technic = technic or {}
technic.nodes = {}

technic.nodes_file = {
    load = function()
        local nodesfile = io.open(minetest.get_worldpath()..'/technic_nodes.txt', "r")
        if nodesfile then
            local contents = nodesfile:read('*all')
            io.close(nodesfile)
            if contents ~= nil then
                local lines = string.split(contents, "\n")
                for _,entry in ipairs(lines) do
                    local name, px, py, pz, meta = unpack(string.split(entry, "°"))
                    technic.set_node({x=px, y=py, z=pz}, name, meta)
                end
            end
        end
    end,
    save = function() --WRITE CHANGES TO FILE
        local output = ''
        for x,ys in pairs(technic.nodes) do
            for y,zs in pairs(ys) do
                for z,names in pairs(zs) do
                    for name,meta in pairs(names) do
                        output = name.."°"..x.."°"..y.."°"..z.."°"..dump(meta).."\n"
                    end
                end
            end
        end
        local f = io.open(minetest.get_worldpath()..'/technic_nodes.txt', "w")
        f:write(output)
        io.close(f)
    end
}

local function table_empty(tab) --looks if it's an empty table
    if dump(tab) == "{}" then --tab == {} didn't work
        return true
    end
    return false
end

function technic.nodes_info() --returns an info string of the node table
    local tmp = "[technic] "..dump(technic.nodes).."\n[technic]:\n"
    for x,a in pairs(technic.nodes) do
        for y,b in pairs(a) do
            for z,c in pairs(b) do
                for name,meta in pairs(c) do
                    tmp = tmp..">\t"..name.." "..x.." "..y.." "..z.." "..dump(meta).."\n"
                end
            end
        end
    end
    return tmp
end

function technic.clean_node_table() --replaces {} with nil
    local again = true
    while again do
        again = false
        for x,ys in pairs(technic.nodes) do
            if table_empty(ys) then
                technic.nodes[x] = nil
                again = true
            else
                for y,zs in pairs(ys) do
                    if table_empty(zs) then
                        technic.nodes[x][y] = nil
                        again = true
                    else
                        for z,names in pairs(zs) do
                            if table_empty(names) then
                                technic.nodes[x][y][z] = nil
                                again = true
                            else
                                for name,meta in pairs(names) do
                                    if table_empty(meta)
                                    or meta == "" then
                                        technic.nodes[x][y][z][name] = nil
                                        again = true
                                    end
                                end
                            end
                        end
                    end
                end
            end
        end
    end
end

function technic.complete_node_table(pos, name) --neccesary because tab[1] wouldn't work if tab is not a table
    local tmp = technic.nodes[pos.x]
    if not tmp then
        technic.nodes[pos.x] = {}
    end
    local tmp = technic.nodes[pos.x][pos.y]
    if not tmp then
        technic.nodes[pos.x][pos.y] = {}
    end
    local tmp = technic.nodes[pos.x][pos.y][pos.z]
    if not tmp then
        technic.nodes[pos.x][pos.y][pos.z] = {}
    end
    local tmp = technic.nodes[pos.x][pos.y][pos.z][name]
    if not tmp then
        technic.nodes[pos.x][pos.y][pos.z][name] = {}
    end
end

function technic.get_node(pos, name)
    if not pos then
        return false
    end
    local tmp = technic.nodes[pos.x]
    if not tmp
    or table_empty(tmp) then
        return false
    end
    local tmp = technic.nodes[pos.x][pos.y]
    if not tmp
    or table_empty(tmp) then
        return false
    end
    local tmp = technic.nodes[pos.x][pos.y][pos.z]
    if not tmp
    or table_empty(tmp) then
        return false
    end

    -- if name isn't mentioned, just look if there's a node
    if not name then
        return true
    end

    local tmp = technic.nodes[pos.x][pos.y][pos.z][name]
    if not tmp
    or table_empty(tmp) then
        return false
    end
    return tmp
end

function technic.remove_node(pos)
    if not pos then
        return false
    end
    if technic.get_node(pos) then
        technic.nodes[pos.x][pos.y][pos.z] = nil
        local xarr = technic.nodes[pos.x]
        if table_empty(xarr[pos.y]) then
            technic.nodes[pos.x][pos.y] = nil
        end
        if table_empty(xarr) then
            technic.nodes[pos.x] = nil
        end
    else
        print("[technic] Warning: The node at ("..pos.x.."|"..pos.y.."|"..pos.z..") wasn't stored in technic.nodes.")
    end
end

function technic.set_node(pos, name, meta)
    if not (name or pos) then
        return false
    end
    technic.complete_node_table(pos, name)
    meta = meta or true
    technic.nodes[pos.x][pos.y][pos.z][name] = meta
end

minetest.register_node("ac:block9", {
    description = "vartestblock",
    tiles = {"ac_block.png"},
    groups = {snappy=1,bendy=2,cracky=1},
    sounds = default_stone_sounds,
    on_construct = function(pos)
        technic.set_node(pos, "LV", 3)
        --print(technic.nodes_info())
    end,
    after_dig_node = function(pos)
        technic.remove_node(pos)
        --print(technic.nodes_info())
    end
})

minetest.register_chatcommand('cleantechnictable',{
    description = 'Tidy up technic.nodes.',
    params = "",
    privs = {},
    func = function(name)
        technic.clean_node_table()
        local tmp = technic.nodes_info()
        minetest.chat_send_player(name, tmp)
        print("[technic] "..tmp)
    end
})

technic.nodes_file["load"]()