local FlMMLTimeBase = 384
local VolMacroSymbols = "ABCDEFGHIJKLMNOPQRSTUVWabcdefghijklmnopqrstuvw"
local LenMacroSymbols = "XYZxyz"
local VolMacroStep = 1
assert(VolMacroStep == 1 or VolMacroStep == 3)

function round(d)
    return math.floor(d + 0.5)
end

function clip(minValue, d, maxValue)
    return math.max(minValue, math.min(d, maxValue))
end

function ReadWaveFile(path)
    local read1 = function(file)
        return string.byte(file:read(1))
    end
    local read2 = function(file)
        local l = read1(file)
        local h = read1(file)
        return h * 0x100 + l
    end
    local read2s = function(file)
        local value = read2(file)
        if value < 0x8000 then
            return value
        else
            return value - 0x10000
        end
    end
    local read4 = function(file)
        local l = read2(file)
        local h = read2(file)
        return h * 0x10000 + l
    end

    local wave = {}
    local info = {}

    local file = io.open(path, "rb")
    if file == nil then
        return wave, info
    end

    -- verify RIFF/WAVE header
    if file:read(4) ~= "RIFF" then
        return wave, info
    end
    file:seek("cur", 4)
    if file:read(8) ~= "WAVEfmt " then
        return wave, info
    end
    local fmtChunkSize = read4(file)

    -- parse format header
    info.format = read2(file)
    info.channels = read2(file)
    info.samplerate = read4(file)
    local bytesPerSeconds = read4(file)
    local bytesPerBlock = read2(file) -- bytes/sample * channels
    info.bitwidth = read2(file)
    file:seek("cur", fmtChunkSize - 0x10)

    -- check unsupported format
    if info.format ~= 1 or (info.bitwidth ~= 8 and info.bitwidth ~= 16) then
        return wave, info
    end

    -- data chunk
    if file:read(4) ~= "data" then
        return wave, info
    end
    local dataChunkSize = read4(file)
    assert(dataChunkSize % bytesPerBlock == 0,
        "Invalid data chunk size (" .. dataChunkSize .. "/" .. bytesPerBlock .. ")")

    -- read whole samples to array
    for sampleIndex = 1, dataChunkSize / bytesPerBlock do
        for channelIndex = 1, info.channels do
            local value
            if info.bitwidth == 8 then
                value = (read1(file) - 0x80) / 0x80
            elseif info.bitwidth == 16 then
                value = read2s(file) / 0x8000
            else
                error("Unsupported bitwidth " .. info.bitwidth)
            end

            if wave[channelIndex] == nil then
                wave[channelIndex] = {}
            end
            wave[channelIndex][sampleIndex] = value
        end
    end

    return wave, info
end

-- [ volume converter ] ---------------

assert(#VolMacroSymbols % 2 == 0)
local VolMacroPatternCount = #VolMacroSymbols / 2

function MakeVolCommandAbs(targetVolume)
    return "@v" .. targetVolume
end

function MakeVolCommandRel(curVolume, targetVolume)
    local diff = targetVolume - curVolume
    local distance = math.abs(diff)
    local volDiffInc, volDiffDec = "(", ")"
    if diff < 0 then
        volDiffInc, volDiffDec = volDiffDec, volDiffInc
    end

    local symbolIndex
    if VolMacroStep == 3 then
        symbolIndex = math.floor((distance + 1) / 3)
        if distance > (3 * VolMacroPatternCount + 1) then
            symbolIndex = math.floor(symbolIndex / 2)
        end
    else
        symbolIndex = distance - 2
        if distance > (VolMacroPatternCount + 2) then
            symbolIndex = math.floor(distance / 2) - 2
        end
    end
    if diff < 0 then
        symbolIndex = symbolIndex + VolMacroPatternCount
    end
    local macroSymbol = ""
    if symbolIndex >= 1 and symbolIndex <= #VolMacroSymbols then
        macroSymbol = VolMacroSymbols:sub(symbolIndex, symbolIndex)
    end

