/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.material.slider;

import com.google.android.material.R;

import static com.google.android.material.internal.ThemeEnforcement.createThemedContext;

import android.content.Context;
import android.content.res.ColorStateList;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffColorFilter;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Parcel;
import android.os.Parcelable;
import androidx.annotation.ColorInt;
import androidx.annotation.DimenRes;
import androidx.annotation.Dimension;
import androidx.annotation.IntRange;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.InflateException;
import android.view.MotionEvent;
import android.view.View;
import com.google.android.material.internal.ThemeEnforcement;
import com.google.android.material.resources.MaterialResources;
import java.util.Locale;

/**
 * A widget that allows picking a value within a given range by sliding a thumb along a horizontal
 * line.
 *
 * <p>The slider can function either as a continuous slider, or as a discrete slider. The mode of
 * operation is controlled by the value of the step size. If the step size is set to 0, the slider
 * operates as a continuous slider where the slider's thumb can be moved to any position along the
 * horizontal line. If the step size is set to a number greater than 0, the slider operates as a
 * discrete slider where the slider's thumb will snap to the closest tick mark. See {@link
 * #setStepSize(float)}.
 *
 * <p>In continuous mode the slider displays a line on which the thumb can be dragged to select a
 * value.
 *
 * <p>In discrete mode the slider displays a line on which the thumb can be dragged to select a
 * value. When clicked, discrete tick marks are displayed along the line, and the thumb
 * automatically snaps to the closest tick mark. When clicked or focused, a bubble displaying the
 * selected value is shown above the horizontal line.
 *
 * <p>The {@link OnChangeListener} interface defines a callback to be invoked when the slider
 * changes.
 *
 * <p>The {@link LabelFormatter} interface defines a formatter to be used to render text within the
 * bubble shown while in discrete mode.
 *
 * <p>{@link BasicLabelFormatter} is a simple implementation of the {@link LabelFormatter} that
 * displays the selected value using letters to indicate magnitude (e.g.: 1.5K, 3M, 12B, etc..).
 *
 * <p>With the default style {@link
 * com.google.android.material.R.style.Widget_MaterialComponents_Slider}, colorPrimary is used to
 * customize the color of the slider. The following attributes are used to customize the slider's
 * appearance further:
 *
 * <ul>
 *   <li>{@code trackColor}: The color of the whole track. This is a short hand for setting both the
 *       {@code activeTrackColor} and {@code inactiveTrackColor} to the same thing. This takes
 *       precedence over {@code activeTrackColor} and {@code inactiveTrackColor}.
 *   <li>{@code activeTrackColor}: The color of the active part of the track.
 *   <li>{@code inactiveTrackColor}: The color of the inactive part of the track.
 *   <li>{@code thumbColor}: the color of the slider's thumb.
 *   <li>{@code tickColor}: the color of the slider's tick marks. Only used when the slider is in
 *       discrete mode.
 *   <li>{@code activeTickColor}: the color of the slider's tick marks for the active part of the
 *       track. Only used when the slider is in discrete mode.
 *   <li>{@code inactiveTickColor}: the color of the slider's tick marks for the inactive part of
 *       the track. Only used when the slider is in discrete mode.
 *   <li>{@code labelColor}: the color of the text displayed in the slider's bubble. Only used when
 *       the slider is in discrete mode.
 * </ul>
 *
 * <p>The following XML attributes are used to set the slider's various parameters of operation:
 *
 * <ul>
 *   <li>{@code android:valueFrom}: <b>Required.</b> The slider's minimum value. This attribute is
 *       required, if missing, an {@link InflateException} is thrown.
 *   <li>{@code android:valueTo}: <b>Required.</b> The slider's maximum value. This attribute is
 *       required, if missing, an {@link InflateException} is thrown.
 *   <li>{@code android:value}: <b>Optional.</b> The initial value of the slider. If not specified,
 *       the slider's minimum value {@code android:valueFrom} is used.
 *   <li>{@code android:stepSize}: <b>Optional.</b> This value dictates whether the slider operates
 *       in continuous mode, or in discrete mode. If missing or equal to 0, the slider operates in
 *       continuous mode. If greater than 0 and evenly divides the range described by {@code
 *       valueFrom} and {@code valueTo}, the slider operates in discrete mode. If negative, or
 *       greater than 0 but not a factor of the range described by {@code valueFrom} and {@code
 *       valueTo}, an {@link IllegalArgumentException} is thrown.
 * </ul>
 *
 * <p>Note: the slider does not accept {@link View.OnFocusChangeListener}s.
 *
 * @attr ref com.google.android.material.R.styleable#Slider_android_value
 * @attr ref com.google.android.material.R.styleable#Slider_android_valueFrom
 * @attr ref com.google.android.material.R.styleable#Slider_android_valueTo
 * @attr ref com.google.android.material.R.styleable#Slider_android_stepSize
 * @attr ref com.google.android.material.R.styleable#Slider_trackColor
 * @attr ref com.google.android.material.R.styleable#Slider_activeTrackColor
 * @attr ref com.google.android.material.R.styleable#Slider_inactiveTrackColor
 * @attr ref com.google.android.material.R.styleable#Slider_thumbColor
 * @attr ref com.google.android.material.R.styleable#Slider_tickColor
 * @attr ref com.google.android.material.R.styleable#Slider_activeTickColor
 * @attr ref com.google.android.material.R.styleable#Slider_inactiveTickColor
 * @attr ref com.google.android.material.R.styleable#Slider_labelColor
 */
public class Slider extends View {

