github.go

// Copyright 2013 The go-github AUTHORS. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:generate go run gen-accessors.go

package github

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/google/go-querystring/query"
)

const (
	defaultBaseURL = "https://api.github.com/"
	uploadBaseURL  = "https://uploads.github.com/"
	userAgent      = "go-github"

	headerRateLimit     = "X-RateLimit-Limit"
	headerRateRemaining = "X-RateLimit-Remaining"
	headerRateReset     = "X-RateLimit-Reset"
	headerOTP           = "X-GitHub-OTP"

	mediaTypeV3                = "application/vnd.github.v3+json"
	defaultMediaType           = "application/octet-stream"
	mediaTypeV3SHA             = "application/vnd.github.v3.sha"
	mediaTypeV3Diff            = "application/vnd.github.v3.diff"
	mediaTypeV3Patch           = "application/vnd.github.v3.patch"
	mediaTypeOrgPermissionRepo = "application/vnd.github.v3.repository+json"

	// Media Type values to access preview APIs

	// https://developer.github.com/changes/2014-12-09-new-attributes-for-stars-api/
	mediaTypeStarringPreview = "application/vnd.github.v3.star+json"

	// https://help.github.com/enterprise/2.4/admin/guides/migrations/exporting-the-github-com-organization-s-repositories/
	mediaTypeMigrationsPreview = "application/vnd.github.wyandotte-preview+json"

	// https://developer.github.com/changes/2016-04-06-deployment-and-deployment-status-enhancements/
	mediaTypeDeploymentStatusPreview = "application/vnd.github.ant-man-preview+json"

	// https://developer.github.com/changes/2018-10-16-deployments-environments-states-and-auto-inactive-updates/
	mediaTypeExpandDeploymentStatusPreview = "application/vnd.github.flash-preview+json"

	// https://developer.github.com/changes/2016-02-19-source-import-preview-api/
	mediaTypeImportPreview = "application/vnd.github.barred-rock-preview"

	// https://developer.github.com/changes/2016-05-12-reactions-api-preview/
	mediaTypeReactionsPreview = "application/vnd.github.squirrel-girl-preview"

	// https://developer.github.com/changes/2016-05-23-timeline-preview-api/
	mediaTypeTimelinePreview = "application/vnd.github.mockingbird-preview+json"

	// https://developer.github.com/changes/2016-07-06-github-pages-preiew-api/
	mediaTypePagesPreview = "application/vnd.github.mister-fantastic-preview+json"

	// https://developer.github.com/changes/2016-09-14-projects-api/
	mediaTypeProjectsPreview = "application/vnd.github.inertia-preview+json"

	// https://developer.github.com/changes/2016-09-14-Integrations-Early-Access/
	mediaTypeIntegrationPreview = "application/vnd.github.machine-man-preview+json"

	// https://developer.github.com/changes/2017-01-05-commit-search-api/
	mediaTypeCommitSearchPreview = "application/vnd.github.cloak-preview+json"

	// https://developer.github.com/changes/2017-02-28-user-blocking-apis-and-webhook/
	mediaTypeBlockUsersPreview = "application/vnd.github.giant-sentry-fist-preview+json"

	// https://developer.github.com/changes/2017-02-09-community-health/
	mediaTypeRepositoryCommunityHealthMetricsPreview = "application/vnd.github.black-panther-preview+json"

	// https://developer.github.com/changes/2017-05-23-coc-api/
	mediaTypeCodesOfConductPreview = "application/vnd.github.scarlet-witch-preview+json"

	// https://developer.github.com/changes/2017-07-17-update-topics-on-repositories/
	mediaTypeTopicsPreview = "application/vnd.github.mercy-preview+json"

	// https://developer.github.com/changes/2017-08-30-preview-nested-teams/
	mediaTypeNestedTeamsPreview = "application/vnd.github.hellcat-preview+json"

	// https://developer.github.com/changes/2017-11-09-repository-transfer-api-preview/
	mediaTypeRepositoryTransferPreview = "application/vnd.github.nightshade-preview+json"

	// https://developer.github.com/changes/2018-01-25-organization-invitation-api-preview/
	mediaTypeOrganizationInvitationPreview = "application/vnd.github.dazzler-preview+json"

	// https://developer.github.com/changes/2018-03-16-protected-branches-required-approving-reviews/
	mediaTypeRequiredApprovingReviewsPreview = "application/vnd.github.luke-cage-preview+json"

