import { normalizeLocale, type SupportedLocale } from "./message-contract.js";

const FORMAT_FALLBACK = "—";

export type DateFormatStyle = "short" | "medium" | "long";

export function formatDate(
  locale: SupportedLocale,
  value: Date | number,
  options: Readonly<{
    dateStyle?: DateFormatStyle;
    timeZone?: string;
  }> = {},
): string {
  try {
    const date = value instanceof Date ? value : new Date(value);
    if (Number.isNaN(date.getTime())) return FORMAT_FALLBACK;
    return new Intl.DateTimeFormat(normalizeLocale(locale), {
      dateStyle: options.dateStyle ?? "medium",
      timeZone: options.timeZone ?? "UTC",
    }).format(date);
  } catch {
    return FORMAT_FALLBACK;
  }
}

export function formatNumber(
  locale: SupportedLocale,
  value: number,
  options: Readonly<{
    style?: "decimal" | "percent";
    maximumFractionDigits?: number;
  }> = {},
): string {
  try {
    if (!Number.isFinite(value)) return FORMAT_FALLBACK;
    return new Intl.NumberFormat(normalizeLocale(locale), options).format(value);
  } catch {
    return FORMAT_FALLBACK;
  }
}

export function formatRelativeTime(
  locale: SupportedLocale,
  value: number,
  unit: Intl.RelativeTimeFormatUnit,
): string {
  try {
    if (!Number.isFinite(value)) return FORMAT_FALLBACK;
    return new Intl.RelativeTimeFormat(normalizeLocale(locale), {
      numeric: "auto",
    }).format(value, unit);
  } catch {
    return FORMAT_FALLBACK;
  }
}

export function formatList(
  locale: SupportedLocale,
  values: readonly string[],
): string {
  try {
    return new Intl.ListFormat(normalizeLocale(locale), {
      style: "long",
      type: "conjunction",
    }).format(values);
  } catch {
    return values.join(", ");
  }
}

export function selectPlural(
  locale: SupportedLocale,
  value: number,
  choices: Readonly<
    Partial<Record<Intl.LDMLPluralRule, string>> & { other: string }
  >,
): string {
  try {
    if (!Number.isFinite(value)) return choices.other;
    return choices[
      new Intl.PluralRules(normalizeLocale(locale)).select(value)
    ] ?? choices.other;
  } catch {
    return choices.other;
  }
}

export function selectMessage(
  value: string,
  choices: Readonly<Record<string, string> & { other: string }>,
): string {
  return choices[value] ?? choices.other;
}

export { FORMAT_FALLBACK };