package service

import (
	"bytes"
	"context"
	"time"

	"hyapp/pkg/appcode"
	"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"
	"hyapp/services/room-service/internal/router"
)

func (s *Service) mutateRoom(ctx context.Context, cmd command.Command, replayable bool, mutate func(now time.Time, current *state.RoomState, localRank *rank.LocalRank) (mutationResult, []outbox.Record, error)) (mutationResult, error) {
	startedAt := time.Now()
	var idempotencyMS int64
	var leaseMS int64
	var saveMutationMS int64
	var snapshotMS int64
	var projectionMS int64
	if cmd.RoomID() == "" || cmd.ID() == "" || cmd.ActorUserID() == 0 {
		// command meta 是幂等、路由、审计和权限判断的共同基础，缺一不可。
		return mutationResult{}, xerr.New(xerr.InvalidArgument, "command meta is incomplete")
	}
	if s.isDraining() {
		// 下线中的节点只让已经进入执行链路的命令收尾，不再接收新的 Room Cell 命令。
		return mutationResult{}, xerr.New(xerr.Unavailable, "room service is draining")
	}

	idempotencyStartedAt := time.Now()
	payload, seen, err := s.commandPayloadForIdempotency(ctx, cmd)
	idempotencyMS = elapsedMS(idempotencyStartedAt)
	if err != nil {
		return mutationResult{}, err
	}
	if seen {
		// 幂等命令不重新执行 mutate，也不会再次调用 wallet 或写 outbox。
		snapshot, err := s.currentSnapshot(ctx, cmd.RoomID())
		if err != nil {
			return mutationResult{}, err
		}

		return mutationResult{snapshot: snapshot}, nil
	}

	// 确保当前节点持有房间 lease，并在没有内存 Cell 时完成恢复。
	leaseStartedAt := time.Now()
	roomCell, lease, err := s.ensureCell(ctx, cmd.RoomID())
	leaseMS = elapsedMS(leaseStartedAt)
	if err != nil {
		return mutationResult{}, err
	}

	value, err := roomCell.Do(ctx, func(current *state.RoomState, currentRank *rank.LocalRank) (any, error) {
		// 在副本上执行命令，只有 command log/outbox 保存成功后才整体替换当前状态。
		nextState := current.Clone()
		nextRank := currentRank.Clone()
		now := s.clock.Now()

		result, outboxRecords, err := mutate(now, nextState, nextRank)
		if err != nil {
			// 校验、钱包或业务失败时不提交状态，不写 command log。
			return nil, err
		}

		if result.snapshot == nil {
			// 无特殊返回需求的命令默认返回变更后的快照。
			result.snapshot = nextState.ToProto()
		}
		result.snapshot = snapshotWithApp(ctx, result.snapshot)

		if result.snapshot.GetVersion() != current.Version {
			// 版本变化代表本命令产生实际状态变更，需要持久化命令和事件。
			if err := s.ensureLeaseStillOwned(ctx, cmd.RoomID(), lease); err != nil {
				return nil, err
			}
			saveStartedAt := time.Now()
			if err := s.repository.SaveMutation(ctx, MutationCommit{
				Command: CommandRecord{
					AppCode:     appcode.FromContext(ctx),
					RoomID:      cmd.RoomID(),
					RoomVersion: nextState.Version,
					CommandID:   cmd.ID(),
					CommandType: cmd.Type(),
					Payload:     commandPayloadForRecord(payload, result),
					Replayable:  replayable,
					OwnerNodeID: s.nodeID,
					LeaseToken:  lease.LeaseToken,
					CreatedAtMS: now.UnixMilli(),
				},
				OutboxRecords: outboxRecords,
				RoomStatus:    result.roomStatus,
				RoomSeatCount: result.roomSeatCount,
			}); err != nil {
				return nil, err
			}
			saveMutationMS += elapsedMS(saveStartedAt)
			// 保存已提交 outbox 记录，出 Cell 锁后由 outbox worker 异步投递 IM/activity，避免外部慢调用占住房间串行执行队列。
			result.outboxRecords = outboxRecords

