AAPT2: Separate out the various steps

An early refactor. Some ideas became clearer as
development continued. Now the various phases are much
clearer and more easily reusable.

Also added a ton of tests!

Change-Id: Ic8f0a70c8222370352e63533b329c40457c0903e
diff --git a/tools/aapt2/Main.cpp b/tools/aapt2/Main.cpp
index 54a7329..248e7ad 100644
--- a/tools/aapt2/Main.cpp
+++ b/tools/aapt2/Main.cpp
@@ -14,1262 +14,39 @@
  * limitations under the License.
  */
 
-#include "AppInfo.h"
-#include "BigBuffer.h"
-#include "BinaryResourceParser.h"
-#include "BindingXmlPullParser.h"
-#include "Debug.h"
-#include "Files.h"
-#include "Flag.h"
-#include "JavaClassGenerator.h"
-#include "Linker.h"
-#include "ManifestMerger.h"
-#include "ManifestParser.h"
-#include "ManifestValidator.h"
-#include "NameMangler.h"
-#include "Png.h"
-#include "ProguardRules.h"
-#include "ResourceParser.h"
-#include "ResourceTable.h"
-#include "ResourceTableResolver.h"
-#include "ResourceValues.h"
-#include "SdkConstants.h"
-#include "SourceXmlPullParser.h"
-#include "StringPiece.h"
-#include "TableFlattener.h"
-#include "Util.h"
-#include "XmlFlattener.h"
-#include "ZipFile.h"
+#include "util/StringPiece.h"
 
-#include <algorithm>
-#include <androidfw/AssetManager.h>
-#include <cstdlib>
-#include <dirent.h>
-#include <errno.h>
-#include <fstream>
 #include <iostream>
-#include <sstream>
-#include <sys/stat.h>
-#include <unordered_set>
-#include <utils/Errors.h>
+#include <vector>
 
-constexpr const char* kAaptVersionStr = "2.0-alpha";
+namespace aapt {
 
-using namespace aapt;
+extern int compile(const std::vector<StringPiece>& args);
+extern int link(const std::vector<StringPiece>& args);
 
-/**
- * Used with smart pointers to free malloc'ed memory.
- */
-struct DeleteMalloc {
-    void operator()(void* ptr) {
-        free(ptr);
-    }
-};
-
-struct StaticLibraryData {
-    Source source;
-    std::unique_ptr<ZipFile> apk;
-};
-
-/**
- * Collect files from 'root', filtering out any files that do not
- * match the FileFilter 'filter'.
- */
-bool walkTree(const Source& root, const FileFilter& filter,
-              std::vector<Source>* outEntries) {
-    bool error = false;
-
-    for (const std::string& dirName : listFiles(root.path)) {
-        std::string dir = root.path;
-        appendPath(&dir, dirName);
-
-        FileType ft = getFileType(dir);
-        if (!filter(dirName, ft)) {
-            continue;
-        }
-
-        if (ft != FileType::kDirectory) {
-            continue;
-        }
-
-        for (const std::string& fileName : listFiles(dir)) {
-            std::string file(dir);
-            appendPath(&file, fileName);
-
-            FileType ft = getFileType(file);
-            if (!filter(fileName, ft)) {
-                continue;
-            }
-
-            if (ft != FileType::kRegular) {
-                Logger::error(Source{ file }) << "not a regular file." << std::endl;
-                error = true;
-                continue;
-            }
-            outEntries->push_back(Source{ file });
-        }
-    }
-    return !error;
-}
-
-void versionStylesForCompat(const std::shared_ptr<ResourceTable>& table) {
-    for (auto& type : *table) {
-        if (type->type != ResourceType::kStyle) {
-            continue;
-        }
-
-        for (auto& entry : type->entries) {
-            // Add the versioned styles we want to create
-            // here. They are added to the table after
-            // iterating over the original set of styles.
-            //
-            // A stack is used since auto-generated styles
-            // from later versions should override
-            // auto-generated styles from earlier versions.
-            // Iterating over the styles is done in order,
-            // so we will always visit sdkVersions from smallest
-            // to largest.
-            std::stack<ResourceConfigValue> addStack;
-
-            for (ResourceConfigValue& configValue : entry->values) {
-                visitFunc<Style>(*configValue.value, [&](Style& style) {
-                    // Collect which entries we've stripped and the smallest
-                    // SDK level which was stripped.
-                    size_t minSdkStripped = std::numeric_limits<size_t>::max();
-                    std::vector<Style::Entry> stripped;
-
-                    // Iterate over the style's entries and erase/record the
-                    // attributes whose SDK level exceeds the config's sdkVersion.
-                    auto iter = style.entries.begin();
-                    while (iter != style.entries.end()) {
-                        if (iter->key.name.package == u"android") {
-                            size_t sdkLevel = findAttributeSdkLevel(iter->key.name);
-                            if (sdkLevel > 1 && sdkLevel > configValue.config.sdkVersion) {
-                                // Record that we are about to strip this.
-                                stripped.emplace_back(std::move(*iter));
-                                minSdkStripped = std::min(minSdkStripped, sdkLevel);
-
-                                // Erase this from this style.
-                                iter = style.entries.erase(iter);
-                                continue;
-                            }
-                        }
-                        ++iter;
-                    }
-
-                    if (!stripped.empty()) {
-                        // We have stripped attributes, so let's create a new style to hold them.
-                        ConfigDescription versionConfig(configValue.config);
-                        versionConfig.sdkVersion = minSdkStripped;
-
-                        ResourceConfigValue value = {
-                                versionConfig,
-                                configValue.source,
-                                {},
-
-                                // Create a copy of the original style.
