package errors

import (
	"errors"
	"fmt"
)

// 錯誤碼定義
const (
	// 通用錯誤碼 (1000-1999)
	ErrCodeInternal      = 1000
	ErrCodeInvalidInput  = 1001
	ErrCodeNotFound      = 1002
	ErrCodeAlreadyExists = 1003
	ErrCodeUnauthorized  = 1004
	ErrCodeForbidden     = 1005

	// 角色相關錯誤碼 (2000-2099)
	ErrCodeRoleNotFound      = 2000
	ErrCodeRoleAlreadyExists = 2001
	ErrCodeRoleHasUsers      = 2002
	ErrCodeInvalidRoleUID    = 2003

	// 權限相關錯誤碼 (2100-2199)
	ErrCodePermissionNotFound = 2100
	ErrCodePermissionDenied   = 2101
	ErrCodeInvalidPermission  = 2102
	ErrCodeCircularDependency = 2103

	// 使用者角色相關錯誤碼 (2200-2299)
	ErrCodeUserRoleNotFound      = 2200
	ErrCodeUserRoleAlreadyExists = 2201
	ErrCodeInvalidUserUID        = 2202

	// Repository 相關錯誤碼 (3000-3099)
	ErrCodeDBConnection  = 3000
	ErrCodeDBQuery       = 3001
	ErrCodeDBTransaction = 3002
	ErrCodeCacheError    = 3003
)

// AppError 應用程式錯誤
type AppError struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
	Err     error  `json:"-"`
}

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

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

// New 建立新錯誤
func New(code int, message string) *AppError {
	return &AppError{
		Code:    code,
		Message: message,
	}
}

// Wrap 包裝錯誤
func Wrap(code int, message string, err error) *AppError {
	return &AppError{
		Code:    code,
		Message: message,
		Err:     err,
	}
}

// 預定義錯誤
var (
	// 通用錯誤
	ErrInternal      = New(ErrCodeInternal, "internal server error")
	ErrInvalidInput  = New(ErrCodeInvalidInput, "invalid input")
	ErrNotFound      = New(ErrCodeNotFound, "resource not found")
	ErrAlreadyExists = New(ErrCodeAlreadyExists, "resource already exists")
	ErrUnauthorized  = New(ErrCodeUnauthorized, "unauthorized")
	ErrForbidden     = New(ErrCodeForbidden, "forbidden")

	// 角色錯誤
	ErrRoleNotFound      = New(ErrCodeRoleNotFound, "role not found")
	ErrRoleAlreadyExists = New(ErrCodeRoleAlreadyExists, "role already exists")
	ErrRoleHasUsers      = New(ErrCodeRoleHasUsers, "role has users")
	ErrInvalidRoleUID    = New(ErrCodeInvalidRoleUID, "invalid role uid")

	// 權限錯誤
	ErrPermissionNotFound = New(ErrCodePermissionNotFound, "permission not found")
	ErrPermissionDenied   = New(ErrCodePermissionDenied, "permission denied")
	ErrInvalidPermission  = New(ErrCodeInvalidPermission, "invalid permission")
	ErrCircularDependency = New(ErrCodeCircularDependency, "circular dependency detected")

	// 使用者角色錯誤
	ErrUserRoleNotFound      = New(ErrCodeUserRoleNotFound, "user role not found")
	ErrUserRoleAlreadyExists = New(ErrCodeUserRoleAlreadyExists, "user role already exists")
	ErrInvalidUserUID        = New(ErrCodeInvalidUserUID, "invalid user uid")

	// Repository 錯誤
	ErrDBConnection  = New(ErrCodeDBConnection, "database connection error")
	ErrDBQuery       = New(ErrCodeDBQuery, "database query error")
	ErrDBTransaction = New(ErrCodeDBTransaction, "database transaction error")
	ErrCacheError    = New(ErrCodeCacheError, "cache error")
)

// Is 檢查錯誤類型
func Is(err, target error) bool {
	return errors.Is(err, target)
}

// As 轉換錯誤類型
func As(err error, target interface{}) bool {
	return errors.As(err, target)
}

// GetCode 取得錯誤碼
func GetCode(err error) int {
	var appErr *AppError
	if errors.As(err, &appErr) {
		return appErr.Code
	}
	return ErrCodeInternal
}