package errors

import (
	"errors"
	"fmt"
)

// AppError 统一的应用错误类型
type AppError struct {
	Code    string
	Message string
	Cause   error
}

func (e *AppError) Error() string {
	if e.Cause != nil {
		return fmt.Sprintf("[%s] %s: %v", e.Code, e.Message, e.Cause)
	}
	return fmt.Sprintf("[%s] %s", e.Code, e.Message)
}

func (e *AppError) Unwrap() error {
	return e.Cause
}

// 预定义错误
var (
	// 通用错误
	ErrNotFound     = &AppError{Code: "NOT_FOUND", Message: "资源不存在"}
	ErrUnauthorized = &AppError{Code: "UNAUTHORIZED", Message: "未授权"}
	ErrForbidden    = &AppError{Code: "FORBIDDEN", Message: "禁止访问"}
	ErrBadRequest   = &AppError{Code: "BAD_REQUEST", Message: "请求参数错误"}
	ErrInternal     = &AppError{Code: "INTERNAL_ERROR", Message: "内部服务器错误"}

	// 用户相关错误
	ErrUserNotFound                = &AppError{Code: "USER_NOT_FOUND", Message: "用户不存在"}
	ErrUserAlreadyExists           = &AppError{Code: "USER_ALREADY_EXISTS", Message: "用户已存在"}
	ErrInvalidCredentials          = &AppError{Code: "INVALID_CREDENTIALS", Message: "用户名或密码错误"}
	ErrInvalidUsername             = &AppError{Code: "INVALID_USERNAME", Message: "无效的用户名"}
	ErrInvalidEmail                = &AppError{Code: "INVALID_EMAIL", Message: "无效的邮箱"}
	ErrInvalidPhone                = &AppError{Code: "INVALID_PHONE", Message: "无效的手机号"}
	ErrWeakPassword                = &AppError{Code: "WEAK_PASSWORD", Message: "密码强度不足"}
	ErrUsernameExists              = &AppError{Code: "USERNAME_EXISTS", Message: "用户名已存在"}
	ErrEmailExists                 = &AppError{Code: "EMAIL_EXISTS", Message: "邮箱已存在"}
	ErrPhoneExists                 = &AppError{Code: "PHONE_EXISTS", Message: "手机号已存在"}
	ErrUserBanned                  = &AppError{Code: "USER_BANNED", Message: "用户已被封禁"}
	ErrUserBlocked                 = &AppError{Code: "USER_BLOCKED", Message: "存在屏蔽关系"}
	ErrInvalidOperation            = &AppError{Code: "INVALID_OPERATION", Message: "无效操作"}
	ErrEmailServiceUnavailable     = &AppError{Code: "EMAIL_SERVICE_UNAVAILABLE", Message: "邮件服务不可用"}
	ErrVerificationCodeTooFrequent = &AppError{Code: "VERIFICATION_CODE_TOO_FREQUENT", Message: "验证码发送过于频繁"}
	ErrVerificationCodeInvalid     = &AppError{Code: "VERIFICATION_CODE_INVALID", Message: "验证码无效"}
	ErrVerificationCodeExpired     = &AppError{Code: "VERIFICATION_CODE_EXPIRED", Message: "验证码已过期"}
	ErrVerificationCodeUnavailable = &AppError{Code: "VERIFICATION_CODE_UNAVAILABLE", Message: "验证码存储不可用"}
	ErrEmailAlreadyVerified        = &AppError{Code: "EMAIL_ALREADY_VERIFIED", Message: "邮箱已验证"}
	ErrEmailNotBound               = &AppError{Code: "EMAIL_NOT_BOUND", Message: "邮箱未绑定"}

	// 帖子相关错误
	ErrPostNotFound = &AppError{Code: "POST_NOT_FOUND", Message: "帖子不存在"}
	ErrPostDeleted  = &AppError{Code: "POST_DELETED", Message: "帖子已删除"}

