// Package webgui implements the "rclone webgui" command — an in-process
// web GUI for rclone with the Anthropic design system. It mirrors the
// architecture of cmd/gui/gui.go (two in-process HTTP servers: a static
// GUI server and an RC API server, with the browser opened automatically),
// but serves our own embedded vanilla HTML/CSS/JS frontend instead of
// the upstream React bundle.
package webgui

import (
	"context"
	_ "embed"
	"fmt"
	iofs "io/fs"
	"net/http"
	"net/url"
	"os"
	"strings"
	"sync"

	"github.com/go-chi/chi/v5/middleware"
	"github.com/rclone/rclone/cmd"
	"github.com/rclone/rclone/fs"
	"github.com/rclone/rclone/fs/rc"
	"github.com/rclone/rclone/fs/rc/rcserver"
	libhttp "github.com/rclone/rclone/lib/http"
	"github.com/rclone/rclone/lib/random"
	"github.com/rclone/rclone/lib/systemd"
	"github.com/skratchdot/open-golang/open"
	"github.com/spf13/cobra"
)

//go:embed web
var embedFS iofs.FS

var (
	guiAddr       []string
	apiAddr       []string
	user          string
	pass          string
	noAuth        bool
	noOpenBrowser bool
	enableMetrics bool
)

func init() {
	cmd.Root.AddCommand(commandDefinition)
	f := commandDefinition.Flags()
	f.StringArrayVar(&guiAddr, "addr", nil, "IPaddress:Port for the GUI server (default auto-chosen localhost port)")
	f.StringArrayVar(&apiAddr, "api-addr", nil, "IPaddress:Port for the RC API server (default auto-chosen localhost port)")
	f.StringVar(&user, "user", "", "User name for RC authentication")
	f.StringVar(&pass, "pass", "", "Password for RC authentication")
	f.BoolVar(&noAuth, "no-auth", false, "Don't require auth for the RC API")
	f.BoolVar(&noOpenBrowser, "no-open-browser", false, "Skip opening the browser automatically")
	f.BoolVar(&enableMetrics, "enable-metrics", false, "Enable OpenMetrics/Prometheus compatible endpoint at /metrics")
}

var commandDefinition = &cobra.Command{
	Use:   "webgui [path]",
	Short: `Open the web based GUI.`,
	Long: `This command starts an embedded web GUI for rclone and opens it in
your default browser.

Two localhost ports are bound: one serves the static GUI, the other is
the rclone RC API server that the GUI talks to. Credentials are
generated automatically unless --no-auth is specified.

    rclone webgui

By default ` + "`rclone webgui`" + ` serves the GUI embedded into the rclone
binary at build time. You can override this by passing a path to an
unpacked GUI directory, which is useful for iterating on the frontend
without rebuilding rclone:

    rclone webgui ./cmd/webgui/web

Use --no-open-browser to skip opening the browser automatically:

    rclone webgui --no-open-browser

Use --addr to bind the GUI to a specific address:

    rclone webgui --addr localhost:5580

Use --user and --pass to set specific credentials:

    rclone webgui --user admin --pass secret

Use --no-auth to disable authentication entirely (localhost only):

    rclone webgui --no-auth

Note: --no-auth enables the RC API's --rc-serve mode, which exposes an
HTTP fileserver on every configured remote. Only run this on a trusted
network.
`,
	Annotations: map[string]string{
		"versionIntroduced": "v1.75",
		"groups":            "RC",
	},
	RunE: func(command *cobra.Command, args []string) error {
		cmd.CheckArgs(0, 1, command, args)
		ctx := context.Background()

		// Resolve the GUI source (embedded subtree or local directory)
		// before binding any sockets so errors surface immediately.
		var srcPath string
		if len(args) == 1 {
			srcPath = args[0]
		}
		srcFS, err := guiSourceFS(srcPath)
		if err != nil {
			return err
		}

		// Create the GUI server (binds port eagerly, before Serve)
		guiCfg := libhttp.DefaultCfg()
		if command.Flags().Changed("addr") {
			guiCfg.ListenAddr = guiAddr
		} else {
			guiCfg.ListenAddr = []string{"localhost:0"}
		}
		guiServer, err := libhttp.NewServer(ctx, libhttp.WithConfig(guiCfg))
		if err != nil {
			return fmt.Errorf("failed to create GUI server: %w", err)
		}

		// Read the GUI origin from the bound address (available before Serve).
		guiOrigin := originFromURL(guiServer.URLs()[0])

		// Configure the RC API server
		opt := rc.Opt // copy global defaults
		opt.Enabled = true
		opt.WebUI = false
		// opt.Serve = true exposes an HTTP fileserver on every configured
		// remote so the GUI can download files via GET /<remote>:<path>.
		opt.Serve = true

		if command.Flags().Changed("api-addr") {
			opt.HTTP.ListenAddr = apiAddr
		} else {
			opt.HTTP.ListenAddr = []string{"localhost:0"}
		}

		// CORS: allow the GUI origin to make cross-port API requests.
		opt.HTTP.AllowOrigin = guiOrigin

		// Forward metrics flag to the RC server.
		if command.Flags().Changed("enable-metrics") {
			opt.EnableMetrics = enableMetrics
		}

		// Auth
		if command.Flags().Changed("user") {
			opt.Auth.BasicUser = user
		}
		if command.Flags().Changed("pass") {
			opt.Auth.BasicPass = pass
		}
		if command.Flags().Changed("no-auth") {
			opt.NoAuth = noAuth
		}

		if !opt.NoAuth {
			if opt.Auth.BasicUser == "" {
				opt.Auth.BasicUser = "gui"
				fs.Infof(nil, "No username specified. Using default username: %s", opt.Auth.BasicUser)
			}
			if opt.Auth.BasicPass == "" {
				randomPass, err := random.Password(128)
				if err != nil {
					return fmt.Errorf("failed to make password: %w", err)
				}
				opt.Auth.BasicPass = randomPass
				fs.Infof(nil, "No password specified. Using random password for this session")
			}
		}

