from pyseq import *

class MonoFilter(PySeq):
    def init(self, n=1):
        self.ports=[self.createInOutPort() for i in range(n)]
        self.mt=MidiThread(self)
        self.mt.start()
        self.e=snd_seq_event()
        self.current=[]
        self.recent=None
    def callback(self, ev):
        pt=ev.dest.port
        ev.sendNow(self, pt)
        if ev.type==SND_SEQ_EVENT_NOTEON or ev.type==SND_SEQ_EVENT_NOTEOFF:
            dat=ev.getData()
            self.current=[e for e in self.current if e[1]!=dat.note]
            if ev.type==SND_SEQ_EVENT_NOTEON and dat.velocity>0:
                self.current.append((dat.channel, dat.note, dat.velocity))
                if self.recent!=None and self.recent!=dat.note:
                    self.e.setNoteOff(dat.channel, self.recent, 0)
                    self.e.sendNow(self, pt)
                self.recent=dat.note
            elif self.current and self.recent!=self.current[-1][1]:
                self.e.setNoteOn(*self.current[-1])
                self.e.sendNow(self, pt)
                self.recent=self.current[-1][1]

if __name__=='__main__':
    import time
    import sys
    if len(sys.argv)>1:
        n=int(sys.argv[1])
    else:
        n=1
    MonoFilter('MonoFilter', n)
    while 1: time.sleep(1)