package api

import (
	"encoding/json"
	"fmt"
)

// Err represents an http response error following the api format.
// These are used by the services to set the *execution status*
// directly into the response as JSON alongside response output fields.
type Err struct {
	// error code (unique)
	Code int `json:"code"`
	// error small description
	Reason string `json:"reason"`
	// associated HTTP status
	Status int
	// data that can be added to document the error
	data []interface{} `json:"data"`
}

func (e Err) Error() string {
	return fmt.Sprintf("[%d] %s", e.Code, e.Reason)
}

// With adds data to document the error and returns the updated error
func (e Err) With(data ...interface{}) Err {
	if e.data == nil {
		e.data = make([]interface{}, 0)
	}
	e.data = append(e.data, data...)
	return e
}

// MarshalJSON implements the 'json.Marshaler' interface and is used
// to generate the JSON representation of the error
func (e Err) MarshalJSON() ([]byte, error) {
	fmt := make(map[string]interface{})
	fmt["code"] = e.Code
	fmt["reason"] = e.Reason
	if len(e.data) > 0 {
		fmt["data"] = e.data
	}
	return json.Marshal(fmt)
}