watchparty/server/src/types.ts

/**
 * Shared server-side types. Kept in one file rather than colocated with
 * each service, since several of these (Session, ItemDto, Party*) are used
 * by three or more services and colocating would just mean everyone
 * importing from whichever service happened to "own" the type first.
 *
 * Not shared with the client build (client/src/types.ts has its own,
 * overlapping copies of the DTO shapes) - the two projects compile
 * independently (tsc here, esbuild there), and a real shared package would
 * be a bigger structural commitment than this app's size justifies. A
 * handful of duplicated interfaces across the client/server boundary is a
 * normal, accepted trade-off for that - see docs/architecture.md.
 */

import type { Server as IoServer, Socket as IoSocket } from 'socket.io';

// --- Realtime (Socket.IO) event maps ---------------------------------------
// Typed once here rather than left as bare strings at every .emit()/.on()
// call site - see SocketGateway, MusicQueueService (which broadcasts
// "queueUpdated" directly, independent of SocketGateway's own handlers).

export interface ClientToServerEvents {
  subscribeLobby: () => void;
  /** deviceId: persisted client-side (see client/src/deviceId.ts) - lets
   *  the "join" handler tell "this same account, same device reconnecting"
   *  apart from "this same account, a genuinely different device" (see
   *  SocketGateway's own comment). force: true re-sends this after the
   *  user confirmed a "deviceConflict" takeover. */
  join: (msg: { partyId: string; deviceId: string; force?: boolean }) => void;
  playstate: (msg: { isPaused: boolean; positionTicks: number }) => void;
  next: () => void;
  voteSkip: () => void;
  musicPlaystate: (msg: { isPaused: boolean }) => void;
  /** No host check, same as "musicPlaystate" - see MusicQueueService's own
   *  class comment on why a seek gets the same permissive treatment as
   *  pause/resume (reversible, doesn't change what's playing) rather than
   *  "voteSkip"'s majority-vote gate (which does). */
  musicSeek: (msg: { positionSeconds: number }) => void;
  requestPause: () => void;
  requestResume: () => void;
  /** Host-only (checked server-side exactly like "next") - picks which
   *  audio/subtitle combination the party's *shared* burn-in stream uses,
   *  see TranscodeService. A null subtitleIndex clears it, dropping the
   *  party back to its normal party-shared Emby stream (PartyStreamService -
   *  also shared, just proxied rather than transcoded by us). Not for
   *  text subtitles - see "setTextSubtitle" below for those. Setting a
   *  real subtitleIndex here clears party.textSubtitleIndex (mutually
   *  exclusive - only one subtitle can be showing at once). */
  setBurnInSubtitle: (msg: { subtitleIndex: string | null; audioIndex?: string }) => void;
  /** Host-only, video-only (checked server-side exactly like "next") -
   *  picks (or clears) a *text* subtitle for the whole party, now that
   *  subtitle choice in general is party-wide rather than each viewer's
   *  own local pick (see docs/architecture.md - it wasn't at first, but
   *  that turned out to be the wrong call once people actually used
   *  this together). Every member still renders it themselves as a
   *  native <track> - this only syncs *which* one, not the rendering
   *  itself, so there's no server-side transcoding cost the way burn-in
   *  has. Setting a real subtitleIndex here clears party.burnInSubtitleIndex/
   *  burnInAudioIndex (mutually exclusive, same as above). */
  setTextSubtitle: (msg: { subtitleIndex: string | null }) => void;
  /** Host-only, video-only (checked server-side exactly like "next") -
   *  picks the audio track/quality the party's *shared* normal stream
   *  uses (PartyStreamService) - see docs/architecture.md's "One shared
   *  Emby stream per party" section for why this had to become a
   *  party-wide choice instead of each viewer's own: there's only ever
   *  one stream now, so there's only room for one set of encoding
   *  parameters behind it. Either field null/omitted means "Emby's own
   *  default" - same as an untouched picker meant before this. */
  setStreamOptions: (msg: { audioStreamIndex?: string | null; quality?: string | null }) => void;
  leave: () => void;
}