  private static final String TAG = Slider.class.getSimpleName();
  private static final String EXCEPTION_ILLEGAL_VALUE =
      "Slider value must be greater or equal to valueFrom, and lower or equal to valueTo";
  private static final String EXCEPTION_ILLEGAL_DISCRETE_VALUE =
      "Value must be equal to valueFrom plus a multiple of stepSize when using stepSize";
  private static final String EXCEPTION_ILLEGAL_VALUE_FROM =
      "valueFrom must be smaller than valueTo";
  private static final String EXCEPTION_ILLEGAL_VALUE_TO = "valueTo must be greater than valueFrom";
  private static final String EXCEPTION_ILLEGAL_STEP_SIZE =
      "The stepSize must be 0, or a factor of the valueFrom-valueTo range";

  private static final int HALO_ALPHA = 63;

  private static final int DEF_STYLE_RES = R.style.Widget_MaterialComponents_Slider;

  @NonNull private final Paint inactiveTrackPaint;
  @NonNull private final Paint activeTrackPaint;
  @NonNull private final Paint thumbPaint;
  @NonNull private final Paint haloPaint;
  @NonNull private final Paint ticksPaint;
  @NonNull private final Drawable label;
  @NonNull private final Paint labelTextPaint;
  @NonNull private final Rect labelTextBounds;

  @NonNull private String labelText = "";

  private int widgetHeight;
  private int widgetHeightDiscrete;
  private int lineHeight;
  private int trackSidePadding;
  private int trackTop;
  private int trackTopDiscrete;
  private int thumbPaddingDisabled;
  private int thumbRadius;
  private int haloRadius;
  private int labelWidth;
  private int labelHeight;
  private int labelTopOffset;
  private float labelTextSize;
  private int labelTextTopOffset;
  private OnChangeListener listener;
  private LabelFormatter formatter;
  private boolean thumbIsPressed = false;
  private float valueFrom;
  private float valueTo;
  private float thumbPosition = 0.0f; // The position of the thumb normalised to a [0.0, 1.0] range.
  private float stepSize = 0.0f;
  private float[] ticksCoordinates;
  private int trackWidth;

  @NonNull private ColorStateList inactiveTrackColor;
  @NonNull private ColorStateList activeTrackColor;
  @NonNull private ColorStateList thumbColor;
  @NonNull private ColorStateList tickColor;
  @NonNull private ColorStateList textColor;

  /** Interface definition for a callback invoked when a slider's value is changed. */
  public interface OnChangeListener {
    void onValueChange(Slider slider, float value);
  }

  /**
   * Interface definition for applying custom formatting to the text displayed inside the bubble
   * shown when a slider is used in discrete mode.
   */
  public interface LabelFormatter {
    @NonNull
    String getFormattedValue(float value);
  }

  /**
   * A simple implementation of the {@link LabelFormatter} interface, that limits the number
   * displayed inside a discrete slider's bubble to three digits, and a single-character suffix that
   * denotes magnitude (e.g.: 1.5K, 2.2M, 1.3B, 2T).
   */
  public static final class BasicLabelFormatter implements LabelFormatter {

    private static final long TRILLION = 1000000000000L;
    private static final int BILLION = 1000000000;
    private static final int MILLION = 1000000;
    private static final int THOUSAND = 1000;

