'use client';

// Learner assistant — floating panel on the learner classroom (design doc
// §4.4). Single-agent Q&A over the courseware knowledge pack, with optional
// web search (shown as tool chips) and read-aloud via /api/tts (browser
// speech fallback). Deliberately self-contained: no multi-agent chat runtime.

import { useEffect, useRef, useState } from 'react';
import { Bot, Loader2, Search, Send, Sparkles, Volume2, VolumeX, X } from 'lucide-react';
import { Button } from '@/components/ui/button';
import { useI18n } from '@/lib/hooks/use-i18n';
import { useQaChat, type QaMessage } from '@/lib/qa/use-qa-chat';

export interface AssistantPanelProps {
  coursewareId: string;
}

export function AssistantPanel({ coursewareId }: AssistantPanelProps) {
  const { t } = useI18n();
  const [open, setOpen] = useState(false);
  const [input, setInput] = useState('');
  const scrollRef = useRef<HTMLDivElement>(null);
  const { messages, streaming, voiceOn, setVoiceOn, send, stop } = useQaChat({ coursewareId });

  useEffect(() => {
    scrollRef.current?.scrollTo({ top: scrollRef.current.scrollHeight });
  }, [messages, streaming]);

  const submit = () => {
    if (!input.trim() || streaming) return;
    void send(input);
    setInput('');
  };

  return (
    <>
      {/* Floating toggle */}
      <button
        onClick={() => setOpen(!open)}
        className="fixed bottom-5 right-5 z-50 w-12 h-12 rounded-full bg-violet-600 hover:bg-violet-500 text-white shadow-lg flex items-center justify-center transition-all"
        aria-label={t('qa.toggle')}
        title={t('qa.toggle')}
      >
        {open ? <X className="w-5 h-5" /> : <Bot className="w-5 h-5" />}
      </button>

      {open && (
        <div className="fixed bottom-20 right-5 z-50 w-[360px] max-w-[calc(100vw-2.5rem)] h-[480px] max-h-[70vh] flex flex-col rounded-2xl border border-border/70 bg-white dark:bg-zinc-900 shadow-2xl overflow-hidden">
          {/* Header */}
          <div className="flex items-center gap-2 px-4 py-3 border-b border-border/60 bg-violet-50/60 dark:bg-violet-950/30">
            <Sparkles className="w-4 h-4 text-violet-500" />
            <span className="font-medium text-sm flex-1">{t('qa.title')}</span>
            <button
              onClick={() => setVoiceOn(!voiceOn)}
              className="p-1.5 rounded-full hover:bg-white dark:hover:bg-zinc-800 text-gray-500"
              title={voiceOn ? t('qa.voiceOn') : t('qa.voiceOff')}
            >
              {voiceOn ? <Volume2 className="w-4 h-4" /> : <VolumeX className="w-4 h-4" />}
            </button>
          </div>

          {/* Messages */}
          <div ref={scrollRef} className="flex-1 overflow-y-auto px-3 py-3 space-y-3">
            {messages.length === 0 && (
              <div className="text-xs text-muted-foreground text-center py-8 px-4 leading-relaxed">
                {t('qa.welcome')}
              </div>
            )}
            {messages.map((message) => (
              <MessageBubble key={message.id} message={message} />
            ))}
            {streaming && (
              <div className="flex items-center gap-2 text-xs text-muted-foreground pl-2">
                <Loader2 className="w-3.5 h-3.5 animate-spin" />
                {t('qa.streaming')}
              </div>
            )}
          </div>

          {/* Input */}
          <div className="border-t border-border/60 p-3 flex items-center gap-2">
            <input
              value={input}
              onChange={(e) => setInput(e.target.value)}
              onKeyDown={(e) => {
                if (e.key === 'Enter') submit();
              }}
              placeholder={t('qa.placeholder')}
              disabled={streaming}
              className="flex-1 h-9 rounded-full border border-border/70 bg-muted/40 px-3.5 text-sm outline-none focus:ring-2 focus:ring-violet-500/40 disabled:opacity-60"
            />
            {streaming ? (
              <Button size="icon" variant="outline" onClick={stop} className="shrink-0">
                <X className="w-4 h-4" />
              </Button>
            ) : (
              <Button size="icon" onClick={submit} disabled={!input.trim()} className="shrink-0">
                <Send className="w-4 h-4" />
              </Button>
            )}
          </div>
        </div>
      )}
    </>
  );
}

function MessageBubble({ message }: { message: QaMessage }) {
  const { t } = useI18n();
  const isUser = message.role === 'user';

  if (isUser) {
    return (
      <div className="flex justify-end">
        <div className="max-w-[85%] rounded-2xl rounded-br-md bg-violet-600 text-white px-3.5 py-2 text-sm whitespace-pre-wrap break-words">
          {message.content}
        </div>
      </div>
    );
  }

  const toolSearch = message.toolEvents?.find((e) => e.tool === 'web_search' && e.status === 'done');

  return (
    <div className="flex justify-start">
      <div className="max-w-[92%] space-y-2">
        {toolSearch && (
          <div className="flex items-center gap-1.5 text-[11px] text-muted-foreground bg-muted/50 rounded-full px-2.5 py-1 w-fit">
            <Search className="w-3 h-3" />
            {t('qa.searched')}
            {toolSearch.error ? `（${toolSearch.error}）` : ''}
          </div>
        )}
        <div className="rounded-2xl rounded-bl-md bg-muted/50 dark:bg-zinc-800 px-3.5 py-2 text-sm whitespace-pre-wrap break-words">
          {message.content || <span className="text-muted-foreground">…</span>}
          {message.error && (
            <div className="mt-1.5 text-xs text-red-500">{t('qa.error')}: {message.error}</div>
          )}
        </div>
        {message.sources && message.sources.length > 0 && (
          <div className="flex flex-wrap gap-1">
            {message.sources.slice(0, 3).map((source) => (
              <span
                key={source.sceneId}
                className="text-[10px] text-muted-foreground bg-muted/60 border border-border/50 rounded-full px-2 py-0.5"
                title={`${t('qa.sceneRef')} #${source.order}`}
              >
                《{source.title}》
              </span>
            ))}
          </div>
        )}
      </div>
    </div>
  );
}