import { useState, useEffect, useRef } from 'react';
import {
  LayoutDashboard, Server, FlaskConical, Brain,
  TrendingUp, Users, Database, Swords, DollarSign, Settings, Trophy, Medal,
  PanelLeftClose, PanelLeftOpen,
} from 'lucide-react';
import { useGameStore, type ActivePage } from '@/store';

const NAV_ITEMS: { page: ActivePage; label: string; icon: typeof LayoutDashboard; era?: string }[] = [
  { page: 'dashboard', label: 'Dashboard', icon: LayoutDashboard },
  { page: 'infrastructure', label: 'Infrastructure', icon: Server },
  { page: 'research', label: 'Research', icon: FlaskConical },
  { page: 'models', label: 'Models', icon: Brain },
  { page: 'market', label: 'Market', icon: TrendingUp },
  { page: 'finance', label: 'Finance', icon: DollarSign },
  { page: 'talent', label: 'Talent', icon: Users, era: 'scaleup' },
  { page: 'data', label: 'Data', icon: Database, era: 'scaleup' },
  { page: 'competitors', label: 'Competitors', icon: Swords, era: 'scaleup' },
  { page: 'achievements', label: 'Achievements', icon: Trophy },
  { page: 'leaderboard', label: 'Leaderboard', icon: Medal },
  { page: 'settings', label: 'Settings', icon: Settings },
];

function getInitialCollapsed(): boolean {
  try {
    const stored = localStorage.getItem('ai-tycoon-sidebar-collapsed');
    if (stored !== null) return stored === 'true';
    return window.innerWidth < 1280;
  } catch { return false; }
}

export function Sidebar() {
  const activePage = useGameStore((s) => s.activePage);
  const setActivePage = useGameStore((s) => s.setActivePage);
  const companyName = useGameStore((s) => s.meta.companyName);
  const era = useGameStore((s) => s.meta.currentEra);
  const [collapsed, setCollapsed] = useState(getInitialCollapsed);

  const eraOrder = ['startup', 'scaleup', 'bigtech', 'agi'];
  const currentEraIdx = eraOrder.indexOf(era);

  const seenEraRef = useRef(era);
  const [newPages, setNewPages] = useState<Set<string>>(new Set());

  useEffect(() => {
    if (era !== seenEraRef.current) {
      const oldIdx = eraOrder.indexOf(seenEraRef.current);
      const newIdx = eraOrder.indexOf(era);
      if (newIdx > oldIdx) {
        const newlyVisible = NAV_ITEMS
          .filter(item => item.era && eraOrder.indexOf(item.era) > oldIdx && eraOrder.indexOf(item.era) <= newIdx)
          .map(item => item.page);
        setNewPages(prev => new Set([...prev, ...newlyVisible]));
      }
      seenEraRef.current = era;
    }
  }, [era]);

  const handleNavClick = (page: ActivePage) => {
    setActivePage(page);
    setNewPages(prev => {
      const next = new Set(prev);
      next.delete(page);
      return next;
    });
  };

  const toggleCollapse = () => {
    setCollapsed(prev => {
      const next = !prev;
      localStorage.setItem('ai-tycoon-sidebar-collapsed', String(next));
      return next;
    });
  };

  return (
    <aside className={`${collapsed ? 'w-16' : 'w-56'} bg-surface-900 border-r border-surface-700 flex flex-col h-screen transition-all duration-200`}>
      <div className={`${collapsed ? 'px-2 py-3' : 'p-4'} border-b border-surface-700 flex items-center ${collapsed ? 'justify-center' : 'justify-between'}`}>
        {!collapsed && (
          <div className="min-w-0">
            <h1 className="text-lg font-bold text-accent-light truncate">{companyName}</h1>
            <span className="text-xs text-surface-400 uppercase tracking-wider">
              {era === 'startup' ? 'Startup' : era === 'scaleup' ? 'Scale-up' : era === 'bigtech' ? 'Big Tech' : 'AGI Era'}
            </span>
          </div>
        )}
        <button onClick={toggleCollapse} className="text-surface-400 hover:text-surface-200 shrink-0 p-1" aria-label={collapsed ? 'Expand sidebar' : 'Collapse sidebar'}>
          {collapsed ? <PanelLeftOpen size={18} /> : <PanelLeftClose size={18} />}
        </button>
      </div>

      <nav className="flex-1 py-2 overflow-y-auto">
        {NAV_ITEMS.map(({ page, label, icon: Icon, era: requiredEra }) => {
          if (requiredEra && eraOrder.indexOf(requiredEra) > currentEraIdx) return null;

          const isActive = activePage === page;
          const isNew = newPages.has(page);
          const showDivider = page === 'talent' || page === 'achievements';
          return (
            <div key={page}>
              {showDivider && <div className={`border-t border-surface-700 my-1 ${collapsed ? 'mx-2' : 'mx-4'}`} />}
              <button
                onClick={() => handleNavClick(page)}
                className={`w-full flex items-center ${collapsed ? 'justify-center px-2' : 'gap-3 px-4'} py-2.5 text-sm transition-colors ${
                  isActive
                    ? 'bg-accent/10 text-accent-light border-r-2 border-accent'
                    : 'text-surface-300 hover:bg-surface-800 hover:text-surface-100'
                }`}
                title={collapsed ? label : undefined}
              >
                <Icon size={18} />
                {!collapsed && label}
                {!collapsed && isNew && (
                  <span className="ml-auto text-[10px] font-bold bg-accent text-white px-1.5 py-0.5 rounded">NEW</span>
                )}
                {collapsed && isNew && (
                  <span className="absolute top-0 right-0 w-1.5 h-1.5 bg-accent rounded-full" />
                )}
              </button>
            </div>
          );
        })}
      </nav>

      <div className={`${collapsed ? 'px-2 py-3 text-center' : 'p-4'} border-t border-surface-700 text-xs text-surface-500`}>
        {collapsed ? 'v0.1' : 'AI Tycoon v0.1'}
      </div>
    </aside>
  );
}