/* @OnlyCurrentDoc */
/* Author: digitalinspiration.com */

const TRANSACTION_TYPE = 'T0001';

// Enter your own PayPal Client ID and Client Secret key
const PAYPAL_CLIENT_ID = '<YOUR_PAYPAL_CLIENT_ID>';
const PAYPAL_CLIENT_SECRET = '<YOUR_PAYPAL_CLIENT_SECRET>';

// Enter start and end dates in the format YYYY-MM-DD
const START_DATE = '2022-03-01';
const END_DATE = '2022-03-15';

// Generate the PayPal access token
const getPayPalAccessToken_ = () => {
  const credentials = `${PAYPAL_CLIENT_ID}:${PAYPAL_CLIENT_SECRET}`;
  const headers = {
    Authorization: ` Basic ${Utilities.base64Encode(credentials)}`,
    Accept: 'application/json',
    'Content-Type': 'application/json',
    'Accept-Language': 'en_US',
  };

  const options = {
    method: 'POST',
    headers,
    contentType: 'application/x-www-form-urlencoded',
    payload: { grant_type: 'client_credentials' },
  };

  const request = UrlFetchApp.fetch('https://api.paypal.com/v1/oauth2/token', options);
  const { access_token } = JSON.parse(request);

  return access_token;
};

// Append the query parameters to the PayPal API URL
const buildAPIUrl_ = (queryParams) => {
  const baseUrl = [`https://api-m.paypal.com/v1/reporting/transactions`];
  Object.entries(queryParams).forEach(([key, value], index) => {
    const prefix = index === 0 ? '?' : '&';
    baseUrl.push(`${prefix}${key}=${value}`);
  });
  return baseUrl.join('');
};

// Fetch the list of PayPal transaction
const fetchTransactionBatchFromPayPal = (queryParams) => {
  const options = {
    headers: {
      Authorization: `Bearer ${getPayPalAccessToken_()}`,
      'Content-Type': 'application/json',
    },
  };

  const request = UrlFetchApp.fetch(buildAPIUrl_(queryParams), options);
  const { transaction_details, total_pages } = JSON.parse(request);
  return { transaction_details, total_pages };
};

// Extract the transaction details including the transaction ID,
// donation amount, transaction date and buyer's email and country code
const parsePayPalTransaction_ = ({ transaction_info, payer_info }) => [
  transaction_info.transaction_id,
  new Date(transaction_info.transaction_initiation_date),
  transaction_info.transaction_amount?.value,
  transaction_info.transaction_note || transaction_info.transaction_subject || '',
  payer_info?.payer_name?.alternate_full_name,
  payer_info?.email_address,
  payer_info?.country_code,
];

const fetchPayPalTransactions_ = () => {
  const startDate = new Date(START_DATE);
  const endDate = new Date(END_DATE);
  startDate.setHours(0, 0, 0, 0);
  endDate.setHours(23, 59, 59, 999);

  const transactions = [];

  const params = {
    start_date: startDate.toISOString(),
    end_date: endDate.toISOString(),
    page_size: 100,
    transaction_type: TRANSACTION_TYPE,
    fields: 'transaction_info,payer_info',
  };

  for (let page = 1, hasMore = true; hasMore; page += 1) {
    const response = fetchTransactionBatchFromPayPal({ ...params, page });
    const { transaction_details = [], total_pages } = response;
    transaction_details.map(parsePayPalTransaction_).forEach((e) => transactions.push(e));
    hasMore = total_pages && total_pages > page;
  }

  return transactions;
};

// Import the transactions from PayPal and write them to the active Google Sheet
const importTransactionsToGoogleSheet = () => {
  const transactions = fetchPayPalTransactions_();
  const { length } = transactions;
  if (length > 0) {
    const sheet = SpreadsheetApp.getActiveSheet();
    sheet.getRange(1, 1, length, transactions[0].length).setValues(transactions);
    const status = `Imported ${length} PayPal transactions into Google Sheets`;
    SpreadsheetApp.getActiveSpreadsheet().toast(status);
  }
};