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
This commit is contained in:
corrado.mulas
192
internal/config/config.go
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192
internal/config/config.go
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// Package config reads the latexgrambot configuration from environment variables.
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package config
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import (
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"fmt"
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"os"
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"strconv"
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"strings"
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"time"
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)
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// Config holds every runtime setting.
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type Config struct {
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TelegramBotToken string
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// MongoURI is the shared cluster connection string. MongoDatabase is
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// the bot's database inside it.
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MongoURI string
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MongoDatabase string
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// S3 hosts rendered inline files. All required values must be set
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// together; otherwise inline mode offers only native rich text.
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S3Endpoint string
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S3Region string
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S3Bucket string
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S3AccessKeyID string
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S3SecretAccessKey string
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S3Prefix string
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S3PublicEndpoint string
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S3PresignTTL time.Duration
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HealthAddr string
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// RichTextEnabled controls the rich-message replies (native math block).
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// The format needs a recent Bot API server; when disabled the bot falls
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// back to PNG and PDF only.
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RichTextEnabled bool
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// RichDefaultMath controls how the rich format treats a bare source
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// (no math delimiters, no text-mode command): true renders it as a math
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// expression, false parses it as text so formulas need $...$ delimiters.
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RichDefaultMath bool
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RenderDPI int
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RenderTimeout time.Duration
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MaxConcurrency int
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// MaxExpressionLen caps chat-mode expressions. MaxPreambleLen caps the
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// per-user preamble (Telegram messages are at most 4096 characters).
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MaxExpressionLen int
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MaxPreambleLen int
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PdflatexBin string
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PdftoppmBin string
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// LatexFormat is the preloaded TeX format name (built from the default
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// preamble at image build time). Empty disables it.
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LatexFormat string
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}
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// Load builds the Config and validates the mandatory keys.
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func Load() (*Config, error) {
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cfg := &Config{
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TelegramBotToken: strings.TrimSpace(os.Getenv("TELEGRAM_BOT_TOKEN")),
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MongoURI: strings.TrimSpace(os.Getenv("MONGODB_URI")),
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MongoDatabase: getenv("MONGODB_DATABASE", "latexgram"),
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S3Endpoint: strings.TrimRight(strings.TrimSpace(os.Getenv("S3_ENDPOINT_URL")), "/"),
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S3Region: getenv("S3_REGION", "us-east-1"),
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S3Bucket: strings.TrimSpace(os.Getenv("S3_BUCKET")),
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S3AccessKeyID: strings.TrimSpace(os.Getenv("AWS_ACCESS_KEY_ID")),
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S3SecretAccessKey: strings.TrimSpace(os.Getenv("AWS_SECRET_ACCESS_KEY")),
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S3Prefix: strings.Trim(getenv("S3_PREFIX", "content"), "/"),
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S3PublicEndpoint: strings.TrimRight(strings.TrimSpace(os.Getenv("S3_PUBLIC_ENDPOINT_URL")), "/"),
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HealthAddr: getenv("HEALTH_ADDR", ":8080"),
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PdflatexBin: getenv("PDFLATEX_BIN", "pdflatex"),
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PdftoppmBin: getenv("PDFTOPPM_BIN", "pdftoppm"),
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LatexFormat: getenv("LATEX_FORMAT", ""),
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}
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var err error
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if cfg.RichTextEnabled, err = getenvBool("RICH_TEXT_ENABLED", true); err != nil {
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return nil, err
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}
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if cfg.RichDefaultMath, err = getenvBool("RICH_DEFAULT_MATH", true); err != nil {
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return nil, err
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}
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if cfg.RenderDPI, err = getenvInt("RENDER_DPI", 600); err != nil {
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return nil, err
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}
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if cfg.MaxConcurrency, err = getenvInt("RENDER_MAX_CONCURRENCY", 2); err != nil {
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return nil, err
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}
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if cfg.MaxExpressionLen, err = getenvInt("MAX_EXPRESSION_LEN", 4000); err != nil {
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return nil, err
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}
