Merge pull request #7844 from spycrab/updatecommon_electric_boogaloo

UpdaterCommon: Move most of the programs here

10 files changed, 337 insertions, 458 deletions

diff --git a/Source/Core/MacUpdater/AppDelegate.mm b/Source/Core/MacUpdater/AppDelegate.mm
index e8bfc5c016..d260a2122a 100644
--- a/Source/Core/MacUpdater/AppDelegate.mm
+++ b/Source/Core/MacUpdater/AppDelegate.mm
@@ -4,100 +4,12 @@
 
 #import "AppDelegate.h"
 
-#include "Common/FileUtil.h"
-
-#include "UpdaterCommon/UI.h"
 #include "UpdaterCommon/UpdaterCommon.h"
 
 #include <Cocoa/Cocoa.h>
-#include <OptionParser.h>
-#include <optional>
-#include <unistd.h>
+#include <string>
 #include <vector>
 
-namespace
-{
-struct Options
-{
-  std::string this_manifest_url;
-  std::string next_manifest_url;
-  std::string content_store_url;
-  std::string install_base_path;
-  std::optional<std::string> binary_to_restart;
-  std::optional<pid_t> parent_pid;
-  std::optional<std::string> log_file;
-};
-
-std::optional<Options> ParseCommandLine(std::vector<std::string>& args)
-{
-  using optparse::OptionParser;
-
-  OptionParser parser =
-      OptionParser().prog("Dolphin Updater").description("Dolphin Updater binary");
-
-  parser.add_option("--this-manifest-url")
-      .dest("this-manifest-url")
-      .help("URL to the update manifest for the currently installed version.")
-      .metavar("URL");
-  parser.add_option("--next-manifest-url")
-      .dest("next-manifest-url")
-      .help("URL to the update manifest for the to-be-installed version.")
-      .metavar("URL");
-  parser.add_option("--content-store-url")
-      .dest("content-store-url")
-      .help("Base URL of the content store where files to download are stored.")
-      .metavar("URL");
-  parser.add_option("--install-base-path")
-      .dest("install-base-path")
-      .help("Base path of the Dolphin install to be updated.")
-      .metavar("PATH");
-  parser.add_option("--binary-to-restart")
-      .dest("binary-to-restart")
-      .help("Binary to restart after the update is over.")
-      .metavar("PATH");
-  parser.add_option("--log-file")
-      .dest("log-file")
-      .help("File where to log updater debug output.")
-      .metavar("PATH");
-  parser.add_option("--parent-pid")
-      .dest("parent-pid")
-      .type("int")
-      .help("(optional) PID of the parent process. The updater will wait for this process to "
-            "complete before proceeding.")
-      .metavar("PID");
-
-  optparse::Values options = parser.parse_args(args);
-
-  Options opts;
-
-  // Required arguments.
-  std::vector<std::string> required{"this-manifest-url", "next-manifest-url", "content-store-url",
-                                    "install-base-path"};
-  for (const auto& req : required)
-  {
-    if (!options.is_set(req))
-    {
-      parser.print_help();
-      return {};
-    }
-  }
-  opts.this_manifest_url = options["this-manifest-url"];
-  opts.next_manifest_url = options["next-manifest-url"];
-  opts.content_store_url = options["content-store-url"];
-  opts.install_base_path = options["install-base-path"];
-
-  // Optional arguments.
-  if (options.is_set("binary-to-restart"))
-    opts.binary_to_restart = options["binary-to-restart"];
-  if (options.is_set("parent-pid"))
-    opts.parent_pid = (pid_t)options.get("parent-pid");
-  if (options.is_set("log-file"))
-    opts.log_file = options["log-file"];
-
-  return opts;
-}
-}  // namespace
-
 @interface AppDelegate ()
 
 @end
@@ -106,8 +18,6 @@ std::optional<Options> ParseCommandLine(std::vector<std::string>& args)
 
 - (void)applicationDidFinishLaunching:(NSNotification*)aNotification
 {
-  UI::SetVisible(false);
-
   NSArray* arguments = [[NSProcessInfo processInfo] arguments];
 
   __block std::vector<std::string> args;
@@ -116,118 +26,10 @@ std::optional<Options> ParseCommandLine(std::vector<std::string>& args)
         args.push_back(std::string([obj UTF8String]));
       }];
 
