package service

import (
	"context"
	"strings"
	"time"

	roomeventsv1 "hyapp.local/api/proto/events/room/v1"
	roomv1 "hyapp.local/api/proto/room/v1"
	"hyapp/pkg/tencentim"
	"hyapp/pkg/xerr"
	"hyapp/services/room-service/internal/room/command"
	"hyapp/services/room-service/internal/room/outbox"
	"hyapp/services/room-service/internal/room/rank"
	"hyapp/services/room-service/internal/room/state"
)

const (
	// rtcEventAudioStarted 表示腾讯 RTC 侧观测到用户开始发布音频。
	rtcEventAudioStarted = "audio_started"
	// rtcEventAudioStopped 表示腾讯 RTC 侧观测到用户停止发布音频。
	rtcEventAudioStopped = "audio_stopped"
	// rtcEventRoomExited 表示用户离开 RTC 媒体房间，不等价于 App 业务离房。
	rtcEventRoomExited = "room_exited"
)

// ApplyRTCEvent 把已验签的腾讯 RTC 服务端事件落到 Room Cell。
func (s *Service) ApplyRTCEvent(ctx context.Context, req *roomv1.ApplyRTCEventRequest) (*roomv1.ApplyRTCEventResponse, error) {
	ctx = contextFromMeta(ctx, req.GetMeta())
	// gateway 负责验签和 user_id 映射，room-service 只处理可信且已标准化的媒体事件。
	cmd := command.ApplyRTCEvent{
		Base:            baseFromMeta(req.GetMeta()),
		TargetUserID:    req.GetTargetUserId(),
		EventType:       strings.TrimSpace(req.GetEventType()),
		EventTimeMS:     req.GetEventTimeMs(),
		Reason:          strings.TrimSpace(req.GetReason()),
		Source:          strings.TrimSpace(req.GetSource()),
		ExternalEventID: strings.TrimSpace(req.GetExternalEventId()),
	}
	if cmd.TargetUserID == 0 {
		// gateway 正常会显式传 target_user_id；兜底使用 actor 保持内部调用更易测试。
		cmd.TargetUserID = cmd.ActorUserID()
	}
	if cmd.Source == "" {
		cmd.Source = "rtc_webhook"
	}

	result, err := s.mutateRoom(ctx, cmd, true, func(now time.Time, current *state.RoomState, _ *rank.LocalRank) (mutationResult, []outbox.Record, error) {
		if cmd.TargetUserID <= 0 || cmd.EventType == "" || cmd.EventTimeMS <= 0 {
			// RTC 事件必须能定位用户、事件类型和事件时间，否则无法做乱序/旧事件过滤。
			return mutationResult{}, nil, xerr.New(xerr.InvalidArgument, "rtc event is incomplete")
		}

		// 不同 RTC 事件的业务语义不同：开始发布只确认麦位，停止发布释放麦位，退房只处理媒体状态。
		switch cmd.EventType {
		case rtcEventAudioStarted:
			return s.applyRTCAudioStarted(now, current, cmd)
		case rtcEventAudioStopped:
			return s.applyRTCAudioStopped(now, current, cmd)
		case rtcEventRoomExited:
			return s.applyRTCRoomExited(now, current, cmd)
		default:
			return mutationResult{}, nil, xerr.New(xerr.InvalidArgument, "rtc event type is unsupported")
		}
	})
	if err != nil {
		return nil, err
	}

	return &roomv1.ApplyRTCEventResponse{
		Result: commandResult(result.applied, result.snapshot.GetVersion(), s.clock.Now()),
		SeatNo: result.seatNo,
		Room:   result.snapshot,
	}, nil
}

// applyRTCAudioStarted 把当前 mic_session 从 pending_publish 确认为 publishing。
// 它只接受匹配当前麦位会话、未超时且时间更新的事件，腾讯回调重试或乱序事件都按 no-op 处理。
func (s *Service) applyRTCAudioStarted(now time.Time, current *state.RoomState, cmd command.ApplyRTCEvent) (mutationResult, []outbox.Record, error) {
	if err := requireActiveRoom(current); err != nil {
		return mutationResult{}, nil, err
	}
	if _, exists := current.OnlineUsers[cmd.TargetUserID]; !exists {
		// RTC 事件不拥有业务进房事实；用户不在业务 presence 时只忽略旧事件。
		return mutationResult{snapshot: current.ToProto()}, nil, nil
	}

