// Package clientapi implements the Client-Server API: the HTTP surface
// clients talk to.
//
// Phase 1 covers everything about identity — registration, login, sessions,
// devices, profiles, account data and capabilities. Rooms, messages and
// /sync arrive in Phases 3 and 4; the route table here is the place they
// will be added.
//
// Handlers are thin. They decode a request, map it onto a userapi call and
// shape the response; the rules live in userapi, and the storage in
// internal/storage. A handler that needs more than that is a sign something
// belongs further down.
package clientapi

import (
	"errors"
	"log/slog"
	"time"

	"github.com/dariuszjaniak/warp/server/internal/appservice"
	"github.com/dariuszjaniak/warp/server/internal/config"
	"github.com/dariuszjaniak/warp/server/internal/delayedevents"
	"github.com/dariuszjaniak/warp/server/internal/federation"
	"github.com/dariuszjaniak/warp/server/internal/httputil"
	"github.com/dariuszjaniak/warp/server/internal/keyserver"
	"github.com/dariuszjaniak/warp/server/internal/mediaapi"
	"github.com/dariuszjaniak/warp/server/internal/pushserver"
	"github.com/dariuszjaniak/warp/server/internal/ratelimit"
	"github.com/dariuszjaniak/warp/server/internal/roomserver"
	"github.com/dariuszjaniak/warp/server/internal/settings"
	"github.com/dariuszjaniak/warp/server/internal/storage"
	"github.com/dariuszjaniak/warp/server/internal/syncapi"
	"github.com/dariuszjaniak/warp/server/internal/userapi"
)

// ClientAPI serves the Client-Server API.
type ClientAPI struct {
	serverName    string
	clientBaseURL string
	users         *userapi.API
	rooms         *roomserver.API
	sync          *syncapi.API
	keys          *keyserver.API
	media         *mediaapi.API
	push          *pushserver.API
	legacyMedia   bool
	settings      *settings.Service
	federation    *federation.Gate
	remoteProfile RemoteProfiles
	regTokens     *userapi.RegistrationTokens
	appservices   *appservice.API
	turn          config.TURN
	delayed       *delayedevents.Service
	rtcTransports []RTCTransport
	openID        storage.OpenIDTokenStore
	log           *slog.Logger
	now           func() time.Time

	uia      *uiaStore
	clientIP ratelimit.KeyFunc

	// One limiter per endpoint class, so a client hammering /login cannot
	// spend the budget of /profile.
	limitDefault    *ratelimit.Limiter
	limitLogin      *ratelimit.Limiter
	limitRegister   *ratelimit.Limiter
	limitRoomCreate *ratelimit.Limiter
	limitJoin       *ratelimit.Limiter

	// limitSync is deliberately generous. A client is in /sync all the
	// time, and a long poll that is refused leaves it reconnecting in a
	// loop — the one place where rate limiting makes the load worse rather
	// than better.
	limitSync *ratelimit.Limiter

	// limitMedia covers downloads and thumbnails, which a client asks for
	// in bursts: every avatar in a room list at once.
	limitMedia *ratelimit.Limiter
}

// Options configure the component.
type Options struct {
	// ServerName is the Matrix server name.
	ServerName string

	// ClientBaseURL is the URL advertised to clients, the same value
	// /.well-known/matrix/client carries. A successful login repeats it so
	// that a client which only knew the server name does not have to fetch
	// the discovery document separately.
	ClientBaseURL string

	// Users is the userapi component.
	Users *userapi.API

	// Rooms is the roomserver component. Without it the room endpoints are
	// not registered at all, which is what the Phase 1 and Phase 2 tests
	// relied on and what keeps a half-wired server from offering a
	// createRoom it cannot honour.
	Rooms *roomserver.API

	// Sync is the syncapi component. Like the roomserver it is optional,
	// and for the same reason: without it /sync, /messages, /context and
	// the ephemeral endpoints answer M_UNRECOGNIZED rather than
	// pretending there is a stream to read.
	Sync *syncapi.API

	// Keys is the keyserver. Without it the end-to-end encryption
	// endpoints answer M_UNRECOGNIZED, which is how a client learns it
	// cannot encrypt here.
	Keys *keyserver.API

	// Media is the media repository. Without it the media endpoints
	// answer M_UNRECOGNIZED.
	Media *mediaapi.API

	// Push is the push server. Without it the push rule, pusher and
	// notification endpoints answer M_UNRECOGNIZED.
	Push *pushserver.API