-  std::optional<Options> maybe_opts = ParseCommandLine(args);
-
-  if (!maybe_opts)
-  {
-    [NSApp terminate:nil];
-    return;
-  }
-
-  Options opts = std::move(*maybe_opts);
-
   dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);
   dispatch_async(queue, ^{
-    if (opts.log_file)
-    {
-      log_fp = fopen(opts.log_file.value().c_str(), "w");
-      if (!log_fp)
-        log_fp = stderr;
-      else
-        atexit(FlushLog);
-    }
-
-    fprintf(log_fp, "Updating from: %s\n", opts.this_manifest_url.c_str());
-    fprintf(log_fp, "Updating to:   %s\n", opts.next_manifest_url.c_str());
-    fprintf(log_fp, "Install path:  %s\n", opts.install_base_path.c_str());
-
-    if (!File::IsDirectory(opts.install_base_path))
-    {
-      FatalError("Cannot find install base path, or not a directory.");
-
-      [NSApp performSelector:@selector(terminate:) withObject:nil afterDelay:0.0];
-      return;
-    }
-
-    if (opts.parent_pid)
-    {
-      UI::SetDescription("Waiting for Dolphin to quit...");
-
-      fprintf(log_fp, "Waiting for parent PID %d to complete...\n", *opts.parent_pid);
-
-      auto pid = opts.parent_pid.value();
-
-      for (int res = kill(pid, 0); res == 0 || (res < 0 && errno == EPERM); res = kill(pid, 0))
-      {
-        sleep(1);
-      }
-
-      fprintf(log_fp, "Completed! Proceeding with update.\n");
-    }
-
-    UI::SetVisible(true);
-
-    UI::SetDescription("Fetching and parsing manifests...");
-
-    Manifest this_manifest, next_manifest;
-    {
-      std::optional<Manifest> maybe_manifest = FetchAndParseManifest(opts.this_manifest_url);
-      if (!maybe_manifest)
-      {
-        FatalError("Could not fetch current manifest. Aborting.");
-        return;
-      }
-      this_manifest = std::move(*maybe_manifest);
-
-      maybe_manifest = FetchAndParseManifest(opts.next_manifest_url);
-      if (!maybe_manifest)
-      {
-        FatalError("Could not fetch next manifest. Aborting.");
-        [NSApp performSelector:@selector(terminate:) withObject:nil afterDelay:0.0];
-        return;
-      }
-      next_manifest = std::move(*maybe_manifest);
-    }
-
-    UI::SetDescription("Computing what to do...");
-
-    TodoList todo = ComputeActionsToDo(this_manifest, next_manifest);
-    todo.Log();
-
-    std::optional<std::string> maybe_temp_dir = FindOrCreateTempDir(opts.install_base_path);
-    if (!maybe_temp_dir)
-      return;
-    std::string temp_dir = std::move(*maybe_temp_dir);
-
-    UI::SetDescription("Performing Update...");
-
-    bool ok = PerformUpdate(todo, opts.install_base_path, opts.content_store_url, temp_dir);
-    if (!ok)
-      FatalError("Failed to apply the update.");
-
-    CleanUpTempDir(temp_dir, todo);
-
-    UI::ResetCurrentProgress();
-    UI::ResetTotalProgress();
-    UI::SetCurrentMarquee(false);
-    UI::SetTotalMarquee(false);
-    UI::SetCurrentProgress(1, 1);
-    UI::SetTotalProgress(1, 1);
-    UI::SetDescription("Done!");
-
-    // Let the user process that we are done.
-    [NSThread sleepForTimeInterval:1.0f];
-
-    if (opts.binary_to_restart)
-    {
-      [[NSWorkspace sharedWorkspace]
-          launchApplication:[NSString stringWithCString:opts.binary_to_restart.value().c_str()
-                                               encoding:[NSString defaultCStringEncoding]]];
-    }
-
-    dispatch_sync(dispatch_get_main_queue(), ^{
-      [NSApp terminate:nil];
-    });
+    RunUpdater(args);
+    [NSApp performSelector:@selector(terminate:) withObject:nil afterDelay:0.0];
   });
 }
 
diff --git a/Source/Core/MacUpdater/MacUI.mm b/Source/Core/MacUpdater/MacUI.mm
index aab655749d..d36a6a111e 100644
--- a/Source/Core/MacUpdater/MacUI.mm
+++ b/Source/Core/MacUpdater/MacUI.mm
@@ -7,6 +7,7 @@
 #include "UpdaterCommon/UI.h"
 
 #include <Cocoa/Cocoa.h>
+#include <unistd.h>
 
 #include <functional>
 
@@ -107,6 +108,32 @@ void UI::SetTotalProgress(int current, int total)
   run_on_main([&] { [GetView() SetTotalProgress:(double)current total:(double)total]; });
 }
 
+void UI::Sleep(int seconds)
+{
+  [NSThread sleepForTimeInterval:static_cast<float>(seconds)];
+}
+
+void UI::WaitForPID(u32 pid)
+{
+  for (int res = kill(pid, 0); res == 0 || (res < 0 && errno == EPERM); res = kill(pid, 0))
+  {
+    UI::Sleep(1);
+  }
+}
+
+void UI::LaunchApplication(std::string path)
+{
+  [[NSWorkspace sharedWorkspace]
+      launchApplication:[NSString stringWithCString:path.c_str()
+                                           encoding:[NSString defaultCStringEncoding]]];
+}
+
+// Stubs. These are only needed on Windows
+
+void UI::Init()
+{
+}
+
 void UI::Stop()
 {
 }
diff --git a/Source/Core/Updater/Main.cpp b/Source/Core/Updater/Main.cpp
index 35e868a7f1..0cb09cb966 100644
--- a/Source/Core/Updater/Main.cpp
+++ b/Source/Core/Updater/Main.cpp
@@ -4,36 +4,18 @@
 
