mid

local FileName = "tet.mid"
local File = fs.open(FileName, "rb")
local ToHex = "%X"

--(( Functions ))--

-- returns a HEX string
local function BigEndian(Size, Stri, Conc)
    local Tbl = {}
    for Count = 1, Size do
        table.insert(Tbl, File.read())
    end
    if Stri == true then
        local Str = ""
        for i,v in pairs(Tbl) do
            Str = Str .. string.char(v)
        end
        return Str
    elseif Conc == true then
        return table.concat(Tbl, "")
    else
        return Tbl
    end
end

-- returns a HEX string
local function LittleEndian(Size)
    local T = {}
    for Count = 1,Size do
        table.insert(T,ToHex:format(File.read()))
    end
    local Str = ""
    for Count = #T,1,-1 do
        Str = Str .. T[Count]
    end
    return Str
end

local function ToBit(Byte)
    local Tbl = {}
    local Num = {
        128;
        64;
        32;
        16;
        8;
        4;
        2;
        1;
    }
    local On = Byte
    for i = 1, 8 do
        local Wh = math.floor(On/Num[i])
        Tbl[i] = Wh
        if Wh == 1 then
            On = On - Num[i]
        end
    end

    return Tbl
end

local function parseVarInt(s, bits) -- parses multiple bytes as an integer
  if not s then
    error("error parsing file")
  end
  bits = bits or 8
  local mask = bit.brshift(0xFF, 8 - bits)
  local num = 0
  for i = 1, s:len() do
    num = num + bit.blshift(bit.band(s:byte(i), mask), (s:len() - i) * bits)
  end
  return num
end

local function GetVL()
    local Done = ""
    while true do
        local By = File:read()
        Done = Done .. string.char(By)
        local Bits = ToBit(By)
        if Bits[1] == 0 then
            return parseVarInt(Done, 7)
        end
    end
end

-- Header Chunk
local ChunkID = BigEndian(4, true)
local ChunkSize = tonumber(BigEndian(4, false, true))
local FormatType = tonumber(BigEndian(2, false, true))
local NTracks = tonumber(BigEndian(2, false, true))
local TDiv = BigEndian(2, false)

-- Track Chunk
local TChunkID = BigEndian(4, true)
local TChunkSize = tonumber(BigEndian(4, false, true))

print("Header Chunk")
print("Chunk ID: " .. ChunkID)
print("Chunk Size: " .. ChunkSize)
print("Format Type: " .. FormatType)
print("Number of Tracks: " .. NTracks)
-- print("Time Division: " .. TDiv)

print("Track Chunk")
print("Chunk ID: " .. TChunkID)
print("Chunk Size: " .. TChunkSize)

local function GetPar(By)
    return bit.band(0xF, By), File:read(), File:read()
end

local Tra = {}

--for Ded = 1, math.huge do
    local Delt = GetVL()
    print("Delta time: " .. Delt)
    File:read()
    local By = File:read()
    local EType = bit.band(0xF0, By)
    print("Event Type: 0x" .. ToHex:format(EType))
    if EType == 0x80 then -- Note Off
        print(":3")
        local Channel, Note, Velocity = GetPar()
        table.insert(Tra, {"note_off", Note, Velocity, Channel})
    elseif EType == 0x9 then -- Note On
        local Channel, Note, Velocity = GetPar()
        table.insert(Tra, {"note_on", Note, Velocity, Channel})
    elseif EType == 0xA then -- Aftertouch
        GetPar()
    elseif EType == 0xB then -- Controller
        GetPar()
    elseif EType == 0xC then -- Program change
        GetPar()
    elseif EType == 0xD then -- Aftertouch
        GetPar()
    elseif EType == 0xE then -- Pitch Bend
        GetPar()
    elseif EType == 0xF0 then
        local Length = GetVL()
        for i = 1, Length - 1 do
            File.read()
        end
        print(Length)
        break
    end
--end

File.close()