    @NonNull
    @Override
    public String getFormattedValue(float value) {
      if (value >= TRILLION) {
        return String.format(Locale.US, "%.1fT", value / TRILLION);
      } else if (value >= BILLION) {
        return String.format(Locale.US, "%.1fB", value / BILLION);
      } else if (value >= MILLION) {
        return String.format(Locale.US, "%.1fM", value / MILLION);
      } else if (value >= THOUSAND) {
        return String.format(Locale.US, "%.1fK", value / THOUSAND);
      } else {
        return String.format(Locale.US, "%.0f", value);
      }
    }
  }

  public Slider(@NonNull Context context) {
    this(context, null);
  }

  public Slider(@NonNull Context context, @Nullable AttributeSet attrs) {
    this(context, attrs, R.attr.sliderStyle);
  }

  public Slider(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(createThemedContext(context, attrs, defStyleAttr, DEF_STYLE_RES), attrs, defStyleAttr);
    // Ensure we are using the correctly themed context rather than the context that was passed in.
    context = getContext();

    loadResources(context.getResources());
    processAttributes(context, attrs, defStyleAttr);

    inactiveTrackPaint = new Paint();
    inactiveTrackPaint.setStyle(Paint.Style.STROKE);
    inactiveTrackPaint.setStrokeWidth(lineHeight);

    activeTrackPaint = new Paint();
    activeTrackPaint.setStyle(Paint.Style.STROKE);
    activeTrackPaint.setStrokeWidth(lineHeight);

    thumbPaint = new Paint();

    haloPaint = new Paint();
    haloPaint.setStyle(Paint.Style.FILL);

    ticksPaint = new Paint();
    ticksPaint.setStyle(Paint.Style.STROKE);
    ticksPaint.setStrokeWidth(lineHeight);

    label = context.getResources().getDrawable(R.drawable.mtrl_slider_label);
    label.setColorFilter(
        new PorterDuffColorFilter(getColorForState(thumbColor), PorterDuff.Mode.MULTIPLY));

    labelTextPaint = new Paint();
    labelTextPaint.setTextSize(labelTextSize);

    labelTextBounds = new Rect();

    super.setOnFocusChangeListener(
        new OnFocusChangeListener() {
          @Override
          public void onFocusChange(View v, boolean hasFocus) {
            invalidate();
          }
        });

    setFocusable(true);
    setFocusableInTouchMode(true);
  }

  @Override
  public void setOnFocusChangeListener(View.OnFocusChangeListener listener) {}

  private void loadResources(@NonNull Resources resources) {
    widgetHeight = resources.getDimensionPixelSize(R.dimen.mtrl_slider_widget_height);
    widgetHeightDiscrete =
        resources.getDimensionPixelSize(R.dimen.mtrl_slider_widget_height_discrete);

    lineHeight = resources.getDimensionPixelSize(R.dimen.mtrl_slider_line_height);

    trackSidePadding = resources.getDimensionPixelOffset(R.dimen.mtrl_slider_track_side_padding);
    trackTop = resources.getDimensionPixelOffset(R.dimen.mtrl_slider_track_top);
    trackTopDiscrete = resources.getDimensionPixelOffset(R.dimen.mtrl_slider_track_top_discrete);

    thumbPaddingDisabled =
        resources.getDimensionPixelOffset(R.dimen.mtrl_slider_thumb_padding_disabled);

    labelWidth = resources.getDimensionPixelSize(R.dimen.mtrl_slider_label_width);
    labelHeight = resources.getDimensionPixelSize(R.dimen.mtrl_slider_label_height);
    labelTopOffset = resources.getDimensionPixelSize(R.dimen.mtrl_slider_label_top_offset);
    labelTextSize = resources.getDimension(R.dimen.mtrl_slider_label_text_size);
    labelTextTopOffset = resources.getDimensionPixelSize(R.dimen.mtrl_slider_label_text_top_offset);
  }

  private void processAttributes(Context context, AttributeSet attrs, int defStyleAttr) {
    TypedArray a =
        ThemeEnforcement.obtainStyledAttributes(
            context, attrs, R.styleable.Slider, defStyleAttr, DEF_STYLE_RES);
    valueFrom = a.getFloat(R.styleable.Slider_android_valueFrom, 0.0f);
    valueTo = a.getFloat(R.styleable.Slider_android_valueTo, 1.0f);
    setValue(a.getFloat(R.styleable.Slider_android_value, valueFrom));
    stepSize = a.getFloat(R.styleable.Slider_android_stepSize, 0.0f);

