Monorail client in Go

go/src/infra/monorail/endpoints.go

Index: go/src/infra/monorail/endpoints.go
diff --git a/go/src/infra/monorail/endpoints.go b/go/src/infra/monorail/endpoints.go
new file mode 100644
index 0000000000000000000000000000000000000000..fffac476a774b97aacd7a92689db71aea2a3ed1f
--- /dev/null
+++ b/go/src/infra/monorail/endpoints.go
@@ -0,0 +1,130 @@
+// Copyright 2016 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 monorail
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"strings"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/context/ctxhttp"
+	"google.golang.org/grpc"
+
+	"github.com/luci/luci-go/common/clock"
+	"github.com/luci/luci-go/common/errors"
+	"github.com/luci/luci-go/common/logging"
+)
+
+// epClient implements MonorailClient by sending requests to Monorail's
+// Cloud Endpoints API.
+// See https://monorail-staging.appspot.com/_ah/api/explorer#p/monorail/v1/
+type epClient struct {
+	HTTP *http.Client
+	// url is root of API without trailing slash,
+	// e.g. "https://monorail-staging.appspot.com/_ah/api/monorail/v1"
+	url string
+}
+
+// NewEndpointsClient creates a MonorailClient that send requests to
+// Monorail Cloud Endpoints API at url.
+//
+// Example of url: "https://monorail-staging.appspot.com/_ah/api/monorail/v1"
+//
+// Methods do not implement retries.
+// Use "github.com/luci/luci-go/common/errors".IsTransient to check
+// if an error is transient.
+//
+// Client methods return an error on any grpc.CallOption.
+func NewEndpointsClient(client *http.Client, url string) MonorailClient {
+	return &epClient{HTTP: client, url: strings.TrimSuffix(url, "/")}
+}
+
+func (c *epClient) call(ctx context.Context, urlSuffix string, request, response interface{}) error {
+	client := c.HTTP
+	if client == nil {
+		client = http.DefaultClient
+	}
+
+	// Limit ctx deadline to timeout set in client.
+	if client.Timeout > 0 {
+		clientDeadline := clock.Now(ctx).Add(client.Timeout)
+		if deadline, ok := ctx.Deadline(); !ok || deadline.After(clientDeadline) {
+			ctx, _ = context.WithDeadline(ctx, clientDeadline)
+		}
+	}
+
+	// Convert request object to JSON.
+	reqBuf := &bytes.Buffer{}
+	if request != nil {
+		if err := json.NewEncoder(reqBuf).Encode(request); err != nil {
+			return err
+		}
+	}
+
+	// Make an HTTP request.
+	req, err := http.NewRequest("POST", c.url + urlSuffix, reqBuf)
+	if err != nil {
+		return fmt.Errorf("could not make a request to %s: %s", req.URL, err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "application/json")
+
+	// Send the request.
+	logging.Debugf(ctx, "POST %s %s", req.URL, reqBuf.Bytes())
+	res, err := ctxhttp.Do(ctx, client, req)
+	if err != nil {
+		return errors.WrapTransient(err)
+	}
+	defer res.Body.Close()
+
+	// Check HTTP status code.
+	if res.StatusCode != http.StatusOK {
+		text, _ := ioutil.ReadAll(io.LimitReader(res.Body, 1024))
+		err := fmt.Errorf("unexpected status %q. Response: %s", res.Status, text)
+		if res.StatusCode == http.StatusNotFound || res.StatusCode > 500 {
+			// Cloud Endpoints often flake with HTTP 404.
+			// Treat such responses transient errors.
+			err = errors.WrapTransient(err)
+		}
+		return err
+	}
+
+	if response == nil {
+		return nil
+	}
+	return json.NewDecoder(res.Body).Decode(response)
+}
+
+func (c *epClient) InsertIssue(ctx context.Context, req *InsertIssueRequest, options ...grpc.CallOption) (*InsertIssueResponse, error) {
+	if err := checkOptions(options); err != nil {
+		return nil, err
+	}
+	if err := req.Validate(); err != nil {
+		return nil, err
+	}
+	url := fmt.Sprintf("/projects/%s/issues?sendEmail=%v", req.ProjectId, req.SendEmail)
+	res := &InsertIssueResponse{&Issue{}}
+	return res, c.call(ctx, url, &req.Issue, res.Issue)
+}
+
+func (c *epClient) InsertComment(ctx context.Context, req *InsertCommentRequest, options ...grpc.CallOption) (*InsertCommentResponse, error) {
+	if err := checkOptions(options); err != nil {
+		return nil, err
+	}
+	url := fmt.Sprintf("/projects/%s/issues/%d/comments", req.Issue.ProjectId, req.Issue.IssueId)
+	return &InsertCommentResponse{}, c.call(ctx, url, req.Comment, nil)
+}
+
+func checkOptions(options []grpc.CallOption) error {
+	if len(options) > 0 {
+		return errGrpcOptions
+	}
+	return nil
+}