Poll on subscribe; test message

web/src/app/Api.js

@@ -0,0 +1,24 @@
+import {topicUrlJsonPoll, fetchLinesIterator, topicUrl} from "./utils";
+
+class Api {
+    static async poll(baseUrl, topic) {
+        const url = topicUrlJsonPoll(baseUrl, topic);
+        const messages = [];
+        console.log(`[Api] Polling ${url}`);
+        for await (let line of fetchLinesIterator(url)) {
+            messages.push(JSON.parse(line));
+        }
+        return messages.sort((a, b) => { return a.time < b.time ? 1 : -1; }); // Newest first
+    }
+
+    static async publish(baseUrl, topic, message) {
+        const url = topicUrl(baseUrl, topic);
+        console.log(`[Api] Publishing message to ${url}`);
+        await fetch(url, {
+            method: 'PUT',
+            body: message
+        });
+    }
+}
+
+export default Api;

web/src/app/utils.js

@@ -2,5 +2,39 @@ export const topicUrl = (baseUrl, topic) => `${baseUrl}/${topic}`;
 export const topicUrlWs = (baseUrl, topic) => `${topicUrl(baseUrl, topic)}/ws`
     .replaceAll("https://", "wss://")
     .replaceAll("http://", "ws://");
+export const topicUrlJson = (baseUrl, topic) => `${topicUrl(baseUrl, topic)}/json`;
+export const topicUrlJsonPoll = (baseUrl, topic) => `${topicUrlJson(baseUrl, topic)}?poll=1`;
 export const shortUrl = (url) => url.replaceAll(/https?:\/\//g, "");
 export const shortTopicUrl = (baseUrl, topic) => shortUrl(topicUrl(baseUrl, topic));
+
+// From: https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
+export async function* fetchLinesIterator(fileURL) {
+    const utf8Decoder = new TextDecoder('utf-8');
+    const response = await fetch(fileURL);
+    const reader = response.body.getReader();
+    let { value: chunk, done: readerDone } = await reader.read();
+    chunk = chunk ? utf8Decoder.decode(chunk) : '';
+
+    const re = /\n|\r|\r\n/gm;
+    let startIndex = 0;
+    let result;
+
+    for (;;) {
+        let result = re.exec(chunk);
+        if (!result) {
+            if (readerDone) {
+                break;
+            }
+            let remainder = chunk.substr(startIndex);
+            ({ value: chunk, done: readerDone } = await reader.read());
+            chunk = remainder + (chunk ? utf8Decoder.decode(chunk) : '');
+            startIndex = re.lastIndex = 0;
+            continue;
+        }
+        yield chunk.substring(startIndex, result.index);
+        startIndex = re.lastIndex;
+    }
+    if (startIndex < chunk.length) {
+        yield chunk.substr(startIndex); // last line didn't end in a newline char
+    }
+}