import { getCompanyInfo } from "../services/mm-api-service/company-info.js";
import { getIANATimezoneOffsetHours } from "./iana-timezone-offset.js";

/**
 * Gets the timezone offset in hours and timezone name for the company's timezone
 * (uses cached {@link getCompanyInfo} — no extra HTTP when already loaded).
 * @returns Promise<{ offset: number; timezone: string }> The timezone offset in hours and timezone name
 * @throws Error if unable to fetch timezone information
 */
export const getTimezoneOffset = async (): Promise<{ offset: number; timezone: string }> => {
  try {
    const info = await getCompanyInfo();
    const offset = getIANATimezoneOffsetHours(info.timezone);
    return { offset, timezone: info.timezone };
  } catch (error) {
    throw new Error(
      `Failed to get timezone offset: ${error instanceof Error ? error.message : "Unknown error"}`
    );
  }
};

/**
 * Converts a UTC/Zulu time to local time based on the provided timezone offset
 * @param zuluTime The UTC/Zulu time to convert
 * @param timezoneOffset The timezone offset in hours
 * @returns The converted local time, or undefined if input is null/undefined
 */
export const convertToLocalTime = (
  zuluTime: string | Date | null | undefined,
  timezoneOffset: number
): Date | undefined => {
  if (!zuluTime) return undefined;
  const date = new Date(zuluTime);
  return new Date(date.getTime() + timezoneOffset * 60 * 60 * 1000);
};

/**
 * Formats a date with the timezone offset in ISO format with offset
 * @param date The date string in format YYYY-MM-DD HH:mm:ss or YYYY-MM-DDTHH:mm:ss
 * @param timezoneOffset The timezone offset in hours
 * @returns The formatted date string in format: YYYY-MM-DDTHH:mm:ss+/-HH:MM
 */
export const formatDateWithTZOffset = (
  date: string | null | undefined,
  timezoneOffset: number
): string | undefined => {
  if (!date) return undefined;

  // Replace space with T if present
  const isoDate = date.replace(" ", "T");

  // Calculate offset components
  const sign = timezoneOffset >= 0 ? "+" : "-";
  const absOffset = Math.abs(timezoneOffset);
  const hours = Math.floor(absOffset).toString().padStart(2, "0");
  const minutes = Math.floor((absOffset % 1) * 60)
    .toString()
    .padStart(2, "0");

  // Append the timezone offset
  return `${isoDate}${sign}${hours}:${minutes}`;
};

/**
 * Formats a Date object as an ISO string with the specified timezone offset
 * @param date The Date object to format (should be a Date that has been shifted by convertToLocalTime)
 * @param timezoneOffset The timezone offset in hours
 * @returns ISO string with offset in format: YYYY-MM-DDTHH:mm:ss.SSS±HH:MM
 */
export const toISOWithOffset = (date: Date, timezoneOffset: number): string => {
  const sign = timezoneOffset >= 0 ? "+" : "-";
  const abs = Math.abs(timezoneOffset);
  const hours = Math.floor(abs);
  const minutes = Math.round((abs - hours) * 60);
  const pad2 = (n: number) => n.toString().padStart(2, "0");
  const pad3 = (n: number) => n.toString().padStart(3, "0");

  // Use UTC getters since convertToLocalTime shifts the Date's internal timestamp
  // The UTC components of the shifted Date represent the local wall time
  const yyyy = date.getUTCFullYear();
  const MM = pad2(date.getUTCMonth() + 1);
  const dd = pad2(date.getUTCDate());
  const HH = pad2(date.getUTCHours());
  const mm = pad2(date.getUTCMinutes());
  const ss = pad2(date.getUTCSeconds());
  const SSS = pad3(date.getUTCMilliseconds());
  const off = `${sign}${pad2(hours)}:${pad2(minutes)}`;

  return `${yyyy}-${MM}-${dd}T${HH}:${mm}:${ss}.${SSS}${off}`;
};