import { useState, useEffect, useRef, useCallback } from 'react';
import { Link, useSearchParams } from 'react-router';
import { useClient } from 'hooks/useClient';
import { toast } from 'sonner';
import { MessageCircle, Send, Plus, RefreshCw, X } from 'lucide-react';
import { formatClock, soulseekPeerPath, PEER_PARAM, type SlskdConversation, type SlskdPrivateMessage } from './shared';

// Chat panel — private (1:1) messaging. GET /conversations lists the peers we have threads with; GET
// /conversations/{user}/messages returns a thread (polled while it's open). Sending POSTs a bare JSON
// string body to /conversations/{user}, matching slskd's [FromBody] string endpoint; viewing a thread
// PUTs /conversations/{user} to acknowledge (clear the unread badge). Basic version: a peer rail on the
// left, transcript + composer on the right.

const POLL_MS = 2500;

const isMine = (m: SlskdPrivateMessage) => (m.direction ?? '').toLowerCase() === 'out';

export const SoulseekChat = () => {
  const client = useClient();
  const [params, setParams] = useSearchParams();
  const selected = params.get(PEER_PARAM)?.trim() || null;
  const [conversations, setConversations] = useState<SlskdConversation[]>([]);
  const [messages, setMessages] = useState<SlskdPrivateMessage[]>([]);
  const [draft, setDraft] = useState('');
  const [peerName, setPeerName] = useState('');
  const scrollRef = useRef<HTMLDivElement>(null);

  const loadConversations = useCallback(async () => {
    try {
      setConversations(await client.get<SlskdConversation[]>('/soulseek/api/v0/conversations'));
    } catch {
      /* status panel surfaces connection errors */
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  useEffect(() => {
    loadConversations();
  }, [loadConversations]);

  // Poll the selected thread's messages while it's open, and acknowledge to clear its unread badge.
  useEffect(() => {
    if (!selected) {
      setMessages([]);
      return;
    }
    let cancelled = false;
    const tick = () =>
      client
        .get<SlskdPrivateMessage[]>(`/soulseek/api/v0/conversations/${encodeURIComponent(selected)}/messages`)
        .then((m) => {
          if (cancelled) return;
          setMessages(m);
          setConversations((prev) =>
            prev.map((c) => (c.username === selected ? { ...c, unAcknowledgedMessageCount: 0 } : c)),
          );
          client.put(`/soulseek/api/v0/conversations/${encodeURIComponent(selected)}`).catch(() => {});
        })
        .catch(() => {});
    tick();
    const timer = setInterval(tick, POLL_MS);
    return () => {
      cancelled = true;
      clearInterval(timer);
    };
    // useClient() is a fresh object each render — re-poll only when the selected peer changes.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [selected]);

  // Stick to the bottom as new messages arrive / when switching threads.
  useEffect(() => {
    const el = scrollRef.current;
    if (el) el.scrollTop = el.scrollHeight;
  }, [messages.length, selected]);

  // Starts a thread that isn't in the list yet, so it stays a form submit rather than a link: it adds the
  // peer locally *and then* opens it, and a link cannot express the "and then".
  const openPeer = (name: string) => {
    const target = name.trim();
    if (!target) return;
    setPeerName('');
    setConversations((prev) => (prev.some((c) => c.username === target) ? prev : [...prev, { username: target }]));
    setParams((prev) => {
      const next = new URLSearchParams(prev);
      next.set(PEER_PARAM, target);
      return next;
    });
  };

  const close = async (name: string) => {
    try {
      await client.delete(`/soulseek/api/v0/conversations/${encodeURIComponent(name)}`);
    } catch {
      /* optimistic — drop it locally regardless */
    }
    setConversations((prev) => prev.filter((c) => c.username !== name));
    // Closing the open thread leaves nothing open. `replace`, because the thread you just deleted is not
    // somewhere Back should return you to.
    if (name === selected) {
      setParams(
        (prev) => {
          const next = new URLSearchParams(prev);
          next.delete(PEER_PARAM);
          return next;
        },
        { replace: true },
      );
    }
  };

  const send = async () => {
    const text = draft.trim();
    if (!text || !selected) return;
    setDraft('');
    try {
      await client.post(`/soulseek/api/v0/conversations/${encodeURIComponent(selected)}`, text);
    } catch (err) {
      setDraft(text);
      toast.error(`Send failed: ${err instanceof Error ? err.message : String(err)}`);
    }
  };