 #include <windows.h>
 #include <ShlObj.h>
-
-#include <OptionParser.h>
-#include <array>
-#include <optional>
 #include <shellapi.h>
+
 #include <string>
-#include <thread>
 #include <vector>
 
-#include "Common/CommonPaths.h"
-#include "Common/CommonTypes.h"
-#include "Common/FileUtil.h"
+#include "Common/StringUtil.h"
 
 #include "UpdaterCommon/UI.h"
 #include "UpdaterCommon/UpdaterCommon.h"
 
 namespace
 {
-// Internal representation of options passed on the command-line.
-struct Options
-{
-  std::string this_manifest_url;
-  std::string next_manifest_url;
-  std::string content_store_url;
-  std::string install_base_path;
-  std::optional<std::string> binary_to_restart;
-  std::optional<DWORD> parent_pid;
-  std::optional<std::string> log_file;
-};
-
 std::vector<std::string> CommandLineToUtf8Argv(PCWSTR command_line)
 {
   int nargs;
@@ -50,75 +32,6 @@ std::vector<std::string> CommandLineToUtf8Argv(PCWSTR command_line)
   LocalFree(tokenized);
   return argv;
 }
-
-std::optional<Options> ParseCommandLine(PCWSTR command_line)
-{
-  using optparse::OptionParser;
-
-  OptionParser parser = OptionParser().prog("updater.exe").description("Dolphin Updater binary");
-
-  parser.add_option("--this-manifest-url")
-      .dest("this-manifest-url")
-      .help("URL to the update manifest for the currently installed version.")
-      .metavar("URL");
-  parser.add_option("--next-manifest-url")
-      .dest("next-manifest-url")
-      .help("URL to the update manifest for the to-be-installed version.")
-      .metavar("URL");
-  parser.add_option("--content-store-url")
-      .dest("content-store-url")
-      .help("Base URL of the content store where files to download are stored.")
-      .metavar("URL");
-  parser.add_option("--install-base-path")
-      .dest("install-base-path")
-      .help("Base path of the Dolphin install to be updated.")
-      .metavar("PATH");
-  parser.add_option("--binary-to-restart")
-      .dest("binary-to-restart")
-      .help("Binary to restart after the update is over.")
-      .metavar("PATH");
-  parser.add_option("--log-file")
-      .dest("log-file")
-      .help("File where to log updater debug output.")
-      .metavar("PATH");
-  parser.add_option("--parent-pid")
-      .dest("parent-pid")
-      .type("int")
-      .help("(optional) PID of the parent process. The updater will wait for this process to "
-            "complete before proceeding.")
-      .metavar("PID");
-
-  std::vector<std::string> argv = CommandLineToUtf8Argv(command_line);
-  optparse::Values options = parser.parse_args(argv);
-
-  Options opts;
-
-  // Required arguments.
-  std::vector<std::string> required{"this-manifest-url", "next-manifest-url", "content-store-url",
-                                    "install-base-path"};
-  for (const auto& req : required)
-  {
-    if (!options.is_set(req))
-    {
-      parser.print_help();
-      return {};
-    }
-  }
-  opts.this_manifest_url = options["this-manifest-url"];
-  opts.next_manifest_url = options["next-manifest-url"];
-  opts.content_store_url = options["content-store-url"];
-  opts.install_base_path = options["install-base-path"];
-
-  // Optional arguments.
-  if (options.is_set("binary-to-restart"))
-    opts.binary_to_restart = options["binary-to-restart"];
-  if (options.is_set("parent-pid"))
-    opts.parent_pid = (DWORD)options.get("parent-pid");
-  if (options.is_set("log-file"))
-    opts.log_file = options["log-file"];
-
-  return opts;
-}
 };  // namespace
 
 int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow)
@@ -132,58 +45,29 @@ int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine
     return 1;
   }
 
-  std::optional<Options> maybe_opts = ParseCommandLine(pCmdLine);
-  if (!maybe_opts)
-    return 1;
-  Options opts = std::move(*maybe_opts);
-
+  // Test for write permissions
   bool need_admin = false;
 
