Make BootImage movable and inherit from FlagBase and remove reference dependencies

This will help put it in a flags struct.

Bug: b/472361611

Author: Databean

base/cvd/cuttlefish/host/commands/assemble_cvd/disk_image_flags_vectorization.cc

@@ -99,7 +99,7 @@ Result<void> DiskImageFlagsVectorization(
   for (const auto& num : instance_nums) {
     auto instance = config.ForInstance(num);
     instance.set_images_dir(system_image_dir.ForIndex(instance_index));
-    std::string cur_boot_image = boot_image.BootImageForIndex(instance_index);
+    std::string cur_boot_image = boot_image.ForIndex(instance_index);
     instance.set_boot_image(cur_boot_image);
     instance.set_new_boot_image(cur_boot_image);
 

base/cvd/cuttlefish/host/commands/assemble_cvd/flags/BUILD.bazel

@@ -54,8 +54,10 @@ cf_cc_library(
     hdrs = ["boot_image.h"],
     deps = [
         "//cuttlefish/host/commands/assemble_cvd:flags_defaults",
+        "//cuttlefish/host/commands/assemble_cvd/flags:flag_base",
         "//cuttlefish/host/commands/assemble_cvd/flags:system_image_dir",
         "//libbase",
+        "@abseil-cpp//absl/strings",
         "@gflags",
     ],
 )

base/cvd/cuttlefish/host/commands/assemble_cvd/flags/boot_image.cc

@@ -20,8 +20,9 @@
 #include <string>
 #include <vector>
 
-#include <android-base/strings.h>
-#include <gflags/gflags.h>
+#include "absl/strings/str_cat.h"
+#include "absl/strings/str_split.h"
+#include "gflags/gflags.h"
 
 #include "cuttlefish/host/commands/assemble_cvd/flags/system_image_dir.h"
 #include "cuttlefish/host/commands/assemble_cvd/flags_defaults.h"
@@ -31,34 +32,33 @@ DEFINE_string(boot_image, CF_DEFAULTS_BOOT_IMAGE,
               "boot.img in the directory specified by -system_image_dir.");
 
 namespace cuttlefish {
+namespace {
+
+static constexpr std::string_view kName = "boot.img";
+
+std::vector<std::string> Defaults(const SystemImageDirFlag& system_image_dirs) {
+  std::vector<std::string> defaults;
+  for (std::string_view system_image_dir : system_image_dirs.AsVector()) {
+    defaults.emplace_back(absl::StrCat(system_image_dir, "/", kName));
+  }
+  return defaults;
+}
+
+}  // namespace
 
 BootImageFlag BootImageFlag::FromGlobalGflags(
     const SystemImageDirFlag& system_image_dir) {
   gflags::CommandLineFlagInfo flag_info =
       gflags::GetCommandLineFlagInfoOrDie("boot_image");
 
-  std::vector<std::string> boot_images =
-      flag_info.is_default ? std::vector<std::string>{}
-                           : android::base::Split(FLAGS_boot_image, ",");
-
-  return BootImageFlag(system_image_dir, boot_images);
-}
-
-std::string BootImageFlag::BootImageForIndex(size_t index) const {
-  if (boot_images_.empty()) {
-    return system_image_dir_.ForIndex(index) + "/boot.img";
-  } else if (index < boot_images_.size()) {
-    return boot_images_[index];
-  } else {
-    return boot_images_[0];
-  }
+  return flag_info.is_default
+             ? BootImageFlag(Defaults(system_image_dir), true)
+             : BootImageFlag(absl::StrSplit(FLAGS_boot_image, ","), false);
 }
 
-bool BootImageFlag::IsDefault() const { return boot_images_.empty(); }
+bool BootImageFlag::IsDefault() const { return is_default_; }
 
-BootImageFlag::BootImageFlag(const SystemImageDirFlag& system_image_dir,
-                             std::vector<std::string> boot_images)
-    : system_image_dir_(system_image_dir),
-      boot_images_(std::move(boot_images)) {}
+BootImageFlag::BootImageFlag(std::vector<std::string> paths, bool is_default)
+    : FlagBase(std::move(paths)), is_default_(is_default) {}
 
 }  // namespace cuttlefish

base/cvd/cuttlefish/host/commands/assemble_cvd/flags/boot_image.h

@@ -20,24 +20,22 @@
 #include <string>
 #include <vector>
 
+#include "cuttlefish/host/commands/assemble_cvd/flags/flag_base.h"
 #include "cuttlefish/host/commands/assemble_cvd/flags/system_image_dir.h"
 
 namespace cuttlefish {
 
 /* Android boot image path flag, --boot_image */
-class BootImageFlag {
+class BootImageFlag : public FlagBase<std::string> {
  public:
   static BootImageFlag FromGlobalGflags(const SystemImageDirFlag&);
 
-  std::string BootImageForIndex(size_t index) const;
-
   bool IsDefault() const;
 
  private:
-  BootImageFlag(const SystemImageDirFlag&, std::vector<std::string>);
+  BootImageFlag(std::vector<std::string>, bool is_default);
 
-  const SystemImageDirFlag& system_image_dir_;
-  std::vector<std::string> boot_images_;
+  bool is_default_;
 };
 
 }  // namespace cuttlefish

base/cvd/cuttlefish/host/commands/assemble_cvd/guest_config.cc

@@ -261,7 +261,7 @@ Result<std::vector<GuestConfig>> ReadGuestConfig(
     // for the ikconfig header in the image before extracting the config list.
     // This code is liable to break if the boot image ever includes the
     // ikconfig header outside the kernel.
-    std::string cur_boot_image = boot_image.BootImageForIndex(instance_index);
+    std::string cur_boot_image = boot_image.ForIndex(instance_index);
 
     if (!kernel_path.KernelPathForIndex(instance_index).empty()) {
       kernel_image_path = kernel_path.KernelPathForIndex(instance_index);