boris/node_modules/applesauce-content/dist/nast/truncate.js

export function truncateContent(tree, maxLength = 256) {
    let length = 0;
    for (let i = 0; i < tree.children.length; i++) {
        const node = tree.children[i];
        switch (node.type) {
            case "hashtag":
                length += 1 + node.hashtag.length;
                break;
            case "mention":
                // guess user names are about 10 long
                length += 10;
                break;
            case "cashu":
                length += node.raw.length;
                break;
            case "gallery":
                length += node.links.reduce((t, l) => t + l.length, 0);
                break;
            case "link":
            case "text":
                length += node.value.length;
                break;
            case "emoji":
                length += 1;
                break;
        }
        if (length > maxLength) {
            if (node.type === "text") {
                const children = i > 0 ? tree.children.slice(0, i) : [];
                const chunkLength = node.value.length - (length - maxLength);
                // find the nearest newline
                const newLines = node.value.matchAll(/\n/g);
                for (const match of newLines) {
                    if (match.index && match.index > chunkLength) {
                        children.push({ type: "text", value: node.value.slice(0, match.index) });
                        return { ...tree, children, truncated: true };
                    }
                }
                // just cut the string
                children.push({ type: "text", value: node.value.slice(0, maxLength - length) });
                return { ...tree, children, truncated: true };
            }
            else
                return { ...tree, children: tree.children.slice(0, i), truncated: true };
        }
    }
    return tree;
}