1 files changed, 205 insertions, 0 deletions
diff --git a/gerrit-gwtexpui/src/main/java/com/google/gwtexpui/linker/server/PermutationSelector.java b/gerrit-gwtexpui/src/main/java/com/google/gwtexpui/linker/server/PermutationSelector.java
new file mode 100644
index 0000000000..d3e5ae35e4
--- /dev/null
+++ b/gerrit-gwtexpui/src/main/java/com/google/gwtexpui/linker/server/PermutationSelector.java
@@ -0,0 +1,205 @@
+// Copyright (C) 2009 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gwtexpui.linker.server;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+
+/**
+ * Selects a permutation based on the HTTP request.
+ * <p>
+ * To use this class the application's GWT module must include our linker by
+ * inheriting our module:
+ *
+ * <pre>
+ *   &lt;inherits name='com.google.gwtexpui.linker.ServerPlannedIFrameLinker'/&gt;
+ * </pre>
+ */
+public class PermutationSelector {
+  private final String moduleName;
+  private final Map<String, Rule> rulesByName;
+  private final List<Rule> ruleOrder;
+  private final List<Permutation> permutations;
+  private final List<String> css;
+
+  /**
+   * Create an empty selector for a module.
+   * <p>
+   * {@link UserAgentRule} rule is automatically registered. Additional custom
+   * selector rules may be registered before {@link #init(ServletContext)} is
+   * called to finish the selector setup.
+   *
+   * @param moduleName the name of the module within the context.
+   */
+  public PermutationSelector(final String moduleName) {
+    this.moduleName = moduleName;
+
+    this.rulesByName = new HashMap<String, Rule>();
+    this.ruleOrder = new ArrayList<Rule>();
+    this.permutations = new ArrayList<Permutation>();
+    this.css = new ArrayList<String>();
+
+    register(new UserAgentRule());
+  }
+
+  private void notInitialized() {
+    if (!ruleOrder.isEmpty()) {
+      throw new IllegalStateException("Already initialized");
+    }
+  }
+
+  /**
+   * Register a property selection rule.
+   *
+   * @param r the rule implementation.
+   */
+  public void register(Rule r) {
+    notInitialized();
+    rulesByName.put(r.getName(), r);
+  }
+
+  /**
+   * Initialize the selector by reading the module's {@code permutations} file.
+   *
+   * @param ctx context to load the module data from.
+   * @throws ServletException
+   * @throws IOException
+   */
+  public void init(ServletContext ctx) throws ServletException, IOException {
+    notInitialized();
+
+    final String tableName = "/" + moduleName + "/permutations";
+    final InputStream in = ctx.getResourceAsStream(tableName);
+    if (in == null) {
+      throw new ServletException("No " + tableName + " in context");
+    }
+    try {
+      BufferedReader r = new BufferedReader(new InputStreamReader(in, "UTF-8"));
+      for (;;) {
+        final String strongName = r.readLine();
+        if (strongName == null) {
+          break;
+        }
+
+        if (strongName.startsWith("css ")) {
+          css.add(strongName.substring("css ".length()));
+          continue;
+        }
+
+        Map<String, String> selections = new LinkedHashMap<String, String>();
+        for (;;) {
+          String permutation = r.readLine();
+          if (permutation == null || permutation.isEmpty()) {
+            break;
+          }
+
+          int eq = permutation.indexOf('=');
+          if (eq < 0) {
+            throw new ServletException(tableName + " has malformed content");
+          }
+
+          String k = permutation.substring(0, eq).trim();
+          String v = permutation.substring(eq + 1);
+
+          Rule rule = get(k);
+          if (!ruleOrder.contains(rule)) {
+            ruleOrder.add(rule);
+          }
+
+          if (selections.put(k, v) != null) {
+            throw new ServletException("Table " + tableName
+                + " has multiple values for " + k + " within permutation "
+                + strongName);
+          }
+        }
+
+        String cacheHtml = strongName + ".cache.html";
+        String[] values = new String[ruleOrder.size()];
+        for (int i = 0; i < values.length; i++) {
+          values[i] = selections.get(ruleOrder.get(i).getName());
+        }
+        permutations.add(new Permutation(this, cacheHtml, values));
+      }
+    } finally {
+      in.close();
+    }
+  }
+
+  private Rule get(final String name) {
+    Rule r = rulesByName.get(name);
+    if (r == null) {
+      r = new ClientSideRule(name);
+      register(r);
+    }
+    return r;
+  }
+
+  /** @return name of the module (within the application context). */
+  public String getModuleName() {
+    return moduleName;
+  }
+
+  /** @return all possible permutations */
+  public List<Permutation> getPermutations() {
+    return Collections.unmodifiableList(permutations);
+  }
+
+  /**
+   * Select the permutation that best matches the browser request.
+   *
+   * @param req current request.
+   * @return the selected permutation; null if no permutation can be fit to the
+   *         request and the standard {@code nocache.js} loader must be used.
+   */
+  public Permutation select(HttpServletRequest req) {
+    final String[] values = new String[ruleOrder.size()];
+    for (int i = 0; i < values.length; i++) {
+      final String value = ruleOrder.get(i).select(req);
+      if (value == null) {
+        // If the rule returned null it doesn't know how to compute
+        // the value for this HTTP request. Since we can't do that
+        // defer to JavaScript by not picking a permutation.
+        //
+        return null;
+      }
+      values[i] = value;
+    }
+
+    for (Permutation p : permutations) {
+      if (p.matches(values)) {
+        return p;
+      }
+    }
+
+    return null;
+  }
+
+  Collection<String> getCSS() {
+    return css;
+  }
+}