Javascript Parse Nested String Functions with parameters

I am trying to parse this string into a organized set of functions:

var str = "a(b, c(e, f(h,i,j), g(k,l,m(o,p,q)) ), d(r,s,t))"

Ideally I would like to turn it into a JSON like this:

var obj = {
    func:'a',
    params:[
        {p:'b'},
        {p: {
            func:'c',
            params:[
                {
                    p:'e',
                    p:{
                        func:'f',
                        params:[
                            {p:'h'},
                            {p:'i'},
                            {p:'j'}
                        ]
                    },
                    p:'g',
                    params:[
                        {p:'k'},
                        {p:'l'},
                        {p:{
                            func:'m',
                            params:[
                                {p:'o'},
                                {p:'p'},
                                {p:'q'}
                            ]
                        }}
                    ]
                }
            ]
        }},
        {
            p:'d',
            params:[
                {p:'r'},
                {p:'s'},
                {p:'t'}
            ]
        }
    ]
}

I have tried about 8 hours of mixed str.replace() str.substring(), and str.indexOf() and not had any luck.

Any help about how to go about achieving my goal would be appreocated.

note: the functions could take any number params and is not set to 3