/*
 * Copyright (C) 2015 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.android.setupwizardlib.view;

import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.view.WindowInsets;

/**
 * This class provides sticky header functionality in a scroll view, to use with
 * SetupWizardIllustration. To use this, add a subview tagged with "sticky", or a subview tagged
 * with "stickyContainer" and one of its child tagged as "sticky". The sticky container will be
 * drawn when the sticky element hits the top of the view.
 *
 * <p>There are a few things to note:
 *
 * <ol>
 *   <li>The two supported scenarios are StickyHeaderScrollView -> subview (stickyContainer) ->
 *       sticky, and StickyHeaderScrollView -> container -> subview (sticky). The arrow (->)
 *       represents parent/child relationship and must be immediate child.
 *   <li>If fitsSystemWindows is true, then this will offset the sticking position by the height of
 *       the system decorations at the top of the screen.
 *   <li>For versions before Honeycomb, this will behave like a regular ScrollView.
 * </ol>
 *
 * @see StickyHeaderListView
 */
public class StickyHeaderScrollView extends BottomScrollView {

  private View sticky;
  private View stickyContainer;
  private int statusBarInset = 0;

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

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

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

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    super.onLayout(changed, l, t, r, b);
    if (sticky == null) {
      updateStickyView();
    }
    updateStickyHeaderPosition();
  }

  public void updateStickyView() {
    sticky = findViewWithTag("sticky");
    stickyContainer = findViewWithTag("stickyContainer");
  }

  private void updateStickyHeaderPosition() {
    // Note: for pre-Honeycomb the header will not be moved, so this ScrollView essentially
    // behaves like a normal BottomScrollView.
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
      if (sticky != null) {
        // The view to draw when sticking to the top
        final View drawTarget = stickyContainer != null ? stickyContainer : sticky;
        // The offset to draw the view at when sticky
        final int drawOffset = stickyContainer != null ? sticky.getTop() : 0;
        // Position of the draw target, relative to the outside of the scrollView
        final int drawTop = drawTarget.getTop() - getScrollY();
        if (drawTop + drawOffset < statusBarInset || !drawTarget.isShown()) {
          // ScrollView translates the whole canvas so we have to compensate for that
          drawTarget.setTranslationY(getScrollY() - drawOffset);
        } else {
          drawTarget.setTranslationY(0);
        }
      }
    }
  }

  @Override
  protected void onScrollChanged(int l, int t, int oldl, int oldt) {
    super.onScrollChanged(l, t, oldl, oldt);
    updateStickyHeaderPosition();
  }

  @Override
  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  public WindowInsets onApplyWindowInsets(WindowInsets insets) {
    if (getFitsSystemWindows()) {
      statusBarInset = insets.getSystemWindowInsetTop();
      insets =
          insets.replaceSystemWindowInsets(
              insets.getSystemWindowInsetLeft(),
              0, /* top */
              insets.getSystemWindowInsetRight(),
              insets.getSystemWindowInsetBottom());
    }
    return insets;
  }
}