fn start => {
    | |

    sample_rate => sample_rate .

    0.125 => volume .
    240 => beats_per_minute .
    32 => length_in_beats .

    -9 note => c4 .
    -8 note => c4♯ .
        c4♯ => d4♭ .
    -7 note => d4 .
    -6 note => d4♯ .
        d4♯ => e4♭ .
    -5 note => e4 .
    -4 note => f4 .
    -3 note => f4♯ .
        f4♯ => g4♭ .
    -2 note => g4 .
    -1 note => g4♯ .
        g4♯ => a4♭ .
     0 note => a4 .
     1 note => a4♯ .
        a4♯ => b4♭ .
     2 note => b4 .

     c4  2 / => c3 .
     c4♯ 2 / => c3♯ .
     d4♭ 2 / => d3♭ .
     d4  2 / => d3 .
     d4♯ 2 / => d3♯ .
     e4♭ 2 / => e3♭ .
     e4  2 / => e3 .
     f4  2 / => f3 .
     f4♯ 2 / => f3♯ .
     g4♭ 2 / => g3♭ .
     g4  2 / => g3 .
     g4♯ 2 / => g3♯ .
     a4♭ 2 / => a3♭ .
     a4  2 / => a3 .
     a4♯ 2 / => a3♯ .
     b4♭ 2 / => b3♭ .
     b4  2 / => b3 .

     c3  2 / => c2 .
     c3♯ 2 / => c2♯ .
     d3♭ 2 / => d2♭ .
     d3  2 / => d2 .
     d3♯ 2 / => d2♯ .
     e3♭ 2 / => e2♭ .
     e3  2 / => e2 .
     f3  2 / => f2 .
     f3♯ 2 / => f2♯ .
     g3♭ 2 / => g2♭ .
     g3  2 / => g2 .
     g3♯ 2 / => g2♯ .
     a3♭ 2 / => a2♭ .
     a3  2 / => a2 .
     a3♯ 2 / => a2♯ .
     b3♭ 2 / => b2♭ .
     b3  2 / => b2 .

    global_timer_init => global_timer .

    osc_init => osc_a_timer osc_a_volume .
    osc_init => osc_b_timer osc_b_volume .
    osc_init => osc_c_timer osc_c_volume .

    global_timer
    osc_a_timer osc_a_volume
    osc_b_timer osc_b_volume
    osc_c_timer osc_c_volume
        loop
}

fn loop =>
    global_timer
    osc_a_timer osc_a_volume
    osc_b_timer osc_b_volume
    osc_c_timer osc_c_volume
{
    |
        sample_rate volume beats_per_minute length_in_beats
        c2 c2♯ d2♭ d2 d2♯ e2♭ e2 f2 f2♯ g2♭ g2 g2♯ a2♭ a2 a2♯ b2♭ b2
        c3 c3♯ d3♭ d3 d3♯ e3♭ e3 f3 f3♯ g3♭ g3 g3♯ a3♭ a3 a3♯ b3♭ b3
        c4 c4♯ d4♭ d4 d4♯ e4♭ e4 f4 f4♯ g4♭ g4 g4♯ a4♭ a4 a4♯ b4♭ b4 |

    global_timer global_timer_to_beat => beat .
    global_timer global_timer_update => global_timer .

    osc_a_timer voice osc_a_volume *
    osc_b_timer voice osc_b_volume *
        +
    osc_c_timer voice osc_c_volume *
        +
        volume *
        push_sample

    osc_a_timer
    beat pattern_mid
        osc_update
    => osc_a_timer .

    osc_b_timer
    beat pattern_low
        osc_update
    => osc_b_timer .
    0.75 => osc_a_volume .

    osc_c_timer
    beat pattern_low 2 /
        osc_update
    => osc_c_timer .
    0.25 => osc_b_volume .

