/**
 * Секция «Ближайшие занятия» для дашборда ментора (iOS 26).
 */

'use client';

import React, { useMemo, useState } from 'react';
import { MentorDashboardResponse } from '@/api/dashboard';
import { Panel, SectionHeader, FlipCard } from '../ui';
import { LoadingSpinner } from '@/components/common/LoadingSpinner';
import { getLesson, type Lesson } from '@/api/schedule';

export interface UpcomingLessonsSectionProps {
  data: MentorDashboardResponse | null;
  loading: boolean;
}

const formatDateTime = (dateTimeStr: string | null): string => {
  if (!dateTimeStr) return '—';
  try {
    const date = new Date(dateTimeStr);
    if (isNaN(date.getTime())) return '—';
    
    const today = new Date();
    const tomorrow = new Date(today);
    tomorrow.setDate(tomorrow.getDate() + 1);
    
    const isToday = date.toDateString() === today.toDateString();
    const isTomorrow = date.toDateString() === tomorrow.toDateString();
    
    const timeStr = date.toLocaleTimeString('ru-RU', {
      hour: '2-digit',
      minute: '2-digit',
    });
    
    if (isToday) {
      return `Сегодня, ${timeStr}`;
    } else if (isTomorrow) {
      return `Завтра, ${timeStr}`;
    } else {
      return date.toLocaleDateString('ru-RU', {
        day: 'numeric',
        month: 'short',
        hour: '2-digit',
        minute: '2-digit',
      });
    }
  } catch {
    return '—';
  }
};

export const UpcomingLessonsSection: React.FC<UpcomingLessonsSectionProps> = ({
  data,
  loading,
}) => {
  const lessons = data?.upcoming_lessons?.slice(0, 4) || [];

  const [flipped, setFlipped] = useState(false);
  const [selectedLessonId, setSelectedLessonId] = useState<string | null>(null);
  const [details, setDetails] = useState<Lesson | null>(null);
  const [loadingDetails, setLoadingDetails] = useState(false);

  const selectedPreview = useMemo(
    () => lessons.find((l) => l.id === selectedLessonId) || null,
    [lessons, selectedLessonId],
  );

  const formatFullDateTime = (dateTimeStr: string | null): string => {
    if (!dateTimeStr) return '—';
    try {
      const date = new Date(dateTimeStr);
      if (isNaN(date.getTime())) return '—';
      return date.toLocaleString('ru-RU', {
        day: 'numeric',
        month: 'long',
        year: 'numeric',
        hour: '2-digit',
        minute: '2-digit',
      });
    } catch {
      return '—';
    }
  };

  const openLessonDetails = async (lessonId: string) => {
    setSelectedLessonId(lessonId);
    setFlipped(true);
    setLoadingDetails(true);
    setDetails(null);
    try {
      const full = await getLesson(lessonId);
      setDetails(full);
    } catch (error) {
      console.error('Ошибка загрузки занятия:', error);
    } finally {
      setLoadingDetails(false);
    }
  };

  return (
    <FlipCard
      flipped={flipped}
      onFlippedChange={(v) => {
        // если пользователь кликнул по "пустому месту" в карточке — не хотим случайно закрывать,
        // но оставим стандартное поведение: переворот по клику на сам контейнер FlipCard.
        setFlipped(v);
      }}
      front={
        <Panel padding="md" data-tour="mentor-upcoming">
          <SectionHeader title="Ближайшие занятия" />
          {loading && !data ? (
            <LoadingSpinner size="medium" />
          ) : lessons.length === 0 ? (
            <div
              style={{
                padding: 'var(--ios26-spacing-md) 0',
                textAlign: 'center',
                color: 'var(--md-sys-color-on-surface-variant)',
                fontSize: 14,
              }}
            >
              Нет запланированных занятий
            </div>
          ) : (
            <div
              className="upcoming-lessons-grid"
              style={{
                display: 'grid',
                gridTemplateColumns: 'repeat(2, minmax(0, 1fr))',
                gap: 'var(--ios26-spacing-sm)',
              }}
              onClick={(e) => e.stopPropagation()}
            >
              {lessons.map((lesson) => {
                const client = lesson.client as any;
                const fullName =
                  client?.first_name || client?.last_name
                    ? `${client.first_name ?? ''} ${client.last_name ?? ''}`.trim()
                    : client?.name || 'Студент';

                return (
                  <button
                    key={lesson.id}
                    type="button"
                    onClick={() => openLessonDetails(lesson.id)}
                    className="ios26-lesson-preview"
                  >
                    <div className="ios26-lesson-avatar">
                      {client?.avatar ? (
                        <img src={client.avatar} alt={fullName} />
                      ) : (
                        <span>
                          {(fullName || 'С')[0]?.toUpperCase()}
                        </span>
                      )}
                    </div>
                    <div className="ios26-lesson-text">
                      <p className="ios26-lesson-subject">
                        {lesson.subject || 'Предмет не указан'}
                      </p>
                      <p className="ios26-lesson-student">
                        {fullName}
                      </p>
                      <p className="ios26-lesson-datetime">
                        {formatDateTime(lesson.start_time)}
                      </p>
                    </div>
                  </button>
                );
              })}
            </div>
          )}
        </Panel>
      }
      back={
        <Panel padding="md">
          <SectionHeader
            title="Детали занятия"
            trailing={
              <button
                type="button"
                onClick={(e) => {
                  e.stopPropagation();
                  setFlipped(false);
                }}
                className="ios26-back-button"
              >
                Назад
              </button>
            }
          />
          <div onClick={(e) => e.stopPropagation()}>
            {loadingDetails ? (
              <div
                style={{
                  padding: 'var(--ios26-spacing-md) 0',
                  textAlign: 'center',
                  color: 'var(--md-sys-color-on-surface-variant)',
                  fontSize: 14,
                }}
              >
                Загрузка...
              </div>
            ) : details ? (
              <div>
                <p style={{ fontSize: 18, fontWeight: 700, margin: '0 0 8px 0' }}>
                  {details.title || selectedPreview?.title || 'Занятие'}
                </p>
                {details.subject && (
                  <p style={{ fontSize: 14, margin: '0 0 8px 0', color: 'var(--md-sys-color-on-surface-variant)' }}>
                    Предмет: {details.subject}
                  </p>
                )}
                <p style={{ fontSize: 14, margin: '0 0 4px 0', color: 'var(--md-sys-color-on-surface-variant)' }}>
                  <strong>Начало:</strong> {formatFullDateTime(details.start_time)}
                </p>
                <p style={{ fontSize: 14, margin: '0 0 4px 0', color: 'var(--md-sys-color-on-surface-variant)' }}>
                  <strong>Окончание:</strong> {formatFullDateTime(details.end_time)}
                </p>
                {details.description && (
                  <p style={{ fontSize: 14, margin: '10px 0 0 0', lineHeight: 1.5 }}>
                    {details.description}
                  </p>
                )}
                {details.mentor_notes && (
                  <p style={{ fontSize: 13, margin: '10px 0 0 0', lineHeight: 1.5, fontStyle: 'italic', color: 'var(--md-sys-color-on-surface-variant)' }}>
                    <strong>Заметки:</strong> {details.mentor_notes}
                  </p>
                )}
              </div>
            ) : (
              <div
                style={{
                  padding: 'var(--ios26-spacing-md) 0',
                  textAlign: 'center',
                  color: 'var(--md-sys-color-on-surface-variant)',
                  fontSize: 14,
                }}
              >
                Не удалось загрузить детали
              </div>
            )}
          </div>
        </Panel>
      }
    />
  );
};