// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

//go:build !ios && !android

package ipnlocal

import (
	"errors"
	"fmt"
	"net"
	"net/http"

	"tailscale.com/client/tailscale"
	"tailscale.com/client/web"
	"tailscale.com/net/netutil"
)

// webClient holds state for the web interface for managing
// this tailscale instance. The web interface is not used by
// default, but initialized by calling LocalBackend.WebOrInit.
type webClient struct {
	server *web.Server // or nil, initialized lazily

	// lc optionally specifies a LocalClient to use to connect
	// to the localapi for this tailscaled instance.
	// If nil, a default is used.
	lc *tailscale.LocalClient
}

// SetWebLocalClient sets the b.web.lc function.
// If lc is provided as nil, b.web.lc is cleared out.
func (b *LocalBackend) SetWebLocalClient(lc *tailscale.LocalClient) {
	b.mu.Lock()
	defer b.mu.Unlock()
	b.webClient.lc = lc
}

// WebClientInit initializes the web interface for managing this
// tailscaled instance.
// If the web interface is already running, WebClientInit is a no-op.
func (b *LocalBackend) WebClientInit() (err error) {
	if !b.ShouldRunWebClient() {
		return errors.New("web client not enabled for this device")
	}

	b.mu.Lock()
	defer b.mu.Unlock()
	if b.webClient.server != nil {
		return nil
	}

	b.logf("WebClientInit: initializing web ui")
	if b.webClient.server, err = web.NewServer(web.ServerOpts{
		Mode:        web.ManageServerMode,
		LocalClient: b.webClient.lc,
		Logf:        b.logf,
	}); err != nil {
		return fmt.Errorf("web.NewServer: %w", err)
	}

	b.logf("WebClientInit: started web ui")
	return nil
}

// WebClientShutdown shuts down any running b.webClient servers and
// clears out b.webClient state (besides the b.webClient.lc field,
// which is left untouched because required for future web startups).
// WebClientShutdown obtains the b.mu lock.
func (b *LocalBackend) WebClientShutdown() {
	b.mu.Lock()
	server := b.webClient.server
	b.webClient.server = nil
	b.mu.Unlock() // release lock before shutdown
	if server != nil {
		server.Shutdown()
		b.logf("WebClientShutdown: shut down web ui")
	}
}

// handleWebClientConn serves web client requests.
func (b *LocalBackend) handleWebClientConn(c net.Conn) error {
	if err := b.WebClientInit(); err != nil {
		return err
	}
	s := http.Server{Handler: b.webClient.server}
	return s.Serve(netutil.NewOneConnListener(c, nil))
}