import { useState, useMemo, useRef, useEffect, useCallback } from 'react';
import { X, Sparkles, Search, Pin, Trash2 } from 'lucide-react';
import type { Session } from '../types';
import { useT } from '../hooks/useLocale';
import { SessionIcon } from './SessionIcon';
import { sessionDisplayName } from '../lib/sessionName';
import { relativeTime } from '../lib/relativeTime';

const PINNED_KEY = 'pinchchat-pinned-sessions';
const WIDTH_KEY = 'pinchchat-sidebar-width';
const MIN_WIDTH = 220;
const MAX_WIDTH = 480;
const DEFAULT_WIDTH = 288; // w-72

function getSavedWidth(): number {
  try {
    const v = localStorage.getItem(WIDTH_KEY);
    if (v) {
      const n = Number(v);
      if (n >= MIN_WIDTH && n <= MAX_WIDTH) return n;
    }
  } catch { /* noop */ }
  return DEFAULT_WIDTH;
}

function getPinnedSessions(): Set<string> {
  try {
    const raw = localStorage.getItem(PINNED_KEY);
    if (raw) return new Set(JSON.parse(raw) as string[]);
  } catch { /* noop */ }
  return new Set();
}

function savePinnedSessions(pinned: Set<string>) {
  try {
    localStorage.setItem(PINNED_KEY, JSON.stringify([...pinned]));
  } catch { /* noop */ }
}

interface Props {
  sessions: Session[];
  activeSession: string;
  onSwitch: (key: string) => void;
  onDelete: (key: string) => void;
  open: boolean;
  onClose: () => void;
}

export function Sidebar({ sessions, activeSession, onSwitch, onDelete, open, onClose }: Props) {
  const t = useT();
  const [filter, setFilter] = useState('');
  const [focusIdx, setFocusIdx] = useState(-1);
  const [pinned, setPinned] = useState(getPinnedSessions);
  const [width, setWidth] = useState(getSavedWidth);
  const [dragging, setDragging] = useState(false);
  const [confirmDelete, setConfirmDelete] = useState<string | null>(null);
  const searchRef = useRef<HTMLInputElement>(null);
  const listRef = useRef<HTMLDivElement>(null);
  const dragRef = useRef({ startX: 0, startW: 0 });

  // Drag-to-resize logic
  useEffect(() => {
    if (!dragging) return;
    const onMove = (e: MouseEvent | TouchEvent) => {
      const clientX = 'touches' in e ? e.touches[0].clientX : e.clientX;
      const newW = Math.min(MAX_WIDTH, Math.max(MIN_WIDTH, dragRef.current.startW + (clientX - dragRef.current.startX)));
      setWidth(newW);
    };
    const onUp = () => {
      setDragging(false);
      // persist on release
      localStorage.setItem(WIDTH_KEY, String(width));
    };
    document.addEventListener('mousemove', onMove);
    document.addEventListener('mouseup', onUp);
    document.addEventListener('touchmove', onMove);
    document.addEventListener('touchend', onUp);
    return () => {
      document.removeEventListener('mousemove', onMove);
      document.removeEventListener('mouseup', onUp);
      document.removeEventListener('touchmove', onMove);
      document.removeEventListener('touchend', onUp);
    };
  }, [dragging, width]);

  // Save width when it changes (debounced via drag end above, but also on unmount)
  useEffect(() => {
    return () => { try { localStorage.setItem(WIDTH_KEY, String(width)); } catch { /* noop */ } };
  }, [width]);

  const startDrag = useCallback((e: React.MouseEvent | React.TouchEvent) => {
    e.preventDefault();
    const clientX = 'touches' in e ? e.touches[0].clientX : e.clientX;
    dragRef.current = { startX: clientX, startW: width };
    setDragging(true);
  }, [width]);

  const togglePin = useCallback((key: string, e: React.MouseEvent) => {
    e.stopPropagation();
    setPinned(prev => {
      const next = new Set(prev);
      if (next.has(key)) next.delete(key);
      else next.add(key);
      savePinnedSessions(next);
      return next;
    });
  }, []);

