1 files changed, 270 insertions, 37 deletions

diff --git a/server/index.ts b/server/index.ts
index c9cc6b4..3737105 100644
--- a/server/index.ts
+++ b/server/index.ts
@@ -1,9 +1,10 @@
-import express from 'express';
-import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
-import path from 'path';
-import { songs } from './data/songs';
-import cors from 'cors';
-import dotenv from 'dotenv';
+import express from "express";
+import { createHmac, timingSafeEqual } from "crypto";
+import { songs } from "./data/songs";
+import cors from "cors";
+import dotenv from "dotenv";
+import rateLimit from "express-rate-limit";
+
 dotenv.config();
 
 const app = express();
@@ -11,13 +12,27 @@ app.use(cors());
 app.use(express.json());
 
 const SERVER_PORT = process.env.SERVER_PORT || 3001;
-const SALT = process.env.VITE_HEARDLE_SALT ?? 'changeme';
-const DAILY_SONGS_FILE = path.resolve(
-  process.env.DAILY_SONGS_FILE ?? 'server/data/daily-songs.json',
-);
+const SALT = process.env.VITE_HEARDLE_SALT ?? "changeme";
+const SIGNING_SECRET = process.env.HEARDLE_SIGNING_SECRET ?? SALT;
 
 type Song = (typeof songs)[number];
-type DailySongs = Record<string, Song>;
+
+type GuessResult = "Correct" | "PartiallyCorrect" | "Incorrect" | "Skipped";
+
+type GuessEntry = {
+  song?: {
+    artist: string;
+    name: string;
+  };
+  state: GuessResult;
+};
+
+type SignedState = {
+  date: string;
+  currentTry: number;
+  didGuess: boolean;
+  guesses: GuessEntry[];
+};
 
 function getObfuscationKey(date = getUtcDate()): Buffer {
   return Buffer.from(SALT + date);
@@ -34,6 +49,7 @@ function xorBuffer(data: Buffer, key: Buffer): Buffer {
 function getUtcDate(): string {
   return new Date().toISOString().slice(0, 10);
 }
+
 function hashString(str: string): number {
   let hash = 0;
   for (let i = 0; i < str.length; i++) {
@@ -42,60 +58,277 @@ function hashString(str: string): number {
   return hash;
 }
 
-function readDailySongs(): DailySongs {
-  if (!existsSync(DAILY_SONGS_FILE)) {
-    return {};
+function getDailySong(date: string): Song {
+  const seed = hashString(date);
+  const index = seed % songs.length;
+  return songs[index];
+}
+
+function signValue(prefix: string, value: string): string {
+  return createHmac("sha256", SIGNING_SECRET)
+    .update(`${prefix}:${value}`)
+    .digest("hex");
+}
+
+function safeEqualHex(a: string, b: string): boolean {
+  try {
+    const left = Buffer.from(a, "hex");
+    const right = Buffer.from(b, "hex");
+    if (left.length !== right.length) return false;
+    return timingSafeEqual(left, right);
+  } catch {
+    return false;
   }
+}
 
-  return JSON.parse(readFileSync(DAILY_SONGS_FILE, 'utf8')) as DailySongs;
+function buildSessionToken(date: string): string {
+  const payload = Buffer.from(JSON.stringify({ date }), "utf8").toString("base64url");
+  const sig = signValue("session", payload);
+  return `${payload}.${sig}`;
 }
 
-function writeDailySongs(dailySongs: DailySongs): void {
-  mkdirSync(path.dirname(DAILY_SONGS_FILE), { recursive: true });
-  writeFileSync(DAILY_SONGS_FILE, JSON.stringify(dailySongs, null, 2));
+function verifySessionToken(token: unknown, expectedDate: string): boolean {
+  if (typeof token !== "string") return false;
+  const [payload, sig] = token.split(".");
+  if (!payload || !sig) return false;
+
+  const expectedSig = signValue("session", payload);
+  if (!safeEqualHex(sig, expectedSig)) return false;
+
+  try {
+    const decoded = JSON.parse(Buffer.from(payload, "base64url").toString("utf8")) as {
+      date?: unknown;
+    };
+
+    return typeof decoded.date === "string" && decoded.date === expectedDate;
+  } catch {
+    return false;
+  }
 }
 