    if distance == 0 then
        return ""
    elseif distance == 1 then
        return volDiffInc
    elseif distance == 2 then
        return volDiffInc .. volDiffInc
    else
        if VolMacroStep == 3 then
            if distance <= (3 * VolMacroPatternCount + 1) then
                if distance % 3 == 0 then
                    assert(macroSymbol ~= "")
                    return "$" .. macroSymbol
                elseif distance % 3 == 1 then
                    assert(macroSymbol ~= "")
                    return volDiffInc .. "$" .. macroSymbol
                else -- if distance % 3 == 2 then
                    assert(macroSymbol ~= "")
                    return volDiffDec .. "$" .. macroSymbol
                end
            elseif distance % 6 == 0 and distance <= 6 * VolMacroPatternCount then
                assert(macroSymbol ~= "")
                return "$" .. macroSymbol .. "$" .. macroSymbol
            else
                return MakeVolCommandAbs(targetVolume)
            end
        else
            if distance <= (VolMacroPatternCount + 2) then
                assert(macroSymbol ~= "")
                return "$" .. macroSymbol
            elseif distance % 2 == 0 and distance >= 6 and distance <= 2 * (VolMacroPatternCount + 2) then
                assert(macroSymbol ~= "")
                return "$" .. macroSymbol .. "$" .. macroSymbol
            else
                return MakeVolCommandAbs(targetVolume)
            end
        end
    end
end

function MakeVolCommand(curVolume, targetVolume)
    local volRel = MakeVolCommandRel(curVolume, targetVolume)
    local volAbs = MakeVolCommandAbs(targetVolume)
    if #volRel <= #volAbs then
        return volRel
    else
        return volAbs
    end
end

local VolMacroDefs = ""
if VolMacroPatternCount > 0 then
    local volIncMacros, volDecMacros = "", ""
    for index = 1, VolMacroPatternCount do
        volIncMacros = volIncMacros .. "$" .. VolMacroSymbols:sub(index, index) .. "="
        volDecMacros = volDecMacros .. "$" .. VolMacroSymbols:sub(VolMacroPatternCount + index, VolMacroPatternCount + index) .. "="

        if VolMacroStep == 3 then
            for i = 1, index do
                volIncMacros = volIncMacros .. "((("
                volDecMacros = volDecMacros .. ")))"
            end
        else
            volIncMacros = volIncMacros .. "(("
            volDecMacros = volDecMacros .. "))"
            for i = 1, index do
                volIncMacros = volIncMacros .. "("
                volDecMacros = volDecMacros .. ")"
            end
        end

        volIncMacros = volIncMacros .. ";"
        volDecMacros = volDecMacros .. ";"
    end
    VolMacroDefs = volIncMacros .. volDecMacros
end

-- [ length converter ] ---------------

local SamplesPerNote = 96
assert(FlMMLTimeBase % SamplesPerNote == 0)

local LengthToNoteTable = {}
-- reset
LengthToNoteTable[1] = "c"
for sampLen = 2, SamplesPerNote * 2 do
    LengthToNoteTable[sampLen] = ""
end
-- single note + dots
for sampLen = 2, SamplesPerNote do
    if SamplesPerNote % sampLen == 0 then
        local baseLen = SamplesPerNote / sampLen
        LengthToNoteTable[sampLen] = "c" .. baseLen

        local len = sampLen
        local dots = ""
        local dotLen = sampLen
        while dotLen % 2 == 0 do
            dotLen = dotLen / 2
            dots = dots .. "."

