import config from '../../config.js';
import log4js from 'log4js';
import { getModelByName } from './model.js';
import { listObjectsOData } from '../../database/odata.js';
import { getFilter } from '../../utils.js';
import {
  generateExcelTable,
  createExcelTempToken,
  getExcelTempParams,
  incrementExcelTempRequestCount,
  deleteExcelTempToken,
} from '../../database/excel.js';

const logger = log4js.getLogger('Excel');
logger.level = config.server.logLevel;

/**
 * Flatten nested objects for Excel display.
 * Objects become "key.subkey: value" or JSON string; arrays become comma-separated.
 */
function flattenForExcel(obj, prefix = '') {
  if (obj === null || obj === undefined) return {};
  if (typeof obj !== 'object') return { [prefix]: obj };
  if (obj instanceof Date) return { [prefix]: obj };
  if (Array.isArray(obj)) {
    const str = obj
      .map((v) => (v && typeof v === 'object' && !(v instanceof Date) ? JSON.stringify(v) : v))
      .join(', ');
    return { [prefix]: str };
  }
  const result = {};
  for (const [k, v] of Object.entries(obj)) {
    const key = prefix ? `${prefix}.${k}` : k;
    if (v !== null && typeof v === 'object' && !(v instanceof Date) && !Array.isArray(v)) {
      Object.assign(result, flattenForExcel(v, key));
    } else {
      result[key] = v;
    }
  }
  return result;
}

/**
 * Convert a row to flat key-value for Excel. Nested objects are flattened.
 */
function rowToFlat(row) {
  const flat = {};
  for (const [key, val] of Object.entries(row)) {
    if (key.startsWith('@')) continue;
    if (val !== null && typeof val === 'object' && !(val instanceof Date) && !Array.isArray(val)) {
      Object.assign(flat, flattenForExcel(val, key));
    } else {
      flat[key] = val;
    }
  }
  return flat;
}

/**
 * Get allowed filter fields for Excel export (reuse OData logic).
 */
function getModelFilterFields(objectType) {
  const base = ['_id'];
  const byType = {
    note: ['parent._id', 'noteType', 'user'],
    notification: ['user'],
    userNotifier: ['user', 'object', 'objectType'],
    printer: ['host'],
    job: ['printer', 'gcodeFile'],
    subJob: ['job'],
    filamentStock: ['filament'],
    partStock: ['part'],
    purchaseOrder: ['vendor'],
    orderItem: ['order._id', 'orderType', 'item._id', 'itemType', 'shipment._id'],
    shipment: ['order._id', 'orderType', 'courierService._id'],
    stockEvent: ['parent._id', 'parentType', 'owner._id', 'ownerType'],
    stockAudit: ['filamentStock._id', 'partStock._id'],
    documentJob: ['documentTemplate', 'documentPrinter', 'object._id', 'objectType'],
    documentTemplate: ['parent._id', 'documentSize._id'],
    salesOrder: ['client'],
    invoice: ['to._id', 'from._id', 'order._id', 'orderType'],
    auditLog: ['parent._id', 'parentType', 'owner._id', 'ownerType'],
    appPassword: ['name', 'user', 'active'],
  };
  const extra = byType[objectType] || [];
  return [...base, ...extra];
}

function parseOrderBy(orderby) {
  if (!orderby || typeof orderby !== 'string') {
    return { sort: 'createdAt', order: 'ascend' };
  }
  const trimmed = orderby.trim();
  const parts = trimmed.split(/\s+/);
  const sort = parts[0] || 'createdAt';
  const dir = (parts[1] || 'asc').toLowerCase();
  const order = dir === 'desc' ? 'descend' : 'ascend';
  return { sort, order };
}

/**
 * Generate Excel file for the given object type.
 * @param {Object} options
 * @param {string} options.objectType - Model type (e.g. 'appPassword', 'user')
 * @param {Object} [options.filter] - Filter object
 * @param {string} [options.sort] - Sort field
 * @param {string} [options.order] - 'ascend' | 'descend'
 * @param {number} [options.limit=10000] - Max rows to export
 * @returns {Promise<{ buffer: Buffer, error?: Object }>}
 */
export async function exportToExcel({ objectType, filter = {}, sort, order, limit = 10000 }) {
  logger.info('[Excel Export] Starting', { objectType, filter, sort, order });
  const entry = getModelByName(objectType);
  if (!entry?.model) {
    logger.warn('[Excel Export] Unknown object type:', objectType);
    return { error: { message: `Unknown object type: ${objectType}` }, code: 404 };
  }

  const orderbyStr = sort ? `${sort} ${order === 'descend' ? 'desc' : 'asc'}` : undefined;
  const { sort: sortField, order: orderDir } = parseOrderBy(orderbyStr);

  const result = await listObjectsOData({
    model: entry.model,
    populate: [],
    page: 1,
    limit,
    filter,
    sort: sortField,
    order: orderDir,
    pagination: true,
    project: undefined,
    count: false,
  });

  if (result?.error) {
    logger.error('[Excel Export] listObjectsOData error:', result.error);
    return { error: result.error, code: result.code || 500 };
  }

  const rows = result?.value || [];
  logger.info('[Excel Export] Rows fetched', { rowCount: rows.length });
  const flatRows = rows.map(rowToFlat);