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if cfg.MaxPreambleLen, err = getenvInt("MAX_PREAMBLE_LEN", 4000); err != nil {
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return nil, err
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}
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if cfg.RenderTimeout, err = getenvDuration("RENDER_TIMEOUT", 30*time.Second); err != nil {
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return nil, err
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}
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if cfg.S3PresignTTL, err = getenvDuration("S3_PRESIGN_TTL", time.Hour); err != nil {
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return nil, err
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}
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if cfg.TelegramBotToken == "" {
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return nil, fmt.Errorf("missing required environment variable: TELEGRAM_BOT_TOKEN")
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}
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if cfg.MongoURI == "" {
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return nil, fmt.Errorf("missing required environment variable: MONGODB_URI")
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}
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if cfg.RenderDPI < 72 || cfg.RenderDPI > 1200 {
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return nil, fmt.Errorf("RENDER_DPI must be between 72 and 1200")
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}
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if cfg.RenderTimeout <= 0 {
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return nil, fmt.Errorf("RENDER_TIMEOUT must be positive")
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}
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if cfg.MaxConcurrency < 1 {
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return nil, fmt.Errorf("RENDER_MAX_CONCURRENCY must be at least 1")
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}
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if cfg.MaxExpressionLen < 1 || cfg.MaxPreambleLen < 1 {
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return nil, fmt.Errorf("MAX_EXPRESSION_LEN and MAX_PREAMBLE_LEN must be positive")
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}
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s3Set := 0
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for _, value := range []string{
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cfg.S3Endpoint, cfg.S3Bucket, cfg.S3AccessKeyID,
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cfg.S3SecretAccessKey, cfg.S3PublicEndpoint,
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} {
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if value != "" {
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s3Set++
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}
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}
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if s3Set != 0 && s3Set != 5 {
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return nil, fmt.Errorf(
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"incomplete S3 configuration: set S3_ENDPOINT_URL, S3_BUCKET, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY and S3_PUBLIC_ENDPOINT_URL together")
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}
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if cfg.S3PresignTTL <= 0 {
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return nil, fmt.Errorf("S3_PRESIGN_TTL must be positive")
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}
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return cfg, nil
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}
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// S3Enabled reports whether private inline PNG/PDF assets can be stored and
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// exposed through short-lived presigned URLs.
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func (c *Config) S3Enabled() bool {
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return c.S3Endpoint != "" && c.S3Bucket != "" &&
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c.S3AccessKeyID != "" && c.S3SecretAccessKey != "" &&
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c.S3PublicEndpoint != ""
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}
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func getenv(key, fallback string) string {
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if value := strings.TrimSpace(os.Getenv(key)); value != "" {
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return value
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}
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return fallback
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}
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func getenvInt(key string, fallback int) (int, error) {
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value := strings.TrimSpace(os.Getenv(key))
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if value == "" {
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return fallback, nil
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}
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parsed, err := strconv.Atoi(value)
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if err != nil {
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return 0, fmt.Errorf("invalid %s: %w", key, err)
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}
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return parsed, nil
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}
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func getenvBool(key string, fallback bool) (bool, error) {
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value := strings.TrimSpace(os.Getenv(key))
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if value == "" {
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return fallback, nil
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}
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parsed, err := strconv.ParseBool(value)
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if err != nil {
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return false, fmt.Errorf("invalid %s: %w", key, err)
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}
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return parsed, nil
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}
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func getenvDuration(key string, fallback time.Duration) (time.Duration, error) {
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value := strings.TrimSpace(os.Getenv(key))
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if value == "" {
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return fallback, nil
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}
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parsed, err := time.ParseDuration(value)
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if err != nil {
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return 0, fmt.Errorf("invalid %s: %w", key, err)
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}
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return parsed, nil
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}
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