import { useEffect, useState } from 'react';
import { Plus, ArrowLeft, ArrowRight, Trash2, CheckSquare } from 'lucide-react';
import { api, fmt } from '../api';
import { Btn, Field, inputCls, Modal, Spinner, ErrorBox, StatusBadge, Badge, EmptyState } from '../components/ui';

export const TASK_STATUS_LABELS = { todo: 'Te doen', in_progress: 'Bezig', done: 'Klaar', cancelled: 'Geannuleerd' };
export const PRIORITY_LABELS = { critical: 'Kritiek', high: 'Hoog', medium: 'Gemiddeld', low: 'Laag' };

const COLUMNS = ['todo', 'in_progress', 'done', 'cancelled'];
const FLOW = ['todo', 'in_progress', 'done'];

const EMPTY_FORM = { engagement_id: '', title: '', priority: 'medium', due_date: '' };

function TaskFormModal({ open, onClose, engagements, onSaved }) {
  const [form, setForm] = useState(EMPTY_FORM);
  const [saving, setSaving] = useState(false);
  const [error, setError] = useState(null);

  useEffect(() => {
    if (!open) return;
    setError(null);
    setForm(EMPTY_FORM);
  }, [open]);

  const set = (k) => (e) => setForm((f) => ({ ...f, [k]: e.target.value }));

  const submit = async (e) => {
    e.preventDefault();
    setSaving(true);
    setError(null);
    try {
      await api.post('/tasks', { ...form, due_date: form.due_date || null });
      onSaved();
    } catch (err) {
      setError(err);
    } finally {
      setSaving(false);
    }
  };

  return (
    <Modal open={open} onClose={onClose} title="Nieuwe taak">
      <form onSubmit={submit} className="space-y-3">
        <ErrorBox error={error} />
        <Field label="Engagement *">
          <select className={inputCls} value={form.engagement_id} onChange={set('engagement_id')} required>
            <option value="">— Kies een engagement —</option>
            {engagements.map((e) => (
              <option key={e.id} value={e.id}>{e.title} — {e.client_name}</option>
            ))}
          </select>
        </Field>
        <Field label="Titel *">
          <input className={inputCls} value={form.title} onChange={set('title')} required autoFocus />
        </Field>
        <div className="grid grid-cols-2 gap-3">
          <Field label="Prioriteit">
            <select className={inputCls} value={form.priority} onChange={set('priority')}>
              {Object.entries(PRIORITY_LABELS).map(([k, v]) => <option key={k} value={k}>{v}</option>)}
            </select>
          </Field>
          <Field label="Deadline">
            <input type="date" className={inputCls} value={form.due_date} onChange={set('due_date')} />
          </Field>
        </div>
        <div className="flex justify-end gap-2 pt-1">
          <Btn type="button" variant="secondary" onClick={onClose}>Annuleren</Btn>
          <Btn type="submit" loading={saving}>Aanmaken</Btn>
        </div>
      </form>
    </Modal>
  );
}

function TaskCard({ task, onMove, onDelete }) {
  const today = new Date().toISOString().slice(0, 10);
  const overdue = task.due_date && task.due_date < today && task.status !== 'done' && task.status !== 'cancelled';
  const idx = FLOW.indexOf(task.status);

