add: elo data model and static rankings page

scripts/lib/elo.js

@@ -0,0 +1,139 @@
+const fs = require("fs");
+const path = require("path");
+
+const { repoRoot } = require("./meals");
+
+const eloPath = path.join(repoRoot, "data", "elo.json");
+
+function validateEloData(eloData) {
+  if (!eloData || typeof eloData !== "object" || Array.isArray(eloData)) {
+    throw new Error("data/elo.json must contain an object");
+  }
+
+  for (const field of ["defaultRating", "kFactor"]) {
+    if (
+      typeof eloData[field] !== "number" ||
+      !Number.isFinite(eloData[field]) ||
+      eloData[field] <= 0
+    ) {
+      throw new Error(`data/elo.json "${field}" must be a positive number`);
+    }
+  }
+
+  if (!Array.isArray(eloData.entries)) {
+    throw new Error('data/elo.json "entries" must be an array');
+  }
+
+  const ids = new Set();
+
+  for (const [index, entry] of eloData.entries.entries()) {
+    if (!entry || typeof entry !== "object" || Array.isArray(entry)) {
+      throw new Error(`Elo entry ${index} must be an object`);
+    }
+
+    if (typeof entry.id !== "string" || !/^\d+$/.test(entry.id)) {
+      throw new Error(`Elo entry ${index} has an invalid id`);
+    }
+
+    if (ids.has(entry.id)) {
+      throw new Error(`Duplicate Elo entry id "${entry.id}" found in data/elo.json`);
+    }
+
+    ids.add(entry.id);
+
+    if (
+      typeof entry.rating !== "number" ||
+      !Number.isFinite(entry.rating) ||
+      entry.rating <= 0
+    ) {
+      throw new Error(`Elo entry ${index} must have a positive numeric rating`);
+    }
+
+    for (const field of ["wins", "losses"]) {
+      if (!Number.isInteger(entry[field]) || entry[field] < 0) {
+        throw new Error(`Elo entry ${index} field "${field}" must be a non-negative integer`);
+      }
+    }
+  }
+}
+
+function loadEloData() {
+  const eloData = JSON.parse(fs.readFileSync(eloPath, "utf8"));
+
+  validateEloData(eloData);
+
+  return eloData;
+}
+
+function saveEloData(eloData) {
+  validateEloData(eloData);
+  fs.writeFileSync(eloPath, `${JSON.stringify(eloData, null, 2)}\n`);
+}
+
+function createDefaultEntry(id, defaultRating) {
+  return {
+    id,
+    rating: defaultRating,
+    wins: 0,
+    losses: 0,
+  };
+}
+
+function syncEloWithMeals(meals) {
+  const eloData = loadEloData();
+  const entryById = new Map(eloData.entries.map((entry) => [entry.id, entry]));
+  const syncedData = {
+    ...eloData,
+    entries: meals.map((meal) => {
+      const existingEntry = entryById.get(meal.id);
+      return existingEntry
+        ? { ...existingEntry }
+        : createDefaultEntry(meal.id, eloData.defaultRating);
+    }),
+  };
+
+  if (JSON.stringify(syncedData) !== JSON.stringify(eloData)) {
+    saveEloData(syncedData);
+  }
+
+  return syncedData;
+}
+
+function compareRankedMeals(left, right) {
+  if (right.rating !== left.rating) {
+    return right.rating - left.rating;
+  }
+
+  if (right.matches !== left.matches) {
+    return right.matches - left.matches;
+  }
+
+  return Number.parseInt(left.id, 10) - Number.parseInt(right.id, 10);
+}
+
+function getRankedMeals(meals, eloData) {
+  const entryById = new Map(eloData.entries.map((entry) => [entry.id, entry]));
+
+  return meals
+    .map((meal) => {
+      const entry = entryById.get(meal.id) || createDefaultEntry(meal.id, eloData.defaultRating);
+      const matches = entry.wins + entry.losses;
+
+      return {
+        ...meal,
+        rating: entry.rating,
+        wins: entry.wins,
+        losses: entry.losses,
+        matches,
+      };
+    })
+    .sort(compareRankedMeals);
+}
+
+module.exports = {
+  eloPath,
+  getRankedMeals,
+  loadEloData,
+  saveEloData,
+  syncEloWithMeals,
+};