"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { toast } from "sonner";
import { useTranslations } from "next-intl";
import { Send } from "lucide-react";
import { Button } from "@/components/ui/button";
import { Textarea } from "@/components/ui/textarea";
import { cn } from "@/lib/utils";

type Message = {
  id: string;
  content: string;
  senderId: string;
  createdAt: string;
};

export function MessageThread({
  conversationId,
  currentUserId,
}: {
  conversationId: string;
  currentUserId: string;
}) {
  const t = useTranslations("messages");
  const [messages, setMessages] = useState<Message[]>([]);
  const [loading, setLoading] = useState(true);
  const [content, setContent] = useState("");
  const [sending, setSending] = useState(false);
  const bottomRef = useRef<HTMLDivElement>(null);

  const load = useCallback(async () => {
    const res = await fetch(`/api/v1/conversations/${conversationId}/messages`);
    if (res.ok) {
      const data = (await res.json()) as { messages: Message[] };
      setMessages(data.messages);
    }
    setLoading(false);
  }, [conversationId]);

  useEffect(() => {
    void load();
    const interval = setInterval(() => { void load(); }, 5000);
    return () => clearInterval(interval);
  }, [load]);

  useEffect(() => {
    bottomRef.current?.scrollIntoView({ behavior: "smooth" });
  }, [messages.length]);

  async function send() {
    if (!content.trim()) return;
    setSending(true);
    try {
      const res = await fetch(`/api/v1/conversations/${conversationId}/messages`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ content: content.trim() }),
      });
      if (!res.ok) {
        const err = await res.json().catch(() => ({})) as { error?: string };
        toast.error(err.error ?? t("sendFailed"));
        return;
      }
      setContent("");
      await load();
    } finally {
      setSending(false);
    }
  }

  return (
    <div className="flex flex-col h-full">
      <div className="flex-1 overflow-y-auto space-y-3 p-4">
        {loading ? (
          <p className="text-sm text-muted-foreground">{t("loading")}</p>
        ) : messages.length === 0 ? (
          <p className="text-sm text-muted-foreground text-center py-8">{t("noMessagesYet")}</p>
        ) : (
          messages.map((m) => {
            const isOwn = m.senderId === currentUserId;
            return (
              <div key={m.id} className={cn("flex", isOwn ? "justify-end" : "justify-start")}>
                <div
                  className={cn(
                    "max-w-[70%] rounded-2xl px-4 py-2 text-sm whitespace-pre-wrap",
                    isOwn ? "bg-primary text-primary-foreground" : "bg-muted"
                  )}
                >
                  {m.content}
                </div>
              </div>
            );
          })
        )}
        <div ref={bottomRef} />
      </div>
      <div className="border-t p-3 flex gap-2 items-end">
        <Textarea
          value={content}
          onChange={(e) => setContent(e.target.value)}
          onKeyDown={(e) => {
            if (e.key === "Enter" && !e.shiftKey) {
              e.preventDefault();
              void send();
            }
          }}
          placeholder={t("placeholder")}
          rows={1}
          className="resize-none"
        />
        <Button size="icon" onClick={() => { void send(); }} disabled={!content.trim() || sending}>
          <Send className="h-4 w-4" />
        </Button>
      </div>
    </div>
  );
}