-                                std::unique_ptr<Value>(configValue.value->clone(
-                                            &table->getValueStringPool()))
-                        };
-
-                        Style& newStyle = static_cast<Style&>(*value.value);
-
-                        // Move the recorded stripped attributes into this new style.
-                        std::move(stripped.begin(), stripped.end(),
-                                  std::back_inserter(newStyle.entries));
-
-                        // We will add this style to the table later. If we do it now, we will
-                        // mess up iteration.
-                        addStack.push(std::move(value));
-                    }
-                });
-            }
-
-            auto comparator =
-                    [](const ResourceConfigValue& lhs, const ConfigDescription& rhs) -> bool {
-                        return lhs.config < rhs;
-                    };
-
-            while (!addStack.empty()) {
-                ResourceConfigValue& value = addStack.top();
-                auto iter = std::lower_bound(entry->values.begin(), entry->values.end(),
-                                             value.config, comparator);
-                if (iter == entry->values.end() || iter->config != value.config) {
-                    entry->values.insert(iter, std::move(value));
-                }
-                addStack.pop();
-            }
-        }
-    }
-}
-
-struct CompileItem {
-    ResourceName name;
-    ConfigDescription config;
-    Source source;
-    std::string extension;
-};
-
-struct LinkItem {
-    ResourceName name;
-    ConfigDescription config;
-    Source source;
-    std::string originalPath;
-    ZipFile* apk;
-    std::u16string originalPackage;
-};
-
-template <typename TChar>
-static BasicStringPiece<TChar> getExtension(const BasicStringPiece<TChar>& str) {
-    auto iter = std::find(str.begin(), str.end(), static_cast<TChar>('.'));
-    if (iter == str.end()) {
-        return BasicStringPiece<TChar>();
-    }
-    size_t offset = (iter - str.begin()) + 1;
-    return str.substr(offset, str.size() - offset);
-}
-
-std::string buildFileReference(const ResourceNameRef& name, const ConfigDescription& config,
-                               const StringPiece& extension) {
-    std::stringstream path;
-    path << "res/" << name.type;
-    if (config != ConfigDescription{}) {
-        path << "-" << config;
-    }
-    path << "/" << util::utf16ToUtf8(name.entry);
-    if (!extension.empty()) {
-        path << "." << extension;
-    }
-    return path.str();
-}
-
-std::string buildFileReference(const CompileItem& item) {
-    return buildFileReference(item.name, item.config, item.extension);
-}
-
-std::string buildFileReference(const LinkItem& item) {
-    return buildFileReference(item.name, item.config, getExtension<char>(item.originalPath));
-}
-
-template <typename T>
-bool addFileReference(const std::shared_ptr<ResourceTable>& table, const T& item) {
-    StringPool& pool = table->getValueStringPool();
-    StringPool::Ref ref = pool.makeRef(util::utf8ToUtf16(buildFileReference(item)),
-                                       StringPool::Context{ 0, item.config });
-    return table->addResource(item.name, item.config, item.source.line(0),
-                              util::make_unique<FileReference>(ref));
-}
-
-struct AaptOptions {
-    enum class Phase {
-        Link,
-        Compile,
-        Dump,
-        DumpStyleGraph,
-    };
-
-    enum class PackageType {
-        StandardApp,
-        StaticLibrary,
-    };
-
-    // The phase to process.
-    Phase phase;
-
-    // The type of package to produce.
-    PackageType packageType = PackageType::StandardApp;
-
-    // Details about the app.
-    AppInfo appInfo;
-
-    // The location of the manifest file.
-    Source manifest;
-
-    // The APK files to link.
-    std::vector<Source> input;
-
-    // The libraries these files may reference.
-    std::vector<Source> libraries;
-
-    // Output path. This can be a directory or file
-    // depending on the phase.
-    Source output;
-
-    // Directory in which to write binding xml files.
-    Source bindingOutput;
-
-    // Directory to in which to generate R.java.
-    Maybe<Source> generateJavaClass;
-
-    // File in which to produce proguard rules.
-    Maybe<Source> generateProguardRules;
-
-    // Whether to output verbose details about
-    // compilation.
-    bool verbose = false;
-
-    // Whether or not to auto-version styles or layouts
-    // referencing attributes defined in a newer SDK
-    // level than the style or layout is defined for.
-    bool versionStylesAndLayouts = true;
-
-    // The target style that will have it's style hierarchy dumped
-    // when the phase is DumpStyleGraph.
-    ResourceName dumpStyleTarget;
-};
-
-struct IdCollector : public xml::Visitor {
-    IdCollector(const Source& source, const std::shared_ptr<ResourceTable>& table) :
-            mSource(source), mTable(table) {
-    }
-
-    virtual void visit(xml::Text* node) override {}
-
-    virtual void visit(xml::Namespace* node) override {
-        for (const auto& child : node->children) {
-            child->accept(this);
-        }
-    }
-
-    virtual void visit(xml::Element* node) override {
-        for (const xml::Attribute& attr : node->attributes) {
-            bool create = false;
-            bool priv = false;
-            ResourceNameRef nameRef;
-            if (ResourceParser::tryParseReference(attr.value, &nameRef, &create, &priv)) {
-                if (create) {
-                    mTable->addResource(nameRef, {}, mSource.line(node->lineNumber),
-                                        util::make_unique<Id>());
-                }
-            }
-        }
-
-        for (const auto& child : node->children) {
-            child->accept(this);
-        }
-    }
-
-private:
-    Source mSource;
-    std::shared_ptr<ResourceTable> mTable;
-};
-
-bool compileXml(const AaptOptions& options, const std::shared_ptr<ResourceTable>& table,
-                const CompileItem& item, ZipFile* outApk) {
-    std::ifstream in(item.source.path, std::ifstream::binary);
-    if (!in) {
-        Logger::error(item.source) << strerror(errno) << std::endl;
-        return false;
-    }
-
-    SourceLogger logger(item.source);
-    std::unique_ptr<xml::Node> root = xml::inflate(&in, &logger);
-    if (!root) {
-        return false;
-    }
-
-    // Collect any resource ID's declared here.
