package kr.util;

import javax.sound.midi.*;
import java.util.ArrayList;

// TODO:
// - define and use a global symbolic constant for 60000000 (see convertTempo)

/**
 * Some utilities for MIDI (some stuff is used from javax.sound.midi)
 *
 * @version 1.4, 03/12/19
 * @author Florian Bomers
 */
public class MidiUtils {

    public final static int DEFAULT_TEMPO_MPQ = 500000; // 120bpm
    public final static int META_END_OF_TRACK_TYPE = 0x2F;
    public final static int META_TEMPO_TYPE = 0x51;


    /** return true if the passed message is Meta End Of Track */
    public static boolean isMetaEndOfTrack(MidiMessage midiMsg) {
	// first check if it is a META message at all
	if (midiMsg.getLength() != 3
	    || midiMsg.getStatus() != MetaMessage.META) {
	    return false;
	}
	// now get message and check for end of track
	byte[] msg = midiMsg.getMessage();
	return ((msg[1] & 0xFF) == META_END_OF_TRACK_TYPE) && (msg[2] == 0);
    }


    /** return if the given message is a meta tempo message */
    public static boolean isMetaTempo(MidiMessage midiMsg) {
	// first check if it is a META message at all
	if (midiMsg.getLength() != 6
	    || midiMsg.getStatus() != MetaMessage.META) {
	    return false;
	}
	// now get message and check for tempo
	byte[] msg = midiMsg.getMessage();
	// meta type must be 0x51, and data length must be 3
	return ((msg[1] & 0xFF) == META_TEMPO_TYPE) && (msg[2] == 3);
    }


    /** parses this message for a META tempo message and returns
     * the tempo in MPQ, or -1 if this isn't a tempo message
     */
    public static int getTempoMPQ(MidiMessage midiMsg) {
	// first check if it is a META message at all
	if (midiMsg.getLength() != 6
	    || midiMsg.getStatus() != MetaMessage.META) {
	    return -1;
	}
	byte[] msg = midiMsg.getMessage();
	if (((msg[1] & 0xFF) != META_TEMPO_TYPE) || (msg[2] != 3)) {
	    return -1;
	}
	int tempo =    (msg[5] & 0xFF)
	            | ((msg[4] & 0xFF) << 8)
	            | ((msg[3] & 0xFF) << 16);
	return tempo;
    }


    /**
     * converts<br>
     * 1 - MPQ-Tempo to BPM tempo<br>
     * 2 - BPM tempo to MPQ tempo<br>
     */
    public static double convertTempo(double tempo) {
	if (tempo <= 0) {
	    tempo = 1;
	}
	return ((double) 60000000l) / tempo;
    }


    /**
     * convert tick to microsecond with given tempo.
     * Does not take tempo changes into account.
     * Does not work for SMPTE timing!
     */
    public static long ticks2microsec(long tick, double tempoMPQ, int resolution) {
	return (long) (((double) tick) * tempoMPQ / resolution);
    }

    /**
     * convert tempo to microsecond with given tempo
     * Does not take tempo changes into account.
     * Does not work for SMPTE timing!
     */
    public static long microsec2ticks(long us, double tempoMPQ, int resolution) {
	// do not round to nearest tick
	//return (long) Math.round((((double)us) * resolution) / tempoMPQ);
	return (long) ((((double)us) * resolution) / tempoMPQ);
    }


    /**
     * Given a tick, convert to microsecond
     * @param cache tempo info and current tempo
     */
    public static long tick2microsecond(Sequence seq, long tick, TempoCache cache) {
	if (seq.getDivisionType() != Sequence.PPQ ) {
	    double seconds = ((double)tick / (double)(seq.getDivisionType() * seq.getResolution()));
	    return (long) (1000000 * seconds);
	}

	if (cache == null) {
	    cache = new TempoCache(seq);
	}

	int resolution = seq.getResolution();

    	long[] ticks = cache.ticks;
	int[] tempos = cache.tempos; // in MPQ
	int cacheCount = tempos.length;

	// optimization to not always go through entire list of tempo events
	int snapshotIndex = cache.snapshotIndex;
	int snapshotMicro = cache.snapshotMicro;

	// walk through all tempo changes and add time for the respective blocks
	long us = 0; // microsecond

	if (snapshotIndex <= 0
	    || snapshotIndex >= cacheCount
	    || ticks[snapshotIndex] > tick) {
	    snapshotMicro = 0;
	    snapshotIndex = 0;
	}
	if (cacheCount > 0) {
	    // this implementation needs a tempo event at tick 0!
	    int i = snapshotIndex + 1;
	    while (i < cacheCount && ticks[i] <= tick) {
		snapshotMicro += ticks2microsec(ticks[i] - ticks[i - 1], tempos[i - 1], resolution);
		snapshotIndex = i;
		i++;
	    }
	    us = snapshotMicro
		+ ticks2microsec(tick - ticks[snapshotIndex],
				 tempos[snapshotIndex],
				 resolution);
	}
	cache.snapshotIndex = snapshotIndex;
	cache.snapshotMicro = snapshotMicro;
	return us;
    }

