feat(provider): implement change provider interface with GitHub integration

- Add ChangeProvider interface and GitHub implementation
- Use Client wrapper pattern with configurable auth
- Add tests for the change provider

Author: rashmi-prithyani

example/server/orchestrator/BUILD.bazel

@@ -13,6 +13,8 @@ go_library(
     deps = [
         "//core/consumer",
         "//entity",
+        "//extension/changeprovider",
+        "//extension/changeprovider/github",
         "//extension/counter",
         "//extension/counter/mysql",
         "//extension/mergechecker",

example/server/orchestrator/main.go

@@ -31,6 +31,8 @@ import (
 	"github.com/uber-go/tally/v4"
 	"github.com/uber/submitqueue/core/consumer"
 	"github.com/uber/submitqueue/entity"
+	"github.com/uber/submitqueue/extension/changeprovider"
+	githubprovider "github.com/uber/submitqueue/extension/changeprovider/github"
 	"github.com/uber/submitqueue/extension/counter"
 	mysqlcounter "github.com/uber/submitqueue/extension/counter/mysql"
 	"github.com/uber/submitqueue/extension/mergechecker"
@@ -190,8 +192,11 @@ func run() error {
 	// Create merge checker
 	mc := newMergeChecker(logger, scope)
 
+	// Create change provider
+	cp := newChangeProvider(logger, scope)
+
 	// Register controllers
-	if err := registerControllers(c, logger.Sugar(), scope, registry, mc, cnt, store); err != nil {
+	if err := registerControllers(c, logger.Sugar(), scope, registry, mc, cp, cnt, store); err != nil {
 		return err
 	}
 
@@ -376,7 +381,7 @@ func newTopicRegistry(q extqueue.Queue, subscriberName string) (consumer.TopicRe
 //                                        │        │                        │
 //                                        └────────┴────────────────────────┘
 
-func registerControllers(c consumer.Consumer, logger *zap.SugaredLogger, scope tally.Scope, registry consumer.TopicRegistry, mc mergechecker.MergeChecker, cnt counter.Counter, store storage.Storage) error {
+func registerControllers(c consumer.Consumer, logger *zap.SugaredLogger, scope tally.Scope, registry consumer.TopicRegistry, mc mergechecker.MergeChecker, cp changeprovider.ChangeProvider, cnt counter.Counter, store storage.Storage) error {
 	requestController := start.NewController(
 		logger,
 		scope,
@@ -395,6 +400,7 @@ func registerControllers(c consumer.Consumer, logger *zap.SugaredLogger, scope t
 		store,
 		registry,
 		mc,
+		cp,
 		consumer.TopicKeyValidate,
 		"orchestrator-validate",
 	)
@@ -514,6 +520,36 @@ func registerControllers(c consumer.Consumer, logger *zap.SugaredLogger, scope t
 	return nil
 }
 
+// getEnv returns environment variable value or default if not set.
+func getEnv(key, defaultVal string) string {
+	if val := os.Getenv(key); val != "" {
+		return val
+	}
+	return defaultVal
+}
+
+// parseTimeout parses a duration from environment variable with fallback to default.
+// Returns defaultVal if envVal is empty or cannot be parsed.
+func parseTimeout(envVal string, defaultVal time.Duration) time.Duration {
+	if envVal == "" {
+		return defaultVal
+	}
+	if d, err := time.ParseDuration(envVal); err == nil {
+		return d
+	}
+	return defaultVal
+}
+
+// buildGitHubHTTPClient creates an http.Client configured for GitHub API calls.
+// Configures timeout and optional bearer token authentication.
+func buildGitHubHTTPClient(token string, timeout time.Duration) *http.Client {
+	httpClient := &http.Client{Timeout: timeout}
+	if token != "" {
+		httpClient.Transport = &bearerTransport{token: token}
+	}
+	return httpClient
+}
+
 // newMergeChecker creates a MergeChecker for GitHub (github.com).
 // Configured via GITHUB_TOKEN and GITHUB_GRAPHQL_URL environment variables.
 func newMergeChecker(logger *zap.Logger, scope tally.Scope) mergechecker.MergeChecker {
@@ -539,6 +575,26 @@ func newMergeChecker(logger *zap.Logger, scope tally.Scope) mergechecker.MergeCh
 	})
 }
 