-function getDailySong(date: string): Song {
-  const dailySongs = readDailySongs();
-  const savedSong = dailySongs[date];
+function normalizeGuessEntry(entry: unknown): GuessEntry | null {
+  if (!entry || typeof entry !== "object" || Array.isArray(entry)) return null;
 
-  if (savedSong) {
-    return savedSong;
+  const maybeState = (entry as { state?: unknown }).state;
+  if (
+    maybeState !== "Correct" &&
+    maybeState !== "PartiallyCorrect" &&
+    maybeState !== "Incorrect" &&
+    maybeState !== "Skipped"
+  ) {
+    return null;
   }
 
-  const seed = hashString(date);
-  const index = seed % songs.length;
-  const song = songs[index];
-  dailySongs[date] = song;
-  writeDailySongs(dailySongs);
-  return song;
+  const maybeSong = (entry as { song?: unknown }).song;
+
+  if (maybeState === "Skipped") {
+    return { state: "Skipped" };
+  }
+
+  if (!maybeSong || typeof maybeSong !== "object" || Array.isArray(maybeSong)) {
+    return null;
+  }
+
+  const artist = (maybeSong as { artist?: unknown }).artist;
+  const name = (maybeSong as { name?: unknown }).name;
+
+  if (typeof artist !== "string" || typeof name !== "string") {
+    return null;
+  }
+
+  return {
+    song: { artist, name },
+    state: maybeState,
+  };
 }
 