    /**
     * Given a microsecond time, convert to tick.
     * returns tempo at the given time in cache.getCurrTempoMPQ
     */
    public static long microsecond2tick(Sequence seq, long micros, TempoCache cache) {
	if (seq.getDivisionType() != Sequence.PPQ ) {
	    double dTick = ( ((double) micros)
	                   * ((double) seq.getDivisionType())
	                   * ((double) seq.getResolution()))
	                   / ((double) 1000000);
	    long tick = (long) dTick;
	    if (cache != null) {
		cache.currTempo = (int) cache.getTempoMPQAt(tick);
	    }
	    return tick;
	}

	if (cache == null) {
	    cache = new TempoCache(seq);
	}
    	long[] ticks = cache.ticks;
	int[] tempos = cache.tempos; // in MPQ
	int cacheCount = tempos.length;

	int resolution = seq.getResolution();

	long us = 0; long tick = 0; int newReadPos = 0; int i = 1;

	// walk through all tempo changes and add time for the respective blocks
	// to find the right tick
	if (micros > 0 && cacheCount > 0) {
	    // this loop requires that the first tempo Event is at time 0
	    while (i < cacheCount) {
		long nextTime = us + ticks2microsec(ticks[i] - ticks[i - 1],
						    tempos[i - 1], resolution);
		if (nextTime > micros) {
		    break;
		}
		us = nextTime;
		i++;
	    }
	    tick = ticks[i - 1] + microsec2ticks(micros - us, tempos[i - 1], resolution);
	    //if (Printer.debug) Printer.debug("   -> convert back = " + (tick2microsecond(seq, tick, null) / 1000)+" microseconds");
	}
	cache.currTempo = tempos[i - 1];
	return tick;
    }


    /**
     * Binary search for the event indexes of the track
     *
     * @param tick - tick number of index to be found in array
     * @return index in track which is on or after "tick".
     *   if no entries are found that follow after tick, track.size() is returned
     */
    public static int tick2index(Track track, long tick) {
	int ret = 0;
	if (tick > 0) {
	    int low = 0;
	    int high = track.size() - 1;
	    while (low < high) {
		// take the middle event as estimate
		ret = (low + high) >> 1;
		// tick of estimate
		long t = track.get(ret).getTick();
		if (t == tick) {
		    break;
		} else if (t < tick) {
		    // estimate too low
		    if (low == high - 1) {
			// "or after tick"
			ret++;
			break;
		    }
		    low = ret;
		} else { // if (t>tick)
		    // estimate too high
		    high = ret;
		}
	    }
	}
	return ret;
    }


    public static class TempoCache {
    	long[] ticks;
	int[] tempos; // in MPQ
	// index in ticks/tempos at the snapshot
	int snapshotIndex = 0;
	// microsecond at the snapshot
	int snapshotMicro = 0;

	int currTempo; // MPQ, used as return value for microsecond2tick

	private boolean firstTempoIsFake = false;

	public TempoCache() {
	    // just some defaults, to prevents weird stuff
	    ticks = new long[1];
	    tempos = new int[1];
	    tempos[0] = DEFAULT_TEMPO_MPQ;
	    snapshotIndex = 0;
	    snapshotMicro = 0;
	}

	public TempoCache(Sequence seq) {
	    this();
	    refresh(seq);
	}


	public synchronized void refresh(Sequence seq) {
	    ArrayList list = new ArrayList();
	    Track[] tracks = seq.getTracks();
	    if (tracks.length > 0) {
	    	// tempo events only occur in track 0
	    	Track track = tracks[0];
	    	int c = track.size();
		for (int i = 0; i < c; i++) {
		    MidiEvent ev = track.get(i);
		    MidiMessage msg = ev.getMessage();
		    if (isMetaTempo(msg)) {
			// found a tempo event. Add it to the list
			list.add(ev);
		    }
		}
	    }
	    int size = list.size() + 1;
	    firstTempoIsFake = true;
	    if ((size > 1)
		&& (((MidiEvent) list.get(0)).getTick() == 0)) {
		// do not need to add an initial tempo event at the beginning
		size--;
		firstTempoIsFake = false;
	    }
	    ticks  = new long[size];
	    tempos = new int[size];
	    int e = 0;
	    if (firstTempoIsFake) {
		// add tempo 120 at beginning
		ticks[0] = 0;
		tempos[0] = DEFAULT_TEMPO_MPQ;
		e++;
	    }
	    for (int i = 0; i < list.size(); i++, e++) {
	    	MidiEvent evt = (MidiEvent) list.get(i);
		ticks[e] = evt.getTick();
		tempos[e] = getTempoMPQ(evt.getMessage());
	    }
	    snapshotIndex = 0;
	    snapshotMicro = 0;
	}

	public int getCurrTempoMPQ() {
	    return currTempo;
	}

	float getTempoMPQAt(long tick) {
	    return getTempoMPQAt(tick, -1.0f);
	}

	synchronized float getTempoMPQAt(long tick, float startTempoMPQ) {
	    for (int i = 0; i < ticks.length; i++) {
		if (ticks[i] > tick) {
		    if (i > 0) i--;
		    if (startTempoMPQ > 0 && i == 0 && firstTempoIsFake) {
			return startTempoMPQ;
		    }
		    return (float) tempos[i];
		}
	    }
	    return tempos[tempos.length - 1];
	}

    }
}