    boolean hasTrackColor = a.hasValue(R.styleable.Slider_trackColor);

    int inactiveTrackColorRes =
        hasTrackColor ? R.styleable.Slider_trackColor : R.styleable.Slider_inactiveTrackColor;
    int activeTrackColorRes =
        hasTrackColor ? R.styleable.Slider_trackColor : R.styleable.Slider_activeTrackColor;

    inactiveTrackColor = MaterialResources.getColorStateList(context, a, inactiveTrackColorRes);
    activeTrackColor = MaterialResources.getColorStateList(context, a, activeTrackColorRes);
    thumbColor = MaterialResources.getColorStateList(context, a, R.styleable.Slider_thumbColor);
    tickColor = MaterialResources.getColorStateList(context, a, R.styleable.Slider_activeTickColor);
    textColor = MaterialResources.getColorStateList(context, a, R.styleable.Slider_labelColor);

    thumbRadius = a.getDimensionPixelSize(R.styleable.Slider_thumbRadius, 0);
    haloRadius = a.getDimensionPixelSize(R.styleable.Slider_haloRadius, 0);
    a.recycle();

    validateValueFrom();
    validateValueTo();
    validateStepSize();
  }

  private void validateValueFrom() {
    if (valueFrom >= valueTo) {
      Log.e(TAG, EXCEPTION_ILLEGAL_VALUE_FROM);
      throw new IllegalArgumentException(EXCEPTION_ILLEGAL_VALUE_FROM);
    }
  }

  private void validateValueTo() {
    if (valueTo <= valueFrom) {
      Log.e(TAG, EXCEPTION_ILLEGAL_VALUE_TO);
      throw new IllegalArgumentException(EXCEPTION_ILLEGAL_VALUE_TO);
    }
  }

  private void validateStepSize() {
    if (stepSize < 0.0f) {
      Log.e(TAG, EXCEPTION_ILLEGAL_STEP_SIZE);
      throw new IllegalArgumentException(EXCEPTION_ILLEGAL_STEP_SIZE);
    } else if (stepSize > 0.0f && (valueTo - valueFrom) % stepSize != 0.0f) {
      Log.e(TAG, EXCEPTION_ILLEGAL_STEP_SIZE);
      throw new IllegalArgumentException(EXCEPTION_ILLEGAL_STEP_SIZE);
    }
  }

  /** Returns the slider's {@code valueFrom} value. */
  public float getValueFrom() {
    return valueFrom;
  }

  /**
   * Sets the slider's {@code valueFrom} value.
   *
   * <p>The {@code valueFrom} value must be strictly lower than the {@code valueTo} value. If that
   * is not the case, an {@link IllegalArgumentException} will be thrown.
   *
   * @param valueFrom The minimum value for the slider's range of values
   * @throws IllegalArgumentException If {@code valueFrom} is greater or equal to {@code valueTo}
   */
  public void setValueFrom(float valueFrom) {
    this.valueFrom = valueFrom;
    validateValueFrom();
  }

  /** Returns the slider's {@code valueTo} value. */
  public float getValueTo() {
    return valueTo;
  }

  /**
   * Sets the slider's {@code valueTo} value.
   *
   * <p>The {@code valueTo} value must be strictly greater than the {@code valueFrom} value. If that
   * is not the case, an {@link IllegalArgumentException} will be thrown.
   *
   * @param valueTo The maximum value for the slider's range of values
   * @throws IllegalArgumentException If {@code valueTo} is lesser or equal to {@code valueFrom}
   */
  public void setValueTo(float valueTo) {
    this.valueTo = valueTo;
    validateValueTo();
  }

  /** Returns the value of the slider. */
  public float getValue() {
    return thumbPosition * (valueTo - valueFrom) + valueFrom;
  }

