package io.github.longluo.ui.layout;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.webkit.WebView;

import androidx.core.view.NestedScrollingChild;
import androidx.core.view.NestedScrollingChildHelper;
import androidx.core.view.ViewCompat;

/**
 * 支持嵌套滚动的 WebView
 */
public class NestedScrollWebView extends WebView implements NestedScrollingChild {

    private final NestedScrollingChildHelper mChildHelper;

    private int mLastMotionY;

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

    private int mNestedOffsetY;
    private boolean mChange;

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

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

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

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

    {
        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) {
            mNestedOffsetY = 0;
        }

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

        event.offsetLocation(0, mNestedOffsetY);

        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]);
                    mNestedOffsetY += 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]);
                    mNestedOffsetY += 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_POINTER_UP:
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                stopNestedScroll();
                result = super.onTouchEvent(event);
                break;
            default:
                break;
        }
        return result;
    }

    /**
     * {@link 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);
    }
}