1 files changed, 77 insertions, 0 deletions
diff --git a/src/requests.js b/src/requests.js
new file mode 100644
index 0000000..06c5577
--- /dev/null
+++ b/src/requests.js
@@ -0,0 +1,77 @@
+const { app } = require("electron");
+const path = require("path");
+const fs = require("fs");
+const { https } = require("follow-redirects");
+
+
+// all requests results are stored in this file
+const cachePath = path.join(app.getPath("cache"), "requests.json");
+const NORTHSTAR_LATEST_RELEASE_KEY = "nsLatestRelease";
+
+
+function _saveCache(data) {
+    fs.writeFileSync(cachePath, JSON.stringify(data));
+}
+
+function _getRequestsCache() {
+    if (fs.existsSync(cachePath)) {
+        return JSON.parse(fs.readFileSync(cachePath, "utf8"));
+    } else {
+        fs.writeFileSync(cachePath, "{}");
+        return {};
+    }
+}
+
+// Returns latest Northstar version available from GitHub releases. If
+// there's no cache result for this request, or if cache exists but is
+// old, refreshes cache with new data.
+async function getLatestNsVersion() {
+    return new Promise((resolve, reject) => {
+        let cache = _getRequestsCache();
+    
+        if (cache[NORTHSTAR_LATEST_RELEASE_KEY] && (Date.now() - cache[NORTHSTAR_LATEST_RELEASE_KEY]["time"]) < 5 * 60 * 1000) {
+            console.log(`returning ${NORTHSTAR_LATEST_RELEASE_KEY} data from cache`);
+            resolve( cache[NORTHSTAR_LATEST_RELEASE_KEY]["body"]["tag_name"] );
+        } else {
+            https.get({
+                host: "api.github.com",
+                port: 443,
+                path: "/repos/R2Northstar/Northstar/releases/latest",
+                method: "GET",
+                headers: { "User-Agent": "viper" }
+            }, 
+            
+            response => {
+                response.setEncoding("utf8");
+                let responseData = "";
+
+                response.on("data", data => {
+                    responseData += data;
+                });
+
+                response.on("end", _ => {                    
+                    cache[NORTHSTAR_LATEST_RELEASE_KEY] = {
+                        "time": Date.now(),
+                        "body": JSON.parse(responseData)
+                    };
+                    _saveCache(cache);
+                    resolve( cache[NORTHSTAR_LATEST_RELEASE_KEY]["body"]["tag_name"] );
+                });
+            });
+        }
+    });
+}
+
+// Returns the download link to latest Northstar version. Should always
+// be called after getLatestNsVersion, as it refreshes cache data (if
+// needed).
+function getLatestNsVersionLink() {
+    const cache = _getRequestsCache();
+    return cache[NORTHSTAR_LATEST_RELEASE_KEY]["body"].assets[0].browser_download_url;
+}
+
+
+module.exports = {
+    getLatestNsVersion, 
+    getLatestNsVersionLink
+};