import { customAlphabet } from 'nanoid';
import log4js from 'log4js';
import ExcelJS from 'exceljs';
import config from '../config.js';
import { redisServer } from './redis.js';

const logger = log4js.getLogger('Excel');
const EXCEL_TEMP_KEY_PREFIX = 'excel:temp:';
const EXCEL_TEMP_TTL_SECONDS = 15; // 15 seconds

const excelNanoid = customAlphabet(
  'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789',
  12
);

/**
 * Create a temp token and store export params in Redis.
 * @param {Object} params - { objectType, filter, sort, order }
 * @returns {Promise<{ token: string, url: string }>}
 */
export async function createExcelTempToken(params) {
  const baseUrl = config.app?.urlApi?.replace(/\/$/, '') || '';
  if (!baseUrl) {
    throw new Error('config.app.urlApi is not set; required for Excel temp URLs');
  }
  const objectType = params.objectType || 'Export';
  const now = new Date();
  const datetime =
    now.getFullYear() +
    String(now.getMonth() + 1).padStart(2, '0') +
    String(now.getDate()).padStart(2, '0') +
    String(now.getHours()).padStart(2, '0') +
    String(now.getMinutes()).padStart(2, '0');
  const token = `${objectType}s-${datetime}-${excelNanoid()}`;
  const key = EXCEL_TEMP_KEY_PREFIX + token;
  const stored = { ...params, requestCount: 0 };
  await redisServer.setKey(key, stored, EXCEL_TEMP_TTL_SECONDS);
  logger.debug('Stored excel temp token in Redis:', key);
  const url = `${baseUrl}/excel/temp/${token}.xlsx`;
  return { token, url };
}

/**
 * Get export params for a temp token (supports up to 2 requests; requestCount stored in Redis).
 * @param {string} token
 * @returns {Promise<Object|null>} { objectType, filter, sort, order } or null
 */
export async function getExcelTempParams(token) {
  if (!token) return null;
  const key = EXCEL_TEMP_KEY_PREFIX + token;
  const params = await redisServer.getKey(key);
  if (!params) {
    logger.debug('Excel temp token not found in Redis:', key);
    return null;
  }
  return params;
}

/**
 * Convert a value to an Excel cell-friendly format.
 * Primitives pass through; objects/arrays are stringified; dates are preserved.
 */
function toExcelValue(val) {
  if (val === null || val === undefined) return null;
  if (val instanceof Date) return val;
  if (typeof val === 'number' || typeof val === 'boolean') return val;
  if (typeof val === 'string') return val;
  if (typeof val === 'object') {
    if (Array.isArray(val)) return val.map(toExcelValue).join(', ');
    return JSON.stringify(val);
  }
  return String(val);
}

/**
 * Generate an Excel workbook from tabular data.
 * @param {Array<Object>} data - Array of row objects (keys = column headers)
 * @param {Object} options - Options
 * @param {string} [options.sheetName='Export'] - Worksheet name
 * @param {string[]} [options.columnOrder] - Optional column order (uses Object.keys of first row if not provided)
 * @returns {Promise<Buffer>} Excel file as buffer
 */
export async function generateExcelTable(data, options = {}) {
  const { sheetName = 'Export', columnOrder } = options;

  const workbook = new ExcelJS.Workbook();
  const worksheet = workbook.addWorksheet(sheetName, {
    views: [{ state: 'frozen', ySplit: 1 }],
  });

  if (!data || data.length === 0) {
    const buffer = await workbook.xlsx.writeBuffer();
    return Buffer.from(buffer);
  }

  const keys = columnOrder || Object.keys(data[0]).filter((k) => !k.startsWith('@'));
  const colCount = keys.length;
  const rowCount = data.length + 1;

  const toColLetter = (n) => {
    let s = '';
    while (n >= 0) {
      s = String.fromCharCode((n % 26) + 65) + s;
      n = Math.floor(n / 26) - 1;
    }
    return s;
  };
  const endCol = toColLetter(colCount - 1);

  const tableRows = data.map((row) => keys.map((key) => toExcelValue(row[key])));
  worksheet.addTable({
    name: 'DataTable',
    ref: `A1:${endCol}${rowCount}`,
    headerRow: true,
    style: {
      theme: 'TableStyleLight1',
      showRowStripes: true,
    },
    columns: keys.map((key) => ({ name: key, filterButton: true })),
    rows: tableRows,
  });

  // Auto-fit columns (approximate)
  worksheet.columns.forEach((col, i) => {
    let maxLen = keys[i]?.length || 10;
    worksheet.eachRow({ includeEmpty: false }, (row) => {
      const cell = row.getCell(i + 1);
      const val = cell.value;
      const len = val != null ? String(val).length : 0;
      maxLen = Math.min(Math.max(maxLen, len), 50);
    });
    col.width = maxLen + 2;
  });

  const buffer = await workbook.xlsx.writeBuffer();
  return Buffer.from(buffer);
}

/**
 * Increment request count for a temp token. Returns new count or null if token not found.
 * @param {string} token
 * @returns {Promise<number|null>} New requestCount or null
 */
export async function incrementExcelTempRequestCount(token) {
  if (!token) return null;
  const key = EXCEL_TEMP_KEY_PREFIX + token;
  const data = await redisServer.getKey(key);
  if (!data) return null;
  const requestCount = (data.requestCount ?? 0) + 1;
  const updated = { ...data, requestCount };
  await redisServer.setKey(key, updated, EXCEL_TEMP_TTL_SECONDS);
  logger.debug('Incremented excel temp request count:', key, requestCount);
  return requestCount;
}

export async function deleteExcelTempToken(token) {
  const key = EXCEL_TEMP_KEY_PREFIX + token;
  await redisServer.deleteKey(key);
  logger.debug('Deleted excel temp token from Redis:', key);
}