appservice.go

// Copyright (c) 2023 Tulir Asokan
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

package appservice

import (
	"context"
	"fmt"
	"net"
	"net/http"
	"net/http/cookiejar"
	"net/url"
	"os"
	"strings"
	"sync"
	"syscall"
	"time"

	"github.com/gorilla/mux"
	"github.com/gorilla/websocket"
	"github.com/rs/zerolog"
	"golang.org/x/net/publicsuffix"
	"gopkg.in/yaml.v3"

	"github.com/element-hq/mautrix-go"
	"github.com/element-hq/mautrix-go/event"
	"github.com/element-hq/mautrix-go/id"
)

// EventChannelSize is the size for the Events channel in Appservice instances.
var EventChannelSize = 64
var OTKChannelSize = 4

// Create creates a blank appservice instance.
func Create() *AppService {
	jar, _ := cookiejar.New(&cookiejar.Options{PublicSuffixList: publicsuffix.List})
	as := &AppService{
		Log:        zerolog.Nop(),
		clients:    make(map[id.UserID]*mautrix.Client),
		intents:    make(map[id.UserID]*IntentAPI),
		HTTPClient: &http.Client{Timeout: 180 * time.Second, Jar: jar},
		StateStore: mautrix.NewMemoryStateStore().(StateStore),
		Router:     mux.NewRouter(),
		UserAgent:  mautrix.DefaultUserAgent,
		txnIDC:     NewTransactionIDCache(128),
		Live:       true,
		Ready:      false,
		ProcessID:  getDefaultProcessID(),

		Events:         make(chan *event.Event, EventChannelSize),
		ToDeviceEvents: make(chan *event.Event, EventChannelSize),
		OTKCounts:      make(chan *mautrix.OTKCount, OTKChannelSize),
		DeviceLists:    make(chan *mautrix.DeviceLists, EventChannelSize),
		QueryHandler:   &QueryHandlerStub{},

		DefaultHTTPRetries: 4,
	}

	as.Router.HandleFunc("/_matrix/app/v1/transactions/{txnID}", as.PutTransaction).Methods(http.MethodPut)
	as.Router.HandleFunc("/_matrix/app/v1/rooms/{roomAlias}", as.GetRoom).Methods(http.MethodGet)
	as.Router.HandleFunc("/_matrix/app/v1/users/{userID}", as.GetUser).Methods(http.MethodGet)
	as.Router.HandleFunc("/_matrix/app/v1/ping", as.PostPing).Methods(http.MethodPost)
	as.Router.HandleFunc("/_matrix/mau/live", as.GetLive).Methods(http.MethodGet)
	as.Router.HandleFunc("/_matrix/mau/ready", as.GetReady).Methods(http.MethodGet)

	return as
}

// CreateOpts contains the options for initializing a new [AppService] instance.
type CreateOpts struct {
	// Required, the registration file data for this appservice.
	Registration *Registration
	// Required, the homeserver's server_name.
	HomeserverDomain string
	// Required, the homeserver URL to connect to. Should be either https://address or unix:path
	HomeserverURL string
	// Required if you want to use the standard HTTP server, optional for websockets (non-standard)
	HostConfig HostConfig
	// Optional, defaults to a memory state store
	StateStore StateStore
}

// CreateFull creates a fully configured appservice instance that can be [Start]ed and used directly.
func CreateFull(opts CreateOpts) (*AppService, error) {
	if opts.HomeserverDomain == "" {
		return nil, fmt.Errorf("missing homeserver domain")
	} else if opts.HomeserverURL == "" {
		return nil, fmt.Errorf("missing homeserver URL")
	} else if opts.Registration == nil {
		return nil, fmt.Errorf("missing registration")
	}
	as := Create()
	as.HomeserverDomain = opts.HomeserverDomain
	as.Host = opts.HostConfig
	as.Registration = opts.Registration
	err := as.SetHomeserverURL(opts.HomeserverURL)
	if err != nil {
		return nil, err
	}
	if opts.StateStore != nil {
		as.StateStore = opts.StateStore
	} else {
		as.StateStore = mautrix.NewMemoryStateStore().(StateStore)
	}
	return as, nil
}

var _ StateStore = (*mautrix.MemoryStateStore)(nil)

// QueryHandler handles room alias and user ID queries from the homeserver.
type QueryHandler interface {
	QueryAlias(alias string) bool
	QueryUser(userID id.UserID) bool
}

type QueryHandlerStub struct{}

func (qh *QueryHandlerStub) QueryAlias(alias string) bool {
	return false
}

func (qh *QueryHandlerStub) QueryUser(userID id.UserID) bool {
	return false
}

type WebsocketHandler func(WebsocketCommand) (ok bool, data interface{})

type StateStore interface {
	mautrix.StateStore

	IsRegistered(ctx context.Context, userID id.UserID) (bool, error)
	MarkRegistered(ctx context.Context, userID id.UserID) error