-    IdCollector idCollector(item.source, table);
-    root->accept(&idCollector);
-
-    BigBuffer outBuffer(1024);
-    if (!xml::flatten(root.get(), options.appInfo.package, &outBuffer)) {
-        logger.error() << "failed to encode XML." << std::endl;
-        return false;
-    }
-
-    // Write the resulting compiled XML file to the output APK.
-    if (outApk->add(outBuffer, buildFileReference(item).data(), ZipEntry::kCompressStored,
-                nullptr) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to write compiled '" << item.source
-                                      << "' to apk." << std::endl;
-        return false;
-    }
-    return true;
-}
-
-/**
- * Determines if a layout should be auto generated based on SDK level. We do not
- * generate a layout if there is already a layout defined whose SDK version is greater than
- * the one we want to generate.
- */
-bool shouldGenerateVersionedResource(const std::shared_ptr<const ResourceTable>& table,
-                                     const ResourceName& name, const ConfigDescription& config,
-                                     int sdkVersionToGenerate) {
-    assert(sdkVersionToGenerate > config.sdkVersion);
-    const ResourceTableType* type;
-    const ResourceEntry* entry;
-    std::tie(type, entry) = table->findResource(name);
-    assert(type && entry);
-
-    auto iter = std::lower_bound(entry->values.begin(), entry->values.end(), config,
-            [](const ResourceConfigValue& lhs, const ConfigDescription& config) -> bool {
-        return lhs.config < config;
-    });
-
-    assert(iter != entry->values.end());
-    ++iter;
-
-    if (iter == entry->values.end()) {
-        return true;
-    }
-
-    ConfigDescription newConfig = config;
-    newConfig.sdkVersion = sdkVersionToGenerate;
-    return newConfig < iter->config;
-}
-
-bool linkXml(const AaptOptions& options, const std::shared_ptr<ResourceTable>& table,
-             const std::shared_ptr<IResolver>& resolver, const LinkItem& item,
-             const void* data, size_t dataLen, ZipFile* outApk, std::queue<LinkItem>* outQueue,
-             proguard::KeepSet* keepSet) {
-    SourceLogger logger(item.source);
-    std::unique_ptr<xml::Node> root = xml::inflate(data, dataLen, &logger);
-    if (!root) {
-        return false;
-    }
-
-    xml::FlattenOptions xmlOptions;
-    if (options.packageType == AaptOptions::PackageType::StaticLibrary) {
-        xmlOptions.keepRawValues = true;
-    }
-
-    if (options.versionStylesAndLayouts) {
-        // We strip attributes that do not belong in this version of the resource.
-        // Non-version qualified resources have an implicit version 1 requirement.
-        xmlOptions.maxSdkAttribute = item.config.sdkVersion ? item.config.sdkVersion : 1;
-    }
-
-    if (options.generateProguardRules) {
-        proguard::collectProguardRules(item.name.type, item.source, root.get(), keepSet);
-    }
-
-    BigBuffer outBuffer(1024);
-    Maybe<size_t> minStrippedSdk = xml::flattenAndLink(item.source, root.get(),
-                                                       item.originalPackage, resolver,
-                                                       xmlOptions, &outBuffer);
-    if (!minStrippedSdk) {
-        logger.error() << "failed to encode XML." << std::endl;
-        return false;
-    }
-
-    if (minStrippedSdk.value() > 0) {
-        // Something was stripped, so let's generate a new file
-        // with the version of the smallest SDK version stripped.
-        // We can only generate a versioned layout if there doesn't exist a layout
-        // with sdk version greater than the current one but less than the one we
-        // want to generate.
-        if (shouldGenerateVersionedResource(table, item.name, item.config,
-                    minStrippedSdk.value())) {
-            LinkItem newWork = item;
-            newWork.config.sdkVersion = minStrippedSdk.value();
-            outQueue->push(newWork);
-
-            if (!addFileReference(table, newWork)) {
-                Logger::error(options.output) << "failed to add auto-versioned resource '"
-                                              << newWork.name << "'." << std::endl;
-                return false;
-            }
-        }
-    }
-
-    if (outApk->add(outBuffer, buildFileReference(item).data(), ZipEntry::kCompressDeflated,
-                nullptr) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to write linked file '"
-                                      << buildFileReference(item) << "' to apk." << std::endl;
-        return false;
-    }
-    return true;
-}
-
-bool compilePng(const AaptOptions& options, const CompileItem& item, ZipFile* outApk) {
-    std::ifstream in(item.source.path, std::ifstream::binary);
-    if (!in) {
-        Logger::error(item.source) << strerror(errno) << std::endl;
-        return false;
-    }
-
-    BigBuffer outBuffer(4096);
-    std::string err;
-    Png png;
-    if (!png.process(item.source, in, &outBuffer, {}, &err)) {
-        Logger::error(item.source) << err << std::endl;
-        return false;
-    }
-
-    if (outApk->add(outBuffer, buildFileReference(item).data(), ZipEntry::kCompressStored,
-                nullptr) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to write compiled '" << item.source
-                                      << "' to apk." << std::endl;
-        return false;
-    }
-    return true;
-}
-
-bool copyFile(const AaptOptions& options, const CompileItem& item, ZipFile* outApk) {
-    if (outApk->add(item.source.path.data(), buildFileReference(item).data(),
-                ZipEntry::kCompressStored, nullptr) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to copy file '" << item.source << "' to apk."
