AAPT2: XML configuration file parser.

The XML file is parsed with the aapt::xml::XmlDom parser and actions are
used for the elements we are interested in. This means that there are
cases where a user could add aditional tags/elements to the document
that are technically invalid (acording to the schema) but are ignored by
the parser. This allows us to be more lenient which probably isn't a bad
thing.

Documents have the namespace stripped before processing as the
XmlActionExecutor ignores any elements with a namespace. The namespace
is validated before being removed.

The test cases are all based off the previous example XML file.

Test: Unit tests

Change-Id: I86d7e0dc6347ace3eaa60c1842d59f3cd0d4f749
diff --git a/tools/aapt2/configuration/ConfigurationParser.h b/tools/aapt2/configuration/ConfigurationParser.h
new file mode 100644
index 0000000..0fb2f71
--- /dev/null
+++ b/tools/aapt2/configuration/ConfigurationParser.h
@@ -0,0 +1,216 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#ifndef AAPT2_CONFIGURATION_H
+#define AAPT2_CONFIGURATION_H
+
+#include <string>
+#include <unordered_map>
+#include <vector>
+#include <ConfigDescription.h>
+
+#include "util/Maybe.h"
+
+namespace aapt {
+
+namespace configuration {
+
+/** A mapping of group labels to group of configuration items. */
+template<class T>
+using Group = std::unordered_map<std::string, std::vector<T>>;
+
+/** Output artifact configuration options. */
+struct Artifact {
+  /** Name to use for output of processing foo.apk -> foo.<name>.apk. */
+  std::string name;
+  /** If present, uses the ABI group with this name. */
+  Maybe<std::string> abi_group;
+  /** If present, uses the screen density group with this name. */
+  Maybe<std::string> screen_density_group;
+  /** If present, uses the locale group with this name. */
+  Maybe<std::string> locale_group;
+  /** If present, uses the Android SDK group with this name. */
+  Maybe<std::string> android_sdk_group;
+  /** If present, uses the device feature group with this name. */
+  Maybe<std::string> device_feature_group;
+  /** If present, uses the OpenGL texture group with this name. */
+  Maybe<std::string> gl_texture_group;
+};
+
+/** Enumeration of currently supported ABIs. */
+enum class Abi {
+  kArmeV6,
+  kArmV7a,
+  kArm64V8a,
+  kX86,
+  kX86_64,
+  kMips,
+  kMips64,
+  kUniversal
+};
+
+/**
+ * Represents an individual locale. When a locale is included, it must be
+ * declared from least specific to most specific, as a region does not make
+ * sense without a language. If neither the language or region are specified it
+ * acts as a special case for catch all. This can allow all locales to be kept,
+ * or compressed.
+ */
+struct Locale {
+  /** The ISO<?> standard locale language code. */
+  Maybe<std::string> lang;
+  /** The ISO<?> standard locale region code. */
+  Maybe<std::string> region;
+
+  inline friend bool operator==(const Locale& lhs, const Locale& rhs) {
+    return lhs.lang == rhs.lang && lhs.region == rhs.region;
+  }
+};
+
+// TODO: Encapsulate manifest modifications from the configuration file.
+struct AndroidManifest {
+  inline friend bool operator==(const AndroidManifest& lhs, const AndroidManifest& rhs) {
+    return true;  // nothing to compare yet.
+  }
+};
+
+struct AndroidSdk {
+  Maybe<std::string> min_sdk_version;
+  Maybe<std::string> target_sdk_version;
+  Maybe<std::string> max_sdk_version;
+  Maybe<AndroidManifest> manifest;
+
+  inline friend bool operator==(const AndroidSdk& lhs, const AndroidSdk& rhs) {
+    return lhs.min_sdk_version == rhs.min_sdk_version &&
+        lhs.target_sdk_version == rhs.target_sdk_version &&
+        lhs.max_sdk_version == rhs.max_sdk_version &&
+        lhs.manifest == rhs.manifest;
+  }
+};
+
+// TODO: Make device features more than just an arbitrary string?