  /**
   * Sets the value of the slider.
   *
   * <p>The thumb value must be greater or equal to {@code valueFrom}, and lesser or equal to {@code
   * valueTo}. If that is not the case, an {@link IllegalArgumentException} will be thrown.
   *
   * <p>If the slider is in discrete mode (i.e. the tick increment value is greater than 0), the
   * thumb's value must be set to a value falls on a tick (i.e.: {@code value == valueFrom + x *
   * stepSize}, where {@code x} is an integer equal to or greater than 0). If that is not the case,
   * an {@link IllegalArgumentException} will be thrown.
   *
   * @param value The value to which to set the slider
   * @throws IllegalArgumentException If the value is not within {@code valueFrom} and {@code
   *     valueTo}. If stepSize is greater than 0 and value does not fall on a tick
   */
  public void setValue(float value) {
    if (isValueValid(value)) {
      thumbPosition = (value - valueFrom) / (valueTo - valueFrom);
      if (hasOnChangeListener()) {
        listener.onValueChange(this, getValue());
      }
    }
  }

  private boolean isValueValid(float value) {
    if (value < valueFrom || value > valueTo) {
      Log.e(TAG, EXCEPTION_ILLEGAL_VALUE);
      return false;
    }
    if (stepSize > 0.0f && ((valueFrom - value) % stepSize) != 0.0f) {
      Log.e(TAG, EXCEPTION_ILLEGAL_DISCRETE_VALUE);
      return false;
    }
    return true;
  }

  /**
   * Returns the step size used to mark the ticks.
   *
   * <p>A step size of 0 means that the slider is operating in continuous mode. A step size greater
   * than 0 means that the slider is operating in discrete mode.
   */
  public float getStepSize() {
    return stepSize;
  }

  /**
   * Sets the step size to use to mark the ticks.
   *
   * <p>Setting this value to 0 will make the slider operate in continuous mode. Setting this value
   * to a number greater than 0 will make the slider operate in discrete mode.
   *
   * <p>The step size must evenly divide the range described by the {@code valueFrom} and {@code
   * valueTo}, it must be a factor of the range. If the step size is not a factor of the range, an
   * {@link IllegalArgumentException} will be thrown.
   *
   * <p>Setting this value to a negative value will result in an {@link IllegalArgumentException}.
   *
   * @param stepSize The interval value at which ticks must be drawn. Set to 0 to operate the slider
   *     in continuous mode and not have any ticks.
   * @throws IllegalArgumentException If the step size is not a factor of the {@code
   *     valueFrom}-{@code valueTo} range. If the step size is less than 0
   */
  public void setStepSize(float stepSize) {
    this.stepSize = stepSize;
    validateStepSize();
    requestLayout();
  }

  /**
   * Returns {@code true} if the slider has an {@link OnChangeListener} attached, {@code false}
   * otherwise.
   */
  public boolean hasOnChangeListener() {
    return listener != null;
  }

  /**
   * Registers a callback to be invoked when the slider changes.
   *
   * @param listener The callback to run when the slider changes
   */
  public void setOnChangeListener(@Nullable OnChangeListener listener) {
    this.listener = listener;
  }

  /**
   * Returns {@code true} if the slider has a {@link LabelFormatter} attached, {@code false}
   * otherwise.
   */
  public boolean hasLabelFormatter() {
    return formatter != null;
  }

  /**
   * Registers a {@link LabelFormatter} to be used to format the value displayed in the bubble shown
   * when the slider operates in discrete mode.
   *
   * @param formatter The {@link LabelFormatter} to use to format the bubble's text
   */
  public void setLabelFormatter(@Nullable LabelFormatter formatter) {
    this.formatter = formatter;
  }

  /** Sets the radius of the thumb in pixels. */
  public void setThumbRadius(@IntRange(from = 0) @Dimension int radius) {
    thumbRadius = radius;
    postInvalidate();
  }

  /** Sets the radius of the thumb from a dimension resource. */
  public void setThumbRadiusResource(@DimenRes int radius) {
    setThumbRadius(getResources().getDimensionPixelSize(radius));
  }

  /** Returns the radius of the thumb. */
  @Dimension
  public int getThumbRadius() {
    return thumbRadius;
  }

  /** Sets the radius of the halo in pixels. */
  public void setHaloRadius(@IntRange(from = 0) @Dimension int radius) {
    haloRadius = radius;
    postInvalidate();
  }

  /** Sets the radius of the halo from a dimension resource. */
  public void setHaloRadiusResource(@DimenRes int radius) {
    setHaloRadius(getResources().getDimensionPixelSize(radius));
  }

  /** Returns the radius of the halo. */
  @Dimension()
  public int getHaloRadius() {
    return haloRadius;
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(
        widthMeasureSpec,
        MeasureSpec.makeMeasureSpec(
            stepSize > 0.0f ? widgetHeightDiscrete : widgetHeight, MeasureSpec.EXACTLY));
  }

