Double entry bookkeeping in pegjs

doubleentry.pegjs

/*

Use pegjs online evaluator to try
https://pegjs.org/online

Input sample:

albin food 100.00
juliana food 100

Output:

{
   "albin": -100,
   "food": 200,
   "juiana": -100
}

*/

{
    var accounts = {};
    
    function addTransaction(cr, dr, am) {
        if (!(cr in accounts)) accounts[cr] = 0;
        if (!(dr in accounts)) accounts[dr] = 0;
        accounts[cr] -= am;
        accounts[dr] += am;
    }
}

start = transaction*
{
    for(var account in accounts) accounts[account] /= 100;
    return accounts
}

transaction = cr:account _ dr:account _ am:amount _
{
    if (cr === dr) expected("different accounts");
    addTransaction(cr, dr, am);
}

amount =
    decimal / integer
digit =
    [0-9]
integer =
    int:digit+
    { return parseInt(int.join("")) * 100}
decimal =
    int:digit+ '.' fra:(digit digit)
    { return parseInt(int.join("")) * 100 + parseInt(fra.join(""))}
account =
    acc:[a-zA-Z]+
    { return acc.join(""); }
_ =
    !.
    / [ \t\n]+