package ratchet

import (
	"errors"
	"fmt"
)

const INTERNAL_ERROR_MESSAGE = "internal error"

// Application error codes.
//
// Note: these are generic codes but map well to HTTP status codes.
const (
	EINTERNAL = "internal"
	ENOTFOUND = "not_found"
)

// Error respresents an application specific-error. Application errors can be
// unwrapped by the caller to extract out the code and message
//
// Any non-application error (like disk error) should be reported as an EINTERNAL
// error and the human user should only see "Internal error" as the message.
// These low-level internal error details should only be logged and reported to
// the operation of the application, not the end user.
type Error struct {
	// Machine-readable error code.
	Code string

	// Human-readable error message.
	Message string
}

// Error  implements the error interface. Not used by the application otherwise.
func (e Error) Error() string {
	return fmt.Sprintf("ratchet error: code=%s message=%s", e.Code, e.Message)
}

// ErrorCode unwraps an application error and returns its code.
// Non-application errors always return EINTERNAL.
func ErrorCode(err error) string {
	var e *Error
	if err == nil {
		return ""
	} else if errors.As(err, &e) {
		return e.Code
	}
	return EINTERNAL
}

// ErrorMessage unwraps an application error and returns it's message.
// Non-application errors always return "Internal error".
func ErrorMessage(err error) string {
	var e *Error
	if err == nil {
		return ""
	} else if errors.As(err, &e) {
		return e.Message
	}
	return INTERNAL_ERROR_MESSAGE
}