	// https://developer.github.com/changes/2018-02-22-label-description-search-preview/
	mediaTypeLabelDescriptionSearchPreview = "application/vnd.github.symmetra-preview+json"

	// https://developer.github.com/changes/2018-02-07-team-discussions-api/
	mediaTypeTeamDiscussionsPreview = "application/vnd.github.echo-preview+json"

	// https://developer.github.com/changes/2018-03-21-hovercard-api-preview/
	mediaTypeHovercardPreview = "application/vnd.github.hagar-preview+json"

	// https://developer.github.com/changes/2018-01-10-lock-reason-api-preview/
	mediaTypeLockReasonPreview = "application/vnd.github.sailor-v-preview+json"

	// https://developer.github.com/changes/2018-05-07-new-checks-api-public-beta/
	mediaTypeCheckRunsPreview = "application/vnd.github.antiope-preview+json"

	// https://developer.github.com/enterprise/2.13/v3/repos/pre_receive_hooks/
	mediaTypePreReceiveHooksPreview = "application/vnd.github.eye-scream-preview"

	// https://developer.github.com/changes/2018-02-22-protected-branches-required-signatures/
	mediaTypeSignaturePreview = "application/vnd.github.zzzax-preview+json"

	// https://developer.github.com/changes/2018-09-05-project-card-events/
	mediaTypeProjectCardDetailsPreview = "application/vnd.github.starfox-preview+json"

	// https://developer.github.com/changes/2018-12-18-interactions-preview/
	mediaTypeInteractionRestrictionsPreview = "application/vnd.github.sombra-preview+json"

	// https://developer.github.com/changes/2019-02-14-draft-pull-requests/
	mediaTypeDraftPreview = "application/vnd.github.shadow-cat-preview+json"

	// https://developer.github.com/changes/2019-03-14-enabling-disabling-pages/
	mediaTypeEnablePagesAPIPreview = "application/vnd.github.switcheroo-preview+json"

	// https://developer.github.com/changes/2019-04-24-vulnerability-alerts/
	mediaTypeRequiredVulnerabilityAlertsPreview = "application/vnd.github.dorian-preview+json"
)

// A Client manages communication with the GitHub API.
type Client struct {
	clientMu sync.Mutex   // clientMu protects the client during calls that modify the CheckRedirect func.
	client   *http.Client // HTTP client used to communicate with the API.

	// Base URL for API requests. Defaults to the public GitHub API, but can be
	// set to a domain endpoint to use with GitHub Enterprise. BaseURL should
	// always be specified with a trailing slash.
	BaseURL *url.URL

	// Base URL for uploading files.
	UploadURL *url.URL

	// User agent used when communicating with the GitHub API.
	UserAgent string

	rateMu     sync.Mutex
	rateLimits [categories]Rate // Rate limits for the client as determined by the most recent API calls.

	common service // Reuse a single struct instead of allocating one for each service on the heap.

	// Services used for talking to different parts of the GitHub API.
	Activity       *ActivityService
	Admin          *AdminService
	Apps           *AppsService
	Authorizations *AuthorizationsService
	Checks         *ChecksService
	Gists          *GistsService
	Git            *GitService
	Gitignores     *GitignoresService
	Interactions   *InteractionsService
	Issues         *IssuesService
	Licenses       *LicensesService
	Marketplace    *MarketplaceService
	Migrations     *MigrationService
	Organizations  *OrganizationsService
	Projects       *ProjectsService
	PullRequests   *PullRequestsService
	Reactions      *ReactionsService
	Repositories   *RepositoriesService
	Search         *SearchService
	Teams          *TeamsService
	Users          *UsersService
}

type service struct {
	client *Client
}

// ListOptions specifies the optional parameters to various List methods that
// support pagination.
type ListOptions struct {
	// For paginated result sets, page of results to retrieve.
	Page int `url:"page,omitempty"`

	// For paginated result sets, the number of results to include per page.
	PerPage int `url:"per_page,omitempty"`
}

// UploadOptions specifies the parameters to methods that support uploads.
type UploadOptions struct {
	Name      string `url:"name,omitempty"`
	Label     string `url:"label,omitempty"`
	MediaType string `url:"-"`
}

// RawType represents type of raw format of a request instead of JSON.
type RawType uint8

const (
	// Diff format.
	Diff RawType = 1 + iota
	// Patch format.
	Patch
)

// RawOptions specifies parameters when user wants to get raw format of
// a response instead of JSON.
type RawOptions struct {
	Type RawType
}

