/**
 * shared/openingHours.ts
 * Helpers for clinic opening hours validation.
 * Used by both server (queue.join validation) and client (PatientQueue display).
 */

export type DayKey = "monday" | "tuesday" | "wednesday" | "thursday" | "friday" | "saturday" | "sunday";

export interface DaySchedule {
  open: string;   // "HH:MM" 24h format, e.g. "08:30"
  close: string;  // "HH:MM" 24h format, e.g. "18:00"
  closed: boolean;
}

export type OpeningHours = Partial<Record<DayKey, DaySchedule>>;

export const DAY_KEYS: DayKey[] = [
  "monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday",
];

export const DAY_LABELS_FR: Record<DayKey, string> = {
  monday: "Lundi",
  tuesday: "Mardi",
  wednesday: "Mercredi",
  thursday: "Jeudi",
  friday: "Vendredi",
  saturday: "Samedi",
  sunday: "Dimanche",
};

/** Map JS Date.getDay() (0=Sunday) to DayKey */
const JS_DAY_TO_KEY: DayKey[] = [
  "sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday",
];

/** Parse "HH:MM" into { hours, minutes } */
function parseTime(time: string): { hours: number; minutes: number } {
  const [h, m] = time.split(":").map(Number);
  return { hours: h ?? 0, minutes: m ?? 0 };
}

/** Convert HH:MM to total minutes since midnight */
function toMinutes(time: string): number {
  const { hours, minutes } = parseTime(time);
  return hours * 60 + minutes;
}

/** Format HH:MM to human-readable "8h30" or "18h00" */
export function formatTime(time: string): string {
  const { hours, minutes } = parseTime(time);
  return minutes === 0 ? `${hours}h` : `${hours}h${String(minutes).padStart(2, "0")}`;
}

/**
 * Check if the clinic is currently open based on its opening hours.
 * @param openingHours - The clinic's opening hours configuration (from DB)
 * @param now - Optional Date to check against (defaults to current time)
 * @returns true if the clinic is currently open
 */
export function isClinicOpen(
  openingHours: OpeningHours | null | undefined,
  now?: Date
): boolean {
  // If no hours configured → always open
  if (!openingHours || Object.keys(openingHours).length === 0) return true;

  const date = now ?? new Date();
  const dayKey = JS_DAY_TO_KEY[date.getDay()];
  const schedule = openingHours[dayKey];

  // Day not configured → closed
  if (!schedule) return false;
  if (schedule.closed) return false;

  const currentMinutes = date.getHours() * 60 + date.getMinutes();
  const openMinutes = toMinutes(schedule.open);
  const closeMinutes = toMinutes(schedule.close);

  return currentMinutes >= openMinutes && currentMinutes < closeMinutes;
}

/**
 * Get today's schedule for the clinic.
 */
export function getTodaySchedule(
  openingHours: OpeningHours | null | undefined,
  now?: Date
): { dayKey: DayKey; schedule: DaySchedule | null } {
  const date = now ?? new Date();
  const dayKey = JS_DAY_TO_KEY[date.getDay()];

  if (!openingHours) return { dayKey, schedule: null };

  const schedule = openingHours[dayKey] ?? null;
  return { dayKey, schedule };
}

/**
 * Get the next opening time (day + time) from now.
 * Returns null if no hours are configured.
 */
export function getNextOpeningTime(
  openingHours: OpeningHours | null | undefined,
  now?: Date
): { dayKey: DayKey; dayLabel: string; openTime: string } | null {
  if (!openingHours || Object.keys(openingHours).length === 0) return null;

  const date = now ?? new Date();
  const todayJsDay = date.getDay(); // 0=Sunday

  // Check next 7 days (including today if not yet open)
  for (let offset = 0; offset < 7; offset++) {
    const jsDay = (todayJsDay + offset) % 7;
    const dayKey = JS_DAY_TO_KEY[jsDay];
    const schedule = openingHours[dayKey];

    if (!schedule || schedule.closed) continue;

    const openMinutes = toMinutes(schedule.open);
    const currentMinutes = date.getHours() * 60 + date.getMinutes();

    // Today: only if opening time is in the future
    if (offset === 0 && currentMinutes >= openMinutes) continue;

    return {
      dayKey,
      dayLabel: DAY_LABELS_FR[dayKey],
      openTime: formatTime(schedule.open),
    };
  }

  return null;
}

/**
 * Build a human-readable error message when the clinic is closed.
 */
export function buildClosedMessage(
  openingHours: OpeningHours | null | undefined,
  clinicName: string,
  now?: Date
): string {
  const next = getNextOpeningTime(openingHours, now);
  const { dayKey, schedule } = getTodaySchedule(openingHours, now);
  const todayLabel = DAY_LABELS_FR[dayKey];

  if (!schedule || schedule.closed) {
    if (next) {
      return `${clinicName} est fermé aujourd'hui (${todayLabel}). Prochaine ouverture : ${next.dayLabel} à ${next.openTime}.`;
    }
    return `${clinicName} est actuellement fermé.`;
  }

  // Today has hours but we're outside them
  const currentMinutes = (now ?? new Date()).getHours() * 60 + (now ?? new Date()).getMinutes();
  const openMinutes = toMinutes(schedule.open);
  const closeMinutes = toMinutes(schedule.close);

  if (currentMinutes < openMinutes) {
    return `${clinicName} ouvre à ${formatTime(schedule.open)} aujourd'hui. Revenez plus tard.`;
  }
  if (currentMinutes >= closeMinutes) {
    if (next) {
      return `${clinicName} est fermé pour aujourd'hui. Prochaine ouverture : ${next.dayLabel} à ${next.openTime}.`;
    }
    return `${clinicName} est fermé pour aujourd'hui.`;
  }

  return `${clinicName} est actuellement fermé.`;
}

/**
 * Format opening hours for display in a weekly schedule.
 */
export function formatWeeklySchedule(
  openingHours: OpeningHours | null | undefined
): Array<{ dayKey: DayKey; dayLabel: string; hours: string }> {
  return DAY_KEYS.map((dayKey) => {
    const schedule = openingHours?.[dayKey];
    if (!schedule || schedule.closed) {
      return { dayKey, dayLabel: DAY_LABELS_FR[dayKey], hours: "Fermé" };
    }
    return {
      dayKey,
      dayLabel: DAY_LABELS_FR[dayKey],
      hours: `${formatTime(schedule.open)} – ${formatTime(schedule.close)}`,
    };
  });
}