Process LocalizerOutput messages in 2022 drivetrain

Make it so that the roborio will actually pay attention to the pi's
localizer.

Change-Id: I8db97cbba65beef8c2ec863a792e57960ead996a
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/y2022/control_loops/drivetrain/localizer.h b/y2022/control_loops/drivetrain/localizer.h
new file mode 100644
index 0000000..50d083a
--- /dev/null
+++ b/y2022/control_loops/drivetrain/localizer.h
@@ -0,0 +1,80 @@
+#ifndef Y2022_CONTROL_LOOPS_DRIVETRAIN_LOCALIZER_H_
+#define Y2022_CONTROL_LOOPS_DRIVETRAIN_LOCALIZER_H_
+
+#include <string_view>
+
+#include "aos/events/event_loop.h"
+#include "frc971/control_loops/drivetrain/hybrid_ekf.h"
+#include "frc971/control_loops/drivetrain/localizer.h"
+#include "y2022/control_loops/localizer/localizer_output_generated.h"
+#include "aos/network/message_bridge_server_generated.h"
+
+namespace y2022 {
+namespace control_loops {
+namespace drivetrain {
+
+// This class handles the localization for the 2022 robot. Rather than actually
+// doing any work on the roborio, we farm all the localization out to a
+// raspberry pi and it then sends out LocalizerOutput messages that we treat as
+// measurement updates. See //y2022/control_loops/localizer.
+// TODO(james): Needs tests. Should refactor out some of the code from the 2020
+// localizer test.
+class Localizer : public frc971::control_loops::drivetrain::LocalizerInterface {
+ public:
+  typedef frc971::control_loops::TypedPose<float> Pose;
+  typedef frc971::control_loops::drivetrain::HybridEkf<float> HybridEkf;
+  typedef typename HybridEkf::State State;
+  typedef typename HybridEkf::StateIdx StateIdx;
+  typedef typename HybridEkf::StateSquare StateSquare;
+  typedef typename HybridEkf::Input Input;
+  typedef typename HybridEkf::Output Output;
+  Localizer(aos::EventLoop *event_loop,
+            const frc971::control_loops::drivetrain::DrivetrainConfig<double>
+                &dt_config);
+  frc971::control_loops::drivetrain::HybridEkf<double>::State Xhat()
+      const override {
+    return ekf_.X_hat().cast<double>();
+  }
+  frc971::control_loops::drivetrain::TrivialTargetSelector *target_selector()
+      override {
+    return &target_selector_;
+  }
+
+  void Update(const ::Eigen::Matrix<double, 2, 1> &U,
+              aos::monotonic_clock::time_point now, double left_encoder,
+              double right_encoder, double gyro_rate,
+              const Eigen::Vector3d &accel) override;
+
+  void Reset(aos::monotonic_clock::time_point t,
+             const frc971::control_loops::drivetrain::HybridEkf<double>::State
+                 &state) override;
+
+  void ResetPosition(aos::monotonic_clock::time_point t, double x, double y,
+                     double theta, double /*theta_override*/,
+                     bool /*reset_theta*/) override {
+    const double left_encoder = ekf_.X_hat(StateIdx::kLeftEncoder);
+    const double right_encoder = ekf_.X_hat(StateIdx::kRightEncoder);
+    ekf_.ResetInitialState(t,
+                           (HybridEkf::State() << x, y, theta, left_encoder, 0,
+                            right_encoder, 0, 0, 0, 0, 0, 0)
+                               .finished(),
+                           ekf_.P());
+  }
+
+ private:
+  aos::EventLoop *const event_loop_;
+  const frc971::control_loops::drivetrain::DrivetrainConfig<double> dt_config_;
+  HybridEkf ekf_;
+
+  aos::Fetcher<frc971::controls::LocalizerOutput> localizer_output_fetcher_;
+  aos::Fetcher<aos::message_bridge::ServerStatistics> clock_offset_fetcher_;
+
+  // Target selector to allow us to satisfy the LocalizerInterface requirements.
+  frc971::control_loops::drivetrain::TrivialTargetSelector target_selector_;
+};
+
+}  // namespace drivetrain
+}  // namespace control_loops
+}  // namespace y2022
+
+#endif  // Y2022_CONTROL_LOOPS_DRIVETRAIN_LOCALIZER_H_