1 files changed, 123 insertions, 0 deletions
diff --git a/server/daily.ts b/server/daily.ts
new file mode 100644
index 0000000..35350f7
--- /dev/null
+++ b/server/daily.ts
@@ -0,0 +1,123 @@
+import { Router } from "express";
+import rateLimit from "express-rate-limit";
+import {
+  buildSessionToken,
+  getDailySong,
+  getUtcDate,
+  GuessEntry,
+  normalizeSignedState,
+  obfuscateSong,
+  SignedState,
+  signState,
+  verifySessionToken,
+  verifyStateSignature,
+} from "./shared";
+
+export const dailyRouter = Router();
+
+const guessLimiter = rateLimit({
+  windowMs: 60 * 1000,
+  limit: 30,
+  standardHeaders: true,
+  legacyHeaders: false,
+  message: { error: "Too many requests. Please slow down." },
+});
+
+dailyRouter.get("/today", (_req, res) => {
+  const date = getUtcDate();
+  const song = getDailySong(date);
+
+  const initialState: SignedState = {
+    date,
+    currentTry: 0,
+    didGuess: false,
+    guesses: [],
+  };
+
+  res.json({
+    date,
+    data: obfuscateSong(song, date),
+    sessionToken: buildSessionToken(date),
+    initialSig: signState(initialState),
+  });
+});
+
+dailyRouter.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,
+  });
+});