-  if (opts.log_file)
-  {
-    log_fp = _wfopen(UTF8ToUTF16(*opts.log_file).c_str(), L"w");
-    if (!log_fp)
-    {
-      log_fp = stderr;
-      // Failing to create the logfile for writing is a good indicator that we need administrator
-      // priviliges
-      need_admin = true;
-    }
-    else
-      atexit(FlushLog);
-  }
-
-  fprintf(log_fp, "Updating from: %s\n", opts.this_manifest_url.c_str());
-  fprintf(log_fp, "Updating to:   %s\n", opts.next_manifest_url.c_str());
-  fprintf(log_fp, "Install path:  %s\n", opts.install_base_path.c_str());
+  FILE* test_fh = fopen("Updater.log", "w");
 
-  if (!File::IsDirectory(opts.install_base_path))
-  {
-    FatalError("Cannot find install base path, or not a directory.");
-    return 1;
-  }
-
-  if (opts.parent_pid)
-  {
-    fprintf(log_fp, "Waiting for parent PID %d to complete...\n", *opts.parent_pid);
-    HANDLE parent_handle = OpenProcess(SYNCHRONIZE, FALSE, *opts.parent_pid);
-    WaitForSingleObject(parent_handle, INFINITE);
-    CloseHandle(parent_handle);
-    fprintf(log_fp, "Completed! Proceeding with update.\n");
-  }
+  if (test_fh == nullptr)
+    need_admin = true;
+  else
+    fclose(test_fh);
 
   if (need_admin)
   {
     if (IsUserAnAdmin())
     {
-      FatalError("Failed to write to directory despite administrator priviliges.");
+      MessageBox(nullptr, L"Failed to write to directory despite administrator priviliges.",
+                 L"Error", MB_ICONERROR);
       return 1;
     }
 
     wchar_t path[MAX_PATH];
     if (GetModuleFileName(hInstance, path, sizeof(path)) == 0)
     {
-      FatalError("Failed to get updater filename.");
+      MessageBox(nullptr, L"Failed to get updater filename.", L"Error", MB_ICONERROR);
       return 1;
     }
 
@@ -192,68 +76,7 @@ int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine
     return 0;
   }
 
-  std::thread thread(UI::MessageLoop);
-  thread.detach();
-
-  UI::SetDescription("Fetching and parsing manifests...");
-
-  Manifest this_manifest, next_manifest;
-  {
-    std::optional<Manifest> maybe_manifest = FetchAndParseManifest(opts.this_manifest_url);
-    if (!maybe_manifest)
-    {
-      FatalError("Could not fetch current manifest. Aborting.");
-      return 1;
-    }
-    this_manifest = std::move(*maybe_manifest);
-
-    maybe_manifest = FetchAndParseManifest(opts.next_manifest_url);
-    if (!maybe_manifest)
-    {
-      FatalError("Could not fetch next manifest. Aborting.");
-      return 1;
-    }
-    next_manifest = std::move(*maybe_manifest);
-  }
-
-  UI::SetDescription("Computing what to do...");
-
-  TodoList todo = ComputeActionsToDo(this_manifest, next_manifest);
-  todo.Log();
-
-  std::optional<std::string> maybe_temp_dir = FindOrCreateTempDir(opts.install_base_path);
-  if (!maybe_temp_dir)
-    return 1;
-  std::string temp_dir = std::move(*maybe_temp_dir);
-
-  UI::SetDescription("Performing Update...");
-
-  bool ok = PerformUpdate(todo, opts.install_base_path, opts.content_store_url, temp_dir);
-  if (!ok)
-    FatalError("Failed to apply the update.");
-
-  CleanUpTempDir(temp_dir, todo);
-
-  UI::ResetCurrentProgress();
-  UI::ResetTotalProgress();
-  UI::SetCurrentMarquee(false);
-  UI::SetTotalMarquee(false);
-  UI::SetCurrentProgress(0, 1);
-  UI::SetTotalProgress(1, 1);
-  UI::SetDescription("Done!");
-
-  // Let the user process that we are done.
-  Sleep(1000);
-
-  if (opts.binary_to_restart)
-  {
-    // Hack: Launching the updater over the explorer ensures that admin priviliges are dropped. Why?
-    // Ask Microsoft.
-    ShellExecuteW(nullptr, nullptr, L"explorer.exe", UTF8ToUTF16(*opts.binary_to_restart).c_str(),
-                  nullptr, SW_SHOW);
-  }
-
-  UI::Stop();
+  std::vector<std::string> args = CommandLineToUtf8Argv(pCmdLine);
 
