import React, { useState, useEffect, useCallback } from 'react';
import { useAuth } from '../context/AuthContext';
import { useToast } from '../components/Toast';
import FillModal from '../components/FillModal';
import TemplateCard from '../components/TemplateCard';
import { apiFetch } from '../utils/api';

export default function Dashboard({ onNavigate }) {
  const { user } = useAuth();
  const toast = useToast();
  const isAdmin = user?.role === 'admin';
  const [templates, setTemplates] = useState([]);
  const [stats, setStats] = useState(null);
  const [search, setSearch] = useState('');
  const [loading, setLoading] = useState(true);
  const [fillTemplate, setFillTemplate] = useState(null);
  // Pagination für die Vorlagen-Table-Liste (10 Einträge pro Seite)
  const TEMPLATES_PER_PAGE = 10;
  const [currentPage, setCurrentPage] = useState(1);

  const fetchTemplates = useCallback(async () => {
    try {
      const res = await apiFetch('/templates');
      const data = await res.json();
      setTemplates(data);
    } catch (e) {
      console.error('Fehler beim Laden der Vorlagen:', e);
    } finally {
      setLoading(false);
    }
  }, []);

  const fetchStats = useCallback(async () => {
    if (!isAdmin) return;
    try {
      const res = await apiFetch('/stats');
      if (res.ok) {
        const data = await res.json();
        setStats(data);
      }
    } catch (e) {
      console.error('Fehler beim Laden der Statistiken:', e);
    }
  }, [isAdmin]);

  useEffect(() => {
    fetchTemplates();
    fetchStats();
    const interval = setInterval(fetchTemplates, 30000);
    return () => clearInterval(interval);
  }, [fetchTemplates, fetchStats]);

  // Alle Vorlagen sind für jeden User sichtbar (nicht mehr nach is_assignable gefiltert)
  const topTemplates = stats?.topTemplates || [];
  const filtered = templates.filter((t) =>
    t.name.toLowerCase().includes(search.toLowerCase()) ||
    (t.description || '').toLowerCase().includes(search.toLowerCase())
  );
  // Pagination: Suchwechsel setzt auf Seite 1 zurück
  const totalPages = Math.max(Math.ceil(filtered.length / TEMPLATES_PER_PAGE), 1);
  const pagedTemplates = filtered.slice((currentPage - 1) * TEMPLATES_PER_PAGE, currentPage * TEMPLATES_PER_PAGE);
  useEffect(() => {
    setCurrentPage(1);
  }, [search]);

  const handleSubmitTask = async (payload) => {
    const res = await apiFetch('/tasks', {
      method: 'POST',
      body: JSON.stringify({ ...payload, user_id: user.id }),
    });
    if (!res.ok) {
      const data = await res.json();
      throw new Error(data.error || 'Fehler beim Absenden');
    }
    setFillTemplate(null);
    toast.success('Aufgabe erfolgreich abgesendet!');
    fetchStats();
  };

  if (loading) {
    return (
      <div className="p-4 md:p-6 space-y-4">
        <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-4 gap-4">
          <div className="static-skeleton h-24 w-full"></div>
          <div className="static-skeleton h-24 w-full"></div>
          <div className="static-skeleton h-24 w-full"></div>
          <div className="static-skeleton h-24 w-full"></div>
        </div>
        <div className="static-skeleton h-10 w-full max-w-sm rounded-btn"></div>
        <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4">
          <div className="static-skeleton h-32 w-full"></div>
          <div className="static-skeleton h-32 w-full"></div>
          <div className="static-skeleton h-32 w-full"></div>
        </div>
      </div>
    );
  }

  return (
    <div className="p-4 md:p-6">
      {/* KPI-Sektion: 4 Statistik-Karten mit Delta + Fortschrittsbalken */}
      {isAdmin && stats && (
        <section aria-label="Kennzahlen" className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-4 gap-4 mb-10">
          {/* StatCard: Offene Aufgaben */}
          <div className="card bg-base-200 shadow-sm hover:shadow-md transition-all cursor-pointer" onClick={() => onNavigate?.('tasks')}>
            <div className="card-body p-5 space-y-3">
              <span className="text-xs font-medium opacity-60 uppercase tracking-wider">Offene Aufgaben</span>
              <div className="flex items-baseline gap-2">
                <span className="text-3xl font-bold tabular-nums">{stats.openTasks}</span>
                {stats.totalTasks > 0 && (
                  <span className="text-xs font-medium text-primary">
                    {Math.round((stats.openTasks / stats.totalTasks) * 100)}%
                  </span>
                )}
              </div>
              <div className="h-1 w-full bg-base-300 rounded-full overflow-hidden">
                <div className="h-full bg-primary transition-all duration-700" style={{ width: `${stats.totalTasks > 0 ? (stats.openTasks / stats.totalTasks) * 100 : 0}%` }} />
              </div>
            </div>
          </div>

