/**
 * French and English rendering of dates, times and opening hours.
 *
 * The month and day names are spelled out here rather than obtained from Intl
 * on purpose. The screen text has to be byte-stable: it feeds a content hash
 * that decides whether the e-ink panel redraws at all, so it must not shift
 * because a container image ships different ICU locale data.
 */

import { addCivilDays, civilDayOfWeek, minutesOfTime, type CivilDate } from './civil';
import type { Slot } from './types';

const MONTHS_FR = [
  'janvier',
  'février',
  'mars',
  'avril',
  'mai',
  'juin',
  'juillet',
  'août',
  'septembre',
  'octobre',
  'novembre',
  'décembre',
];

const MONTHS_EN = [
  'January',
  'February',
  'March',
  'April',
  'May',
  'June',
  'July',
  'August',
  'September',
  'October',
  'November',
  'December',
];

/** Indexed by `getDay()`: 0 = Sunday. */
const DAYS_FR = ['dimanche', 'lundi', 'mardi', 'mercredi', 'jeudi', 'vendredi', 'samedi'];
const DAYS_EN = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
const SHORT_DAYS_FR = ['Dim', 'Lun', 'Mar', 'Mer', 'Jeu', 'Ven', 'Sam'];
const SHORT_DAYS_EN = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];

/** What the next change is: the door closing, or the door opening. */
export type NextChange = {
  kind: 'OPENS' | 'CLOSES';
  date: CivilDate;
  time: string;
};

function parts(date: CivilDate): { day: number; monthIndex: number } {
  const [, month, day] = date.split('-');
  return { day: Number(day), monthIndex: Number(month) - 1 };
}

function capitalise(value: string): string {
  return value.charAt(0).toUpperCase() + value.slice(1);
}

/** "Dimanche 20 septembre" */
export function formatDateFr(date: CivilDate): string {
  const { day, monthIndex } = parts(date);
  return `${capitalise(DAYS_FR[civilDayOfWeek(date)] ?? '')} ${day} ${MONTHS_FR[monthIndex] ?? ''}`;
}

/** "Sunday 20 September" */
export function formatDateEn(date: CivilDate): string {
  const { day, monthIndex } = parts(date);
  return `${DAYS_EN[civilDayOfWeek(date)] ?? ''} ${day} ${MONTHS_EN[monthIndex] ?? ''}`;
}

export function shortDayLabelFr(dayOfWeek: number): string {
  return SHORT_DAYS_FR[dayOfWeek] ?? '';
}

export function shortDayLabelEn(dayOfWeek: number): string {
  return SHORT_DAYS_EN[dayOfWeek] ?? '';
}

/** "10:00 – 13:00 · 14:00 – 18:30", or an empty string when closed. */
export function formatHoursText(slots: Slot[]): string {
  return slots.map((slot) => `${slot.open} – ${slot.close}`).join(' · ');
}

/** "6:30 pm" — English readers expect the twelve-hour clock. */
export function formatTimeEn(time: string): string {
  const minutes = minutesOfTime(time);
  const hour24 = Math.floor(minutes / 60);
  const minute = minutes % 60;
  const suffix = hour24 < 12 ? 'am' : 'pm';
  const hour12 = hour24 % 12 === 0 ? 12 : hour24 % 12;
  return `${hour12}:${minute.toString().padStart(2, '0')} ${suffix}`;
}

/**
 * Rewrites 24-hour times in English text to the 12-hour clock.
 *
 * The labels this application generates itself already read "6:30 pm", while a
 * translated message keeps whatever the source said, because the prompt tells
 * the model to leave times alone — which it should, since converting a clock
 * is not a job for a language model. Doing it here instead keeps both
 * conventions from appearing side by side on the same panel.
 *
 * Only `HH:mm` is touched, and never a time that already carries am/pm, so
 * years and dates written 20/07 are left alone.
 */
export function toEnglishClock(text: string): string {
  return text.replace(
    /\b([01]?\d|2[0-3]):([0-5]\d)\b(?!\s*(?:am|pm|AM|PM))/g,
    (match, hours: string, minutes: string) =>
      formatTimeEn(`${hours.padStart(2, '0')}:${minutes}`) ?? match,
  );
}

export function formatNextChangeFr(change: NextChange | null, today: CivilDate): string {
  if (!change) {
    return '';
  }
  const verb = change.kind === 'CLOSES' ? 'Ferme' : 'Ouvre';
  return `${verb}${whenFr(change.date, today)} à ${change.time}`;
}

export function formatNextChangeEn(change: NextChange | null, today: CivilDate): string {
  if (!change) {
    return '';
  }
  const verb = change.kind === 'CLOSES' ? 'Closes' : 'Opens';
  return `${verb}${whenEn(change.date, today)} at ${formatTimeEn(change.time)}`;
}

function whenFr(date: CivilDate, today: CivilDate): string {
  if (date === today) {
    return '';
  }
  if (date === addCivilDays(today, 1)) {
    return ' demain';
  }
  return ` ${DAYS_FR[civilDayOfWeek(date)] ?? ''}`;
}

function whenEn(date: CivilDate, today: CivilDate): string {
  if (date === today) {
    return '';
  }
  if (date === addCivilDays(today, 1)) {
    return ' tomorrow';
  }
  return ` ${DAYS_EN[civilDayOfWeek(date)] ?? ''}`;
}