/*
Copyright 2020 Wajahat Karim

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.wajahatkarim3.easyflipviewpager;

import android.view.View;
import android.view.ViewParent;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager2.widget.ViewPager2;

/**
 * A book based page flip animation PageTransformer implementation for ViewPager2
 *
 * Set the object of this transformer to any ViewPager object.
 * For example, myViewPager.setPageTransformer(true, new BookFlipPageTransformer2());
 *
 * @see <a href="http://github.com/wajahatkarim3/EasyFlipViewPager">EasyFlipViewPager</a>
 *
 * @author Wajahat Karim (http://wajahatkarim.com)
 */
public class BookFlipPageTransformer2 implements ViewPager2.PageTransformer {

    private final int LEFT = -1;
    private final int RIGHT = 1;
    private final int CENTER = 0;

    private float scaleAmountPercent = 5f;
    private boolean enableScale = true;

    @Override
    public void transformPage(@NonNull View page, float position) {
        float percentage = 1 - Math.abs(position);
        ViewPager2 viewPager = requireViewPager(page);
        // Don't move pages once they are on left or right
        if (position > CENTER && position <= RIGHT)
        {
            if (viewPager.getOrientation() == ViewPager2.ORIENTATION_HORIZONTAL)
            {
                // This is behind page
                page.setTranslationX(-position * (page.getWidth()));
                page.setTranslationY(0);
                page.setTranslationZ(-1);
                page.setRotation(0);
                if (enableScale)
                {
                    float amount = ((100 - scaleAmountPercent) + ( scaleAmountPercent * percentage)) / 100;
                    setSize(page, position, amount);
                }
            }
            else
            {
                // This is behind page
                page.setTranslationY(-position * (page.getHeight()));
                page.setTranslationX(0);
                page.setTranslationZ(-1);
                page.setRotation(0);
                if (enableScale)
                {
                    float amount = ((100 - scaleAmountPercent) + ( scaleAmountPercent * percentage)) / 100;
                    setSize(page, position, amount);
                }
            }

        }
        // Otherwise flip the current page
        else
        {
            page.setVisibility(View.VISIBLE);
            flipPage(page, position, percentage);
        }
    }

    private void flipPage(View page, float position, float percentage)
    {

        // Flip this page
        page.setCameraDistance(-30000);
        setVisibility(page, position);
        setTranslation(page);
        if (requireViewPager(page).getOrientation() == ViewPager2.ORIENTATION_HORIZONTAL)
        {
            setPivot(page, 0f, page.getHeight() * 0.5f);
        }
        else if (requireViewPager(page).getOrientation() == ViewPager2.ORIENTATION_VERTICAL)
        {
            setPivot(page, page.getWidth() * 0.5f, 0f);
        }

        setRotation(page, position, percentage);
    }

    private void setPivot(View page, float pivotX, float pivotY)
    {
        page.setPivotX(pivotX);
        page.setPivotY(pivotY);
    }

    private void setVisibility(View page, float position) {
        if (position < 0.5 && position > -0.5) {
            page.setVisibility(View.VISIBLE);
        } else {
            page.setVisibility(View.INVISIBLE);
        }
    }

    private void setTranslation(View page) {
        ViewPager2 viewPager = requireViewPager(page);
        if (viewPager.getOrientation() == ViewPager2.ORIENTATION_HORIZONTAL)
        {
            int scroll = viewPager.getScrollX() - page.getLeft();
            page.setTranslationX(scroll);
        }
        else if (viewPager.getOrientation() == ViewPager2.ORIENTATION_VERTICAL)
        {
            int scroll = viewPager.getScrollY() - page.getTop();
            page.setTranslationY(scroll);
        }
        page.setTranslationZ(1f);
    }

    private void setSize(View page, float position, float percentage) {
        page.setScaleX((position != 0 && position != 1) ? percentage : 1);
        page.setScaleY((position != 0 && position != 1) ? percentage : 1);
    }

    private void setRotation(View page, float position, float percentage) {
        ViewPager2 viewPager = requireViewPager(page);
        if (viewPager.getOrientation() == ViewPager2.ORIENTATION_HORIZONTAL)
        {
            if (position > 0) {
                page.setRotationY(-180 * (percentage + 1));
            } else {
                page.setRotationY(180 * (percentage + 1));
            }
        }
        else if (viewPager.getOrientation() == ViewPager2.ORIENTATION_VERTICAL)
        {
            if (position > 0) {
                page.setRotationX(180 * (percentage + 1));
            } else {
                page.setRotationX(-180 * (percentage + 1));
            }
        }
    }

    private ViewPager2 requireViewPager(@NonNull View page) {
        ViewParent parent = page.getParent();
        ViewParent parentParent = parent.getParent();

        if (parent instanceof RecyclerView && parentParent instanceof ViewPager2) {
            return (ViewPager2) parentParent;
        }

        throw new IllegalStateException(
                "Expected the page view to be managed by a ViewPager2 instance.");
    }

    //region Getters/Setters
    public float getScaleAmountPercent() {
        return scaleAmountPercent;
    }

    public void setScaleAmountPercent(float scaleAmountPercent) {
        this.scaleAmountPercent = scaleAmountPercent;
    }

    public boolean isEnableScale() {
        return enableScale;
    }

    public void setEnableScale(boolean enableScale) {
        this.enableScale = enableScale;
    }

    //endregion
}