ComfyFactorio/functions/connect_belts.lua

local direction_tendencies = {
    [1] = {0, 2, 4, 6},
    [2] = {2, 4, 6, 0},
    [3] = {4, 6, 0, 2},
    [4] = {6, 0, 2, 4}
}

local function get_optimal_direction(entity, direction_tendency)
    local original_direction = entity.direction
    local optimal_direction = entity.direction
    local max_connection_count = #entity.belt_neighbours['inputs'] + #entity.belt_neighbours['outputs']

    for _, d in pairs(direction_tendency) do
        entity.direction = d
        local count = #entity.belt_neighbours['inputs'] + #entity.belt_neighbours['outputs']
        --if #entity.belt_neighbours["inputs"] > 0 and #entity.belt_neighbours["outputs"] > 0 then
        --	optimal_direction = d
        --	break
        --end
        if count > max_connection_count then
            max_connection_count = count
            optimal_direction = d
        end
    end

    if max_connection_count == 1 then
        for _, d in pairs(direction_tendency) do
            entity.direction = d
            if #entity.belt_neighbours['inputs'] > 0 then
                if d == entity.belt_neighbours['inputs'][1].direction then
                    optimal_direction = d
                    break
                end
            end
            if #entity.belt_neighbours['outputs'] > 0 then
                if d == entity.belt_neighbours['outputs'][1].direction then
                    optimal_direction = d
                    break
                end
            end
        end
    end

    entity.direction = original_direction

    return optimal_direction
end

local function connect_belts(entities, d)
    for _ = 1, 4, 1 do
        local r = d
        if not r then
            r = math.random(1, 4)
        end
        for k, entity in pairs(entities) do
            entity.direction = get_optimal_direction(entity, direction_tendencies[r])
        end
    end
end

return connect_belts