package com.hjq.md.widget;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.webkit.WebView;

/**
 * NestedScrollWebView
 */
public class NestedScrollWebView extends WebView implements NestedScrollingChild {

 private NestedScrollingChildHelper mChildHelper;

 private int mLastMotionY;

 private final int[] mScrollOffset = new int[2];
 private final int[] mScrollConsumed = new int[2];

 private int mNestedYOffset;
 private boolean mChange;

 public NestedScrollWebView(Context context) {
 super(context);
 init();
 }

 public NestedScrollWebView(Context context, AttributeSet attrs) {
 super(context, attrs);
 init();
 }

 public NestedScrollWebView(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 init();
 }

 @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
 public NestedScrollWebView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
 super(context, attrs, defStyleAttr, defStyleRes);
 init();
 }

 public NestedScrollWebView(Context context, AttributeSet attrs, int defStyleAttr, boolean privateBrowsing) {
 super(context, attrs, defStyleAttr, privateBrowsing);
 init();
 }

 private void init() {
 if (mChildHelper == null) {
 mChildHelper = new NestedScrollingChildHelper(this);
 setNestedScrollingEnabled(true);
 }
 }

 @SuppressLint("ClickableViewAccessibility")
 @Override
 public boolean onTouchEvent(MotionEvent event) {
 boolean result = false;

 MotionEvent trackedEvent = MotionEvent.obtain(event);

 final int action = event.getActionMasked();

 if (action == MotionEvent.ACTION_DOWN) {
 mNestedYOffset = 0;
 }

 int y = (int) event.getY();

 event.offsetLocation(0, mNestedYOffset);

 switch (action) {
 case MotionEvent.ACTION_DOWN:
 mChange = false;
 mLastMotionY = y;
 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
 result = super.onTouchEvent(event);
 break;
 case MotionEvent.ACTION_MOVE:
 int deltaY = mLastMotionY - y;

 if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
 deltaY -= mScrollConsumed[1];
 trackedEvent.offsetLocation(0, mScrollOffset[1]);
 mNestedYOffset += mScrollOffset[1];
 }

 mLastMotionY = y - mScrollOffset[1];

 int oldY = getScrollY();
 int newScrollY = Math.max(0, oldY + deltaY);
 int dyConsumed = newScrollY - oldY;
 int dyUnconsumed = deltaY - dyConsumed;

 if (dispatchNestedScroll(0, dyConsumed, 0, dyUnconsumed, mScrollOffset)) {
 mLastMotionY -= mScrollOffset[1];
 trackedEvent.offsetLocation(0, mScrollOffset[1]);
 mNestedYOffset += mScrollOffset[1];
 }

 if(mScrollConsumed[1]==0 && mScrollOffset[1]==0) {
 if(mChange){
 mChange =false;
 trackedEvent.setAction(MotionEvent.ACTION_DOWN);
 super.onTouchEvent(trackedEvent);
 }else {
 result = super.onTouchEvent(trackedEvent);
 }
 trackedEvent.recycle();
 }else{
 if(!mChange){
 mChange = true;
 super.onTouchEvent(MotionEvent.obtain(0,0,MotionEvent.ACTION_CANCEL,0,0,0));
 }
 }

 //result = super.onTouchEvent(trackedEvent);
 //trackedEvent.recycle();
 break;
 case MotionEvent.ACTION_POINTER_DOWN:
 case MotionEvent.ACTION_UP:
 case MotionEvent.ACTION_CANCEL:
 stopNestedScroll();
 result = super.onTouchEvent(event);
 break;
 }
 return result;
 }

 // NestedScrollingChild

 @Override
 public void setNestedScrollingEnabled(boolean enabled) {
 mChildHelper.setNestedScrollingEnabled(enabled);
 }

 @Override
 public boolean isNestedScrollingEnabled() {
 return mChildHelper.isNestedScrollingEnabled();
 }

 @Override
 public boolean startNestedScroll(int axes) {
 return mChildHelper.startNestedScroll(axes);
 }

 @Override
 public void stopNestedScroll() {
 mChildHelper.stopNestedScroll();
 }

 @Override
 public boolean hasNestedScrollingParent() {
 return mChildHelper.hasNestedScrollingParent();
 }

 @Override
 public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
 return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
 }

 @Override
 public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
 return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
 }

 @Override
 public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
 return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
 }

 @Override
 public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
 return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
 }
}