package jsonapi

import (
	"encoding/json"
	"fmt"
	"io"
)

// MarshalErrors writes a JSON API response using the given `[]error`.
//
// For more information on JSON API error payloads, see the spec here:
// http://jsonapi.org/format/#document-top-level
// and here: http://jsonapi.org/format/#error-objects.
func MarshalErrors(w io.Writer, errorObjects []*ErrorObject) error {
	if err := json.NewEncoder(w).Encode(&ErrorsPayload{Errors: errorObjects}); err != nil {
		return err
	}
	return nil
}

// ErrorsPayload is a serializer struct for representing a valid JSON API errors payload.
type ErrorsPayload struct {
	Errors []*ErrorObject `json:"errors"`
}

// ErrorObject is an `Error` implementation as well as an implementation of the JSON API error object.
//
// The main idea behind this struct is that you can use it directly in your code as an error type
// and pass it directly to `MarshalErrors` to get a valid JSON API errors payload.
// For more information on Golang errors, see: https://golang.org/pkg/errors/
// For more information on the JSON API spec's error objects, see: http://jsonapi.org/format/#error-objects
type ErrorObject struct {
	// ID is a unique identifier for this particular occurrence of a problem.
	ID string `json:"id,omitempty"`

	// Title is a short, human-readable summary of the problem that SHOULD NOT change from occurrence to occurrence of the problem, except for purposes of localization.
	Title string `json:"title,omitempty"`

	// Detail is a human-readable explanation specific to this occurrence of the problem. Like title, this field’s value can be localized.
	Detail string `json:"detail,omitempty"`

	// Status is the HTTP status code applicable to this problem, expressed as a string value.
	Status string `json:"status,omitempty"`

	// Code is an application-specific error code, expressed as a string value.
	Code string `json:"code,omitempty"`

	// Meta is an object containing non-standard meta-information about the error.
	Meta *map[string]interface{} `json:"meta,omitempty"`
}

// Error implements the `Error` interface.
func (e *ErrorObject) Error() string {
	return fmt.Sprintf("Error: %s %s\n", e.Title, e.Detail)
}