			// 持久化成功后再替换内存状态，避免内存提交领先于恢复来源。
			current.ReplaceWith(nextState)
			currentRank.ReplaceWith(nextRank)
			result.snapshot = snapshotWithApp(ctx, current.ToProto())
			result.applied = true
		} else {
			// no-op 命令仍写入 command log，保证相同 command_id 重试可命中幂等，
			// 不同 payload 复用 command_id 会被后续入口拒绝为 CONFLICT。
			if err := s.ensureLeaseStillOwned(ctx, cmd.RoomID(), lease); err != nil {
				return nil, err
			}
			saveStartedAt := time.Now()
			if err := s.repository.SaveMutation(ctx, MutationCommit{
				Command: CommandRecord{
					AppCode:     appcode.FromContext(ctx),
					RoomID:      cmd.RoomID(),
					RoomVersion: current.Version,
					CommandID:   cmd.ID(),
					CommandType: cmd.Type(),
					Payload:     payload,
					Replayable:  false,
					OwnerNodeID: s.nodeID,
					LeaseToken:  lease.LeaseToken,
					CreatedAtMS: now.UnixMilli(),
				},
			}); err != nil {
				return nil, err
			}
			saveMutationMS += elapsedMS(saveStartedAt)
		}

		return result, nil
	})
	if err != nil {
		return mutationResult{}, err
	}

	result := value.(mutationResult)

	if result.applied && shouldSnapshot(result.snapshot, s.snapshotEveryN) {
		// 快照失败时返回错误，因为没有快照会增加恢复成本并可能影响 guard 查询。
		snapshotStartedAt := time.Now()
		if err := s.persistSnapshot(ctx, result.snapshot); err != nil {
			return mutationResult{}, err
		}
		snapshotMS = elapsedMS(snapshotStartedAt)
	}
	if result.applied {
		projectionStartedAt := time.Now()
		// 列表读模型最终一致，失败只记录日志，不回滚已经提交的 Room Cell 命令。
		s.projectRoomListBestEffort(ctx, result.snapshot)
		// 当前房间恢复读模型同样最终一致；权威校验仍以 Room Cell 快照为准。
		s.projectRoomPresenceBestEffort(ctx, result.snapshot)
		projectionMS = elapsedMS(projectionStartedAt)
	}

	logRoomCommandTiming(ctx, cmd.RoomID(), cmd.ID(), cmd.Type(), result.applied, elapsedMS(startedAt), idempotencyMS, leaseMS, saveMutationMS, snapshotMS, projectionMS, result.walletDebitMS, 0, 0, len(result.outboxRecords) > 0, result.syncEvent != nil)

	return result, nil
}

func (s *Service) commandPayloadForIdempotency(ctx context.Context, cmd command.Command) ([]byte, bool, error) {
	payload, err := command.Serialize(cmd)
	if err != nil {
		return nil, false, err
	}

	record, exists, err := s.repository.GetCommand(ctx, cmd.RoomID(), cmd.ID())
	if err != nil {
		return nil, false, err
	}
	if !exists {
		return payload, false, nil
	}
	currentIDPayload, err := command.IdempotencyPayload(payload)
	if err != nil {
		return nil, true, err
	}
	storedIDPayload, err := command.IdempotencyPayload(record.Payload)
	if err != nil {
		return nil, true, err
	}
	if record.CommandType != cmd.Type() || !bytes.Equal(storedIDPayload, currentIDPayload) {
		return nil, true, xerr.New(xerr.Conflict, "command_id payload conflict")
	}

	return payload, true, nil
}

func commandPayloadForRecord(defaultPayload []byte, result mutationResult) []byte {
	if len(result.commandPayload) > 0 {
		return result.commandPayload
	}
	return defaultPayload
}

func (s *Service) ensureLeaseStillOwned(ctx context.Context, roomID string, lease router.Lease) error {
	ok, err := s.directory.VerifyOwner(ctx, runtimeRoomKeyFromContext(ctx, roomID), s.nodeID, lease.LeaseToken, s.clock.Now())
	if err != nil {
		return err
	}
	if !ok {
		return xerr.New(xerr.Unavailable, "room lease is no longer owned by this node")
	}
	return nil
}

func elapsedMS(start time.Time) int64 {
	return time.Since(start).Milliseconds()
}