import { useState, useEffect } from 'react';
import { format } from 'date-fns';
import { Trash2 } from 'lucide-react';
import { useMutation, useQueryClient } from '@tanstack/react-query';
import { api, type CalendarEvent } from '@/lib/api';
import { useMembers } from '@/hooks/useMembers';
import { Modal } from '@/components/ui/Modal';
import { Input } from '@/components/ui/Input';
import { Textarea } from '@/components/ui/Textarea';
import { Select } from '@/components/ui/Select';
import { Button } from '@/components/ui/Button';

interface Props {
  open: boolean;
  onClose: () => void;
  event?: CalendarEvent | null;
  defaultDate?: Date;
}

function toDateTimeLocal(iso: string) {
  return iso ? iso.slice(0, 16) : '';
}

function toISO(local: string) {
  return local ? new Date(local).toISOString() : '';
}

const RECURRENCE_OPTIONS = [
  { value: 'none',    label: 'Does not repeat' },
  { value: 'daily',   label: 'Daily' },
  { value: 'weekly',  label: 'Weekly' },
  { value: 'monthly', label: 'Monthly' },
  { value: 'yearly',  label: 'Yearly' },
];

export function EventModal({ open, onClose, event, defaultDate }: Props) {
  const qc = useQueryClient();
  const { data: members = [] } = useMembers();
  const isEdit = !!event;

  const blank = () => {
    const d = defaultDate ?? new Date();
    const start = new Date(d);
    start.setHours(9, 0, 0, 0);
    const end = new Date(d);
    end.setHours(10, 0, 0, 0);
    return {
      title: '', description: '', all_day: false, recurrence: 'none',
      member_id: '', color: '',
      start_at: format(start, "yyyy-MM-dd'T'HH:mm"),
      end_at: format(end,   "yyyy-MM-dd'T'HH:mm"),
    };
  };

  const [form, setForm] = useState(blank);
  const [error, setError] = useState('');

  useEffect(() => {
    if (!open) return;
    if (event) {
      setForm({
        title:       event.title,
        description: event.description ?? '',
        all_day:     !!event.all_day,
        recurrence:  event.recurrence ?? 'none',
        member_id:   event.member_id ? String(event.member_id) : '',
        color:       event.color ?? '',
        start_at:    toDateTimeLocal(event.start_at),
        end_at:      toDateTimeLocal(event.end_at),
      });
    } else {
      setForm(blank());
    }
    setError('');
  }, [open, event]);

  const set = (k: keyof typeof form, v: string | boolean) =>
    setForm((f) => ({ ...f, [k]: v }));

  const saveMutation = useMutation({
    mutationFn: (body: object) =>
      isEdit
        ? api.put(`/events/${event!.id}`, body).then((r) => r.data)
        : api.post('/events', body).then((r) => r.data),
    onSuccess: () => { qc.invalidateQueries({ queryKey: ['events'] }); onClose(); },
    onError: () => setError('Failed to save event. Please try again.'),
  });

  const deleteMutation = useMutation({
    mutationFn: () => api.delete(`/events/${event!.id}`),
    onSuccess: () => { qc.invalidateQueries({ queryKey: ['events'] }); onClose(); },
  });

  const handleSubmit = () => {
    if (!form.title.trim()) { setError('Title is required'); return; }
    if (!form.start_at || !form.end_at) { setError('Start and end times are required'); return; }
    saveMutation.mutate({
      title:       form.title.trim(),
      description: form.description || null,
      start_at:    toISO(form.start_at),
      end_at:      toISO(form.end_at),
      all_day:     form.all_day,
      recurrence:  form.recurrence === 'none' ? null : form.recurrence,
      member_id:   form.member_id ? Number(form.member_id) : null,
      color:       form.color || null,
    });
  };

  // Derive chip color: use selected member's color, or user-picked color, or accent
  const chipColor = (() => {
    if (form.color) return form.color;
    if (form.member_id) return members.find((m) => m.id === Number(form.member_id))?.color ?? '';
    return '';
  })();

  return (
    <Modal open={open} onClose={onClose} title={isEdit ? 'Edit Event' : 'New Event'} size="lg">
      <div className="space-y-4">
        <Input
          label="Title"
          value={form.title}
          onChange={(e) => set('title', e.target.value)}
          placeholder="Event title"
          autoFocus
        />