	GetPowerLevel(ctx context.Context, roomID id.RoomID, userID id.UserID) (int, error)
	GetPowerLevelRequirement(ctx context.Context, roomID id.RoomID, eventType event.Type) (int, error)
	HasPowerLevel(ctx context.Context, roomID id.RoomID, userID id.UserID, eventType event.Type) (bool, error)
}

// AppService is the main config for all appservices.
// It also serves as the appservice instance struct.
type AppService struct {
	HomeserverDomain string
	hsURLForClient   *url.URL
	Host             HostConfig

	Registration *Registration
	Log          zerolog.Logger

	txnIDC *TransactionIDCache

	Events         chan *event.Event
	ToDeviceEvents chan *event.Event
	DeviceLists    chan *mautrix.DeviceLists
	OTKCounts      chan *mautrix.OTKCount
	QueryHandler   QueryHandler
	StateStore     StateStore

	Router     *mux.Router
	UserAgent  string
	server     *http.Server
	HTTPClient *http.Client
	botClient  *mautrix.Client
	botIntent  *IntentAPI

	DefaultHTTPRetries int

	Live  bool
	Ready bool

	clients     map[id.UserID]*mautrix.Client
	clientsLock sync.RWMutex
	intents     map[id.UserID]*IntentAPI
	intentsLock sync.RWMutex

	ws                    *websocket.Conn
	wsWriteLock           sync.Mutex
	StopWebsocket         func(error)
	websocketHandlers     map[string]WebsocketHandler
	websocketHandlersLock sync.RWMutex
	websocketRequests     map[int]chan<- *WebsocketCommand
	websocketRequestsLock sync.RWMutex
	websocketRequestID    int32
	// ProcessID is an identifier sent to the websocket proxy for debugging connections
	ProcessID string

	WebsocketTransactionHandler WebsocketTransactionHandler

	DoublePuppetValue string
	GetProfile        func(userID id.UserID, roomID id.RoomID) *event.MemberEventContent
}

const DoublePuppetKey = "fi.mau.double_puppet_source"

func getDefaultProcessID() string {
	pid := syscall.Getpid()
	uid := syscall.Getuid()
	hostname, _ := os.Hostname()
	return fmt.Sprintf("%s-%d-%d", hostname, uid, pid)
}

func (as *AppService) PrepareWebsocket() {
	as.websocketHandlersLock.Lock()
	defer as.websocketHandlersLock.Unlock()
	if as.WebsocketTransactionHandler == nil {
		as.WebsocketTransactionHandler = as.defaultHandleWebsocketTransaction
	}
	if as.websocketHandlers == nil {
		as.websocketHandlers = make(map[string]WebsocketHandler, 32)
		as.websocketHandlers[WebsocketCommandHTTPProxy] = as.WebsocketHTTPProxy
		as.websocketRequests = make(map[int]chan<- *WebsocketCommand)
	}
}

// HostConfig contains info about how to host the appservice.
type HostConfig struct {
	// Hostname can be an IP address or an absolute path for a unix socket.
	Hostname string `yaml:"hostname"`
	// Port is required when Hostname is an IP address, optional for unix sockets
	Port uint16 `yaml:"port"`

	TLSKey  string `yaml:"tls_key,omitempty"`
	TLSCert string `yaml:"tls_cert,omitempty"`
}

// Address gets the whole address of the Appservice.
func (hc *HostConfig) Address() string {
	return fmt.Sprintf("%s:%d", hc.Hostname, hc.Port)
}

func (hc *HostConfig) IsUnixSocket() bool {
	return strings.HasPrefix(hc.Hostname, "/")
}

func (hc *HostConfig) IsConfigured() bool {
	return hc.IsUnixSocket() || hc.Port != 0
}

// Save saves this config into a file at the given path.
func (as *AppService) Save(path string) error {
	data, err := yaml.Marshal(as)
	if err != nil {
		return err
	}
	return os.WriteFile(path, data, 0644)
}

// YAML returns the config in YAML format.
func (as *AppService) YAML() (string, error) {
	data, err := yaml.Marshal(as)
	if err != nil {
		return "", err
	}
	return string(data), nil
}

// BotMXID returns the user ID corresponding to the appservice's sender_localpart
func (as *AppService) BotMXID() id.UserID {
	return id.NewUserID(as.Registration.SenderLocalpart, as.HomeserverDomain)
}

func (as *AppService) makeIntent(userID id.UserID) *IntentAPI {
	as.intentsLock.Lock()
	defer as.intentsLock.Unlock()

	intent, ok := as.intents[userID]
	if ok {
		return intent
	}

	localpart, homeserver, err := userID.Parse()
	if err != nil || len(localpart) == 0 || homeserver != as.HomeserverDomain {
		if err != nil {
			as.Log.Error().Err(err).
				Str("user_id", userID.String()).
				Msg("Failed to parse user ID")
		} else if len(localpart) == 0 {
			as.Log.Error().Err(err).
				Str("user_id", userID.String()).
				Msg("Failed to make intent: localpart is empty")
		} else if homeserver != as.HomeserverDomain {
			as.Log.Error().Err(err).
				Str("user_id", userID.String()).
				Str("expected_homeserver", as.HomeserverDomain).
				Msg("Failed to make intent: homeserver doesn't match")
		}
		return nil
	}
	intent = as.NewIntentAPI(localpart)
	as.intents[userID] = intent
	return intent
}

