEmpty(strings.TrimSpace(options.WorkerName), robotOutboxWorkerName)
	if err := s.maybeCleanupRobotOutbox(ctx, normalizeOutboxWorkerOptions(options)); err != nil {
		return err
	}
	return s.processPendingOutbox(ctx, options, workerName, true)
}

func (s *Service) processPendingOutbox(ctx context.Context, options OutboxWorkerOptions, workerName string, robotLane bool) error {
	options = normalizeOutboxWorkerOptions(options)
	if options.RetryStrategy != outboxRetryExponentialBackoff {
		return fmt.Errorf("unsupported outbox retry_strategy %q", options.RetryStrategy)
	}

	// 补偿 worker 先抢占 pending/retryable 事件，再投递，避免多机同时处理同一批。
	records, err := s.claimPendingOutbox(ctx, robotLane, options)
	if err != nil {
		return err
	}

	for _, record := range records {
		select {
		case <-ctx.Done():
			// 退出时不再领取新事件；已抢占但未处理完的事件会在 lock_until_ms 到期后重新可见。
			return ctx.Err()
		default:
		}
		if robotLane && staleRobotOutboxRecord(record, options.StaleDiscardAfter) {
			// 机器人展示事件超过 TTL 后再补发会制造“迟到礼物”体验，直接删除并释放 MQ/IM 资源。
			deleteCtx, deleteCancel := context.WithTimeout(appcode.WithContext(context.Background(), record.AppCode), options.PublishTimeout)
			deleteErr := s.repository.DeleteRobotOutbox(deleteCtx, record.EventID)
			deleteCancel()
			if deleteErr != nil {
				return deleteErr
			}
			logx.Warn(ctx, "robot_outbox_stale_discarded",
				slog.String("worker", workerName),
				slog.String("node_id", s.nodeID),
				slog.String("event_id", record.EventID),
				slog.String("event_type", record.EventType),
				slog.String("room_id", record.RoomID),
				slog.Int64("created_at_ms", record.CreatedAtMS),
				slog.Int64("stale_discard_after_ms", options.StaleDiscardAfter.Milliseconds()),
			)
			continue
		}
		if record.RetryCount >= options.MaxRetryCount {
			// 已达到最大失败次数的历史事件直接转死信，防止每轮 worker 继续打外部系统。
			markCtx, markCancel := context.WithTimeout(appcode.WithContext(context.Background(), record.AppCode), options.PublishTimeout)
			markErr := s.markOutboxDead(markCtx, robotLane, record.EventID, deadLetterReason(record))
			markCancel()
			if markErr != nil {
				return markErr
			}
			logx.Error(ctx, "outbox_dead_letter", nil,
				slog.String("worker", workerName),
				slog.String("node_id", s.nodeID),
				slog.String("event_id", record.EventID),
				slog.String("event_type", record.EventType),
				slog.String("room_id", record.RoomID),
				slog.Int("retry_count", record.RetryCount),
				slog.String("last_error", trimOutboxError(record.LastError)),
			)
			continue
		}

		publishCtx, cancel := context.WithTimeout(appcode.WithContext(context.Background(), record.AppCode), options.PublishTimeout)
		// 发布上下文不继承 worker ctx，避免 shutdown 取消导致已开始的单条外部投递无界处于未知状态。
		err := s.publishOutboxRecord(publishCtx, record, robotLane)
		cancel()
		if err != nil {
			// 投递失败转为 retryable，并写入指数退避时间，等待下一轮 worker 到期后再抢占。
			nextRetryAtMS := time.Now().UTC().Add(outboxBackoff(record.RetryCount+1, options)).UnixMilli()
			markCtx, markCancel := context.WithTimeout(appcode.WithContext(context.Background(), record.AppCode), options.PublishTimeout)
			markErr := s.markOutboxRetryable(markCtx, robotLane, record.EventID, trimOutboxError(err.Error()), nextRetryAtMS)
			markCancel()
			if markErr != nil {
				return markErr
			}

			logx.Warn(ctx, "outbox_publish_retryable",
				slog.String("worker", workerName),
				slog.String("node_id", s.nodeID),
				slog.String("event_id", record.EventID),
				slog.String("event_type", record.EventType),
				slog.String("room_id", record.RoomID),
				slog.Int("retry_count", record.RetryCount+1),
				slog.Int64("next_retry_at_ms", nextRetryAtMS),
				slog.String("error", trimOutboxError(err.Error())),
			)
			continue
		}

		// 只有外部发布成功后才能标记 delivered。
		markCtx, markCancel := context.WithTimeout(appcode.WithContext(context.Background(), record.AppCode), options.PublishTimeout)
		markErr := s.markOutboxDelivered(markCtx, robotLane, record.EventID)
		markCancel()
		if markErr != nil {
			return markErr
		}

		logx.Info(ctx, "outbox_delivered",
			slog.String("worker", workerName),
			slog.String("node_id", s.nodeID),
			slog.String("event_id", record.EventID),
			slog.String("event_type", record.EventType),
			slog.String("room_id", record.RoomID),
			slog.Int("retry_count", record.RetryCount),
		)
	}

	return nil
}

func (s *Service) maybeCleanupRobotOutbox(ctx context.Context, options OutboxWorkerOptions) error {
	if s == nil || s.repository == nil || options.CleanupInterval <= 0 || (options.CleanupActiveAfter <= 0 && options.CleanupTerminalAfter <= 0) {
		return nil
	}

	now := time.Now().UTC()
	s.robotOutboxCleanupMu.Lock()
	if !s.robotOutboxLastCleanup.IsZero() && now.Sub(s.robotOutboxLastCleanup) < options.CleanupInterval {
		s.robotOutboxCleanupMu.Unlock()
		return nil
	}
	// 先记录本次尝试时间，避免多 worker 或异常重试在同一秒内反复打 DELETE。
	s.robotOutboxLastCleanup = now
	s.robotOutboxCleanupMu.Unlock()

