local function getUint16(bytes, idx)
    return bytes[idx] * 256 + bytes[idx + 1]
end

local function getUint8(bytes, idx)
    return bytes[idx]
end

local function componentToHex(c)
    return string.format("%02x", c)
end

local function rgbToHex(r, g, b)
    return "#" .. componentToHex(r) .. componentToHex(g) .. componentToHex(b)
end

local function unpack_block(whole_buffer, startByte)
    local paletteIdx = getUint16(whole_buffer, startByte)
    local packedInfo = getUint8(whole_buffer, startByte + 2)
    local blockAmount = math.floor(packedInfo / 16)
    local byteRemoval = packedInfo % 16

    local textArr = {}

    for i = 1, blockAmount do
        local byte = getUint8(whole_buffer, startByte + 2 + i)
        for bit = 7, 0, -1 do
            table.insert(textArr, ((math.floor(byte / (2 ^ bit)) % 2) == 1) and "\n" or "▇")
        end
    end

    if byteRemoval > 0 then
        for i = 1, byteRemoval do
            table.remove(textArr)
        end
    end

    local endByte = startByte + 2 + blockAmount
    return { paletteIdx = paletteIdx, text = table.concat(textArr), endByte = endByte }
end


local function unpack_blocks(packed)
    local size = getUint16(packed, 1)

    local palette = {}
    local idx = 3

    for i = 1, 300 do
        table.insert(palette, {
            getUint8(packed, idx + 1),
            getUint8(packed, idx + 2),
            getUint8(packed, idx + 3)
        })
        idx = idx + 3
    end

    local blocks_unpacked = {}
    idx = idx + 1

    while idx <= #packed do
        local block = unpack_block(packed, idx)
        idx = block.endByte + 1
        block.color = rgbToHex(table.unpack(palette[block.paletteIdx + 1]))
        block.paletteIdx = nil
        block.endByte = nil
        table.insert(blocks_unpacked, block)
    end

    return blocks_unpacked
end

return { unpack_blocks = unpack_blocks }

--[[
local base64 = require("base64")
local lz4 = require("lz4")

local bytes = base64.decode(image)
local byte_table = {}
for num in string.gmatch(bytes, "%d+") do
    table.insert(byte_table, tonumber(num))
end
local decomp = lz4.decompress(byte_table)

local unpacked = unpack_blocks(decomp)
local json = <..json serializer..>:serialize(unpacked);
]]