--[[
    If we had Regex, we could convert all numbers to letters
    and match (\S)\1+ to find repetitions but that doesn't work
    in Lua patterns.
]]
local function findRepetitions(row)
    local lastNum = row[1]
    local repetitions = {}
    local curTable = {}

    for i=1,#row+1 do
        local c = row[i]

        if c == lastNum then
            curTable[#curTable + 1] = c
        elseif c == nil then
            repetitions[#repetitions + 1] = curTable
        else
            repetitions[#repetitions + 1] = curTable
            curTable = { c }
        end

        lastNum = c
    end

    return repetitions
end

local function simplifyColour(colour)
    return math.log(colour) / math.log(2)
end

function save(filename, map, solidity)
    local file = fs.open(filename, "wb")

    -- Header
    -- Magic word, "MAP".
    file.write(string.byte("M"))
    file.write(string.byte("A"))
    file.write(string.byte("P"))

    file.write(#map) -- Map height.
    file.write(solidity ~= nil and #solidity or 0) -- Write the size of the solidity bank. 0 if none.

    -- Map bank.
    -- Write the map.
    for y=1,#map do
        for _,v in ipairs(findRepetitions(map[y])) do
            if #v <= 2 then
                for i=1,#v do
                    file.write(simplifyColour(v[1]))
                end
            elseif #v >= 3 then
                file.write(0xFF)
                file.write(simplifyColour(v[1]))
                file.write(#v)
            end
        end

        file.write(string.byte('\n'))
    end

    -- Solidity bank.
    if solidity ~= nil then
        for i,v in ipairs(solidity) do
            file.write(v[1])
            file.write(v[2])
        end
    end

    file.close()
end

function load(filename)
    local file = fs.open(filename, "rb")

    -- Header
    -- There has to be a better way to do this... Feel free to change it.
    local c1 = string.char(file.read())
    local c2 = string.char(file.read())
    local c3 = string.char(file.read())
    local word = c1 .. c2 .. c3

    assert(word == "MAP", "not a valid map file!")

    local height = file.read()

    local solidBankSize = file.read()

    local tbl = {}
    local curTbl = {}

    local i = 0
    while i < height do
        local id = file.read()

        if id == 0xFF then
            local num = file.read()
            local repet = file.read()

            for j=1,repet do
                curTbl[#curTbl + 1] = { ["c"] = 2 ^ num, ["s"] = false }
            end
        elseif id == string.byte('\n') then
            tbl[#tbl + 1] = curTbl
            curTbl = {}
            i = i + 1
        else
            curTbl[#curTbl + 1] = { ["c"] = 2 ^ id, ["s"] = false }
        end
    end

    for i=1,solidBankSize do
        local x = file.read()
        local y = file.read()
        tbl[y][x]["s"] = true
    end

    file.close()
    return tbl
end