const nonAlphaNum = /[^A-Za-z0-9\-]/g;
const space = /\s/g

export function makeSlug(text) {
    return text
        .toLowerCase()
        .replace(space, '-')
        .replace(nonAlphaNum, '')
}

function apply(node, types, fn) {
    if (typeof types === 'string') {
        types = new Set([types]);
    }
    else if (!(types instanceof Set)) {
        types = new Set(types)
        console.log(types)
    }

    if (types.has(node.type)) {
        fn(node);
    }
    if ('children' in node) {
        for (let child of node.children) {
            apply(child, types, fn);
        }
    }
}

function getTextContent(node) {
    let segments = [];
    apply(node, 'text', textNode => {
        // skip all-whitespace strings
        if (textNode.value.match(/^\s+$/)) return;
        segments.push(textNode.value.trim());
    });

    return segments.join(' ');
}

export default function slug() {
    return (tree) => {
        apply(tree, 'element', e => {
            if (e.tagName.match(/h[1-6]/)) {
                let text = getTextContent(e);
                e.properties.id = makeSlug(text);
            }
        })
    }
}