/** The socket "members" broadcast's shape - deliberately smaller than
 *  PartyPublicState.members below (no isPaused/positionTicks): that extra
 *  detail is REST-only (a follower's player only ever reads "playstate"
 *  events for position, never the member list, for that). */
export interface SocketMemberDto {
  userId: string;
  userName: string;
  isHost: boolean;
  connected: boolean;
}

export interface ServerToClientEvents {
  parties: (parties: LobbyPartyDto[]) => void;
  members: (members: SocketMemberDto[]) => void;
  playstate: (msg: { isPaused: boolean; positionTicks: number }) => void;
  itemChanged: (msg: {
    itemId: string;
    itemName: string;
    itemImageUrl: string;
    queueIndex: number;
    queueLength: number;
    hasNext: boolean;
  }) => void;
  queueUpdated: (state: MusicPublicState) => void;
  hostChanged: () => void;
  pauseRequested: (msg: { userId: string; userName: string }) => void;
  resumeRequested: (msg: { userId: string; userName: string }) => void;
  /** Sent only to the joining socket itself (never broadcast) when this
   *  account is already actively connected from a different deviceId -
   *  see SocketGateway's "join" handler. The socket stays connected but
   *  inert (not attached to the party) until the client either re-sends
   *  "join" with force:true or gives up. */
  deviceConflict: (msg: { partyId: string }) => void;
  /** Broadcast to the whole party room whenever the host changes (or
   *  clears) the party's shared burn-in subtitle/audio choice - see
   *  "setBurnInSubtitle" above and TranscodeService. Mirrors party.burnIn*
   *  below, which is what a fresh "getParty" (a follower joining
   *  mid-party) reads instead - this event is only for someone already
   *  connected when it changes live. */
  burnInChanged: (msg: { subtitleIndex: string | null; audioIndex: string | null }) => void;
  /** Broadcast to the whole party room whenever the host changes (or
   *  clears) the party's *text* subtitle choice - see "setTextSubtitle"
   *  above. Mirrors party.textSubtitleIndex below, which is what a
   *  fresh "getParty" (a follower joining mid-party) reads instead. */
  textSubtitleChanged: (msg: { subtitleIndex: string | null }) => void;
  /** Broadcast to the whole party room whenever the host changes the
   *  party's shared stream's audio track/quality - see
   *  "setStreamOptions" above and PartyStreamService. Mirrors
   *  party.streamAudioIndex/streamQuality below, which is what a fresh
   *  "getParty" (a follower joining mid-party) reads instead - this
   *  event is only for someone already connected when it changes live. */
  streamOptionsChanged: (msg: { audioStreamIndex: string | null; quality: string | null }) => void;
  errorMessage: (msg: { message: string }) => void;
}

export type AppSocket = IoSocket<ClientToServerEvents, ServerToClientEvents>;
export type AppServer = IoServer<ClientToServerEvents, ServerToClientEvents>;

// --- Auth / session -------------------------------------------------------

export interface EmbySession {
  embyToken: string;
  userId: string;
  userName: string;
  serverId: string;
  createdUtc: number;
}

// Augments Express's own Request type (declaration merging) so
// `req.embySession` is known everywhere without a separate "AuthedRequest"
// type at every route - set once by requireSession in index.ts.
declare global {
  // eslint-disable-next-line @typescript-eslint/no-namespace
  namespace Express {
    interface Request {
      embySession?: EmbySession;
    }
  }
}

// --- Catalog ---------------------------------------------------------------

/** Emby's own item shape, as returned by /Users/{id}/Items and friends -
 *  only the fields this app actually reads, not the full Emby schema. */
export interface EmbyItem {
  Id: string;
  Name: string;
  Overview?: string;
  ProductionYear?: number;
  Type?: string;
  SeriesId?: string;
  SeriesName?: string;
  ParentIndexNumber?: number;
  IndexNumber?: number;
  RunTimeTicks?: number;
  Album?: string;
  AlbumArtist?: string;
  Artists?: string[];
  /** The parent album's own id - only meaningful for Type: 'Audio'. See
   *  CatalogService.imageUrlFor: confirmed against a real server that an
   *  individual track essentially never has its own Primary image (every
   *  one sampled 500'd), only its album does - this is how an image URL
   *  falls back to the album's art instead. */
  AlbumId?: string;
}

/** This app's own DTO shape - what toItemDto() in CatalogService produces,
 *  sent to the client for every item type (movie/episode/series/artist/
 *  album/track/musicvideo alike). Track-specific fields are present but
 *  meaningless for anything else. */
export interface ItemDto {
  id: string;
  name: string;
  overview?: string;
  year?: number;
  type?: string;
  canWatchParty: boolean;
  imageUrl: string;
  embyUrl: string;
  durationTicks: number | null;
  indexNumber: number | null;
  artistName: string | null;
  albumName: string | null;
}

export interface LibraryDto {
  id: string;
  name: string;
  collectionType: string;
}

export interface SeasonDto {
  id: string;
  name: string;
  indexNumber?: number;
}

export interface PlaybackTrackOption {
  index: number;
  label: string;
  // Subtitle tracks only (undefined for audio - the concept doesn't apply).
  // false means this is an image/bitmap subtitle (PGS/VobSub/DVB, typically
  // a Blu-ray/DVD rip) - see IMAGE_SUBTITLE_CODECS's own comment. This app
  // renders subtitles as a native <track> (WebVTT, converted server-side
  // from whatever the source format is - see CatalogService.proxySubtitle),
  // which needs actual text; a bitmap has none to extract.
  isTextBased?: boolean;
}

export interface PlaybackOptionsDto {
  audioTracks: PlaybackTrackOption[];
  subtitleTracks: PlaybackTrackOption[];
}

