import { isAmpBoilerplate } from '../helpers.mjs';

/* Merge multiple <style> into one */
export default function mergeStyles(tree) {
    const styleNodes = {};

    tree.match({tag: 'style'}, node => {
        const nodeAttrs = node.attrs || {};
        // Skip <style scoped></style>
        // https://developer.mozilla.org/en/docs/Web/HTML/Element/style
        //
        // Also skip SRI, reasons are documented in "minifyJs" module
        if ('scoped' in nodeAttrs || 'integrity' in nodeAttrs) {
            return node;
        }

        if (isAmpBoilerplate(node)) {
            return node;
        }

        const styleType = nodeAttrs.type || 'text/css';
        const styleMedia = nodeAttrs.media || 'all';
        const styleKey = styleType + '_' + styleMedia;
        if (styleNodes[styleKey]) {
            const styleContent = (node.content || []).join(' ');
            styleNodes[styleKey].content.push(' ' + styleContent);
            return '';
        }

        node.content = node.content || [];
        styleNodes[styleKey] = node;
        return node;
    });

    return tree;
}