// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/events/ozone/evdev/touch_filter/far_apart_taps_touch_noise_filter.h"

#include <stddef.h>

#include <cmath>

#include "base/logging.h"
#include "base/metrics/histogram_macros.h"
#include "base/stl_util.h"
#include "base/strings/stringprintf.h"

namespace ui {

namespace {

// Minimum squared distance between taps to be considered far apart.
const int kMinDistance2 = 1500 * 1500;

// The minimum squared distance between taps to log to UMA.
const int kUmaMinDistance2 = 1000 * 1000;

// The maximum squared distance between taps to log to UMA.
const int kUmaMaxDistance2 = 3000 * 3000;

// Max time between taps considered.
const int kMaxTapDeltaMs = 30;

// Maximum squared movement of a touch to still be considered a tap.
const int kMaxTapMovement2 = 20 * 20;

// Returns the squared distance between (|x1|, |y1|) and (|x2|, |y2|).
int Distance2(int x1, int y1, int x2, int y2) {
  int offset_x = x2 - x1;
  int offset_y = y2 - y1;
  return offset_x * offset_x + offset_y * offset_y;
}

}  // namespace

void FarApartTapsTouchNoiseFilter::Filter(
    const std::vector<InProgressTouchEvdev>& touches,
    base::TimeTicks time,
    std::bitset<kNumTouchEvdevSlots>* slots_with_noise) {
  // Remove old taps.
  base::TimeTicks tap_cutoff =
      time - base::TimeDelta::FromMilliseconds(kMaxTapDeltaMs);
  for (size_t i = 0; i < base::size(tracked_taps_); ++i) {
    if (tracked_taps_[i].start < tap_cutoff)
      tracked_taps_[i].Invalidate();
  }

  for (const InProgressTouchEvdev& touch : touches) {
    // Only look at slots with active touches.
    if (!touch.touching && !touch.was_touching)
      continue;

    size_t slot = touch.slot;
    if (!touch.was_touching) {
      // Track new finger info.
      tracked_taps_[slot] = Tap(time, touch.x, touch.y);
    } else if (tracked_taps_[slot].is_valid()) {
      // Check if this finger has moved too far to be considered a tap.
      if (kMaxTapMovement2 < Distance2(touch.x, touch.y, tracked_taps_[slot].x,
                                       tracked_taps_[slot].y)) {
        tracked_taps_[slot].Invalidate();
      }
    }

    if (tracked_taps_[slot].is_valid()) {
      // Check distance from other tracked taps.
      int min_distance2 = -1;
      for (size_t i = 0; i < base::size(tracked_taps_); ++i) {
        if (i == slot || !tracked_taps_[i].is_valid())
          continue;

        int dist2 =
            Distance2(tracked_taps_[i].x, tracked_taps_[i].y, touch.x, touch.y);
        if (min_distance2 < 0 || dist2 < min_distance2)
          min_distance2 = dist2;
      }

      // Log |min_distance2| to a UMA histogram to allow tuning of
      // |kMinDistance2|.
      if (min_distance2 > kUmaMinDistance2) {
        UMA_HISTOGRAM_CUSTOM_COUNTS(
            "Ozone.TouchNoiseFilter.FarApartTapDistance", min_distance2,
            kUmaMinDistance2, kUmaMaxDistance2, 50);
      }

      if (min_distance2 > kMinDistance2) {
        // The other finger should see this one on its next frame and also
        // get canceled.
        VLOG(2) << base::StringPrintf(
            "Cancel tracking id %d %.0fpx from other current taps.",
            touch.tracking_id, sqrt(min_distance2));
        slots_with_noise->set(slot);
      }
    }

    if (!touch.touching)
      tracked_taps_[slot].Invalidate();
  }
}

}  // namespace ui