  return (
    <div className="bg-card border border-border-soft rounded-lg p-2.5 space-y-1.5">
      <div className="text-[13px] font-medium">{task.title}</div>
      <div className="text-[11px] text-muted truncate">{task.client_name} · {task.engagement_title}</div>
      <div className="flex items-center justify-between gap-2">
        <StatusBadge status={task.priority} labels={PRIORITY_LABELS} />
        {task.due_date && (
          <span className={`text-[11px] ${overdue ? 'text-red font-medium' : 'text-muted'}`}>
            {fmt.date(task.due_date)}
          </span>
        )}
      </div>
      <div className="flex items-center justify-between pt-1.5 border-t border-border-soft/50">
        <div className="flex gap-0.5">
          {idx > 0 && (
            <button
              onClick={() => onMove(task, FLOW[idx - 1])}
              className="p-1 rounded text-muted hover:text-text hover:bg-bg-soft"
              title={`Naar '${TASK_STATUS_LABELS[FLOW[idx - 1]]}'`}
            >
              <ArrowLeft className="w-3.5 h-3.5" />
            </button>
          )}
          {idx >= 0 && idx < FLOW.length - 1 && (
            <button
              onClick={() => onMove(task, FLOW[idx + 1])}
              className="p-1 rounded text-muted hover:text-text hover:bg-bg-soft"
              title={`Naar '${TASK_STATUS_LABELS[FLOW[idx + 1]]}'`}
            >
              <ArrowRight className="w-3.5 h-3.5" />
            </button>
          )}
        </div>
        <button
          onClick={() => onDelete(task)}
          className="p-1 rounded text-muted hover:text-red hover:bg-bg-soft"
          title="Verwijderen"
        >
          <Trash2 className="w-3.5 h-3.5" />
        </button>
      </div>
    </div>
  );
}

export default function Tasks() {
  const [data, setData] = useState(null);
  const [engagements, setEngagements] = useState([]);
  const [error, setError] = useState(null);
  const [modalOpen, setModalOpen] = useState(false);

  const load = () => {
    setError(null);
    api.get('/tasks').then(setData).catch(setError);
  };
  useEffect(load, []);
  useEffect(() => {
    api.get('/engagements').then(setEngagements).catch(() => { /* opties voor modal */ });
  }, []);

  const move = async (task, status) => {
    try {
      await api.post(`/tasks/${task.id}/status`, { status });
      load();
    } catch (err) {
      setError(err);
    }
  };

  const remove = async (task) => {
    if (!window.confirm(`Taak "${task.title}" verwijderen?`)) return;
    try {
      await api.del(`/tasks/${task.id}`);
      load();
    } catch (err) {
      setError(err);
    }
  };

  return (
    <div className="space-y-4 fade-in">
      <div className="flex items-center justify-between gap-3 flex-wrap">
        <div>
          <h1 className="text-xl font-bold tracking-tight">Taken</h1>
          <p className="text-[13px] text-muted mt-0.5">Kanban-overzicht van alle taken</p>
        </div>
        <Btn onClick={() => setModalOpen(true)}>
          <Plus className="w-4 h-4" /> Nieuwe taak
        </Btn>
      </div>

      {error && <ErrorBox error={error} onRetry={load} />}
      {!data && !error && <Spinner />}

      {data && data.length === 0 && (
        <EmptyState
          icon={CheckSquare}
          title="Nog geen taken"
          hint="Maak je eerste taak aan om te beginnen."
          action={<Btn onClick={() => setModalOpen(true)}><Plus className="w-4 h-4" /> Nieuwe taak</Btn>}
        />
      )}

      {data && data.length > 0 && (
        <div className="grid grid-cols-1 md:grid-cols-2 xl:grid-cols-4 gap-3 items-start">
          {COLUMNS.map((col) => {
            const colTasks = data.filter((t) => t.status === col);
            return (
              <div key={col} className="bg-bg-soft border border-border-soft rounded-xl p-2.5">
                <div className="flex items-center justify-between px-1 pb-2">
                  <span className="text-[12px] font-semibold">{TASK_STATUS_LABELS[col]}</span>
                  <Badge color="muted">{colTasks.length}</Badge>
                </div>
                <div className="space-y-2">
                  {colTasks.map((t) => (
                    <TaskCard key={t.id} task={t} onMove={move} onDelete={remove} />
                  ))}
                  {colTasks.length === 0 && (
                    <div className="text-center text-[11px] text-muted py-4">Geen taken</div>
                  )}
                </div>
              </div>
            );
          })}
        </div>
      )}

      <TaskFormModal
        open={modalOpen}
        onClose={() => setModalOpen(false)}
        engagements={engagements}
        onSaved={() => { setModalOpen(false); load(); }}
      />
    </div>
  );
}