// addOptions adds the parameters in opt as URL query parameters to s. opt
// must be a struct whose fields may contain "url" tags.
func addOptions(s string, opt interface{}) (string, error) {
	v := reflect.ValueOf(opt)
	if v.Kind() == reflect.Ptr && v.IsNil() {
		return s, nil
	}

	u, err := url.Parse(s)
	if err != nil {
		return s, err
	}

	qs, err := query.Values(opt)
	if err != nil {
		return s, err
	}

	u.RawQuery = qs.Encode()
	return u.String(), nil
}

// NewClient returns a new GitHub API client. If a nil httpClient is
// provided, http.DefaultClient will be used. To use API methods which require
// authentication, provide an http.Client that will perform the authentication
// for you (such as that provided by the golang.org/x/oauth2 library).
func NewClient(httpClient *http.Client) *Client {
	if httpClient == nil {
		httpClient = http.DefaultClient
	}
	baseURL, _ := url.Parse(defaultBaseURL)
	uploadURL, _ := url.Parse(uploadBaseURL)

	c := &Client{client: httpClient, BaseURL: baseURL, UserAgent: userAgent, UploadURL: uploadURL}
	c.common.client = c
	c.Activity = (*ActivityService)(&c.common)
	c.Admin = (*AdminService)(&c.common)
	c.Apps = (*AppsService)(&c.common)
	c.Authorizations = (*AuthorizationsService)(&c.common)
	c.Checks = (*ChecksService)(&c.common)
	c.Gists = (*GistsService)(&c.common)
	c.Git = (*GitService)(&c.common)
	c.Gitignores = (*GitignoresService)(&c.common)
	c.Interactions = (*InteractionsService)(&c.common)
	c.Issues = (*IssuesService)(&c.common)
	c.Licenses = (*LicensesService)(&c.common)
	c.Marketplace = &MarketplaceService{client: c}
	c.Migrations = (*MigrationService)(&c.common)
	c.Organizations = (*OrganizationsService)(&c.common)
	c.Projects = (*ProjectsService)(&c.common)
	c.PullRequests = (*PullRequestsService)(&c.common)
	c.Reactions = (*ReactionsService)(&c.common)
	c.Repositories = (*RepositoriesService)(&c.common)
	c.Search = (*SearchService)(&c.common)
	c.Teams = (*TeamsService)(&c.common)
	c.Users = (*UsersService)(&c.common)
	return c
}

// NewEnterpriseClient returns a new GitHub API client with provided
// base URL and upload URL (often the same URL).
// If either URL does not have a trailing slash, one is added automatically.
// If a nil httpClient is provided, http.DefaultClient will be used.
//
// Note that NewEnterpriseClient is a convenience helper only;
// its behavior is equivalent to using NewClient, followed by setting
// the BaseURL and UploadURL fields.
func NewEnterpriseClient(baseURL, uploadURL string, httpClient *http.Client) (*Client, error) {
	baseEndpoint, err := url.Parse(baseURL)
	if err != nil {
		return nil, err
	}
	if !strings.HasSuffix(baseEndpoint.Path, "/") {
		baseEndpoint.Path += "/"
	}

	uploadEndpoint, err := url.Parse(uploadURL)
	if err != nil {
		return nil, err
	}
	if !strings.HasSuffix(uploadEndpoint.Path, "/") {
		uploadEndpoint.Path += "/"
	}

	c := NewClient(httpClient)
	c.BaseURL = baseEndpoint
	c.UploadURL = uploadEndpoint
	return c, nil
}

// NewRequest creates an API request. A relative URL can be provided in urlStr,
// in which case it is resolved relative to the BaseURL of the Client.
// Relative URLs should always be specified without a preceding slash. If
// specified, the value pointed to by body is JSON encoded and included as the
// request body.
func (c *Client) NewRequest(method, urlStr string, body interface{}) (*http.Request, error) {
	if !strings.HasSuffix(c.BaseURL.Path, "/") {
		return nil, fmt.Errorf("BaseURL must have a trailing slash, but %q does not", c.BaseURL)
	}
	u, err := c.BaseURL.Parse(urlStr)
	if err != nil {
		return nil, err
	}

	var buf io.ReadWriter
	if body != nil {
		buf = new(bytes.Buffer)
		enc := json.NewEncoder(buf)
		enc.SetEscapeHTML(false)
		err := enc.Encode(body)
		if err != nil {
			return nil, err
		}
	}

	req, err := http.NewRequest(method, u.String(), buf)
	if err != nil {
		return nil, err
	}