-  return !ok;
+  return RunUpdater(args) ? 0 : 1;
 }
diff --git a/Source/Core/Updater/Updater.vcxproj b/Source/Core/Updater/Updater.vcxproj
index cb6085f967..93e1c7ea72 100644
--- a/Source/Core/Updater/Updater.vcxproj
+++ b/Source/Core/Updater/Updater.vcxproj
@@ -42,9 +42,6 @@
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\..\Externals\cpp-optparse\cpp-optparse.vcxproj">
-      <Project>{c636d9d1-82fe-42b5-9987-63b7d4836341}</Project>
-    </ProjectReference>
     <ProjectReference Include="..\Common\Common.vcxproj">
       <Project>{2e6c348c-c75c-4d94-8d1e-9c1fcbf3efe4}</Project>
     </ProjectReference>
diff --git a/Source/Core/Updater/WinUI.cpp b/Source/Core/Updater/WinUI.cpp
index b66a8fc92c..7f9a951bef 100644
--- a/Source/Core/Updater/WinUI.cpp
+++ b/Source/Core/Updater/WinUI.cpp
@@ -5,10 +5,12 @@
 #include "UpdaterCommon/UI.h"
 
 #include <string>
+#include <thread>
 
 #include <Windows.h>
 #include <CommCtrl.h>
 #include <ShObjIdl.h>
+#include <shellapi.h>
 
 #include "Common/Flag.h"
 #include "Common/StringUtil.h"
@@ -39,7 +41,7 @@ constexpr int PADDING_HEIGHT = 5;
 
 namespace UI
 {
-bool Init()
+bool InitWindow()
 {
   InitCommonControls();
 
@@ -200,7 +202,7 @@ void MessageLoop()
   request_stop.Clear();
   running.Set();
 
-  if (!Init())
+  if (!InitWindow())
   {
     running.Clear();
     MessageBox(nullptr, L"Window init failed!", L"", MB_ICONERROR);
@@ -224,6 +226,12 @@ void MessageLoop()
   Destroy();
 }
 
+void Init()
+{
+  std::thread thread(MessageLoop);
+  thread.detach();
+}
+
 void Stop()
 {
   if (!running.IsSet())
@@ -235,4 +243,29 @@ void Stop()
   {
   }
 }
+
+void LaunchApplication(std::string path)
+{
+  // Hack: Launching the updater over the explorer ensures that admin priviliges are dropped. Why?
+  // Ask Microsoft.
+  ShellExecuteW(nullptr, nullptr, L"explorer.exe", UTF8ToUTF16(path).c_str(), nullptr, SW_SHOW);
+}
+
+void Sleep(int sleep)
+{
+  ::Sleep(sleep * 1000);
+}
+
+void WaitForPID(u32 pid)
+{
+  HANDLE parent_handle = OpenProcess(SYNCHRONIZE, FALSE, static_cast<DWORD>(pid));
+  WaitForSingleObject(parent_handle, INFINITE);
+  CloseHandle(parent_handle);
+}
+
+void SetVisible(bool visible)
+{
+  ShowWindow(window_handle, visible ? SW_SHOW : SW_HIDE);
+}
+
 };  // namespace UI
diff --git a/Source/Core/UpdaterCommon/CMakeLists.txt b/Source/Core/UpdaterCommon/CMakeLists.txt
index c789681ef4..8a98814e4d 100644
--- a/Source/Core/UpdaterCommon/CMakeLists.txt
+++ b/Source/Core/UpdaterCommon/CMakeLists.txt
@@ -5,4 +5,5 @@ target_link_libraries(updatercommon PRIVATE
   uicommon
   mbedtls
   z
-  ed25519)
\ No newline at end of file
+  ed25519
+  cpp-optparse)
\ No newline at end of file
diff --git a/Source/Core/UpdaterCommon/UI.h b/Source/Core/UpdaterCommon/UI.h
index f542d02da0..0d4d606f37 100644
--- a/Source/Core/UpdaterCommon/UI.h
+++ b/Source/Core/UpdaterCommon/UI.h
@@ -6,11 +6,11 @@
 
 #include <string>
 
+#include "Common/CommonTypes.h"
+
 namespace UI
 {
-void MessageLoop();
 void Error(const std::string& text);
-void Stop();
 
 void SetDescription(const std::string& text);
 
@@ -23,4 +23,11 @@ void ResetCurrentProgress();
 void SetCurrentProgress(int current, int total);
 
 void SetVisible(bool visible);
+
+void Stop();
+
+void Init();
+void Sleep(int seconds);
+void WaitForPID(u32 pid);
+void LaunchApplication(std::string path);
 }  // namespace UI
diff --git a/Source/Core/UpdaterCommon/UpdaterCommon.cpp b/Source/Core/UpdaterCommon/UpdaterCommon.cpp
index 456576d5e7..77fb317040 100644
--- a/Source/Core/UpdaterCommon/UpdaterCommon.cpp
+++ b/Source/Core/UpdaterCommon/UpdaterCommon.cpp
@@ -5,6 +5,9 @@
 #include "UpdaterCommon/UpdaterCommon.h"
 
 #include <array>
+#include <optional>
+
+#include <OptionParser.h>
 #include <ed25519/ed25519.h>
 #include <mbedtls/base64.h>
 #include <mbedtls/sha256.h>
@@ -21,6 +24,8 @@
 #include <sys/types.h>
 #endif
 
