/**
 * Anonymous 5-message trial — integration tests.
 *
 * Uses `createChatRouter({ streamFn })` with a FAKE streamer, mounted behind
 * `optionalAuth` exactly as app.js wires it, on an ephemeral loopback port.
 * No real AI calls and no Supabase dependency: the anonymous path is pure
 * in-memory.
 *
 * Scenarios:
 *  1. Exactly 5 messages succeed, each emitting session + limit events.
 *  2. The 6th is blocked server-side with 403 SIGNIN_REQUIRED (no AI call).
 *  3. Continuity: echoing chatId continues the same trial; the AI receives
 *     prior turns (context preserved).
 *  4. Refresh / unknown chatId → fresh trial, fresh budget.
 *  5. Forged chatId → fresh trial, never touches sessions, no leak.
 *  6. AI failure still consumes the message and ends the stream cleanly.
 *  7. Chapter validation still applies to anonymous requests.
 *  8. Unauthenticated GET /api/chat/* still requires auth (401).
 */
import test, { before, after } from "node:test";
import assert from "node:assert/strict";
import express from "express";
import { randomUUID } from "node:crypto";
import { createChatRouter } from "../src/routes/chat.js";
import { optionalAuth } from "../src/middleware/supabaseAuth.js";
import { MAX_FREE_MESSAGES } from "../src/services/anonTrial.js";

// ─── fake AI streamer ───
const streamArgs = [];
async function fakeStream(messages, grade, subject, chapter, onChunk, onError, summary) {
  streamArgs.push({ messages, grade, subject, chapter, summary });
  if (fakeStream.mode === "error") {
    onError("boom");
    return "";
  }
  onChunk("Hello ");
  onChunk("world");
  return "Hello world";
}

let server;
let base;

before(async () => {
  const app = express();
  app.use(express.json());
  app.use("/api/chat", optionalAuth, createChatRouter({ streamFn: fakeStream }));
  server = app.listen(0, "127.0.0.1");
  await new Promise((resolve) => server.once("listening", resolve));
  base = `http://127.0.0.1:${server.address().port}`;
});

after(async () => {
  if (server) await new Promise((resolve) => server.close(resolve));
});

async function postChat(body) {
  const res = await fetch(`${base}/api/chat`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(body),
  });
  return res;
}

/** Parse SSE text into {type, payload} events. */
function parseSse(text) {
  return text
    .split("\n\n")
    .filter((block) => block.startsWith("data: "))
    .map((block) => JSON.parse(block.slice(6)));
}

test("anonymous can send exactly 5 messages, each with session+limit events", async () => {
  fakeStream.mode = "ok";
  let trialId = null;
  for (let i = 1; i <= MAX_FREE_MESSAGES; i++) {
    // First message starts a trial; follow-ups echo the trial id as chatId,
    // exactly like the frontend does with activeChat.
    const body = trialId ? { text: `q${i}`, chatId: trialId } : { text: `q${i}` };
    const res = await postChat(body);
    assert.equal(res.status, 200, `message ${i} should be 200`);
    const events = parseSse(await res.text());

    const sessionEvt = events.find((e) => e.type === "session");
    const limitEvt = events.find((e) => e.type === "limit");
    const doneEvt = events.find((e) => e.type === "done");
    assert.ok(sessionEvt?.id, `message ${i} emits a session id`);
    assert.equal(limitEvt?.remaining, MAX_FREE_MESSAGES - i, `remaining after msg ${i}`);
    assert.ok(doneEvt, `message ${i} ends with done`);

    const chunks = events.filter((e) => e.type === "chunk").map((e) => e.content).join("");
    assert.equal(chunks, "Hello world", "chunks streamed");
    if (!trialId) trialId = sessionEvt.id;
    else assert.equal(sessionEvt.id, trialId, "same trial across the session");
  }
});

