// Server entry: one Express process that serves the built client, the /api REST
// routes, and the /sse stream — all on a single internal port (default 4321).
// In dev, Vite (:5173) proxies /api and /sse here; in Docker/Traefik the whole
// thing is one origin.
import express, { type NextFunction, type Request, type Response } from 'express';
import { randomUUID } from 'node:crypto';
import { existsSync } from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

import { deepClone } from '../shared/protocol';
import type {
  AddActionRequest,
  AddDiplomacyRequest,
  CreateGameRequest,
  RemoveQueueItemRequest,
} from '../shared/protocol';
import type { GameState } from '../shared/types';
import { createLlmClient } from './llm';
import { makeStubLlmClient } from './stub';
import { askAdvisor, queueRoundItem, removeRoundItem, runTurn } from './engine';
import { expandTerritory, loadRegions } from './regions';
import { buildRegionMap } from './map';
import { createPresetStore } from './presets';
import { openDb, type Db } from './db';

const here = fileURLToPath(new URL('.', import.meta.url));

/**
 * Resolve the project root: dev (tsx) runs from <root>/server, the compiled prod
 * bundle runs from <root>/server/dist. Probe a couple of candidates for presets/.
 */
function findRoot(): string {
  const candidates = [
    path.resolve(here, '..'), // dev: <root>  |  prod: <root>/server
    path.resolve(here, '../..'), // prod: <root>
  ];
  for (const c of candidates) {
    if (existsSync(path.join(c, 'presets', 'index.json'))) return c;
  }
  return candidates[0];
}

const root = findRoot();
// Load the sub-region geo once at boot (a graceful no-op, with a warning, when
// the file is missing — the territory model then degrades to whole-country
// ISO_A3 codes). Must run before the first game creation/load.
loadRegions(root);
const presetsDir = path.join(root, 'presets');
const clientDir = process.env.CLIENT_DIST ?? path.join(root, 'dist');
const dataDir = process.env.DATA_DIR ?? path.join(root, 'data');

// PORT wins; HISTORY_API_PORT is the override used by the dev proxy (vite) and
// the e2e config, so honor it as a fallback to keep all three in agreement.
const PORT = parseInt(process.env.PORT ?? process.env.HISTORY_API_PORT ?? '4321', 10);
const presetStore = createPresetStore(presetsDir);
const db: Db = openDb(path.join(dataDir, 'history.db'));
// LLM_STUB=1 → deterministic stub (tests/e2e/dev without a live model).
const useStub = process.env.LLM_STUB === '1';
const llm = useStub ? makeStubLlmClient() : createLlmClient();

const app = express();
app.use(express.json());

// --- SSE client registry (gameId -> set of open responses) ---
const clients = new Map<string, Set<Response>>();

function addClient(res: Response, id: string): void {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache, no-transform',
    Connection: 'keep-alive',
    'Access-Control-Allow-Origin': '*',
  });
  res.write('retry: 2000\n\n');
  let set = clients.get(id);
  if (!set) {
    set = new Set();
    clients.set(id, set);
  }
  set.add(res);
  res.on('close', () => {
    set.delete(res);
    if (set.size === 0) clients.delete(id);
  });
}

function broadcast(id: string, event: string, data: unknown): void {
  const set = clients.get(id);
  if (!set) return;
  const chunk = `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
  for (const r of set) r.write(chunk);
}

// --- Routes ---

app.get('/api/health', (_req, res) => {
  res.json({ ok: true, stub: useStub, port: PORT });
});

app.get('/api/presets', (_req, res) => {
  res.json({ presets: presetStore.listMeta() });
});

app.get('/api/presets/:id', (req, res) => {
  const preset = presetStore.get(req.params.id);
  if (!preset) return res.status(404).json({ error: 'unknown preset' });
  res.json({ preset });
});

app.post('/api/games', (req: Request, res) => {
  const body = req.body as CreateGameRequest | undefined;
  const preset = presetStore.get(body?.presetId ?? '');
  if (!preset) return res.status(400).json({ error: 'unknown preset' });
  const nation = preset.nations.find((n) => n.id === body?.playerNationId);
  if (!nation) return res.status(400).json({ error: 'unknown nation' });
  const state: GameState = {
    id: randomUUID(),
    presetId: preset.id,
    presetTitle: preset.title,
    playerNationId: nation.id,
    turn: 1,
    date: preset.startDate,
    // v0.19: territory is at sub-region granularity — expand each preset
    // nation's ISO_A3 country codes into all their sub-region ids (a no-op that
    // keeps the country codes when the region geo is not loaded).
    nations: Object.fromEntries(
      preset.nations.map((n) => {
        const nation = deepClone(n);
        nation.territory = expandTerritory(nation.territory);
        return [n.id, nation];
      }),
    ),
    events: [],
    pending: [],
    version: 1, // the first saved revision; every later mutation bumps it
  };
  db.save(state);
  res.json({ game: state });
});

// List every saved game (newest-updated first) as a lightweight summary, so the
// home screen can offer to resume prior games. `db.listIds()` is already ordered
// by updated_at DESC.
app.get('/api/games', (_req, res) => {
  const games = db
    .listIds()
    .map((id) => db.load(id))
    .filter((g): g is GameState => g !== null)
    .map((g) => ({
      id: g.id,
      presetId: g.presetId,
      presetTitle: g.presetTitle,
      playerNationId: g.playerNationId,
      turn: g.turn,
      date: g.date,
    }));
  res.json({ games });
});

app.get('/api/games/:id', (req, res) => {
  const game = db.load(req.params.id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  res.json({ game });
});

app.get('/api/games/:id/map', (req, res) => {
  const game = db.load(req.params.id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  res.json({ regions: buildRegionMap(game) });
});

