require("dotenv").config();
const express = require("express");
const fs = require("fs");
const msal = require("@azure/msal-node");
const axios = require("axios");

const app = express();
const port = 3000;
const cachePath = "./cache.json";

const msalConfig = {
  auth: {
    clientId: process.env.CLIENT_ID,
    authority: "https://login.microsoftonline.com/common",
    clientSecret: process.env.CLIENT_SECRET,
  },
};

const pca = new msal.ConfidentialClientApplication(msalConfig);
const scopes = ["offline_access", "Calendars.ReadWrite"];
const redirectUri = "http://localhost:3000/redirect";

function loadTokenCache() {
  if (fs.existsSync(cachePath)) {
    const cache = fs.readFileSync(cachePath, "utf-8");
    pca.getTokenCache().deserialize(cache);
  }
}

function saveTokenCache() {
  const cache = pca.getTokenCache().serialize();
  fs.writeFileSync(cachePath, cache);
}

async function acquireTokenSilently(scopes) {
  loadTokenCache();
  const accounts = await pca.getTokenCache().getAllAccounts();
  const account = accounts[0];
  if (!account) throw new Error("No account found in token cache");

  const result = await pca.acquireTokenSilent({ account, scopes });
  return result.accessToken;
}

async function getCalendarEvents(accessToken) {
  try {
    const response = await axios.get(
      "https://graph.microsoft.com/v1.0/me/events?$select=subject,body,bodyPreview,organizer,attendees,start,end,location",
      {
        headers: {
          Authorization: `Bearer ${accessToken}`,
          "Content-Type": "application/json",
        },
      }
    );
    return response.data;
  } catch (error) {
    console.error("Error fetching calendar events:", error?.response?.status, error?.response?.statusText);
    return { error: "Failed to fetch calendar events" };
  }
}

app.get("/", async (req, res) => {
  loadTokenCache();
  const authCodeUrlParams = {
    scopes,
    redirectUri,
    prompt: "select_account",
  };
  const url = await pca.getAuthCodeUrl(authCodeUrlParams);
  res.redirect(url);
});

app.get("/redirect", async (req, res) => {
  const tokenRequest = {
    code: req.query.code,
    scopes,
    redirectUri,
  };

  try {
    const result = await pca.acquireTokenByCode(tokenRequest);
    saveTokenCache();

    const accessToken = await acquireTokenSilently(scopes); // uses refresh token silently

    const rawCache = pca.getTokenCache().serialize();
    const parsedCache = JSON.parse(rawCache);
    const rtEntry = parsedCache.RefreshToken;
    const rtKey = Object.keys(rtEntry)[0];
    const refreshToken = rtEntry[rtKey]?.secret || "Not found";

    console.log("\nAccess Token:\n", accessToken);
    console.log("\nRefresh Token:\n", refreshToken);

    const newEvent = {
      subject: "Test event created in MS account",
      body: {
        contentType: "HTML",
        content: "Test event for repro purpose.",
      },
      start: {
        dateTime: new Date(Date.now() + 3600000).toISOString(), // 1 hour from now
        timeZone: "UTC",
      },
      end: {
        dateTime: new Date(Date.now() + 7200000).toISOString(), // 2 hours from now
        timeZone: "UTC",
      },
      attendees: [],
    };

    const eventResponse = await axios.post(
      "https://graph.microsoft.com/v1.0/me/events",
      newEvent,
      {
        headers: {
          Authorization: `Bearer ${accessToken}`,
          "Content-Type": "application/json",
        },
      }
    );

    console.log("\nCreated Event:\n", JSON.stringify(eventResponse.data, null, 2));

    const calendarData = await getCalendarEvents(accessToken);
    console.log("\nCalendar Events:\n", JSON.stringify(calendarData, null, 2));

    res.send(`
      <h2>Created Event</h2>
      <pre>${JSON.stringify(eventResponse.data, null, 2)}</pre>

      <h2>Calendar Events</h2>
      <pre>${JSON.stringify(calendarData, null, 2)}</pre>
    `);
  } catch (err) {
    console.error("Redirect error:", err.response?.data || err.message);
    res.status(500).send("Something went wrong while processing token or calendar operation.");
  }
});

app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`);
});