          {/* StatCard: Abgeschlossen */}
          <div className="card bg-base-200 shadow-sm hover:shadow-md transition-all cursor-pointer" onClick={() => onNavigate?.('tasks')}>
            <div className="card-body p-5 space-y-3">
              <span className="text-xs font-medium opacity-60 uppercase tracking-wider">Abgeschlossen</span>
              <div className="flex items-baseline gap-2">
                <span className="text-3xl font-bold tabular-nums">{stats.completedTasks}</span>
                {stats.totalTasks > 0 && (
                  <span className="text-xs font-medium text-success">
                    {Math.round((stats.completedTasks / stats.totalTasks) * 100)}%
                  </span>
                )}
              </div>
              <div className="h-1 w-full bg-base-300 rounded-full overflow-hidden">
                <div className="h-full bg-success transition-all duration-700" style={{ width: `${stats.totalTasks > 0 ? (stats.completedTasks / stats.totalTasks) * 100 : 0}%` }} />
              </div>
            </div>
          </div>

          {/* StatCard: Aktive Nutzer */}
          <div className="card bg-base-200 shadow-sm hover:shadow-md transition-all cursor-pointer" onClick={() => onNavigate?.('users')}>
            <div className="card-body p-5 space-y-3">
              <span className="text-xs font-medium opacity-60 uppercase tracking-wider">Aktive Nutzer</span>
              <div className="flex items-baseline gap-2">
                <span className="text-3xl font-bold tabular-nums">{stats.activeUsers}</span>
                {stats.totalUsers > 0 && (
                  <span className="text-xs font-medium text-secondary">
                    von {stats.totalUsers}
                  </span>
                )}
              </div>
              <div className="h-1 w-full bg-base-300 rounded-full overflow-hidden">
                <div className="h-full bg-secondary transition-all duration-700" style={{ width: `${stats.totalUsers > 0 ? (stats.activeUsers / stats.totalUsers) * 100 : 0}%` }} />
              </div>
            </div>
          </div>

          {/* StatCard: AD-Nutzer */}
          <div className="card bg-base-200 shadow-sm hover:shadow-md transition-all cursor-pointer" onClick={() => onNavigate?.('users')}>
            <div className="card-body p-5 space-y-3">
              <span className="text-xs font-medium opacity-60 uppercase tracking-wider">AD-Nutzer</span>
              <div className="flex items-baseline gap-2">
                <span className="text-3xl font-bold tabular-nums">{stats.adUsers}</span>
              </div>
              <div className="h-1 w-full bg-base-300 rounded-full overflow-hidden">
                <div className="h-full bg-warning transition-all duration-700" style={{ width: `${stats.totalUsers > 0 ? (stats.adUsers / stats.totalUsers) * 100 : 0}%` }} />
              </div>
            </div>
          </div>
        </section>
      )}

      {/* Haupt-Grid: Vorlagen-Liste (links) | Graph-Card (rechts) — gleich große Spalten */}
      <div className="grid grid-cols-1 lg:grid-cols-2 gap-8 items-stretch">
        {/* Linke Spalte: Vorlagen als Table-Liste */}
        <section aria-label="Vorlagen" className="flex flex-col">
          <div className="flex flex-col sm:flex-row sm:items-center justify-between gap-4 mb-4">
            <h2 className="text-xl font-medium tracking-tight">{isAdmin ? 'Vorlagen' : 'Verfügbare Vorlagen'}</h2>
            <div className="form-control w-full sm:w-72">
              <input
                type="text"
                placeholder="Vorlagen durchsuchen..."
                className="input input-bordered w-full"
                value={search}
                onChange={(e) => setSearch(e.target.value)}
              />
            </div>
          </div>