+using DeviceFeature = std::string;
+
+/** Represents a mapping of texture paths to a GL texture format. */
+struct GlTexture {
+  std::string name;
+  std::vector<std::string> texture_paths;
+
+  inline friend bool operator==(const GlTexture& lhs, const GlTexture& rhs) {
+    return lhs.name == rhs.name && lhs.texture_paths == rhs.texture_paths;
+  }
+};
+
+/**
+ * AAPT2 XML configuration binary representation.
+ */
+struct Configuration {
+  std::unordered_map<std::string, Artifact> artifacts;
+  Maybe<std::string> artifact_format;
+
+  Group<Abi> abi_groups;
+  Group<ConfigDescription> screen_density_groups;
+  Group<Locale> locale_groups;
+  Group<AndroidSdk> android_sdk_groups;
+  Group<DeviceFeature> device_feature_groups;
+  Group<GlTexture> gl_texture_groups;
+};
+
+}  // namespace configuration
+
+// Forward declaration of classes used in the API.
+struct IDiagnostics;
+namespace xml {
+class Element;
+}
+
+/**
+ * XML configuration file parser for the split and optimize commands.
+ */
+class ConfigurationParser {
+ public:
+  /** Returns a ConfigurationParser for the configuration in the provided file contents. */
+  static ConfigurationParser ForContents(const std::string& contents) {
+    ConfigurationParser parser{contents};
+    return parser;
+  }
+
+  /** Returns a ConfigurationParser for the file located at the provided path. */
+  static ConfigurationParser ForPath(const std::string& path) {
+    // TODO: Read XML file into memory.
+    return ForContents(path);
+  }
+
+  /** Sets the diagnostics context to use when parsing. */
+  ConfigurationParser& WithDiagnostics(IDiagnostics* diagnostics) {
+    diag_ = diagnostics;
+    return *this;
+  }
+
+  /**
+   * Parses the configuration file and returns the results. If the configuration could not be parsed
+   * the result is empty and any errors will be displayed with the provided diagnostics context.
+   */
+  Maybe<configuration::Configuration> Parse();
+
+ protected:
+  /**
+   * Instantiates a new ConfigurationParser with the provided configuration file and a no-op
+   * diagnostics context. The default diagnostics context can be overridden with a call to
+   * WithDiagnostics(IDiagnostics *).
+   */
+  explicit ConfigurationParser(std::string contents);
+
+  /** Returns the current diagnostics context to any subclasses. */
+  IDiagnostics* diagnostics() {
+    return diag_;
+  }
+
+  /**
+   * An ActionHandler for processing XML elements in the XmlActionExecutor. Returns true if the
+   * element was successfully processed, otherwise returns false.
+   */
+  using ActionHandler = std::function<bool(configuration::Configuration* config,
+                                           xml::Element* element,
+                                           IDiagnostics* diag)>;
+
+  /** Handler for <artifact> tags. */
+  static ActionHandler artifact_handler_;
+  /** Handler for <artifact-format> tags. */
+  static ActionHandler artifact_format_handler_;
+  /** Handler for <abi-group> tags. */
+  static ActionHandler abi_group_handler_;
+  /** Handler for <screen-density-group> tags. */
+  static ActionHandler screen_density_group_handler_;
+  /** Handler for <locale-group> tags. */
+  static ActionHandler locale_group_handler_;
+  /** Handler for <android-sdk-group> tags. */
+  static ActionHandler android_sdk_group_handler_;
+  /** Handler for <gl-texture-group> tags. */
+  static ActionHandler gl_texture_group_handler_;
+  /** Handler for <device-feature-group> tags. */
+  static ActionHandler device_feature_group_handler_;
+
+ private:
+  /** The contents of the configuration file to parse. */
+  const std::string contents_;
+  /** The diagnostics context to send messages to. */
+  IDiagnostics* diag_;
+};
+
+}  // namespace aapt
+
+#endif //AAPT2_CONFIGURATION_H