sorting c3 stacked bar chart per category

i need to sort stacked bar chart in each category by value so for the following code:

var chart = c3.generate({
    data: {
        columns: [
            
            ['data1', 100, 400, 500, 800, 900],
            ['data2', 200, 300, 600, 700, 1000]
        ],
        type: 'bar',
        groups: [
            ['data1', 'data2']
        ]
    },
    axis: {
      x: {
          type: "category",
           categories: ['c1', 'c2', 'c3', 'c4', 'c5']
      }
    },
    grid: {
        y: {
            lines: [{value:0}]
        }
    }
});

in category c1 i want to see data1 under data2 (because 100 < 200) but in category c2 i want to see data2 under data1 (because 400 > 300). the c3 data order property is only making the sort based on the sum over all the categories.

the graph before sort looks like: unsorted graph

desired sort: sorted graph per category by value