-                                      << std::endl;
-        return false;
-    }
-    return true;
-}
-
-bool compileManifest(const AaptOptions& options, const std::shared_ptr<IResolver>& resolver,
-                     const std::map<std::shared_ptr<ResourceTable>, StaticLibraryData>& libApks,
-                     const android::ResTable& table, ZipFile* outApk, proguard::KeepSet* keepSet) {
-    if (options.verbose) {
-        Logger::note(options.manifest) << "compiling AndroidManifest.xml." << std::endl;
-    }
-
-    std::ifstream in(options.manifest.path, std::ifstream::binary);
-    if (!in) {
-        Logger::error(options.manifest) << strerror(errno) << std::endl;
-        return false;
-    }
-
-    SourceLogger logger(options.manifest);
-    std::unique_ptr<xml::Node> root = xml::inflate(&in, &logger);
-    if (!root) {
-        return false;
-    }
-
-    ManifestMerger merger({});
-    if (!merger.setAppManifest(options.manifest, options.appInfo.package, std::move(root))) {
-        return false;
-    }
-
-    for (const auto& entry : libApks) {
-        ZipFile* libApk = entry.second.apk.get();
-        const std::u16string& libPackage = entry.first->getPackage();
-        const Source& libSource = entry.second.source;
-
-        ZipEntry* zipEntry = libApk->getEntryByName("AndroidManifest.xml");
-        if (!zipEntry) {
-            continue;
-        }
-
-        std::unique_ptr<void, DeleteMalloc> uncompressedData = std::unique_ptr<void, DeleteMalloc>(
-                libApk->uncompress(zipEntry));
-        assert(uncompressedData);
-
-        SourceLogger logger(libSource);
-        std::unique_ptr<xml::Node> libRoot = xml::inflate(uncompressedData.get(),
-                                                          zipEntry->getUncompressedLen(), &logger);
-        if (!libRoot) {
-            return false;
-        }
-
-        if (!merger.mergeLibraryManifest(libSource, libPackage, std::move(libRoot))) {
-            return false;
-        }
-    }
-
-    if (options.generateProguardRules) {
-        proguard::collectProguardRulesForManifest(options.manifest, merger.getMergedXml(),
-                                                  keepSet);
-    }
-
-    BigBuffer outBuffer(1024);
-    if (!xml::flattenAndLink(options.manifest, merger.getMergedXml(), options.appInfo.package,
-                resolver, {}, &outBuffer)) {
-        return false;
-    }
-
-    std::unique_ptr<uint8_t[]> data = util::copy(outBuffer);
-
-    android::ResXMLTree tree;
-    if (tree.setTo(data.get(), outBuffer.size(), false) != android::NO_ERROR) {
-        return false;
-    }
-
-    ManifestValidator validator(table);
-    if (!validator.validate(options.manifest, &tree)) {
-        return false;
-    }
-
-    if (outApk->add(data.get(), outBuffer.size(), "AndroidManifest.xml",
-                ZipEntry::kCompressStored, nullptr) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to write 'AndroidManifest.xml' to apk."
-                                      << std::endl;
-        return false;
-    }
-    return true;
-}
-
-static bool compileValues(const std::shared_ptr<ResourceTable>& table, const Source& source,
-                          const ConfigDescription& config) {
-    std::ifstream in(source.path, std::ifstream::binary);
-    if (!in) {
-        Logger::error(source) << strerror(errno) << std::endl;
-        return false;
-    }
-
-    std::shared_ptr<XmlPullParser> xmlParser = std::make_shared<SourceXmlPullParser>(in);
-    ResourceParser parser(table, source, config, xmlParser);
-    return parser.parse();
-}
-
-struct ResourcePathData {
-    std::u16string resourceDir;
-    std::u16string name;
-    std::string extension;
-    ConfigDescription config;
-};
-
-/**
- * Resource file paths are expected to look like:
- * [--/res/]type[-config]/name
- */
-static Maybe<ResourcePathData> extractResourcePathData(const Source& source) {
-    // TODO(adamlesinski): Use Windows path separator on windows.
-    std::vector<std::string> parts = util::splitAndLowercase(source.path, '/');
-    if (parts.size() < 2) {
-        Logger::error(source) << "bad resource path." << std::endl;
-        return {};
-    }
-
-    std::string& dir = parts[parts.size() - 2];
-    StringPiece dirStr = dir;
-
-    ConfigDescription config;
-    size_t dashPos = dir.find('-');
-    if (dashPos != std::string::npos) {
-        StringPiece configStr = dirStr.substr(dashPos + 1, dir.size() - (dashPos + 1));
-        if (!ConfigDescription::parse(configStr, &config)) {
-            Logger::error(source)
-                    << "invalid configuration '"
-                    << configStr
-                    << "'."
