Split //frc971/zeroing into multiple files

It's still a single target, and one massive header file. We should
actually split that up in a future refactoring. However, this does make
it easier to find the relevant parts within each file.

Change-Id: I7abc26f2e3d88da4558f54d56e6db4233cc4c30f
diff --git a/frc971/zeroing/pot_and_index.h b/frc971/zeroing/pot_and_index.h
new file mode 100644
index 0000000..473c674
--- /dev/null
+++ b/frc971/zeroing/pot_and_index.h
@@ -0,0 +1,103 @@
+#ifndef FRC971_ZEROING_POT_AND_INDEX_H_
+#define FRC971_ZEROING_POT_AND_INDEX_H_
+
+#include <vector>
+
+#include "flatbuffers/flatbuffers.h"
+
+#include "frc971/zeroing/zeroing.h"
+
+namespace frc971 {
+namespace zeroing {
+
+// Estimates the position with an incremental encoder with an index pulse and a
+// potentiometer.
+class PotAndIndexPulseZeroingEstimator
+    : public ZeroingEstimator<PotAndIndexPosition,
+                              constants::PotAndIndexPulseZeroingConstants,
+                              EstimatorState> {
+ public:
+  explicit PotAndIndexPulseZeroingEstimator(
+      const constants::PotAndIndexPulseZeroingConstants &constants);
+
+  // Update the internal logic with the next sensor values.
+  void UpdateEstimate(const PotAndIndexPosition &info) override;
+
+  // Reset the internal logic so it needs to be re-zeroed.
+  void Reset() override;
+
+  // Manually trigger an internal error. This is used for testing the error
+  // logic.
+  void TriggerError() override;
+
+  bool error() const override { return error_; }
+
+  bool zeroed() const override { return zeroed_; }
+
+  double offset() const override { return offset_; }
+
+  // Returns a number between 0 and 1 that represents the percentage of the
+  // samples being used in the moving average filter. A value of 0.0 means that
+  // no samples are being used. A value of 1.0 means that the filter is using
+  // as many samples as it has room for. For example, after a Reset() this
+  // value returns 0.0. As more samples get added with UpdateEstimate(...) the
+  // return value starts increasing to 1.0.
+  double offset_ratio_ready() const {
+    return start_pos_samples_.size() /
+           static_cast<double>(constants_.average_filter_size);
+  }
+
+  // Returns true if the sample buffer is full.
+  bool offset_ready() const override {
+    return start_pos_samples_.size() == constants_.average_filter_size;
+  }
+
+  // Returns information about our current state.
+  virtual flatbuffers::Offset<State> GetEstimatorState(
+      flatbuffers::FlatBufferBuilder *fbb) const override;
+
+ private:
+  // This function calculates the start position given the internal state and
+  // the provided `latched_encoder' value.
+  double CalculateStartPosition(double start_average,
+                                double latched_encoder) const;
+
+  // The zeroing constants used to describe the configuration of the system.
+  const constants::PotAndIndexPulseZeroingConstants constants_;
+
+  // The estimated position.
+  double position_;
+  // The unzeroed filtered position.
+  double filtered_position_ = 0.0;
+  // The next position in 'start_pos_samples_' to be used to store the next
+  // sample.
+  int samples_idx_;
+  // Last 'max_sample_count_' samples for start positions.
+  std::vector<double> start_pos_samples_;
+  // The estimated starting position of the mechanism. We also call this the
+  // 'offset' in some contexts.
+  double offset_;
+  // Flag for triggering logic that takes note of the current index pulse count
+  // after a reset. See `last_used_index_pulse_count_'.
+  bool wait_for_index_pulse_;
+  // After a reset we keep track of the index pulse count with this. Only after
+  // the index pulse count changes (i.e. increments at least once or wraps
+  // around) will we consider the mechanism zeroed. We also use this to store
+  // the most recent `PotAndIndexPosition::index_pulses' value when the start
+  // position was calculated. It helps us calculate the start position only on
+  // index pulses to reject corrupted intermediate data.
+  uint32_t last_used_index_pulse_count_;
+  // Marker to track whether we're fully zeroed yet or not.
+  bool zeroed_;
+  // Marker to track whether an error has occurred. This gets reset to false
+  // whenever Reset() is called.
+  bool error_;
+  // Stores the position "start_pos" variable the first time the program
+  // is zeroed.
+  double first_start_pos_;
+};
+
+}  // namespace zeroing
+}  // namespace frc971
+
+#endif  // FRC971_ZEROING_POT_AND_INDEX_H_