/**
 * The lobby screen — Phase 4 of `docs/architecture/multiplayer.md` (§12 steps 17-20).
 *
 * Everything in `#lobby` (`play.html`) is owned here: the join-secret gate, creating or joining a
 * game by code, and the seating screen up to `Lobby.Start`. `main.ts` calls `runLobby` once, at
 * `start()`, only when there is no stored session to reconnect with — see `main.ts`'s own comment
 * on why a stored `{token, gameId, seat}` skips this module entirely.
 *
 * MIRRORS SERVER TYPES RATHER THAN IMPORTING THEM, same choice `web/session.ts` already made for
 * `Push`: this file must never depend on anything under `src/server/`, even at the type level, since
 * it ships to the browser and the server does not.
 */

import type { GameConfig, PlayerIndex } from '../engine/state.ts';
import { defaultMultiplayerConfig } from './game.ts';

export type LobbyReady = { token: string; gameId: string; seat: PlayerIndex };

type LobbySeat = { kind: 'human'; token: string; displayName: string } | { kind: 'bot' } | null;
type Lobby = {
  gameId: string;
  gameCode: string;
  hostToken: string;
  config: GameConfig;
  seats: LobbySeat[];
  joinOrder: string[];
  createdAt: number;
};
type LobbyPush = { lobby: Lobby; you: PlayerIndex; started: boolean };

/** Per-origin, same reasoning `lobby-and-sessions.md` §1 gives for the session token itself — a
 * secret typed at one address means nothing at another. */
const SECRET_KEY = 'stationmaster-joinsecret';

const $ = <T extends HTMLElement = HTMLElement>(id: string): T => document.getElementById(id) as T;

async function postJson(path: string, body: unknown): Promise<{ status: number; body: Record<string, unknown> }> {
  const res = await fetch(path, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(body),
  });
  return { status: res.status, body: (await res.json()) as Record<string, unknown> };
}

/**
 * Shows `#lobby`, drives it through creating or joining a game and then seating, and calls
 * `onReady` exactly once — the instant `Lobby.Start` fires, from WHICHEVER browser tab started it.
 * Never calls back more than once; the caller is expected to tear this screen down (`main.ts` hides
 * `#lobby` and shows `#gameui`) as its very first action inside `onReady`.
 */
export function runLobby(onReady: (r: LobbyReady) => void): void {
  $('lobby').hidden = false;
  $<HTMLInputElement>('lb-secret').value = localStorage.getItem(SECRET_KEY) ?? '';

  let source: EventSource | null = null;

  function setError(id: string, message: string): void {
    $(id).textContent = message;
  }

  function secret(): string {
    const value = $<HTMLInputElement>('lb-secret').value;
    localStorage.setItem(SECRET_KEY, value);
    return value;
  }

  function renderSeating(lobby: Lobby, you: PlayerIndex, token: string): void {
    $('lb-gamecode').textContent = `— code ${lobby.gameCode}`;
    const isHost = lobby.hostToken === token;

    let html = '';
    for (let seat = 0; seat < lobby.seats.length; seat++) {
      const occupant = lobby.seats[seat] ?? null;
      const isYou = occupant?.kind === 'human' && occupant.token === token;
      const isSeatHost = occupant?.kind === 'human' && occupant.token === lobby.hostToken;
      const who =
        occupant === null
          ? '<span class="dim">— waiting —</span>'
          : occupant.kind === 'bot'
            ? 'Bot'
            : `${occupant.displayName}${isYou ? ' (you)' : ''}${isSeatHost ? ' — host' : ''}`;
      let action = '';
      if (isHost) {
        if (occupant === null) action = `<button class="lb-bot-add" data-seat="${seat}">+ bot</button>`;
        else if (occupant.kind === 'bot') action = `<button class="lb-bot-remove" data-seat="${seat}">remove bot</button>`;
      }
      html += `<div class="lb-seat"><span class="dim">Seat ${seat}</span><span class="who">${who}</span>${action}</div>`;
    }
    $('lb-seats').innerHTML = html;

    for (const btn of Array.from($('lb-seats').querySelectorAll<HTMLButtonElement>('.lb-bot-add'))) {
      btn.onclick = () => void postJson('/api/lobby/bot', { token, seat: Number(btn.dataset['seat']), filled: true });
    }
    for (const btn of Array.from($('lb-seats').querySelectorAll<HTMLButtonElement>('.lb-bot-remove'))) {
      btn.onclick = () => void postJson('/api/lobby/bot', { token, seat: Number(btn.dataset['seat']), filled: false });
    }

    const waiting = lobby.seats.filter((s) => s === null).length;
    const startBtn = $<HTMLButtonElement>('lb-start');
    startBtn.hidden = !isHost;
    startBtn.disabled = waiting > 0;
    $('lb-start-note').textContent = isHost
      ? waiting === 0
        ? ''
        : `Waiting on ${waiting} more ${waiting === 1 ? 'player' : 'players'} — add a bot to any empty chair to start now.`
      : 'Waiting for the host to start the game.';
    startBtn.onclick = () => {
      void postJson('/api/lobby/start', { token }).then(({ status, body }) => {
        if (status !== 200) setError('lb-start-note', String(body['error'] ?? 'could not start'));
      });
    };
  }

  function enterSeating(gameId: string, token: string): void {
    $('lb-choice-section').hidden = true;
    $('lb-seating-section').hidden = false;
    source = new EventSource(`/api/lobby/stream?token=${encodeURIComponent(token)}`);
    source.onmessage = (ev: MessageEvent<string>) => {
      const push = JSON.parse(ev.data) as LobbyPush;
      if (push.started) {
        source?.close();
        onReady({ token, gameId, seat: push.you });
        return;
      }
      renderSeating(push.lobby, push.you, token);
    };
  }

  $<HTMLButtonElement>('lb-create').onclick = () => {
    const displayName = $<HTMLInputElement>('lb-name').value.trim();
    const mode = ($('lb-choice-section').querySelector<HTMLInputElement>('input[name="lb-mode"]:checked')?.value ??
      'competitive') as 'competitive' | 'coop';
    if (displayName === '') {
      setError('lb-create-err', 'enter a display name first');
      return;
    }
    const players = Number($<HTMLSelectElement>('lb-players').value) || 4;
    // The real seat count reaches `defaultMultiplayerConfig`, so the combined-Revenue floor is
    // sized for the table actually being played rather than for an assumed four.
    void postJson('/api/lobby/create', {
      secret: secret(),
      config: defaultMultiplayerConfig(mode, players),
      displayName,
      players,
    }).then(
      ({ status, body }) => {
        if (status !== 200) {
          setError('lb-create-err', String(body['error'] ?? 'could not create the game'));
          return;
        }
        setError('lb-create-err', '');
        enterSeating(body['gameId'] as string, body['token'] as string);
      },
    );
  };

  $<HTMLButtonElement>('lb-join').onclick = () => {
    const displayName = $<HTMLInputElement>('lb-name').value.trim();
    const gameCode = $<HTMLInputElement>('lb-code').value.trim();
    if (displayName === '' || gameCode === '') {
      setError('lb-join-err', 'enter a display name and a game code');
      return;
    }
    void postJson('/api/lobby/join', { secret: secret(), gameCode, displayName }).then(({ status, body }) => {
      if (status !== 200) {
        setError('lb-join-err', String(body['error'] ?? 'could not join that game'));
        return;
      }
      setError('lb-join-err', '');
      enterSeating(body['gameId'] as string, body['token'] as string);
    });
  };
}