	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	req.Header.Set("Accept", mediaTypeV3)
	if c.UserAgent != "" {
		req.Header.Set("User-Agent", c.UserAgent)
	}
	return req, nil
}

// NewUploadRequest creates an upload request. A relative URL can be provided in
// urlStr, in which case it is resolved relative to the UploadURL of the Client.
// Relative URLs should always be specified without a preceding slash.
func (c *Client) NewUploadRequest(urlStr string, reader io.Reader, size int64, mediaType string) (*http.Request, error) {
	if !strings.HasSuffix(c.UploadURL.Path, "/") {
		return nil, fmt.Errorf("UploadURL must have a trailing slash, but %q does not", c.UploadURL)
	}
	u, err := c.UploadURL.Parse(urlStr)
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequest("POST", u.String(), reader)
	if err != nil {
		return nil, err
	}
	req.ContentLength = size

	if mediaType == "" {
		mediaType = defaultMediaType
	}
	req.Header.Set("Content-Type", mediaType)
	req.Header.Set("Accept", mediaTypeV3)
	req.Header.Set("User-Agent", c.UserAgent)
	return req, nil
}

// Response is a GitHub API response. This wraps the standard http.Response
// returned from GitHub and provides convenient access to things like
// pagination links.
type Response struct {
	*http.Response

	// These fields provide the page values for paginating through a set of
	// results. Any or all of these may be set to the zero value for
	// responses that are not part of a paginated set, or for which there
	// are no additional pages.

	NextPage  int
	PrevPage  int
	FirstPage int
	LastPage  int

	// Explicitly specify the Rate type so Rate's String() receiver doesn't
	// propagate to Response.
	Rate Rate
}

// newResponse creates a new Response for the provided http.Response.
// r must not be nil.
func newResponse(r *http.Response) *Response {
	response := &Response{Response: r}
	response.populatePageValues()
	response.Rate = parseRate(r)
	return response
}

// populatePageValues parses the HTTP Link response headers and populates the
// various pagination link values in the Response.
func (r *Response) populatePageValues() {
	if links, ok := r.Response.Header["Link"]; ok && len(links) > 0 {
		for _, link := range strings.Split(links[0], ",") {
			segments := strings.Split(strings.TrimSpace(link), ";")

			// link must at least have href and rel
			if len(segments) < 2 {
				continue
			}

			// ensure href is properly formatted
			if !strings.HasPrefix(segments[0], "<") || !strings.HasSuffix(segments[0], ">") {
				continue
			}

			// try to pull out page parameter
			url, err := url.Parse(segments[0][1 : len(segments[0])-1])
			if err != nil {
				continue
			}
			page := url.Query().Get("page")
			if page == "" {
				continue
			}

			for _, segment := range segments[1:] {
				switch strings.TrimSpace(segment) {
				case `rel="next"`:
					r.NextPage, _ = strconv.Atoi(page)
				case `rel="prev"`:
					r.PrevPage, _ = strconv.Atoi(page)
				case `rel="first"`:
					r.FirstPage, _ = strconv.Atoi(page)
				case `rel="last"`:
					r.LastPage, _ = strconv.Atoi(page)
				}

			}
		}
	}
}

// parseRate parses the rate related headers.
func parseRate(r *http.Response) Rate {
	var rate Rate
	if limit := r.Header.Get(headerRateLimit); limit != "" {
		rate.Limit, _ = strconv.Atoi(limit)
	}
	if remaining := r.Header.Get(headerRateRemaining); remaining != "" {
		rate.Remaining, _ = strconv.Atoi(remaining)
	}
	if reset := r.Header.Get(headerRateReset); reset != "" {
		if v, _ := strconv.ParseInt(reset, 10, 64); v != 0 {
			rate.Reset = Timestamp{time.Unix(v, 0)}
		}
	}
	return rate
}

// Do sends an API request and returns the API response. The API response is
// JSON decoded and stored in the value pointed to by v, or returned as an
// error if an API error has occurred. If v implements the io.Writer
// interface, the raw response body will be written to v, without attempting to
// first decode it. If rate limit is exceeded and reset time is in the future,
// Do returns *RateLimitError immediately without making a network API call.
//
// The provided ctx must be non-nil. If it is canceled or times out,
// ctx.Err() will be returned.
func (c *Client) Do(ctx context.Context, req *http.Request, v interface{}) (*Response, error) {
	req = withContext(ctx, req)

	rateLimitCategory := category(req.URL.Path)