-                    << std::endl;
-            return {};
-        }
-        dirStr = dirStr.substr(0, dashPos);
-    }
-
-    std::string& filename = parts[parts.size() - 1];
-    StringPiece name = filename;
-    StringPiece extension;
-    size_t dotPos = filename.find('.');
-    if (dotPos != std::string::npos) {
-        extension = name.substr(dotPos + 1, filename.size() - (dotPos + 1));
-        name = name.substr(0, dotPos);
-    }
-
-    return ResourcePathData{
-            util::utf8ToUtf16(dirStr),
-            util::utf8ToUtf16(name),
-            extension.toString(),
-            config
-    };
-}
-
-bool writeResourceTable(const AaptOptions& options, const std::shared_ptr<ResourceTable>& table,
-                        const TableFlattener::Options& flattenerOptions, ZipFile* outApk) {
-    if (table->begin() != table->end()) {
-        BigBuffer buffer(1024);
-        TableFlattener flattener(flattenerOptions);
-        if (!flattener.flatten(&buffer, *table)) {
-            Logger::error() << "failed to flatten resource table." << std::endl;
-            return false;
-        }
-
-        if (options.verbose) {
-            Logger::note() << "Final resource table size=" << util::formatSize(buffer.size())
-                           << std::endl;
-        }
-
-        if (outApk->add(buffer, "resources.arsc", ZipEntry::kCompressStored, nullptr) !=
-                android::NO_ERROR) {
-            Logger::note(options.output) << "failed to store resource table." << std::endl;
-            return false;
-        }
-    }
-    return true;
-}
-
-/**
- * For each FileReference in the table, adds a LinkItem to the link queue for processing.
- */
-static void addApkFilesToLinkQueue(const std::u16string& package, const Source& source,
-                                   const std::shared_ptr<ResourceTable>& table,
-                                   const std::unique_ptr<ZipFile>& apk,
-                                   std::queue<LinkItem>* outLinkQueue) {
-    bool mangle = package != table->getPackage();
-    for (auto& type : *table) {
-        for (auto& entry : type->entries) {
-            ResourceName name = { package, type->type, entry->name };
-            if (mangle) {
-                NameMangler::mangle(table->getPackage(), &name.entry);
-            }
-
-            for (auto& value : entry->values) {
-                visitFunc<FileReference>(*value.value, [&](FileReference& ref) {
-                    std::string pathUtf8 = util::utf16ToUtf8(*ref.path);
-                    Source newSource = source;
-                    newSource.path += "/";
-                    newSource.path += pathUtf8;
-                    outLinkQueue->push(LinkItem{
-                            name, value.config, newSource, pathUtf8, apk.get(),
-                            table->getPackage() });
-                    // Now rewrite the file path.
-                    if (mangle) {
-                        ref.path = table->getValueStringPool().makeRef(util::utf8ToUtf16(
-                                    buildFileReference(name, value.config,
-                                                       getExtension<char>(pathUtf8))));
-                    }
-                });
-            }
-        }
-    }
-}
-
-static constexpr int kOpenFlags = ZipFile::kOpenCreate | ZipFile::kOpenTruncate |
-        ZipFile::kOpenReadWrite;
-
-bool link(const AaptOptions& options, const std::shared_ptr<ResourceTable>& outTable,
-          const std::shared_ptr<IResolver>& resolver) {
-    std::map<std::shared_ptr<ResourceTable>, StaticLibraryData> apkFiles;
-    std::unordered_set<std::u16string> linkedPackages;
-
-    // Populate the linkedPackages with our own.
-    linkedPackages.insert(options.appInfo.package);
-
-    // Load all APK files.
-    for (const Source& source : options.input) {
-        std::unique_ptr<ZipFile> zipFile = util::make_unique<ZipFile>();
-        if (zipFile->open(source.path.data(), ZipFile::kOpenReadOnly) != android::NO_ERROR) {
-            Logger::error(source) << "failed to open: " << strerror(errno) << std::endl;
-            return false;
-        }
-
-        std::shared_ptr<ResourceTable> table = std::make_shared<ResourceTable>();
-
-        ZipEntry* entry = zipFile->getEntryByName("resources.arsc");
-        if (!entry) {
-            Logger::error(source) << "missing 'resources.arsc'." << std::endl;
-            return false;
-        }
-
-        std::unique_ptr<void, DeleteMalloc> uncompressedData = std::unique_ptr<void, DeleteMalloc>(
-                zipFile->uncompress(entry));
-        assert(uncompressedData);
-
-        BinaryResourceParser parser(table, resolver, source, options.appInfo.package, 
-                                    uncompressedData.get(), entry->getUncompressedLen());
-        if (!parser.parse()) {
-            return false;
-        }
-
-        // Keep track of where this table came from.
-        apkFiles[table] = StaticLibraryData{ source, std::move(zipFile) };
-
-        // Add the package to the set of linked packages.
-        linkedPackages.insert(table->getPackage());
-    }
-
-    std::queue<LinkItem> linkQueue;
-    for (auto& p : apkFiles) {
-        const std::shared_ptr<ResourceTable>& inTable = p.first;
-
-        // Collect all FileReferences and add them to the queue for processing.
-        addApkFilesToLinkQueue(options.appInfo.package, p.second.source, inTable, p.second.apk,
-                               &linkQueue);
-
-        // Merge the tables.
-        if (!outTable->merge(std::move(*inTable))) {
-            return false;
-        }
-    }
-
-    // Version all styles referencing attributes outside of their specified SDK version.
-    if (options.versionStylesAndLayouts) {
-        versionStylesForCompat(outTable);
-    }
-
-    {
-        // Now that everything is merged, let's link it.
-        Linker::Options linkerOptions;
-        if (options.packageType == AaptOptions::PackageType::StaticLibrary) {
-            linkerOptions.linkResourceIds = false;
-        }
-        Linker linker(outTable, resolver, linkerOptions);
-        if (!linker.linkAndValidate()) {
-            return false;
-        }
-
-        // Verify that all symbols exist.
-        const auto& unresolvedRefs = linker.getUnresolvedReferences();
-        if (!unresolvedRefs.empty()) {
-            for (const auto& entry : unresolvedRefs) {
-                for (const auto& source : entry.second) {
-                    Logger::error(source) << "unresolved symbol '" << entry.first << "'."