  // Keyboard shortcut: Ctrl+K or Cmd+K to focus search when sidebar is open
  useEffect(() => {
    const handler = (e: KeyboardEvent) => {
      if ((e.metaKey || e.ctrlKey) && e.key === 'k') {
        e.preventDefault();
        searchRef.current?.focus();
      }
    };
    window.addEventListener('keydown', handler);
    return () => window.removeEventListener('keydown', handler);
  }, []);

  const updateFilter = useCallback((value: string) => {
    setFilter(value);
    setFocusIdx(-1);
  }, []);

  const filtered = useMemo(() => {
    let list = sessions;
    if (filter.trim()) {
      const q = filter.toLowerCase();
      list = sessions.filter(s => sessionDisplayName(s).toLowerCase().includes(q));
    }
    // Sort pinned sessions to top (preserving relative order within each group)
    const pinnedList = list.filter(s => pinned.has(s.key));
    const unpinnedList = list.filter(s => !pinned.has(s.key));
    // Sort each group by most recently updated
    const byRecent = (a: Session, b: Session) => (b.updatedAt || 0) - (a.updatedAt || 0);
    pinnedList.sort(byRecent);
    unpinnedList.sort(byRecent);
    return [...pinnedList, ...unpinnedList];
  }, [sessions, filter, pinned]);

  return (
    <>
      {open && <div className="fixed inset-0 bg-black/60 backdrop-blur-sm z-40 lg:hidden" onClick={onClose} />}
      <aside role="navigation" aria-label="Sessions" className={`fixed lg:relative top-0 left-0 h-full bg-[#1e1e24]/95 border-r border-white/8 z-50 transform ${dragging ? '' : 'transition-transform'} lg:translate-x-0 ${open ? 'translate-x-0' : '-translate-x-full'} flex flex-col backdrop-blur-xl`} style={{ width: `${width}px` }}>
        <div className="h-14 flex items-center justify-between px-4 border-b border-white/8">
          <div className="flex items-center gap-2">
            <div className="relative">
              <div className="absolute -inset-1.5 rounded-xl bg-gradient-to-r from-cyan-400/15 to-violet-500/15 blur-lg" />
              <div className="relative flex h-8 w-8 items-center justify-center rounded-xl border border-white/8 bg-zinc-800/50">
                <Sparkles className="h-4 w-4 text-cyan-200" />
              </div>
            </div>
            <span className="font-semibold text-sm text-zinc-200 tracking-wide">{t('sidebar.title')}</span>
          </div>
          <button onClick={onClose} className="lg:hidden p-1.5 rounded-xl hover:bg-white/5 text-zinc-400 transition-colors">
            <X size={16} />
          </button>
        </div>

        {/* Session search */}
        {sessions.length > 3 && (
          <div className="px-2 pt-2">
            <div className="relative">
              <Search size={14} className="absolute left-3 top-1/2 -translate-y-1/2 text-zinc-500" />
              <input
                ref={searchRef}
                type="text"
                value={filter}
                onChange={e => updateFilter(e.target.value)}
                placeholder={t('sidebar.search')}
                aria-label={t('sidebar.search')}
                className="w-full pl-8 pr-3 py-1.5 rounded-xl border border-white/8 bg-zinc-800/30 text-xs text-zinc-300 placeholder:text-zinc-500 outline-none focus:ring-1 focus:ring-cyan-400/30 transition-all"
              />
              {filter && (
                <button
                  onClick={() => updateFilter('')}
                  className="absolute right-2 top-1/2 -translate-y-1/2 text-zinc-500 hover:text-zinc-300"
                >
                  <X size={12} />
                </button>
              )}
            </div>
          </div>
        )}

