package errors

import (
	"fmt"
	"net/http"
)

// AppError 结构化应用错误
type AppError struct {
	Code       string                 `json:"code"`
	Message    string                 `json:"message"`
	HTTPStatus int                    `json:"-"`
	Cause      error                  `json:"-"`
	Context    map[string]interface{} `json:"-"`
}

// Error implements error interface
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)
}

// Unwrap returns the underlying error
func (e *AppError) Unwrap() error {
	return e.Cause
}

// NewAppError creates a new AppError
func NewAppError(code, message string, httpStatus int) *AppError {
	return &AppError{
		Code:       code,
		Message:    message,
		HTTPStatus: httpStatus,
	}
}

// Predefined errors
var (
	ErrModelNotFound    = NewAppError("model_not_found", "模型未找到", http.StatusNotFound)
	ErrModelDisabled    = NewAppError("model_disabled", "模型已禁用", http.StatusNotFound)
	ErrProviderNotFound = NewAppError("provider_not_found", "供应商未找到", http.StatusNotFound)
	ErrProviderDisabled = NewAppError("provider_disabled", "供应商已禁用", http.StatusNotFound)
	ErrInvalidRequest   = NewAppError("invalid_request", "无效的请求", http.StatusBadRequest)
	ErrInternal         = NewAppError("internal_error", "内部错误", http.StatusInternalServerError)
	ErrDatabaseNotInit  = NewAppError("database_not_initialized", "数据库未初始化", http.StatusInternalServerError)
	ErrConflict         = NewAppError("conflict", "资源已存在", http.StatusConflict)
)

// AsAppError 尝试将 error 转换为 *AppError
func AsAppError(err error) (*AppError, bool) {
	if err == nil {
		return nil, false
	}
	var appErr *AppError
	if ok := is(err, &appErr); ok {
		return appErr, true
	}
	return nil, false
}

func is(err error, target interface{}) bool {
	// 简单的类型断言
	if e, ok := err.(*AppError); ok {
		// 直接赋值
		switch t := target.(type) {
		case **AppError:
			*t = e
			return true
		}
	}
	return false
}