package grpc

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"sync"
	"time"

	"schedule_converter/service"

	pb "schedule_converter/proto/runner"
)

type TaskHandler struct {
	cancelledTasks sync.Map
	service        *service.Service
}

func NewTaskHandler() *TaskHandler {
	return &TaskHandler{service: service.NewService()}
}

func supportedTaskTypes() []pb.TaskType {
	return []pb.TaskType{
		pb.TaskType_TASK_TYPE_LOGIN,
		pb.TaskType_TASK_TYPE_GET_SCHEDULE,
		pb.TaskType_TASK_TYPE_GET_GRADES,
		pb.TaskType_TASK_TYPE_GET_EXAMS,
		pb.TaskType_TASK_TYPE_GET_EMPTY_CLASSROOM,
		pb.TaskType_TASK_TYPE_GET_CET,
	}
}

func unmarshalPayload(payload []byte, v any) error {
	if len(payload) == 0 {
		return fmt.Errorf("任务 payload 为空")
	}
	if err := json.Unmarshal(payload, v); err != nil {
		return fmt.Errorf("解析任务 payload 失败: %w", err)
	}
	return nil
}

func (h *TaskHandler) Execute(task *pb.Task) *pb.TaskResult {
	log := slog.With("task_id", task.TaskId, "task_type", task.Type.String())
	log.Info("开始执行任务")

	result := &pb.TaskResult{
		TaskId:      task.TaskId,
		CompletedAt: time.Now().UnixMilli(),
	}

	if h.IsCancelled(task.TaskId) {
		result.Status = pb.TaskStatus_TASK_STATUS_CANCELLED
		result.ErrorMessage = "任务已取消"
		log.Info("任务已取消")
		return result
	}

	ctx := context.Background()
	data, err := h.dispatch(ctx, task)

	if err != nil {
		if errors.Is(err, errUnknownTaskType) {
			result.Status = pb.TaskStatus_TASK_STATUS_FAILED
			result.ErrorMessage = err.Error()
			log.Warn("未知的任务类型")
			return result
		}
		result.Status = pb.TaskStatus_TASK_STATUS_FAILED
		result.ErrorMessage = err.Error()
		log.Error("任务执行失败", "error", err)
		return result
	}

	result.Status = pb.TaskStatus_TASK_STATUS_SUCCESS
	result.Data = data
	log.Info("任务执行成功")
	return result
}

var errUnknownTaskType = fmt.Errorf("unknown task type")

func (h *TaskHandler) dispatch(ctx context.Context, task *pb.Task) ([]byte, error) {
	switch task.Type {
	case pb.TaskType_TASK_TYPE_GET_SCHEDULE:
		return h.getSchedule(ctx, task.Payload)
	case pb.TaskType_TASK_TYPE_GET_GRADES:
		return h.getGrades(ctx, task.Payload)
	case pb.TaskType_TASK_TYPE_GET_EXAMS:
		return h.getExams(ctx, task.Payload)
	case pb.TaskType_TASK_TYPE_LOGIN:
		return h.login(ctx, task.Payload)
	case pb.TaskType_TASK_TYPE_GET_EMPTY_CLASSROOM:
		return h.getEmptyClassrooms(ctx, task.Payload)
	case pb.TaskType_TASK_TYPE_GET_CET:
		return h.getCET(ctx, task.Payload)
	default:
		return nil, fmt.Errorf("%w: %v", errUnknownTaskType, task.Type)
	}
}

func (h *TaskHandler) CancelTask(taskID string) {
	h.cancelledTasks.Store(taskID, true)
	slog.Info("任务已标记为取消", "task_id", taskID)
}

func (h *TaskHandler) IsCancelled(taskID string) bool {
	v, ok := h.cancelledTasks.Load(taskID)
	return ok && v.(bool)
}