require("dotenv").config();
const express = require("express");
const cors = require("cors");
const fs = require("fs");
const path = require("path");

const app = express();
const PORT = process.env.PORT || 3000;
const CASES_DIR = path.join(__dirname, "cases");
const PROGRESS_DIR = path.join(__dirname, "data", "progress");

// Ensure progress directory exists
if (!fs.existsSync(PROGRESS_DIR)) {
  fs.mkdirSync(PROGRESS_DIR, { recursive: true });
}

// Middleware
app.use(cors());
app.use(express.json());

// Expose public Supabase config to the frontend
app.get("/config.js", (_req, res) => {
  res.type("application/javascript");
  res.send(
    `window.SUPABASE_URL = '${process.env.SUPABASE_URL}'; window.SUPABASE_ANON_KEY = '${process.env.SUPABASE_ANON_KEY}';`,
  );
});

app.use(express.static("public"));

// Verify token by asking Supabase directly — works regardless of JWT algorithm
async function requireAuth(req, res, next) {
  const auth = req.headers.authorization;
  if (!auth || !auth.startsWith("Bearer ")) {
    return res.status(401).json({ error: "Nicht angemeldet" });
  }

  try {
    const response = await fetch(`${process.env.SUPABASE_URL}/auth/v1/user`, {
      headers: {
        Authorization: auth,
        apikey: process.env.SUPABASE_ANON_KEY,
      },
    });

    if (!response.ok) {
      console.error("[auth] Supabase rejected token, status:", response.status);
      return res
        .status(401)
        .json({ error: "Sitzung abgelaufen. Bitte erneut anmelden." });
    }

    const user = await response.json();
    console.log("[auth] OK, userId:", user.id);
    req.userId = user.id;
    next();
  } catch (err) {
    console.error("[auth] Supabase request failed:", err.message);
    res.status(401).json({ error: "Authentifizierung fehlgeschlagen." });
  }
}

// Load task definitions from case files (no user progress mixed in)
function loadCaseTasks() {
  if (!fs.existsSync(CASES_DIR)) return [];
  const allTasks = [];

  fs.readdirSync(CASES_DIR).forEach((file) => {
    if (!file.endsWith(".json")) return;
    try {
      const caseData = JSON.parse(
        fs.readFileSync(path.join(CASES_DIR, file), "utf8"),
      );
      if (Array.isArray(caseData)) {
        caseData.forEach(
          ({ userAnswer, isCorrect, attempts, answerTimestamp, ...task }) => {
            allTasks.push(task);
          },
        );
      } else if (caseData.tasks) {
        caseData.tasks.forEach(
          ({ userAnswer, isCorrect, attempts, answerTimestamp, ...task }) => {
            allTasks.push({
              ...task,
              chapter: caseData.chapter,
              chapterDescription: caseData.description,
            });
          },
        );
      }
    } catch (err) {
      console.error("Fehler beim Laden von", file, ":", err.message);
    }
  });

  return allTasks;
}

// Load/save per-user progress from data/progress/{userId}.json
function loadProgress(userId) {
  const file = path.join(PROGRESS_DIR, `${userId}.json`);
  if (!fs.existsSync(file)) return {};
  try {
    return JSON.parse(fs.readFileSync(file, "utf8"));
  } catch {
    return {};
  }
}

function saveProgress(userId, progress) {
  fs.writeFileSync(
    path.join(PROGRESS_DIR, `${userId}.json`),
    JSON.stringify(progress, null, 2),
  );
}

// API: Get all tasks merged with user's progress
app.get("/api/tasks", requireAuth, (req, res) => {
  const tasks = loadCaseTasks();
  const progress = loadProgress(req.userId);
  res.json({ tasks: tasks.map((task) => ({ ...task, ...progress[task.id] })) });
});

// API: Check answer and save result for the current user
app.post("/api/check-answer", requireAuth, (req, res) => {
  const { taskId, answer } = req.body;

  if (!taskId || answer === undefined) {
    return res
      .status(400)
      .json({ error: "taskId und answer sind erforderlich" });
  }

  const task = loadCaseTasks().find((t) => t.id === taskId);
  if (!task) {
    return res.status(404).json({ error: "Aufgabe nicht gefunden" });
  }

  const userAnswer = parseInt(answer);
  const correctAnswer = parseInt(task.answer);
  const isCorrect = userAnswer === correctAnswer;

  const progress = loadProgress(req.userId);
  progress[taskId] = {
    attempts: (progress[taskId]?.attempts || 0) + 1,
    userAnswer,
    isCorrect,
    answerTimestamp: new Date().toISOString(),
  };
  saveProgress(req.userId, progress);

  res.json({
    correct: isCorrect,
    correctAnswer,
    points: isCorrect ? task.points : 0,
  });
});

app.listen(PORT, () => {
  console.log(`MathQuest Server läuft auf http://localhost:${PORT}`);
});