            len = len + dotLen
            if len <= #LengthToNoteTable then
                assert(LengthToNoteTable[len] == "")
                LengthToNoteTable[len] = "c" .. baseLen .. dots
            end
        end
    end
end
-- tick
for sampLen = 2, #LengthToNoteTable do
    local tick = sampLen * (FlMMLTimeBase / SamplesPerNote)
    local tickstring = "c" .. "%" .. tostring(tick)
    if LengthToNoteTable[sampLen] == "" or #LengthToNoteTable[sampLen] > #tickstring then
        LengthToNoteTable[sampLen] = tickstring
    end
end
-- continuous notes
for sampLen = 2, #LengthToNoteTable do
    if LengthToNoteTable[sampLen] == "" or #LengthToNoteTable[sampLen] > sampLen then
        local note = ""
        for index = 1, sampLen do
            note = note .. "c"
        end
        LengthToNoteTable[sampLen] = note
    end
end
-- long note
for sampLen = SamplesPerNote + 1, SamplesPerNote * 2 do
    local note = "c" .. LengthToNoteTable[sampLen - SamplesPerNote]
    if #note <= #LengthToNoteTable[sampLen] then
        LengthToNoteTable[sampLen] = note
    end
end
-- combination
for sampLen = 3, #LengthToNoteTable do
    if #LengthToNoteTable[sampLen] > 2 then
        for i = 1, math.floor(sampLen / 2) do
            j = sampLen - i
            local note = LengthToNoteTable[j] .. LengthToNoteTable[i]
            if #note < #LengthToNoteTable[sampLen] then
                LengthToNoteTable[sampLen] = note
            end
        end
    end
end
-- macros
local LenMacroDefs = ""
if #LenMacroSymbols > 0 then
    for index = 1, #LenMacroSymbols do
        local sampLen = index + 2
        local macroSymbol =LenMacroSymbols:sub(index, index)
        LenMacroDefs = LenMacroDefs .. "$" .. macroSymbol .. "=" .. LengthToNoteTable[sampLen] .. ";"
        LengthToNoteTable[sampLen] = "$" .. macroSymbol
    end
end
-- combination
for sampLen = 3, #LengthToNoteTable do
    if #LengthToNoteTable[sampLen] > 2 then
        for i = 1, math.floor(sampLen / 2) do
            j = sampLen - i
            local note = LengthToNoteTable[j] .. LengthToNoteTable[i]
            if #note < #LengthToNoteTable[sampLen] then
                LengthToNoteTable[sampLen] = note
            end
        end
    end
end

function MakeLenCommand(sampLen)
    local tick = sampLen * (FlMMLTimeBase / SamplesPerNote)
    local noteAbs = "c" .. "%" .. tostring(tick)

    local len = sampLen
    local noteRel = ""
    while len > SamplesPerNote * 2 do
        len = len - (SamplesPerNote * 2)
        noteRel = noteRel .. "c1c1"
    end
    noteRel = noteRel .. LengthToNoteTable[len]

    if #noteRel <= #noteAbs then
        return noteRel
    else
        return noteAbs
    end
end

-- [ core subroutines ] ---------------

local ShowHistogram = false

function SevenBitiseReal(d)
    return clip(0, (d + 1.0) * 0x40, 0x80)
end

function SevenBitise(d)
    return clip(0, math.floor((d + 1.0) * 0x40), 0x7f)
end

function ShowUsage()
    local options = {
        { name = "-L, -R", description = "specify target channel (left/right)" }
    }

    print("FlPCM [options] filename.wav (filename.mml)")
    print("Options:")
    for index = 1, #options do
        print(string.format("%s\t%s", options[index].name, options[index].description))
    end
    return
end

function PreprocessPCM(PCM)
    local PCM7 = {}
    local curVolume = SevenBitiseReal(PCM[1])
    for index = 1, #PCM do
        local nextVolume = SevenBitiseReal(PCM[index])
        local diff = nextVolume - curVolume
        local distance = math.abs(diff)
        PCM7[index] = clip(0, round(curVolume + diff), 0x7f)
        curVolume = nextVolume
    end
    return PCM7
end

function MakeHistogram(PCM7)
    local VolHistogram = {}
    local LenHistogram = {}
    for index = 1, 127 do
        VolHistogram[index] = 0
    end
    for index = 1, SamplesPerNote * 2 + 1 do
        LenHistogram[index] = 0
    end

    if #PCM7 <= 1 then
        return VolHistogram, LenHistogram
    end

    local curVolume = PCM7[1]
    local sampLen = 0
    for index = 1, #PCM7 do
        local nextVolume = PCM7[index]
        local diff = nextVolume - curVolume
        local distance = math.abs(diff)
        if distance ~= 0 then
            if sampLen > SamplesPerNote then
                LenHistogram[SamplesPerNote * 2 + 1] = LenHistogram[SamplesPerNote * 2 + 1] + 1
            else
                LenHistogram[sampLen] = LenHistogram[sampLen] + 1
            end
            VolHistogram[distance] = VolHistogram[distance] + 1
            sampLen = 0
        end
        sampLen = sampLen + 1
        curVolume = nextVolume
    end
    if sampLen > SamplesPerNote then
        LenHistogram[SamplesPerNote * 2 + 1] = LenHistogram[SamplesPerNote * 2 + 1] + 1
    else
        LenHistogram[sampLen] = LenHistogram[sampLen] + 1
    end
    return VolHistogram, LenHistogram
end

function ToFlPCM(MMLFile, PCM, PCMInfo)
    local PCM7 = PreprocessPCM(PCM)