    global_timer
    osc_a_timer osc_a_volume
    osc_b_timer osc_b_volume
    osc_c_timer osc_c_volume
        loop
}

fn voice => osc {
    | return _ . |

    osc osc_saw
        return
}

fn pattern_low => beat {
    |
        c2 c2♯ d2♭ d2 d2♯ e2♭ e2 f2 f2♯ g2♭ g2 g2♯ a2♭ a2 a2♯ b2♭ b2
        c3 c3♯ d3♭ d3 d3♯ e3♭ e3 f3 f3♯ g3♭ g3 g3♯ a3♭ a3 a3♯ b3♭ b3
        c4 c4♯ d4♭ d4 d4♯ e4♭ e4 f4 f4♯ g4♭ g4 g4♯ a4♭ a4 a4♯ b4♭ b4
        return _ . |

    beat 32 % match
        => beat if { | | beat 0 >= beat 12 < and } { | c3 |
            c3
        }
        => beat if { | | beat 12 >= beat 16 < and } { | e3 |
            e3
        }
        => beat if { | | beat 16 >= beat 28 < and } { | f3 |
            f3
        }
        => beat if { | | beat 28 >= beat 32 < and } { | e3 |
            e3
        }
        => _ { | |
            0
        }
    .
        return
}

fn pattern_mid => beat {
    |
        c2 c2♯ d2♭ d2 d2♯ e2♭ e2 f2 f2♯ g2♭ g2 g2♯ a2♭ a2 a2♯ b2♭ b2
        c3 c3♯ d3♭ d3 d3♯ e3♭ e3 f3 f3♯ g3♭ g3 g3♯ a3♭ a3 a3♯ b3♭ b3
        c4 c4♯ d4♭ d4 d4♯ e4♭ e4 f4 f4♯ g4♭ g4 g4♯ a4♭ a4 a4♯ b4♭ b4
        return _ . |

    beat 32 % match
        => beat if { | | beat 0 >= beat 14 < and } { | c4 g4 e4 d4 |
            beat 8 % match
                => beat if { | | beat 0 >= beat 3 < and } { | c4 |
                    c4
                }
                => beat if { | | beat 3 >= beat 4 < and } { | g4 |
                    g4
                }
                => beat if { | | beat 4 >= beat 6 < and } { | e4 |
                    e4
                }
                => beat if { | | beat 6 >= beat 8 < and } { | d4 |
                    d4
                }
            .
        }
        => beat if { | | beat 14 >= beat 16 < and } { | d4♯ |
            d4♯
        }
        => beat if { | | beat 16 >= beat 30 < and } { | d4 a4 f4 d4♯ |
            beat 8 % match
                => beat if { | | beat 0 >= beat 3 < and } { | d4 |
                    d4
                }
                => beat if { | | beat 3 >= beat 4 < and } { | a4 |
                    a4
                }
                => beat if { | | beat 4 >= beat 6 < and } { | f4 |
                    f4
                }
                => beat if { | | beat 6 >= beat 8 < and } { | d4♯ |
                    d4♯
                }
            .
        }
        => beat if { | | beat 30 >= beat 32 < and } { | e4 |
            e4
        }
        => _ { | |
            0
        }
    .
        return
}


# Infrastructure

fn note => distance_from_a4_in_half_steps {
    | return _ . |

    2 distance_from_a4_in_half_steps 12 / pow 440 *
        return
}

fn global_timer_init => {
    | return _ . |

    0 return
}

fn global_timer_to_beat => global_timer {
    |
        sample_rate beats_per_minute return _ . |

    global_timer sample_rate /
        beats_per_second *
        return
}

fn global_timer_update => timer {
    |
        sample_rate beats_per_minute length_in_beats return _ . |

    timer 1 + => timer .

    sample_rate beats_per_second / length_in_beats * => length_in_samples .

    timer length_in_samples >= match
        => done if { | | done 1 = } { | |
            exit
        }
        => _ { | timer |
            timer
        }
    .
        return
}

fn beats_per_second => {
    | beats_per_minute return _ . |

    beats_per_minute 60 /
        return
}

fn osc_init => {
    | return _ _ . |

    0 => osc_timer .
    1 => osc_volume .

    osc_timer osc_volume return
}

fn osc_update => osc_timer pitch {
    | sample_rate return _ . |

    pitch sample_rate / osc_timer + => osc_timer .

    osc_timer 1 >= match
        => must_wrap if { | | must_wrap 0 = } { | osc_timer | osc_timer }
        => must_wrap if { | | must_wrap 1 = } { | osc_timer | osc_timer 1 - }
    .
        return
}

fn osc_saw => osc_timer {
    | return _ . |

    osc_timer return
}