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// Package github is a mini-library for querying the GitHub v3 API that
// takes care of authentication (with tokens only) and pagination.
package github
import (
"encoding/json"
"fmt"
"io"
"net/http"
"net/url"
"os"
"reflect"
"github.com/kevinburke/rest/restclient"
"github.com/tomnomnom/linkheader"
)
const DefaultBaseURL = "https://api.github.com"
// Set to values > 0 to control verbosity, for debugging.
var VERBOSITY = 0
// DoAuthRequest ...
//
// TODO: This function is amazingly ugly (separate headers, token, no API
// URL constructions, et cetera).
func DoAuthRequest(method, url, mime, token string, headers map[string]string, body io.Reader) (*http.Response, error) {
req, err := newAuthRequest(method, url, mime, token, headers, body)
if err != nil {
return nil, err
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return nil, err
}
return resp, nil
}
// Client collects a few options that can be set when contacting the GitHub
// API, such as authorization tokens. Methods called on Client will supply
// these options when calling the API.
type Client struct {
client *restclient.Client
}
// NewClient creates a new Client for use with the Github API.
func NewClient(username, token string, client *restclient.Client) Client {
c := Client{}
if client == nil {
c.client = restclient.New(username, token, DefaultBaseURL)
} else {
c.client = client
}
return c
}
// SetBaseURL updates the client's base URL, if baseurl is a non-empty value.
func (c Client) SetBaseURL(baseurl string) {
// This is lazy, because the caller always tries to override the base URL
// with EnvApiEndpoint and we used to ignore that at the top of Get, but we
// don't do that now. So instead just filter out/ignore the empty string.
if baseurl == "" {
return
}
c.client.Base = baseurl
}
// Get fetches uri (relative URL) from the GitHub API and unmarshals the
// response into v. It takes care of pagination transparantly.
func (c Client) Get(uri string, v interface{}) error {
rc, err := c.getPaginated(uri)
if err != nil {
return err
}
defer rc.Close()
var r io.Reader = rc
if VERBOSITY > 0 {
vprintln("BODY:")
r = io.TeeReader(rc, os.Stderr)
}
// Github may return paginated responses. If so, githubGetPaginated will
// return a reader which yields the concatenation of all pages. These
// reponses are _separate_ JSON arrays. Standard json.Unmarshal() or
// json.Decoder.Decode() will not have the expected result when
// unmarshalling into v. For example, a 2-page response:
//
// 1. [{...}, {...}, {...}]
// 2. [{...}]
//
// If v is a slice type, we'd like to decode the four objects from the
// two pages into a single slice. However, if we just use
// json.Decoder.Decode(), that won't work. v will be overridden each
// time.
//
// For this reason, we use two very ugly things.
//
// 1. We analyze v with reflect to see if it's a slice.
// 2. If so, we use the json.Decoder token API and reflection to
// dynamically add new elements into the slice, ignoring the
// boundaries between JSON arrays.
//
// This is a lot of work, and feels very stupid. An alternative would be
// removing the outermost ][ in the intermediate responses, which would
// be even more finnicky. Another alternative would be to explicitly
// expose a pagination API, forcing clients of this code to deal with
// it. That's how the go-github library does it. But why solve a problem
// sensibly if one can power through it with reflection (half-joking)?
sl := reflect.Indirect(reflect.ValueOf(v)) // Get the reflect.Value of the slice so we can append to it.
t := sl.Type()
if t.Kind() != reflect.Slice {
// Not a slice, not going to handle special pagination JSON stream
// semantics since it likely wouldn't work properly anyway. If this
// is a non-paginated stream, it should work.
return json.NewDecoder(r).Decode(v)
}
t = t.Elem() // Extract the type of the slice's elements.
// Use streaming Token API to append all elements of the JSON stream
// arrays (pagination) to the slice.
for dec := json.NewDecoder(r); ; {
tok, err := dec.Token()
if err != nil {
if err == io.EOF {
return nil // Natural end of the JSON stream.
}
return err
}
vprintf("TOKEN %T: %v\n", tok, tok)
// Check for tokens until we get an opening array brace. If we're
// not in an array, we can't decode an array element later, which
// would result in an error.
if tok != json.Delim('[') {
continue
}
// Read the array, appending all elements to the slice.
for dec.More() {
it := reflect.New(t) // Interface to a valid pointer to an object of the same type as the slice elements.
if err := dec.Decode(it.Interface()); err != nil {
return err
}
vprintf("OBJECT %T: %v\n", it.Interface(), it)
sl.Set(reflect.Append(sl, it.Elem()))
}
}
}
var defaultHttpClient *http.Client
func init() {
defaultHttpClient = &http.Client{
Transport: restclient.DefaultTransport,
}
}
// Caller is responsible for reading and closing the response body.
func (c Client) Do(r *http.Request) (*http.Response, error) {
// Pulled this out of client.go:Do because we need to read the response
// headers.
