station-master/src/web/replays.ts

/**
 * The replay directory, and the viewer that plays one back.
 *
 * A REPLAY IS A SAVE. `{ seed, history }` — a few hundred bytes — because the engine is
 * deterministic and runs in the browser: re-submitting the same intents against the same seed
 * reconstructs the position exactly. So sharing a game means sharing a small JSON file, not a
 * multi-megabyte page, and a save that would describe an impossible position simply cannot be
 * replayed, because every step goes through `applyIntent`.
 *
 * Static hosting cannot list a directory, so site-hosted replays are enumerated by
 * `replays/manifest.json`, written at build time from whatever is in `public/replays/`.
 */

import { BOARD_CSS, divisionSvg, officeSvg } from '../sim/board-svg.ts';
import { TURNCHART_CSS, turnChartHtml } from '../sim/turnchart.ts';
import { PANEL_CSS, blockedHtml, facilitiesHtml, handHtml, pilesHtml, yardHtml } from './panels.ts';
import { cuesFor } from '../sim/narrate.ts';
import { playCue } from './sound.ts';
import { TOOLTIP_CSS, installTooltips } from './tooltip.ts';
import { narrate } from '../sim/narrate.ts';
import { cardName, trainName } from '../sim/view.ts';
import type { Frame } from '../sim/view.ts';
import { applyIntent } from '../engine/apply.ts';
import { pump } from '../engine/advance.ts';
import { createGame } from '../engine/setup.ts';
import { snapshot } from '../sim/view.ts';
import type { Intent } from '../engine/intents.ts';
import { SOLO_CONFIG } from './game.ts';
import { actingPlayer } from '../engine/state.ts';

type Save = { seed: number; history: Intent[] };
type Entry = { file: string; title: string; note?: string; seed?: number };

const $ = (id: string): HTMLElement => {
  const el = document.getElementById(id);
  if (!el) throw new Error(`missing element: ${id}`);
  return el;
};
const esc = (s: string): string =>
  String(s).replace(/[&<>"]/g, (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' })[c] ?? c);

/** Every position the save passes through, with the lines narrated along the way. */
type Step = {
  frame: Frame;
  lines: { text: string; tone: string }[];
  /** What this step should sound like — from `cuesFor`, the same function the live game uses. */
  cues: string[];
};

/**
 * Rebuild a game from a save, keeping a snapshot at each step.
 *
 * An intent that no longer applies stops the rebuild rather than being forced — better a short
 * replay than one showing a position the rules could not produce.
 */
function rebuild(save: Save): { steps: Step[]; stoppedEarly: boolean } {
  const s = createGame({ id: `replay-${save.seed}`, seed: save.seed, config: SOLO_CONFIG, playerNames: ['player'] });
  const steps: Step[] = [];
  const ctx = {
    cardName: (id: string) => cardName(s, id),
    trainName: (id: string) => trainName(s, id),
    // A player index is not a seat index, so the fallback names no number at all — see `game.ts`.
    playerName: (p: number) => s.players[p]?.name ?? 'another player',
  };
  const push = (events: ReturnType<typeof pump>): void => {
    const lines = events
      .filter((e) => e.type !== 'actorChanged')
      .map((e) => {
        const n = narrate(e, ctx);
        return { text: n.text, tone: n.tone };
      });
    steps.push({ frame: snapshot(s, [], null), lines, cues: cuesFor(events) });
  };

  push(pump(s));
  let stoppedEarly = false;
  for (const intent of save.history) {
    const actor = actingPlayer(s);
    if (actor === null || s.status !== 'active') break;
    const r = applyIntent(s, actor, intent);
    if (!r.ok) {
      stoppedEarly = true;
      break;
    }
    const events = [...r.events, ...pump(s)];
    push(events);
  }
  return { steps, stoppedEarly };
}

// ---------------------------------------------------------------------------
// Viewer
// ---------------------------------------------------------------------------

let steps: Step[] = [];
let at = 0;
let timer: ReturnType<typeof setInterval> | null = null;
/**
 * Sound and auto-hide, matching the playable page and the standalone replay.
 *
 * This viewer is a third place a game gets drawn, and it had drifted: three speeds where the
 * standalone had five, and neither of these. Anything a player learns on one screen should hold on
 * the others.
 */
let soundOn = false;
let districtMode: 'auto' | 'open' | 'closed' = 'auto';
const FOCUS_PHASES = new Set(['localOps', 'loadUnload']);

function show(i: number): void {
  const from = at;
  at = Math.max(0, Math.min(steps.length - 1, i));
  const step = steps[at];
  if (!step) return;
  const f = step.frame;