	var activeBeforeMS int64
	if options.CleanupActiveAfter > 0 {
		activeBeforeMS = now.Add(-options.CleanupActiveAfter).UnixMilli()
	}
	var terminalBeforeMS int64
	if options.CleanupTerminalAfter > 0 {
		terminalBeforeMS = now.Add(-options.CleanupTerminalAfter).UnixMilli()
	}
	cleanupCtx, cancel := context.WithTimeout(appcode.WithContext(context.Background(), appcode.FromContext(ctx)), options.PublishTimeout)
	activeDeleted, terminalDeleted, err := s.repository.CleanupRobotOutbox(cleanupCtx, activeBeforeMS, terminalBeforeMS, options.CleanupBatchSize)
	cancel()
	if err != nil {
		return err
	}
	if activeDeleted > 0 || terminalDeleted > 0 {
		logx.Info(ctx, "robot_outbox_cleanup_deleted",
			slog.String("worker", robotOutboxWorkerName),
			slog.String("node_id", s.nodeID),
			slog.Int64("active_deleted", activeDeleted),
			slog.Int64("terminal_deleted", terminalDeleted),
			slog.Int("batch_size", options.CleanupBatchSize),
		)
	}
	return nil
}

func staleRobotOutboxRecord(record outbox.Record, ttl time.Duration) bool {
	if ttl <= 0 || record.CreatedAtMS <= 0 {
		return false
	}
	// 使用当前 UTC 毫秒判断 TTL，和 outbox created_at_ms 的持久化口径保持一致。
	return time.Now().UTC().UnixMilli()-record.CreatedAtMS >= ttl.Milliseconds()
}

func (s *Service) claimPendingOutbox(ctx context.Context, robotLane bool, options OutboxWorkerOptions) ([]outbox.Record, error) {
	lockUntilMS := time.Now().UTC().Add(options.PublishTimeout).UnixMilli()
	workerID := firstNonEmpty(strings.TrimSpace(options.WorkerID), s.nodeID)
	if robotLane {
		return s.repository.ClaimPendingRobotOutbox(ctx, workerID, options.BatchSize, lockUntilMS)
	}
	return s.repository.ClaimPendingOutbox(ctx, workerID, options.BatchSize, lockUntilMS)
}

func (s *Service) markOutboxDelivered(ctx context.Context, robotLane bool, eventID string) error {
	if robotLane {
		return s.repository.MarkRobotOutboxDelivered(ctx, eventID)
	}
	return s.repository.MarkOutboxDelivered(ctx, eventID)
}

func (s *Service) markOutboxRetryable(ctx context.Context, robotLane bool, eventID string, lastErr string, nextRetryAtMS int64) error {
	if robotLane {
		return s.repository.MarkRobotOutboxRetryable(ctx, eventID, lastErr, nextRetryAtMS)
	}
	return s.repository.MarkOutboxRetryable(ctx, eventID, lastErr, nextRetryAtMS)
}

func (s *Service) markOutboxDead(ctx context.Context, robotLane bool, eventID string, lastErr string) error {
	if robotLane {
		return s.repository.MarkRobotOutboxDead(ctx, eventID, lastErr)
	}
	return s.repository.MarkOutboxDead(ctx, eventID, lastErr)
}

func (s *Service) publishOutboxRecord(ctx context.Context, record outbox.Record, robotLane bool) error {
	// Ignited 先安排延迟发射，再对外广播事件；如果 MQ 延迟调度不可用，本条 outbox 保持 retryable。
	if err := s.scheduleRoomRocketLaunchFromEnvelope(ctx, record.Envelope); err != nil {
		return err
	}
	if robotLane {
		if s.robotOutboxPublisher == nil {
			return nil
		}
		return s.robotOutboxPublisher.PublishOutboxEvent(ctx, record.Envelope)
	}
	if s.outboxPublisher == nil {
		return nil
	}
	return s.outboxPublisher.PublishOutboxEvent(ctx, record.Envelope)
}

// outboxBackoff 根据失败次数计算指数退避，且永远不超过 MaxBackoff。
func outboxBackoff(retryCount int, options OutboxWorkerOptions) time.Duration {
	if retryCount <= 1 {
		return options.InitialBackoff
	}
	backoff := options.InitialBackoff
	for i := 1; i < retryCount; i++ {
		if backoff >= options.MaxBackoff/2 {
			// 提前截断，避免 duration 乘 2 溢出或超过配置上限。
			return options.MaxBackoff
		}
		backoff *= 2
	}
	if backoff > options.MaxBackoff {
		return options.MaxBackoff
	}
	return backoff
}

// deadLetterReason 生成写入 failed 状态的稳定错误原因。
func deadLetterReason(record outbox.Record) string {
	if strings.TrimSpace(record.LastError) == "" {
		return "outbox retry limit exceeded"
	}
	return trimOutboxError("outbox retry limit exceeded: " + record.LastError)
}

func trimOutboxError(value string) string {
	// last_error 会写入 MySQL 和日志，先去掉首尾空白避免不可见差异影响排障。
	value = strings.TrimSpace(value)
	if len(value) <= 512 {
		return value
	}

	// V1 只保留错误前缀，避免外部响应过大撑爆日志或 TEXT 字段查询成本。
	return value[:512]
}

func firstNonEmpty(values ...string) string {
	for _, value := range values {
		if strings.TrimSpace(value) != "" {
			return strings.TrimSpace(value)
		}
	}
	return ""
}