backend/internal/handler/helpers.go

package handler

import (
	"carrotskin/internal/errors"
	"carrotskin/internal/model"
	"carrotskin/internal/types"
	"net/http"
	"strconv"

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

// parseIntWithDefault 将字符串解析为整数，解析失败返回默认值
func parseIntWithDefault(s string, defaultVal int) int {
	val, err := strconv.Atoi(s)
	if err != nil {
		return defaultVal
	}
	return val
}

// GetUserIDFromContext 从上下文获取用户ID，如果不存在返回未授权响应
// 返回值: userID, ok (如果ok为false，已经发送了错误响应)
func GetUserIDFromContext(c *gin.Context) (int64, bool) {
	userIDValue, exists := c.Get("user_id")
	if !exists {
		c.JSON(http.StatusUnauthorized, model.NewErrorResponse(
			model.CodeUnauthorized,
			model.MsgUnauthorized,
			nil,
		))
		return 0, false
	}

	// 安全的类型断言
	userID, ok := userIDValue.(int64)
	if !ok {
		c.JSON(http.StatusInternalServerError, model.NewErrorResponse(
			model.CodeServerError,
			"用户ID类型错误",
			nil,
		))
		return 0, false
	}

	return userID, true
}

// UserToUserInfo 将 User 模型转换为 UserInfo 响应
func UserToUserInfo(user *model.User) *types.UserInfo {
	return &types.UserInfo{
		ID:          user.ID,
		Username:    user.Username,
		Email:       user.Email,
		Avatar:      user.Avatar,
		Points:      user.Points,
		Role:        user.Role,
		Status:      user.Status,
		LastLoginAt: user.LastLoginAt,
		CreatedAt:   user.CreatedAt,
		UpdatedAt:   user.UpdatedAt,
	}
}

// ProfileToProfileInfo 将 Profile 模型转换为 ProfileInfo 响应
func ProfileToProfileInfo(profile *model.Profile) *types.ProfileInfo {
	return &types.ProfileInfo{
		UUID:       profile.UUID,
		UserID:     profile.UserID,
		Name:       profile.Name,
		SkinID:     profile.SkinID,
		CapeID:     profile.CapeID,
		IsActive:   profile.IsActive,
		LastUsedAt: profile.LastUsedAt,
		CreatedAt:  profile.CreatedAt,
		UpdatedAt:  profile.UpdatedAt,
	}
}

// ProfilesToProfileInfos 批量转换 Profile 模型为 ProfileInfo 响应
func ProfilesToProfileInfos(profiles []*model.Profile) []*types.ProfileInfo {
	result := make([]*types.ProfileInfo, 0, len(profiles))
	for _, profile := range profiles {
		result = append(result, ProfileToProfileInfo(profile))
	}
	return result
}

// TextureToTextureInfo 将 Texture 模型转换为 TextureInfo 响应
func TextureToTextureInfo(texture *model.Texture) *types.TextureInfo {
	return &types.TextureInfo{
		ID:            texture.ID,
		UploaderID:    texture.UploaderID,
		Name:          texture.Name,
		Description:   texture.Description,
		Type:          types.TextureType(texture.Type),
		URL:           texture.URL,
		Hash:          texture.Hash,
		Size:          texture.Size,
		IsPublic:      texture.IsPublic,
		DownloadCount: texture.DownloadCount,
		FavoriteCount: texture.FavoriteCount,
		IsSlim:        texture.IsSlim,
		Status:        texture.Status,
		CreatedAt:     texture.CreatedAt,
		UpdatedAt:     texture.UpdatedAt,
	}
}

// TexturesToTextureInfos 批量转换 Texture 模型为 TextureInfo 响应
func TexturesToTextureInfos(textures []*model.Texture) []*types.TextureInfo {
	result := make([]*types.TextureInfo, len(textures))
	for i, texture := range textures {
		result[i] = TextureToTextureInfo(texture)
	}
	return result
}

// RespondBadRequest 返回400错误响应
func RespondBadRequest(c *gin.Context, message string, err error) {
	c.JSON(http.StatusBadRequest, model.NewErrorResponse(
		model.CodeBadRequest,
		message,
		err,
	))
}

// RespondUnauthorized 返回401错误响应
func RespondUnauthorized(c *gin.Context, message string) {
	c.JSON(http.StatusUnauthorized, model.NewErrorResponse(
		model.CodeUnauthorized,
		message,
		nil,
	))
}

// RespondForbidden 返回403错误响应
func RespondForbidden(c *gin.Context, message string) {
	c.JSON(http.StatusForbidden, model.NewErrorResponse(
		model.CodeForbidden,
		message,
		nil,
	))
}

// RespondNotFound 返回404错误响应
func RespondNotFound(c *gin.Context, message string) {
	c.JSON(http.StatusNotFound, model.NewErrorResponse(
		model.CodeNotFound,
		message,
		nil,
	))
}

// RespondServerError 返回500错误响应
func RespondServerError(c *gin.Context, message string, err error) {
	c.JSON(http.StatusInternalServerError, model.NewErrorResponse(
		model.CodeServerError,
		message,
		err,
	))
}

// RespondSuccess 返回成功响应
func RespondSuccess(c *gin.Context, data interface{}) {
	c.JSON(http.StatusOK, model.NewSuccessResponse(data))
}

// RespondWithError 根据错误类型自动选择状态码
func RespondWithError(c *gin.Context, err error) {
	if err == nil {
		return
	}

	// 使用errors.Is检查预定义错误
	if errors.Is(err, errors.ErrUserNotFound) || 
	   errors.Is(err, errors.ErrProfileNotFound) || 
	   errors.Is(err, errors.ErrTextureNotFound) ||
	   errors.Is(err, errors.ErrNotFound) {
		RespondNotFound(c, err.Error())
		return
	}

	if errors.Is(err, errors.ErrProfileNoPermission) || 
	   errors.Is(err, errors.ErrTextureNoPermission) ||
	   errors.Is(err, errors.ErrForbidden) {
		RespondForbidden(c, err.Error())
		return
	}

	if errors.Is(err, errors.ErrUnauthorized) || 
	   errors.Is(err, errors.ErrInvalidToken) ||
	   errors.Is(err, errors.ErrTokenExpired) {
		RespondUnauthorized(c, err.Error())
		return
	}

	// 检查AppError类型
	var appErr *errors.AppError
	if errors.As(err, &appErr) {
		c.JSON(appErr.Code, model.NewErrorResponse(
			appErr.Code,
			appErr.Message,
			appErr.Err,
		))
		return
	}

	// 默认返回500错误
	RespondServerError(c, err.Error(), err)
}