  @Override
  protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    updateTrackWidthAndTicksCoordinates(w);
  }

  private void updateTrackWidthAndTicksCoordinates(int viewWidth) {
    trackWidth = viewWidth - trackSidePadding * 2;
    if (stepSize > 0.0f) {
      int tickCount = (int) ((valueTo - valueFrom) / stepSize + 1);
      if (ticksCoordinates == null || ticksCoordinates.length != tickCount * 2) {
        ticksCoordinates = new float[tickCount * 2];
      }
      float interval = trackWidth / (float) (tickCount - 1);
      for (int i = 0; i < tickCount * 2; i += 2) {
        ticksCoordinates[i] = trackSidePadding + i / 2 * interval;
        ticksCoordinates[i + 1] = trackTopDiscrete;
      }
    }
  }

  @Override
  protected void onDraw(@NonNull Canvas canvas) {
    super.onDraw(canvas);

    int top = stepSize > 0.0f ? trackTopDiscrete : trackTop;

    drawTrack(canvas, trackWidth, top);
    if (thumbPosition > 0.0f) {
      drawMarker(canvas, trackWidth, top);
    }
    if (stepSize > 0.0f) {
      if (hasFocus() && isEnabled()) {
        drawLabel(canvas, trackWidth, top);
        drawLabelText(canvas, trackWidth, top);
      } else {
        drawThumb(canvas, trackWidth, top);
      }
      if (thumbIsPressed) {
        drawTicks(canvas);
      }
    } else {
      if (!thumbIsPressed && hasFocus() && isEnabled()) {
        drawHalo(canvas, trackWidth, top);
      }
      drawThumb(canvas, trackWidth, top);
    }
  }

  private void drawTrack(@NonNull Canvas canvas, int width, int top) {
    float right = trackSidePadding + thumbPosition * width;
    if (!isEnabled()) {
      right += thumbRadius + thumbPaddingDisabled;
    }
    if (right < trackSidePadding + width) {
      canvas.drawLine(right, top, trackSidePadding + width, top, inactiveTrackPaint);
    }
  }

  private void drawMarker(@NonNull Canvas canvas, int width, int top) {
    float left = trackSidePadding + thumbPosition * width;
    if (!isEnabled()) {
      left -= thumbPaddingDisabled + thumbRadius;
    }
    canvas.drawLine(trackSidePadding, top, left, top, activeTrackPaint);
  }

  private void drawTicks(@NonNull Canvas canvas) {
    canvas.drawPoints(ticksCoordinates, ticksPaint);
  }

  private void drawLabel(@NonNull Canvas canvas, int width, int top) {
    int left = trackSidePadding + (int) (thumbPosition * width) - labelWidth / 2;
    top -= labelTopOffset;
    label.setBounds(left, top, left + labelWidth, top + labelHeight);
    label.draw(canvas);
  }

  private void drawLabelText(@NonNull Canvas canvas, int width, int top) {
    labelTextPaint.getTextBounds(labelText, 0, labelText.length(), labelTextBounds);
    int left = trackSidePadding + (int) (thumbPosition * width) - labelTextBounds.width() / 2;
    canvas.drawText(labelText, left, top - labelTextTopOffset, labelTextPaint);
  }

  private void drawThumb(@NonNull Canvas canvas, int width, int top) {
    if (isEnabled()) {
      thumbPaint.setStyle(Paint.Style.FILL);
    } else {
      thumbPaint.setStyle(Paint.Style.STROKE);
      thumbPaint.setStrokeWidth(lineHeight);
    }

    canvas.drawCircle(trackSidePadding + thumbPosition * width, top, thumbRadius, thumbPaint);
  }

  private void drawHalo(@NonNull Canvas canvas, int width, int top) {
    canvas.drawCircle(trackSidePadding + thumbPosition * width, top, haloRadius, haloPaint);
  }

