import { useEffect, useMemo, useRef } from "react";
import { Music2, X } from "lucide-react";
import { Button } from "./Button";
import styles from "./LyricsPanel.module.css";

type LyricsPanelProps = {
  title?: string;
  artist?: string;
  plain?: string;
  synced?: string;
  instrumental?: boolean;
  positionMs: number;
  loading?: boolean;
  error?: string;
  onClose: () => void;
};

type SyncedLine = {
  timeMs: number;
  text: string;
};

function parseSynced(value?: string) {
  if (!value) return [] as SyncedLine[];
  return value
    .split(/\r?\n/)
    .map((line) => {
      const match = line.match(/^\[(\d{1,2}):(\d{2})(?:[.:](\d{1,3}))?\](.*)$/);
      if (!match) return undefined;
      const minutes = Number(match[1]);
      const seconds = Number(match[2]);
      const fraction = match[3] || "0";
      const millis = fraction.length === 3
        ? Number(fraction)
        : fraction.length === 2
          ? Number(fraction) * 10
          : Number(fraction) * 100;
      return {
        timeMs: (minutes * 60 + seconds) * 1000 + millis,
        text: match[4].trim(),
      };
    })
    .filter((line): line is SyncedLine => Boolean(line));
}

export function LyricsPanel({
  title,
  artist,
  plain,
  synced,
  instrumental,
  positionMs,
  loading,
  error,
  onClose,
}: LyricsPanelProps) {
  const lines = useMemo(() => parseSynced(synced), [synced]);
  const activeIndex = useMemo(() => {
    let active = -1;
    for (let index = 0; index < lines.length; index += 1) {
      if (lines[index].timeMs <= positionMs + 120) active = index;
      else break;
    }
    return active;
  }, [lines, positionMs]);
  const containerRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    if (activeIndex < 0 || !containerRef.current) return;
    const active = containerRef.current.querySelector(
      `[data-line="${activeIndex}"]`,
    );
    active?.scrollIntoView({ block: "center", behavior: "smooth" });
  }, [activeIndex]);

  return (
    <aside className={styles.panel} aria-label="Lyrics">
      <header>
        <div>
          <span>LYRICS</span>
          <strong>{title || "Now playing"}</strong>
          <small>{artist}</small>
        </div>
        <Button variant="ghost" size="icon-sm" onClick={onClose} aria-label="Close lyrics">
          <X size={16} />
        </Button>
      </header>
      <div className={styles.body} ref={containerRef}>
        {loading ? <div className={styles.empty}>Loading lyrics…</div> : null}
        {error ? <div className={styles.error}>{error}</div> : null}
        {!loading && !error && instrumental ? (
          <div className={styles.empty}><Music2 size={22} /> Instrumental track</div>
        ) : null}
        {!loading && !error && lines.length ? (
          <div className={styles.synced}>
            {lines.map((line, index) => (
              <p
                key={`${line.timeMs}-${index}`}
                data-line={index}
                className={index === activeIndex ? styles.active : undefined}
              >
                {line.text || "♪"}
              </p>
            ))}
          </div>
        ) : null}
        {!loading && !error && !lines.length && plain ? (
          <div className={styles.plain}>{plain}</div>
        ) : null}
        {!loading && !error && !instrumental && !lines.length && !plain ? (
          <div className={styles.empty}>No lyrics found for this track.</div>
        ) : null}
      </div>
    </aside>
  );
}