/**
 * Détermine l'ordre d'affichage des séquences sur le lien d'inscription public.
 * Les sessions ouvertes avec des places disponibles sont toujours proposées en premier.
 */
export type RegistrationSequence = {
  id: number;
  nom: string;
  statut: string;
  dateBlocage?: Date | string | null;
  capaciteMax: number;
  nbInscrits?: number | null;
  dates?: ReadonlyArray<{ dateDebut: Date | string }>;
};

export type RegistrationSequenceWithAvailability<T extends RegistrationSequence> = T & {
  isBloquee: boolean;
  placesRestantes: number;
};

function firstDateTimestamp(sequence: RegistrationSequence): number {
  const firstDate = sequence.dates?.[0]?.dateDebut;
  if (!firstDate) return Number.MAX_SAFE_INTEGER;

  const timestamp = new Date(firstDate).getTime();
  return Number.isFinite(timestamp) ? timestamp : Number.MAX_SAFE_INTEGER;
}

function displayPriority(sequence: RegistrationSequenceWithAvailability<RegistrationSequence>): number {
  if (sequence.isBloquee) return 2;
  return sequence.placesRestantes > 0 ? 0 : 1;
}

export function sortSequencesForRegistration<T extends RegistrationSequence>(
  sequences: readonly T[],
  now = new Date(),
): RegistrationSequenceWithAvailability<T>[] {
  return sequences
    .map((sequence) => {
      const dateBlocage = sequence.dateBlocage ? new Date(sequence.dateBlocage) : null;
      const hasReachedBlockingDate = dateBlocage !== null && now >= dateBlocage;
      const isBloquee = sequence.statut !== "ouverte" || hasReachedBlockingDate;
      const placesRestantes = Math.max(0, sequence.capaciteMax - (sequence.nbInscrits ?? 0));

      return { ...sequence, isBloquee, placesRestantes };
    })
    .sort((left, right) => {
      const priorityDifference = displayPriority(left) - displayPriority(right);
      if (priorityDifference !== 0) return priorityDifference;

      const dateDifference = firstDateTimestamp(left) - firstDateTimestamp(right);
      if (dateDifference !== 0) return dateDifference;

      return left.nom.localeCompare(right.nom, "fr", { sensitivity: "base" });
    });
}