"use client";

import { useState } from "react";
import { Pill, Send } from "lucide-react";
import type { ChatMessage, Citation } from "@duoc-thu/shared-types";
import { ChatBubble, CitationCard, Card, Input, Button, cn } from "@duoc-thu/ui";
import { sendChatMessage } from "@duoc-thu/api-client";

function TypingIndicator() {
  return (
    <div className="inline-flex items-center gap-1 px-4 py-3" aria-label="Đang soạn câu trả lời">
      <span className="h-1.5 w-1.5 animate-bounce-dot rounded-full bg-muted-foreground/60" />
      <span className="h-1.5 w-1.5 animate-bounce-dot rounded-full bg-muted-foreground/60 [animation-delay:0.15s]" />
      <span className="h-1.5 w-1.5 animate-bounce-dot rounded-full bg-muted-foreground/60 [animation-delay:0.3s]" />
    </div>
  );
}

export interface ChatPanelProps {
  onCitationClick?: (citation: Citation) => void;
  className?: string;
}

const ERROR_MESSAGE =
  "Hệ thống tạm thời không phản hồi. Vui lòng thử lại — nếu vẫn lỗi, có thể dịch vụ tra cứu đang tạm ngưng.";

export function ChatPanel({ onCitationClick, className }: ChatPanelProps) {
  const [messages, setMessages] = useState<ChatMessage[]>([]);
  const [input, setInput] = useState("");
  const [isSending, setIsSending] = useState(false);
  // One id per chat session, so follow-ups ("còn trẻ em thì sao?") resolve
  // against the same conversation on the backend.
  const [conversationId] = useState(() =>
    typeof crypto !== "undefined" && crypto.randomUUID
      ? crypto.randomUUID()
      : `conv-${Date.now()}`
  );

  async function handleSubmit(event: React.FormEvent) {
    event.preventDefault();
    const content = input.trim();
    if (!content || isSending) return;

    const userMessage: ChatMessage = {
      id: `local-${messages.length}`,
      role: "user",
      content,
      createdAt: new Date().toISOString(),
    };
    setMessages((prev) => [...prev, userMessage]);
    setInput("");
    setIsSending(true);
    try {
      const response = await sendChatMessage(content, conversationId);
      setMessages((prev) => [...prev, response.message]);
    } catch {
      // Never leave the user staring at their own message with no reply: an
      // error is surfaced as a labelled bubble, not swallowed silently.
      setMessages((prev) => [
        ...prev,
        {
          id: `error-${messages.length}`,
          role: "assistant",
          content: ERROR_MESSAGE,
          createdAt: new Date().toISOString(),
        },
      ]);
    } finally {
      setIsSending(false);
    }
  }

  return (
    <Card className={cn("flex w-full flex-col overflow-hidden", className)}>
      <div className="flex min-h-[32rem] flex-1 flex-col gap-1 overflow-y-auto p-6">
        {messages.length === 0 && (
          <div className="m-auto max-w-sm text-center text-muted-foreground">
            <Pill className="mx-auto mb-2 h-10 w-10 text-primary" aria-hidden="true" />
            <p className="mb-1.5 text-lg font-semibold text-foreground">
              Hỏi về bất kỳ loại thuốc nào
            </p>
            <p className="text-[0.95rem]">
              Ví dụ: &ldquo;Liều dùng paracetamol cho người lớn?&rdquo; hoặc &ldquo;Chống chỉ
              định của amoxicillin là gì?&rdquo;
            </p>
          </div>
        )}
        {messages.map((message) => (
          <div key={message.id}>
            <ChatBubble message={message} />
            {message.citations && message.citations.length > 0 && (
              <div className="mb-4 mt-1.5 flex flex-wrap">
                {message.citations.map((citation) => (
                  <CitationCard
                    key={citation.drugName}
                    citation={citation}
                    onClick={onCitationClick ? () => onCitationClick(citation) : undefined}
                  />
                ))}
              </div>
            )}
          </div>
        ))}
        {isSending && <TypingIndicator />}
      </div>
      <form className="flex gap-2.5 border-t bg-muted/40 p-4" onSubmit={handleSubmit}>
        <Input
          value={input}
          onChange={(event) => setInput(event.target.value)}
          placeholder="Hỏi về một loại thuốc..."
          disabled={isSending}
          aria-label="Nhập câu hỏi"
        />
        <Button type="submit" disabled={isSending}>
          <Send className="h-4 w-4" aria-hidden="true" />
          {isSending ? "Đang gửi" : "Gửi"}
        </Button>
      </form>
    </Card>
  );
}