/**
 * Geopolitical Risk (GPR) Index client.
 *
 * Source: Dario Caldara and Matteo Iacoviello (2022),
 * "Measuring Geopolitical Risk," American Economic Review.
 * https://www.matteoiacoviello.com/gpr.htm
 *
 * Data is a daily Excel file (CC-BY-4.0), updated daily.
 * We download it, parse with xlsx, and return CommodityPricePoint[].
 */

import { type CommodityPricePoint } from '@/lib/schemas/commodities.js';
import * as XLSX from 'xlsx';

const GPR_DAILY_URL = 'https://www.matteoiacoviello.com/gpr_files/data_gpr_daily_recent.xls';

const FETCH_TIMEOUT_MS = 30_000;

/**
 * Fetch and parse the daily GPR index.
 * Returns CommodityPricePoint[] with commodity='gpr_daily'.
 */
export async function getGeopoliticalRiskIndex(
  options: {
    start?: string;
    end?: string;
  } = {},
): Promise<CommodityPricePoint[]> {
  const controller = new AbortController();
  const timeoutId = setTimeout(() => controller.abort(), FETCH_TIMEOUT_MS);

  let buffer: ArrayBuffer;
  try {
    const response = await fetch(GPR_DAILY_URL, { signal: controller.signal });
    if (!response.ok) {
      throw new Error(`GPR download failed: HTTP ${response.status}`);
    }
    buffer = await response.arrayBuffer();
  } finally {
    clearTimeout(timeoutId);
  }

  const workbook = XLSX.read(buffer, { type: 'array' });
  const sheet = workbook.Sheets[workbook.SheetNames[0]!];
  if (!sheet) {
    throw new Error('GPR Excel file has no sheets');
  }

  const rows = XLSX.utils.sheet_to_json<Record<string, unknown>>(sheet);

  const startDate = options.start ? new Date(`${options.start}T00:00:00Z`) : null;
  const endDate = options.end ? new Date(`${options.end}T00:00:00Z`) : null;

  const results: CommodityPricePoint[] = [];

  for (const row of rows) {
    // The date column may be named "date" or "DATE" depending on the file version
    const dateVal = row['date'] ?? row['DATE'];
    const gprVal = row['GPRD'] ?? row['GPR_Daily'] ?? row['gprd'];

    if (dateVal === undefined || gprVal === undefined) continue;

    let timestamp: Date;
    if (typeof dateVal === 'number') {
      // Excel serial date number
      timestamp = excelDateToUTC(dateVal);
    } else if (typeof dateVal === 'string') {
      timestamp = new Date(`${dateVal}T00:00:00Z`);
    } else {
      continue;
    }

    if (isNaN(timestamp.getTime())) continue;

    const price = Number(gprVal);
    if (isNaN(price)) continue;

    if (startDate && timestamp < startDate) continue;
    if (endDate && timestamp > endDate) continue;

    results.push({
      timestamp,
      commodity: 'gpr_daily',
      price,
      unit: 'Index',
      source: 'GPR',
    });
  }

  return results;
}

/** Convert Excel serial date number to UTC Date */
function excelDateToUTC(serial: number): Date {
  // Excel epoch is 1900-01-01, but has a leap year bug (day 60 = Feb 29, 1900 which didn't exist)
  const utcDays = serial - 25569; // Days since Unix epoch
  return new Date(utcDays * 86400 * 1000);
}