-                                          << std::endl;
-                }
-            }
-            return false;
-        }
-    }
-
-    // Open the output APK file for writing.
-    ZipFile outApk;
-    if (outApk.open(options.output.path.data(), kOpenFlags) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to open: " << strerror(errno) << std::endl;
-        return false;
-    }
-
-    proguard::KeepSet keepSet;
-
-    android::ResTable binTable;
-    if (!compileManifest(options, resolver, apkFiles, binTable, &outApk, &keepSet)) {
-        return false;
-    }
-
-    for (; !linkQueue.empty(); linkQueue.pop()) {
-        const LinkItem& item = linkQueue.front();
-
-        assert(!item.originalPackage.empty());
-        ZipEntry* entry = item.apk->getEntryByName(item.originalPath.data());
-        if (!entry) {
-            Logger::error(item.source) << "failed to find '" << item.originalPath << "'."
-                                       << std::endl;
-            return false;
-        }
-
-        if (util::stringEndsWith<char>(item.originalPath, ".xml")) {
-            void* uncompressedData = item.apk->uncompress(entry);
-            assert(uncompressedData);
-
-            if (!linkXml(options, outTable, resolver, item, uncompressedData,
-                        entry->getUncompressedLen(), &outApk, &linkQueue, &keepSet)) {
-                Logger::error(options.output) << "failed to link '" << item.originalPath << "'."
-                                              << std::endl;
-                return false;
-            }
-        } else {
-            if (outApk.add(item.apk, entry, buildFileReference(item).data(), 0, nullptr) !=
-                    android::NO_ERROR) {
-                Logger::error(options.output) << "failed to copy '" << item.originalPath << "'."
-                                              << std::endl;
-                return false;
-            }
-        }
-    }
-
-    // Generate the Java class file.
-    if (options.generateJavaClass) {
-        JavaClassGenerator::Options javaOptions;
-        if (options.packageType == AaptOptions::PackageType::StaticLibrary) {
-            javaOptions.useFinal = false;
-        }
-        JavaClassGenerator generator(outTable, javaOptions);
-
-        for (const std::u16string& package : linkedPackages) {
-            Source outPath = options.generateJavaClass.value();
-
-            // Build the output directory from the package name.
-            // Eg. com.android.app -> com/android/app
-            const std::string packageUtf8 = util::utf16ToUtf8(package);
-            for (StringPiece part : util::tokenize<char>(packageUtf8, '.')) {
-                appendPath(&outPath.path, part);
-            }
-
-            if (!mkdirs(outPath.path)) {
-                Logger::error(outPath) << strerror(errno) << std::endl;
-                return false;
-            }
-
-            appendPath(&outPath.path, "R.java");
-
-            if (options.verbose) {
-                Logger::note(outPath) << "writing Java symbols." << std::endl;
-            }
-
-            std::ofstream fout(outPath.path);
-            if (!fout) {
-                Logger::error(outPath) << strerror(errno) << std::endl;
-                return false;
-            }
-
-            if (!generator.generate(package, fout)) {
-                Logger::error(outPath) << generator.getError() << "." << std::endl;
-                return false;
-            }
-        }
-    }
-
-    // Generate the Proguard rules file.
-    if (options.generateProguardRules) {
-        const Source& outPath = options.generateProguardRules.value();
-
-        if (options.verbose) {
-            Logger::note(outPath) << "writing proguard rules." << std::endl;
-        }
-
-        std::ofstream fout(outPath.path);
-        if (!fout) {
-            Logger::error(outPath) << strerror(errno) << std::endl;
-            return false;
-        }
-
-        if (!proguard::writeKeepSet(&fout, keepSet)) {
-            Logger::error(outPath) << "failed to write proguard rules." << std::endl;
-            return false;
-        }
-    }
-
-    outTable->getValueStringPool().prune();
-    outTable->getValueStringPool().sort(
-            [](const StringPool::Entry& a, const StringPool::Entry& b) -> bool {
-                if (a.context.priority < b.context.priority) {
-                    return true;
-                }
-
-                if (a.context.priority > b.context.priority) {
-                    return false;
-                }
-                return a.value < b.value;
-            });
-
-
-    // Flatten the resource table.
-    TableFlattener::Options flattenerOptions;
-    if (options.packageType != AaptOptions::PackageType::StaticLibrary) {
-        flattenerOptions.useExtendedChunks = false;
-    }
-
-    if (!writeResourceTable(options, outTable, flattenerOptions, &outApk)) {
-        return false;
-    }
-
-    outApk.flush();
-    return true;
-}
-
-bool compile(const AaptOptions& options, const std::shared_ptr<ResourceTable>& table,
-             const std::shared_ptr<IResolver>& resolver) {
-    std::queue<CompileItem> compileQueue;
-    bool error = false;
-
-    // Compile all the resource files passed in on the command line.
-    for (const Source& source : options.input) {
-        // Need to parse the resource type/config/filename.
-        Maybe<ResourcePathData> maybePathData = extractResourcePathData(source);
-        if (!maybePathData) {
-            return false;
-        }
-
-        const ResourcePathData& pathData = maybePathData.value();
-        if (pathData.resourceDir == u"values") {
-            // The file is in the values directory, which means its contents will
-            // go into the resource table.
-            if (options.verbose) {
-                Logger::note(source) << "compiling values." << std::endl;
-            }
-
-            error |= !compileValues(table, source, pathData.config);
-        } else {
-            // The file is in a directory like 'layout' or 'drawable'. Find out
-            // the type.
-            const ResourceType* type = parseResourceType(pathData.resourceDir);
-            if (!type) {
-                Logger::error(source) << "invalid resource type '" << pathData.resourceDir << "'."
