dwi converter

local sm_file

local note_lookup_table = {
    ['1000'] = '4',    ['0100'] = '2',
    ['0010'] = '8',    ['0001'] = '6',
    ['1100'] = '1',    ['1010'] = '7',
    ['1001'] = 'B',    ['0110'] = 'A',
    ['0101'] = '3',    ['0011'] = '9',
    ['1110'] = '<81>', ['0111'] = '<83>',
    ['1101'] = '<61>', ['1011'] = '<8B>',
    ['1111'] = '<19>', ['0000'] = '0',
}

function string:getField(field)
    local _, idx = self:find('#' .. field:upper() .. ':')
    local str = self:match('%b:;', idx)
    return str:sub(2, #str - 1)
end

local function processMeasure(measure)
    local beat_notes = {''}
    local note_count = 0
    for note in measure:gmatch('%d%d%d%d') do
        beat_notes[#beat_notes+1] = note_lookup_table[note]
        beat_notes[#beat_notes+1] = ''
        note_count = note_count + 1
    end

    if note_count == 4 then
        for i=3, 9, 2 do beat_notes[i] = '0' end
    elseif note_count == 8 then
    elseif note_count == 12 then
        for i=3, 25, 2 do beat_notes[i] = '0' end
        beat_notes[1], beat_notes[#beat_notes+1] = '[', ']'
    elseif note_count == 16 then
        beat_notes[1], beat_notes[#beat_notes+1] = '(', ')'
    elseif note_count == 24 then
        beat_notes[1], beat_notes[#beat_notes+1] = '[', ']'
    elseif note_count == 32 then
        for i=3, 65, 2 do beat_notes[i] = '0' end
        beat_notes[1], beat_notes[#beat_notes+1] = '{', '}'
    elseif note_count == 48 then
        for i=3, 97, 2 do beat_notes[i] = '000' end
        beat_notes[1], beat_notes[#beat_notes+1] = '`', '\''
    elseif note_count == 64 then
        beat_notes[1], beat_notes[#beat_notes+1] = '{', '}'
    elseif note_count == 96 then
        for i=3, 193, 2 do beat_notes[i] = '0' end
        beat_notes[1], beat_notes[#beat_notes+1] = '`', '\''
    elseif note_count == 192 then
        beat_notes[1], beat_notes[#beat_notes+1] = '`', '\''
    else
        return nil
    end

    return table.concat(beat_notes) .. '\n'
end

local sm_filename = 'test'
local tmp = io.open(sm_filename .. '.sm')
sm_file = tmp:read('*a')
tmp:close()

local title = sm_file:getField('TITLE')
local artist = sm_file:getField('ARTIST')
local file = sm_file:getField('MUSIC')
local gap = tonumber(sm_file:getField('OFFSET')) * -1000
local sample_start = sm_file:getField('SAMPLESTART')
local sample_length = sm_file:getField('SAMPLELENGTH')
local changebpm = sm_file:getField('BPMS')
local note_data, idx = sm_file:getField('NOTES')

local start_bpm = changebpm:match('%d*%.?%d*%s*=%s*(%d+%.?%d+)')
if start_bpm == nil then end

local _, idx = changebpm:find('%d*%.?%d*%s*=%s*%d+%.?%d+%s*,')
if idx then
    changebpm = changebpm:sub(idx + 1)
else
    changebpm = '' end

local changebpm_str = {}
if changebpm ~= '' then
    for beat, bpm, comma in changebpm:gmatch('(%d*%.?%d*)%s*(=%s*%d+%.?%d*)(,?)') do
        changebpm_str[#changebpm_str+1] = string.format("%.3f", tonumber(beat) * 4)..bpm
        if comma ~= '' then changebpm_str[#changebpm_str+1] = ',' end
    end
end

local file_contents = {}
file_contents[#file_contents+1] = '#TITLE:'         .. sm_file:getField('TITLE')                    .. ';\n'
file_contents[#file_contents+1] = '#ARTIST:'        .. sm_file:getField('ARTIST')                   .. ';\n'
file_contents[#file_contents+1] = '#FILE:'          .. sm_file:getField('MUSIC')                    .. ';\n'
file_contents[#file_contents+1] = '#BPM:'           .. start_bpm                                    .. ';\n'
file_contents[#file_contents+1] = '#GAP:'           .. tonumber(sm_file:getField('OFFSET')) * -1000 .. ';\n'
file_contents[#file_contents+1] = '#SAMPLESTART:'   .. sm_file:getField('SAMPLESTART')              .. ';\n'
file_contents[#file_contents+1] = '#SAMPLELENGTH:'  .. sm_file:getField('SAMPLELENGTH')             .. ';\n\n'
if changebpm ~= '' then
    file_contents[#file_contents+1] = '#CHANGEBPM:' .. table.concat(changebpm_str)                  .. ';\n'
end
file_contents[#file_contents+1] = '#SINGLE:MANIAC:1:\n'

local _, idx = sm_file:find('%d+%.%d+%s*%:', idx)
sm_file = sm_file:sub(idx + 1)

for measure in sm_file:gmatch('.-[,;]') do
    file_contents[#file_contents+1] = processMeasure(measure)
end

local dwi_file = io.open(sm_filename .. '.dwi', 'w')
dwi_file:write(table.concat(file_contents)..'\n')
dwi_file:close()