scrabble-game/ui/src/lib/codec.ts

// FlatBuffers <-> domain-model codec. The real transport encodes each request table
// and decodes each response/event table here, mirroring the gateway's Go encoders in
// reverse. The screens only ever see the plain model (lib/model), never these wire
// types.

import { Builder, ByteBuffer, type Offset } from 'flatbuffers';
import * as fb from '../gen/fbs/scrabblefb';
import type { PlacedTile } from './client';
import type {
  AccountRef,
  ChatMessage,
  EvalResult,
  FriendCode,
  GameList,
  GameView,
  GcgExport,
  History,
  HintResult,
  Invitation,
  InvitationInvitee,
  InvitationSettings,
  MatchResult,
  MoveRecord,
  MoveResult,
  Profile,
  ProfileUpdate,
  PushEvent,
  Seat,
  Session,
  StateView,
  Stats,
  Tile,
  Variant,
  WordCheckResult,
} from './model';

// --- request encoders ---

function buildTile(b: Builder, t: PlacedTile): Offset {
  const letter = b.createString(t.letter);
  fb.TileRecord.startTileRecord(b);
  fb.TileRecord.addRow(b, t.row);
  fb.TileRecord.addCol(b, t.col);
  fb.TileRecord.addLetter(b, letter);
  fb.TileRecord.addBlank(b, t.blank);
  return fb.TileRecord.endTileRecord(b);
}

function finish(b: Builder, root: Offset): Uint8Array {
  b.finish(root);
  return b.asUint8Array();
}

export const empty = (): Uint8Array => new Uint8Array();

export function encodeGameAction(gameId: string): Uint8Array {
  const b = new Builder(64);
  const gid = b.createString(gameId);
  fb.GameActionRequest.startGameActionRequest(b);
  fb.GameActionRequest.addGameId(b, gid);
  return finish(b, fb.GameActionRequest.endGameActionRequest(b));
}

export function encodeStateRequest(gameId: string): Uint8Array {
  const b = new Builder(64);
  const gid = b.createString(gameId);
  fb.StateRequest.startStateRequest(b);
  fb.StateRequest.addGameId(b, gid);
  return finish(b, fb.StateRequest.endStateRequest(b));
}

export function encodeSubmitPlay(gameId: string, dir: 'H' | 'V', tiles: PlacedTile[]): Uint8Array {
  const b = new Builder(256);
  const tileOffs = tiles.map((t) => buildTile(b, t));
  const vec = fb.SubmitPlayRequest.createTilesVector(b, tileOffs);
  const gid = b.createString(gameId);
  const d = b.createString(dir);
  fb.SubmitPlayRequest.startSubmitPlayRequest(b);
  fb.SubmitPlayRequest.addGameId(b, gid);
  fb.SubmitPlayRequest.addDir(b, d);
  fb.SubmitPlayRequest.addTiles(b, vec);
  return finish(b, fb.SubmitPlayRequest.endSubmitPlayRequest(b));
}

export function encodeEval(gameId: string, dir: 'H' | 'V', tiles: PlacedTile[]): Uint8Array {
  const b = new Builder(256);
  const tileOffs = tiles.map((t) => buildTile(b, t));
  const vec = fb.EvalRequest.createTilesVector(b, tileOffs);
  const gid = b.createString(gameId);
  const d = b.createString(dir);
  fb.EvalRequest.startEvalRequest(b);
  fb.EvalRequest.addGameId(b, gid);
  fb.EvalRequest.addDir(b, d);
  fb.EvalRequest.addTiles(b, vec);
  return finish(b, fb.EvalRequest.endEvalRequest(b));
}

export function encodeExchange(gameId: string, tiles: string[]): Uint8Array {
  const b = new Builder(128);
  const offs = tiles.map((s) => b.createString(s));
  const vec = fb.ExchangeRequest.createTilesVector(b, offs);
  const gid = b.createString(gameId);
  fb.ExchangeRequest.startExchangeRequest(b);
  fb.ExchangeRequest.addGameId(b, gid);
  fb.ExchangeRequest.addTiles(b, vec);
  return finish(b, fb.ExchangeRequest.endExchangeRequest(b));
}

