/**

 * ============================================================================

 * GOOGLE CALENDAR TO DISCORD SYNC (Generic Version)

 * ============================================================================

 * * PURPOSE:

 * This script monitors specific Google Calendars and syncs upcoming events

 * to Discord channels via Webhooks.

 * * FEATURES:

 * 1. Individual Event Posts: Creates a dedicated embed for new events.

 * 2. Edit Detection: If a calendar event changes (time, desc, title), the

 * Discord message updates automatically.

 * 3. Deletion Detection: If an event is deleted from Calendar, it is removed

 * from Discord.

 * 4. Weekly Summary: Generates a single list of all upcoming events for a

 * quick overview.

 * * INSTRUCTIONS:

 * 1. Fill out the CALENDAR_CONFIG array below.

 * 2. Run 'setupTriggers' once to automate the script.

 */

// ============================================================================

// 1. CONFIGURATION

// ============================================================================

const CALENDAR_CONFIG = [

  {

    // Friendly name for logging purposes

    name: "Community Events",

    // The Google Calendar ID (found in Calendar Settings > Integrate Calendar)

    calendarId: "YOUR_CALENDAR_ID_HERE@group.calendar.google.com",

    // The Webhook URL for posting individual event cards

    webhookUrl: "https://discord.com/api/webhooks/...",

    // (Optional) The Webhook URL for posting the weekly summary list.

    // Can be the same as above, or a different channel. Leave empty "" to disable.

    summaryWebhookUrl: "https://discord.com/api/webhooks/...",

    // SYNC SETTINGS

    lookaheadDays: 14,      // How many days into the future to scan for individual cards

    summaryLookahead: 10,   // How many days to include in the summary list

    // DATA STORE KEYS (Unique IDs to save state in Script Properties)

    // Change these if you add a second calendar config block (e.g., "FINGERPRINTS_B")

    fingerprintKey: "FINGERPRINTS_A",

    messageMapKey: "MSG_MAP_A",

    summaryMapKey: "SUMMARY_MSG_ID_A"

  }

];

// ============================================================================

// 2. MAIN EXECUTION FUNCTIONS

// ============================================================================

/**

 * Main entry point. Run this function manually or via trigger.

 * It iterates through every configuration block defined above.

 */

function syncAllCalendars() {

  const props = PropertiesService.getScriptProperties();

  CALENDAR_CONFIG.forEach(config => {

    try {

      console.log(`>>> Starting Sync for: ${config.name}`);

      // 1. Handle Individual Event Cards (Create/Edit/Delete)

      processEventCards(config, props);

      // 2. Handle the Summary List (if configured)

      if (config.summaryWebhookUrl) {

        Utilities.sleep(2000); // Rate limit safety

        generateSummaryList(config, props);

      }

      console.log(`<<< Finished Sync for: ${config.name}`);

    } catch (e) {

      console.error(`CRITICAL ERROR processing ${config.name}: ${e.message} at line ${e.lineNumber}`);

    }

  });

}

/**

 * Handles the logic for individual event embeds.

 * It compares the current state of the calendar against the saved state (PropertiesService).

 */

function processEventCards(config, props) {

  const now = new Date();

  const limitDate = new Date(now.getTime() + (config.lookaheadDays * 24 * 60 * 60 * 1000));

  // Load saved state (Data Persistence)

  // fingerprints: Stores MD5 hashes of events to detect changes.

  // messageMap: Maps Google Event IDs to Discord Message IDs.

  let fingerprints = JSON.parse(props.getProperty(config.fingerprintKey) || "{}");

  let messageMap = JSON.parse(props.getProperty(config.messageMapKey) || "{}");

  // Fetch Events from Google

  const events = Calendar.Events.list(config.calendarId, {

    timeMin: now.toISOString(),

    timeMax: limitDate.toISOString(),

    singleEvents: true,

    orderBy: 'startTime'

  }).items || [];

  console.log(`Found ${events.length} upcoming events in window.`);

  const currentEventIds = events.map(e => e.id);

  // --- STEP 1: CLEANUP (Delete Discord messages for events that no longer exist) ---

  Object.keys(messageMap).forEach(storedEventId => {

    // If the event ID is in our database, but not in the fetch results...

    if (!currentEventIds.includes(storedEventId)) {

      console.log(`Event ${storedEventId} removed or outside window. Deleting from Discord.`);

      deleteFromDiscord(messageMap[storedEventId], config.webhookUrl);

      // Remove from our local state

      delete messageMap[storedEventId];

      delete fingerprints[storedEventId];

      Utilities.sleep(500); // Prevent Discord rate limiting

    }

  });

  // --- STEP 2: PROCESS (Create or Update messages) ---

  events.forEach(event => {

    const eventId = event.id;

    // Generate a "Fingerprint" (MD5 Hash) of the data we care about.