	seat, exists := current.SeatByUser(cmd.TargetUserID)
	if !exists {
		// 用户不在麦上时，audio_started 只能是旧回调或客户端已经下麦后的迟到事件。
		return mutationResult{snapshot: current.ToProto()}, nil, nil
	}
	if !rtcEventMatchesCurrentMicSession(seat, cmd.EventTimeMS, s.micPublishTimeout) {
		// 会话不匹配、事件时间倒退或超过确认 deadline 时不能推进当前麦位状态。
		return mutationResult{snapshot: current.ToProto(), seatNo: seat.SeatNo}, nil, nil
	}
	if seat.PublishState == state.MicPublishPublishing {
		// 腾讯可能重试同一事件，已确认发流时保持幂等 no-op。
		return mutationResult{snapshot: current.ToProto(), seatNo: seat.SeatNo}, nil, nil
	}
	if seat.PublishState != state.MicPublishPending {
		// 非 pending 状态不应该被 audio_started 重新打开，避免旧事件复活已释放会话。
		return mutationResult{snapshot: current.ToProto(), seatNo: seat.SeatNo}, nil, nil
	}

	// 只有通过所有防旧校验后，才把麦位推进到 publishing 并记录最新媒体事件时间。
	index := current.SeatIndex(seat.SeatNo)
	current.MicSeats[index].PublishState = state.MicPublishPublishing
	current.MicSeats[index].LastPublishEventTimeMS = cmd.EventTimeMS
	current.MicSeats[index].MicHeartbeatAtMS = now.UnixMilli()
	current.Version++
	seatStatus := current.MicSeats[index].SeatStatus()

	micEvent, err := outbox.Build(current.RoomID, "RoomMicChanged", current.Version, now, &roomeventsv1.RoomMicChanged{
		ActorUserId:        cmd.ActorUserID(),
		TargetUserId:       cmd.TargetUserID,
		FromSeat:           seat.SeatNo,
		ToSeat:             seat.SeatNo,
		Action:             "publish_confirmed",
		MicSessionId:       seat.MicSessionID,
		PublishState:       state.MicPublishPublishing,
		PublishDeadlineMs:  seat.PublishDeadlineMS,
		PublishEventTimeMs: cmd.EventTimeMS,
		MicMuted:           current.MicSeats[index].MicMuted,
		SeatStatus:         seatStatus,
	})
	if err != nil {
		return mutationResult{}, nil, err
	}

	return mutationResult{
		snapshot: current.ToProto(),
		seatNo:   seat.SeatNo,
		syncEvent: &tencentim.RoomEvent{
			EventID:      micEvent.EventID,
			RoomID:       current.RoomID,
			EventType:    "room_mic_publish_confirmed",
			ActorUserID:  cmd.ActorUserID(),
			TargetUserID: cmd.TargetUserID,
			SeatNo:       seat.SeatNo,
			RoomVersion:  current.Version,
			Attributes: map[string]string{
				"action":                "publish_confirmed",
				"publish_state":         state.MicPublishPublishing,
				"mic_session_id":        seat.MicSessionID,
				"publish_event_time_ms": int64String(cmd.EventTimeMS),
				"source":                cmd.Source,
				"external_event_id":     cmd.ExternalEventID,
				"mic_muted":             boolString(current.MicSeats[index].MicMuted),
				"seat_status":           seatStatus,
			},
		},
	}, []outbox.Record{micEvent}, nil
}

// applyRTCAudioStopped 释放当前 mic_session 占用的麦位。
// 停止发布事件不检查业务 presence，因为 RTC 退流可能先于 LeaveRoom 或 stale 清理到达。
func (s *Service) applyRTCAudioStopped(now time.Time, current *state.RoomState, cmd command.ApplyRTCEvent) (mutationResult, []outbox.Record, error) {
	seat, exists := current.SeatByUser(cmd.TargetUserID)
	if !exists {
		// 麦位已释放时，迟到的停止发布事件按 no-op 收敛。
		return mutationResult{snapshot: current.ToProto()}, nil, nil
	}
	if !rtcStopEventMatchesCurrentMicSession(seat, cmd.EventTimeMS, s.micPublishTimeout) {
		// 旧事件不能释放新 mic_session，防止用户快速重上麦时被迟到 webhook 踢下。
		return mutationResult{snapshot: current.ToProto(), seatNo: seat.SeatNo}, nil, nil
	}

