1 files changed, 140 insertions, 0 deletions
diff --git a/src/io/AbstractRequester.java b/src/io/AbstractRequester.java
new file mode 100644
index 0000000..bdd7052
--- /dev/null
+++ b/src/io/AbstractRequester.java
@@ -0,0 +1,140 @@
+package io;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.StringWriter;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.net.URLConnection;
+import java.util.logging.Logger;
+import org.apache.commons.io.Charsets;
+import org.apache.commons.io.IOUtils;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+/**
+ * Performs an API Request.
+ *
+ * @author Peter Wu
+ */
+public abstract class AbstractRequester implements Requester {
+
+    private static final String API_URL = "https://api.twitter.com/";
+
+    @Override
+    public JSONObject getJSON(String resource) throws IOException {
+        return getJSON(resource, true);
+    }
+
+    @Override
+    public JSONObject getJSONRelax(String resource) throws IOException {
+        return getJSON(resource, false);
+    }
+
+    private JSONObject getJSON(String resource, boolean checkStatusCode)
+            throws IOException {
+        HttpURLConnection conn = open(buildUrl(resource));
+        preconnect(conn);
+        JSONObject resp = getResponseAsJson(conn);
+        /* print response to stderr for debugging */
+        if (resp.has("errors")) {
+            try {
+                String errors = resp.get("errors").toString();
+                getLogger().info("Request failed: " + errors);
+            } catch (JSONException ex) {
+            }
+        }
+        // TODO: what if there is an internal server error? Technically we
+        // should always treat that as "don't know what the server thinks".
+        if (checkStatusCode && conn.getResponseCode() != 200) {
+            // TODO: print more helpful details
+            throw new IOException("Unexpected response code");
+        }
+        return resp;
+    }
+
+    protected final URL buildUrl(String resource) throws IOException {
+        String spec = API_URL;
+        String[] split = resource.split("\\?", 2);
+        boolean isPreV1;
+        isPreV1 = resource.startsWith("oauth/") || resource.startsWith("oauth2/");
+        if (!isPreV1 && !resource.startsWith("1")) {
+            // manual inspection shows that at least oauth/ and oauth2/ do not
+            // have a version prefixed. Do not add version if already given
+            // (e.g. "1/account/rate_limit_status").
+            spec += "1.1/";
+        }
+        // path part
+        spec += split[0];
+        if (!isPreV1) {
+            // not sure about the history, but oauth{,2}/ don't have this.
+            spec += ".json";
+        }
+
+        // append parameters after path
+        if (split.length >= 2) {
+            spec += "?" + split[1];
+        }
+
+        return new URL(spec);
+    }
+
+    /**
+     * Opens a connection to the URL.
+     *
+     * @param url The URL to open a connection to.
+     * @return a connection that can be used for sending requests.
+     * @throws java.io.IOException on failure to open a connection.
+     */
+    protected final HttpURLConnection open(URL url) throws IOException {
+        getLogger().fine("Opening: " + url);
+        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
+        // set default param: fail if no response within 5 seconds
+        conn.setReadTimeout(5000);
+        return conn;
+    }
+
+    /**
+     * Reads the response body from a connection (in JSON format).
+     *
+     * @param conn An open connection to which a request was already made.
+     * @return A JSON object as parsed from the response.
+     * @throws java.io.IOException if the response cannot be retrieved or if the
+     * response does not contain well-formed JSON.
+     */
+    protected final JSONObject getResponseAsJson(HttpURLConnection conn)
+            throws IOException {
+        StringWriter writer = new StringWriter();
+        InputStream is;
+        try {
+            is = conn.getInputStream();
+        } catch (IOException ex) {
+            /* 404 (FileNotFoundException) */
+            is = conn.getErrorStream();
+        }
+        // this could happen if the URL was severly malformed
+        if (is == null) {
+            throw new IOException("Failed to fetch response");
+        }
+        IOUtils.copy(is, writer, Charsets.UTF_8);
+        try {
+            return new JSONObject(writer.toString());
+        } catch (JSONException ex) {
+            // treat JSON errors as if an I/O error occurred
+            throw new IOException(ex);
+        }
+    }
+
+    /**
+     * Prepare the request before it gets send.
+     *
+     * @param conn A connection for the request.
+     * @throws java.io.IOException on failing to prepare the request.
+     */
+    protected abstract void preconnect(URLConnection conn)
+            throws IOException;
+
+    private Logger getLogger() {
+        return Logger.getLogger(getClass().getName());
+    }
+}