Javascript Regex: get specific parts inside brackets without taking extra brackets

Question

I am building a program that would simplify coding discord bots. I wanted to add inline functions, but seems like my regex selector is not the perfect match.

My program loops through every inline function and tests if it exists in the string. And replaces the inline function strings with the inline function returnings.

For example, {ping} is translated to 91. Or, {id author} is translated to id of the message author.

The problem is that if there are inline functions in an inline function. I managed to solve 1 inline function per 1, but as the number grow, my regex selector fails and just matches the wrong stuff.

what i want it to match:

{avatarurl {id {message}}}
           ^^^^^^^^^^^^^^

can even match this too:

{avatarurl {id {message}}}
               ^^^^^^^^^

this too:

{avatarurl {id {message}}}
^^^^^^^^^^^^^^^^^^^^^^^^^^

and so on.

it just needs to starts from {(function name) and end with }.

my regex selector fails at matching this part, it just matches extra brackets. I need a perfect regex selector that will match {blabla}, but still work when placed into another {blabla}.

this is the pattern that didnt work out: new RegExp(`\{${func.name}([^\}]+[^])*\}`)

the func.name is the function name. i also need the part that comes after "{funcname" and before "}".

Answer 1

This is a general non-regex solution to brackets (supports unbalanced input).

You can then just traverse the tree and search for your matches.

Edit: converted into a class

class BracketTree {

    constructor (brackets, string) {

        if (typeof brackets != 'string' || brackets.length != 2 || brackets[0] == brackets[1]) {
            return null;
        }

        let opening = brackets[0];
        let closing = brackets[1];

        function parse (start) {

            let children = [];
            let pos = start;

            loop: while (pos < string.length) {

                switch (string[pos]) {

                case opening:
                    let child = parse(pos + 1);
                    children.push(child);
                    if (child.end == string.length) {
                        break loop;
                    }
                    pos = child.end;
                    break;

                case closing:
                    if (start == 0) {
                        children = [{
                            children, start, end: pos, opened: false, closed: true,
                            contents: string.slice(0, pos)
                        }];
                    }
                    else {
                        return {
                            children, start, end: pos, opened: true, closed: true,
                            contents: string.slice(start, pos)
                        };
                    }
                }

                pos++;
            }

            return (start == 0)? {
                children, start, end: string.length, opened: false, closed: false,
                contents: string
            }: {
                children, start, end: string.length, opened: true, closed: false,
                contents: string.slice(start)
            };
        }

        this.root = parse(0);
    }

    traverse (callback) {

        if (typeof callback != 'function') {
            return false;
        }

        let root = this.root;
        let input = root.contents;
        let nodeId = 0;

        function recurse (parent, level) {

            function callbackLeaf (start, end) {
                callback({
                    root, parent, level,
                    nodeId: nodeId++, childId: childId++,
                    start, end, contents: input.slice(start, end)
                });
            }

            function callbackBranch (branch) {
                return callback({
                    root, parent, branch, level,
                    nodeId: nodeId++, childId: childId++
                });
            }

            let children = parent.children;
            let childId = 0;
            if (children.length == 0) {
                callbackLeaf(parent.start, parent.end);
                return;
            }

            callbackLeaf(parent.start, children[0].start - children[0].opened);
            if (callbackBranch(children[0])) {
                recurse(children[0], level+1);
            }

            for (var i = 0; i < children.length-1; i++) {
                callbackLeaf(children[i].end + children[i].closed, children[i+1].start - children[i+1].opened);
                if (callbackBranch(children[i+1])) {
                    recurse(children[i+1], level+1);
                }
            }

            callbackLeaf(children[i].end + children[i].closed, parent.end);
        }

        recurse(root, 0);
        return true;
    }
}

let input = 'NOT OPENED {3}2}1}***{avatarurl {id {message}}} blah blah blah {1{2{3} NOT CLOSED';
let tree = new BracketTree('{}', input);

function filteredTraverse (caption, leafFilter, branchFilter) {
    console.log(`${'-'.repeat(29 - caption.length/2)} ${caption} `.padEnd(60, '-'));
    leafFilter ??= () => true;
    branchFilter ??= () => true;
    tree.traverse((args) => {
        if (args.branch) {
            return branchFilter(args);
        }
        if (leafFilter(args)) {
            console.log(`${'  '.repeat(args.level)}<${args.contents}>`);
        }
    });
}

filteredTraverse(
    'Ignore unbalanced and all their descendants',
    null,
    ({branch}) => branch.opened && branch.closed
);

filteredTraverse(
    'Ignore unbalanced but include their descendants',
    ({parent}) => parent.opened == parent.closed
);

filteredTraverse(
    'Ignore empty',
    ({start, end}) => start != end
);

filteredTraverse(
    'Show non-empty first children only',
    ({childId, start, end}) => childId == 0 && start != end
);