	// If we've hit rate limit, don't make further requests before Reset time.
	if err := c.checkRateLimitBeforeDo(req, rateLimitCategory); err != nil {
		return &Response{
			Response: err.Response,
			Rate:     err.Rate,
		}, err
	}

	resp, err := c.client.Do(req)
	if err != nil {
		// If we got an error, and the context has been canceled,
		// the context's error is probably more useful.
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
		}

		// If the error type is *url.Error, sanitize its URL before returning.
		if e, ok := err.(*url.Error); ok {
			if url, err := url.Parse(e.URL); err == nil {
				e.URL = sanitizeURL(url).String()
				return nil, e
			}
		}

		return nil, err
	}
	defer resp.Body.Close()

	response := newResponse(resp)

	c.rateMu.Lock()
	c.rateLimits[rateLimitCategory] = response.Rate
	c.rateMu.Unlock()

	err = CheckResponse(resp)
	if err != nil {
		// Special case for AcceptedErrors. If an AcceptedError
		// has been encountered, the response's payload will be
		// added to the AcceptedError and returned.
		//
		// Issue #1022
		aerr, ok := err.(*AcceptedError)
		if ok {
			b, readErr := ioutil.ReadAll(resp.Body)
			if readErr != nil {
				return response, readErr
			}

			aerr.Raw = b
			return response, aerr
		}

		return response, err
	}

	if v != nil {
		if w, ok := v.(io.Writer); ok {
			io.Copy(w, resp.Body)
		} else {
			decErr := json.NewDecoder(resp.Body).Decode(v)
			if decErr == io.EOF {
				decErr = nil // ignore EOF errors caused by empty response body
			}
			if decErr != nil {
				err = decErr
			}
		}
	}

	return response, err
}

// checkRateLimitBeforeDo does not make any network calls, but uses existing knowledge from
// current client state in order to quickly check if *RateLimitError can be immediately returned
// from Client.Do, and if so, returns it so that Client.Do can skip making a network API call unnecessarily.
// Otherwise it returns nil, and Client.Do should proceed normally.
func (c *Client) checkRateLimitBeforeDo(req *http.Request, rateLimitCategory rateLimitCategory) *RateLimitError {
	c.rateMu.Lock()
	rate := c.rateLimits[rateLimitCategory]
	c.rateMu.Unlock()
	if !rate.Reset.Time.IsZero() && rate.Remaining == 0 && time.Now().Before(rate.Reset.Time) {
		// Create a fake response.
		resp := &http.Response{
			Status:     http.StatusText(http.StatusForbidden),
			StatusCode: http.StatusForbidden,
			Request:    req,
			Header:     make(http.Header),
			Body:       ioutil.NopCloser(strings.NewReader("")),
		}
		return &RateLimitError{
			Rate:     rate,
			Response: resp,
			Message:  fmt.Sprintf("API rate limit of %v still exceeded until %v, not making remote request.", rate.Limit, rate.Reset.Time),
		}
	}

	return nil
}

/*
An ErrorResponse reports one or more errors caused by an API request.

GitHub API docs: https://developer.github.com/v3/#client-errors
*/
type ErrorResponse struct {
	Response *http.Response // HTTP response that caused this error
	Message  string         `json:"message"` // error message
	Errors   []Error        `json:"errors"`  // more detail on individual errors
	// Block is only populated on certain types of errors such as code 451.
	// See https://developer.github.com/changes/2016-03-17-the-451-status-code-is-now-supported/
	// for more information.
	Block *struct {
		Reason    string     `json:"reason,omitempty"`
		CreatedAt *Timestamp `json:"created_at,omitempty"`
	} `json:"block,omitempty"`
	// Most errors will also include a documentation_url field pointing
	// to some content that might help you resolve the error, see
	// https://developer.github.com/v3/#client-errors
	DocumentationURL string `json:"documentation_url,omitempty"`
}

func (r *ErrorResponse) Error() string {
	return fmt.Sprintf("%v %v: %d %v %+v",
		r.Response.Request.Method, sanitizeURL(r.Response.Request.URL),
		r.Response.StatusCode, r.Message, r.Errors)
}

// TwoFactorAuthError occurs when using HTTP Basic Authentication for a user
// that has two-factor authentication enabled. The request can be reattempted
// by providing a one-time password in the request.
type TwoFactorAuthError ErrorResponse

func (r *TwoFactorAuthError) Error() string { return (*ErrorResponse)(r).Error() }