  return (
    <div className="flex h-full overflow-hidden">
      {/* Peer rail */}
      <div className="flex w-56 shrink-0 flex-col border-r bg-muted/20">
        <div className="flex items-center justify-between px-3 py-2.5 text-xs font-medium uppercase tracking-wide text-muted-foreground">
          <span>Conversations</span>
          <button type="button" onClick={loadConversations} title="Refresh" className="rounded p-1 hover:bg-muted">
            <RefreshCw className="h-3 w-3" />
          </button>
        </div>
        <div className="flex flex-col gap-0.5 px-2">
          {conversations.length === 0 && (
            <p className="px-2 py-1 text-xs text-muted-foreground">No conversations yet.</p>
          )}
          {conversations.map((c) => {
            const active = c.username === selected;
            const unread = c.unAcknowledgedMessageCount ?? 0;
            return (
              <div
                key={c.username}
                className={`group flex items-center gap-1.5 rounded-lg px-2 py-1.5 text-sm transition-colors ${
                  active ? 'bg-primary/10 text-primary' : 'text-muted-foreground hover:bg-muted hover:text-foreground'
                }`}
              >
                {/* The close button is a sibling, never nested inside the anchor. */}
                <Link
                  to={soulseekPeerPath(c.username)}
                  className="flex min-w-0 flex-1 items-center gap-1.5 text-left"
                  aria-current={active ? 'true' : undefined}
                >
                  <MessageCircle className="h-3.5 w-3.5 shrink-0" />
                  <span className="truncate">{c.username}</span>
                </Link>
                {unread > 0 && !active && (
                  <span className="shrink-0 rounded-full bg-primary px-1.5 text-[10px] font-medium tabular-nums text-primary-foreground">
                    {unread}
                  </span>
                )}
                <button
                  type="button"
                  onClick={() => close(c.username)}
                  title={`Close ${c.username}`}
                  className="shrink-0 rounded p-0.5 text-muted-foreground opacity-0 transition group-hover:opacity-100 hover:bg-muted hover:text-foreground"
                >
                  <X className="h-3 w-3" />
                </button>
              </div>
            );
          })}
        </div>

        {/* Start a conversation */}
        <div className="mt-auto border-t p-2">
          <form
            onSubmit={(ev) => {
              ev.preventDefault();
              openPeer(peerName);
            }}
            className="flex items-center gap-1.5"
          >
            <input
              value={peerName}
              onChange={(ev) => setPeerName(ev.target.value)}
              placeholder="Message a user…"
              className="h-8 min-w-0 flex-1 rounded-md border bg-background px-2 text-sm outline-none focus:border-primary/50"
            />
            <button
              type="submit"
              disabled={!peerName.trim()}
              title="Open conversation"
              className="flex h-8 w-8 shrink-0 items-center justify-center rounded-md border text-muted-foreground hover:bg-accent hover:text-foreground disabled:opacity-40"
            >
              <Plus className="h-4 w-4" />
            </button>
          </form>
        </div>
      </div>

      {/* Transcript + composer */}
      <div className="flex min-w-0 flex-1 flex-col">
        {!selected ? (
          <div className="flex flex-1 flex-col items-center justify-center gap-2 text-center text-muted-foreground">
            <MessageCircle className="h-8 w-8" />
            <p className="text-sm">Pick a conversation, or message a user to start one.</p>
          </div>
        ) : (
          <>
            <div className="flex shrink-0 items-center gap-2 border-b px-4 py-2.5">
              <MessageCircle className="h-4 w-4 shrink-0 text-muted-foreground" />
              <span className="truncate font-medium">{selected}</span>
            </div>

            <div ref={scrollRef} className="min-h-0 flex-1 overflow-y-auto px-4 py-3">
              {messages.length === 0 ? (
                <p className="text-sm text-muted-foreground">No messages yet. Say hello.</p>
              ) : (
                <div className="flex flex-col gap-1.5">
                  {messages.map((m, i) => {
                    const mine = isMine(m);
                    return (
                      <div key={m.id || `${m.timestamp}-${i}`} className={`flex ${mine ? 'justify-end' : 'justify-start'}`}>
                        <div
                          className={`max-w-[80%] rounded-2xl px-3 py-1.5 text-sm ${
                            mine ? 'bg-primary text-primary-foreground' : 'bg-muted text-foreground'
                          }`}
                        >
                          <div className="break-words">{m.message}</div>
                          <div className={`mt-0.5 text-right text-[10px] tabular-nums ${mine ? 'text-primary-foreground/70' : 'text-muted-foreground'}`}>
                            {formatClock(m.timestamp)}
                          </div>
                        </div>
                      </div>
                    );
                  })}
                </div>
              )}
            </div>

            <form
              onSubmit={(ev) => {
                ev.preventDefault();
                send();
              }}
              className="flex shrink-0 items-center gap-2 border-t p-3"
            >
              <input
                value={draft}
                onChange={(ev) => setDraft(ev.target.value)}
                placeholder={`Message ${selected}…`}
                className="h-9 min-w-0 flex-1 rounded-lg border bg-background px-3 text-sm outline-none focus:border-primary/50 focus:ring-2 focus:ring-primary/20"
              />
              <button
                type="submit"
                disabled={!draft.trim()}
                className="flex h-9 w-9 shrink-0 items-center justify-center rounded-lg bg-primary text-primary-foreground transition hover:bg-primary/90 disabled:opacity-40"
              >
                <Send className="h-4 w-4" />
              </button>
            </form>
          </>
        )}
      </div>
    </div>
  );
};