// Delete a saved game entirely. Fast, non-LLM. 404 if it doesn't exist; on
// success broadcast an SSE `error` to any other open tab watching it so it
// returns home (see the `event: error` handling in src/lib/sse.ts).
app.delete('/api/games/:id', (req, res) => {
  const id = req.params.id;
  const removed = db.delete(id);
  if (!removed) return res.status(404).json({ error: 'game not found' });
  broadcast(id, 'error', { message: 'game deleted' });
  res.json({ deleted: true });
});

// Queue a free-text player action onto the pending round. No LLM call and no
// turn advance — the round is only committed (in one turn) by "Jump forward".
app.post('/api/games/:id/action', (req, res) => {
  const id = req.params.id;
  const game = db.load(id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  const text = (req.body as AddActionRequest | undefined)?.text?.trim();
  if (!text) return res.status(400).json({ error: 'empty action' });
  const next = queueRoundItem(game, { kind: 'action', text });
  db.save(next);
  broadcast(id, 'state', { state: next });
  res.json({ game: next });
});

// Queue a diplomatic message to a target nation onto the pending round. No LLM
// call and no advance.
app.post('/api/games/:id/diplomacy', (req, res) => {
  const id = req.params.id;
  const game = db.load(id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  const body = (req.body ?? {}) as AddDiplomacyRequest;
  const message = body.message?.trim();
  if (!body.to || !message) return res.status(400).json({ error: 'empty message' });
  const next = queueRoundItem(game, { kind: 'diplomacy', to: body.to, text: message });
  db.save(next);
  broadcast(id, 'state', { state: next });
  res.json({ game: next });
});

// Remove one item from the pending round, by its index in `game.pending`. No
// LLM call, no turn advance — same fast save → broadcast → respond order as the
// add routes above. The mutated state bumps `version`, so clients (which apply
// states "never go backwards") always reconcile to it.
app.post('/api/games/:id/queue/remove', (req, res) => {
  const id = req.params.id;
  const game = db.load(id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  const index = (req.body as RemoveQueueItemRequest | undefined)?.index;
  const next = removeRoundItem(game, index);
  if (!next) return res.status(400).json({ error: 'invalid queue index' });
  db.save(next);
  broadcast(id, 'state', { state: next });
  res.json({ game: next });
});

// Jump forward: commit the whole pending round (or an empty one) to the model
// in a single turn. applyTurnResult clears the pending queue on the returned
// state. 404 for not-found/preset-missing; 502 for LLM/model (transport) errors.
app.post('/api/games/:id/jump', async (req, res) => {
  const id = req.params.id;
  const game = db.load(id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  const preset = presetStore.get(game.presetId);
  if (!preset) return res.status(404).json({ error: 'preset_missing' });
  try {
    const { state, result } = await runTurn({
      llm,
      preset,
      state: game,
      items: game.pending,
    });
    db.save(state);
    broadcast(id, 'turn', { state, result });
    res.json({ state, result });
  } catch (e) {
    const msg = e instanceof Error ? e.message : String(e);
    res.status(502).json({ error: `jump failed: ${msg}` });
  }
});

app.post('/api/games/:id/advisor', async (req, res) => {
  const game = db.load(req.params.id);
  if (!game) return res.status(404).json({ error: 'game not found' });
  const prompt = (req.body as { prompt?: string } | undefined)?.prompt;
  try {
    const suggestions = await askAdvisor(llm, game, prompt);
    res.json({ suggestions });
  } catch {
    // Live model down → degrade gracefully with a canned idea list.
    res.json({
      suggestions: [
        'Rearm quietly to buy time while the great powers watch.',
        'Court a neutral neighbor for a defensive pact.',
        'Expand industry to sustain a longer conflict.',
      ],
    });
  }
});

// --- SSE stream ---
app.get('/sse/:id', (req, res) => {
  const id = req.params.id;
  const game = db.load(id);
  addClient(res, id);
  if (game) {
    res.write(`event: state\ndata: ${JSON.stringify({ state: game })}\n\n`);
  } else {
    res.write(`event: error\ndata: ${JSON.stringify({ message: 'game not found' })}\n\n`);
  }
});

// --- Static client + SPA fallback ---
if (existsSync(clientDir)) {
  app.use(express.static(clientDir));
  app.get('*', (req, res) => {
    if (req.path.startsWith('/api/') || req.path.startsWith('/sse/')) {
      return res.status(404).send('not found');
    }
    res.sendFile(path.join(clientDir, 'index.html'));
  });
}

// Unhandled async errors shouldn't take down the process.
app.use((err: unknown, _req: Request, res: Response, next: NextFunction) => {
  console.error('[history] unhandled error:', err);
  if (!res.headersSent) res.status(500).json({ error: 'internal error' });
  next();
});

app.listen(PORT, () => {
  console.log(
    `[history] listening on :${PORT} (llm=${useStub ? 'STUB' : 'live'}) client=${existsSync(clientDir) ? 'found' : 'absent'}`,
  );
});

// Exported for tests (createApp is implicit via app; here we just expose handles).
export { app, db, llm };