http_responders.go

package main

import (
	"fmt"
	"net/http"
)

// stripe.com/docs/api/errors
//
// 200: Everything worked as expected.
// 400: The request was unacceptable, often due to missing a required parameter.
// 401: No valid API key provided.
// 402: The parameters were valid but the request failed.
// 404: The requested resource doesn't exist.
// 409: The request conflicts with another request.
// 429: Too many requests hit the API too quickly.
// 500: Something went wrong on our end.
//
const (
	StatusCodeOK              = 200
	StatusCodeBadRequest      = 400
	StatusCodeUnauthorized    = 401
	StatusCodeRequestFailed   = 402
	StatusCodeNotFound        = 404
	StatusCodeConflict        = 409
	StatusCodeTooManyRequests = 429
	StatusCodeServerError     = 500
)

var Statuses = map[int]string{
	StatusCodeOK:              "OK",
	StatusCodeBadRequest:      "Bad Request",
	StatusCodeUnauthorized:    "Unauthorized",
	StatusCodeRequestFailed:   "Request Failed",
	StatusCodeNotFound:        "Not Found",
	StatusCodeConflict:        "Conflict",
	StatusCodeTooManyRequests: "Too Many Requests",
	StatusCodeServerError:     "Server Error",
}

var (
	RespondOK              = NewResponder(StatusCodeOK)
	RespondBadRequest      = NewResponder(StatusCodeBadRequest)
	RespondUnauthorized    = NewResponder(StatusCodeUnauthorized)
	RespondRequestFailed   = NewResponder(StatusCodeRequestFailed)
	RespondNotFound        = NewResponder(StatusCodeNotFound)
	RespondConflict        = NewResponder(StatusCodeConflict)
	RespondTooManyRequests = NewResponder(StatusCodeTooManyRequests)
	RespondServerError     = NewResponder(StatusCodeServerError)
)

// Returns a function that responds to an HTTP request.
func NewResponder(statusCode int) func(http.ResponseWriter) {
	respond := func(w http.ResponseWriter) {
		if statusCode >= 200 && statusCode <= 299 {
			w.WriteHeader(statusCode)
			return
		}
		status, ok := Statuses[statusCode]
		if !ok {
			err := fmt.Errorf("no such status code %d", statusCode)
			panic(err)
		}
		errStr := fmt.Sprintf("%d %s", statusCode, status)
		http.Error(w, errStr, statusCode)
	}
	return respond
}