	// LegacyMediaDownloads serves the deprecated unauthenticated download
	// and thumbnail endpoints too.
	LegacyMediaDownloads bool

	// Settings is the runtime-settings service; the registration switch is
	// read from it on every registration attempt.
	Settings *settings.Service

	// Federation gates the endpoints that would need a remote server.
	Federation *federation.Gate

	// RemoteProfiles asks another server for one of its users' profile.
	// Nil means remote profiles cannot be looked up at all.
	RemoteProfiles RemoteProfiles

	// Registration is the file configuration of the registration flow.
	Registration config.Registration

	// RegistrationTokens answers the m.login.registration_token stage.
	// Nil builds one from Registration's static tokens alone.
	RegistrationTokens *userapi.RegistrationTokens

	// AppServices is the application service component: who may act as
	// whom, the exclusive namespaces, and the queries. Nil means no
	// application services are registered.
	AppServices *appservice.API

	// RateLimit configures the per-endpoint buckets.
	RateLimit config.RateLimit

	// TURN is the relay handed to clients for calls.
	TURN config.TURN

	// RTC is the group call backend, listed at the MSC4143 transports
	// endpoint.
	RTC config.RTC

	// DelayedEvents schedules MSC4140 delayed events. Nil, or a service
	// with delayed events switched off, leaves the endpoints unregistered
	// and refuses the delay parameter.
	DelayedEvents *delayedevents.Service

	// OpenIDTokens keeps the OpenID tokens a user hands third parties,
	// such as the LiveKit JWT service of a group call. Nil leaves the
	// OpenID endpoints unregistered.
	OpenIDTokens storage.OpenIDTokenStore

	// TrustXForwardedFor takes the client address from the proxy header.
	TrustXForwardedFor bool

	Logger *slog.Logger

	// Now is the clock, so tests can expire sessions without waiting.
	Now func() time.Time
}

// New builds the component.
func New(opts Options) (*ClientAPI, error) {
	if opts.ServerName == "" {
		return nil, errors.New("clientapi: ServerName must not be empty")
	}
	if opts.Users == nil {
		return nil, errors.New("clientapi: Users must not be nil")
	}
	if opts.Settings == nil {
		return nil, errors.New("clientapi: Settings must not be nil")
	}
	if opts.Federation == nil {
		opts.Federation = federation.NewGate(nil, nil)
	}
	if opts.Logger == nil {
		opts.Logger = slog.Default()
	}
	if opts.Now == nil {
		opts.Now = time.Now
	}
	if opts.RegistrationTokens == nil {
		now := opts.Now
		opts.RegistrationTokens = userapi.NewRegistrationTokens(userapi.RegistrationTokensOptions{
			Static:   opts.Registration.Tokens,
			Required: opts.Registration.RequireToken,
			NowMS:    func() int64 { return now().UnixMilli() },
		})
	}
	if opts.AppServices == nil {
		var err error
		if opts.AppServices, err = appservice.New(appservice.Options{Logger: opts.Logger}); err != nil {
			return nil, err
		}
	}

	c := &ClientAPI{
		serverName:    opts.ServerName,
		clientBaseURL: opts.ClientBaseURL,
		users:         opts.Users,
		rooms:         opts.Rooms,
		sync:          opts.Sync,
		keys:          opts.Keys,
		media:         opts.Media,
		push:          opts.Push,
		legacyMedia:   opts.LegacyMediaDownloads,
		settings:      opts.Settings,
		federation:    opts.Federation,
		remoteProfile: opts.RemoteProfiles,
		regTokens:     opts.RegistrationTokens,
		appservices:   opts.AppServices,
		turn:          opts.TURN,
		delayed:       opts.DelayedEvents,
		rtcTransports: RTCTransports(opts.RTC.LiveKitServiceURL),
		openID:        opts.OpenIDTokens,
		log:           opts.Logger,
		now:           opts.Now,
		uia:           newUIAStore(uiaSessionTTL, opts.Now),
		clientIP:      ratelimit.ClientIP(opts.TrustXForwardedFor),
	}