export function encodeCheckWord(gameId: string, word: string): Uint8Array {
  const b = new Builder(128);
  const gid = b.createString(gameId);
  const w = b.createString(word);
  fb.CheckWordRequest.startCheckWordRequest(b);
  fb.CheckWordRequest.addGameId(b, gid);
  fb.CheckWordRequest.addWord(b, w);
  return finish(b, fb.CheckWordRequest.endCheckWordRequest(b));
}

export function encodeComplaint(gameId: string, word: string, note: string): Uint8Array {
  const b = new Builder(256);
  const gid = b.createString(gameId);
  const w = b.createString(word);
  const n = b.createString(note);
  fb.ComplaintRequest.startComplaintRequest(b);
  fb.ComplaintRequest.addGameId(b, gid);
  fb.ComplaintRequest.addWord(b, w);
  fb.ComplaintRequest.addNote(b, n);
  return finish(b, fb.ComplaintRequest.endComplaintRequest(b));
}

export function encodeEnqueue(variant: Variant): Uint8Array {
  const b = new Builder(64);
  const v = b.createString(variant);
  fb.EnqueueRequest.startEnqueueRequest(b);
  fb.EnqueueRequest.addVariant(b, v);
  return finish(b, fb.EnqueueRequest.endEnqueueRequest(b));
}

export function encodeChatPost(gameId: string, body: string): Uint8Array {
  const b = new Builder(128);
  const gid = b.createString(gameId);
  const bd = b.createString(body);
  fb.ChatPostRequest.startChatPostRequest(b);
  fb.ChatPostRequest.addGameId(b, gid);
  fb.ChatPostRequest.addBody(b, bd);
  return finish(b, fb.ChatPostRequest.endChatPostRequest(b));
}

export function encodeTelegramLogin(initData: string): Uint8Array {
  const b = new Builder(512);
  const d = b.createString(initData);
  fb.TelegramLoginRequest.startTelegramLoginRequest(b);
  fb.TelegramLoginRequest.addInitData(b, d);
  return finish(b, fb.TelegramLoginRequest.endTelegramLoginRequest(b));
}

export function encodeGuestLogin(locale: string): Uint8Array {
  const b = new Builder(64);
  const l = b.createString(locale);
  fb.GuestLoginRequest.startGuestLoginRequest(b);
  fb.GuestLoginRequest.addLocale(b, l);
  return finish(b, fb.GuestLoginRequest.endGuestLoginRequest(b));
}

export function encodeEmailRequest(email: string): Uint8Array {
  const b = new Builder(128);
  const e = b.createString(email);
  fb.EmailRequestRequest.startEmailRequestRequest(b);
  fb.EmailRequestRequest.addEmail(b, e);
  return finish(b, fb.EmailRequestRequest.endEmailRequestRequest(b));
}

export function encodeEmailLogin(email: string, code: string): Uint8Array {
  const b = new Builder(128);
  const e = b.createString(email);
  const c = b.createString(code);
  fb.EmailLoginRequest.startEmailLoginRequest(b);
  fb.EmailLoginRequest.addEmail(b, e);
  fb.EmailLoginRequest.addCode(b, c);
  return finish(b, fb.EmailLoginRequest.endEmailLoginRequest(b));
}

// --- response decoders ---

function s(v: string | null): string {
  return v ?? '';
}

function decodeTile(t: fb.TileRecord): Tile {
  return { row: t.row(), col: t.col(), letter: s(t.letter()), blank: t.blank() };
}

function decodeSeat(v: fb.SeatView): Seat {
  return {
    seat: v.seat(),
    accountId: s(v.accountId()),
    displayName: s(v.displayName()),
    score: v.score(),
    hintsUsed: v.hintsUsed(),
    isWinner: v.isWinner(),
  };
}