          {templates.length === 0 ? (
            <div className="card bg-base-200 shadow-sm rounded-xl p-10 text-center">
              <p className="text-sm opacity-60">Keine Vorlagen vorhanden.</p>
            </div>
          ) : filtered.length === 0 ? (
            <div className="card bg-base-200 shadow-sm rounded-xl p-10 text-center">
              <p className="text-sm opacity-60">Keine Vorlagen für „{search}" gefunden.</p>
            </div>
          ) : (
            <>
              {/* Scrollbare Liste — flex-1 + min-h-0 (Pflicht für overflow in Flexbox),
                  damit die Liste innerhalb der Card-Höhe scrollt statt sie aufzuspannen */}
              <div className="card bg-base-200 shadow-sm rounded-xl overflow-hidden flex-1 flex flex-col min-h-[600px] max-h-[600px]">
                <div className="divide-y divide-base-300 flex-1 min-h-0 overflow-y-auto">
                  {pagedTemplates.map((tpl) => (
                    <TemplateCard
                      key={tpl.id}
                      template={tpl}
                      action={
                        <button
                          className="btn btn-primary btn-sm"
                          onClick={() => setFillTemplate(tpl)}
                        >
                          <svg xmlns="http://www.w3.org/2000/svg" className="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor"><path strokeLinecap="round" strokeLinejoin="round" strokeWidth="2" d="M14.752 11.168l-3.197-2.132A1 1 0 0010 9.87v4.263a1 1 0 001.555.832l3.197-2.132a1 1 0 000-1.664z" /><path strokeLinecap="round" strokeLinejoin="round" strokeWidth="2" d="M21 12a9 9 0 11-18 0 9 9 0 0118 0z" /></svg>
                          Starten
                        </button>
                      }
                    />
                  ))}
                </div>
              </div>

              {/* Pagination: 10 Vorlagen pro Seite */}
              {totalPages > 1 && (
                <div className="flex justify-center items-center gap-2 mt-4">
                  <button
                    className="btn btn-sm btn-outline"
                    disabled={currentPage <= 1}
                    onClick={() => setCurrentPage((p) => Math.max(p - 1, 1))}
                  >
                    « Zurück
                  </button>
                  <span className="text-sm opacity-70">
                    Seite {currentPage} von {totalPages}
                  </span>
                  <button
                    className="btn btn-sm btn-outline"
                    disabled={currentPage >= totalPages}
                    onClick={() => setCurrentPage((p) => Math.min(p + 1, totalPages))}
                  >
                    Weiter »
                  </button>
                </div>
              )}
            </>
          )}
        </section>

        {/* Rechte Spalte: Meistgenutzte Vorlagen als Column-Chart (Anteil in %) */}
        {isAdmin && topTemplates.length > 0 && (
          <section aria-label="Meistgenutzte Vorlagen" className="flex flex-col">
            {/* Header mit gleicher Mindesthöhe wie der Listen-Header (Suchbox = 48px),
                damit beide Cards auf derselben Höhe starten */}
            <div className="flex items-center justify-between mb-4 sm:min-h-[48px]">
              <h2 className="text-xl font-medium tracking-tight">Meistgenutzt</h2>
            </div>
            <div className="card bg-base-200 shadow-sm rounded-xl flex-1 flex flex-col">
              <div className="card-body p-5 flex-1 flex flex-col justify-center">
                {(() => {
                  // Prozentanteil jeder Vorlage an allen Task-Zuordnungen der Top-Liste
                  const totalCount = topTemplates.reduce((sum, t) => sum + (t.task_count || 0), 0);
                  if (totalCount === 0) return null;
                  return (
                    <div className="flex items-end justify-around gap-2 sm:gap-4 h-64 pt-2">
                      {topTemplates.map((t, idx) => {
                        const pct = Math.round(((t.task_count || 0) / totalCount) * 100);
                        return (
                          <div key={t.id} className="flex flex-col items-center justify-end h-full flex-1 min-w-0">
                            {/* Prozentwert über der Säule */}
                            <span className="text-xs font-semibold tabular-nums mb-1">{pct}%</span>
                            {/* Säule: Höhe proportional zum Prozentanteil, animiert per CSS-Transition */}
                            <div
                              className={`w-full max-w-16 rounded-t-md transition-all duration-700 ${idx === 0 ? 'bg-primary' : 'bg-primary/50'}`}
                              style={{ height: `${Math.max(pct, 2)}%` }}
                            />
                            {/* Beschriftung unter der Säule */}
                            <span className="text-[11px] opacity-70 truncate w-full text-center mt-2" title={t.name}>
                              {t.name}
                            </span>
                          </div>
                        );
                      })}
                    </div>
                  );
                })()}
              </div>
            </div>
          </section>
        )}
      </div>

      {fillTemplate && (
        <FillModal
          template={fillTemplate}
          onSubmit={handleSubmitTask}
          onClose={() => setFillTemplate(null)}
        />
      )}
    </div>
  );
}