AAPT2: Refactor flags into commands

Refactors the flag based command invocation into classes that make using
subcommands easier.

Test: manual tests of printing
Change-Id: Ic8df6af0be30db552e32150afebecbfeec7e1075
diff --git a/tools/aapt2/cmd/Command.cpp b/tools/aapt2/cmd/Command.cpp
new file mode 100644
index 0000000..09411b9
--- /dev/null
+++ b/tools/aapt2/cmd/Command.cpp
@@ -0,0 +1,222 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+#include "Command.h"
+
+#include <iomanip>
+#include <iostream>
+#include <string>
+#include <vector>
+
+#include "androidfw/StringPiece.h"
+
+#include "util/Util.h"
+
+using android::StringPiece;
+
+namespace aapt {
+
+void Command::AddRequiredFlag(const StringPiece& name,
+    const StringPiece& description, std::string* value) {
+  auto func = [value](const StringPiece& arg) -> bool {
+    *value = arg.to_string();
+    return true;
+  };
+
+  flags_.push_back(Flag{name.to_string(), description.to_string(), func, true, 1, false});
+}
+
+void Command::AddRequiredFlagList(const StringPiece& name,
+    const StringPiece& description,
+    std::vector<std::string>* value) {
+  auto func = [value](const StringPiece& arg) -> bool {
+    value->push_back(arg.to_string());
+    return true;
+  };
+
+  flags_.push_back(Flag{name.to_string(), description.to_string(), func, true, 1, false});
+}
+
+void Command::AddOptionalFlag(const StringPiece& name,
+    const StringPiece& description,
+    Maybe<std::string>* value) {
+  auto func = [value](const StringPiece& arg) -> bool {
+    *value = arg.to_string();
+    return true;
+  };
+
+  flags_.push_back(Flag{name.to_string(), description.to_string(), func, false, 1, false});
+}
+
+void Command::AddOptionalFlagList(const StringPiece& name,
+    const StringPiece& description,
+    std::vector<std::string>* value) {
+  auto func = [value](const StringPiece& arg) -> bool {
+    value->push_back(arg.to_string());
+    return true;
+  };
+
+  flags_.push_back(Flag{name.to_string(), description.to_string(), func, false, 1, false});
+}
+
+void Command::AddOptionalFlagList(const StringPiece& name,
+    const StringPiece& description,
+    std::unordered_set<std::string>* value) {
+  auto func = [value](const StringPiece& arg) -> bool {
+    value->insert(arg.to_string());
+    return true;
+  };
+
+  flags_.push_back(Flag{name.to_string(), description.to_string(), func, false, 1, false});
+}
+
+void Command::AddOptionalSwitch(const StringPiece& name,
+    const StringPiece& description, bool* value) {
+  auto func = [value](const StringPiece& arg) -> bool {
+    *value = true;
+    return true;
+  };
+
+  flags_.push_back(Flag{name.to_string(), description.to_string(), func, false, 0, false});
+}
+
+void Command::AddOptionalSubcommand(std::unique_ptr<Command>&& subcommand) {
+  subcommand->fullname_ = name_ + " " + subcommand->name_;
+  subcommands_.push_back(std::move(subcommand));
+}
+
+void Command::SetDescription(const android::StringPiece& description) {
+  description_ = description.to_string();
+}
+
+void Command::Usage(std::ostream* out) {
+  constexpr size_t kWidth = 50;
+
+  *out << fullname_;
+
+  if (!subcommands_.empty()) {
+    *out << " [subcommand]";
+  }
+
+  *out << " [options]";
+  for (const Flag& flag : flags_) {
+    if (flag.required) {
+      *out << " " << flag.name << " arg";
+    }
+  }
+
+  *out << " files...\n";
+
+  if (!subcommands_.empty()) {
+    *out << "\nSubcommands:\n";
+    for (auto& subcommand : subcommands_) {
+      std::string argline = subcommand->name_;
+
+      // Split the description by newlines and write out the argument (which is
+      // empty after the first line) followed by the description line. This will make sure
+      // that multiline descriptions are still right justified and aligned.
+      for (StringPiece line : util::Tokenize(subcommand->description_, '\n')) {
+        *out << " " << std::setw(kWidth) << std::left << argline << line << "\n";
+        argline = " ";
+      }
+    }
+  }
+
+  *out << "\nOptions:\n";
+
+  for (const Flag& flag : flags_) {
+    std::string argline = flag.name;
+    if (flag.num_args > 0) {
+      argline += " arg";
+    }
+
+    // Split the description by newlines and write out the argument (which is
+    // empty after the first line) followed by the description line. This will make sure
+    // that multiline descriptions are still right justified and aligned.
+    for (StringPiece line : util::Tokenize(flag.description, '\n')) {
+      *out << " " << std::setw(kWidth) << std::left << argline << line << "\n";
+      argline = " ";
+    }
+  }
+  *out << " " << std::setw(kWidth) << std::left << "-h"
+       << "Displays this help menu\n";
+  out->flush();
+}
+
+int Command::Execute(const std::vector<android::StringPiece>& args, std::ostream* out_error) {
+  std::vector<std::string> file_args;
+
+  for (size_t i = 0; i < args.size(); i++) {
+    StringPiece arg = args[i];
+    if (*(arg.data()) != '-') {
+      // Continue parsing as the sub command if the first argument matches one of the subcommands
+      if (i == 0) {
+        for (auto& subcommand : subcommands_) {
+          if (arg == subcommand->name_ || arg==subcommand->short_name_) {
+            return subcommand->Execute(
+                std::vector<android::StringPiece>(args.begin() + 1, args.end()), out_error);
+          }
+        }
+      }
+
+      file_args.push_back(arg.to_string());
+      continue;
+    }
+
+    if (arg == "-h" || arg == "--help") {
+      Usage(out_error);
+      return 1;
+    }
+
+    bool match = false;
+    for (Flag& flag : flags_) {
+      if (arg == flag.name) {
+        if (flag.num_args > 0) {
+          i++;
+          if (i >= args.size()) {
+            *out_error << flag.name << " missing argument.\n\n";
+            Usage(out_error);
+            return false;
+          }
+          flag.action(args[i]);
+        } else {
+          flag.action({});
+        }
+        flag.parsed = true;
+        match = true;
+        break;
+      }
+    }
+
+    if (!match) {
+      *out_error << "unknown option '" << arg << "'.\n\n";
+      Usage(out_error);
+      return 1;
+    }
+  }
+
+  for (const Flag& flag : flags_) {
+    if (flag.required && !flag.parsed) {
+      *out_error << "missing required flag " << flag.name << "\n\n";
+      Usage(out_error);
+      return 1;
+    }
+  }
+
+  return Action(file_args);
+}
+
+}  // namespace aapt