-                                      << std::endl;
-                return false;
-            }
-
-            compileQueue.push(CompileItem{
-                    ResourceName{ table->getPackage(), *type, pathData.name },
-                    pathData.config,
-                    source,
-                    pathData.extension
-            });
-        }
-    }
-
-    if (error) {
-        return false;
-    }
-    // Open the output APK file for writing.
-    ZipFile outApk;
-    if (outApk.open(options.output.path.data(), kOpenFlags) != android::NO_ERROR) {
-        Logger::error(options.output) << "failed to open: " << strerror(errno) << std::endl;
-        return false;
-    }
-
-    // Compile each file.
-    for (; !compileQueue.empty(); compileQueue.pop()) {
-        const CompileItem& item = compileQueue.front();
-
-        // Add the file name to the resource table.
-        error |= !addFileReference(table, item);
-
-        if (item.extension == "xml") {
-            error |= !compileXml(options, table, item, &outApk);
-        } else if (item.extension == "png" || item.extension == "9.png") {
-            error |= !compilePng(options, item, &outApk);
-        } else {
-            error |= !copyFile(options, item, &outApk);
-        }
-    }
-
-    if (error) {
-        return false;
-    }
-
-    // Link and assign resource IDs.
-    Linker linker(table, resolver, {});
-    if (!linker.linkAndValidate()) {
-        return false;
-    }
-
-    // Flatten the resource table.
-    if (!writeResourceTable(options, table, {}, &outApk)) {
-        return false;
-    }
-
-    outApk.flush();
-    return true;
-}
-
-bool loadAppInfo(const Source& source, AppInfo* outInfo) {
-    std::ifstream ifs(source.path, std::ifstream::in | std::ifstream::binary);
-    if (!ifs) {
-        Logger::error(source) << strerror(errno) << std::endl;
-        return false;
-    }
-
-    ManifestParser parser;
-    std::shared_ptr<XmlPullParser> pullParser = std::make_shared<SourceXmlPullParser>(ifs);
-    return parser.parse(source, pullParser, outInfo);
-}
-
-static void printCommandsAndDie() {
-    std::cerr << "The following commands are supported:" << std::endl << std::endl;
-    std::cerr << "compile       compiles a subset of resources" << std::endl;
-    std::cerr << "link          links together compiled resources and libraries" << std::endl;
-    std::cerr << "dump          dumps resource contents to to standard out" << std::endl;
-    std::cerr << std::endl;
-    std::cerr << "run aapt2 with one of the commands and the -h flag for extra details."
-              << std::endl;
-    exit(1);
-}
-
-static AaptOptions prepareArgs(int argc, char** argv) {
-    if (argc < 2) {
-        std::cerr << "no command specified." << std::endl << std::endl;
-        printCommandsAndDie();
-    }
-
-    const StringPiece command(argv[1]);
-    argc -= 2;
-    argv += 2;
-
-    AaptOptions options;
-
-    if (command == "--version" || command == "version") {
-        std::cout << kAaptVersionStr << std::endl;
-        exit(0);
-    } else if (command == "link") {
-        options.phase = AaptOptions::Phase::Link;
-    } else if (command == "compile") {
-        options.phase = AaptOptions::Phase::Compile;
-    } else if (command == "dump") {
-        options.phase = AaptOptions::Phase::Dump;
-    } else if (command == "dump-style-graph") {
-        options.phase = AaptOptions::Phase::DumpStyleGraph;
-    } else {
-        std::cerr << "invalid command '" << command << "'." << std::endl << std::endl;
-        printCommandsAndDie();
-    }
-
-    bool isStaticLib = false;
-    if (options.phase == AaptOptions::Phase::Link) {
-        flag::requiredFlag("--manifest", "AndroidManifest.xml of your app",
-                [&options](const StringPiece& arg) {
-                    options.manifest = Source{ arg.toString() };
-                });
-
-        flag::optionalFlag("-I", "add an Android APK to link against",
-                [&options](const StringPiece& arg) {
-                    options.libraries.push_back(Source{ arg.toString() });
-                });
-
-        flag::optionalFlag("--java", "directory in which to generate R.java",
-                [&options](const StringPiece& arg) {
-                    options.generateJavaClass = Source{ arg.toString() };
-                });
-
-        flag::optionalFlag("--proguard", "file in which to output proguard rules",
-                [&options](const StringPiece& arg) {
-                    options.generateProguardRules = Source{ arg.toString() };
-                });
-
-        flag::optionalSwitch("--static-lib", "generate a static Android library", true,
-                             &isStaticLib);
-
-        flag::optionalFlag("--binding", "Output directory for binding XML files",
-                [&options](const StringPiece& arg) {
-                    options.bindingOutput = Source{ arg.toString() };
-                });
-        flag::optionalSwitch("--no-version", "Disables automatic style and layout versioning",
-                             false, &options.versionStylesAndLayouts);
-    }
-
-    if (options.phase == AaptOptions::Phase::Compile ||
-            options.phase == AaptOptions::Phase::Link) {
-        // Common flags for all steps.
-        flag::requiredFlag("-o", "Output path", [&options](const StringPiece& arg) {
-            options.output = Source{ arg.toString() };
-        });
-    }
-
-    if (options.phase == AaptOptions::Phase::DumpStyleGraph) {
-        flag::requiredFlag("--style", "Name of the style to dump",
-                [&options](const StringPiece& arg, std::string* outError) -> bool {
-                    Reference styleReference;
-                    if (!ResourceParser::parseStyleParentReference(util::utf8ToUtf16(arg),
-                                &styleReference, outError)) {
-                        return false;
-                    }
-                    options.dumpStyleTarget = styleReference.name;
-                    return true;
-                });
-    }
-
-    bool help = false;
-    flag::optionalSwitch("-v", "enables verbose logging", true, &options.verbose);
-    flag::optionalSwitch("-h", "displays this help menu", true, &help);
-
-    // Build the command string for output (eg. "aapt2 compile").
