import React, { useEffect, useMemo, useRef, useState } from 'react';
import {
  Search,
  FileText,
  CheckSquare,
  ShoppingCart,
  X,
  Loader2,
  ArrowRight,
  CornerDownLeft,
} from 'lucide-react';
import { SearchHit } from '../lib/types';
import { api } from '../lib/api';

interface CommandPaletteProps {
  isOpen: boolean;
  onClose: () => void;
  onOpenDocument: (docId: string, blockId?: string) => void;
  onOpenTask: (taskId: string) => void;
  onOpenList: (listId: string) => void;
}

// Safely render snippet containing <mark>...</mark> without dangerouslySetInnerHTML
const SnippetRenderer: React.FC<{ snippet: string }> = ({ snippet }) => {
  const parts = useMemo(() => {
    if (!snippet) return [];
    return snippet.split(/(<mark>[\s\S]*?<\/mark>)/g);
  }, [snippet]);

  return (
    <span className="text-muted text-xs line-clamp-2 leading-relaxed">
      {parts.map((part, i) => {
        if (part.startsWith('<mark>') && part.endsWith('</mark>')) {
          const text = part.slice(6, -7);
          return (
            <mark
              key={i}
              className="bg-accent-dim text-accent font-semibold px-0.5 rounded"
            >
              {text}
            </mark>
          );
        }
        return <span key={i}>{part}</span>;
      })}
    </span>
  );
};

export const CommandPalette: React.FC<CommandPaletteProps> = ({
  isOpen,
  onClose,
  onOpenDocument,
  onOpenTask,
  onOpenList,
}) => {
  const [query, setQuery] = useState('');
  const [hits, setHits] = useState<SearchHit[]>([]);
  const [selectedIndex, setSelectedIndex] = useState(0);
  const [loading, setLoading] = useState(false);

  const inputRef = useRef<HTMLInputElement>(null);
  const debounceTimerRef = useRef<number | null>(null);

  // Group hits by category: Notizen, Aufgaben, Listen
  const groupedHits = useMemo(() => {
    const docs: SearchHit[] = [];
    const tasks: SearchHit[] = [];
    const lists: SearchHit[] = [];

    for (const h of hits) {
      if (h.type === 'document') {
        docs.push(h);
      } else if (h.type === 'thought') {
        tasks.push(h);
      } else if (h.type === 'list_item') {
        lists.push(h);
      }
    }

    return [
      { key: 'documents', label: 'Notizen', icon: FileText, items: docs },
      { key: 'tasks', label: 'Aufgaben', icon: CheckSquare, items: tasks },
      { key: 'lists', label: 'Listen', icon: ShoppingCart, items: lists },
    ].filter((g) => g.items.length > 0);
  }, [hits]);

  // Flattened array for simple up/down index navigation
  const flatHits = useMemo(() => {
    return groupedHits.flatMap((g) => g.items);
  }, [groupedHits]);

  // Focus input and reset on open
  useEffect(() => {
    if (isOpen) {
      setQuery('');
      setHits([]);
      setSelectedIndex(0);
      setTimeout(() => inputRef.current?.focus(), 50);
    }
  }, [isOpen]);

  // 150ms debounce search
  useEffect(() => {
    if (debounceTimerRef.current !== null) {
      window.clearTimeout(debounceTimerRef.current);
    }

    const trimmed = query.trim();
    if (!trimmed) {
      setHits([]);
      setLoading(false);
      setSelectedIndex(0);
      return;
    }

    setLoading(true);
    debounceTimerRef.current = window.setTimeout(async () => {
      try {
        const res = await api.searchAll(trimmed);
        setHits(res.hits || []);
        setSelectedIndex(0);
      } catch {
        setHits([]);
      } finally {
        setLoading(false);
      }
    }, 150);

    return () => {
      if (debounceTimerRef.current !== null) {
        window.clearTimeout(debounceTimerRef.current);
      }
    };
  }, [query]);

  // Keyboard navigation: ↑, ↓, Enter, Escape
  useEffect(() => {
    if (!isOpen) return;

    const handleKeyDown = (e: KeyboardEvent) => {
      if (e.key === 'Escape') {
        e.preventDefault();
        onClose();
        return;
      }

      if (flatHits.length === 0) return;

      if (e.key === 'ArrowDown') {
        e.preventDefault();
        setSelectedIndex((prev) => (prev + 1) % flatHits.length);
      } else if (e.key === 'ArrowUp') {
        e.preventDefault();
        setSelectedIndex((prev) => (prev - 1 + flatHits.length) % flatHits.length);
      } else if (e.key === 'Enter') {
        e.preventDefault();
        const selected = flatHits[selectedIndex];
        if (selected) {
          executeSelection(selected);
        }
      }
    };

    window.addEventListener('keydown', handleKeyDown);
    return () => window.removeEventListener('keydown', handleKeyDown);
  }, [isOpen, flatHits, selectedIndex]);

  const executeSelection = (hit: SearchHit) => {
    onClose();
    if (hit.type === 'document') {
      onOpenDocument(hit.docId || hit.id, hit.blockId);
    } else if (hit.type === 'thought') {
      onOpenTask(hit.id);
    } else if (hit.type === 'list_item') {
      if (hit.listId) {
        onOpenList(hit.listId);
      }
    }
  };

  if (!isOpen) return null;