function decodeGameView(g: fb.GameView): GameView {
  const seats: Seat[] = [];
  for (let i = 0; i < g.seatsLength(); i++) {
    const sv = g.seats(i);
    if (sv) seats.push(decodeSeat(sv));
  }
  return {
    id: s(g.id()),
    variant: s(g.variant()) as Variant,
    dictVersion: s(g.dictVersion()),
    status: s(g.status()),
    players: g.players(),
    toMove: g.toMove(),
    turnTimeoutSecs: g.turnTimeoutSecs(),
    moveCount: g.moveCount(),
    endReason: s(g.endReason()),
    seats,
  };
}

function decodeMove(m: fb.MoveRecord): MoveRecord {
  const tiles: Tile[] = [];
  for (let i = 0; i < m.tilesLength(); i++) {
    const t = m.tiles(i);
    if (t) tiles.push(decodeTile(t));
  }
  const words: string[] = [];
  for (let i = 0; i < m.wordsLength(); i++) words.push(s(m.words(i)));
  return {
    player: m.player(),
    action: s(m.action()),
    dir: s(m.dir()),
    mainRow: m.mainRow(),
    mainCol: m.mainCol(),
    tiles,
    words,
    count: m.count(),
    score: m.score(),
    total: m.total(),
  };
}

function decodeChatMsg(m: fb.ChatMessage): ChatMessage {
  return {
    id: s(m.id()),
    gameId: s(m.gameId()),
    senderId: s(m.senderId()),
    kind: s(m.kind()),
    body: s(m.body()),
    createdAtUnix: Number(m.createdAtUnix()),
  };
}

export function decodeSession(buf: Uint8Array): Session {
  const t = fb.Session.getRootAsSession(new ByteBuffer(buf));
  return { token: s(t.token()), userId: s(t.userId()), isGuest: t.isGuest(), displayName: s(t.displayName()) };
}

export function decodeProfile(buf: Uint8Array): Profile {
  const p = fb.Profile.getRootAsProfile(new ByteBuffer(buf));
  return {
    userId: s(p.userId()),
    displayName: s(p.displayName()),
    preferredLanguage: s(p.preferredLanguage()),
    timeZone: s(p.timeZone()),
    awayStart: s(p.awayStart()),
    awayEnd: s(p.awayEnd()),
    hintBalance: p.hintBalance(),
    blockChat: p.blockChat(),
    blockFriendRequests: p.blockFriendRequests(),
    isGuest: p.isGuest(),
    notificationsInAppOnly: p.notificationsInAppOnly(),
  };
}

export function decodeStateView(buf: Uint8Array): StateView {
  const v = fb.StateView.getRootAsStateView(new ByteBuffer(buf));
  const g = v.game();
  const rack: string[] = [];
  for (let i = 0; i < v.rackLength(); i++) rack.push(s(v.rack(i)));
  return {
    game: g ? decodeGameView(g) : emptyGame(),
    seat: v.seat(),
    rack,
    bagLen: v.bagLen(),
    hintsRemaining: v.hintsRemaining(),
  };
}

export function decodeMoveResult(buf: Uint8Array): MoveResult {
  const r = fb.MoveResult.getRootAsMoveResult(new ByteBuffer(buf));
  const m = r.move();
  const g = r.game();
  return { move: m ? decodeMove(m) : emptyMove(), game: g ? decodeGameView(g) : emptyGame() };
}

export function decodeHintResult(buf: Uint8Array): HintResult {
  const r = fb.HintResult.getRootAsHintResult(new ByteBuffer(buf));
  const m = r.move();
  return { move: m ? decodeMove(m) : emptyMove(), hintsRemaining: r.hintsRemaining() };
}

export function decodeEvalResult(buf: Uint8Array): EvalResult {
  const r = fb.EvalResult.getRootAsEvalResult(new ByteBuffer(buf));
  const words: string[] = [];
  for (let i = 0; i < r.wordsLength(); i++) words.push(s(r.words(i)));
  return { legal: r.legal(), score: r.score(), words };
}

export function decodeWordCheck(buf: Uint8Array): WordCheckResult {
  const r = fb.WordCheckResult.getRootAsWordCheckResult(new ByteBuffer(buf));
  return { word: s(r.word()), legal: r.legal() };
}

