import type { Language, TranslationKey } from "@/lib/i18n";
import { translate } from "@/lib/i18n";
import type { HourlyForecast } from "@/types/forecast";

export function getForecastConditionKey(code: number | null): TranslationKey {
  if (code === 0) return "forecast.condition.clear";
  if (code === 1 || code === 2) return "forecast.condition.partlyCloudy";
  if (code === 3) return "forecast.condition.cloudy";
  if (code === 45 || code === 48) return "forecast.condition.fog";
  if (code !== null && code >= 51 && code <= 57) return "forecast.condition.drizzle";
  if (code !== null && ((code >= 61 && code <= 67) || (code >= 80 && code <= 82))) return "forecast.condition.rain";
  if (code !== null && ((code >= 71 && code <= 77) || code === 85 || code === 86)) return "forecast.condition.snow";
  if (code !== null && code >= 95) return "forecast.condition.thunderstorm";
  return "forecast.condition.unknown";
}

export function getForecastCondition(code: number | null, language: Language) {
  return translate(language, getForecastConditionKey(code));
}

export function formatForecastTemperature(value: number | null, language: Language) {
  if (value === null) return "—";
  return `${new Intl.NumberFormat(language === "pl" ? "pl-PL" : "en-GB", { maximumFractionDigits: 0 }).format(value)}°`;
}

export function formatForecastRainfall(value: number | null, language: Language) {
  if (value === null) return "—";
  return `${new Intl.NumberFormat(language === "pl" ? "pl-PL" : "en-GB", { maximumFractionDigits: 1 }).format(value)} mm`;
}

export function formatForecastWind(value: number | null, language: Language) {
  if (value === null) return "—";
  return `${new Intl.NumberFormat(language === "pl" ? "pl-PL" : "en-GB", {
    minimumFractionDigits: 1,
    maximumFractionDigits: 1,
  }).format(value)} m/s`;
}

function getWarsawForecastHour(date = new Date()) {
  const parts = new Intl.DateTimeFormat("en-CA", {
    timeZone: "Europe/Warsaw",
    year: "numeric",
    month: "2-digit",
    day: "2-digit",
    hour: "2-digit",
    hourCycle: "h23",
  }).formatToParts(date);
  const getPart = (type: Intl.DateTimeFormatPartTypes) => parts.find((part) => part.type === type)?.value ?? "";

  return `${getPart("year")}-${getPart("month")}-${getPart("day")}T${getPart("hour")}:00`;
}

function parseForecastHour(time: string) {
  const match = time.match(/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})/);
  if (!match) return null;
  const [, year, month, day, hour, minute] = match;
  const timestamp = Date.UTC(Number(year), Number(month) - 1, Number(day), Number(hour), Number(minute));
  return Number.isFinite(timestamp) ? timestamp : null;
}

function getForecastHourOfDay(time: string) {
  const match = time.match(/T(\d{2}):/);
  return match ? Number(match[1]) : null;
}

export function getUpcomingHourlyForecast(hours: HourlyForecast[], limit = 24) {
  const currentHour = getWarsawForecastHour();
  const currentTimestamp = parseForecastHour(currentHour);
  const upcomingHours = currentTimestamp === null
    ? hours.filter((hour) => hour.time >= currentHour)
    : hours.filter((hour) => {
      const hourTimestamp = parseForecastHour(hour.time);
      return hourTimestamp === null ? hour.time >= currentHour : hourTimestamp >= currentTimestamp;
    });

  if (upcomingHours.length) return upcomingHours.slice(0, limit);

  const currentHourOfDay = getForecastHourOfDay(currentHour);
  const fallbackHours = currentHourOfDay === null
    ? hours
    : hours.filter((hour) => {
      const forecastHourOfDay = getForecastHourOfDay(hour.time);
      return forecastHourOfDay === null || forecastHourOfDay >= currentHourOfDay;
    });

  return (fallbackHours.length ? fallbackHours : hours).slice(0, limit);
}

export function getHourlyForecastForDay(hours: HourlyForecast[], date: string) {
  return hours.filter((hour) => hour.time.startsWith(`${date}T`));
}

export function isForecastHourPast(time: string) {
  return time < getWarsawForecastHour();
}