/*
 * Copyright (C) 2011 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.huetoyou.chatexchange.ui.misc;

import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Parcelable;
import android.support.annotation.Nullable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;

/**
 * Implementation of {@link android.support.v4.view.PagerAdapter} that
 * represents each page as a {@link Fragment} that is persistently
 * kept in the fragment manager as long as the user can return to the page.
 * <p>
 * <p>This version of the pager is best for use when there are a handful of
 * typically more static fragments to be paged through, such as a set of tabs.
 * The fragment of each page the user visits will be kept in memory, though its
 * view hierarchy may be destroyed when not visible.  This can result in using
 * a significant amount of memory since fragment instances can hold on to an
 * arbitrary amount of state.  For larger sets of pages, consider
 * <p>
 * <p>When using FragmentPagerAdapter the host ViewPager must have a
 * valid ID set.</p>
 * <p>
 * <p>Subclasses only need to implement {@link #getItem(int)}
 * and {@link #getCount()} to have a working adapter.
 * <p>
 * <p>Here is an example implementation of a pager containing fragments of
 * lists:
 * <p>
 * {@sample development/samples/Support4Demos/src/com/example/android/supportv4/app/FragmentPagerSupport.java
 * complete}
 * <p>
 * <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is:
 * <p>
 * {@sample development/samples/Support4Demos/res/layout/fragment_pager.xml
 * complete}
 * <p>
 * <p>The <code>R.layout.fragment_pager_list</code> resource containing each
 * individual fragment's layout is:
 * <p>
 * {@sample development/samples/Support4Demos/res/layout/fragment_pager_list.xml
 * complete}
 */
public abstract class HueFragmentPagerAdapter extends PagerAdapter
{
    private static final String TAG = "FragmentPagerAdapter";
    private static final boolean DEBUG = false;
    private final FragmentManager mFragmentManager;
    private FragmentTransaction mCurTransaction = null;
    private Fragment mCurrentPrimaryItem = null;

    public HueFragmentPagerAdapter(FragmentManager fm)
    {
        mFragmentManager = fm;
    }

    /**
     * Return the Fragment associated with a specified position.
     */
    public abstract android.app.Fragment getItem(int position);

    @Override
    public void startUpdate(ViewGroup container)
    {
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position)
    {
        if (mCurTransaction == null)
        {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        final long itemId = getItemId(position);
        // Do we already have this fragment?
        String name = makeFragmentName(container.getId(), itemId);
        Fragment fragment = mFragmentManager.findFragmentByTag(name);
        if (fragment != null)
        {
            if (DEBUG)
            {
                Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
            }
            mCurTransaction.attach(fragment);
        }
        else
        {
            fragment = getItem(position);
            if (DEBUG)
            {
                Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
            }
            mCurTransaction.add(container.getId(), fragment,
                    makeFragmentName(container.getId(), itemId));
        }
        if (fragment != mCurrentPrimaryItem)
        {
            fragment.setMenuVisibility(false);
            fragment.setUserVisibleHint(false);
        }
        return fragment;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object)
    {
        if (mCurTransaction == null)
        {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        if (DEBUG)
        {
            Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object
                    + " v=" + ((Fragment) object).getView());
        }
        mCurTransaction.detach((Fragment) object);
    }

    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object)
    {
        Fragment fragment = (Fragment) object;
        if (fragment != mCurrentPrimaryItem)
        {
            if (mCurrentPrimaryItem != null)
            {
                mCurrentPrimaryItem.setMenuVisibility(false);
                mCurrentPrimaryItem.setUserVisibleHint(false);
            }
            if (fragment != null)
            {
                fragment.setMenuVisibility(true);
                fragment.setUserVisibleHint(true);
            }
            mCurrentPrimaryItem = fragment;
        }
    }

    @Override
    public void finishUpdate(ViewGroup container)
    {
        if (mCurTransaction != null)
        {
            mCurTransaction.commitAllowingStateLoss();
            mCurTransaction = null;
            mFragmentManager.executePendingTransactions();
        }
    }

    @Override
    public boolean isViewFromObject(View view, Object object)
    {
        return ((Fragment) object).getView() == view;
    }

    @Override
    public Parcelable saveState()
    {
        return null;
    }

    @Override
    public void restoreState(Parcelable state, ClassLoader loader)
    {
    }

    /**
     * Return a unique identifier for the item at the given position.
     * <p>
     * <p>The default implementation returns the given position.
     * Subclasses should override this method if the positions of items can change.</p>
     *
     * @param position Position within this adapter
     * @return Unique identifier for the item at position
     */
    public long getItemId(int position)
    {
        return position;
    }

    /**
     * @param containerViewId the ViewPager this adapter is being supplied to
     * @param id              pass in getItemId(position) as this is whats used internally in this class
     * @return the tag used for this pages fragment
     */
    public static String makeFragmentName(int containerViewId, long id)
    {
        return "android:switcher:" + containerViewId + ":" + id;
    }

    /**
     * @return may return null if the fragment has not been instantiated yet for that position - this depends on if the fragment has been viewed
     * yet OR is a sibling covered by {@link android.support.v4.view.ViewPager#setOffscreenPageLimit(int)}. Can use this to call methods on
     * the current positions fragment.
     */
    public @Nullable
    Fragment getFragmentForPosition(ViewPager mViewPager, int position)
    {
        String tag = makeFragmentName(mViewPager.getId(), getItemId(position));
        return mFragmentManager.findFragmentByTag(tag);
    }
}