d3.csv('titanic_dataset.csv', function(data) {
    alluvial.draw(
        d3.select('svg'),
        dataToGraph(data)
    );
})

var dataToGraph = function(data) {
    var d = { nodes: [], links: [] }

    var steps = _.keys(_.first(data));

    if ( steps < 2) return d;

    var n = [], l = [], si, ti;

    for (var i=0; i < steps.length-1; i++ ) {

    var sg = steps[i]
    var tg = steps[i+1]
    var relations = d3.nest()
        .key(function (d) { return d[sg] } )
        .key(function (d) { return d[tg] } )
        .entries(data)

    relations.forEach(function (s){
        si = getNodeIndex(n, s.key, sg);

        if ( si == -1) {
        n.push({ name : s.key, group : sg })
        si = n.length-1;
        }

        s.values.forEach(function (t){
        ti = getNodeIndex(n, t.key, tg)
        if (ti == -1) {
            n.push({ name : t.key, group : tg })
            ti = n.length-1;
        }
        var value = t.values.length;
        var link = { source : n[si], target : n[ti], value : value };
        l.push(link);
        })

    })
    }
    d.nodes = n.sort(customSort);
    l.forEach(function (d){ d.source = n.indexOf(d.source); d.target = n.indexOf(d.target)});
    d.links = l;
    return d;
}

function customSort(a, b) {
    var Item1 = a.group;
    var Item2 = b.group;
    if(Item1 != Item2)
        return (Item1.localeCompare(Item2));
    else 
        return (a.name.localeCompare(b.name));
}


function getNodeIndex(array, name, group) {
    for (var i in array) {
        var a = array[i]
        if (a['name'] == name && a['group'] == group) {
            return i;
        }
    }
    return -1;
}