-app.get('/today', (_req, res) => {
+function normalizeSignedState(input: unknown): SignedState | null {
+  if (!input || typeof input !== "object" || Array.isArray(input)) return null;
+
+  const date = (input as { date?: unknown }).date;
+  const currentTryRaw = (input as { currentTry?: unknown }).currentTry;
+  const didGuessRaw = (input as { didGuess?: unknown }).didGuess;
+  const guessesRaw = (input as { guesses?: unknown }).guesses;
+
+  if (typeof date !== "string") return null;
+  if (!Array.isArray(guessesRaw)) return null;
+  if (typeof currentTryRaw !== "number" || !Number.isFinite(currentTryRaw)) return null;
+
+  const currentTry = Math.floor(currentTryRaw);
+  if (currentTry < 0 || currentTry > 6) return null;
+
+  const guesses: GuessEntry[] = [];
+  for (const entry of guessesRaw) {
+    const normalized = normalizeGuessEntry(entry);
+    if (!normalized) return null;
+    guesses.push(normalized);
+  }
+
+  if (guesses.length > 6) return null;
+  if (guesses.length !== currentTry) return null;
+
+  const didGuess = !!didGuessRaw;
+  if (didGuess && !guesses.some((guess) => guess.state === "Correct")) {
+    return null;
+  }
+
+  return {
+    date,
+    currentTry,
+    didGuess,
+    guesses,
+  };
+}
+
+function canonicalState(state: SignedState): string {
+  return JSON.stringify({
+    date: state.date,
+    currentTry: state.currentTry,
+    didGuess: state.didGuess,
+    guesses: state.guesses.map((guess) => ({
+      state: guess.state,
+      song: guess.song
+        ? {
+            artist: guess.song.artist,
+            name: guess.song.name,
+          }
+        : null,
+    })),
+  });
+}
+
+function signState(state: SignedState): string {
+  return signValue("state", canonicalState(state));
+}
+
+function verifyStateSignature(state: SignedState, sig: unknown): boolean {
+  if (typeof sig !== "string") return false;
+  const expectedSig = signState(state);
+  return safeEqualHex(sig, expectedSig);
+}
+
+const guessLimiter = rateLimit({
+  windowMs: 60 * 1000,
+  limit: 30,
+  standardHeaders: true,
+  legacyHeaders: false,
+  message: { error: "Too many requests. Please slow down." },
+});
+
+app.get("/today", (_req, res) => {
   const date = getUtcDate();
   const song = getDailySong(date);
   const obfuscationKey = getObfuscationKey(date);
   const songJson = JSON.stringify(song);
-  const obfuscatedData = xorBuffer(Buffer.from(songJson, 'utf8'), obfuscationKey);
+  const obfuscatedData = xorBuffer(Buffer.from(songJson, "utf8"), obfuscationKey);
+
+  const initialState: SignedState = {
+    date,
+    currentTry: 0,
+    didGuess: false,
+    guesses: [],
+  };
+
   res.json({
     date,
-    data: obfuscatedData.toString('hex'),
+    data: obfuscatedData.toString("hex"),
+    sessionToken: buildSessionToken(date),
+    initialSig: signState(initialState),
+  });
+});
+
+app.post("/guess", guessLimiter, (req, res) => {
+  const today = getUtcDate();
+  const body = req.body as {
+    sessionToken?: unknown;
+    state?: unknown;
+    sig?: unknown;
+    guess?: unknown;
+  };
+
+  if (!verifySessionToken(body.sessionToken, today)) {
+    res.status(401).json({ error: "Invalid session token." });
+    return;
+  }
+
+  const state = normalizeSignedState(body.state);
+  if (!state) {
+    res.status(400).json({ error: "Invalid state payload." });
+    return;
+  }
+
+  if (state.date !== today) {
+    res.status(409).json({ error: "State date is not valid for today." });
+    return;
+  }
+
+  if (!verifyStateSignature(state, body.sig)) {
+    res.status(403).json({ error: "State signature mismatch." });
+    return;
+  }
+
+  if (state.didGuess || state.currentTry >= 6) {
+    res.status(409).json({ error: "Round already finished." });
+    return;
+  }
+
+  let nextGuess: GuessEntry;
+  const guess = body.guess as { artist?: unknown; name?: unknown } | null | undefined;
+
+  if (guess == null) {
+    nextGuess = {
+      state: "Skipped",
+    };
+  } else if (typeof guess.artist === "string" && typeof guess.name === "string") {
+    const solution = getDailySong(today);
+
+    if (guess.artist === solution.artist && guess.name === solution.name) {
+      nextGuess = {
+        song: { artist: guess.artist, name: guess.name },
+        state: "Correct",
+      };
+    } else if (guess.artist === solution.artist) {
+      nextGuess = {
+        song: { artist: guess.artist, name: guess.name },
+        state: "PartiallyCorrect",
+      };
+    } else {
+      nextGuess = {
+        song: { artist: guess.artist, name: guess.name },
+        state: "Incorrect",
+      };
+    }
+  } else {
+    res.status(400).json({ error: "Invalid guess payload." });
+    return;
+  }
+
+  const nextState: SignedState = {
+    date: state.date,
+    currentTry: Math.min(6, state.currentTry + 1),
+    didGuess: state.didGuess || nextGuess.state === "Correct",
+    guesses: [...state.guesses, nextGuess],
+  };
+
+  res.json({
+    state: nextState,
+    sig: signState(nextState),
+    guessState: nextGuess.state,
   });
 });
 
-app.get('/select', (_req, res) => {
+app.get("/select", (_req, res) => {
   const song = songs[Math.floor(Math.random() * songs.length)];
   const obfuscationKey = getObfuscationKey();
   const songJson = JSON.stringify(song);
-  const obfuscatedData = xorBuffer(Buffer.from(songJson, 'utf8'), obfuscationKey);
+  const obfuscatedData = xorBuffer(Buffer.from(songJson, "utf8"), obfuscationKey);
   res.json({
-    data: obfuscatedData.toString('hex'),
+    data: obfuscatedData.toString("hex"),
   });
 });
 
-app.get('/songs', (_req, res) => {
+app.get("/songs", (_req, res) => {
   res.json(songs.map(({ artist, name }) => ({ artist, name })));
 });
 
-
 app.listen(SERVER_PORT, () => console.log(`Server running on :${SERVER_PORT}`));