package handlers

import (
	"errors"
	"fmt"
	"go-todo-api/constants"
	"go-todo-api/models"
	"go-todo-api/services"
	"net/http"
	"strconv"

	"github.com/gin-gonic/gin"
	"gorm.io/gorm"
)

// 辅助函数：从 Gin Context 中获取用户 ID
// ❗ 修正：将此函数放在包级别 (不在任何结构体内)
func getUserIDFromContext(c *gin.Context) (uint, error) {
	// Note: UserIDKey must be imported from the constants package
	// ... (Your implementation using constants.UserIDKey)
	userIDStr, exists := c.Get(constants.UserIDKey)
	if !exists {
		return 0, errors.New("User ID not found in context")
	}

	// 转换 string 到 uint
	userIDUint, err := strconv.ParseUint(userIDStr.(string), 10, 32)
	if err != nil {
		return 0, errors.New("Invalid user ID format in context")
	}
	return uint(userIDUint), nil
}

// TodoHandler 结构体持有 Service 接口，用于处理 HTTP 请求
type TodoHandler struct {
	// Handler 层依赖于 Service 接口
	Service services.TodoService
}

// NewTodoHandler 实例化一个新的 TodoHandler
func NewTodoHandler(service services.TodoService) *TodoHandler {
	return &TodoHandler{Service: service}
}

// FindAllTodosHandler 处理 GET /todos 请求
func (h *TodoHandler) FindAllTodosHandler(c *gin.Context) {
	userID, err := getUserIDFromContext(c) // 1. 获取 UserID
	if err != nil || userID == 0 {
		// 401 错误，使用自定义代码 CodeInvalidAuth
		c.JSON(http.StatusUnauthorized, constants.StandardResponse{
			Code:    constants.CodeInvalidAuth,
			Message: "Unauthorized or Invalid User ID",
		})
		return
	}
	// 1. 调用 Service 层获取数据 (Service 层调用 Repository 层)
	todos, err := h.Service.FindAllTodos(userID)

	if err != nil {
		// 500 内部错误，使用自定义代码 CodeInternalError
		c.JSON(http.StatusInternalServerError, constants.StandardResponse{
			Code:    constants.CodeInternalError,
			Message: fmt.Sprintf("Failed to retrieve todos: %v", err),
		})
		return
	}
	// 200 成功响应，使用 CodeSuccess
	// 2. 返回 JSON 响应 (Handler 负责 HTTP 细节)
	c.JSON(http.StatusOK, constants.StandardResponse{
		Code:    constants.CodeSuccess,
		Message: "Successfully retrieved todos",
		Data:    todos,
	})
}

// FindTodoByIDHandler 处理 GET /todos/:id 请求
func (h *TodoHandler) FindTodoByIDHandler(c *gin.Context) {
	userID, err := getUserIDFromContext(c) // 1. 获取 UserID
	if err != nil || userID == 0 {
		c.JSON(http.StatusUnauthorized, gin.H{"error": "Unauthorized or Invalid User ID"})
		return
	}
	// 1. 获取 URL 参数 ID
	idStr := c.Param("id")
	// 将字符串 ID 转换为无符号整数 (uint)
	id, err := strconv.ParseUint(idStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid Todo ID format"})
		return
	}

	// 2. 调用 Service 层获取数据
	todo, err := h.Service.FindTodoByID(uint(id), userID)

	if err != nil {
		// 检查是否是“未找到记录”错误
		if errors.Is(err, gorm.ErrRecordNotFound) {
			// 404 资源未找到，使用 CodeResourceNotFound
			c.JSON(http.StatusNotFound, constants.StandardResponse{
				Code:    constants.CodeResourceNotFound,
				Message: "Todo item not found",
			})
			return
		}
		// 其他数据库错误
		c.JSON(http.StatusInternalServerError, constants.StandardResponse{
			Code:    constants.CodeInternalError,
			Message: fmt.Sprintf("Failed to retrieve todo: %v", err),
		})
		return
	}

	// 3. 返回 JSON 响应
	c.JSON(http.StatusOK, constants.StandardResponse{
		Code:    constants.CodeSuccess,
		Message: "Successfully retrieved todo",
		Data:    todo,
	})
}

// DeleteTodoByIDHandler 处理 DELETE /todos/:id 请求
func (h *TodoHandler) DeleteTodoByIDHandler(c *gin.Context) {
	userID, err := getUserIDFromContext(c) // 1. 获取 UserID
	if err != nil || userID == 0 {
		// 401 错误，使用自定义代码 CodeInvalidAuth
		c.JSON(http.StatusUnauthorized, constants.StandardResponse{
			Code:    constants.CodeInvalidAuth,
			Message: "Unauthorized or Invalid User ID",
		})
		return
	}
	// 1. 获取并解析 ID
	idStr := c.Param("id")
	id, err := strconv.ParseUint(idStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, constants.StandardResponse{
			Code:    constants.CodeInvalidAuth,
			Message: "Invalid Todo ID format",
		})
		return
	}