  const allKeys = new Set();
  flatRows.forEach((r) => Object.keys(r).forEach((k) => allKeys.add(k)));
  const columnOrder = Array.from(allKeys).sort();

  let buffer;
  try {
    buffer = await generateExcelTable(flatRows, {
      sheetName: entry.model.modelName || objectType,
      columnOrder,
    });
    logger.info('[Excel Export] Buffer generated', { bufferLength: buffer?.length });
  } catch (err) {
    logger.error('[Excel Export] generateExcelTable threw:', err?.message, err?.stack);
    return { error: { message: err.message || 'Failed to generate Excel' }, code: 500 };
  }

  return { buffer };
}

/**
 * Route handler for GET /odata/:objectType/excel
 */
export const excelExportRouteHandler = async (req, res) => {
  const objectType = req.params.objectType;
  const allowedFilters = getModelFilterFields(objectType);
  const filter = getFilter(req.query, allowedFilters);
  const { sort, order } = parseOrderBy(req.query.$orderby);

  const result = await exportToExcel({
    objectType,
    filter,
    sort,
    order,
  });

  if (result.error) {
    return res.status(result.code || 500).json(result.error);
  }

  const filename = `${objectType}-export-${new Date().toISOString().slice(0, 10)}.xlsx`;
  res.set('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
  res.set('Content-Disposition', `attachment; filename="${filename}"`);
  res.send(result.buffer);
};

/**
 * Route handler for POST /excel/:objectType/open - creates a temporary URL for opening in Excel.
 * Stores export params in Redis; spreadsheet is generated when Excel fetches the temp URL.
 * Returns { url } - an https URL Excel can fetch (no auth required, one-time use, 5 min expiry).
 */
export const excelOpenRouteHandler = async (req, res) => {
  try {
    const objectType = req.params.objectType;
    logger.info('[Excel Open] POST received', { objectType, query: req.query });
    const allowedFilters = getModelFilterFields(objectType);
    const filter = getFilter(req.query, allowedFilters);
    const { sort, order } = parseOrderBy(req.query.$orderby);

    const entry = getModelByName(objectType);
    if (!entry?.model) {
      logger.warn('[Excel Open] Unknown object type:', objectType);
      return res.status(404).json({ message: `Unknown object type: ${objectType}` });
    }

    const params = { objectType, filter, sort, order };
    logger.info('[Excel Open] Creating temp token with params:', JSON.stringify(params));
    const { token, url } = await createExcelTempToken(params);
    if (!url) {
      logger.error('[Excel Open] createExcelTempToken returned no url');
      return res.status(500).json({ message: 'Failed to create temporary URL' });
    }
    logger.info('[Excel Open] Temp URL created', { objectType, token, url });
    res.json({ url });
  } catch (err) {
    logger.error('[Excel Open] Route error:', err?.message, err?.stack);
    res.status(500).json({ message: err.message || 'Failed to create Excel URL' });
  }
};

/**
 * Route handler for GET /excel/temp/:token - generates and serves temporary Excel file (no auth).
 * Retrieves export params from Redis, generates spreadsheet on demand.
 * Token allows 2 requests before deletion; expires after 5 minutes.
 */
export const excelTempRouteHandler = async (req, res) => {
  const tokenParam = req.params.token || '';
  const token = tokenParam.endsWith('.xlsx') ? tokenParam.slice(0, -5) : tokenParam;
  logger.info('[Excel Temp] GET received', {
    tokenParam,
    token,
    userAgent: req.get('User-Agent'),
    referer: req.get('Referer'),
  });

  const params = await getExcelTempParams(token);
  if (!params) {
    logger.error('[Excel Temp] Token not found or expired', { token, tokenParam });
    return res.status(404).json({ message: 'Link expired or invalid' });
  }

  logger.info('[Excel Temp] Params retrieved from Redis', { objectType: params.objectType });

  const result = await exportToExcel({
    objectType: params.objectType,
    filter: params.filter || {},
    sort: params.sort,
    order: params.order,
  });

  if (result.error) {
    logger.error('[Excel Temp] Export failed', { error: result.error, code: result.code });
    return res.status(result.code || 500).json(result.error);
  }

  const buffer = Buffer.isBuffer(result.buffer) ? result.buffer : Buffer.from(result.buffer);
  const filename = `${token}.xlsx`;
  logger.info('[Excel Temp] Sending buffer', { bufferLength: buffer.length });

  // Strong ETag based on buffer length + timestamp
  const strongETag = `"${buffer.length.toString(16)}-${Date.now()}"`;

  res.setHeader('Content-Length', buffer.length);
  res.setHeader(
    'Content-Type',
    'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
  );
  res.setHeader('Content-Disposition', `attachment; filename="${filename}"`);
  res.setHeader('Access-Control-Expose-Headers', 'Content-Disposition');
  res.setHeader('Cache-Control', 'private, max-age=300');
  res.setHeader('X-Content-Type-Options', 'nosniff');
  res.setHeader('ETag', strongETag);

  // Remove headers that may break Excel
  res.removeHeader('Vary');
  res.removeHeader('Access-Control-Allow-Credentials');
  res.removeHeader('X-Powered-By');

  res.end(buffer);

  if (req.method === 'GET') {
    const requestCount = await incrementExcelTempRequestCount(token);
    if (requestCount !== null && requestCount >= 2) {
      await deleteExcelTempToken(token);
    }
  }
};