package task

import (
	"context"
	"fmt"
	"os"

	"github.com/hibiken/asynq"
	"github.com/redis/go-redis/v9"
	"go.uber.org/zap"

	"github.com/break/junhong_cmp_fiber/internal/exporter"
	"github.com/break/junhong_cmp_fiber/internal/store/postgres"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
	"github.com/break/junhong_cmp_fiber/pkg/storage"
)

// ExportFinalizeHandler 导出 finalize 处理器。
type ExportFinalizeHandler struct {
	redis         *redis.Client
	taskStore     *postgres.ExportTaskStore
	shardStore    *postgres.ExportShardTaskStore
	storageSvc    *storage.Service
	sceneRegistry *exporter.Registry
	logger        *zap.Logger
}

// NewExportFinalizeHandler 创建导出 finalize 处理器。
func NewExportFinalizeHandler(
	redis *redis.Client,
	taskStore *postgres.ExportTaskStore,
	shardStore *postgres.ExportShardTaskStore,
	storageSvc *storage.Service,
	sceneRegistry *exporter.Registry,
	logger *zap.Logger,
) *ExportFinalizeHandler {
	return &ExportFinalizeHandler{
		redis:         redis,
		taskStore:     taskStore,
		shardStore:    shardStore,
		storageSvc:    storageSvc,
		sceneRegistry: sceneRegistry,
		logger:        logger,
	}
}

// HandleExportFinalize 处理导出 finalize 任务。
func (h *ExportFinalizeHandler) HandleExportFinalize(ctx context.Context, task *asynq.Task) error {
	var payload ExportFinalizePayload
	if err := parseExportPayload(task.Payload(), &payload); err != nil {
		h.logger.Error("解析导出 finalize 任务载荷失败", zap.Error(err))
		return asynq.SkipRetry
	}

	lockKey := constants.RedisExportFinalizeLockKey(payload.TaskID)
	locked, err := tryAcquireLock(ctx, h.redis, lockKey, exportFinalizeLockTTL)
	if err != nil {
		return err
	}
	if !locked {
		return nil
	}
	defer releaseLock(ctx, h.redis, lockKey)

	exportTask, err := h.taskStore.GetByIDForWorker(ctx, payload.TaskID)
	if err != nil {
		h.logger.Error("查询导出任务失败", zap.Uint("task_id", payload.TaskID), zap.Error(err))
		return asynq.SkipRetry
	}

	if exportTask.Status == constants.ExportTaskStatusCompleted || exportTask.Status == constants.ExportTaskStatusFailed || exportTask.Status == constants.ExportTaskStatusCancelled {
		return nil
	}

	updater := dispatchUpdater(exportTask)
	if exportTask.CancelRequested {
		if err := h.shardStore.CancelByTaskID(ctx, exportTask.ID, updater, "任务已取消"); err != nil {
			return err
		}
		if err := h.taskStore.MarkCancelledByWorker(ctx, exportTask.ID, updater, "任务已取消"); err != nil {
			return err
		}
		return nil
	}

	unfinishedCount, err := h.shardStore.CountUnfinishedByTaskID(ctx, exportTask.ID)
	if err != nil {
		return err
	}
	if unfinishedCount > 0 {
		return fmt.Errorf("分片任务尚未完成: %d", unfinishedCount)
	}

	failedCount, err := h.shardStore.CountByTaskIDAndStatus(ctx, exportTask.ID, constants.ExportShardStatusFailed)
	if err != nil {
		return err
	}
	if failedCount > 0 {
		if err := h.taskStore.MarkFailed(ctx, exportTask.ID, updater, "存在失败分片，导出任务失败"); err != nil {
			return err
		}
		return nil
	}

	strategy, ok := h.sceneRegistry.Get(exportTask.Scene)
	if !ok {
		if err := h.taskStore.MarkFailed(ctx, exportTask.ID, updater, "导出场景未注册"); err != nil {
			return err
		}
		return nil
	}

	shards, err := h.shardStore.ListByTaskID(ctx, exportTask.ID)
	if err != nil {
		return err
	}

	rows := make([][]string, 0)
	for _, shard := range shards {
		if shard.Status != constants.ExportShardStatusSuccess {
			continue
		}
		currentRows, err := strategy.QueryRows(ctx, exportTask, shard.CursorStart, shard.CursorEnd)
		if err != nil {
			return h.handleFinalizeError(ctx, exportTask.ID, updater, "读取分片数据失败", err)
		}
		rows = append(rows, currentRows...)
	}

	localPath, fileSize, err := writeExportFile(exportTask.Format, strategy.Headers(), rows)
	if err != nil {
		return h.handleFinalizeError(ctx, exportTask.ID, updater, "生成汇总文件失败", err)
	}
	defer func() { _ = os.Remove(localPath) }()

	fileName := fmt.Sprintf("%s.%s", exportTask.TaskNo, exportTask.Format)
	fileKey, err := uploadExportFile(ctx, h.storageSvc, localPath, fileName)
	if err != nil {
		return h.handleFinalizeError(ctx, exportTask.ID, updater, "上传汇总文件失败", err)
	}

	if err := h.taskStore.MarkCompleted(ctx, exportTask.ID, updater, fileKey, fileSize); err != nil {
		return err
	}

	return nil
}

func (h *ExportFinalizeHandler) handleFinalizeError(ctx context.Context, taskID uint, updater uint, prefix string, err error) error {
	if isFinalRetry(ctx) {
		markErr := h.taskStore.MarkFailed(ctx, taskID, updater, prefix+": "+err.Error())
		if markErr != nil {
			return markErr
		}
		return nil
	}
	return err
}