// RateLimitError occurs when GitHub returns 403 Forbidden response with a rate limit
// remaining value of 0, and error message starts with "API rate limit exceeded for ".
type RateLimitError struct {
	Rate     Rate           // Rate specifies last known rate limit for the client
	Response *http.Response // HTTP response that caused this error
	Message  string         `json:"message"` // error message
}

func (r *RateLimitError) Error() string {
	return fmt.Sprintf("%v %v: %d %v %v",
		r.Response.Request.Method, sanitizeURL(r.Response.Request.URL),
		r.Response.StatusCode, r.Message, formatRateReset(r.Rate.Reset.Time.Sub(time.Now())))
}

// AcceptedError occurs when GitHub returns 202 Accepted response with an
// empty body, which means a job was scheduled on the GitHub side to process
// the information needed and cache it.
// Technically, 202 Accepted is not a real error, it's just used to
// indicate that results are not ready yet, but should be available soon.
// The request can be repeated after some time.
type AcceptedError struct {
	// Raw contains the response body.
	Raw []byte
}

func (*AcceptedError) Error() string {
	return "job scheduled on GitHub side; try again later"
}

// AbuseRateLimitError occurs when GitHub returns 403 Forbidden response with the
// "documentation_url" field value equal to "https://developer.github.com/v3/#abuse-rate-limits".
type AbuseRateLimitError struct {
	Response *http.Response // HTTP response that caused this error
	Message  string         `json:"message"` // error message

	// RetryAfter is provided with some abuse rate limit errors. If present,
	// it is the amount of time that the client should wait before retrying.
	// Otherwise, the client should try again later (after an unspecified amount of time).
	RetryAfter *time.Duration
}

func (r *AbuseRateLimitError) Error() string {
	return fmt.Sprintf("%v %v: %d %v",
		r.Response.Request.Method, sanitizeURL(r.Response.Request.URL),
		r.Response.StatusCode, r.Message)
}

// sanitizeURL redacts the client_secret parameter from the URL which may be
// exposed to the user.
func sanitizeURL(uri *url.URL) *url.URL {
	if uri == nil {
		return nil
	}
	params := uri.Query()
	if len(params.Get("client_secret")) > 0 {
		params.Set("client_secret", "REDACTED")
		uri.RawQuery = params.Encode()
	}
	return uri
}

/*
An Error reports more details on an individual error in an ErrorResponse.
These are the possible validation error codes:

    missing:
        resource does not exist
    missing_field:
        a required field on a resource has not been set
    invalid:
        the formatting of a field is invalid
    already_exists:
        another resource has the same valid as this field
    custom:
        some resources return this (e.g. github.User.CreateKey()), additional
        information is set in the Message field of the Error

GitHub API docs: https://developer.github.com/v3/#client-errors
*/
type Error struct {
	Resource string `json:"resource"` // resource on which the error occurred
	Field    string `json:"field"`    // field on which the error occurred
	Code     string `json:"code"`     // validation error code
	Message  string `json:"message"`  // Message describing the error. Errors with Code == "custom" will always have this set.
}

func (e *Error) Error() string {
	return fmt.Sprintf("%v error caused by %v field on %v resource",
		e.Code, e.Field, e.Resource)
}

// CheckResponse checks the API response for errors, and returns them if
// present. A response is considered an error if it has a status code outside
// the 200 range or equal to 202 Accepted.
// API error responses are expected to have either no response
// body, or a JSON response body that maps to ErrorResponse. Any other
// response body will be silently ignored.
//
// The error type will be *RateLimitError for rate limit exceeded errors,
// *AcceptedError for 202 Accepted status codes,
// and *TwoFactorAuthError for two-factor authentication errors.
func CheckResponse(r *http.Response) error {
	if r.StatusCode == http.StatusAccepted {
		return &AcceptedError{}
	}
	if c := r.StatusCode; 200 <= c && c <= 299 {
		return nil
	}
	errorResponse := &ErrorResponse{Response: r}
	data, err := ioutil.ReadAll(r.Body)
	if err == nil && data != nil {
		json.Unmarshal(data, errorResponse)
	}
	switch {
	case r.StatusCode == http.StatusUnauthorized && strings.HasPrefix(r.Header.Get(headerOTP), "required"):
		return (*TwoFactorAuthError)(errorResponse)
	case r.StatusCode == http.StatusForbidden && r.Header.Get(headerRateRemaining) == "0" && strings.HasPrefix(errorResponse.Message, "API rate limit exceeded for "):
		return &RateLimitError{
			Rate:     parseRate(r),
			Response: errorResponse.Response,
			Message:  errorResponse.Message,
		}
	case r.StatusCode == http.StatusForbidden && strings.HasSuffix(errorResponse.DocumentationURL, "/v3/#abuse-rate-limits"):
		abuseRateLimitError := &AbuseRateLimitError{
			Response: errorResponse.Response,
			Message:  errorResponse.Message,
		}
		if v := r.Header["Retry-After"]; len(v) > 0 {
			// According to GitHub support, the "Retry-After" header value will be
			// an integer which represents the number of seconds that one should
			// wait before resuming making requests.
			retryAfterSeconds, _ := strconv.ParseInt(v[0], 10, 64) // Error handling is noop.
			retryAfter := time.Duration(retryAfterSeconds) * time.Second
			abuseRateLimitError.RetryAfter = &retryAfter
		}
		return abuseRateLimitError
	default:
		return errorResponse
	}
}