	// 群组相关错误
	ErrGroupNotFound        = &AppError{Code: "GROUP_NOT_FOUND", Message: "群组不存在"}
	ErrNotGroupMember       = &AppError{Code: "NOT_GROUP_MEMBER", Message: "不是群组成员"}
	ErrAlreadyGroupMember   = &AppError{Code: "ALREADY_GROUP_MEMBER", Message: "已是群组成员"}
	ErrNotGroupAdmin        = &AppError{Code: "NOT_GROUP_ADMIN", Message: "不是群管理员"}
	ErrNotGroupOwner        = &AppError{Code: "NOT_GROUP_OWNER", Message: "不是群主"}
	ErrGroupFull            = &AppError{Code: "GROUP_FULL", Message: "群已满"}
	ErrCannotRemoveOwner    = &AppError{Code: "CANNOT_REMOVE_OWNER", Message: "不能移除群主"}
	ErrCannotMuteOwner      = &AppError{Code: "CANNOT_MUTE_OWNER", Message: "不能禁言群主"}
	ErrMuted                = &AppError{Code: "MUTED", Message: "你已被禁言"}
	ErrMuteAllEnabled       = &AppError{Code: "MUTE_ALL_ENABLED", Message: "全员禁言中"}
	ErrCannotJoin           = &AppError{Code: "CANNOT_JOIN", Message: "该群不允许加入"}
	ErrJoinRequestPending   = &AppError{Code: "JOIN_REQUEST_PENDING", Message: "加群申请已提交"}
	ErrGroupRequestNotFound = &AppError{Code: "GROUP_REQUEST_NOT_FOUND", Message: "加群请求不存在"}
	ErrGroupRequestHandled  = &AppError{Code: "GROUP_REQUEST_HANDLED", Message: "该加群请求已处理"}
	ErrNotRequestTarget     = &AppError{Code: "NOT_REQUEST_TARGET", Message: "不是邀请目标用户"}
	ErrNoEligibleInvitee    = &AppError{Code: "NO_ELIGIBLE_INVITEE", Message: "没有可邀请的用户"}
	ErrNotMutualFollow      = &AppError{Code: "NOT_MUTUAL_FOLLOW", Message: "仅支持邀请互相关注用户"}
	ErrInviteNotAccepted    = &AppError{Code: "INVITE_NOT_ACCEPTED", Message: "被邀请人尚未同意邀请，无法审批"}

	// 表情包相关错误
	ErrStickerAlreadyExists = &AppError{Code: "STICKER_ALREADY_EXISTS", Message: "表情包已存在"}
	ErrInvalidStickerURL    = &AppError{Code: "INVALID_STICKER_URL", Message: "无效的表情包URL"}

	// 日程相关错误
	ErrInvalidSchedulePayload  = &AppError{Code: "INVALID_SCHEDULE_PAYLOAD", Message: "无效的日程数据"}
	ErrScheduleCourseNotFound  = &AppError{Code: "SCHEDULE_COURSE_NOT_FOUND", Message: "日程课程不存在"}
	ErrScheduleForbidden       = &AppError{Code: "SCHEDULE_FORBIDDEN", Message: "禁止的日程操作"}
	ErrScheduleColorDuplicated = &AppError{Code: "SCHEDULE_COLOR_DUPLICATED", Message: "课程颜色已被使用"}

	// 通知相关错误
	ErrUnauthorizedNotification = &AppError{Code: "UNAUTHORIZED_NOTIFICATION", Message: "无权删除此通知"}
)

// Wrap 包装错误
func Wrap(err error, appErr *AppError) *AppError {
	return &AppError{
		Code:    appErr.Code,
		Message: appErr.Message,
		Cause:   err,
	}
}

// New 创建新错误
func New(code, message string) *AppError {
	return &AppError{Code: code, Message: message}
}

// Is 判断是否为特定错误
func Is(err, target error) bool {
	return errors.Is(err, target)
}

// As 将错误转换为 AppError
func As(err error) (*AppError, bool) {
	var appErr *AppError
	if errors.As(err, &appErr) {
		return appErr, true
	}
	return nil, false
}