browser_mcp/main.go

package main

import (
	"flag"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"os/signal"
	"strings"
	"syscall"

	"github.com/mark3labs/mcp-go/server"

	"fn-registry/functions/browser"
)

// version is the server version reported in serverInfo. The literal here is a
// fallback for `go build` with no flags; build.sh overrides it via
// -ldflags "-X main.version=<app.md version>" so app.md stays the single source
// of truth and the binary can never drift behind it (see build.sh).
var version = "0.8.0"

type config struct {
	httpAddr string
	bind     string
	readOnly bool
	logLevel string
}

// deps carries shared state into tool handlers.
type deps struct {
	pool     *connPool
	readOnly bool
}

func main() {
	var cfg config
	flag.StringVar(&cfg.httpAddr, "http", "", "Listen on HTTP address (e.g. :7740). Empty = stdio.")
	flag.StringVar(&cfg.bind, "bind", "127.0.0.1", "HTTP bind address. Use 0.0.0.0 only with REGISTRY_API_TOKEN set.")
	flag.BoolVar(&cfg.readOnly, "read-only", false, "Register only read tools (no mutating browser actions).")
	flag.StringVar(&cfg.logLevel, "log-level", "info", "Log level: debug, info, warn, error.")
	flag.Parse()

	// Slog → stderr (stdio JSON-RPC owns stdout).
	lvl := parseLevel(cfg.logLevel)
	slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: lvl})))

	pool := newConnPool()
	// Cierre por EOF de stdio (ServeStdio retorna) o salida normal de serveHTTP.
	defer pool.closeAll()

	// Cierre por señal: SIGTERM/SIGINT NO ejecutan defers, así que matamos los
	// Chrome propios explícitamente antes de salir. Sin esto, al matar el MCP los
	// chromium lanzados quedaban vivos y huérfanos (~789 MiB RSS cada uno) — el
	// leak que provocó el apagón por saturación de RAM (06/06/2026).
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
	go func() {
		sig := <-sigCh
		slog.Info("signal received, killing launched chromes", "signal", sig.String())
		pool.closeAll()
		os.Exit(0)
	}()

	d := &deps{pool: pool, readOnly: cfg.readOnly}

	srv := server.NewMCPServer(
		"browser_mcp",
		version,
		server.WithToolCapabilities(true),
	)

	registerTools(srv, d)

	slog.Info("starting browser_mcp",
		"version", version,
		"transport", transportLabel(cfg),
		"read_only", cfg.readOnly,
	)

	if cfg.httpAddr == "" {
		if err := server.ServeStdio(srv); err != nil {
			slog.Error("stdio server", "err", err)
			os.Exit(1)
		}
		return
	}

	if err := serveHTTP(srv, cfg); err != nil {
		slog.Error("http server", "err", err)
		os.Exit(1)
	}
}

// registerTools wires every tool group. Mutating tools are skipped under --read-only.
func registerTools(s *server.MCPServer, d *deps) {
	registerSessionTools(s, d)
	registerLifecycleTools(s, d)
	registerNavTools(s, d)
	registerReadTools(s, d)
	registerDomTools(s, d)
	registerInputTools(s, d)
	registerCookieTools(s, d)
	registerFrameTools(s, d)
	registerStorageTools(s, d)
}

// portOr returns the CDP port, defaulting to 9333 when zero.
//
// SECURITY (P0.3): the default is 9333 — the MCP's OWN isolated Chrome — NOT
// 9222. Port 9222 is the user's daily chromium (CDP enabled globally via
// /etc/chromium.d/cdp). Defaulting there would let the agent drive the user's
// banking/email tabs. The MCP operates on its dedicated browser by default;
// pass port=9222 explicitly only to deliberately attach to the daily browser.
func portOr(p int) int {
	if p == 0 {
		return 9333
	}
	return p
}

// withConn obtiene la conexión del puerto y ejecuta fn. Si falla con error de
// conexión muerta, descarta y reintenta UNA vez (Chrome pudo cerrar la tab).
func (d *deps) withConn(port int, fn func(c *browser.CDPConn) error) error {
	c, err := d.pool.get(port)
	if err != nil {
		return err
	}
	err = fn(c)
	if err != nil && isConnErr(err) {
		// La conexión murió (Chrome pudo cerrar la tab). Soltamos SOLO el
		// WebSocket y reconectamos al mismo Chrome — releaseConn, no drop: drop
		// mataría el proceso y dejaría sin nada a qué reconectar.
		d.pool.releaseConn(port)
		c2, err2 := d.pool.get(port)
		if err2 != nil {
			return err2
		}
		return fn(c2)
	}
	return err
}

// serveHTTP hosts the MCP server over Streamable HTTP with optional bearer auth.
func serveHTTP(s *server.MCPServer, cfg config) error {
	addr := cfg.bind + cfg.httpAddr

	httpSrv := server.NewStreamableHTTPServer(s)

	token := os.Getenv("REGISTRY_API_TOKEN")
	if cfg.bind == "0.0.0.0" && token == "" {
		return fmt.Errorf("--bind 0.0.0.0 requires REGISTRY_API_TOKEN")
	}

	mux := http.NewServeMux()
	if token != "" {
		mux.Handle("/", authMiddleware(token, httpSrv))
	} else {
		mux.Handle("/", httpSrv)
	}

	slog.Info("listening http", "addr", addr)
	return http.ListenAndServe(addr, mux)
}

func authMiddleware(token string, next http.Handler) http.Handler {
	expected := "Bearer " + token
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get("Authorization") != expected {
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func transportLabel(cfg config) string {
	if cfg.httpAddr == "" {
		return "stdio"
	}
	return fmt.Sprintf("http %s%s", cfg.bind, cfg.httpAddr)
}

func parseLevel(s string) slog.Level {
	switch strings.ToLower(s) {
	case "debug":
		return slog.LevelDebug
	case "warn":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}

// truncate caps a string at n chars, appending a marker when cut.
func truncate(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "\n... [truncated]"
}