	if opts.RateLimit.Enabled {
		c.limitDefault = ratelimit.New(bucket(opts.RateLimit.Default))
		c.limitLogin = ratelimit.New(bucket(opts.RateLimit.Login))
		c.limitRegister = ratelimit.New(bucket(opts.RateLimit.Register))
		// Creating a room writes a dozen events and joining one writes a
		// membership event into a room everybody in it then sees, so both
		// get their own, tighter bucket: the default one is sized for
		// reads.
		c.limitRoomCreate = ratelimit.New(bucket(opts.RateLimit.RoomCreate))
		c.limitJoin = ratelimit.New(bucket(opts.RateLimit.Join))
		c.limitSync = ratelimit.New(bucket(opts.RateLimit.Sync))
		c.limitMedia = ratelimit.New(bucket(opts.RateLimit.Media))
	} else {
		c.limitDefault, c.limitLogin, c.limitRegister =
			ratelimit.Disabled(), ratelimit.Disabled(), ratelimit.Disabled()
		c.limitRoomCreate, c.limitJoin = ratelimit.Disabled(), ratelimit.Disabled()
		c.limitSync, c.limitMedia = ratelimit.Disabled(), ratelimit.Disabled()
	}
	return c, nil
}

func bucket(b config.RateLimitBucket) ratelimit.Policy {
	return ratelimit.Policy{Burst: b.Burst, Interval: b.Interval}
}

// Client-Server API path prefixes. Warp serves the versioned paths only:
// the r0 prefix was deprecated in Matrix 1.4, and every client that still
// sends it also understands a 404 and falls back to version negotiation
// through /_matrix/client/versions.
const (
	v3 = "/_matrix/client/v3"
	v1 = "/_matrix/client/v1"
)

// RegisterRoutes adds the Client-Server endpoints to the router.
func (c *ClientAPI) RegisterRoutes(r *httputil.Router) {
	// Registration. The token-validity endpoint is v1 because that is the
	// version the spec introduced it at.
	c.public(r, "POST "+v3+"/register", c.limitRegister, c.handleRegister)
	c.public(r, "GET "+v3+"/register/available", c.limitRegister, c.handleRegisterAvailable)
	c.public(r, "GET "+v1+"/register/m.login.registration_token/validity",
		c.limitRegister, c.handleRegistrationTokenValidity)

	// Sessions.
	c.public(r, "GET "+v3+"/login", c.limitDefault, c.handleLoginFlows)
	c.public(r, "POST "+v3+"/login", c.limitLogin, c.handleLogin)
	c.public(r, "POST "+v3+"/refresh", c.limitLogin, c.handleRefresh)
	c.authed(r, "POST "+v3+"/logout", c.limitDefault, c.handleLogout)
	c.authed(r, "POST "+v3+"/logout/all", c.limitDefault, c.handleLogoutAll)

	// Account.
	c.authed(r, "GET "+v3+"/account/whoami", c.limitDefault, c.handleWhoami)
	c.authed(r, "POST "+v3+"/account/password", c.limitLogin, c.handleChangePassword)
	c.authed(r, "POST "+v3+"/account/deactivate", c.limitLogin, c.handleDeactivate)

	// Application services. The ping is the service checking that this
	// server can reach it, so it is authenticated with the service's own
	// token.
	c.authed(r, "POST "+v1+"/appservice/{appserviceID}/ping", c.limitDefault, c.handleAppServicePing)
	c.authed(r, "GET "+v3+"/capabilities", c.limitDefault, c.handleCapabilities)

	// Calls: the relay a client sets its peer connection up with.
	c.authed(r, "GET "+v3+"/voip/turnServer", c.limitDefault, c.handleTurnServer)
	c.registerOpenIDRoutes(r)
	c.registerDelayedEventRoutes(r)
	c.registerRTCRoutes(r)

	// Devices.
	c.authed(r, "GET "+v3+"/devices", c.limitDefault, c.handleGetDevices)
	c.authed(r, "GET "+v3+"/devices/{deviceID}", c.limitDefault, c.handleGetDevice)
	c.authed(r, "PUT "+v3+"/devices/{deviceID}", c.limitDefault, c.handlePutDevice)
	c.authed(r, "DELETE "+v3+"/devices/{deviceID}", c.limitDefault, c.handleDeleteDevice)
	c.authed(r, "POST "+v3+"/delete_devices", c.limitDefault, c.handleDeleteDevices)

	// Profiles are world-readable: a client showing a room member's name
	// has no token for that member's server, and the spec makes the GETs
	// unauthenticated for exactly that reason.
	c.public(r, "GET "+v3+"/profile/{userID}", c.limitDefault, c.handleGetProfile)
	c.public(r, "GET "+v3+"/profile/{userID}/displayname", c.limitDefault, c.handleGetDisplayName)
	c.public(r, "GET "+v3+"/profile/{userID}/avatar_url", c.limitDefault, c.handleGetAvatarURL)
	c.authed(r, "PUT "+v3+"/profile/{userID}/displayname", c.limitDefault, c.handlePutDisplayName)
	c.authed(r, "PUT "+v3+"/profile/{userID}/avatar_url", c.limitDefault, c.handlePutAvatarURL)

