[fixes #825] Add ReleaseInfo model

This model contains all the information about a releases

core/src/net/sf/openrocket/communication/ReleaseInfo.java

@@ -0,0 +1,62 @@
+package net.sf.openrocket.communication;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.json.JsonObject;
+
+/**
+ * Class containing info about a GitHub release. All the info is stored in a JSON objects, retrieved using the GitHub
+ * releases API.
+ *
+ * @author Sibo Van Gool <sibo.vangool@hotmail.com>
+ */
+public class ReleaseInfo {
+    // GitHub release JSON object containing all the information about a certain release
+    // You can examine an example object here: https://api.github.com/repos/openrocket/openrocket/releases/latest
+    private final JsonObject obj;
+
+    private static final Logger log = LoggerFactory.getLogger(ReleaseInfo.class);
+
+    public ReleaseInfo(JsonObject obj) {
+        this.obj = obj;
+    }
+
+    /**
+     * Get the release tag from the GitHub release JSON object.
+     * @return release tag (e.g. "15.0.3")
+     */
+    private String getReleaseTag() {
+        if (this.obj == null) return null;
+
+        String tag = this.obj.get("tag_name").toString();        // Release label is encapsulated in the 'tag_name'-tag
+        tag = tag.replaceAll("^\"+|\"+$", "");    // Remove double quotations in the beginning and end
+
+        // Remove the 'release-' preamble of the name tag (example name tag: 'release-15.03')
+        String preamble = "release-";
+        if (tag.startsWith(preamble)) {
+            tag = tag.substring(preamble.length());
+        } else {
+            log.debug("Invalid release tag format for tag: " + tag);
+        }
+        return tag;
+    }
+
+    /**
+     * Get the release notes from the GitHub release JSON object.
+     * @return release notes (this is the text that explains a certain GitHub release)
+     */
+    private String getReleaseNotes() {
+        if (this.obj == null) return null;
+        return this.obj.get("body").toString();
+    }
+
+    /**
+     * Get the release URL from the GitHub release JSON object.
+     * @return release URL (e.g. 'https://github.com/openrocket/openrocket/releases/tag/release-15.03')
+     */
+    private String getReleaseURL() {
+        if (this.obj == null) return null;
+        return this.obj.get("html_url").toString();
+    }
+}