SpriteReader = {}

sprite_size = 32
sprite_data_size = sprite_size * sprite_size * 4


--[[
    * Inicia classe com atributo do tipo userdata 'data'
    * Seta atributos default e le data no modo "*a"
--]]
function SpriteReader:load(data)
    attr = {version = 0, numberOfSprites = 0, posByte = 1,file = data, data = data:read("*a"), id = 1}
    return setmetatable(attr, {__index = self})
end

--[[
    * Pega os valores minimo e maximos para numero de bytes fornecidos
    * signed é uma variavel boolean, quando true rearranja os limites para tipo signed
--]]
function SpriteReader:getRanges(byte, signed)
    local min, max = 0, 0
    for var = byte, 1, -1 do
        max = max +(2 ^ (8 * var))
    end
    if(signed)then
        min, max = -max/2, max/2
    end
    return min, not signed and (max - 1) or max
end

--[[
    * le byte a byte somando seus valores 'byte' numero de vezes
    * se signed é true, reajusta o valor para signed
--]]
function SpriteReader:readBytes(byte, signed)
    local min, _ = self:getRanges(byte, signed)
    local value = self:nextByte()
    for var = 2, byte do
        value = value + (self:nextByte() ^ 2)
    end
    return (value + min)
end

--[[
    * le 'posByte', que é um atributo de controle, serve apaenas para armazenar o proximo byte
    * reajusta 'posByte' para posição seguinte
    * retorna 'byte'
--]]
function SpriteReader:nextByte()
    local byte = self.data:byte(self.posByte)
    self.posByte = self.posByte + 1
    return tonumber(byte)
end

--[[
    * faz a leitura byte a byte 8 vezes somando seus valores pela progressão:
    * (byte) ^ 1 + (byte) ^ 2 + ... + (byte) ^ n
    * valido para todos unsigneds abaixo
--]]
function SpriteReader:getUint64()
    return self:readBytes(8, false)
end

function SpriteReader:getUint32()
    return self:readBytes(4, false)
end

function SpriteReader:getUint16()
    return self:readBytes(2, false)
end

function SpriteReader:getUint8()
    return self:readBytes(1, false)
end

--[[
    * segue a mesma lógica anterior, com uma unica diferença
    * o valor final é reajustado para signed
--]]
function SpriteReader:getInt64()
    return self:readBytes(8, true)
end

function SpriteReader:getInt32()
    return self:readBytes(4, true)
end

function SpriteReader:getInt16()
    return self:readBytes(2, true)
end

function SpriteReader:getInt8()
    return self:readBytes(1, true)
end

--[[
    * fecha o atributo file
--]]
function SpriteReader:closeData()
    return self.file:close()
end


function SpriteReader:getImage(id)

    local offset = (((id-1) * 4) + 6)
    self.posByte = offset
    local spriteAddress = self:getUint32()
    self.posByte = spriteAddress
    -- skip
    self:getInt8()
    self:getInt8()
    self:getInt8()

    local pixelDataSize = self:getUint16()
    local image = SpriteWriter:new(id)
    image:addMagicNumber()
    image.file:write(0x00)
    image.file:write(0x00)
    image.file:write(0x00)
    image.file:write(0x00)
    image.file:write(spriteAddress)

    local read_ = 0
    local writePos = 0
    while(read_ < pixelDataSize) do

        local transparentPixels = self:getUint16()
        local coloredPixels = self:getUint16()

        for i = 0, transparentPixels do
            image.file:write(0x00)
            image.file:write(0x00)
            image.file:write(0x00)
            image.file:write(0x00)
            writePos = writePos + 4
        end

        for i = 0, coloredPixels do
            image.file:write(self:getUint8())
            image.file:write(self:getUint8())
            image.file:write(self:getUint8())
            image.file:write(0xFF)
            writePos = writePos + 4
        end
        read_ = read_ + 4 + (3 * coloredPixels)
    end
    while writePos < pixelDataSize do
        image.file:write(0x00)
        image.file:write(0x00)
        image.file:write(0x00)
        image.file:write(0x00)
        writePos = writePos + 4
    end
    return image.file
end

SpriteWriter = {}

function SpriteWriter:new(fileName)
    local file = io.open(fileName..".bmp", "wp")
    return setmetatable({file = file}, {__index = self})
end

function SpriteWriter:addMagicNumber()
    self.file:write(0x42)
    self.file:write(0x4D)
end


    local file = io.open("./ka.spr", "rb")
    reader = SpriteReader:load(file)
    reader.version = reader:getUint32()
    reader.numberOfSprites = reader:getUint16()
    io.write("Version: ",reader.version,"\nNumber Of Sprites: ", reader.numberOfSprites)
    for id = 1, reader.numberOfSprites do
        local img = reader:getImage(id)
        img:close()
    end

    reader:closeData()