        <div
          ref={listRef}
          className="flex-1 overflow-y-auto py-2 px-2"
          role="listbox"
          aria-label={t('sidebar.title')}
          tabIndex={0}
          onKeyDown={(e) => {
            const len = filtered.length;
            if (!len) return;
            if (e.key === 'ArrowDown') {
              e.preventDefault();
              const next = focusIdx < len - 1 ? focusIdx + 1 : 0;
              setFocusIdx(next);
              listRef.current?.querySelectorAll<HTMLButtonElement>('[role="option"]')[next]?.scrollIntoView({ block: 'nearest' });
            } else if (e.key === 'ArrowUp') {
              e.preventDefault();
              const prev = focusIdx > 0 ? focusIdx - 1 : len - 1;
              setFocusIdx(prev);
              listRef.current?.querySelectorAll<HTMLButtonElement>('[role="option"]')[prev]?.scrollIntoView({ block: 'nearest' });
            } else if (e.key === 'Enter' && focusIdx >= 0 && focusIdx < len) {
              e.preventDefault();
              onSwitch(filtered[focusIdx].key);
              onClose();
            } else if (e.key === 'Escape') {
              e.preventDefault();
              onClose();
            }
          }}
        >
          {sessions.length === 0 && (
            <div className="px-3 py-8 text-center text-zinc-500 text-sm">{t('sidebar.empty')}</div>
          )}
          {sessions.length > 0 && filtered.length === 0 && (
            <div className="px-3 py-6 text-center text-zinc-500 text-xs">{t('sidebar.noResults')}</div>
          )}
          {filtered.map((s, idx) => {
            const isActive = s.key === activeSession;
            const isFocused = idx === focusIdx;
            const isPinned = pinned.has(s.key);
            const isFirstUnpinned = !isPinned && idx > 0 && pinned.has(filtered[idx - 1].key);
            return (
              <div key={s.key}>
                {isFirstUnpinned && (
                  <div className="flex items-center gap-2 px-3 py-1.5 mt-1 mb-1">
                    <div className="flex-1 h-px bg-white/5" />
                  </div>
                )}
                <button
                  role="option"
                  aria-selected={isActive}
                  onClick={() => { onSwitch(s.key); onClose(); }}
                  onMouseEnter={() => setFocusIdx(idx)}
                  className={`group/item w-full flex items-center gap-3 px-3 py-2.5 rounded-2xl text-left text-sm transition-all mb-1 ${
                    isActive
                      ? 'bg-white/5 text-cyan-200 border border-white/8 shadow-[0_0_12px_rgba(34,211,238,0.08)]'
                      : s.isActive
                        ? 'bg-violet-500/5 text-violet-200 border border-violet-500/15 shadow-[0_0_10px_rgba(168,85,247,0.06)]'
                        : 'text-zinc-400 hover:bg-white/5 border border-transparent'
                  } ${isFocused && !isActive ? 'ring-1 ring-cyan-400/30' : ''}`}
                >
                  <div className="relative">
                    <SessionIcon session={s} isActive={s.isActive} isCurrentSession={isActive} />
                    {s.isActive && (
                      <span className="absolute -top-0.5 -right-0.5 h-2 w-2 rounded-full bg-violet-400 shadow-[0_0_8px_rgba(168,85,247,0.7)] animate-pulse" />
                    )}
                    {s.hasUnread && !isActive && (
                      <span className="absolute -top-0.5 -left-0.5 h-2 w-2 rounded-full bg-cyan-400 shadow-[0_0_8px_rgba(34,211,238,0.7)]" />
                    )}
                  </div>
                  <div className="flex-1 min-w-0">
                    <div className="flex items-center gap-1">
                      <span className="flex-1 truncate">{sessionDisplayName(s)}</span>
                      {(() => {
                        const rel = relativeTime(s.updatedAt);
                        return rel ? <span className="text-[10px] text-zinc-500 tabular-nums shrink-0">{rel}</span> : null;
                      })()}
                      <button
                        onClick={(e) => togglePin(s.key, e)}
                        className={`shrink-0 p-0.5 rounded-lg transition-all ${
                          isPinned
                            ? 'text-cyan-400 opacity-80 hover:opacity-100'
                            : 'text-zinc-600 opacity-0 group-hover/item:opacity-60 hover:!opacity-100 hover:text-zinc-400'
                        }`}
                        title={isPinned ? t('sidebar.unpin') : t('sidebar.pin')}
                        aria-label={isPinned ? t('sidebar.unpin') : t('sidebar.pin')}
                      >
                        <Pin size={12} className={isPinned ? 'fill-current' : ''} />
                      </button>