// parseBoolResponse determines the boolean result from a GitHub API response.
// Several GitHub API methods return boolean responses indicated by the HTTP
// status code in the response (true indicated by a 204, false indicated by a
// 404). This helper function will determine that result and hide the 404
// error if present. Any other error will be returned through as-is.
func parseBoolResponse(err error) (bool, error) {
	if err == nil {
		return true, nil
	}

	if err, ok := err.(*ErrorResponse); ok && err.Response.StatusCode == http.StatusNotFound {
		// Simply false. In this one case, we do not pass the error through.
		return false, nil
	}

	// some other real error occurred
	return false, err
}

// Rate represents the rate limit for the current client.
type Rate struct {
	// The number of requests per hour the client is currently limited to.
	Limit int `json:"limit"`

	// The number of remaining requests the client can make this hour.
	Remaining int `json:"remaining"`

	// The time at which the current rate limit will reset.
	Reset Timestamp `json:"reset"`
}

func (r Rate) String() string {
	return Stringify(r)
}

// RateLimits represents the rate limits for the current client.
type RateLimits struct {
	// The rate limit for non-search API requests. Unauthenticated
	// requests are limited to 60 per hour. Authenticated requests are
	// limited to 5,000 per hour.
	//
	// GitHub API docs: https://developer.github.com/v3/#rate-limiting
	Core *Rate `json:"core"`

	// The rate limit for search API requests. Unauthenticated requests
	// are limited to 10 requests per minutes. Authenticated requests are
	// limited to 30 per minute.
	//
	// GitHub API docs: https://developer.github.com/v3/search/#rate-limit
	Search *Rate `json:"search"`
}

func (r RateLimits) String() string {
	return Stringify(r)
}

type rateLimitCategory uint8

const (
	coreCategory rateLimitCategory = iota
	searchCategory

	categories // An array of this length will be able to contain all rate limit categories.
)

// category returns the rate limit category of the endpoint, determined by Request.URL.Path.
func category(path string) rateLimitCategory {
	switch {
	default:
		return coreCategory
	case strings.HasPrefix(path, "/search/"):
		return searchCategory
	}
}

// RateLimits returns the rate limits for the current client.
func (c *Client) RateLimits(ctx context.Context) (*RateLimits, *Response, error) {
	req, err := c.NewRequest("GET", "rate_limit", nil)
	if err != nil {
		return nil, nil, err
	}

	response := new(struct {
		Resources *RateLimits `json:"resources"`
	})
	resp, err := c.Do(ctx, req, response)
	if err != nil {
		return nil, nil, err
	}

	if response.Resources != nil {
		c.rateMu.Lock()
		if response.Resources.Core != nil {
			c.rateLimits[coreCategory] = *response.Resources.Core
		}
		if response.Resources.Search != nil {
			c.rateLimits[searchCategory] = *response.Resources.Search
		}
		c.rateMu.Unlock()
	}

	return response.Resources, resp, nil
}

/*
UnauthenticatedRateLimitedTransport allows you to make unauthenticated calls
that need to use a higher rate limit associated with your OAuth application.

	t := &github.UnauthenticatedRateLimitedTransport{
		ClientID:     "your app's client ID",
		ClientSecret: "your app's client secret",
	}
	client := github.NewClient(t.Client())

This will append the querystring params client_id=xxx&client_secret=yyy to all
requests.