        <div className="grid grid-cols-2 gap-4">
          <div>
            <label className="text-sm font-medium text-secondary block mb-1.5">Start</label>
            <input
              type={form.all_day ? 'date' : 'datetime-local'}
              value={form.all_day ? form.start_at.slice(0, 10) : form.start_at}
              onChange={(e) => set('start_at', e.target.value)}
              className="w-full rounded-lg border border-theme bg-surface-raised px-3 py-2 text-sm text-primary focus:outline-none focus:ring-2 ring-accent transition-colors"
            />
          </div>
          <div>
            <label className="text-sm font-medium text-secondary block mb-1.5">End</label>
            <input
              type={form.all_day ? 'date' : 'datetime-local'}
              value={form.all_day ? form.end_at.slice(0, 10) : form.end_at}
              onChange={(e) => set('end_at', e.target.value)}
              className="w-full rounded-lg border border-theme bg-surface-raised px-3 py-2 text-sm text-primary focus:outline-none focus:ring-2 ring-accent transition-colors"
            />
          </div>
        </div>

        <label className="flex items-center gap-3 cursor-pointer select-none">
          <div
            onClick={() => set('all_day', !form.all_day)}
            className={`relative h-5 w-9 rounded-full transition-colors duration-200 ${form.all_day ? 'bg-accent' : 'bg-border'}`}
          >
            <span className={`absolute top-0.5 h-4 w-4 rounded-full bg-white shadow transition-all duration-200 ${form.all_day ? 'left-[18px]' : 'left-0.5'}`} />
          </div>
          <span className="text-sm font-medium text-secondary">All day</span>
        </label>

        <div className="grid grid-cols-2 gap-4">
          <Select
            label="Family Member"
            value={form.member_id}
            onChange={(e) => set('member_id', e.target.value)}
          >
            <option value="">No one assigned</option>
            {members.map((m) => (
              <option key={m.id} value={m.id}>{m.name}</option>
            ))}
          </Select>
          <Select
            label="Repeats"
            value={form.recurrence}
            onChange={(e) => set('recurrence', e.target.value)}
          >
            {RECURRENCE_OPTIONS.map((o) => (
              <option key={o.value} value={o.value}>{o.label}</option>
            ))}
          </Select>
        </div>

        <Textarea
          label="Description"
          value={form.description}
          onChange={(e) => set('description', e.target.value)}
          placeholder="Optional notes…"
          rows={2}
        />

        <div>
          <label className="text-sm font-medium text-secondary block mb-1.5">
            Event Color <span className="text-muted font-normal">(overrides member color)</span>
          </label>
          <div className="flex items-center gap-3">
            <input
              type="color"
              value={chipColor || '#6366f1'}
              onChange={(e) => set('color', e.target.value)}
              className="h-9 w-12 cursor-pointer rounded-lg border border-theme bg-transparent"
            />
            {chipColor && (
              <span
                className="px-3 py-1 rounded-full text-xs font-medium text-white"
                style={{ backgroundColor: chipColor }}
              >
                Preview
              </span>
            )}
            {form.color && (
              <button
                className="text-xs text-muted hover:text-secondary"
                onClick={() => set('color', '')}
              >
                Clear override
              </button>
            )}
          </div>
        </div>

        {error && <p className="text-sm text-red-500">{error}</p>}

        <div className="flex items-center gap-2 pt-1">
          {isEdit && (
            <Button
              variant="ghost"
              onClick={() => deleteMutation.mutate()}
              loading={deleteMutation.isPending}
              className="text-red-500 hover:bg-red-50 dark:hover:bg-red-950"
            >
              <Trash2 size={16} />
            </Button>
          )}
          <div className="flex gap-2 ml-auto">
            <Button variant="secondary" onClick={onClose}>Cancel</Button>
            <Button onClick={handleSubmit} loading={saveMutation.isPending}>
              {isEdit ? 'Save Changes' : 'Add Event'}
            </Button>
          </div>
        </div>
      </div>
    </Modal>
  );
}