depot/web/fup/cmd/serve.go

// SPDX-FileCopyrightText: 2021 Luke Granger-Brown <depot@lukegb.com>
//
// SPDX-License-Identifier: Apache-2.0

package cmd

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"os/exec"
	"strings"

	"github.com/coreos/go-systemd/v22/activation"
	"github.com/google/safehtml"
	"github.com/spf13/cobra"
	"github.com/spf13/viper"
	"hg.lukegb.com/lukegb/depot/web/fup/fuphttp"
	"hg.lukegb.com/lukegb/depot/web/fup/fupstatic"
	"hg.lukegb.com/lukegb/depot/web/fup/minicheddar"
)

func init() {
	rootCmd.AddCommand(serveCmd)

	serveCmd.Flags().String("root", "http://localhost:8191/", "Application root address.")
	viper.BindPFlag("serve.app-root", serveCmd.Flags().Lookup("root"))
	viper.SetDefault("serve.app-root", "http://localhost:8191/")

	serveCmd.Flags().String("static-root", "/static/", "Root address from which static assets should be referenced.")
	viper.BindPFlag("serve.static-root", serveCmd.Flags().Lookup("static-root"))
	viper.SetDefault("serve.static-root", "/static/")

	serveCmd.Flags().StringP("listen", "l", ":8191", "Bind address for HTTP server.")
	viper.BindPFlag("serve.listen", serveCmd.Flags().Lookup("listen"))
	viper.SetDefault("serve.listen", ":8191")

	serveCmd.Flags().Bool("direct-only", false, "If set, all file serving will be proxied, even if the backend supports signed URLs.")
	viper.BindPFlag("serve.direct-only", serveCmd.Flags().Lookup("direct-only"))
	viper.SetDefault("serve.direct-only", false)

	serveCmd.Flags().String("cheddar-path", "cheddar", "Path to 'cheddar' binary to use for syntax highlighting. If it cannot be found, syntax highlighting and markdown rendering will be disabled.")
	viper.BindPFlag("serve.cheddar.path", serveCmd.Flags().Lookup("cheddar-path"))
	viper.SetDefault("serve.cheddar.path", "cheddar")

	serveCmd.Flags().String("cheddar-address", "", "If non-empty, will be used instead of attempting to spawn a copy of cheddar.")
	viper.BindPFlag("serve.cheddar.address", serveCmd.Flags().Lookup("cheddar-address"))

	serveCmd.Flags().String("auth-token", "", "If non-empty, this auth token will be required as the Basic Auth password.")
	viper.BindPFlag("serve.auth.token", serveCmd.Flags().Lookup("auth-token"))
	serveCmd.Flags().String("auth-realm", "fup", "Will be used as the realm for Basic Auth.")
	viper.BindPFlag("serve.auth.realm", serveCmd.Flags().Lookup("auth-realm"))
	viper.SetDefault("serve.auth.realm", "fup")
}

var (
	serveCmd = &cobra.Command{
		Use:   "serve",
		Short: "Serve HTTP",
		RunE: func(cmd *cobra.Command, args []string) error {
			if !strings.HasSuffix(viper.GetString("serve.app-root"), "/") {
				return fmt.Errorf("--root flag (serve.app-root) should end in / (value is %q)", viper.GetString("serve.app-root"))
			}
			if !strings.HasSuffix(viper.GetString("serve.static-root"), "/") {
				return fmt.Errorf("--static-root flag (serve.static-root) should end in / (value is %q)", viper.GetString("serve.static-root"))
			}

			ctx := context.Background()
			highlighter, err := serveCheddar(ctx)
			if err != nil {
				return fmt.Errorf("spawning cheddar syntax highlighter: %v", err)
			}

			cfg := &fuphttp.Config{
				Templates:           fupstatic.Templates,
				Static:              fupstatic.Static,
				StaticRoot:          safehtml.TrustedResourceURLFromFlag(cmd.Flag("static-root").Value),
				AppRoot:             viper.GetString("serve.app-root"),
				StorageURL:          bucketURL(),
				RedirectToBlobstore: !viper.GetBool("serve.direct-only"),
				AuthMiddleware:      fuphttp.TokenAuthMiddleware(viper.GetString("serve.auth.token"), viper.GetString("serve.auth.realm")),
			}
			if highlighter != nil {
				cfg.Highlighter = highlighter
			}
			a, err := fuphttp.New(ctx, cfg)
			if err != nil {
				return fmt.Errorf("constructing application: %w", err)
			}
			http.Handle("/", a.Handler())
			http.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.FS(fupstatic.Static))))
			log.Printf("Serving on %s", viper.GetString("serve.listen"))
			if viper.GetString("serve.listen") == "systemd" {
				listeners, err := activation.Listeners()
				if err != nil {
					return fmt.Errorf("getting systemd socket-activated listeners: %v", err)
				}
				if len(listeners) != 1 {
					return fmt.Errorf("unexpected systemd socket activation fds: got %d; want 1", len(listeners))
				}
				return http.Serve(listeners[0], nil)
			}
			return http.ListenAndServe(viper.GetString("serve.listen"), nil)
		},
	}
)

func serveCheddar(ctx context.Context) (*minicheddar.Cheddar, error) {
	if serveCheddarAddr := viper.GetString("serve.cheddar.addr"); serveCheddarAddr != "" {
		return minicheddar.Remote(serveCheddarAddr), nil
	}

	cpath, err := exec.LookPath(viper.GetString("serve.cheddar.path"))
	if err != nil {
		log.Printf("couldn't find cheddar at %q; disabling syntax highlighting", viper.GetString("serve.cheddar.path"))
		return nil, nil
	}

	return minicheddar.Spawn(ctx, cpath)
}