Session 28: Parlay builder, line movement tracker, book comparison — 3 features, zero credits (1623 tests)

src/routes/bookComparison.js

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+'use strict';
+
+/**
+ * /api/books (Session 28)
+ *
+ * Book comparison views over the CACHED odds props — zero odds-api
+ * credits (it never triggers a fetch; it reads what's already cached).
+ *
+ *   GET /api/books/:sport                 → best lines tonight (sorted by savings)
+ *   GET /api/books/:sport/:player/:stat   → book-by-book for one prop
+ *
+ * `?side=over|under` selects which side to optimize (default over).
+ */
+
+const express = require('express');
+const bookComparison = require('../services/bookComparisonService');
+const { cacheGet } = require('../utils/redis');
+
+const router = express.Router();
+
+const MISSION_HEADER = { 'X-VYNDR-Mission': 'Never leave money on the table' };
+
+const SUPPORTED = new Set(['nba', 'wnba', 'mlb', 'soccer', 'nfl', 'nhl']);
+
+// Read cached grouped props for a sport without triggering a fetch.
+// oddsService caches `odds:{sport}:{utcDate}` = { updated_at, props, spreads }.
+async function readCachedProps(sport) {
+  const utcDate = new Date().toISOString().split('T')[0];
+  const cache =
+    (await cacheGet(`odds:${sport}:${utcDate}`)) ??
+    (await cacheGet(`odds:${sport}`));
+  if (!cache) return [];
+  return Array.isArray(cache.props) ? cache.props : [];
+}
+
+router.get('/:sport', async (req, res) => {
+  const sport = String(req.params.sport || '').toLowerCase();
+  if (!SUPPORTED.has(sport)) {
+    return res.status(404).set(MISSION_HEADER).json({ error: `No book comparison for sport: ${sport}` });
+  }
+  const side = req.query.side === 'under' ? 'under' : 'over';
+  const limit = req.query.limit ? Math.max(0, parseInt(req.query.limit, 10) || 0) : 20;
+  try {
+    const props = await readCachedProps(sport);
+    const lines = bookComparison.bestLines(props, { side, limit });
+    return res.set(MISSION_HEADER).json({ sport, side, bestLines: lines, source: 'odds-cache' });
+  } catch (err) {
+    console.error(`[books/${sport}]`, err.message);
+    return res.set(MISSION_HEADER).json({ sport, side, bestLines: [], source: 'odds-cache' });
+  }
+});
+
+router.get('/:sport/:player/:stat', async (req, res) => {
+  const sport = String(req.params.sport || '').toLowerCase();
+  const player = decodeURIComponent(req.params.player);
+  const stat = req.params.stat;
+  const side = req.query.side === 'under' ? 'under' : 'over';
+  try {
+    const props = await readCachedProps(sport);
+    const prop = props.find(
+      (p) => (p.player || '').toLowerCase() === player.toLowerCase() &&
+        (p.stat_type || p.stat || '').toLowerCase() === stat.toLowerCase(),
+    );
+    if (!prop) {
+      return res.status(404).set(MISSION_HEADER).json({ error: 'Prop not found in current slate.' });
+    }
+    const comparison = bookComparison.compareProp(prop, side);
+    if (!comparison) {
+      return res.set(MISSION_HEADER).json({ sport, player, stat, side, books: [], bestBook: null });
+    }
+    return res.set(MISSION_HEADER).json({ sport, ...comparison });
+  } catch (err) {
+    console.error(`[books/${sport}/prop]`, err.message);
+    return res.status(500).set(MISSION_HEADER).json({ error: 'Comparison failed' });
+  }
+});
+
+module.exports = router;