Genkhord chords.txt transpose script

-- Compatibility: Lua-5.1
function split(str, pat)
   local t = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pat
   local last_end = 1
   local s, e, cap = str:find(fpat, 1)
   while s do
      if s ~= 1 or cap ~= "" then
     table.insert(t,cap)
      end
      last_end = e+1
      s, e, cap = str:find(fpat, last_end)
   end
   if last_end <= #str then
      cap = str:sub(last_end)
      table.insert(t, cap)
   end
   return t
end


-- transpose function main
function transposeChordStr(chordSrc, keyShift)
    local chordTable = { "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B" }
    local chordKeywordTable = { "C#", "D#", "F#", "G#", "A#", "C", "D", "E", "F", "G", "A", "B" }
    local chordKeyIndexTable = { 1, 3, 6, 8, 10, 0, 2, 4, 5, 7, 9, 11 }

    local chordOut = ""
    local iSrc = 1
    while iSrc <= #chordSrc do
        -- replace chord if possible
        local chordReplaced = false
        for iToken, chordToken in pairs(chordKeywordTable) do
            local iStart, iEnd = string.find(chordSrc, chordToken, iSrc, true)
            if iStart == iSrc then
                local newChord = chordTable[(chordKeyIndexTable[iToken] + keyShift) % 12 + 1]
                chordOut = chordOut .. newChord
                iSrc = iSrc + #chordToken
                chordReplaced = true
                break
            end
        end
        --
        if not chordReplaced then
            chordOut = chordOut .. chordSrc:sub(iSrc, iSrc)
            iSrc = iSrc + 1
        end
    end
    return chordOut
end



-- parse command line options
local chordFilePath = "chords.txt"
local keyShift = 0
if #arg == 1 then
    keyShift = tonumber(arg[1])
elseif #arg == 2 then
    chordFilePath = arg[1]
    keyShift = tonumber(arg[2])
else
    error("Unsupported option.")
    return
end

-- open chords.txt
local chordFile = io.open(chordFilePath, "r")
if chordFile == nil then
    stderr.write("Unable to open: " .. chordFilePath)
end

-- process for each lines
for line in chordFile:lines() do
    -- split codes into an array
    local chordsIn = split(line, " ")
    for i, chordSrc in pairs(chordsIn) do
        local chord
        if i == 1 then
            chord = chordSrc
        else
            chord = transposeChordStr(chordSrc, keyShift)
            io.write(" ")
        end
        io.write(chord)
    end
    io.write("\n")
end

chordFile:close()