  // Only a single step FORWARD sounds. Scrubbing across a hundred steps would fire a hundred
  // whistles, and stepping back would sound a Stage ending that is being un-done.
  if (soundOn && at === from + 1) for (const c of step.cues) playCue(c);

  // The live game's turn chart, from the shared renderer: same five phases, same violet "you are
  // here". A replay used to report the Day and phase as two plain strings, so the one thing a player
  // glances at most often looked nothing like it does in play.
  // A replay carries the seat names in the frame's own lines rather than a player table, so the
  // solitaire seat is named directly; a multi-player replay reports the index it has.
  const actorName = f.actor === null ? null : `Player ${f.actor + 1}`;
  // A replay of a multi-player game gets the Fedora too — it is the answer to "why is it asking
  // THEM", which a replay raises exactly as a live game does.
  const superName = f.players.length > 1 ? `Player ${f.superintendent + 1}` : null;
  $('turnchart').innerHTML = turnChartHtml(f, actorName, superName);
  $('vrev').textContent = String(f.revenue);
  $('vpos').textContent = `${at} / ${steps.length - 1}`;
  ($('vscrub') as HTMLInputElement).value = String(at);
  $('vdivision').innerHTML = divisionSvg(f.division);
  $('vgrid').innerHTML = officeSvg(f.cells, f.runningRow, [], [], f.limits);

  // Auto-hide: the district is worth its space during the phases that change it.
  const open = districtMode === 'auto' ? FOCUS_PHASES.has(f.phaseKey) : districtMode === 'open';
  const sec = $('vdistrict');
  if (open) sec.classList.remove('folded');
  else sec.classList.add('folded');
  const cars = f.cells.reduce((n, c) => n + c.cars.length, 0);
  $('vdistrictsummary').textContent =
    `${f.cells.length} cards · ${f.facilities.length} facilities · ${cars} cars standing`;
  $('vdistricttoggle').textContent =
    districtMode === 'auto'
      ? (open ? 'auto-hide: on — click to keep open' : 'auto-hide: on — click to show')
      : districtMode === 'open'
        ? 'always showing — click for auto-hide'
        : 'always hidden — click for auto-hide';

  // A window of history rather than only this step, so a jump lands in context.
  let log = '';
  for (let k = Math.max(0, at - 18); k <= at; k++) {
    for (const l of steps[k]?.lines ?? []) {
      log += `<div class="line t-${l.tone}${k === at ? ' now' : ''}">${esc(l.text)}</div>`;
    }
  }
  // The same side panels the playable page shows, from the same renderers. A replay is the game
  // being watched, so it drops only what asks you to act.
  $('vhand').innerHTML = handHtml(f);
  $('vdepts').innerHTML = pilesHtml(f);
  $('vdivyard').innerHTML = yardHtml(f.yards.division);
  $('vclsyard').innerHTML = yardHtml(f.yards.classification);
  $('vdivtot').textContent = `${f.yards.divisionTotal} cars`;
  $('vclstot').textContent = `${f.yards.classificationTotal} cars`;
  $('vblocked').innerHTML = blockedHtml(f);
  $('vfacs').innerHTML = facilitiesHtml(f);

  $('vlog').innerHTML = log;
  const logEl = $('vlog');
  logEl.scrollTop = logEl.scrollHeight;
}

function openSave(save: Save, title: string): void {
  const built = rebuild(save);
  steps = built.steps;
  $('picker').style.display = 'none';
  $('viewer').style.display = 'block';
  $('vtitle').textContent = title;
  $('vnote').textContent = built.stoppedEarly
    ? 'this save stopped early — an action in it is no longer legal under the current rules'
    : `${steps.length} steps · seed ${save.seed}`;
  const scrub = $('vscrub') as HTMLInputElement;
  scrub.max = String(Math.max(0, steps.length - 1));
  show(0);
}

function parseSave(text: string, from: string): Save | null {
  try {
    const raw = JSON.parse(text) as Partial<Save>;
    if (typeof raw.seed !== 'number' || !Array.isArray(raw.history)) {
      throw new Error('not a Station Master save');
    }
    return { seed: raw.seed, history: raw.history as Intent[] };
  } catch (e) {
    $('perr').textContent = `Could not read ${from}: ${(e as Error).message}`;
    return null;
  }
}