	// Account data.
	c.authed(r, "GET "+v3+"/user/{userID}/account_data/{dataType}",
		c.limitDefault, c.handleGetAccountData)
	c.authed(r, "PUT "+v3+"/user/{userID}/account_data/{dataType}",
		c.limitDefault, c.handlePutAccountData)
	c.authed(r, "GET "+v3+"/user/{userID}/rooms/{roomID}/account_data/{dataType}",
		c.limitDefault, c.handleGetRoomAccountData)
	c.authed(r, "PUT "+v3+"/user/{userID}/rooms/{roomID}/account_data/{dataType}",
		c.limitDefault, c.handlePutRoomAccountData)

	c.registerRoomRoutes(r)
	c.registerSyncRoutes(r)
	c.registerKeyRoutes(r)
	c.registerMediaRoutes(r)
	c.registerPushRoutes(r)
}

// registerSyncRoutes adds the endpoints the syncapi serves, if there is
// one.
//
// Like the room routes they are left unregistered rather than stubbed in a
// build without the component: a client that gets M_UNRECOGNIZED from
// /sync knows the server does not have it, where an empty success would
// have it believe nothing was happening.
func (c *ClientAPI) registerSyncRoutes(r *httputil.Router) {
	if c.sync == nil {
		return
	}

	c.authed(r, "GET "+v3+"/sync", c.limitSync, c.handleSync)
	c.authed(r, "POST "+slidingSyncPath, c.limitSync, c.handleSlidingSync)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/messages", c.limitDefault, c.handleMessages)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/context/{eventID}", c.limitDefault, c.handleContext)

	// Relations and threads, which the spec introduced at v1.
	c.authed(r, "GET "+v1+"/rooms/{roomID}/relations/{eventID}", c.limitDefault, c.handleRelations)
	c.authed(r, "GET "+v1+"/rooms/{roomID}/relations/{eventID}/{relType}", c.limitDefault, c.handleRelations)
	c.authed(r, "GET "+v1+"/rooms/{roomID}/relations/{eventID}/{relType}/{eventType}",
		c.limitDefault, c.handleRelations)
	c.authed(r, "GET "+v1+"/rooms/{roomID}/threads", c.limitDefault, c.handleThreads)

	c.authed(r, "POST "+v3+"/search", c.limitDefault, c.handleSearch)

	// Filters.
	c.authed(r, "POST "+v3+"/user/{userID}/filter", c.limitDefault, c.handlePostFilter)
	c.authed(r, "GET "+v3+"/user/{userID}/filter/{filterID}", c.limitDefault, c.handleGetFilter)

	// The ephemeral streams. Typing goes in the sync limiter's class
	// rather than the default one: a client sends one per keystroke-burst,
	// and it is the chattiest write in the API.
	c.authed(r, "PUT "+v3+"/rooms/{roomID}/typing/{userID}", c.limitSync, c.handlePutTyping)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/receipt/{receiptType}/{eventID}",
		c.limitSync, c.handlePostReceipt)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/read_markers", c.limitDefault, c.handlePostReadMarkers)

	// To-device messaging. A client encrypting for a busy room sends one
	// of these per device, so it shares the sync budget too.
	c.authed(r, "PUT "+v3+"/sendToDevice/{eventType}/{txnID}", c.limitSync, c.handleSendToDevice)

	// Presence.
	c.authed(r, "GET "+v3+"/presence/{userID}/status", c.limitDefault, c.handleGetPresence)
	c.authed(r, "PUT "+v3+"/presence/{userID}/status", c.limitSync, c.handlePutPresence)
}

// registerRoomRoutes adds the room endpoints, if there is a roomserver.
//
// A build without one answers them with M_UNRECOGNIZED, which is the right
// answer: a server that cannot store a room should say it has no createRoom
// rather than fail every call to it.
func (c *ClientAPI) registerRoomRoutes(r *httputil.Router) {
	if c.rooms == nil {
		return
	}

	c.authed(r, "POST "+v3+"/createRoom", c.limitRoomCreate, c.handleCreateRoom)

