dwi converter

-- make global functions local for faster lookup
local table = table
local append, concat = table.insert, table.concat
local string = string
local sub, gsub, lower = string.sub, string.gsub, string.lower
local find, match, gmatch = string.find, string.match, string.gmatch
local ipairs, pairs = ipairs, pairs

local function file_search(filter, dir_path)
    local function c_in(value, tab)
        for _, v in pairs(tab) do
            if v == value then return true end
        end
        return false
    end

    function string:split(sep)
        local sep, fields = sep or ":", {}
        local pattern = string.format("([^%s]+)", sep)
        self:gsub(pattern, function(c) fields[#fields+1] = c end)
        return fields
    end

    local fs = require 'lfs'
    local filter = string.lower(filter) or "*"
    local dir_path = dir_path or fs.currentdir()
    local extensions = filter:split(";")

    local files = {}
    for _, path in ipairs(dir_path:split(";")) do
        for f in fs.dir(path) do
            if f ~= "." and f ~= ".." then
                local attr = fs.attributes(path..'\\'..f)
                if attr.mode == "file" then
                    if filter=="*" or
                    c_in(lower(f:match('%.%w*$')), extensions) then
                        append(files, {path = path..'\\', name = f})
                    end
                elseif attr.mode == "directory" then
                    local subf = file_search(filter, path..'\\'..f)
                    for _, v in ipairs(subf) do
                        append(files, {path = v.path, name = v.name})
                    end
                end
            end
        end
    end
    return files
end

local function processMeasure(measure)
    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',
    }
    local beat_notes = {''} -- reserve beat_notes[1] for opening tag if necessary
    local note_count = 0

    for note in measure:gmatch('%d%d%d%d') do
        append(beat_notes, note_lookup_table[note])
        append(beat_notes, '') -- for possible note padding
        note_count = note_count + 1
    end

    if note_count == 4 then
        for i=3, 9, 2 do beat_notes[i] = '0' end -- add appropriate note padding
    elseif note_count == 8 then
    elseif note_count == 12 then
        for i=3, 25, 2 do beat_notes[i] = '0' end
        beat_notes[1] = '['; append(beat_notes, ']')
    elseif note_count == 16 then
        beat_notes[1] = '('; append(beat_notes, ')')
    elseif note_count == 24 then
        beat_notes[1] = '['; append(beat_notes, ']')
    elseif note_count == 32 then
        for i=3, 65, 2 do beat_notes[i] = '0' end
        beat_notes[1] = '{'; append(beat_notes, '}')
    elseif note_count == 48 then
        for i=3, 97, 2 do beat_notes[i] = '000' end
        beat_notes[1] = '`'; append(beat_notes, '\'')
    elseif note_count == 64 then
        beat_notes[1] = '{'; append(beat_notes, '}')
    elseif note_count == 96 then
        for i=3, 193, 2 do beat_notes[i] = '0' end
        beat_notes[1] = '`'; append(beat_notes, '\'')
    elseif note_count == 192 then
        beat_notes[1] = '`'; append(beat_notes, '\'')
    else
        return nil -- invalid note count
    end

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

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local function smToDwi(full_path)
    -- open sm file to read contents into string
    local sm_file
    do
        local tmp = io.open(full_path)
        sm_file = tmp:read('*a')
        tmp:close()
    end

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

    local changebpm = sm_file:getFieldContents('BPMS')
    local start_bpm
    do -- separate first bpm and bpm changes
        start_bpm = changebpm:match('%d+%.?%d*%s*=%s*(%d+%.?%d*)')
        local _, idx = changebpm:find('%d+%.?%d*%s*=%s*%d+%.?%d*%s*,')

        if idx then changebpm = changebpm:sub(idx + 1)
        else changebpm = '' end
    end

    if changebpm then -- multiply all measures by 4 to convert to beats
        changebpm = changebpm:gsub('(%d+%.?%d*)(%s*=%s*%d+%.?%d*,?)', function(beat, bpm)
            return string.format('%.3f', beat * 4)..bpm
        end)
    end

    -- process common .sm file fields
    local file_contents = {}
    append(file_contents, '#TITLE:'         .. sm_file:getFieldContents('TITLE')                    .. ';\n')
    append(file_contents, '#ARTIST:'        .. sm_file:getFieldContents('ARTIST')                   .. ';\n')
    append(file_contents, '#FILE:'          .. sm_file:getFieldContents('MUSIC')                    .. ';\n')
    append(file_contents, '#BPM:'           .. start_bpm                                            .. ';\n')
    append(file_contents, '#GAP:'           .. tonumber(sm_file:getFieldContents('OFFSET')) * -1000 .. ';\n')
    append(file_contents, '#SAMPLESTART:'   .. sm_file:getFieldContents('SAMPLESTART')              .. ';\n')
    append(file_contents, '#SAMPLELENGTH:'  .. sm_file:getFieldContents('SAMPLELENGTH')             .. ';\n\n')
    if changebpm then
        append(file_contents, '#CHANGEBPM:' .. changebpm                                            .. ';\n')
    end
    append(file_contents, '#SINGLE:MANIAC:1:\n')

    sm_file = sm_file:match(':.+$') -- extract start of note data to end of file

    for measure in sm_file:gmatch('.-[,;]') do
        append(file_contents, processMeasure(measure))
    end

    do -- save converted file
        local contents = concat(file_contents)
        local dwi_file = io.open(full_path:gsub('%.%w*$', '.dwi'), 'w')
        dwi_file:write(contents..'\n')
        dwi_file:close()
    end
end

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for _, file in ipairs(file_search('.sm;.ssc;.ds')) do
    smToDwi(file.path .. file.name)
end