// ---------------------------------------------------------------------------
// Directory
// ---------------------------------------------------------------------------

async function listHosted(): Promise<void> {
  const el = $('hosted');
  try {
    const res = await fetch('./replays/manifest.json', { cache: 'no-cache' });
    if (!res.ok) throw new Error(String(res.status));
    const entries = (await res.json()) as Entry[];
    if (entries.length === 0) {
      el.innerHTML = '<p class="dim">No replays have been published to this site yet.</p>';
      return;
    }
    el.innerHTML = entries
      .map(
        (e, i) =>
          `<button class="entry" data-i="${i}"><b>${esc(e.title)}</b>` +
          (e.note ? `<span class="dim"> — ${esc(e.note)}</span>` : '') +
          `<div class="dim sm">${esc(e.file)}</div></button>`,
      )
      .join('');
    for (const b of Array.from(el.querySelectorAll('button.entry'))) {
      (b as HTMLElement).onclick = async () => {
        const entry = entries[Number((b as HTMLElement).dataset['i'])];
        if (!entry) return;
        const r = await fetch(`./replays/${entry.file}`, { cache: 'no-cache' });
        const save = parseSave(await r.text(), entry.file);
        if (save) openSave(save, entry.title);
      };
    }
  } catch {
    el.innerHTML =
      '<p class="dim">No replay index on this site yet. You can still open a save file from your computer below.</p>';
  }
}

function wire(): void {
  const file = $('file') as HTMLInputElement;
  file.onchange = () => {
    const f = file.files?.[0];
    if (!f) return;
    const reader = new FileReader();
    reader.onload = () => {
      const save = parseSave(String(reader.result), f.name);
      if (save) openSave(save, f.name.replace(/\.json$/i, ''));
    };
    reader.readAsText(f);
  };

  $('vback').onclick = () => show(at - 1);
  $('vfwd').onclick = () => show(at + 1);
  $('vfirst').onclick = () => show(0);
  $('vlast').onclick = () => show(steps.length - 1);
  ($('vscrub') as HTMLInputElement).oninput = (e) => show(Number((e.target as HTMLInputElement).value));
  $('vstage').onclick = () => {
    const now = steps[at]?.frame;
    for (let k = at + 1; k < steps.length; k++) {
      const f = steps[k]!.frame;
      if (f.stage !== now?.stage || f.day !== now?.day) return show(k);
    }
    show(steps.length - 1);
  };
  $('vplay').onclick = () => {
    if (timer) {
      clearInterval(timer);
      timer = null;
      $('vplay').textContent = '▶ play';
      return;
    }
    $('vplay').textContent = '⏸ pause';
    timer = setInterval(() => {
      if (at >= steps.length - 1) {
        clearInterval(timer!);
        timer = null;
        $('vplay').textContent = '▶ play';
        return;
      }
      show(at + 1);
    }, Number(($('vspeed') as HTMLSelectElement).value));
  };
  /**
   * A SPEED CHANGE HAS TO TAKE EFFECT WHILE IT IS PLAYING.
   *
   * The interval is created with whatever the select held at the moment play started, and nothing
   * re-read it — so choosing "extra slow" mid-replay did nothing at all and the pace looked stuck.
   * The standalone replay has always restarted its timer on change; this viewer was missed.
   */
  ($('vspeed') as HTMLSelectElement).onchange = () => {
    if (!timer) return;
    $('vplay').click();
    $('vplay').click();
  };
  $('vdistricttoggle').onclick = () => {
    const f = steps[at]?.frame;
    const open = districtMode === 'auto' ? (f ? FOCUS_PHASES.has(f.phaseKey) : true) : districtMode === 'open';
    districtMode = districtMode === 'auto' ? (open ? 'closed' : 'open') : 'auto';
    show(at);
  };
  $('vsound').onclick = () => {
    soundOn = !soundOn;
    $('vsound').textContent = soundOn ? '\u{1F50A} sound' : '\u{1F507} muted';
    // Confirms the change, and gives the browser the gesture it needs before audio may start.
    if (soundOn) playCue('stage');
  };
  $('vclose').onclick = () => {
    if (timer) clearInterval(timer);
    timer = null;
    $('viewer').style.display = 'none';
    $('picker').style.display = 'block';
  };

  document.onkeydown = (e) => {
    if ($('viewer').style.display === 'none') return;
    if (e.key === 'ArrowRight') show(at + 1);
    else if (e.key === 'ArrowLeft') show(at - 1);
    else if (e.key === ' ') {
      e.preventDefault();
      $('vplay').click();
    }
  };
}

const style = document.createElement('style');
style.textContent = BOARD_CSS + TOOLTIP_CSS + TURNCHART_CSS + PANEL_CSS;
document.head.appendChild(style);
installTooltips();
wire();
void listHosted();