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go/src/infra/libs/gitiles/gitiles.go

Index: go/src/infra/libs/gitiles/gitiles.go
diff --git a/go/src/infra/libs/gitiles/gitiles.go b/go/src/infra/libs/gitiles/gitiles.go
new file mode 100644
index 0000000000000000000000000000000000000000..955117b839243a31095ef2a57b4e126d4984aeb8
--- /dev/null
+++ b/go/src/infra/libs/gitiles/gitiles.go
@@ -0,0 +1,189 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+package gitiles
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"reflect"
+	"strings"
+)
+
+// Gitiles wraps one Gitiles server. Use NewGitiles to create one.
+type Gitiles struct {
+	url      string
+	requests chan<- request
+}
+
+// URL returns the base url for this Gitiles service wrapper
+func (g Gitiles) URL() string { return g.url }
+
+// NewGitiles creates a new Gitiles instance for the given |url|, and a maximum
+// number of concurrent requests.
+func NewGitiles(url string, maxConnections int) *Gitiles {

[Vadim Sh., 2014/10/21 15:27:00]

there's some idiomatic Go way to support HTTP midleware (like OAuth
authentication), some set of interfaces... e.g.. instead of 'url' you can accept
Transport or HttpClient or something like that (I do not remember).

tl;dr this stuff doesn't work with non-public repos?

+	// TODO(iannucci): make a separate http.Client?
+	// TODO(iannucci): have a way to destroy the Gitiles instance?
+	requestChan := make(chan request, maxConnections)
+	ret := &Gitiles{
+		url:      strings.TrimRight(url, "/"),
+		requests: requestChan,
+	}
+	for i := 0; i < maxConnections; i++ {

[Vadim Sh., 2014/10/21 15:27:00]

Isn't there built in connection pool? :(

+		go ret.requestProcessor(requestChan)
+	}
+	return ret
+}
+
+// StatusError is a simple error type which wraps a Http StatusCode.
+type StatusError int
+
+// Bad returns true iff the status code is not 2XX
+func (s StatusError) Bad() bool     { return s < 200 || s >= 300 }
+func (s StatusError) Error() string { return fmt.Sprintf("got status code %d", s) }
+
+// JSON Returns an instance of target or an error.
+//
+// Example:
+//   data := map[string]int{}
+//   result, err := g.JSON(data, "some", "url", "pieces")
+//   if err != nil { panic(err) }
+//   data = *result.(*map[string]int)
+func (g *Gitiles) JSON(target interface{}, pieces ...string) (interface{}, error) {
+	reply := make(chan jsonResult, 1)
+	g.requests <- jsonRequest{
+		strings.Join(pieces, "/"),
+		reflect.TypeOf(target),
+		reply,
+	}
+	rslt := <-reply
+	return rslt.dataPtr, rslt.err
+}
+
+// Text returns the decoded text data or an error. It will load the given path
+// with format=TEXT and apply the base64 decoding.
+func (g *Gitiles) Text(pieces ...string) ([]byte, error) {
+	reply := make(chan textResult, 1)
+	g.requests <- textRequest{
+		strings.Join(pieces, "/"),
+		reply,
+	}
+	rslt := <-reply
+	return rslt.data, rslt.err
+}
+
+// private decoders
+type textResult struct {
+	err  error
+	data []byte
+}
+
+type jsonResult struct {
+	err     error
+	dataPtr interface{}
+}
+
+type request interface {
+	Process(rsp *http.Response, err error)
+	Method() string
+	URLPath() string
+	Body() io.Reader
+}
+
+type jsonRequest struct {
+	urlPath    string
+	typ        reflect.Type
+	resultChan chan<- jsonResult
+}
+
+func (j jsonRequest) URLPath() string { return j.urlPath + "?format=JSON" }
+func (j jsonRequest) Method() string  { return "GET" }
+func (j jsonRequest) Body() io.Reader { return nil }
+
+func (j jsonRequest) Process(resp *http.Response, err error) {
+	var rslt jsonResult
+	if err != nil {
+		rslt.err = err
+	} else {
+		bufreader := bufio.NewReader(resp.Body)
+		firstFour, err := bufreader.Peek(4)
+		if err != nil {
+			rslt.err = err
+		} else {
+			if bytes.Equal(firstFour, []byte(")]}'")) {
+				bufreader.Read(make([]byte, 4))
+			}
+
+			data := reflect.New(j.typ).Interface()
+			err = json.NewDecoder(bufreader).Decode(data)
+			if err != nil {
+				rslt.err = err
+			} else {
+				rslt.dataPtr = data
+			}
+		}
+	}
+	j.resultChan <- rslt
+}
+
+type textRequest struct {
+	urlPath    string
+	resultChan chan<- textResult
+}
+
+func (t textRequest) URLPath() string { return t.urlPath + "?format=TEXT" }
+func (t textRequest) Method() string  { return "GET" }
+func (t textRequest) Body() io.Reader { return nil }
+
+func (t textRequest) internalProcess(rsp *http.Response, err error) ([]byte, error) {
+	if err != nil {
+		return nil, err
+	}
+	return ioutil.ReadAll(base64.NewDecoder(base64.StdEncoding, rsp.Body))
+}
+
+func (t textRequest) Process(rsp *http.Response, err error) {
+	if data, err := t.internalProcess(rsp, err); err != nil {
+		t.resultChan <- textResult{err: err}
+	} else {
+		t.resultChan <- textResult{data: data}
+	}
+}
+
+func (g *Gitiles) requestProcessor(queue <-chan request) {
+	// Launched as a goroutine to avoid blocking the request processor.
+	for r := range queue {
+		r := r
+		if r == nil {
+			continue
+		}
+
+		var req *http.Request
+		req, err := http.NewRequest(r.Method(), g.url+"/"+r.URLPath(), r.Body())
+		if err != nil {
+			r.Process(nil, err)
+			continue
+		}
+
+		rsp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			r.Process(nil, err)
+			continue
+		}
+
+		e := StatusError(rsp.StatusCode)
+		if e.Bad() {
+			err = e
+		}
+		func() {
+			defer rsp.Body.Close()
+			r.Process(rsp, err)
+		}()
+	}
+}