+// newChangeProvider creates a ChangeProvider for GitHub (github.com).
+// Configured via GITHUB_BASE_URL, GITHUB_TOKEN, and GITHUB_TIMEOUT environment variables.
+// Uses pure dependency injection - creates http.Client with auth configured in Transport.
+func newChangeProvider(logger *zap.Logger, scope tally.Scope) changeprovider.ChangeProvider {
+	// 1. Read configuration from environment
+	baseURL := getEnv("GITHUB_BASE_URL", "https://api.github.com")
+	token := os.Getenv("GITHUB_TOKEN")
+	timeout := parseTimeout(os.Getenv("GITHUB_TIMEOUT"), 30*time.Second)
+
+	// 2. Build HTTP client with caller-controlled config (auth + timeout)
+	httpClient := buildGitHubHTTPClient(token, timeout)
+
+	// 3. Inject into provider
+	return githubprovider.NewProvider(githubprovider.Params{
+		Client:       githubprovider.NewClient(httpClient, baseURL),
+		Logger:       logger.Sugar(),
+		MetricsScope: scope.SubScope("changeprovider"),
+	})
+}
+
 // bearerTransport is an http.RoundTripper that adds a Bearer token to requests.
 type bearerTransport struct {
 	token string

extension/changeprovider/change_provider.go

@@ -44,8 +44,9 @@ type ChangedFile struct {
 
 // ChangeInfo contains metadata and file changes for a code change.
 type ChangeInfo struct {
-	// ID is the change identifier (e.g., "PR: uber-code/go-code/1" or "diff: uber-code/go-code/D1").
-	ID string
+	// URI is the full change URI for correlation with the input request
+	// (e.g., "github://uber/repo/98/abc123sha" or "phab://D123/xyz789").
+	URI string
 	// User is the author of the change.
 	User User
 	// ChangedFiles is the list of files modified in this change. Order is unspecified.
@@ -56,6 +57,7 @@ type ChangeInfo struct {
 // Each implementation is configured for a specific provider (GitHub, GitLab, Phabricator).
 type ChangeProvider interface {
 	// Get retrieves change information for the provided Change.
-	// Returns the change info containing metadata and file changes.
-	Get(ctx context.Context, change entity.Change) (ChangeInfo, error)
+	// For a Change with multiple URIs (e.g., stacked PRs), returns one ChangeInfo per URI.
+	// Returns a slice of ChangeInfo, one for each change in the stack.
+	Get(ctx context.Context, change entity.Change) ([]ChangeInfo, error)
 }

extension/changeprovider/github/BUILD.bazel

@@ -0,0 +1,42 @@
+load("@rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "github",
+    srcs = [
+        "config.go",
+        "convert.go",
+        "graphql.go",
+        "provider.go",
+        "validate.go",
+    ],
+    importpath = "github.com/uber/submitqueue/extension/changeprovider/github",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//core/metrics",
+        "//entity",
+        "//entity/github",
+        "//extension/changeprovider",
+        "@com_github_uber_go_tally_v4//:tally",
+        "@org_uber_go_zap//:zap",
+    ],
+)
+
+go_test(
+    name = "github_test",
+    srcs = [
+        "config_test.go",
+        "graphql_test.go",
+        "provider_test.go",
+        "validate_test.go",
+    ],
+    embed = [":github"],
+    deps = [
+        "//entity",
+        "//entity/github",
+        "//extension/changeprovider",
+        "@com_github_stretchr_testify//assert",
+        "@com_github_stretchr_testify//require",
+        "@com_github_uber_go_tally_v4//:tally",
+        "@org_uber_go_zap//zaptest",
+    ],
+)

extension/changeprovider/github/config.go

@@ -0,0 +1,47 @@
+package github
+
+import (
+	"net/http"
+)
+
+// Client is a GitHub API client that encapsulates connection details and authentication.
+// The client is protocol-agnostic - it provides helpers for both GraphQL and REST endpoints.
+type Client struct {
+	httpClient *http.Client
+	baseURL    string
+}
+
+// NewClient creates a new GitHub API client with a pre-configured HTTP client.
+// The caller is responsible for configuring authentication in the HTTP client's Transport.
+//
+// Parameters:
+// - httpClient: Configured HTTP client (with auth, timeout, transport, etc.)
+// - baseURL: GitHub instance base URL (e.g., "https://api.github.com" or "https://ghe.company.com/api")
+func NewClient(httpClient *http.Client, baseURL string) *Client {
+	return &Client{
+		httpClient: httpClient,
+		baseURL:    baseURL,
+	}
+}
+
+// HTTPClient returns the configured HTTP client.
+func (c *Client) HTTPClient() *http.Client {
+	return c.httpClient
+}
+
+// BaseURL returns the configured GitHub base URL.
+func (c *Client) BaseURL() string {
+	return c.baseURL
+}
+
+// GraphQLURL returns the GitHub GraphQL endpoint URL.
+// Constructs the URL by appending "/graphql" to the base URL.
+func (c *Client) GraphQLURL() string {
+	return c.baseURL + "/graphql"
+}
+
+// RESTURL constructs a GitHub REST API endpoint URL.
+// The path should start with "/" (e.g., "/repos/uber/submitqueue/pulls/123").
+func (c *Client) RESTURL(path string) string {
+	return c.baseURL + path
+}