+namespace
+{
 // Where to log updater output.
 FILE* log_fp = stderr;
 
@@ -31,13 +36,48 @@ const std::array<u8, 32> UPDATE_PUB_KEY = {
 
 const char UPDATE_TEMP_DIR[] = "TempUpdate";
 
-static bool ProgressCallback(double total, double now, double, double)
+struct Manifest
+{
+  using Filename = std::string;
+  using Hash = std::array<u8, 16>;
+  std::map<Filename, Hash> entries;
+};
+
+// Represent the operations to be performed by the updater.
+struct TodoList
+{
+  struct DownloadOp
+  {
+    Manifest::Filename filename;
+    Manifest::Hash hash;
+  };
+  std::vector<DownloadOp> to_download;
+
+  struct UpdateOp
+  {
+    Manifest::Filename filename;
+    std::optional<Manifest::Hash> old_hash;
+    Manifest::Hash new_hash;
+  };
+  std::vector<UpdateOp> to_update;
+
+  struct DeleteOp
+  {
+    Manifest::Filename filename;
+    Manifest::Hash old_hash;
+  };
+  std::vector<DeleteOp> to_delete;
+
+  void Log() const;
+};
+
+bool ProgressCallback(double total, double now, double, double)
 {
   UI::SetCurrentProgress(static_cast<int>(now), static_cast<int>(total));
   return true;
 }
 
-static std::string HexEncode(const u8* buffer, size_t size)
+std::string HexEncode(const u8* buffer, size_t size)
 {
   std::string out(size * 2, '\0');
 
@@ -50,7 +90,7 @@ static std::string HexEncode(const u8* buffer, size_t size)
   return out;
 }
 
-static bool HexDecode(const std::string& hex, u8* buffer, size_t size)
+bool HexDecode(const std::string& hex, u8* buffer, size_t size)
 {
   if (hex.size() != size * 2)
     return false;
@@ -79,7 +119,7 @@ static bool HexDecode(const std::string& hex, u8* buffer, size_t size)
   return true;
 }
 
-static std::optional<std::string> GzipInflate(const std::string& data)
+std::optional<std::string> GzipInflate(const std::string& data)
 {
   z_stream zstrm;
   zstrm.zalloc = nullptr;
@@ -115,7 +155,7 @@ static std::optional<std::string> GzipInflate(const std::string& data)
   return out;
 }
 
-static Manifest::Hash ComputeHash(const std::string& contents)
+Manifest::Hash ComputeHash(const std::string& contents)
 {
   std::array<u8, 32> full;
   mbedtls_sha256(reinterpret_cast<const u8*>(contents.data()), contents.size(), full.data(), false);
@@ -125,7 +165,7 @@ static Manifest::Hash ComputeHash(const std::string& contents)
   return out;
 }
 
-static bool VerifySignature(const std::string& data, const std::string& b64_signature)
+bool VerifySignature(const std::string& data, const std::string& b64_signature)
 {
   u8 signature[64];  // ed25519 sig size.
   size_t sig_size;
@@ -173,8 +213,8 @@ void TodoList::Log() const
   }
 }
 
-static bool DownloadContent(const std::vector<TodoList::DownloadOp>& to_download,
-                            const std::string& content_base_url, const std::string& temp_path)
+bool DownloadContent(const std::vector<TodoList::DownloadOp>& to_download,
+                     const std::string& content_base_url, const std::string& temp_path)
 {
   Common::HttpRequest req(std::chrono::seconds(30), ProgressCallback);
 
@@ -314,7 +354,7 @@ void CleanUpTempDir(const std::string& temp_dir, const TodoList& todo)
   File::DeleteDir(temp_dir);
 }
 
-static bool BackupFile(const std::string& path)
+bool BackupFile(const std::string& path)
 {
   std::string backup_path = path + ".bak";
   fprintf(log_fp, "Backing up unknown pre-existing %s to .bak.\n", path.c_str());
@@ -326,8 +366,8 @@ static bool BackupFile(const std::string& path)
   return true;
 }
 
-static bool DeleteObsoleteFiles(const std::vector<TodoList::DeleteOp>& to_delete,
-                                const std::string& install_base_path)
+bool DeleteObsoleteFiles(const std::vector<TodoList::DeleteOp>& to_delete,
+                         const std::string& install_base_path)
 {
   for (const auto& op : to_delete)
   {
@@ -359,8 +399,8 @@ static bool DeleteObsoleteFiles(const std::vector<TodoList::DeleteOp>& to_delete
   return true;
 }
 
-static bool UpdateFiles(const std::vector<TodoList::UpdateOp>& to_update,
-                        const std::string& install_base_path, const std::string& temp_path)
+bool UpdateFiles(const std::vector<TodoList::UpdateOp>& to_update,
+                 const std::string& install_base_path, const std::string& temp_path)
 {
   for (const auto& op : to_update)
   {
@@ -459,7 +499,7 @@ void FatalError(const std::string& message)
   UI::Stop();
 }
 
