1 files changed, 115 insertions, 0 deletions
diff --git a/src/utils/webmentions.ts b/src/utils/webmentions.ts
new file mode 100644
index 0000000..c9f62b7
--- /dev/null
+++ b/src/utils/webmentions.ts
@@ -0,0 +1,115 @@
+import * as fs from "node:fs";
+import { WEBMENTION_API_KEY } from "astro:env/server";
+import type { WebmentionsCache, WebmentionsChildren, WebmentionsFeed } from "@/types";
+
+const DOMAIN = import.meta.env.SITE;
+const CACHE_DIR = ".data";
+const filePath = `${CACHE_DIR}/webmentions.json`;
+const validWebmentionTypes = ["like-of", "mention-of", "in-reply-to"];
+
+const hostName = new URL(DOMAIN).hostname;
+
+// Calls webmention.io api.
+async function fetchWebmentions(timeFrom: string | null, perPage = 1000) {
+	if (!DOMAIN) {
+		console.warn("No domain specified. Please set in astro.config.ts");
+		return null;
+	}
+
+	if (!WEBMENTION_API_KEY) {
+		console.warn("No webmention api token specified in .env");
+		return null;
+	}
+
+	let url = `https://webmention.io/api/mentions.jf2?domain=${hostName}&token=${WEBMENTION_API_KEY}&sort-dir=up&per-page=${perPage}`;
+
+	if (timeFrom) url += `&since${timeFrom}`;
+
+	const res = await fetch(url);
+
+	if (res.ok) {
+		const data = (await res.json()) as WebmentionsFeed;
+		return data;
+	}
+
+	return null;
+}
+
+// Merge cached entries [a] with fresh webmentions [b], merge by wm-id
+function mergeWebmentions(a: WebmentionsCache, b: WebmentionsFeed): WebmentionsChildren[] {
+	return Array.from(
+		[...a.children, ...b.children]
+			.reduce((map, obj) => map.set(obj["wm-id"], obj), new Map())
+			.values(),
+	);
+}
+
+// filter out WebmentionChildren
+export function filterWebmentions(webmentions: WebmentionsChildren[]) {
+	return webmentions.filter((webmention) => {
+		// make sure the mention has a property so we can sort them later
+		if (!validWebmentionTypes.includes(webmention["wm-property"])) return false;
+
+		// make sure 'mention-of' or 'in-reply-to' has text content.
+		if (webmention["wm-property"] === "mention-of" || webmention["wm-property"] === "in-reply-to") {
+			return webmention.content && webmention.content.text !== "";
+		}
+
+		return true;
+	});
+}
+
+// save combined webmentions in cache file
+function writeToCache(data: WebmentionsCache) {
+	const fileContent = JSON.stringify(data, null, 2);
+
+	// create cache folder if it doesn't exist already
+	if (!fs.existsSync(CACHE_DIR)) {
+		fs.mkdirSync(CACHE_DIR);
+	}
+
+	// write data to cache json file
+	fs.writeFile(filePath, fileContent, (err) => {
+		if (err) throw err;
+		console.log(`Webmentions saved to ${filePath}`);
+	});
+}
+
+function getFromCache(): WebmentionsCache {
+	if (fs.existsSync(filePath)) {
+		const data = fs.readFileSync(filePath, "utf-8");
+		return JSON.parse(data);
+	}
+	// no cache found
+	return {
+		lastFetched: null,
+		children: [],
+	};
+}
+
+async function getAndCacheWebmentions() {
+	const cache = getFromCache();
+	const mentions = await fetchWebmentions(cache.lastFetched);
+
+	if (mentions) {
+		mentions.children = filterWebmentions(mentions.children);
+		const webmentions: WebmentionsCache = {
+			lastFetched: new Date().toISOString(),
+			// Make sure the first arg is the cache
+			children: mergeWebmentions(cache, mentions),
+		};
+
+		writeToCache(webmentions);
+		return webmentions;
+	}
+
+	return cache;
+}
+
+let webMentions: WebmentionsCache;
+
+export async function getWebmentionsForUrl(url: string) {
+	if (!webMentions) webMentions = await getAndCacheWebmentions();
+
+	return webMentions.children.filter((entry) => entry["wm-target"] === url);
+}