	// 清麦和 RoomMicChanged/down 必须同版本提交，给时长聚合一个稳定闭合点。
	index := current.SeatIndex(seat.SeatNo)
	micSessionID := current.MicSeats[index].MicSessionID
	current.ClearMicSession(index)
	current.Version++
	seatStatus := current.MicSeats[index].SeatStatus()

	micEvent, err := outbox.Build(current.RoomID, "RoomMicChanged", current.Version, now, &roomeventsv1.RoomMicChanged{
		ActorUserId:        cmd.ActorUserID(),
		TargetUserId:       cmd.TargetUserID,
		FromSeat:           seat.SeatNo,
		ToSeat:             0,
		Action:             "down",
		MicSessionId:       micSessionID,
		PublishState:       state.MicPublishIdle,
		Reason:             cmd.Reason,
		PublishEventTimeMs: cmd.EventTimeMS,
		SeatStatus:         seatStatus,
	})
	if err != nil {
		return mutationResult{}, nil, err
	}

	return mutationResult{
		snapshot: current.ToProto(),
		seatNo:   seat.SeatNo,
		syncEvent: &tencentim.RoomEvent{
			EventID:      micEvent.EventID,
			RoomID:       current.RoomID,
			EventType:    "room_mic_down",
			ActorUserID:  cmd.ActorUserID(),
			TargetUserID: cmd.TargetUserID,
			SeatNo:       seat.SeatNo,
			RoomVersion:  current.Version,
			Attributes: map[string]string{
				"action":                "down",
				"publish_state":         state.MicPublishIdle,
				"mic_session_id":        micSessionID,
				"reason":                cmd.Reason,
				"publish_event_time_ms": int64String(cmd.EventTimeMS),
				"source":                cmd.Source,
				"external_event_id":     cmd.ExternalEventID,
				"seat_status":           seatStatus,
			},
		},
	}, []outbox.Record{micEvent}, nil
}

// applyRTCRoomExited 只处理 RTC 媒体房间退出事实，不删除 room-service 业务 presence。
func (s *Service) applyRTCRoomExited(now time.Time, current *state.RoomState, cmd command.ApplyRTCEvent) (mutationResult, []outbox.Record, error) {
	if user, exists := current.OnlineUsers[cmd.TargetUserID]; exists && user.LastSeenAtMS > cmd.EventTimeMS {
		// 腾讯可能重试或延迟投递旧退房事件；如果业务 presence 已被更新到事件之后，保留当前重连和麦位状态。
		return mutationResult{snapshot: current.ToProto()}, nil, nil
	}

	_, onSeat := current.SeatByUser(cmd.TargetUserID)
	if !onSeat {
		// RTC 退房只代表媒体频道状态，不拥有 room-service 业务 presence。
		return mutationResult{snapshot: current.ToProto()}, nil, nil
	}

	// 用户仍可能停留在房间页继续重连；这里只释放当前 mic_session，业务离房只能由 LeaveRoom、kick、close 或 stale worker 触发。
	return s.applyRTCAudioStopped(now, current, cmd)
}

// rtcEventMatchesCurrentMicSession 校验音频开始事件是否仍属于当前 pending mic_session。
func rtcEventMatchesCurrentMicSession(seat state.MicSeat, eventTimeMS int64, timeout time.Duration) bool {
	if !rtcStopEventMatchesCurrentMicSession(seat, eventTimeMS, timeout) {
		return false
	}
	if eventTimeMS <= seat.LastPublishEventTimeMS {
		// audio_started 必须晚于已接受发布水位，防止腾讯重试或乱序开始事件反复推进状态。
		return false
	}
	if seat.PublishDeadlineMS > 0 && eventTimeMS > seat.PublishDeadlineMS {
		// audio_started 过了确认 deadline 不再接受，超时 worker 会按 mic_session_id 释放麦位。
		return false
	}

	return true
}

// rtcStopEventMatchesCurrentMicSession 校验停止/退房事件是否能作用于当前 mic_session。
func rtcStopEventMatchesCurrentMicSession(seat state.MicSeat, eventTimeMS int64, timeout time.Duration) bool {
	if seat.MicSessionID == "" {
		// 没有会话时，停止/退房事件只能是旧回调。
		return false
	}
	if createdAtMS := rtcMicSessionCreatedAtMS(seat, timeout); createdAtMS > 0 && eventTimeMS < createdAtMS {
		// 小于会话创建时间的 webhook 一定属于旧会话。
		return false
	}

	return true
}

// rtcMicSessionCreatedAtMS 从发布 deadline 反推出会话创建时间，用于过滤旧 RTC 事件。
func rtcMicSessionCreatedAtMS(seat state.MicSeat, timeout time.Duration) int64 {
	timeoutMS := timeout.Milliseconds()
	if seat.PublishDeadlineMS <= 0 || timeoutMS <= 0 {
		// 没有 deadline 或 timeout 配置时无法反推创建时间，调用方只能使用事件时间递增校验。
		return 0
	}

	return seat.PublishDeadlineMS - timeoutMS
}