extension/changeprovider/github/config_test.go

@@ -0,0 +1,97 @@
+package github
+
+import (
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewClient(t *testing.T) {
+	httpClient := &http.Client{Timeout: 30 * time.Second}
+	baseURL := "https://api.github.com"
+
+	client := NewClient(httpClient, baseURL)
+
+	assert.NotNil(t, client)
+	assert.Equal(t, httpClient, client.HTTPClient())
+	assert.Equal(t, baseURL, client.BaseURL())
+}
+
+func TestClient_GraphQLURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		baseURL  string
+		expected string
+	}{
+		{
+			name:     "standard github",
+			baseURL:  "https://api.github.com",
+			expected: "https://api.github.com/graphql",
+		},
+		{
+			name:     "github enterprise",
+			baseURL:  "https://ghe.example.com/api",
+			expected: "https://ghe.example.com/api/graphql",
+		},
+		{
+			name:     "localhost",
+			baseURL:  "http://localhost:8080",
+			expected: "http://localhost:8080/graphql",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			client := NewClient(&http.Client{}, tt.baseURL)
+			assert.Equal(t, tt.expected, client.GraphQLURL())
+		})
+	}
+}
+
+func TestClient_BaseURL(t *testing.T) {
+	tests := []struct {
+		name    string
+		baseURL string
+	}{
+		{name: "standard github", baseURL: "https://api.github.com"},
+		{name: "github enterprise", baseURL: "https://ghe.example.com/api"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			client := NewClient(&http.Client{}, tt.baseURL)
+			assert.Equal(t, tt.baseURL, client.BaseURL())
+		})
+	}
+}
+
+func TestClient_RESTURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		baseURL  string
+		path     string
+		expected string
+	}{
+		{
+			name:     "repos endpoint",
+			baseURL:  "https://api.github.com",
+			path:     "/repos/uber/submitqueue/pulls/123",
+			expected: "https://api.github.com/repos/uber/submitqueue/pulls/123",
+		},
+		{
+			name:     "enterprise repos endpoint",
+			baseURL:  "https://ghe.example.com/api",
+			path:     "/repos/myorg/myrepo/pulls/456",
+			expected: "https://ghe.example.com/api/repos/myorg/myrepo/pulls/456",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			client := NewClient(&http.Client{}, tt.baseURL)
+			assert.Equal(t, tt.expected, client.RESTURL(tt.path))
+		})
+	}
+}

extension/changeprovider/github/convert.go

@@ -0,0 +1,42 @@
+package github
+
+import (
+	entitygithub "github.com/uber/submitqueue/entity/github"
+	"github.com/uber/submitqueue/extension/changeprovider"
+)
+
+// convertToChangeInfo converts GitHub PR data to ChangeInfo.
+func convertToChangeInfo(parsed entitygithub.ChangeID, prData *pullRequestData) changeprovider.ChangeInfo {
+	changedFiles := convertFiles(prData.Files.Nodes)
+
+	return changeprovider.ChangeInfo{
+		URI: parsed.String(),
+		User: changeprovider.User{
+			Name:  prData.Author.Name,
+			Email: prData.Author.Email,
+		},
+		ChangedFiles: changedFiles,
+	}
+}
+
+// convertFiles converts GitHub file nodes to ChangedFile structs.
+func convertFiles(nodes []fileNode) []changeprovider.ChangedFile {
+	changedFiles := make([]changeprovider.ChangedFile, 0, len(nodes))
+
+	for _, file := range nodes {
+		linesModified := 0
+		if file.Additions > 0 && file.Deletions > 0 {
+			linesModified = min(file.Additions, file.Deletions)
+		}
+
+		changedFiles = append(changedFiles, changeprovider.ChangedFile{
+			Path:          file.Path,
+			Patch:         file.Patch,
+			LinesAdded:    file.Additions,
+			LinesDeleted:  file.Deletions,
+			LinesModified: linesModified,
+		})
+	}
+
+	return changedFiles
+}