    MMLFile:write(VolMacroDefs)
    MMLFile:write(LenMacroDefs)

    local sampLen = 0
    local curVolume = PCM7[1]
    MMLFile:write("$wv=@e1,0,0,128,0@5@w8q16l96")
    MMLFile:write(MakeVolCommandAbs(curVolume))
    for sampleIndex = 1, #PCM7 do
        local nextVolume = PCM7[sampleIndex]
        if curVolume ~= nextVolume then
            MMLFile:write(MakeLenCommand(sampLen))
            sampLen = 0
        end
        sampLen = sampLen + 1
        MMLFile:write(MakeVolCommand(curVolume, nextVolume))
        curVolume = nextVolume
    end
    if sampLen > 0 then
        MMLFile:write(MakeLenCommand(sampLen))
    end
    MMLFile:write(";\n")

    MMLFile:write("t" .. round(PCMInfo.samplerate * 60 / (SamplesPerNote / 4)) .. "\n")
    MMLFile:write("    $wv;\n")
    MMLFile:write("r384$wv;\n")
    MMLFile:write("r192$wv;\n")
    MMLFile:write("r128$wv;\n")

    if ShowHistogram then
        local VolHistogram, LenHistogram = MakeHistogram(PCM7)
        print("#", "vol", "len")
        for index = 1, math.max(127, SamplesPerNote * 2 + 1) do
            print(index,
                ((index <= 127) and VolHistogram[index] or ""),
                ((index <= SamplesPerNote * 2 + 1) and LenHistogram[index] or ""),
                ((index <= SamplesPerNote * 2) and MakeLenCommand(index) or ""))
        end
    end
end

-- [ application main ] ---------------

local WhichChannel = 1

-- parse commandline parameters
local argi = 1
if #arg == 0 then
    ShowUsage()
    return
end
while argi <= #arg and arg[argi]:sub(1, 1) == "-" do
    if arg[argi]:sub(2, 2) == "-" then
        local thisArg = arg[argi]:sub(3)
        argi = argi + 1

        if thisArg == "histogram" then
            ShowHistogram = true
        else
            print("Error: unknown option [--" .. thisArg .. "]")
            return
        end
    else
        local argCharIndex = 2
        local thisArg = arg[argi]:sub(2)
        argi = argi + 1

        for argCharIndex = 1, #thisArg do
            local thisArgChar = thisArg:sub(argCharIndex, argCharIndex)
            if thisArgChar == "L" then
                WhichChannel = 1
            elseif thisArgChar == "R" then
                WhichChannel = 2
            else
                print("Error: unknown option [-" .. thisArgChar .. "]")
                return
            end
        end
    end
end
if argi > #arg then
    print("Error: no input files")
    return
elseif argi + 1 < #arg then
    print("Error: too many parameters")
    return
end
local WavFilePath = arg[argi]
local MMLFile = io.stdout
if argi + 1 == #arg then
    MMLFile = io.open(arg[argi + 1], "w")
end

local PCM, PCMInfo = ReadWaveFile(WavFilePath)
if WhichChannel < 1 or WhichChannel > #PCM then
    WhichChannel = 1
end
if #PCM == 0 or #PCM[WhichChannel] == 0 then
    print("Error: Unsupported format")
    return
end

io.stderr:write(string.format("FlPCM: %d Hz, %d bit, %d channels, %d samples\n",
    PCMInfo.samplerate, PCMInfo.bitwidth, PCMInfo.channels, #PCM[WhichChannel]))

ToFlPCM(MMLFile, PCM[WhichChannel], PCMInfo)
MMLFile:close()