latexgrambot: inline LaTeX bot for Telegram in Go
Renders LaTeX expressions into PNG pictures, PDF documents and native Telegram rich text messages, entirely locally with TeX Live and poppler. - Chat mode with /image, /pdf, /rich plus per-user preamble and DPI - Inline mode delivering picture, PDF and rich text results - Broad default package set preloaded into a TeX format at image build - MongoDB persistence: settings, users, groups, render statistics - Private S3-compatible bucket with short-lived presigned URLs - OpenTelemetry traces over OTLP - Kubernetes manifests and Argo CD application, Docker Compose, GitHub Actions CI, BSD 3-Clause license
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corrado.mulas
177
cmd/latexgrambot/main.go
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177
cmd/latexgrambot/main.go
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// latexgrambot renders LaTeX expressions into PNG, PDF and Telegram rich
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// messages, entirely locally (TeX Live + poppler, no external services).
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package main
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"log"
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"net/http"
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"os"
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"os/signal"
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"syscall"
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"time"
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"latexgrambot/internal/bot"
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"latexgrambot/internal/config"
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"latexgrambot/internal/files"
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"latexgrambot/internal/render"
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"latexgrambot/internal/store"
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"latexgrambot/internal/telemetry"
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"go.mongodb.org/mongo-driver/mongo"
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"go.mongodb.org/mongo-driver/mongo/options"
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"go.opentelemetry.io/contrib/instrumentation/go.mongodb.org/mongo-driver/mongo/otelmongo"
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"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
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)
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func main() {
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// Used at image build time to generate the preamble that preloads the
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// default packages into the "latexgrambot" TeX format.
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if len(os.Args) > 1 && os.Args[1] == "-print-preamble" {
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fmt.Print(render.DefaultPreamble())
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return
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}
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cfg, err := config.Load()
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if err != nil {
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log.Fatalf("configuration error: %v", err)
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}
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ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
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defer stop()
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shutdown, err := telemetry.Setup(ctx)
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if err != nil {
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log.Fatalf("telemetry: %v", err)
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}
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defer func() {
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shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
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defer cancel()
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if err := shutdown(shutdownCtx); err != nil {
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log.Printf("telemetry shutdown: %v", err)
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}
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}()
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mongoClient, err := mongo.Connect(ctx,
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options.Client().ApplyURI(cfg.MongoURI).SetMonitor(otelmongo.NewMonitor()),
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)
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if err != nil {
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log.Fatalf("mongo connect: %v", err)
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}
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defer mongoClient.Disconnect(context.Background())
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storage := store.New(mongoClient, cfg.MongoDatabase)
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pingCtx, pingCancel := context.WithTimeout(ctx, 10*time.Second)
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err = storage.Ping(pingCtx)
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pingCancel()
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if err != nil {
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log.Fatalf("MongoDB not reachable: %v", err)
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}
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if err := storage.EnsureIndexes(ctx); err != nil {
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log.Fatalf("ensure indexes: %v", err)
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}
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renderer := render.New(cfg.PdflatexBin, cfg.PdftoppmBin, cfg.RenderTimeout, cfg.MaxConcurrency, "")
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renderer.Format = cfg.LatexFormat
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var fileStore *files.Store
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if cfg.S3Enabled() {
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s3Store, storeErr := files.New(ctx, files.Config{
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Endpoint: cfg.S3Endpoint,
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Region: cfg.S3Region,
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Bucket: cfg.S3Bucket,
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AccessKeyID: cfg.S3AccessKeyID,
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SecretAccessKey: cfg.S3SecretAccessKey,
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Prefix: cfg.S3Prefix,
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PublicEndpoint: cfg.S3PublicEndpoint,
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PresignTTL: cfg.S3PresignTTL,
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})
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if storeErr != nil {
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log.Fatalf("files store: %v", storeErr)
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}
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fileStore = s3Store
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log.Printf("inline files use private bucket %s with %s presigned URLs", cfg.S3Bucket, cfg.S3PresignTTL)
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// Garbage collect inline assets once their presigned links have
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// certainly expired: Telegram downloads them at pick time, and the
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// signed URLs are dead after the presign TTL anyway.
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assetAge := 2 * cfg.S3PresignTTL
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if assetAge < time.Hour {
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assetAge = time.Hour
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}
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go func() {
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ticker := time.NewTicker(15 * time.Minute)
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defer ticker.Stop()
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for {
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select {
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case <-ctx.Done():
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return
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case <-ticker.C:
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sweepCtx, cancel := context.WithTimeout(ctx, time.Minute)
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removed, sweepErr := fileStore.DeleteExpired(sweepCtx, assetAge)
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cancel()
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if sweepErr != nil {
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log.Printf("asset sweep: %v", sweepErr)
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} else if removed > 0 {
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log.Printf("asset sweep: removed %d expired objects", removed)
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}
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}
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}
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}()
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} else {
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log.Println("S3 not configured: inline PNG/PDF results disabled")
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}
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b, err := bot.New(cfg, renderer, storage, storage, storage, fileStore)
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if err != nil {
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log.Fatal(err)
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}
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mux := http.NewServeMux()
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mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
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writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
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})
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mux.HandleFunc("/readyz", func(w http.ResponseWriter, request *http.Request) {
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checkCtx, cancel := context.WithTimeout(request.Context(), 3*time.Second)
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defer cancel()
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if err := storage.Ping(checkCtx); err != nil {
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writeJSON(w, http.StatusServiceUnavailable, map[string]string{"status": "degraded", "dependency": "mongodb"})
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return
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}
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if err := b.Healthy(); err != nil {
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writeJSON(w, http.StatusServiceUnavailable, map[string]string{"status": "degraded", "error": err.Error()})
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return
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}
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writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
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})
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srv := &http.Server{
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Addr: cfg.HealthAddr,
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Handler: otelhttp.NewHandler(mux, "latexgrambot-http"),
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ReadHeaderTimeout: 10 * time.Second,
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}
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go func() {
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if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
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log.Fatalf("http server: %v", err)
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}
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}()
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log.Printf("latexgrambot started: dpi=%d timeout=%s concurrency=%d mongo=%s",
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cfg.RenderDPI, cfg.RenderTimeout, cfg.MaxConcurrency, cfg.MongoDatabase)
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runErr := b.Run(ctx)
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shutdownCtx, cancelShutdown := context.WithTimeout(context.Background(), 5*time.Second)
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defer cancelShutdown()
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_ = srv.Shutdown(shutdownCtx)
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if runErr != nil {
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log.Fatal(runErr)
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}
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log.Println("latexgrambot stopped")
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}
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func writeJSON(w http.ResponseWriter, status int, value interface{}) {
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w.Header().Set("Content-Type", "application/json")
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w.WriteHeader(status)
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_ = json.NewEncoder(w).Encode(value)
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}
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