-    std::string fullCommand = "aapt2";
-    fullCommand += " ";
-    fullCommand += command.toString();
-
-    // Actually read the command line flags.
-    flag::parse(argc, argv, fullCommand);
-
-    if (help) {
-        flag::usageAndDie(fullCommand);
-    }
-
-    if (isStaticLib) {
-        options.packageType = AaptOptions::PackageType::StaticLibrary;
-    }
-
-    // Copy all the remaining arguments.
-    for (const std::string& arg : flag::getArgs()) {
-        options.input.push_back(Source{ arg });
-    }
-    return options;
-}
-
-static bool doDump(const AaptOptions& options) {
-    for (const Source& source : options.input) {
-        std::unique_ptr<ZipFile> zipFile = util::make_unique<ZipFile>();
-        if (zipFile->open(source.path.data(), ZipFile::kOpenReadOnly) != android::NO_ERROR) {
-            Logger::error(source) << "failed to open: " << strerror(errno) << std::endl;
-            return false;
-        }
-
-        std::shared_ptr<ResourceTable> table = std::make_shared<ResourceTable>();
-        std::shared_ptr<ResourceTableResolver> resolver =
-                std::make_shared<ResourceTableResolver>(
-                        table, std::vector<std::shared_ptr<const android::AssetManager>>());
-
-        ZipEntry* entry = zipFile->getEntryByName("resources.arsc");
-        if (!entry) {
-            Logger::error(source) << "missing 'resources.arsc'." << std::endl;
-            return false;
-        }
-
-        std::unique_ptr<void, DeleteMalloc> uncompressedData = std::unique_ptr<void, DeleteMalloc>(
-                zipFile->uncompress(entry));
-        assert(uncompressedData);
-
-        BinaryResourceParser parser(table, resolver, source, {}, uncompressedData.get(),
-                                    entry->getUncompressedLen());
-        if (!parser.parse()) {
-            return false;
-        }
-
-        if (options.phase == AaptOptions::Phase::Dump) {
-            Debug::printTable(table);
-        } else if (options.phase == AaptOptions::Phase::DumpStyleGraph) {
-            Debug::printStyleGraph(table, options.dumpStyleTarget);
-        }
-    }
-    return true;
-}
+} // namespace aapt
 
 int main(int argc, char** argv) {
-    Logger::setLog(std::make_shared<Log>(std::cerr, std::cerr));
-    AaptOptions options = prepareArgs(argc, argv);
+    if (argc >= 2) {
+        argv += 1;
+        argc -= 1;
 
-    if (options.phase == AaptOptions::Phase::Dump ||
-            options.phase == AaptOptions::Phase::DumpStyleGraph) {
-        if (!doDump(options)) {
-            return 1;
-        }
-        return 0;
-    }
-
-    // If we specified a manifest, go ahead and load the package name from the manifest.
-    if (!options.manifest.path.empty()) {
-        if (!loadAppInfo(options.manifest, &options.appInfo)) {
-            return false;
+        std::vector<aapt::StringPiece> args;
+        for (int i = 1; i < argc; i++) {
+            args.push_back(argv[i]);
         }
 
-        if (options.appInfo.package.empty()) {
-            Logger::error() << "no package name specified." << std::endl;
-            return false;
+        aapt::StringPiece command(argv[0]);
+        if (command == "compile" || command == "c") {
+            return aapt::compile(args);
+        } else if (command == "link" || command == "l") {
+            return aapt::link(args);
         }
-    }
-
-    // Every phase needs a resource table.
-    std::shared_ptr<ResourceTable> table = std::make_shared<ResourceTable>();
-
-    // The package name is empty when in the compile phase.
-    table->setPackage(options.appInfo.package);
-    if (options.appInfo.package == u"android") {
-        table->setPackageId(0x01);
+        std::cerr << "unknown command '" << command << "'\n";
     } else {
-        table->setPackageId(0x7f);
+        std::cerr << "no command specified\n";
     }
 
-    // Load the included libraries.
-    std::vector<std::shared_ptr<const android::AssetManager>> sources;
-    for (const Source& source : options.libraries) {
-        std::shared_ptr<android::AssetManager> assetManager =
-                std::make_shared<android::AssetManager>();
-        int32_t cookie;
-        if (!assetManager->addAssetPath(android::String8(source.path.data()), &cookie)) {
-            Logger::error(source) << "failed to load library." << std::endl;
-            return false;
-        }
-
-        if (cookie == 0) {
-            Logger::error(source) << "failed to load library." << std::endl;
-            return false;
-        }
-        sources.push_back(assetManager);
-    }
-
-    // Make the resolver that will cache IDs for us.
-    std::shared_ptr<ResourceTableResolver> resolver = std::make_shared<ResourceTableResolver>(
-            table, sources);
-
-    if (options.phase == AaptOptions::Phase::Compile) {
-        if (!compile(options, table, resolver)) {
-            Logger::error() << "aapt exiting with failures." << std::endl;
-            return 1;
-        }
-    } else if (options.phase == AaptOptions::Phase::Link) {
-        if (!link(options, table, resolver)) {
-            Logger::error() << "aapt exiting with failures." << std::endl;
-            return 1;
-        }
-    }
-    return 0;
+    std::cerr << "\nusage: aapt2 [compile|link] ..." << std::endl;
+    return 1;
 }