// Intent returns an [IntentAPI] object for the given user ID.
//
// This will return nil if the given user ID has an empty localpart,
// or if the server name is not the same as the appservice's HomeserverDomain.
// It does not currently validate that the given user ID is actually in the
// appservice's namespace. Validation may be added later.
func (as *AppService) Intent(userID id.UserID) *IntentAPI {
	as.intentsLock.RLock()
	intent, ok := as.intents[userID]
	as.intentsLock.RUnlock()
	if !ok {
		return as.makeIntent(userID)
	}
	return intent
}

// BotIntent returns an [IntentAPI] object for the appservice's sender_localpart user.
func (as *AppService) BotIntent() *IntentAPI {
	if as.botIntent == nil {
		as.botIntent = as.makeIntent(as.BotMXID())
	}
	return as.botIntent
}

// SetHomeserverURL updates the appservice's homeserver URL.
//
// Note that this does not affect already-created [IntentAPI] or [mautrix.Client] objects,
// so it should not be called after Intent or Client are called.
func (as *AppService) SetHomeserverURL(homeserverURL string) error {
	parsedURL, err := url.Parse(homeserverURL)
	if err != nil {
		return err
	}
	copied := *parsedURL
	as.hsURLForClient = &copied
	if as.hsURLForClient.Scheme == "unix" {
		as.hsURLForClient.Scheme = "http"
		as.hsURLForClient.Host = "unix"
		as.hsURLForClient.Path = ""
	} else if as.hsURLForClient.Scheme == "" {
		as.hsURLForClient.Scheme = "https"
	}
	as.hsURLForClient.RawPath = parsedURL.EscapedPath()

	jar, _ := cookiejar.New(&cookiejar.Options{PublicSuffixList: publicsuffix.List})
	as.HTTPClient = &http.Client{Timeout: 180 * time.Second, Jar: jar}
	if parsedURL.Scheme == "unix" {
		as.HTTPClient.Transport = &http.Transport{
			DialContext: func(_ context.Context, _, _ string) (net.Conn, error) {
				return net.Dial("unix", parsedURL.Path)
			},
		}
	}
	return nil
}

// NewMautrixClient creates a new [mautrix.Client] instance for the given user ID.
//
// This does not do any validation, and it does not cache the client.
// Usually you should prefer [AppService.Client] or [AppService.Intent] over this method.
func (as *AppService) NewMautrixClient(userID id.UserID) *mautrix.Client {
	return &mautrix.Client{
		HomeserverURL:       as.hsURLForClient,
		UserID:              userID,
		SetAppServiceUserID: true,
		AccessToken:         as.Registration.AppToken,
		UserAgent:           as.UserAgent,
		StateStore:          as.StateStore,
		Log:                 as.Log.With().Str("as_user_id", userID.String()).Logger(),
		Client:              as.HTTPClient,
		DefaultHTTPRetries:  as.DefaultHTTPRetries,
	}
}

// NewExternalMautrixClient creates a new [mautrix.Client] instance for an external user,
// with a token and homeserver URL separate from the main appservice.
//
// This is primarily meant to facilitate double puppeting in bridges, and is used by [bridge.doublePuppetUtil].
// Non-bridge appservices will likely not need this.
func (as *AppService) NewExternalMautrixClient(userID id.UserID, token string, homeserverURL string) (*mautrix.Client, error) {
	client := as.NewMautrixClient(userID)
	client.AccessToken = token
	client.SetAppServiceUserID = false
	if homeserverURL != "" {
		client.Client = &http.Client{Timeout: 180 * time.Second}
		var err error
		client.HomeserverURL, err = mautrix.ParseAndNormalizeBaseURL(homeserverURL)
		if err != nil {
			return nil, err
		}
	}
	return client, nil
}

func (as *AppService) makeClient(userID id.UserID) *mautrix.Client {
	as.clientsLock.Lock()
	defer as.clientsLock.Unlock()

	client, ok := as.clients[userID]
	if !ok {
		client = as.NewMautrixClient(userID)
		as.clients[userID] = client
	}
	return client
}

// Client returns the [mautrix.Client] instance for the given user ID.
//
// Unlike [AppService.Intent], this does not do any validation, and will always return a value.
// Usually you should prefer creating intents and using intent methods over direct client methods.
// You can always access the client inside an intent with [IntentAPI.Client].
func (as *AppService) Client(userID id.UserID) *mautrix.Client {
	as.clientsLock.RLock()
	client, ok := as.clients[userID]
	as.clientsLock.RUnlock()
	if !ok {
		return as.makeClient(userID)
	}
	return client
}

// BotClient returns the [mautrix.Client] instance for the appservice's sender_localpart user.
//
// Like with the generic Client method, [AppService.BotIntent] should be preferred over this.
func (as *AppService) BotClient() *mautrix.Client {
	if as.botClient == nil {
		as.botClient = as.makeClient(as.BotMXID())
	}
	return as.botClient
}