See https://developer.github.com/v3/#unauthenticated-rate-limited-requests for
more information.
*/
type UnauthenticatedRateLimitedTransport struct {
	// ClientID is the GitHub OAuth client ID of the current application, which
	// can be found by selecting its entry in the list at
	// https://github.com/settings/applications.
	ClientID string

	// ClientSecret is the GitHub OAuth client secret of the current
	// application.
	ClientSecret string

	// Transport is the underlying HTTP transport to use when making requests.
	// It will default to http.DefaultTransport if nil.
	Transport http.RoundTripper
}

// RoundTrip implements the RoundTripper interface.
func (t *UnauthenticatedRateLimitedTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	if t.ClientID == "" {
		return nil, errors.New("t.ClientID is empty")
	}
	if t.ClientSecret == "" {
		return nil, errors.New("t.ClientSecret is empty")
	}

	// To set extra querystring params, we must make a copy of the Request so
	// that we don't modify the Request we were given. This is required by the
	// specification of http.RoundTripper.
	//
	// Since we are going to modify only req.URL here, we only need a deep copy
	// of req.URL.
	req2 := new(http.Request)
	*req2 = *req
	req2.URL = new(url.URL)
	*req2.URL = *req.URL

	q := req2.URL.Query()
	q.Set("client_id", t.ClientID)
	q.Set("client_secret", t.ClientSecret)
	req2.URL.RawQuery = q.Encode()

	// Make the HTTP request.
	return t.transport().RoundTrip(req2)
}

// Client returns an *http.Client that makes requests which are subject to the
// rate limit of your OAuth application.
func (t *UnauthenticatedRateLimitedTransport) Client() *http.Client {
	return &http.Client{Transport: t}
}

func (t *UnauthenticatedRateLimitedTransport) transport() http.RoundTripper {
	if t.Transport != nil {
		return t.Transport
	}
	return http.DefaultTransport
}

// BasicAuthTransport is an http.RoundTripper that authenticates all requests
// using HTTP Basic Authentication with the provided username and password. It
// additionally supports users who have two-factor authentication enabled on
// their GitHub account.
type BasicAuthTransport struct {
	Username string // GitHub username
	Password string // GitHub password
	OTP      string // one-time password for users with two-factor auth enabled

	// Transport is the underlying HTTP transport to use when making requests.
	// It will default to http.DefaultTransport if nil.
	Transport http.RoundTripper
}

// RoundTrip implements the RoundTripper interface.
func (t *BasicAuthTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	// To set extra headers, we must make a copy of the Request so
	// that we don't modify the Request we were given. This is required by the
	// specification of http.RoundTripper.
	//
	// Since we are going to modify only req.Header here, we only need a deep copy
	// of req.Header.
	req2 := new(http.Request)
	*req2 = *req
	req2.Header = make(http.Header, len(req.Header))
	for k, s := range req.Header {
		req2.Header[k] = append([]string(nil), s...)
	}

	req2.SetBasicAuth(t.Username, t.Password)
	if t.OTP != "" {
		req2.Header.Set(headerOTP, t.OTP)
	}
	return t.transport().RoundTrip(req2)
}

// Client returns an *http.Client that makes requests that are authenticated
// using HTTP Basic Authentication.
func (t *BasicAuthTransport) Client() *http.Client {
	return &http.Client{Transport: t}
}

func (t *BasicAuthTransport) transport() http.RoundTripper {
	if t.Transport != nil {
		return t.Transport
	}
	return http.DefaultTransport
}

// formatRateReset formats d to look like "[rate reset in 2s]" or
// "[rate reset in 87m02s]" for the positive durations. And like "[rate limit was reset 87m02s ago]"
// for the negative cases.
func formatRateReset(d time.Duration) string {
	isNegative := d < 0
	if isNegative {
		d *= -1
	}
	secondsTotal := int(0.5 + d.Seconds())
	minutes := secondsTotal / 60
	seconds := secondsTotal - minutes*60

	var timeString string
	if minutes > 0 {
		timeString = fmt.Sprintf("%dm%02ds", minutes, seconds)
	} else {
		timeString = fmt.Sprintf("%ds", seconds)
	}

	if isNegative {
		return fmt.Sprintf("[rate limit was reset %v ago]", timeString)
	}
	return fmt.Sprintf("[rate reset in %v]", timeString)
}

// Bool is a helper routine that allocates a new bool value
// to store v and returns a pointer to it.
func Bool(v bool) *bool { return &v }

// Int is a helper routine that allocates a new int value
// to store v and returns a pointer to it.
func Int(v int) *int { return &v }

// Int64 is a helper routine that allocates a new int64 value
// to store v and returns a pointer to it.
func Int64(v int64) *int64 { return &v }

// String is a helper routine that allocates a new string value
// to store v and returns a pointer to it.
func String(v string) *string { return &v }