/**
 * Emby's own native intro/credits detection (a library's own
 * EnableMarkerDetection option, run by its "Detect Episode Intros"
 * scheduled task - confirmed directly against a real server's
 * /openapi.json: MarkerType is one of Chapter/IntroStart/IntroEnd/
 * CreditsStart, mixed into the same Chapters array as the auto-generated
 * per-5-minutes ones). Every field is nullable, independently - the task
 * may not have reached this item yet, the library may not have the
 * feature enabled at all (it's per-library, not global), or a real
 * cold-open episode may genuinely have no IntroStart/IntroEnd. None of
 * that is an error - see CatalogService.getPlaybackMarkers - a caller
 * just checks each field for null before offering the matching skip
 * button. */
export interface PlaybackMarkersDto {
  introStartTicks: number | null;
  introEndTicks: number | null;
  creditsStartTicks: number | null;
}

// --- Party (video) -----------------------------------------------------------

/** One entry in a video party's fixed, pre-built queue (a movie/standalone
 *  episode is just a one-item queue) - see PartyService.create. */
export interface QueueItem {
  itemId: string;
  itemName: string;
  itemImageUrl: string;
}

export type MediaType = 'video' | 'music';

export interface PartyMember {
  userId: string;
  userName: string;
  connection: AppSocket | null;
  /** Whichever deviceId last successfully attached `connection` - null
   *  until the first real socket "join" (a member freshly created by the
   *  REST join/create routes has no live connection yet, so nothing to
   *  compare a new one against). See SocketGateway's "join" handler. */
  deviceId: string | null;
  /** This member's own Emby access token - set right after they
   *  create/join (REST) and re-confirmed on every socket "join" (see
   *  index.ts / SocketGateway). Needed so the periodic Emby-playstate
   *  sweep (index.ts) can report *their own* progress under *their own*
   *  Emby account, not just the host's - see PlaystateService and
   *  docs/architecture.md. Never sent to the client - see
   *  PartyService.toPublicState, which never includes it. Null until
   *  the first of those two things happens (mirrors deviceId's own
   *  null-until-known convention). */
  embyToken: string | null;
  isPaused: boolean;
  positionTicks: number;
  lastUpdatedUtc: number;
  lastPauseRequestUtc?: number;
  lastResumeRequestUtc?: number;
  /** This member's own live Emby Sessions-API entry, if one's currently
   *  open - see EmbySessionService. Null whenever they don't have one
   *  (not connected/no token yet, or the periodic sweep hasn't started
   *  one for their current item yet). `itemId` is what the sweep compares
   *  against on each tick to notice an item change (stop the old
   *  session, start a fresh one) - `mediaSourceId`/`playSessionId` are
   *  cached here specifically so a Progress report can reuse them
   *  without renegotiating PlaybackInfo on every single tick. */
  embySession: EmbyPlaybackSession | null;
}

/** See PartyMember.embySession's own comment. */
export interface EmbyPlaybackSession {
  itemId: string;
  mediaSourceId: string;
  playSessionId: string;
}

/** The full internal party record - never sent to the client as-is, see
 *  PartyService.toPublicState for the shape that actually goes out. */
export interface Party {
  id: string;
  mediaType: MediaType;
  itemId: string;
  itemName: string;
  itemImageUrl: string;
  queue: QueueItem[];
  queueIndex: number;
  hostUserId: string;
  createdUtc: number;
  lastActivityUtc: number;
  members: Map<string, PartyMember>;
  /** Only present once MusicQueueService.init() has run - i.e. mediaType
   *  === 'music'. Owned and shaped entirely by MusicQueueService; every
   *  other service treats this as an opaque bag it just carries around. */
  music?: MusicState;
  /** Video only - the host's current pick for the party's *shared*
   *  burn-in stream (see TranscodeService), null when nobody's picked one
   *  and the party is just using its normal party-shared Emby stream
   *  instead (PartyStreamService - also shared, just proxied rather than
   *  transcoded by us). Both null or both set - never one without the
   *  other, see SocketGateway's "setBurnInSubtitle" handler. Persisted
   *  here (not just broadcast live) so a follower joining mid-party, or
   *  a page reload, picks up the party's current choice from a plain
   *  "getParty" - same reason itemId/queueIndex live here too. */
  burnInSubtitleIndex: string | null;
  burnInAudioIndex: string | null;
  /** Video only - the host's current pick for a *text* subtitle, party-
   *  wide - see SocketGateway's "setTextSubtitle" handler. Mutually
   *  exclusive with burnInSubtitleIndex (picking one clears the other -
   *  only one subtitle can be showing at once). Every member still
   *  renders it themselves as a native <track> - this only syncs
   *  *which* one, no server-side transcoding involved, unlike burn-in. */
  textSubtitleIndex: string | null;
  /** Video only - the host's current pick for the party's normal
   *  *shared* Emby stream (PartyStreamService) - null means "Emby's own
   *  default", same as an untouched picker meant before streams were
   *  shared. There is only ever one of these now (not one per viewer),
   *  so - like burnIn* above - this is party-wide, host-set state, not
   *  something each client tracks locally; see SocketGateway's
   *  "setStreamOptions" handler. Meaningless for a music party -
   *  MusicBar.ts never had this picker in the first place. */
  streamAudioIndex: string | null;
  streamQuality: string | null;
}