-static std::optional<Manifest> ParseManifest(const std::string& manifest)
+std::optional<Manifest> ParseManifest(const std::string& manifest)
 {
   Manifest parsed;
   size_t pos = 0;
@@ -550,3 +590,193 @@ std::optional<Manifest> FetchAndParseManifest(const std::string& url)
 
   return ParseManifest(decompressed);
 }
+
+struct Options
+{
+  std::string this_manifest_url;
+  std::string next_manifest_url;
+  std::string content_store_url;
+  std::string install_base_path;
+  std::optional<std::string> binary_to_restart;
+  std::optional<u32> parent_pid;
+  std::optional<std::string> log_file;
+};
+
+std::optional<Options> ParseCommandLine(std::vector<std::string>& args)
+{
+  using optparse::OptionParser;
+
+  OptionParser parser =
+      OptionParser().prog("Dolphin Updater").description("Dolphin Updater binary");
+
+  parser.add_option("--this-manifest-url")
+      .dest("this-manifest-url")
+      .help("URL to the update manifest for the currently installed version.")
+      .metavar("URL");
+  parser.add_option("--next-manifest-url")
+      .dest("next-manifest-url")
+      .help("URL to the update manifest for the to-be-installed version.")
+      .metavar("URL");
+  parser.add_option("--content-store-url")
+      .dest("content-store-url")
+      .help("Base URL of the content store where files to download are stored.")
+      .metavar("URL");
+  parser.add_option("--install-base-path")
+      .dest("install-base-path")
+      .help("Base path of the Dolphin install to be updated.")
+      .metavar("PATH");
+  parser.add_option("--binary-to-restart")
+      .dest("binary-to-restart")
+      .help("Binary to restart after the update is over.")
+      .metavar("PATH");
+  parser.add_option("--log-file")
+      .dest("log-file")
+      .help("File where to log updater debug output.")
+      .metavar("PATH");
+  parser.add_option("--parent-pid")
+      .dest("parent-pid")
+      .type("int")
+      .help("(optional) PID of the parent process. The updater will wait for this process to "
+            "complete before proceeding.")
+      .metavar("PID");
+
+  optparse::Values options = parser.parse_args(args);
+
+  Options opts;
+
+  // Required arguments.
+  std::vector<std::string> required{"this-manifest-url", "next-manifest-url", "content-store-url",
+                                    "install-base-path"};
+  for (const auto& req : required)
+  {
+    if (!options.is_set(req))
+    {
+      parser.print_help();
+      return {};
+    }
+  }
+  opts.this_manifest_url = options["this-manifest-url"];
+  opts.next_manifest_url = options["next-manifest-url"];
+  opts.content_store_url = options["content-store-url"];
+  opts.install_base_path = options["install-base-path"];
+
+  // Optional arguments.
+  if (options.is_set("binary-to-restart"))
+    opts.binary_to_restart = options["binary-to-restart"];
+  if (options.is_set("parent-pid"))
+    opts.parent_pid = static_cast<u32>(options.get("parent-pid"));
+  if (options.is_set("log-file"))
+    opts.log_file = options["log-file"];
+
+  return opts;
+}
+};  // namespace
+
+bool RunUpdater(std::vector<std::string> args)
+{
+  std::optional<Options> maybe_opts = ParseCommandLine(args);
+
+  if (!maybe_opts)
+  {
+    return false;
+  }
+
+  UI::Init();
+
+  Options opts = std::move(*maybe_opts);
+
+  if (opts.log_file)
+  {
+    log_fp = fopen(opts.log_file.value().c_str(), "w");
+    if (!log_fp)
+      log_fp = stderr;
+    else
+      atexit(FlushLog);
+  }
+
+  fprintf(log_fp, "Updating from: %s\n", opts.this_manifest_url.c_str());
+  fprintf(log_fp, "Updating to:   %s\n", opts.next_manifest_url.c_str());
+  fprintf(log_fp, "Install path:  %s\n", opts.install_base_path.c_str());
+
+  if (!File::IsDirectory(opts.install_base_path))
+  {
+    FatalError("Cannot find install base path, or not a directory.");
+    return false;
+  }
+
+  if (opts.parent_pid)
+  {
+    UI::SetDescription("Waiting for Dolphin to quit...");
+
+    fprintf(log_fp, "Waiting for parent PID %d to complete...\n", *opts.parent_pid);
+
+    auto pid = opts.parent_pid.value();
+
+    UI::WaitForPID(static_cast<u32>(pid));
+
+    fprintf(log_fp, "Completed! Proceeding with update.\n");
+  }
+
+  UI::SetVisible(true);
+
+  UI::SetDescription("Fetching and parsing manifests...");
+
+  Manifest this_manifest, next_manifest;
+  {
+    std::optional<Manifest> maybe_manifest = FetchAndParseManifest(opts.this_manifest_url);
+    if (!maybe_manifest)
+    {
+      FatalError("Could not fetch current manifest. Aborting.");
+      return false;
+    }
+    this_manifest = std::move(*maybe_manifest);
+
+    maybe_manifest = FetchAndParseManifest(opts.next_manifest_url);
+    if (!maybe_manifest)
+    {
+      FatalError("Could not fetch next manifest. Aborting.");
+      return false;
+    }
+    next_manifest = std::move(*maybe_manifest);
+  }
+
+  UI::SetDescription("Computing what to do...");
+
+  TodoList todo = ComputeActionsToDo(this_manifest, next_manifest);
+  todo.Log();
+
+  std::optional<std::string> maybe_temp_dir = FindOrCreateTempDir(opts.install_base_path);
+  if (!maybe_temp_dir)
+    return false;
+  std::string temp_dir = std::move(*maybe_temp_dir);
+
+  UI::SetDescription("Performing Update...");
+
+  bool ok = PerformUpdate(todo, opts.install_base_path, opts.content_store_url, temp_dir);
+  if (!ok)
+  {
+    FatalError("Failed to apply the update.");
+    CleanUpTempDir(temp_dir, todo);
+    return false;
+  }
+
+  UI::ResetCurrentProgress();
+  UI::ResetTotalProgress();
+  UI::SetCurrentMarquee(false);
+  UI::SetTotalMarquee(false);
+  UI::SetCurrentProgress(1, 1);
+  UI::SetTotalProgress(1, 1);
+  UI::SetDescription("Done!");
+
+  // Let the user process that we are done.
+  UI::Sleep(1);
+
+  if (opts.binary_to_restart)
+  {
+    UI::LaunchApplication(opts.binary_to_restart.value());
+  }
+
+  UI::Stop();
+
+  return true;
+}
diff --git a/Source/Core/UpdaterCommon/UpdaterCommon.h b/Source/Core/UpdaterCommon/UpdaterCommon.h
index fb63994d80..53f37c2424 100644
--- a/Source/Core/UpdaterCommon/UpdaterCommon.h
+++ b/Source/Core/UpdaterCommon/UpdaterCommon.h
@@ -13,48 +13,4 @@
 
