'use client';

import { useStore } from '@/lib/store';
import { api } from '@/lib/api';

function formatDate(iso: string): string {
  const d = new Date(iso);
  const now = new Date();
  const diff = (now.getTime() - d.getTime()) / 1000;
  if (diff < 60) return 'just now';
  if (diff < 3600) return `${Math.floor(diff / 60)}m ago`;
  if (diff < 86400) return `${Math.floor(diff / 3600)}h ago`;
  if (diff < 172800) return 'yesterday';
  return d.toLocaleDateString('en-US', { month: 'short', day: 'numeric' });
}

function groupConversations(convs: { id: string; title: string; updated_at: string; created_at: string; message_count: number }[]) {
  const now = new Date();
  const groups: Record<string, typeof convs> = { today: [], yesterday: [], week: [], older: [] };
  convs.forEach(c => {
    const diff = (now.getTime() - new Date(c.updated_at).getTime()) / 86400000;
    if (diff < 1) groups.today.push(c);
    else if (diff < 2) groups.yesterday.push(c);
    else if (diff < 7) groups.week.push(c);
    else groups.older.push(c);
  });
  return groups;
}

export default function Sidebar({ onClose }: { onClose?: () => void }) {
  const { conversations, currentId, setCurrentId, setMessages, setConversations, setSidebarOpen } = useStore();

  async function newConversation() {
    const conv = await api.newConversation();
    const updated = await api.getConversations();
    setConversations(updated);
    setCurrentId(conv.id);
    setMessages([]);
    if (onClose) onClose();
  }

  async function loadConversation(id: string) {
    setCurrentId(id);
    setSidebarOpen(false);
  }

  async function deleteConv(e: React.MouseEvent, id: string) {
    e.stopPropagation();
    if (!confirm('Delete this conversation?')) return;
    await api.deleteConversation(id);
    const updated = await api.getConversations();
    setConversations(updated);
    if (currentId === id) { setCurrentId(null); setMessages([]); }
  }

  const groups = groupConversations(conversations);
  const labels: Record<string, string> = { today: 'Today', yesterday: 'Yesterday', week: 'This week', older: 'Older' };

  return (
    <div className="flex flex-col h-full">
      {/* Header */}
      <div className="p-3" style={{ borderBottom: '1px solid var(--border)' }}>
        <button
          onClick={newConversation}
          className="w-full flex items-center gap-2 px-3 py-2 rounded-lg text-sm font-medium transition-opacity hover:opacity-85"
          style={{ background: 'var(--accent)', color: '#e8f5ed', border: 'none', cursor: 'pointer' }}
        >
          <span style={{ fontSize: '16px', lineHeight: 1 }}>+</span>
          New conversation
        </button>
      </div>

      {/* Conversation list */}
      <div className="flex-1 overflow-y-auto py-1 px-2">
        {Object.entries(labels).map(([key, label]) => {
          const group = groups[key];
          if (!group.length) return null;
          return (
            <div key={key}>
              <div
                className="px-2 py-2 text-xs uppercase tracking-wider"
                style={{ color: 'var(--text3)', letterSpacing: '0.06em' }}
              >
                {label}
              </div>
              {group.map(c => (
                <div
                  key={c.id}
                  onClick={() => loadConversation(c.id)}
                  className="flex items-center gap-2 px-2 py-2 rounded-lg cursor-pointer mb-0.5 group"
                  style={{
                    background: c.id === currentId ? 'var(--bg3)' : 'transparent',
                  }}
                  onMouseEnter={e => { if (c.id !== currentId) (e.currentTarget as HTMLElement).style.background = 'var(--bg3)'; }}
                  onMouseLeave={e => { if (c.id !== currentId) (e.currentTarget as HTMLElement).style.background = 'transparent'; }}
                >
                  <div className="flex-1 min-w-0">
                    <div className="text-sm truncate" style={{ color: 'var(--text)' }} title={c.title}>
                      {c.title}
                    </div>
                    <div className="text-xs mt-0.5" style={{ color: 'var(--text3)' }}>
                      {formatDate(c.updated_at)}
                    </div>
                  </div>
                  <button
                    onClick={e => deleteConv(e, c.id)}
                    className="opacity-0 group-hover:opacity-100 px-1 py-0.5 rounded text-sm transition-opacity"
                    style={{ background: 'none', border: 'none', color: 'var(--text3)', cursor: 'pointer', minWidth: '24px', minHeight: '24px' }}
                  >
                    ×
                  </button>
                </div>
              ))}
            </div>
          );
        })}
        {conversations.length === 0 && (
          <div className="px-3 py-4 text-sm" style={{ color: 'var(--text3)' }}>
            No conversations yet
          </div>
        )}
      </div>
    </div>
  );
}