export function decodeHistory(buf: Uint8Array): History {
  const h = fb.History.getRootAsHistory(new ByteBuffer(buf));
  const moves: MoveRecord[] = [];
  for (let i = 0; i < h.movesLength(); i++) {
    const m = h.moves(i);
    if (m) moves.push(decodeMove(m));
  }
  return { gameId: s(h.gameId()), moves };
}

export function decodeGameList(buf: Uint8Array): GameList {
  const gl = fb.GameList.getRootAsGameList(new ByteBuffer(buf));
  const games: GameView[] = [];
  for (let i = 0; i < gl.gamesLength(); i++) {
    const g = gl.games(i);
    if (g) games.push(decodeGameView(g));
  }
  return { games };
}

export function decodeMatchResult(buf: Uint8Array): MatchResult {
  const m = fb.MatchResult.getRootAsMatchResult(new ByteBuffer(buf));
  const g = m.game();
  return { matched: m.matched(), game: m.matched() && g ? decodeGameView(g) : undefined };
}

export function decodeChatMessage(buf: Uint8Array): ChatMessage {
  return decodeChatMsg(fb.ChatMessage.getRootAsChatMessage(new ByteBuffer(buf)));
}

export function decodeChatList(buf: Uint8Array): ChatMessage[] {
  const cl = fb.ChatList.getRootAsChatList(new ByteBuffer(buf));
  const out: ChatMessage[] = [];
  for (let i = 0; i < cl.messagesLength(); i++) {
    const m = cl.messages(i);
    if (m) out.push(decodeChatMsg(m));
  }
  return out;
}

export function decodeEvent(kind: string, payload: Uint8Array): PushEvent | null {
  const bb = new ByteBuffer(payload);
  switch (kind) {
    case 'your_turn': {
      const e = fb.YourTurnEvent.getRootAsYourTurnEvent(bb);
      return { kind: 'your_turn', gameId: s(e.gameId()), deadlineUnix: Number(e.deadlineUnix()) };
    }
    case 'opponent_moved': {
      const e = fb.OpponentMovedEvent.getRootAsOpponentMovedEvent(bb);
      return { kind: 'opponent_moved', gameId: s(e.gameId()), seat: e.seat(), action: s(e.action()), score: e.score(), total: e.total() };
    }
    case 'chat_message':
      return { kind: 'chat_message', message: decodeChatMsg(fb.ChatMessage.getRootAsChatMessage(bb)) };
    case 'nudge': {
      const e = fb.NudgeEvent.getRootAsNudgeEvent(bb);
      return { kind: 'nudge', gameId: s(e.gameId()), fromUserId: s(e.fromUserId()) };
    }
    case 'match_found': {
      const e = fb.MatchFoundEvent.getRootAsMatchFoundEvent(bb);
      return { kind: 'match_found', gameId: s(e.gameId()) };
    }
    case 'notify': {
      const e = fb.NotificationEvent.getRootAsNotificationEvent(bb);
      return { kind: 'notify', sub: s(e.kind()) };
    }
    case 'heartbeat':
      return { kind: 'heartbeat' };
    default:
      return null;
  }
}

// --- Stage 8 encoders ---

export function encodeTarget(accountId: string): Uint8Array {
  const b = new Builder(64);
  const id = b.createString(accountId);
  fb.TargetRequest.startTargetRequest(b);
  fb.TargetRequest.addAccountId(b, id);
  return finish(b, fb.TargetRequest.endTargetRequest(b));
}

export function encodeFriendRespond(requesterId: string, accept: boolean): Uint8Array {
  const b = new Builder(64);
  const id = b.createString(requesterId);
  fb.FriendRespondRequest.startFriendRespondRequest(b);
  fb.FriendRespondRequest.addRequesterId(b, id);
  fb.FriendRespondRequest.addAccept(b, accept);
  return finish(b, fb.FriendRespondRequest.endFriendRespondRequest(b));
}

export function encodeRedeemCode(code: string): Uint8Array {
  const b = new Builder(32);
  const c = b.createString(code);
  fb.RedeemCodeRequest.startRedeemCodeRequest(b);
  fb.RedeemCodeRequest.addCode(b, c);
  return finish(b, fb.RedeemCodeRequest.endRedeemCodeRequest(b));
}

