#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# midiclock.py
#
"""Receive MIDI clock and print out current BPM.

MIDI clock (status 0xF8) is sent 24 times per quarter note by clock generators.

"""

import time
from collections import deque

from rtmidi.midiconstants import (TIMING_CLOCK, SONG_CONTINUE, SONG_START, SONG_STOP)
from rtmidi.midiutil import open_midiinput


class MIDIClockReceiver:
    def __init__(self, bpm=None):
        self.bpm = bpm if bpm is not None else 120.0
        self.sync = False
        self.running = True
        self._samples = deque()
        self._last_clock = None

    def __call__(self, event, data=None):
        msg, _ = event

        if msg[0] == TIMING_CLOCK:
            now = time.time()

            if self._last_clock is not None:
                self._samples.append(now - self._last_clock)

            self._last_clock = now

            if len(self._samples) > 24:
                self._samples.popleft()

            if len(self._samples) >= 2:
                self.bpm = 2.5 / (sum(self._samples) / len(self._samples))
                self.sync = True

        elif msg[0] in (SONG_CONTINUE, SONG_START):
            self.running = True
            print("START/CONTINUE received.")
        elif msg[0] == SONG_STOP:
            self.running = False
            print("STOP received.")


def main(args=None):
    clock = MIDIClockReceiver(float(args[0]) if args else None)

    try:
        m_in, port_name = open_midiinput(args[0] if args else None)
    except (EOFError, KeyboardInterrupt):
        return 1

    m_in.set_callback(clock)
    # Important: enable reception of MIDI Clock messages (status 0xF8)
    m_in.ignore_types(timing=False)

    try:
        print("Waiting for clock sync...")
        while True:
            time.sleep(1)

            if clock.running:
                if clock.sync:
                    print("%.2f bpm" % clock.bpm)
                else:
                    print("%.2f bpm (no sync)" % clock.bpm)

    except KeyboardInterrupt:
        pass
    finally:
        m_in.close_port()
        del m_in


if __name__ == '__main__':
    import sys
    sys.exit(main(sys.argv[1:]) or 0)