var res *http.Response
var err error
if c.client.Client == nil {
res, err = defaultHttpClient.Do(r)
} else {
res, err = c.client.Client.Do(r)
}
if err != nil {
return nil, err
}
if res.StatusCode >= 400 {
// both of these consume res.Body
if c.client.ErrorParser != nil {
return nil, c.client.ErrorParser(res)
}
return nil, restclient.DefaultErrorParser(res)
}
return res, nil
}
const uaPart = "github-release/" + VERSION
func (c Client) NewRequest(method, uri string, body io.Reader) (*http.Request, error) {
req, err := c.client.NewRequest(method, uri, body)
if err != nil {
return nil, err
}
ua := req.Header.Get("User-Agent")
if ua == "" {
req.Header.Set("User-Agent", uaPart)
} else {
req.Header.Set("User-Agent", uaPart+" "+ua)
}
return req, nil
}
// getPaginated returns a reader that yields the concatenation of the
// paginated responses to a query (URI).
//
// TODO: Rework the API so we can cleanly append per_page=100 as a URL
// parameter.
func (c Client) getPaginated(uri string) (io.ReadCloser, error) {
// Parse the passed-in URI to make sure we don't lose any values when
// setting our own params.
u, err := url.Parse(uri)
if err != nil {
return nil, err
}
v := u.Query()
v.Set("per_page", "100") // The default is 30, this makes it less likely for Github to rate-limit us.
u.RawQuery = v.Encode()
req, err := c.NewRequest("GET", u.String(), nil)
if err != nil {
return nil, err
}
resp, err := c.Do(req)
if err != nil {
return nil, err
}
vprintln("GET (top-level)", resp.Request.URL, "->", resp)
// If the HTTP response is paginated, it will contain a Link header.
links := linkheader.Parse(resp.Header.Get("Link"))
if len(links) == 0 {
return resp.Body, nil // No pagination.
}
// In this case, fetch all pages and concatenate them.
r, w := io.Pipe()
done := make(chan struct{}) // Backpressure from the pipe writer.
responses := make(chan *http.Response, 5) // Allow 5 concurrent HTTP requests.
responses <- resp
// URL fetcher goroutine. Fetches paginated responses until no more
// pages can be found. Closes the write end of the pipe if fetching a
// page fails.
go func() {
defer close(responses) // Signal that no more requests are coming.
for len(links) > 0 {
nextLinkURL := nextLink(links)
if nextLinkURL == "" {
return // We're done.
}
req, err := c.NewRequest("GET", nextLinkURL, nil)
if err != nil {
w.CloseWithError(err)
return
}
resp, err := c.Do(req)
if err != nil {
w.CloseWithError(err)
return
}
links = linkheader.Parse(resp.Header.Get("Link"))
if err != nil {
w.CloseWithError(err)
return
}
select {
case <-done:
return // The body concatenator goroutine signals it has stopped.
case responses <- resp: // Schedule the request body to be written to the pipe.
}
}
}()
// Body concatenator goroutine. Writes each response into the pipe
// sequentially. Closes the write end of the pipe if the HTTP status is
// not 200 or the body can't be read.
go func() {
defer func() {
// Drain channel and close bodies, stop leaks.
for resp := range responses {
resp.Body.Close()
}
}()
defer close(done) // Signal that we're done writing all requests, or an error occurred.
for resp := range responses {
if resp.StatusCode != http.StatusOK {
resp.Body.Close()
w.CloseWithError(fmt.Errorf("expected '200 OK' but received '%v' (%s to %s)", resp.Status, resp.Request.Method, resp.Request.URL.Path))
return
}
_, err := io.Copy(w, resp.Body)
resp.Body.Close()
if err != nil {
vprintln("error: io.Copy: ", err)
w.CloseWithError(err)
return
}
}
w.Close()
}()
return r, nil
}
// Create a new request that sends the auth token.
func newAuthRequest(method, url, mime, token string, headers map[string]string, body io.Reader) (*http.Request, error) {
vprintln("creating request:", method, url, mime, token)
var n int64 // content length
var err error
if f, ok := body.(*os.File); ok {
// Retrieve the content-length and buffer up if necessary.
body, n, err = materializeFile(f)
if err != nil {
return nil, err
}
}
// TODO find all of the usages and replace with the Client.
req, err := http.NewRequest(method, url, body)
if err != nil {
return nil, err
}
req.SetBasicAuth("", token)
req.Header.Set("User-Agent", uaPart)
// net/http automatically does this if req.Body is of type
// (bytes.Reader|bytes.Buffer|strings.Reader). Sadly, we also need to
// handle *os.File.
if n != 0 {
vprintln("setting content-length to", n)
req.ContentLength = n
}
if mime != "" {
req.Header.Set("Content-Type", mime)
}
for k, v := range headers {
req.Header.Set(k, v)
}
return req, nil
}
// nextLink returns the HTTP header Link annotated with 'next', "" otherwise.
func nextLink(links linkheader.Links) string {
for _, link := range links {
if link.Rel == "next" && link.URL != "" {
return link.URL
}
}
return ""
}
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