		// Start the RC server
		rcServer, err := rcserver.Start(ctx, &opt)
		if err != nil || rcServer == nil {
			return fmt.Errorf("failed to start RC server: %w", err)
		}

		// Read the bound RC URL back from rcserver, in case we asked
		// libhttp to pick a free port (localhost:0).
		rcURL := rcServer.URLs()[0]

		// Mount the GUI handler and start serving
		spaHandler := guiHandler(srcFS)
		guiServer.Router().Use(middleware.Compress(5))
		guiServer.Router().Get("/*", spaHandler.ServeHTTP)
		guiServer.Router().Head("/*", spaHandler.ServeHTTP)
		guiServer.Serve()

		guiURL := guiServer.URLs()[0]
		guiSource := "embedded bundle"
		if srcPath != "" {
			guiSource = fmt.Sprintf("from %s", srcPath)
		}
		fs.Logf(nil, "Serving GUI %s on %s", guiSource, guiURL)

		// Build the launch URL: always pass ?url=<rcURL> so the SPA can
		// discover the RC base.
		loginURL := buildLoginURL(guiURL, rcURL, opt.Auth.BasicUser, opt.Auth.BasicPass, opt.NoAuth)

		fs.Logf(nil, "GUI available at %s", safeLoginURL(loginURL))
		if !opt.NoAuth {
			fs.Logf(nil, "GUI authentication user: %s", opt.Auth.BasicUser)
		}
		if !noOpenBrowser {
			if err := open.Start(loginURL); err != nil {
				fs.Errorf(nil, "failed to open GUI in browser: %v", err)
			}
		}

		// Wait for either server to exit, then shut both down and
		// join the second goroutine before returning.
		defer systemd.Notify()()
		var wg sync.WaitGroup
		done := make(chan struct{}, 2)
		wg.Add(2)
		go func() { defer wg.Done(); rcServer.Wait(); done <- struct{}{} }()
		go func() { defer wg.Done(); guiServer.Wait(); done <- struct{}{} }()
		<-done
		_ = rcServer.Shutdown()
		_ = guiServer.Shutdown()
		wg.Wait()
		return nil
	},
}

// originFromURL extracts the origin (scheme://host) from a URL string,
// stripping any path or trailing slash.
func originFromURL(rawURL string) string {
	u, err := url.Parse(rawURL)
	if err != nil {
		return strings.TrimRight(rawURL, "/")
	}
	return u.Scheme + "://" + u.Host
}

// guiSourceFS opens the GUI bundle at the given path. An empty path
// returns the embedded bundle (the `web/` directory compiled into the
// binary). A non-empty path must be an existing directory whose contents
// are served directly — useful for hot-reload during development.
func guiSourceFS(path string) (iofs.FS, error) {
	if path == "" {
		sub, err := iofs.Sub(embedFS, "web")
		if err != nil {
			return nil, fmt.Errorf("failed to read embedded GUI: %w", err)
		}
		if _, err := iofs.Stat(sub, "index.html"); err != nil {
			return nil, fmt.Errorf("embedded GUI has no index.html: %w", err)
		}
		return sub, nil
	}
	info, err := os.Stat(path)
	if err != nil {
		return nil, fmt.Errorf("failed to stat GUI source %q: %w", path, err)
	}
	if !info.IsDir() {
		return nil, fmt.Errorf("GUI source must be a directory: %q", path)
	}
	if _, err := os.Stat(path + "/index.html"); err != nil {
		return nil, fmt.Errorf("GUI source directory has no index.html: %w", err)
	}
	return os.DirFS(path), nil
}

// guiHandler returns an http.Handler that serves the GUI bundle from
// srcFS with SPA fallback: paths that don't match a real file return
// index.html so client-side hash routing keeps working.
func guiHandler(srcFS iofs.FS) http.Handler {
	fileServer := http.FileServer(http.FS(srcFS))
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		path := strings.TrimPrefix(r.URL.Path, "/")
		if path == "" {
			path = "index.html"
		}
		if _, err := iofs.Stat(srcFS, path); err == nil {
			fileServer.ServeHTTP(w, r)
			return
		}
		// SPA fallback: serve index.html for unknown paths so that
		// client-side routing (e.g. /login) works.
		r.URL.Path = "/"
		fileServer.ServeHTTP(w, r)
	})
}

// buildLoginURL constructs the URL the browser should open. The query
// string always carries the RC API base URL so the SPA can find it.
// When auth is enabled, user/pass and a /login hash are added so the SPA can
// present credentials to the cross-port RC server, then remove them from the
// visible address bar on load.
func buildLoginURL(guiBaseURL, rcURL, user, pass string, noAuth bool) string {
	u, err := url.Parse(guiBaseURL)
	if err != nil {
		return guiBaseURL
	}
	q := u.Query()
	q.Set("url", rcURL)
	if !noAuth {
		u.Path = "/login"
		q.Set("user", user)
		q.Set("pass", pass)
	}
	// Always land on the remotes view.
	if u.Fragment == "" {
		u.Fragment = "/remotes"
	}
	u.RawQuery = q.Encode()
	return u.String()
}

func safeLoginURL(loginURL string) string {
	u, err := url.Parse(loginURL)
	if err != nil {
		return loginURL
	}
	q := u.Query()
	q.Del("user")
	q.Del("pass")
	u.RawQuery = q.Encode()
	return u.String()
}