# import packages
using DigitalMusicology
using DataFrames
using Plots

# A4 is set to 440Hz
frequency_to_pitch(f) = 69 + 12 * log2(f / 440)

pitch_to_frequency(p) = 2^((p - 69) / 12) * 440

# the frequency of C4
pitch_to_frequency(60)

# the lowest midi note has a frequency of about 8Hz,
# the highest about 13kHz
# humans typically hear between 20Hz and 20kHz
pitch_to_frequency(0), pitch_to_frequency(127)

notes = midifilenotes("Run_To_The_Hills.mid")
head(notes)

notes[:key_sharps] |> unique

?midifilenotes

# this is a small pipeline
notes[:track] |> unique |> sort

# it is equivalent to
sort(unique(notes[:track]))

track_names = ["meta", "vocals", "vocal harmony", "guitar 1", "guitar 2", "bass", "drums"]

# drums in first bar
# there are 192 ticks per quarter note
notes[1:20, [:onset_wholes, :onset_ticks]]

# select the the instruments other than the drums
not_percussive_notes = notes[notes[:track] .!= 7, :]
head(not_percussive_notes)

# convert midi notes to pitch numbers
pitches = [note.pitch for note in not_percussive_notes[:pitch]]
pitches[1:10]

# plot pitch histogram
histogram(pitches, bins=collect(0:127))

# plot pitch class histogram
pitch_classes = [mod(p, 12) for p in pitches]
xticks = (collect(0:11) .+ 0.5, collect(0:11))
histogram(pitch_classes, bins=12, xticks=xticks)

# shift the histogram so that the most prominent note is in front
shifted_xticks = (collect(0:11) .+ 0.5, [mod(pc+7, 12) for pc in 0:11])
histogram(
    [mod(pc-7, 12) for pc in pitch_classes], 
    bins=12, 
    xticks=shifted_xticks
)

transform(p) = mod((p+4)*7, 12)
histogram(
    transform.(pitch_classes), 
    bins   = 12, 
    xticks = (transform.(collect(0:11)) .+ 0.5, (collect(0:11))), 
    xlim   = (0,12)
)

for track in 2:6
    display(
        histogram(
            [mod(note.pitch, 12) for note in notes[notes[:track] .== track, :pitch]], 
            bins   = collect(0:12),
            xticks = xticks,
            title  = track_names[track],
            xlim = (0,12)
        )
    )
end

onsets  = notes[notes[:track] .== 4, :onset_wholes]
offsets = notes[notes[:track] .== 4, :offset_wholes]
durations = offsets - onsets

[(d.num + 1) // d.den for d in durations]

for track in 2:6
    onsets  = notes[notes[:track] .== track, :onset_wholes]
    offsets = notes[notes[:track] .== track, :offset_wholes]
    durations = offsets - onsets
    display(histogram([(d.num + 1) // d.den for d in durations], title=track_names[track]))
end

for track in 2:6
    onsets  = notes[notes[:track] .== track, :onset_wholes]
    display(
        histogram(
            [o - floor(o) for o in onsets], 
            bins  = [x*1/16 for x in 0:16], 
            title = track_names[track]
        )
    )
end