	// 2. 调用 Service 层执行删除逻辑
	err = h.Service.DeleteTodoByID(uint(id), userID)

	if err != nil {
		// 检查是否是“未找到记录”错误（Repository层返回的gorm.ErrRecordNotFound）
		if errors.Is(err, gorm.ErrRecordNotFound) {
			// 404 资源未找到，使用 CodeResourceNotFound
			c.JSON(http.StatusNotFound, constants.StandardResponse{
				Code:    constants.CodeResourceNotFound,
				Message: "Todo item not found",
			})
			return
		}
		// 其他数据库错误
		c.JSON(http.StatusInternalServerError, constants.StandardResponse{
			Code:    constants.CodeInternalError,
			Message: fmt.Sprintf("Failed to delete todo item: %v", err),
		})
		return
	}

	// 3. 返回成功响应
	c.JSON(http.StatusOK, constants.StandardResponse{
		Code:    constants.CodeSuccess,
		Message: "Todo deleted successfully (soft deleted)",
	})
}

// CreateTodoHandler 处理 POST /todos 请求，创建新的待办事项
func (h *TodoHandler) CreateTodoHandler(c *gin.Context) {
	var newTodo models.Todo

	// 1. 绑定前端 JSON 数据
	// Todo 结构体中应有 binding:"required" 标签来确保数据完整性
	if err := c.ShouldBindJSON(&newTodo); err != nil {
		c.JSON(http.StatusBadRequest, constants.StandardResponse{
			Code:    constants.CodeValidationError,
			Message: err.Error(),
		})
		return
	}
	userID, err := getUserIDFromContext(c) // 获取 UserID

	if err != nil || userID == 0 { // ❗ 核心修正：新增检查 userID == 0
		// 如果获取失败或者 ID 为 0，视为未授权或无效令牌
		c.JSON(http.StatusUnauthorized, constants.StandardResponse{
			Code:    constants.CodeInvalidAuth,
			Message: "Unauthorized or Invalid User ID",
		})
		return
	}

	// 2. 调用 Service 层创建数据 (Service 会调用 Repository)
	if err := h.Service.CreateTodo(&newTodo, userID); err != nil {
		c.JSON(http.StatusInternalServerError, constants.StandardResponse{
			Code:    constants.CodeInternalError,
			Message: fmt.Sprintf("Failed to save todo item: %v", err),
		})
		return
	}

	// 3. 返回成功响应
	// newTodo 现在包含了 GORM 自动生成的 ID 和时间戳
	c.JSON(http.StatusCreated, constants.StandardResponse{
		Code:    constants.CodeSuccess,
		Message: "Todo created successfully (via Service)",
		Data:    newTodo,
	})
}

// UpdateTodoHandler 处理 PATCH /todos/:id 请求
func (h *TodoHandler) UpdateTodoHandler(c *gin.Context) {
	userID, err := getUserIDFromContext(c) // 1. 获取 UserID
	if err != nil || userID == 0 {
		c.JSON(http.StatusUnauthorized, constants.StandardResponse{
			Code:    constants.CodeInvalidAuth,
			Message: "Unauthorized or Invalid User ID",
		})
		return
	}
	// 1. 获取并解析 ID
	idStr := c.Param("id")
	id, err := strconv.ParseUint(idStr, 10, 32)
	if err != nil {
		c.JSON(http.StatusBadRequest, constants.StandardResponse{
			Code:    constants.CodeValidationError,
			Message: "Invalid Todo ID format",
		})
		return
	}

	// 2. 接收更新的 JSON 数据到 map 中（用于部分更新）
	var input map[string]interface{}
	if err := c.ShouldBindJSON(&input); err != nil {
		c.JSON(http.StatusBadRequest, constants.StandardResponse{
			Code:    constants.CodeValidationError,
			Message: err.Error(),
		})
		return
	}

	// 3. 调用 Service 层执行更新逻辑
	// 注意：Service 层将负责查找记录，然后执行更新
	updatedTodo, err := h.Service.UpdateTodo(uint(id), userID, input)

	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			c.JSON(http.StatusNotFound, constants.StandardResponse{
				Code:    constants.CodeResourceNotFound,
				Message: "Todo item not found",
			})
			return
		}
		c.JSON(http.StatusInternalServerError, constants.StandardResponse{
			Code:    constants.CodeInternalError,
			Message: fmt.Sprintf("Failed to update todo item: %v", err),
		})
		return
	}

	// 4. 返回更新后的记录
	c.JSON(http.StatusOK, constants.StandardResponse{
		Code:    constants.CodeSuccess,
		Message: "Todo updated successfully",
		Data:    updatedTodo,
	})
}