                      <button
                        onClick={(e) => { e.stopPropagation(); setConfirmDelete(s.key); }}
                        className="shrink-0 p-0.5 rounded-lg transition-all text-zinc-600 opacity-0 group-hover/item:opacity-60 hover:!opacity-100 hover:text-red-400"
                        title={t('sidebar.delete')}
                        aria-label={t('sidebar.delete')}
                      >
                        <Trash2 size={12} />
                      </button>
                      {s.messageCount != null && (
                        <span className={`text-[11px] px-2 py-0.5 rounded-full shrink-0 ${isActive ? 'bg-cyan-400/10 text-cyan-300' : 'bg-white/5 text-zinc-500'}`}>
                          {s.messageCount}
                        </span>
                      )}
                    </div>
                    {s.lastMessagePreview && (
                      <p className="text-[11px] text-zinc-500 truncate mt-0.5 leading-tight">{s.lastMessagePreview.replace(/\s+/g, ' ').slice(0, 80)}</p>
                    )}
                    {(() => {
                      if (!s.contextTokens) return null;
                      const pct = Math.min(100, ((s.totalTokens || 0) / s.contextTokens) * 100);
                      const barOpacity = Math.max(0.35, Math.min(1, pct / 100));
                      const barStyle = { width: `${pct}%`, backgroundColor: `rgba(56, 189, 248, ${barOpacity})` };
                      return (
                        <div className="flex items-center gap-1.5 mt-1">
                          <div className="flex-1 h-[3px] rounded-full bg-white/5 overflow-hidden">
                            <div className="h-full rounded-full" style={barStyle} />
                          </div>
                          <span className="text-[9px] text-zinc-500 tabular-nums shrink-0">{Math.round(pct)}%</span>
                        </div>
                      );
                    })()}
                  </div>
                </button>
              </div>
            );
          })}
        </div>
        {/* Footer with version */}
        <div className="px-4 py-3 border-t border-white/8 flex items-center justify-center gap-2">
          <span className="h-1.5 w-1.5 rounded-full bg-violet-300/60 shadow-[0_0_10px_rgba(168,85,247,0.5)]" />
          <span className="h-1.5 w-1.5 rounded-full bg-cyan-300/60 shadow-[0_0_10px_rgba(34,211,238,0.5)]" />
          <span className="h-1.5 w-1.5 rounded-full bg-indigo-300/50 shadow-[0_0_10px_rgba(99,102,241,0.4)]" />
          <span className="ml-1 text-[9px] text-zinc-600 select-all" title={`PinchChat v${__APP_VERSION__}`}>v{__APP_VERSION__}</span>
        </div>
        {/* Resize drag handle */}
        <div
          onMouseDown={startDrag}
          onTouchStart={startDrag}
          className={`hidden lg:block absolute top-0 right-0 w-1.5 h-full cursor-col-resize group/resize z-10 ${dragging ? 'bg-cyan-400/20' : 'hover:bg-cyan-400/15'} transition-colors`}
          role="separator"
          aria-orientation="vertical"
          aria-label="Resize sidebar"
          aria-valuenow={width}
          aria-valuemin={MIN_WIDTH}
          aria-valuemax={MAX_WIDTH}
        >
          <div className={`absolute top-1/2 -translate-y-1/2 right-0 w-0.5 h-8 rounded-full ${dragging ? 'bg-cyan-400/50' : 'bg-white/0 group-hover/resize:bg-cyan-400/30'} transition-colors`} />
        </div>
      </aside>
      {/* Prevent text selection while dragging */}
      {dragging && <div className="fixed inset-0 z-[60] cursor-col-resize" />}
      {/* Delete confirmation dialog */}
      {confirmDelete && (
        <>
          <div className="fixed inset-0 bg-black/60 backdrop-blur-sm z-[70]" onClick={() => setConfirmDelete(null)} />
          <div className="fixed top-1/2 left-1/2 -translate-x-1/2 -translate-y-1/2 z-[80] w-72 bg-[#1e1e24] border border-white/10 rounded-2xl p-5 shadow-2xl">
            <p className="text-sm text-zinc-300 mb-4">{t('sidebar.deleteConfirm')}</p>
            <div className="flex gap-2 justify-end">
              <button
                onClick={() => setConfirmDelete(null)}
                className="px-3 py-1.5 text-xs rounded-xl border border-white/10 text-zinc-400 hover:bg-white/5 transition-colors"
              >
                {t('sidebar.deleteCancel')}
              </button>
              <button
                onClick={() => { onDelete(confirmDelete); setConfirmDelete(null); }}
                className="px-3 py-1.5 text-xs rounded-xl bg-red-500/20 text-red-300 border border-red-500/20 hover:bg-red-500/30 transition-colors"
              >
                {t('sidebar.delete')}
              </button>
            </div>
          </div>
        </>
      )}
    </>
  );
}