  return (
    <div
      className="fixed inset-0 z-50 flex items-start justify-center p-0 sm:p-4 sm:pt-16 bg-black/60 backdrop-blur-xs animate-in fade-in duration-150"
      onClick={onClose}
    >
      {/* Search Modal Container */}
      <div
        className="
          w-full h-full bg-panel flex flex-col overflow-hidden shadow-2xl
          sm:h-auto sm:max-h-[80vh] sm:max-w-2xl sm:rounded-card sm:border sm:border-border
        "
        onClick={(e) => e.stopPropagation()}
      >
        {/* Top Input Bar */}
        <div className="flex items-center gap-2.5 px-4 py-3 border-b border-border bg-canvas/40 shrink-0">
          <Search className="w-5 h-5 text-accent shrink-0" />
          <input
            ref={inputRef}
            type="text"
            value={query}
            onChange={(e) => setQuery(e.target.value)}
            placeholder="Globale Suche in Notizen, Aufgaben und Listen…"
            className="flex-1 bg-transparent border-0 outline-none text-main placeholder-muted text-base sm:text-sm focus:ring-0 p-0"
          />
          {loading && <Loader2 className="w-4 h-4 animate-spin text-accent shrink-0" />}
          {query && !loading && (
            <button
              type="button"
              onClick={() => {
                setQuery('');
                setHits([]);
                inputRef.current?.focus();
              }}
              className="text-muted hover:text-main p-1"
              title="Eingabe leeren"
            >
              <X className="w-4 h-4" />
            </button>
          )}
          <button
            type="button"
            onClick={onClose}
            className="sm:hidden px-2 py-1 text-xs font-semibold text-accent"
          >
            Fertig
          </button>
        </div>

        {/* Results Container */}
        <div className="flex-1 overflow-y-auto p-2 space-y-4 min-h-[160px]">
          {query.trim() === '' ? (
            <div className="py-12 px-4 text-center text-xs text-muted space-y-1">
              <p className="font-semibold text-main">MindSift Globale Suche</p>
              <p>Tippe ein Stichwort ein, um alle Inhalte in Sekundenschnelle zu durchsuchen.</p>
            </div>
          ) : flatHits.length === 0 && !loading ? (
            <div className="py-12 px-4 text-center text-xs text-muted space-y-1">
              <p className="font-semibold text-main">Keine Treffer gefunden</p>
              <p>Keine Notizen, Aufgaben oder Listen-Einträge stimmen mit „{query}“ überein.</p>
            </div>
          ) : (
            groupedHits.map((group) => {
              const GroupIcon = group.icon;
              return (
                <div key={group.key} className="space-y-1">
                  <div className="flex items-center gap-1.5 px-2 py-1 text-[11px] font-bold text-accent uppercase tracking-wider">
                    <GroupIcon className="w-3.5 h-3.5" />
                    <span>{group.label}</span>
                  </div>

                  <div className="space-y-1">
                    {group.items.map((item) => {
                      const overallIndex = flatHits.indexOf(item);
                      const isSelected = overallIndex === selectedIndex;
                      return (
                        <div
                          key={item.id}
                          onClick={() => executeSelection(item)}
                          onMouseEnter={() => setSelectedIndex(overallIndex)}
                          className={`
                            px-3 py-2.5 rounded-btn flex items-start gap-2.5 transition-colors cursor-pointer border
                            ${
                              isSelected
                                ? 'bg-panel-elevated border-accent text-main'
                                : 'bg-canvas/50 border-transparent text-main hover:bg-panel-elevated'
                            }
                          `}
                        >
                          <div className="mt-0.5 shrink-0 text-base leading-none">
                            {item.icon || (item.type === 'document' ? '📝' : item.type === 'thought' ? '✅' : '🛒')}
                          </div>

                          <div className="flex-1 min-w-0 space-y-0.5">
                            <div className="flex items-center justify-between gap-2">
                              <span className="font-semibold text-xs truncate">
                                {item.title || 'Unbenannt'}
                              </span>
                              {isSelected && (
                                <span className="hidden sm:inline-flex items-center text-[10px] text-accent gap-0.5 shrink-0">
                                  <span>Öffnen</span>
                                  <CornerDownLeft className="w-3 h-3" />
                                </span>
                              )}
                            </div>

                            {item.snippet && (
                              <div>
                                <SnippetRenderer snippet={item.snippet} />
                              </div>
                            )}
                          </div>
                        </div>
                      );
                    })}
                  </div>
                </div>
              );
            })
          )}
        </div>

        {/* Footer Shortcut Bar (Desktop) */}
        <div className="hidden sm:flex items-center justify-between px-4 py-2 bg-canvas/40 border-t border-border text-[11px] text-muted shrink-0">
          <div className="flex items-center gap-3">
            <span>
              <kbd className="px-1 py-0.5 bg-panel border border-border rounded font-mono text-[10px] text-accent">↑</kbd>{' '}
              <kbd className="px-1 py-0.5 bg-panel border border-border rounded font-mono text-[10px] text-accent">↓</kbd> Navigieren
            </span>
            <span>
              <kbd className="px-1 py-0.5 bg-panel border border-border rounded font-mono text-[10px] text-accent">↵</kbd> Auswählen
            </span>
            <span>
              <kbd className="px-1 py-0.5 bg-panel border border-border rounded font-mono text-[10px] text-accent">Esc</kbd> Schließen
            </span>
          </div>

          <div>
            <span>{flatHits.length} Treffer</span>
          </div>
        </div>
      </div>
    </div>
  );
};