// ═══════════════════════════════════════════════════════════
//  MacroScope 伺服器
//  - 對外提供 index.html（前端）
//  - GET /api/macro          整理好的總經資料（後端持金鑰呼叫 FRED）
//  - GET /api/series/:key     單一指標的歷史序列（給「走勢大圖」）
//  - GET /api/score-history   每日健康分數累積歷史
//  資料持久化於 SQLite（data.db）：重啟即時載入、每天累積分數快照
// ═══════════════════════════════════════════════════════════

import 'dotenv/config';
import express from 'express';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

import { GROUPS, INDICATOR_MAP } from './lib/indicators.js';
import { getIndicatorCards, getYieldCurve, MissingKeyError } from './lib/fred.js';
import { computeScore } from './lib/score.js';
import { EVENTS, EPISODES } from './lib/events.js';
import {
  savePayload, loadPayload, saveSeries, getSeries,
  saveScoreSnapshot, getScoreHistory,
} from './lib/db.js';

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const app = express();
const PORT = process.env.PORT || 3000;
const CACHE_TTL_MS = (Number(process.env.CACHE_TTL_SECONDS) || 3600) * 1000;
const hasKey = process.env.FRED_API_KEY && process.env.FRED_API_KEY !== 'your_fred_api_key_here';

// 記憶體快取（開機時會用 DB 內容預先填入）
let cache = { at: 0, payload: null };

async function buildPayload() {
  const [{ cards, seriesHistory, degraded }, yieldCurve] = await Promise.all([
    getIndicatorCards(),
    getYieldCurve(),
  ]);
  const { score, regime, breakdown, signals } = computeScore(cards);
  const groups = GROUPS.map((g) => ({
    key: g.key, title: g.title, titleEn: g.titleEn, icon: g.icon,
    colorKey: g.colorKey, intro: g.intro,
    cards: Object.values(cards).filter((c) => c.group === g.key),
  }));
  const payload = {
    updatedAt: new Date().toISOString(),
    score, regime, breakdown, signals, groups, yieldCurve, degraded,
  };
  return { payload, seriesHistory };
}

// 抓取 → 更新記憶體快取 → 寫入資料庫（序列 + 分數快照）
async function refreshAndCache() {
  const { payload, seriesHistory } = await buildPayload();
  cache = { at: Date.now(), payload };
  try {
    savePayload(payload);
    for (const [key, points] of Object.entries(seriesHistory)) saveSeries(key, points);
    saveScoreSnapshot(payload.score, payload.regime?.label);
  } catch (e) {
    console.warn('寫入資料庫失敗（不影響顯示）：', e.message);
  }
  return payload;
}

app.get('/api/macro', async (req, res) => {
  try {
    const fresh = req.query.fresh === '1';
    if (!fresh && cache.payload && Date.now() - cache.at < CACHE_TTL_MS) {
      return res.json({ ...cache.payload, cached: true });
    }
    const payload = await refreshAndCache();
    res.json({ ...payload, cached: false });
  } catch (err) {
    if (err instanceof MissingKeyError) {
      return res.status(503).json({
        error: 'missing_api_key',
        message: '尚未設定 FRED 金鑰。請複製 .env.example 為 .env 並填入免費的 FRED_API_KEY，再重新啟動伺服器。',
        hint: 'https://fred.stlouisfed.org/docs/api/api_key.html',
      });
    }
    // 若有舊快取，至少先給舊資料
    if (cache.payload) return res.json({ ...cache.payload, cached: true, stale: true });
    console.error('[api/macro] 失敗：', err);
    res.status(502).json({ error: 'fetch_failed', message: '取得資料失敗，請稍後再試。', detail: String(err?.message || err) });
  }
});

// 歷史事件標記 & 危機案例（靜態設定，給走勢標註與「歷史殷鑑」頁用）
app.get('/api/events', (req, res) => res.json({ events: EVENTS, episodes: EPISODES }));

// 單一指標歷史序列（給走勢大圖）
const RANGE_DAYS = { '1m': 30, '6m': 182, '1y': 365, '5y': 1825, '10y': 3650, max: null };
app.get('/api/series/:key', (req, res) => {
  const key = req.params.key;
  const ind = INDICATOR_MAP[key];
  if (!ind) return res.status(404).json({ error: 'unknown_series', message: `查無指標：${key}` });
  const range = RANGE_DAYS[req.query.range] !== undefined ? req.query.range : '1y';
  const days = RANGE_DAYS[range];
  const since = days ? new Date(Date.now() - days * 86400000).toISOString().slice(0, 10) : null;
  const points = getSeries(key, since);
  res.json({
    key, label: ind.label, labelEn: ind.labelEn,
    format: ind.format, decimals: ind.decimals ?? 2,
    inverted: !!ind.inverted, tip: ind.tip, substitute: ind.substitute || null,
    range, points,
  });
});

// 每日健康分數歷史
app.get('/api/score-history', (req, res) => {
  res.json({ points: getScoreHistory() });
});

app.get('/api/health', (req, res) => res.json({ ok: true }));
app.use(express.static(__dirname));

app.listen(PORT, () => {
  console.log(`\nMacroScope 已啟動 → http://localhost:${PORT}\n`);
  if (!hasKey) {
    console.log('提醒：尚未設定 FRED_API_KEY，畫面會顯示設定教學。');
    console.log('申請免費金鑰：https://fred.stlouisfed.org/docs/api/api_key.html\n');
    return;
  }
  // 先用資料庫裡的舊資料填入快取（若有），讓頁面能即時開啟
  const saved = loadPayload();
  if (saved) {
    cache = { at: saved.updatedAt, payload: saved.payload };
    console.log('已從資料庫載入上次資料，頁面可即時開啟。');
  }
  // 背景刷新最新資料（首次或過期時較久，FRED 有流量限制）
  console.log('正在背景抓取最新資料（首次約需 20–40 秒）…');
  const t0 = Date.now();
  refreshAndCache()
    .then((payload) => {
      const ok = payload.groups.reduce((a, g) => a + g.cards.length, 0);
      console.log(`資料就緒：${ok} 個指標，健康分數 ${payload.score}（耗時 ${((Date.now() - t0) / 1000).toFixed(0)} 秒）\n`);
    })
    .catch((err) => console.log('背景抓取失敗（開啟頁面時會再試）：', String(err?.message || err), '\n'));
});