    // If the Title, Location, Time, or Description changes, the hash changes.

    const rawDataString = `${event.summary}|${event.location}|${event.start.dateTime || event.start.date}|${event.description}`;

    const newFingerprint = Utilities.computeDigest(Utilities.DigestAlgorithm.MD5, rawDataString).join("");

    const isNew = !messageMap[eventId];

    const isChanged = fingerprints[eventId] !== newFingerprint;

    // Only hit the Discord API if something is new or changed

    if (isNew || isChanged) {

      console.log(`Processing update for: ${event.summary}`);

      const payload = buildEventEmbed(event, isNew);

      // If it exists, try to Edit (PATCH). If that fails (msg deleted), Post new (POST).

      // If it's new, just Post (POST).

      let discordMessageId;

      if (!isNew && messageMap[eventId]) {

        discordMessageId = editInDiscord(messageMap[eventId], payload, config.webhookUrl);

      } else {

        discordMessageId = postToDiscord(payload, config.webhookUrl);

      }

      // Save the result to our state

      if (discordMessageId) {

        messageMap[eventId] = discordMessageId;

        fingerprints[eventId] = newFingerprint;

      }

      Utilities.sleep(1000); // Rate limit safety

    }

  });

  // Save state back to Script Properties

  props.setProperty(config.fingerprintKey, JSON.stringify(fingerprints));

  props.setProperty(config.messageMapKey, JSON.stringify(messageMap));

}

/**

 * Generates a single (or paged) message summarizing all upcoming events.

 * This deletes the old summary and posts a fresh one every time to ensure

 * it is always at the bottom of the channel.

 */

function generateSummaryList(config, props) {

  console.log(`Generating Summary for ${config.name}...`);

  const now = new Date();

  const limitDate = new Date(now.getTime() + (config.summaryLookahead * 24 * 60 * 60 * 1000));

  // --- Cleanup OLD summary messages ---

  // We store previous summary IDs to delete them so the channel doesn't get cluttered.

  const oldSummaryIds = JSON.parse(props.getProperty(config.summaryMapKey) || "[]");

  if (Array.isArray(oldSummaryIds)) {

    oldSummaryIds.forEach(id => {

      deleteFromDiscord(id, config.summaryWebhookUrl);

      Utilities.sleep(500);

    });

  }

  // Fetch events specifically for the summary window

  const events = Calendar.Events.list(config.calendarId, {

    timeMin: now.toISOString(),

    timeMax: limitDate.toISOString(),

    singleEvents: true,

    orderBy: 'startTime'

  }).items || [];

  if (events.length === 0) return;

  // --- Pagination Logic ---

  // Discord has a 4096 char limit per embed. We split into chunks if needed.

  const MAX_CHARS = 3800;

  let chunks = [];

  let currentChunk = `## 📅 ${config.name}: Next ${config.summaryLookahead} Days\n`;

  let currentDayLabel = "";

  events.forEach(event => {

    // Format Date header (e.g., "Monday, Jan 1")

    const start = new Date(event.start.dateTime || event.start.date);

    const dayLabel = Utilities.formatDate(start, Session.getScriptTimeZone(), "EEEE MMM d");

    let eventEntry = "";

    // Add a header if the day changes

    if (dayLabel !== currentDayLabel) {

      eventEntry += `\n### **${dayLabel}**\n`;

      currentDayLabel = dayLabel;

    }

    // Format Time (e.g., "7:00 PM" or "All Day")

    const timeRange = event.start.dateTime

      ? `\`${Utilities.formatDate(start, Session.getScriptTimeZone(), "h:mm a")}\``

      : "`All Day`";

    // Create the line item

    eventEntry += `* ${timeRange} **${event.summary}**`;

    if(event.location) {

      // clean location (grab text before the first comma to save space)

      const shortLoc = event.location.split(',')[0];

      eventEntry += ` (${shortLoc})`;

    }

    eventEntry += `\n`;

    // Check size limit before adding

    if ((currentChunk.length + eventEntry.length) > MAX_CHARS) {

      chunks.push(currentChunk);

      currentChunk = `## 📅 ${config.name} (Cont.)\n` + eventEntry;

    } else {

      currentChunk += eventEntry;

    }

  });

  // Add the final chunk

  if (currentChunk.length > 0) chunks.push(currentChunk);

  // Post new chunks

  const newMsgIds = [];

  chunks.forEach(chunk => {

    const payload = {

      embeds: [{

        description: chunk,

        color: 3066993 // Green-ish color

      }]

    };

    const res = postToDiscord(payload, config.summaryWebhookUrl);

    if (res) newMsgIds.push(res);

    Utilities.sleep(1000);

  });

  // Save IDs so we can delete them next time

  props.setProperty(config.summaryMapKey, JSON.stringify(newMsgIds));

}

// ============================================================================

// 3. PAYLOAD BUILDER & UTILITIES

// ============================================================================

/**

 * Creates the JSON object for the Discord Embed.

