// TaxPack Background Service Worker
// Handles Gmail OAuth and message passing

import {
  Receipt,
  extractReceiptFromEmail,
  exportToCSV,
  generateTaxSummary,
} from './lib/receipt-utils';

// Store for extracted receipts
const STORAGE_KEY = 'taxpack_receipts';

// Get auth token from Chrome identity API
export async function getAuthToken(interactive: boolean = true): Promise<string | null> {
  try {
    const token = await chrome.identity.getAuthToken({ interactive });
    return token.token ?? null;
  } catch (error) {
    console.error('Auth error:', error);
    return null;
  }
}

// Fetch Gmail messages with receipt indicators
export async function fetchReceiptEmails(token: string, maxResults: number = 50): Promise<any[]> {
  const queries = [
    'subject:receipt',
    'subject:invoice',
    'subject:order confirmation',
    'subject:payment confirmation',
    'subject:purchase confirmation',
    'from:receipts',
    'from:noreply',
  ];

  const allMessages: any[] = [];
  const seenIds = new Set<string>();

  for (const query of queries) {
    try {
      const url = `https://www.googleapis.com/gmail/v1/users/me/messages?q=${encodeURIComponent(query)}&maxResults=${Math.ceil(maxResults / queries.length)}`;
      const response = await fetch(url, {
        headers: { Authorization: `Bearer ${token}` },
      });

      if (!response.ok) {
        if (response.status === 401) {
          // Token expired, try to remove and re-auth
          await chrome.identity.removeCachedAuthToken({ token });
        }
        continue;
      }

      const data = await response.json();
      if (data.messages) {
        for (const msg of data.messages) {
          if (!seenIds.has(msg.id)) {
            seenIds.add(msg.id);
            allMessages.push(msg);
          }
        }
      }
    } catch (error) {
      console.error(`Query failed: ${query}`, error);
    }
  }

  return allMessages.slice(0, maxResults);
}

// Fetch full message details
export async function fetchMessageDetails(token: string, messageId: string): Promise<any | null> {
  try {
    const url = `https://www.googleapis.com/gmail/v1/users/me/messages/${messageId}?format=full`;
    const response = await fetch(url, {
      headers: { Authorization: `Bearer ${token}` },
    });

    if (!response.ok) return null;
    return await response.json();
  } catch (error) {
    console.error('Fetch message error:', error);
    return null;
  }
}

// Save receipts to storage
export async function saveReceipts(receipts: Receipt[]): Promise<void> {
  const existing = await loadReceipts();
  const merged = [...existing];
  const seen = new Set(existing.map(r => r.id));

  for (const receipt of receipts) {
    if (!seen.has(receipt.id)) {
      seen.add(receipt.id);
      merged.push(receipt);
    }
  }

  await chrome.storage.local.set({ [STORAGE_KEY]: merged });
}

// Load receipts from storage
export async function loadReceipts(): Promise<Receipt[]> {
  const result = await chrome.storage.local.get(STORAGE_KEY);
  return result[STORAGE_KEY] || [];
}

// Clear all receipts
export async function clearReceipts(): Promise<void> {
  await chrome.storage.local.remove(STORAGE_KEY);
}

// Listen for messages from popup
chrome.runtime.onMessage.addListener((request, _sender, sendResponse) => {
  (async () => {
    try {
      if (request.action === 'scanGmail') {
        const token = await getAuthToken(request.interactive ?? true);
        if (!token) {
          sendResponse({ success: false, error: 'Authentication failed' });
          return;
        }

        const messages = await fetchReceiptEmails(token, request.maxResults || 50);
        const receipts: Receipt[] = [];

        for (const msg of messages.slice(0, 20)) {
          const details = await fetchMessageDetails(token, msg.id);
          if (details) {
            const receipt = extractReceiptFromEmail(details);
            if (receipt) receipts.push(receipt);
          }
        }

        await saveReceipts(receipts);
        sendResponse({ success: true, count: receipts.length, total: messages.length });
      } else if (request.action === 'getReceipts') {
        const receipts = await loadReceipts();
        sendResponse({ success: true, receipts });
      } else if (request.action === 'clearReceipts') {
        await clearReceipts();
        sendResponse({ success: true });
      } else if (request.action === 'exportCSV') {
        const receipts = await loadReceipts();
        const csv = exportToCSV(receipts);
        sendResponse({ success: true, csv });
      } else if (request.action === 'getSummary') {
        const receipts = await loadReceipts();
        const summary = generateTaxSummary(receipts);
        sendResponse({ success: true, summary, total: receipts.reduce((s, r) => s + r.amount, 0) });
      } else {
        sendResponse({ success: false, error: 'Unknown action' });
      }
    } catch (error) {
      sendResponse({ success: false, error: String(error) });
    }
  })();
  return true; // Keep channel open for async
});