hackmud sample script: ledger (using #db)

// call the script as script_name{type:"<action type>", user:"<target_user>", amount:<number, or GC string>}
// some actions do not require amount, and some do not require user
// current character count, as measured by hackmud: 1312 characters
function(context, args)
{
    var l = #s.scripts.lib();
    // we set a ledger_type:"demo" value in each document, so that we can later filter/update/delete *just* entries from this ledger
    var ledger_name = 'demo';

    // preprocess the amount
    if (args.amount) {
        args.amount = amountAsNumber(args.amount);
    }

    function hasAccount(user_name) {
        return #db.f({user:user_name}).count > 1;
    }

    function getBalance(user_name) {
        return l.to_gc_str(#db.f({ledger_type: ledger_name, user:user_name}).first.balance);
    }

    // $inc is used for both increment and decrement, so pass in negative amount for decrement
    function addBalance(user_name, amount) {
        #db.u({ledger_type: ledger_name, user:user_name}, {"$inc": { balance: amount }});
    }

    function amountAsNumber(amount) {
        return (typeof amount == 'number') ? amount : l.to_gc_num(amount);
    }

    switch(args.type) {
        case 'open':
            if (!hasAccount(args.user)) {
                #db.i({ledger_type: ledger_name, user:args.user, balance:0});
                return { ok: true };
            } else {
                return { ok: false, msg: "That user already has an account" };
            }
            break;
        case 'check':
            return getBalance(args.user);
        case 'sub':
            args.amount = -args.amount;
            //deliberate fall-through to the 'add' case
        case 'add':
            addBalance(args.user, amountAsNumber(args.amount));
            return { ok: true, msg: "New balance for user " + args.user + ": " + getBalance(args.user) };
        case 'close':
            if (hasAccount(args.user)) {
                #db.r({ledger_type: ledger_name, user:args.user});
                return { ok: true };
            } else {
                return { ok: false, msg: "That user does not have an account" };
            }
            break;
        case 'list':
            // use .map() to remove the not-very-useful _id field from all these documents
            return #db.f({ledger_type: ledger_name}).array.map(function(doc) { delete doc._id; return doc; });
        case 'bankrupt':
            // well, we're done. Close everything, burn all the books!
            #db.r({ledger_type: ledger_name});
            return "Ledger deleted.";
        default:
            return { ok: false, msg:"unrecognized transaction type" };
    }
}