 * Make this function generic to handle any calendar event.

 */

function buildEventEmbed(event, isNew) {

  // Format dates

  const startDate = new Date(event.start.dateTime || event.start.date);

  const dateString = Utilities.formatDate(startDate, Session.getScriptTimeZone(), "EEEE, MMMM d, yyyy");

  const timeString = event.start.dateTime

    ? Utilities.formatDate(startDate, Session.getScriptTimeZone(), "h:mm a")

    : "All Day Event";

  // Clean up the description (Remove HTML tags which Google Calendar adds)

  let description = cleanHtml(event.description || "No description provided.");

  // Truncate description if it exceeds Discord limits (4096 chars)

  if (description.length > 1000) {

    description = description.substring(0, 997) + "...";

  }

  // Define Color (Blue for New, Orange for Updated)

  const color = isNew ? 3447003 : 15158332;

  return {

    embeds: [{

      title: event.summary,

      url: event.htmlLink, // Link back to Google Calendar

      color: color,

      description: description,

      fields: [

        { name: "🗓️ Date", value: dateString, inline: true },

        { name: "⏰ Time", value: timeString, inline: true },

        { name: "📍 Location", value: event.location || "Online / TBD", inline: true }

      ],

      footer: {

        text: isNew ? "🆕 New Event Created" : "✏️ Event Updated"

      },

      timestamp: new Date().toISOString()

    }]

  };

}

/**

 * Helper to strip HTML tags from Google Calendar descriptions

 */

function cleanHtml(text) {

  if (!text) return "";

  // Replace block tags with newlines

  let s = text.replace(/<(br|div|p|li)[^>]*>/gi, "\n");

  // Strip all other tags

  s = s.replace(/<[^>]+>/g, "");

  // Fix common entities

  s = s.replace(/&nbsp;/g, " ")

       .replace(/&amp;/g, "&")

       .replace(/&lt;/g, "<")

       .replace(/&gt;/g, ">");

  return s.trim();

}

// ============================================================================

// 4. DISCORD API HELPERS

// ============================================================================

/**

 * POST a new message to Discord.

 * Returns the Message ID.

 */

function postToDiscord(payload, url) {

  try {

    const options = {

      method: "post",

      contentType: "application/json",

      payload: JSON.stringify(payload),

      muteHttpExceptions: true

    };

    // ?wait=true is required to get the Message Object back (with ID)

    const res = UrlFetchApp.fetch(`${url}?wait=true`, options);

    if (res.getResponseCode() >= 400) {

      console.error(`Discord API Error: ${res.getContentText()}`);

      return null;

    }

    return JSON.parse(res.getContentText()).id;

  } catch (e) {

    console.error("Discord POST failed: " + e.message);

    return null;

  }

}

/**

 * PATCH (Edit) an existing message in Discord.

 * If the message was deleted manually in Discord, this falls back to creating a new one.

 */

function editInDiscord(msgId, payload, url) {

  try {

    const options = {

      method: "patch",

      contentType: "application/json",

      payload: JSON.stringify(payload),

      muteHttpExceptions: true

    };

    const res = UrlFetchApp.fetch(`${url}/messages/${msgId}`, options);

    // If message not found (404), post a new one

    if (res.getResponseCode() === 404) {

      console.warn("Message not found (deleted?), creating new one.");

      return postToDiscord(payload, url);

    }

    return msgId;

  } catch(e) {

    return postToDiscord(payload, url);

  }

}

/**

 * DELETE a message from Discord.

 */

function deleteFromDiscord(msgId, url) {

  if (!msgId) return;

  try {

    UrlFetchApp.fetch(`${url}/messages/${msgId}`, { method: "delete", muteHttpExceptions: true });

  } catch (e) {

    console.warn(`Failed to delete message ${msgId}: ${e.message}`);

  }

}

// ============================================================================

// 5. SETUP & UTILS

// ============================================================================

/**

 * Run this ONCE to authorize the script and set up the hourly trigger.

 */

function setupTriggers() {

  const triggers = ScriptApp.getProjectTriggers();

  triggers.forEach(t => ScriptApp.deleteTrigger(t));

  ScriptApp.newTrigger('syncAllCalendars')

    .timeBased()

    .everyHours(1) // Checks for updates every hour

    .create();

  console.log("✅ Trigger set! Script will run every hour.");

}

/**

 * UTILITY: Run this if you want to wipe the memory and start fresh.

 * Warning: This will cause the script to repost all upcoming events as "New".

 */

function clearScriptMemory() {

  const props = PropertiesService.getScriptProperties();

  props.deleteAllProperties();

  console.log("Memory cleared. Next run will repost all events.");

}