feat: initial github-to-signal webhook server

HTTP server that receives GitHub webhook events and sends formatted
notifications to Signal via signal-cli's JSON-RPC API.

Supported events: push, issues, issue comments, pull requests,
PR reviews, PR review comments, releases, stars, forks, workflow
runs, branch/tag creation, branch/tag deletion.

Uses cbrgm/githubevents for webhook handling and taigrr/signalcli
for Signal delivery. Config via TOML file or GH2SIG_ env vars
(powered by taigrr/jety).

main.go

@@ -0,0 +1,149 @@
+// github-to-signal is an HTTP server that receives GitHub webhook events
+// and forwards formatted notifications to Signal via signal-cli's JSON-RPC API.
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/cbrgm/githubevents/v2/githubevents"
+	"github.com/google/go-github/v70/github"
+	"github.com/taigrr/signalcli"
+)
+
+func main() {
+	cfg := loadConfig()
+
+	if cfg.SignalAccount == "" {
+		log.Fatal("signal_account is required (set GH2SIG_SIGNAL_ACCOUNT or config.toml)")
+	}
+	if cfg.SignalRecipient == "" {
+		log.Fatal("signal_recipient is required (set GH2SIG_SIGNAL_RECIPIENT or config.toml)")
+	}
+
+	signal := signalcli.NewClient(cfg.SignalURL, cfg.SignalAccount)
+	handle := githubevents.New(cfg.WebhookSecret)
+
+	notifier := &notifier{
+		signal:    signal,
+		recipient: cfg.SignalRecipient,
+	}
+
+	// Register event handlers.
+	handle.OnPushEventAny(notifier.onPush)
+	handle.OnIssuesEventAny(notifier.onIssue)
+	handle.OnIssueCommentEventAny(notifier.onIssueComment)
+	handle.OnPullRequestEventAny(notifier.onPR)
+	handle.OnPullRequestReviewEventAny(notifier.onPRReview)
+	handle.OnPullRequestReviewCommentEventAny(notifier.onPRReviewComment)
+	handle.OnReleaseEventAny(notifier.onRelease)
+	handle.OnStarEventAny(notifier.onStar)
+	handle.OnForkEventAny(notifier.onFork)
+	handle.OnWorkflowRunEventAny(notifier.onWorkflowRun)
+	handle.OnCreateEventAny(notifier.onCreate)
+	handle.OnDeleteEventAny(notifier.onDelete)
+
+	handle.OnError(func(_ context.Context, _ string, _ string, _ interface{}, err error) error {
+		log.Printf("webhook error: %v", err)
+		return nil
+	})
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /webhook", func(w http.ResponseWriter, r *http.Request) {
+		if err := handle.HandleEventRequest(r); err != nil {
+			log.Printf("handle event: %v", err)
+			http.Error(w, "webhook processing failed", http.StatusInternalServerError)
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+	})
+	mux.HandleFunc("GET /health", func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		fmt.Fprintln(w, "ok")
+	})
+
+	log.Printf("listening on %s", cfg.ListenAddr)
+	if err := http.ListenAndServe(cfg.ListenAddr, mux); err != nil {
+		log.Fatal(err)
+	}
+}
+
+type notifier struct {
+	signal    *signalcli.Client
+	recipient string
+}
+
+func (n *notifier) send(ctx context.Context, msg string) {
+	if msg == "" {
+		return
+	}
+	_, err := n.signal.Send(ctx, signalcli.SendParams{
+		Recipient: n.recipient,
+		Message:   msg,
+	})
+	if err != nil {
+		log.Printf("signal send error: %v", err)
+	}
+}
+
+func (n *notifier) onPush(ctx context.Context, _ string, _ string, event *github.PushEvent) error {
+	n.send(ctx, formatPush(event))
+	return nil
+}
+
+func (n *notifier) onIssue(ctx context.Context, _ string, _ string, event *github.IssuesEvent) error {
+	n.send(ctx, formatIssue(event))
+	return nil
+}
+
+func (n *notifier) onIssueComment(ctx context.Context, _ string, _ string, event *github.IssueCommentEvent) error {
+	n.send(ctx, formatIssueComment(event))
+	return nil
+}
+
+func (n *notifier) onPR(ctx context.Context, _ string, _ string, event *github.PullRequestEvent) error {
+	n.send(ctx, formatPR(event))
+	return nil
+}
+
+func (n *notifier) onPRReview(ctx context.Context, _ string, _ string, event *github.PullRequestReviewEvent) error {
+	n.send(ctx, formatPRReview(event))
+	return nil
+}
+
+func (n *notifier) onPRReviewComment(ctx context.Context, _ string, _ string, event *github.PullRequestReviewCommentEvent) error {
+	n.send(ctx, formatPRReviewComment(event))
+	return nil
+}
+
+func (n *notifier) onRelease(ctx context.Context, _ string, _ string, event *github.ReleaseEvent) error {
+	n.send(ctx, formatRelease(event))
+	return nil
+}
+
+func (n *notifier) onStar(ctx context.Context, _ string, _ string, event *github.StarEvent) error {
+	n.send(ctx, formatStar(event))
+	return nil
+}
+
+func (n *notifier) onFork(ctx context.Context, _ string, _ string, event *github.ForkEvent) error {
+	n.send(ctx, formatFork(event))
+	return nil
+}
+
+func (n *notifier) onWorkflowRun(ctx context.Context, _ string, _ string, event *github.WorkflowRunEvent) error {
+	n.send(ctx, formatWorkflowRun(event))
+	return nil
+}
+
+func (n *notifier) onCreate(ctx context.Context, _ string, _ string, event *github.CreateEvent) error {
+	n.send(ctx, formatCreate(event))
+	return nil
+}
+
+func (n *notifier) onDelete(ctx context.Context, _ string, _ string, event *github.DeleteEvent) error {
+	n.send(ctx, formatDelete(event))
+	return nil
+}