import * as posix from "node:path/posix";
import { Node, Element } from "antihtml";

function shallowCopyElement(element: Element) {
	const copy = new Element(element.name);
	copy.attributes = new Map(element.attributes);
	copy.childNodes = element.childNodes;
	return copy;
}

/**
	Resolves absolute href attributes in a and link elements the Node tree into relative references from the given directory.

	@param node Node tree to transform
	@param dir Absolute path to directory to resolve references from.
	@returns new node tree with href attributes transformed, or the original node if no transformations took place.
*/
export function resolveRefs(node: Node, dir: string) {
	if (!(node instanceof Element)) {
		return node;
	}
	let resolvedNode = node;
	const name = node.name;
	if (
		(name === "link" || name === "a")
		&& node.attributes.has("href")
	) {
		const original = node.attributes.get("href")!
		/* node:coverage ignore next 3 */
		if (!original.startsWith("/")) {
			console.log(`Warning: found relative href to ${original}`);
		} else {
			const ref = posix.relative(dir, original);
			resolvedNode = shallowCopyElement(node);
			resolvedNode.attributes.set("href", ref);
		}
	}
	const resolvedChildren: Node[] = [];
	let modifiedChildren = false;
	for (const child of resolvedNode.childNodes) {
		const resolvedChild = resolveRefs(child, dir);
		if (child !== resolvedChild) {
			modifiedChildren = true;
		}
		resolvedChildren.push(resolvedChild);
	}
	if (modifiedChildren) {
		resolvedNode = shallowCopyElement(node);
		resolvedNode.childNodes = resolvedChildren;
	}
	return resolvedNode;
}