	// Membership. The two join endpoints differ only in what they are
	// addressed by: /join/{roomIdOrAlias} resolves an alias first.
	c.authed(r, "POST "+v3+"/join/{roomIDOrAlias}", c.limitJoin, c.handleJoinRoom)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/join", c.limitJoin, c.handleJoinRoomByID)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/leave", c.limitDefault, c.handleLeaveRoom)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/invite", c.limitDefault, c.handleInvite)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/kick", c.limitDefault, c.handleKick)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/ban", c.limitDefault, c.handleBan)
	c.authed(r, "POST "+v3+"/rooms/{roomID}/unban", c.limitDefault, c.handleUnban)

	// Sending. The state endpoint is registered twice, because the empty
	// state key is both valid and the common case and arrives in two
	// spellings: ".../state/m.room.name" and ".../state/m.room.name/".
	// The trailing-slash form uses a multi-segment wildcard, which is the
	// only kind Go's router matches against an empty segment — and which
	// also means a state key a client did not escape arrives whole rather
	// than as a 404.
	c.authed(r, "PUT "+v3+"/rooms/{roomID}/send/{eventType}/{txnID}",
		c.limitDefault, c.handleSendEvent)
	c.authed(r, "PUT "+v3+"/rooms/{roomID}/state/{eventType}",
		c.limitDefault, c.handlePutState)
	c.authed(r, "PUT "+v3+"/rooms/{roomID}/state/{eventType}/{stateKey...}",
		c.limitDefault, c.handlePutState)
	c.authed(r, "PUT "+v3+"/rooms/{roomID}/redact/{eventID}/{txnID}",
		c.limitDefault, c.handleRedact)

	// Reading.
	c.authed(r, "GET "+v3+"/rooms/{roomID}/event/{eventID}", c.limitDefault, c.handleGetEvent)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/state", c.limitDefault, c.handleGetState)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/state/{eventType}",
		c.limitDefault, c.handleGetStateEvent)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/state/{eventType}/{stateKey...}",
		c.limitDefault, c.handleGetStateEvent)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/members", c.limitDefault, c.handleGetMembers)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/joined_members",
		c.limitDefault, c.handleGetJoinedMembers)
	c.authed(r, "GET "+v3+"/joined_rooms", c.limitDefault, c.handleGetJoinedRooms)

	// Spaces, and the summary of a room the user may not be in.
	c.authed(r, "GET "+v1+"/rooms/{roomID}/hierarchy", c.limitDefault, c.handleHierarchy)
	c.authed(r, "GET "+v1+"/room_summary/{roomIDOrAlias}", c.limitDefault, c.handleRoomSummary)

	// The directory. Resolving an alias and reading the public room list
	// need no token: a client handed a link has to be able to follow it
	// before it decides whether to log in.
	c.public(r, "GET "+v3+"/directory/room/{roomAlias}", c.limitDefault, c.handleGetAlias)
	c.authed(r, "PUT "+v3+"/directory/room/{roomAlias}", c.limitDefault, c.handlePutAlias)
	c.authed(r, "DELETE "+v3+"/directory/room/{roomAlias}", c.limitDefault, c.handleDeleteAlias)
	c.authed(r, "GET "+v3+"/rooms/{roomID}/aliases", c.limitDefault, c.handleGetRoomAliases)

	c.public(r, "GET "+v3+"/publicRooms", c.limitDefault, c.handleGetPublicRooms)
	c.authed(r, "POST "+v3+"/publicRooms", c.limitDefault, c.handlePostPublicRooms)
	c.public(r, "GET "+v3+"/directory/list/room/{roomID}",
		c.limitDefault, c.handleGetRoomVisibility)
	c.authed(r, "PUT "+v3+"/directory/list/room/{roomID}",
		c.limitDefault, c.handlePutRoomVisibility)
}

// public registers an endpoint that needs no access token.
func (c *ClientAPI) public(r *httputil.Router, pattern string, limiter *ratelimit.Limiter, h httputil.Handler) {
	r.Handle(pattern, limiter.MiddlewareUnless(c.clientIP, c.rateLimitExempt)(httputil.Wrap(h)))
}

// authed registers an endpoint that needs one.
//
// The rate limiter still keys on the client address rather than the user:
// it runs before the token is resolved, and a limiter that had to hit the
// database to find its own key would be a denial of service of its own.
func (c *ClientAPI) authed(r *httputil.Router, pattern string, limiter *ratelimit.Limiter, h AuthedHandler) {
	r.Handle(pattern, limiter.MiddlewareUnless(c.clientIP, c.rateLimitExempt)(httputil.Wrap(c.withAuth(h))))
}