type AppError struct {
    Code       string
    Message    string
    StatusCode int
    Err        error
}

func (e *AppError) Error() string {
    return e.Message
}

// Predefined errors
var (
    ErrNotFound = &AppError{
        Code:       "NOT_FOUND",
        Message:    "Resource not found",
        StatusCode: 404,
    }
    
    ErrUnauthorized = &AppError{
        Code:       "UNAUTHORIZED",
        Message:    "Unauthorized access",
        StatusCode: 401,
    }
    
    ErrValidation = &AppError{
        Code:       "VALIDATION_ERROR",
        Message:    "Validation failed",
        StatusCode: 400,
    }
)

type ErrorResponse struct {
    Error ErrorDetail `json:"error"`
}

type ErrorDetail struct {
    Code    string            `json:"code"`
    Message string            `json:"message"`
    Details []ValidationError `json:"details,omitempty"`
    TraceID string            `json:"traceId"`
}

func HandleError(c echo.Context, err error) error {
    var appErr *AppError
    if errors.As(err, &appErr) {
        return c.JSON(appErr.StatusCode, ErrorResponse{
            Error: ErrorDetail{
                Code:    appErr.Code,
                Message: appErr.Message,
                TraceID: getTraceID(c),
            },
        })
    }
    
    // Unknown error
    return c.JSON(500, ErrorResponse{
        Error: ErrorDetail{
            Code:    "INTERNAL_ERROR",
            Message: "An unexpected error occurred",
            TraceID: getTraceID(c),
        },
    })
}