 #include "Common/CommonTypes.h"
 
-extern FILE* log_fp;
-
-struct Manifest
-{
-  using Filename = std::string;
-  using Hash = std::array<u8, 16>;
-  std::map<Filename, Hash> entries;
-};
-
-// Represent the operations to be performed by the updater.
-struct TodoList
-{
-  struct DownloadOp
-  {
-    Manifest::Filename filename;
-    Manifest::Hash hash;
-  };
-  std::vector<DownloadOp> to_download;
-
-  struct UpdateOp
-  {
-    Manifest::Filename filename;
-    std::optional<Manifest::Hash> old_hash;
-    Manifest::Hash new_hash;
-  };
-  std::vector<UpdateOp> to_update;
-
-  struct DeleteOp
-  {
-    Manifest::Filename filename;
-    Manifest::Hash old_hash;
-  };
-  std::vector<DeleteOp> to_delete;
-
-  void Log() const;
-};
-
-void FatalError(const std::string& message);
-std::optional<Manifest> FetchAndParseManifest(const std::string& url);
-TodoList ComputeActionsToDo(Manifest this_manifest, Manifest next_manifest);
-std::optional<std::string> FindOrCreateTempDir(const std::string& base_path);
-void CleanUpTempDir(const std::string& temp_dir, const TodoList& todo);
-bool PerformUpdate(const TodoList& todo, const std::string& install_base_path,
-                   const std::string& content_base_url, const std::string& temp_path);
-void FlushLog();
+bool RunUpdater(std::vector<std::string> args);
diff --git a/Source/Core/UpdaterCommon/UpdaterCommon.vcxproj b/Source/Core/UpdaterCommon/UpdaterCommon.vcxproj
index 191098f15f..77fbaf069c 100644
--- a/Source/Core/UpdaterCommon/UpdaterCommon.vcxproj
+++ b/Source/Core/UpdaterCommon/UpdaterCommon.vcxproj
@@ -55,6 +55,9 @@
     <ProjectReference Include="..\..\..\Externals\zlib\zlib.vcxproj">
       <Project>{ff213b23-2c26-4214-9f88-85271e557e87}</Project>
     </ProjectReference>
+	<ProjectReference Include="..\..\..\Externals\cpp-optparse\cpp-optparse.vcxproj">
+      <Project>{c636d9d1-82fe-42b5-9987-63b7d4836341}</Project>
+    </ProjectReference>
   </ItemGroup>
   <ItemGroup>
 	<ClCompile Include="UpdaterCommon.cpp" />