//Title: Weighted Probability Selection
//Credit to: Jtgibson
//Contributed by: Jtgibson


proc/weightedprob(choices[], weights[])
    if(!choices || !weights) return null

    //Build a range of weights
    var/max_num = 0
    for(var/X in weights) if(isnum(X)) max_num += X

    //Now roll in the range.
    var/weighted_num = rand(1,max_num)

    var/running_total, i

    //Loop through all possible choices
    for(i = 1; i <= choices.len; i++)
        if(i > weights.len) return null

        running_total += weights[i]

        //Once the current step is less than the roll,
        // we have our winner.
        if(weighted_num <= running_total)
            return choices[i]


///*
//Testing code/sample implementation:

mob/proc/test_weighted_prob()
    var/weights = list(  5, 10, 20, 40, 20, 15, 10,  5, 2)
    var/choices = list("1","2","3","4","5","6","7","8","9")

    usr << weightedprob(choices, weights)

//*/