import { DateTime } from "luxon";
import { sdkLogger as logger } from "../services/reporting-service/logger.js";
import { getCachedTimezoneName } from "../services/mm-api-service/company-info.js";

/**
 * Retrieves the ERP timezone name that should have been cached during initialization.
 * @throws Error when the timezone cache has not been populated.
 */
export function getERPTimezone(): string {
  const timezone = getCachedTimezoneName();
  if (!timezone) {
    throw new Error(
      "ERP timezone is not cached. Run getTimezoneOffsetAndPersist() to populate it."
    );
  }
  return timezone;
}

/**
 * Converts a UTC ISO-8601 datetime string to the ERP's local timezone (also ISO-8601).
 * @param utcDateTime ISO-8601 datetime string representing UTC time.
 * @param timezone Optional timezone override; defaults to the cached ERP timezone.
 * @returns ISO-8601 string in the ERP timezone.
 */
export function convertUtcDateTimeToErpLocal(
  utcDateTime: string,
  timezone?: string
): string {
  if (!utcDateTime) {
    throw new Error("convertUtcDateTimeToErpLocal requires a non-empty UTC datetime string");
  }
  try {
    const targetZone = timezone ?? getERPTimezone();
    const parsedUtc = DateTime.fromISO(utcDateTime, { zone: "utc" });
    if (!parsedUtc.isValid) {
      throw new Error(
        `Invalid UTC datetime "${utcDateTime}": ${parsedUtc.invalidReason}`
      );
    }

    const localized = parsedUtc.setZone(targetZone);
    if (!localized.isValid) {
      throw new Error(
        `Unable to convert UTC datetime "${utcDateTime}" to target zone "${targetZone}": ${localized.invalidReason}`
      );
    }

    return localized.toISO();
  } catch (error) {
    logger.error("convertUtcDateTimeToErpLocal: Failed to convert datetime", {
      utcDateTime,
      error,
    });
    throw new Error(
      "Failed to convert UTC datetime to ERP local timezone. See logs for details."
    );
  }
}

/**
 * Converts an ERP-local ISO-8601 datetime string to UTC (still ISO-8601).
 * @param localDateTime ISO-8601 datetime string representing ERP local time.
 * @param timezone Optional timezone override; defaults to the cached ERP timezone.
 * @returns ISO-8601 string in UTC.
 */
export function convertErpLocalDateTimeToUtc(
  localDateTime: string,
  timezone?: string
): string {
  if (!localDateTime) {
    throw new Error("convertErpLocalDateTimeToUtc requires a non-empty local datetime string");
  }
  try {
    const sourceZone = timezone ?? getERPTimezone();
    const parsedLocal = DateTime.fromISO(localDateTime, { zone: sourceZone });
    if (!parsedLocal.isValid) {
      throw new Error(
        `Invalid ERP local datetime "${localDateTime}" for zone "${sourceZone}": ${parsedLocal.invalidReason}`
      );
    }

    const utcDateTime = parsedLocal.setZone("utc");
    if (!utcDateTime.isValid) {
      throw new Error(
        `Unable to convert ERP local datetime "${localDateTime}" to UTC: ${utcDateTime.invalidReason}`
      );
    }

    return utcDateTime.toISO();
  } catch (error) {
    logger.error("convertErpLocalDateTimeToUtc: Failed to convert datetime", {
      localDateTime,
      error,
    });
    throw new Error(
      "Failed to convert ERP local datetime to UTC. See logs for details."
    );
  }
}