  @Override
  public boolean onTouchEvent(@NonNull MotionEvent event) {
    if (!isEnabled()) {
      return false;
    }
    float x = event.getX();
    float position = (x - trackSidePadding) / trackWidth;
    position = Math.max(0, position);
    position = Math.min(1, position);

    switch (event.getActionMasked()) {
      case MotionEvent.ACTION_DOWN:
        getParent().requestDisallowInterceptTouchEvent(true);
        requestFocus();
        thumbIsPressed = true;
        thumbPosition = position;
        snapThumbPosition();
        invalidate();
        if (hasOnChangeListener()) {
          listener.onValueChange(this, getValue());
        }
        break;
      case MotionEvent.ACTION_MOVE:
        thumbPosition = position;
        snapThumbPosition();
        invalidate();
        if (hasOnChangeListener()) {
          listener.onValueChange(this, getValue());
        }
        break;
      case MotionEvent.ACTION_UP:
        getParent().requestDisallowInterceptTouchEvent(false);
        thumbIsPressed = false;
        thumbPosition = position;
        snapThumbPosition();
        invalidate();
        break;
      default:
        // Nothing to do in this case.
    }
    float value = getValue();
    if (hasLabelFormatter()) {
      labelText = formatter.getFormattedValue(value);
    } else {
      labelText = String.format((int) value == value ? "%.0f" : "%.2f", value);
    }
    return true;
  }

  private void snapThumbPosition() {
    if (stepSize > 0.0f) {
      int intervalsCovered = Math.round(thumbPosition * (ticksCoordinates.length / 2 - 1));
      thumbPosition = (float) intervalsCovered / (ticksCoordinates.length / 2 - 1);
    }
  }

  @Override
  protected void drawableStateChanged() {
    super.drawableStateChanged();

    inactiveTrackPaint.setColor(getColorForState(inactiveTrackColor));
    activeTrackPaint.setColor(getColorForState(activeTrackColor));
    ticksPaint.setColor(getColorForState(tickColor));
    labelTextPaint.setColor(getColorForState(textColor));
    thumbPaint.setColor(getColorForState(thumbColor));
    haloPaint.setColor(getColorForState(thumbColor));
    haloPaint.setAlpha(HALO_ALPHA);
  }

  @ColorInt
  private int getColorForState(@NonNull ColorStateList colorStateList) {
    return colorStateList.getColorForState(getDrawableState(), colorStateList.getDefaultColor());
  }

  @Override
  protected Parcelable onSaveInstanceState() {
    Parcelable superState = super.onSaveInstanceState();
    SliderState sliderState = new SliderState(superState);
    sliderState.valueFrom = valueFrom;
    sliderState.valueTo = valueTo;
    sliderState.thumbPosition = thumbPosition;
    sliderState.stepSize = stepSize;
    sliderState.hasFocus = hasFocus();
    return sliderState;
  }

  @Override
  protected void onRestoreInstanceState(Parcelable state) {
    SliderState sliderState = (SliderState) state;
    super.onRestoreInstanceState(sliderState.getSuperState());

    valueFrom = sliderState.valueFrom;
    valueTo = sliderState.valueTo;
    thumbPosition = sliderState.thumbPosition;
    stepSize = sliderState.stepSize;
    if (sliderState.hasFocus) {
      requestFocus();
    }
    if (hasOnChangeListener()) {
      listener.onValueChange(this, getValue());
    }
  }

  static class SliderState extends BaseSavedState {

    float valueFrom;
    float valueTo;
    float thumbPosition;
    float stepSize;
    float[] ticksCoordinates;
    boolean hasFocus;

    public static final Parcelable.Creator<SliderState> CREATOR =
        new Parcelable.Creator<SliderState>() {

          @NonNull
          @Override
          public SliderState createFromParcel(@NonNull Parcel source) {
            return new SliderState(source);
          }

          @NonNull
          @Override
          public SliderState[] newArray(int size) {
            return new SliderState[size];
          }
        };

    SliderState(Parcelable superState) {
      super(superState);
    }

    private SliderState(@NonNull Parcel source) {
      super(source);
      valueFrom = source.readFloat();
      valueTo = source.readFloat();
      thumbPosition = source.readFloat();
      stepSize = source.readFloat();
      source.readFloatArray(ticksCoordinates);
      hasFocus = source.createBooleanArray()[0];
    }

    @Override
    public void writeToParcel(@NonNull Parcel dest, int flags) {
      super.writeToParcel(dest, flags);
      dest.writeFloat(valueFrom);
      dest.writeFloat(valueTo);
      dest.writeFloat(thumbPosition);
      dest.writeFloat(stepSize);
      dest.writeFloatArray(ticksCoordinates);
      boolean[] booleans = new boolean[1];
      booleans[0] = hasFocus;
      dest.writeBooleanArray(booleans);
    }
  }
}