/**
 * Validation of opening slots.
 *
 * Returns the list of problems in French, ready to show next to the field that
 * caused them. It returns every problem rather than the first, so someone
 * fixing a day's hours on a phone is not sent round the loop three times.
 */

import { minutesOfTime } from './civil';
import type { Slot } from './types';

/** A shop day realistically has a morning, an afternoon, and at most one more. */
export const MAX_SLOTS_PER_DAY = 3;

const TIME_PATTERN = /^([01]\d|2[0-3]):([0-5]\d)$/;

export function validateSlots(slots: Slot[]): string[] {
  const errors: string[] = [];

  if (slots.length > MAX_SLOTS_PER_DAY) {
    errors.push(`Trois plages horaires au maximum par jour (${slots.length} fournies).`);
  }

  const wellFormed: Slot[] = [];

  for (const slot of slots) {
    let malformed = false;
    for (const time of [slot.open, slot.close]) {
      if (!TIME_PATTERN.test(time)) {
        errors.push(`Heure invalide : « ${time} ». Format attendu : HH:mm.`);
        malformed = true;
      }
    }
    if (malformed) {
      continue;
    }
    if (minutesOfTime(slot.close) <= minutesOfTime(slot.open)) {
      errors.push(
        `L'heure de fermeture doit suivre l'heure d'ouverture : ${slot.open} – ${slot.close}.`,
      );
      continue;
    }
    wellFormed.push(slot);
  }

  // Overlaps are checked in chronological order, so the message names the
  // slots the way the user reads them rather than the way they were typed.
  const ordered = [...wellFormed].sort((a, b) => minutesOfTime(a.open) - minutesOfTime(b.open));
  for (let index = 1; index < ordered.length; index += 1) {
    const previous = ordered[index - 1];
    const current = ordered[index];
    if (!previous || !current) {
      continue;
    }
    if (minutesOfTime(current.open) < minutesOfTime(previous.close)) {
      errors.push(
        `Les plages ${previous.open} – ${previous.close} et ${current.open} – ${current.close} se chevauchent.`,
      );
    }
  }

  return errors;
}