export function encodeCreateInvitation(inviteeIds: string[], st: InvitationSettings): Uint8Array {
  const b = new Builder(256);
  const idOffs = inviteeIds.map((id) => b.createString(id));
  const ids = fb.CreateInvitationRequest.createInviteeIdsVector(b, idOffs);
  const variant = b.createString(st.variant);
  const dropout = b.createString(st.dropoutTiles);
  fb.CreateInvitationRequest.startCreateInvitationRequest(b);
  fb.CreateInvitationRequest.addInviteeIds(b, ids);
  fb.CreateInvitationRequest.addVariant(b, variant);
  fb.CreateInvitationRequest.addTurnTimeoutSecs(b, st.turnTimeoutSecs);
  fb.CreateInvitationRequest.addHintsAllowed(b, st.hintsAllowed);
  fb.CreateInvitationRequest.addHintsPerPlayer(b, st.hintsPerPlayer);
  fb.CreateInvitationRequest.addDropoutTiles(b, dropout);
  return finish(b, fb.CreateInvitationRequest.endCreateInvitationRequest(b));
}

export function encodeInvitationAction(invitationId: string): Uint8Array {
  const b = new Builder(64);
  const id = b.createString(invitationId);
  fb.InvitationActionRequest.startInvitationActionRequest(b);
  fb.InvitationActionRequest.addInvitationId(b, id);
  return finish(b, fb.InvitationActionRequest.endInvitationActionRequest(b));
}

export function encodeUpdateProfile(p: ProfileUpdate): Uint8Array {
  const b = new Builder(256);
  const name = b.createString(p.displayName);
  const lang = b.createString(p.preferredLanguage);
  const tz = b.createString(p.timeZone);
  const as = b.createString(p.awayStart);
  const ae = b.createString(p.awayEnd);
  fb.UpdateProfileRequest.startUpdateProfileRequest(b);
  fb.UpdateProfileRequest.addDisplayName(b, name);
  fb.UpdateProfileRequest.addPreferredLanguage(b, lang);
  fb.UpdateProfileRequest.addTimeZone(b, tz);
  fb.UpdateProfileRequest.addAwayStart(b, as);
  fb.UpdateProfileRequest.addAwayEnd(b, ae);
  fb.UpdateProfileRequest.addBlockChat(b, p.blockChat);
  fb.UpdateProfileRequest.addBlockFriendRequests(b, p.blockFriendRequests);
  fb.UpdateProfileRequest.addNotificationsInAppOnly(b, p.notificationsInAppOnly);
  return finish(b, fb.UpdateProfileRequest.endUpdateProfileRequest(b));
}

export function encodeEmailBind(email: string): Uint8Array {
  const b = new Builder(128);
  const e = b.createString(email);
  fb.EmailBindRequest.startEmailBindRequest(b);
  fb.EmailBindRequest.addEmail(b, e);
  return finish(b, fb.EmailBindRequest.endEmailBindRequest(b));
}

export function encodeEmailConfirm(email: string, code: string): Uint8Array {
  const b = new Builder(128);
  const e = b.createString(email);
  const c = b.createString(code);
  fb.EmailConfirmRequest.startEmailConfirmRequest(b);
  fb.EmailConfirmRequest.addEmail(b, e);
  fb.EmailConfirmRequest.addCode(b, c);
  return finish(b, fb.EmailConfirmRequest.endEmailConfirmRequest(b));
}

