'use client';

import { useMemo, useState, useTransition } from 'react';

import { MAX_SLOTS_PER_DAY } from '@/lib/schedule/validate';
import {
  changedDays,
  DAY_NAMES_FR,
  duplicateToOpenDays,
  validateWeek,
  type WeekDraft,
} from '@/lib/schedule/week';

import { saveWeek } from './actions';

type Props = {
  initial: WeekDraft;
  canEdit: boolean;
};

/**
 * The reference week.
 *
 * Built for a phone held in one hand behind the counter: one card per day,
 * native time inputs so the platform keyboard does the work, and the
 * consequences of a change shown before it is saved rather than after.
 */
export default function WeekEditor({ initial, canEdit }: Props) {
  const [week, setWeek] = useState<WeekDraft>(initial);
  const [saved, setSaved] = useState<WeekDraft>(initial);
  const [pending, startTransition] = useTransition();
  const [message, setMessage] = useState<{ kind: 'ok' | 'error'; text: string } | null>(null);
  const [serverErrors, setServerErrors] = useState<Record<number, string[]>>({});

  const errors = useMemo(() => validateWeek(week), [week]);
  const pendingChanges = useMemo(() => changedDays(saved, week), [saved, week]);
  const blocked = Object.keys(errors).length > 0;

  function update(dayOfWeek: number, patch: Partial<WeekDraft[number]>) {
    setMessage(null);
    setServerErrors({});
    setWeek((current) =>
      current.map((day) => (day.dayOfWeek === dayOfWeek ? { ...day, ...patch } : day)),
    );
  }

  function updateSlot(dayOfWeek: number, index: number, field: 'open' | 'close', value: string) {
    setWeek((current) =>
      current.map((day) =>
        day.dayOfWeek === dayOfWeek
          ? {
              ...day,
              slots: day.slots.map((slot, position) =>
                position === index ? { ...slot, [field]: value } : slot,
              ),
            }
          : day,
      ),
    );
    setMessage(null);
  }

  function addSlot(dayOfWeek: number) {
    update(dayOfWeek, {
      slots: [
        ...(week.find((day) => day.dayOfWeek === dayOfWeek)?.slots ?? []),
        { open: '14:00', close: '18:30' },
      ],
    });
  }

  function removeSlot(dayOfWeek: number, index: number) {
    const day = week.find((entry) => entry.dayOfWeek === dayOfWeek);
    update(dayOfWeek, { slots: (day?.slots ?? []).filter((_, position) => position !== index) });
  }

  function submit() {
    setMessage(null);
    setServerErrors({});
    startTransition(async () => {
      const result = await saveWeek(week);
      if (result.ok) {
        setSaved(week);
        setMessage({
          kind: 'ok',
          text:
            result.changed.length === 0
              ? 'Aucun changement à enregistrer.'
              : `Horaires enregistrés (${result.changed.length} jour${result.changed.length > 1 ? 's' : ''} modifié${result.changed.length > 1 ? 's' : ''}).`,
        });
      } else {
        setServerErrors(result.dayErrors ?? {});
        setMessage({ kind: 'error', text: result.error });
      }
    });
  }

  return (
    <div className="mt-8">
      {!canEdit ? (
        <p className="mb-6 rounded-[var(--radius-md)] border border-[var(--line-strong)] bg-[var(--surface-muted)] px-4 py-3 text-sm text-[var(--ink-muted)]">
          Ce compte est en lecture seule&nbsp;: les horaires sont consultables mais pas modifiables.
        </p>
      ) : null}

      <div className="space-y-3">
        {week.map((day) => {
          const dayErrors = [...(errors[day.dayOfWeek] ?? []), ...(serverErrors[day.dayOfWeek] ?? [])];
          const isChanged = pendingChanges.includes(day.dayOfWeek);

          return (
            <section
              key={day.dayOfWeek}
              className={`rounded-[var(--radius-md)] border bg-[var(--surface)] p-4 ${
                dayErrors.length > 0 ? 'border-[var(--danger)]' : 'border-[var(--line)]'
              }`}
            >
              <div className="flex flex-wrap items-center gap-3">
                <h2 className="min-w-28 text-base font-medium">{DAY_NAMES_FR[day.dayOfWeek]}</h2>

                <label className="flex items-center gap-2 text-sm">
                  <input
                    type="checkbox"
                    className="size-4 accent-[var(--accent)]"
                    checked={!day.isClosed}
                    disabled={!canEdit}
                    onChange={(event) =>
                      update(day.dayOfWeek, {
                        isClosed: !event.target.checked,
                        slots:
                          event.target.checked && day.slots.length === 0
                            ? [{ open: '10:00', close: '18:30' }]
                            : day.slots,
                      })
                    }
                  />
                  Ouvert
                </label>

