package com.evsuite.abrp;

import java.util.List;
import java.util.Locale;
import java.util.regex.Pattern;

/**
 * What the Overview shows as playing, out of the media sessions the head unit publishes
 * ({@link NowPlayingWatcher}): the session that plays, the one updated last when several do, and
 * when none plays the one paused last. Sessions without any text are passed over (Bluetooth leaves
 * an empty one behind when the phone stops). The text is cleaned: CarPlay's YouTube titles lose
 * their trailing video ID, and the radio, whose title is the station and whose artist field is the
 * station's own text, shows that text with the station below. Shown on screen only; nothing here
 * is logged or sent. Android-free and unit-tested.
 */
final class NowPlaying {

    enum Source { BLUETOOTH, CARPLAY, RADIO, OTHER }

    /** android.media.session.PlaybackState's codes, mirrored to stay Android-free. */
    static final int STATE_PAUSED = 2, STATE_PLAYING = 3, STATE_FAST_FORWARDING = 4, STATE_REWINDING = 5,
            STATE_BUFFERING = 6, STATE_SKIPPING_TO_PREVIOUS = 9, STATE_SKIPPING_TO_NEXT = 10,
            STATE_SKIPPING_TO_QUEUE_ITEM = 11;

    private static final int MAX_TEXT = 200;
    /** A YouTube video ID in brackets at the end of a title, as CarPlay passes them on. */
    private static final Pattern VIDEO_ID = Pattern.compile("\\s*\\[[A-Za-z0-9_-]{11}\\]$");
    private static final Pattern SPACES = Pattern.compile("\\s+");

    private NowPlaying() {}

    /** One media session as last seen. Times in the platform's elapsed-realtime milliseconds. */
    static final class Session {
        String packageName;
        int state;
        String title, artist;
        /** -1 when the session says no position. */
        long positionMs = -1;
        long positionUpdatedAt;
        float speed = 1f;
        /** 0 when unknown (the radio). */
        long durationMs;
        /** A file or content URI for the cover, when the session names one (Bluetooth does). */
        String artUri;
    }

    /** What to show. {@code subtitle} may be null; {@code session} is where it came from. */
    static final class Track {
        final Source source;
        final String title, subtitle;
        final boolean playing;
        final Session session;

        Track(Source source, String title, String subtitle, boolean playing, Session session) {
            this.source = source;
            this.title = title;
            this.subtitle = subtitle;
            this.playing = playing;
            this.session = session;
        }

        /** Where the song is at {@code now}, or -1 when the session gives no position. */
        long positionAt(long now) {
            if (session.positionMs < 0) return -1;
            long at = session.positionMs;
            if (playing && session.positionUpdatedAt > 0 && now > session.positionUpdatedAt) {
                at += (long) ((now - session.positionUpdatedAt) * session.speed);
            }
            if (session.durationMs > 0) at = Math.min(at, session.durationMs);
            return Math.max(0, at);
        }

        /** How far through the song, from 0 to 1, or -1 without a length or position (the radio). */
        float progressAt(long now) {
            long at = positionAt(now);
            if (at < 0 || session.durationMs <= 0) return -1f;
            return Math.min(1f, at / (float) session.durationMs);
        }
    }

    static Track pick(List<Session> sessions) {
        Session best = null;
        boolean bestPlaying = false;
        if (sessions != null) {
            for (Session s : sessions) {
                if (s == null || (!playing(s.state) && s.state != STATE_PAUSED)) continue;
                if (clean(s.title) == null && clean(s.artist) == null) continue;
                boolean p = playing(s.state);
                if (best == null || (p && !bestPlaying)
                        || (p == bestPlaying && s.positionUpdatedAt > best.positionUpdatedAt)) {
                    best = s;
                    bestPlaying = p;
                }
            }
        }
        if (best == null) return null;
        Source source = source(best.packageName);
        String title = clean(best.title), artist = clean(best.artist);
        if (source == Source.RADIO) {
            // The station is the title; its own text (song, programme) comes as the artist.
            if (artist != null) return new Track(source, artist, title, bestPlaying, best);
            return new Track(source, title, null, bestPlaying, best);
        }
        if (title == null) return new Track(source, artist, null, bestPlaying, best);
        return new Track(source, title, artist, bestPlaying, best);
    }

    static boolean playing(int state) {
        switch (state) {
            case STATE_PLAYING: case STATE_FAST_FORWARDING: case STATE_REWINDING: case STATE_BUFFERING:
            case STATE_SKIPPING_TO_PREVIOUS: case STATE_SKIPPING_TO_NEXT: case STATE_SKIPPING_TO_QUEUE_ITEM:
                return true;
            default:
                return false;
        }
    }

    /** Which source a session's app is: the ones seen on the owner's car, the rest as "other". */
    static Source source(String packageName) {
        if (packageName == null) return Source.OTHER;
        String p = packageName.toLowerCase(Locale.ROOT);
        if (p.equals("com.android.bluetooth")) return Source.BLUETOOTH;
        if (p.contains("allgo") || p.contains("carplay")) return Source.CARPLAY;
        if (p.contains("radio")) return Source.RADIO;
        return Source.OTHER;
    }

    /** Trimmed, one line, without a trailing video ID, at most 200 characters; null when empty. */
    static String clean(String text) {
        if (text == null) return null;
        String s = SPACES.matcher(text).replaceAll(" ").trim();
        s = VIDEO_ID.matcher(s).replaceAll("").trim();
        if (s.isEmpty()) return null;
        return s.length() > MAX_TEXT ? s.substring(0, MAX_TEXT - 1) + "…" : s;
    }
}