// --- Stage 8 decoders ---

function decodeAccountRef(r: fb.AccountRef): AccountRef {
  return { accountId: s(r.accountId()), displayName: s(r.displayName()) };
}

export function decodeFriendList(buf: Uint8Array): AccountRef[] {
  const l = fb.FriendList.getRootAsFriendList(new ByteBuffer(buf));
  const out: AccountRef[] = [];
  for (let i = 0; i < l.friendsLength(); i++) {
    const r = l.friends(i);
    if (r) out.push(decodeAccountRef(r));
  }
  return out;
}

export function decodeIncomingList(buf: Uint8Array): AccountRef[] {
  const l = fb.IncomingRequestList.getRootAsIncomingRequestList(new ByteBuffer(buf));
  const out: AccountRef[] = [];
  for (let i = 0; i < l.requestsLength(); i++) {
    const r = l.requests(i);
    if (r) out.push(decodeAccountRef(r));
  }
  return out;
}

export function decodeBlockList(buf: Uint8Array): AccountRef[] {
  const l = fb.BlockList.getRootAsBlockList(new ByteBuffer(buf));
  const out: AccountRef[] = [];
  for (let i = 0; i < l.blockedLength(); i++) {
    const r = l.blocked(i);
    if (r) out.push(decodeAccountRef(r));
  }
  return out;
}

export function decodeFriendCode(buf: Uint8Array): FriendCode {
  const c = fb.FriendCode.getRootAsFriendCode(new ByteBuffer(buf));
  return { code: s(c.code()), expiresAtUnix: Number(c.expiresAtUnix()) };
}

export function decodeRedeemResult(buf: Uint8Array): AccountRef {
  const r = fb.RedeemResult.getRootAsRedeemResult(new ByteBuffer(buf));
  const f = r.friend();
  return f ? decodeAccountRef(f) : { accountId: '', displayName: '' };
}

export function decodeStats(buf: Uint8Array): Stats {
  const v = fb.StatsView.getRootAsStatsView(new ByteBuffer(buf));
  return {
    wins: v.wins(),
    losses: v.losses(),
    draws: v.draws(),
    maxGamePoints: v.maxGamePoints(),
    maxWordPoints: v.maxWordPoints(),
  };
}

function decodeInvitationTable(i: fb.Invitation): Invitation {
  const inviter = i.inviter();
  const invitees: InvitationInvitee[] = [];
  for (let k = 0; k < i.inviteesLength(); k++) {
    const iv = i.invitees(k);
    if (iv) {
      invitees.push({
        accountId: s(iv.accountId()),
        displayName: s(iv.displayName()),
        seat: iv.seat(),
        response: s(iv.response()),
      });
    }
  }
  return {
    id: s(i.id()),
    inviter: inviter ? decodeAccountRef(inviter) : { accountId: '', displayName: '' },
    invitees,
    variant: s(i.variant()) as Variant,
    turnTimeoutSecs: i.turnTimeoutSecs(),
    hintsAllowed: i.hintsAllowed(),
    hintsPerPlayer: i.hintsPerPlayer(),
    dropoutTiles: s(i.dropoutTiles()),
    status: s(i.status()),
    gameId: s(i.gameId()),
    expiresAtUnix: Number(i.expiresAtUnix()),
  };
}

export function decodeInvitation(buf: Uint8Array): Invitation {
  return decodeInvitationTable(fb.Invitation.getRootAsInvitation(new ByteBuffer(buf)));
}

export function decodeInvitationList(buf: Uint8Array): Invitation[] {
  const l = fb.InvitationList.getRootAsInvitationList(new ByteBuffer(buf));
  const out: Invitation[] = [];
  for (let i = 0; i < l.invitationsLength(); i++) {
    const inv = l.invitations(i);
    if (inv) out.push(decodeInvitationTable(inv));
  }
  return out;
}

export function decodeGcg(buf: Uint8Array): GcgExport {
  const g = fb.GcgExport.getRootAsGcgExport(new ByteBuffer(buf));
  return { gameId: s(g.gameId()), filename: s(g.filename()), content: s(g.content()) };
}

function emptyGame(): GameView {
  return {
    id: '',
    variant: 'english',
    dictVersion: '',
    status: '',
    players: 0,
    toMove: 0,
    turnTimeoutSecs: 0,
    moveCount: 0,
    endReason: '',
    seats: [],
  };
}

function emptyMove(): MoveRecord {
  return { player: 0, action: '', dir: '', mainRow: 0, mainCol: 0, tiles: [], words: [], count: 0, score: 0, total: 0 };
}