                {isChanged ? (
                  <span className="rounded-[var(--radius-sm)] bg-[var(--accent-tint)] px-2 py-0.5 text-xs text-[var(--accent-ink)]">
                    modifié
                  </span>
                ) : null}
              </div>

              {day.isClosed ? (
                <p className="mt-3 text-sm text-[var(--ink-muted)]">Fermé toute la journée.</p>
              ) : (
                <div className="mt-3 space-y-2">
                  {day.slots.map((slot, index) => (
                    <div key={index} className="flex flex-wrap items-center gap-2">
                      <input
                        type="time"
                        aria-label={`${DAY_NAMES_FR[day.dayOfWeek]} — ouverture ${index + 1}`}
                        value={slot.open}
                        disabled={!canEdit}
                        onChange={(event) =>
                          updateSlot(day.dayOfWeek, index, 'open', event.target.value)
                        }
                        className="rounded-[var(--radius-sm)] border border-[var(--line-strong)] bg-[var(--surface)] px-2 py-1.5 text-base tabular-nums"
                      />
                      <span aria-hidden className="text-[var(--ink-muted)]">
                        –
                      </span>
                      <input
                        type="time"
                        aria-label={`${DAY_NAMES_FR[day.dayOfWeek]} — fermeture ${index + 1}`}
                        value={slot.close}
                        disabled={!canEdit}
                        onChange={(event) =>
                          updateSlot(day.dayOfWeek, index, 'close', event.target.value)
                        }
                        className="rounded-[var(--radius-sm)] border border-[var(--line-strong)] bg-[var(--surface)] px-2 py-1.5 text-base tabular-nums"
                      />
                      {canEdit && day.slots.length > 1 ? (
                        <button
                          type="button"
                          onClick={() => removeSlot(day.dayOfWeek, index)}
                          className="rounded-[var(--radius-sm)] px-2 py-1.5 text-sm text-[var(--ink-muted)] underline-offset-2 hover:underline"
                        >
                          Retirer
                        </button>
                      ) : null}
                    </div>
                  ))}

                  {canEdit && day.slots.length < MAX_SLOTS_PER_DAY ? (
                    <button
                      type="button"
                      onClick={() => addSlot(day.dayOfWeek)}
                      className="text-sm text-[var(--accent-ink)] underline-offset-2 hover:underline"
                    >
                      + Ajouter une plage (pause de midi)
                    </button>
                  ) : null}

                  {canEdit ? (
                    <div>
                      <button
                        type="button"
                        onClick={() => setWeek(duplicateToOpenDays(week, day.dayOfWeek))}
                        className="text-sm text-[var(--ink-muted)] underline-offset-2 hover:underline"
                      >
                        Dupliquer sur les autres jours ouverts
                      </button>
                    </div>
                  ) : null}
                </div>
              )}

              {dayErrors.length > 0 ? (
                <ul role="alert" className="mt-3 space-y-1 text-sm text-[var(--danger)]">
                  {dayErrors.map((error) => (
                    <li key={error}>{error}</li>
                  ))}
                </ul>
              ) : null}
            </section>
          );
        })}
      </div>

      {canEdit ? (
        <div className="sticky bottom-0 mt-6 flex flex-wrap items-center gap-3 border-t border-[var(--line)] bg-[var(--canvas)] py-4">
          <button
            type="button"
            onClick={submit}
            disabled={pending || blocked || pendingChanges.length === 0}
            className="rounded-[var(--radius-md)] bg-[var(--accent)] px-5 py-2.5 font-medium text-[var(--on-accent)] transition-colors hover:bg-[var(--accent-hover)] disabled:cursor-not-allowed disabled:opacity-40"
          >
            {pending ? 'Enregistrement…' : 'Enregistrer'}
          </button>

          {pendingChanges.length > 0 ? (
            <button
              type="button"
              onClick={() => {
                setWeek(saved);
                setMessage(null);
                setServerErrors({});
              }}
              className="text-sm text-[var(--ink-muted)] underline-offset-2 hover:underline"
            >
              Annuler les modifications
            </button>
          ) : null}

          <p className="text-sm text-[var(--ink-muted)]" aria-live="polite">
            {blocked
              ? 'Corrigez les erreurs ci-dessus.'
              : pendingChanges.length === 0
                ? 'Aucune modification.'
                : `${pendingChanges.length} jour${pendingChanges.length > 1 ? 's' : ''} sera modifié : ${pendingChanges
                    .map((dayOfWeek) => DAY_NAMES_FR[dayOfWeek])
                    .join(', ')}.`}
          </p>
        </div>
      ) : null}

      {message ? (
        <p
          role="status"
          className={`mt-4 rounded-[var(--radius-md)] px-4 py-3 text-sm ${
            message.kind === 'ok'
              ? 'bg-[var(--success-tint)] text-[var(--success)]'
              : 'bg-[var(--danger-tint)] text-[var(--danger)]'
          }`}
        >
          {message.text}
        </p>
      ) : null}
    </div>
  );
}