export interface PublicMember {
  userId: string;
  userName: string;
  isHost: boolean;
  isPaused: boolean;
  positionTicks: number;
  connected: boolean;
}

/** What GET /api/parties/:id and POST /api/parties actually return - the
 *  video queue fields (hasNext/queueLength/queueIndex) are meaningless for
 *  a music party, which carries `music` instead. */
export interface PartyPublicState {
  partyId: string;
  mediaType: MediaType;
  itemId: string;
  itemName: string;
  itemImageUrl: string;
  createdUtc: number;
  hasNext: boolean;
  queueLength: number;
  queueIndex: number;
  hostUserName: string | null;
  memberCount: number;
  youAreHost: boolean;
  members: PublicMember[];
  music: MusicPublicState | null;
  burnInSubtitleIndex: string | null;
  burnInAudioIndex: string | null;
  textSubtitleIndex: string | null;
  streamAudioIndex: string | null;
  streamQuality: string | null;
}

export interface LobbyPartyDto {
  partyId: string;
  mediaType: MediaType;
  itemId: string;
  itemName: string;
  itemImageUrl: string;
  hostUserName: string | null;
  memberCount: number;
  createdUtc: number; // music parties (and any party's own age) still key off this
  // Video only - null for music (no single "elapsed" makes sense across a
  // rotating queue of tracks the way it does for one movie/episode). The
  // host's own last-reported position/pause state (same values their
  // "playstate" heartbeat already tracks - see SocketGateway) plus the
  // moment they were reported, so the client can tick a live, pause-aware
  // "elapsed" label itself between broadcasts instead of the home page
  // just counting wall-clock time since createdUtc regardless of whether
  // the movie was ever actually playing that whole time.
  positionTicks: number | null;
  isPaused: boolean | null;
  positionUpdatedUtc: number | null;
}

export interface LeaveResult {
  hostChanged: boolean;
  newHostUserId: string | null;
  destroyed: boolean;
}

// --- Music (participative queue) --------------------------------------------

/** One track in a music party's shared, mutable queue - see
 *  MusicQueueService. Distinct from QueueItem above: that one is fixed and
 *  built once server-side, this one grows live as members add to it. */
export interface MusicTrack {
  itemId: string;
  itemName: string;
  artistName: string | null;
  albumName: string | null;
  itemImageUrl: string;
  durationSeconds: number | null;
  addedByUserId: string;
  addedByUserName: string;
}

/** What a client actually sends when adding a track (POST
 *  /api/parties/:id/tracks) - Emby-tick-shaped, converted to
 *  MusicTrack.durationSeconds once by MusicQueueService.addTrack. */
export interface MusicTrackInput {
  itemId: string;
  itemName: string;
  artistName?: string | null;
  albumName?: string | null;
  itemImageUrl: string;
  durationTicks?: number | null;
}

export interface MusicCurrentTrack {
  track: MusicTrack;
  startedUtc: number;
  isPaused: boolean;
  /** Elapsed ms at the moment it was paused - null while playing. Combined
   *  with `isPaused`, this is the only state MusicQueueService.getElapsedSeconds
   *  needs; there is no separate ticking "position" stored anywhere. */
  pausedElapsedMs: number | null;
}

/** party.music - owned entirely by MusicQueueService (see its class
 *  comment for why this is a separate service rather than living in
 *  PartyService alongside the video queue fields). */
export interface MusicState {
  queue: MusicTrack[];
  current: MusicCurrentTrack | null;
  skipVotes: Set<string>;
  advanceTimer: NodeJS.Timeout | null;
}

export interface MusicCurrentPublic extends MusicTrack {
  isPaused: boolean;
  elapsedSeconds: number;
}

/** The "queueUpdated" broadcast payload / party.music's public shape. */
export interface MusicPublicState {
  queue: MusicTrack[];
  current: MusicCurrentPublic | null;
  skipVotes: number;
}