test("the 6th anonymous message is blocked with 403 SIGNIN_REQUIRED (no AI call)", async () => {
  fakeStream.mode = "ok";
  // First establish a fresh trial and burn the whole budget.
  let trialId = null;
  for (let i = 0; i < MAX_FREE_MESSAGES; i++) {
    const body = trialId ? { text: `burn${i}`, chatId: trialId } : { text: `burn${i}` };
    const res = await postChat(body);
    const events = parseSse(await res.text());
    trialId = events.find((e) => e.type === "session").id;
  }
  // Snapshot AFTER the burn loop: the 6th must not reach the AI at all.
  const beforeCalls = streamArgs.length;
  const res = await postChat({ text: "sixth", chatId: trialId });
  assert.equal(res.status, 403);
  const body = await res.json();
  assert.equal(body.code, "SIGNIN_REQUIRED");
  assert.ok(body.error.toLowerCase().includes("sign in"));
  assert.equal(streamArgs.length, beforeCalls, "no AI call was made for the blocked message");
});

test("continuity: chatId continues the same trial and AI sees prior turns", async () => {
  fakeStream.mode = "ok";
  streamArgs.length = 0;
  const first = parseSse(await (await postChat({ text: "first question" })).text());
  const trialId = first.find((e) => e.type === "session").id;

  const second = parseSse(await (await postChat({ text: "second question", chatId: trialId })).text());
  assert.equal(second.find((e) => e.type === "session").id, trialId, "same trial id");
  assert.equal(second.find((e) => e.type === "limit").remaining, MAX_FREE_MESSAGES - 2);

  // The fake streamer must have received both turns (context preserved).
  const lastCall = streamArgs[streamArgs.length - 1];
  const texts = lastCall.messages.map((m) => m.text);
  assert.ok(texts.includes("first question"), "prior user turn in context");
  assert.ok(texts.includes("second question"), "current user turn in context");
});

test("refresh / unknown chatId starts a fresh trial with a fresh budget", async () => {
  fakeStream.mode = "ok";
  const first = parseSse(await (await postChat({ text: "before refresh" })).text());
  const trialId = first.find((e) => e.type === "session").id;
  assert.equal(first.find((e) => e.type === "limit").remaining, MAX_FREE_MESSAGES - 1);

  // Simulated page refresh: the browser has no state, so no chatId is sent.
  const second = parseSse(await (await postChat({ text: "after refresh" })).text());
  const newId = second.find((e) => e.type === "session").id;
  assert.notEqual(newId, trialId, "new trial id after refresh");
  assert.equal(second.find((e) => e.type === "limit").remaining, MAX_FREE_MESSAGES - 1, "budget reset");
});

test("forged chatId starts a fresh trial and never touches session data", async () => {
  fakeStream.mode = "ok";
  const forged = randomUUID(); // looks like a real session uuid
  const events = parseSse(await (await postChat({ text: "hi", chatId: forged })).text());
  const sessionEvt = events.find((e) => e.type === "session");
  assert.ok(sessionEvt.id, "emits a trial id");
  assert.notEqual(sessionEvt.id, forged, "does not adopt the forged id");
  assert.equal(events.find((e) => e.type === "limit").remaining, MAX_FREE_MESSAGES - 1);
});

test("AI failure consumes the message and ends the stream cleanly with an error event", async () => {
  fakeStream.mode = "error";
  const res = await postChat({ text: "will fail" });
  assert.equal(res.status, 200, "SSE response still 200 (error surfaced in-stream)");
  const events = parseSse(await res.text());
  assert.ok(events.some((e) => e.type === "error"), "error event present");
  assert.ok(!events.some((e) => e.type === "done"), "no done after error");
  // The message was consumed: budget decremented.
  // (Re-establish context by sending one ok message on the same trial.)
  fakeStream.mode = "ok";
  const after = parseSse(await (await postChat({ text: "check", chatId: events.find((e) => e.type === "session").id })).text());
  assert.equal(after.find((e) => e.type === "limit").remaining, MAX_FREE_MESSAGES - 2);
});

test("chapter injection is rejected for anonymous requests too", async () => {
  const res = await postChat({ text: "hello", chapter: "<script>alert(1)</script>" });
  assert.equal(res.status, 400);
  const body = await res.json();
  assert.ok(body.error, "error message present");
});

test("unauthenticated GET /api/chat/* still requires auth", async () => {
  const sessions = await fetch(`${base}/api/chat/sessions`);
  assert.equal(sessions.status, 401, "GET /api/chat/sessions → 401");

  const one = await fetch(`${base}/api/chat/${randomUUID()}`);
  assert.equal(one.status, 401, "GET /api/chat/:id → 401");
});