// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package org.chromium.components.browser_ui.widget.displaystyle;

import android.content.res.Resources;
import android.view.View;

import androidx.core.view.ViewCompat;

/**
 * Changes a view's padding when switching between {@link UiConfig} display styles. If the display
 * style is {@link HorizontalDisplayStyle#REGULAR}, a predetermined value will be used to set the
 * lateral padding. If the display style is {@link HorizontalDisplayStyle#WIDE}, the lateral padding
 * will be calculated using the available screen width to keep the view constrained to
 * {@link UiConfig#WIDE_DISPLAY_STYLE_MIN_WIDTH_DP}
 */
public class ViewResizer implements DisplayStyleObserver {
    /** The default value for the lateral padding. */
    private int mDefaultPaddingPixels;
    /** The minimum wide display value used for the lateral padding. */
    private int mMinWidePaddingPixels;
    private final View mView;
    private final DisplayStyleObserverAdapter mDisplayStyleObserver;
    private final UiConfig mUiConfig;

    @HorizontalDisplayStyle
    private int mCurrentDisplayStyle;

    /**
     * @param view The view that will have its padding resized.
     * @param config The UiConfig object to subscribe to.
     * @param defaultPaddingPixels Padding to use in {@link HorizontalDisplayStyle#REGULAR}.
     * @param minWidePaddingPixels Minimum lateral padding to use in {@link
     *         HorizontalDisplayStyle#WIDE}.
     */
    public ViewResizer(
            View view, UiConfig config, int defaultPaddingPixels, int minWidePaddingPixels) {
        mView = view;
        mDefaultPaddingPixels = defaultPaddingPixels;
        mMinWidePaddingPixels = minWidePaddingPixels;
        mUiConfig = config;
        mDisplayStyleObserver = new DisplayStyleObserverAdapter(view, config, this);
    }

    /**
     * Convenience method to create a new ViewResizer and immediately attach it to a {@link
     * UiConfig}. If the {@link UiConfig} can outlive the view, the regular constructor should be
     * used, so it can be detached to avoid memory leaks.
     * @param view The view that will have its padding resized.
     * @param config The UiConfig object to subscribe to.
     * @param defaultPaddingPixels Padding to use in {@link HorizontalDisplayStyle#REGULAR}.
     * @param minWidePaddingPixels Minimum lateral padding to use in {@link
     *         HorizontalDisplayStyle#WIDE}.
     * @return The {@link ViewResizer} that is created and attached.
     */
    public static ViewResizer createAndAttach(
            View view, UiConfig config, int defaultPaddingPixels, int minWidePaddingPixels) {
        ViewResizer viewResizer =
                new ViewResizer(view, config, defaultPaddingPixels, minWidePaddingPixels);
        viewResizer.attach();
        return viewResizer;
    }

    /**
     * Attaches to the {@link UiConfig}.
     */
    public void attach() {
        mDisplayStyleObserver.attach();
    }

    /**
     * Detaches from the {@link UiConfig}.
     */
    public void detach() {
        mDisplayStyleObserver.detach();
    }

    @Override
    public void onDisplayStyleChanged(UiConfig.DisplayStyle newDisplayStyle) {
        mCurrentDisplayStyle = newDisplayStyle.horizontal;
        updatePadding();
    }

    /**
     * Sets the lateral padding on the associated view, using the appropriate value depending on
     * the current display style.
     * @param defaultPaddingPixels Padding to use in {@link HorizontalDisplayStyle#REGULAR}.
     * @param minWidePaddingPixels Minimum lateral padding to use in {@link
     *         HorizontalDisplayStyle#WIDE}.
     */
    public void setPadding(int defaultPaddingPixels, int minWidePaddingPixels) {
        mDefaultPaddingPixels = defaultPaddingPixels;
        mMinWidePaddingPixels = minWidePaddingPixels;
        updatePadding();
    }

    private void updatePadding() {
        int padding;
        if (mCurrentDisplayStyle == HorizontalDisplayStyle.WIDE) {
            padding = computePadding();
        } else {
            padding = mDefaultPaddingPixels;
        }
        ViewCompat.setPaddingRelative(
                mView, padding, mView.getPaddingTop(), padding, mView.getPaddingBottom());
    }

    private int computePadding() {
        // mUiConfig.getContext().getResources() is used here instead of mView.getResources()
        // because lemon compression, somehow, causes the resources to return a different
        // configuration.
        Resources resources = mUiConfig.getContext().getResources();
        int screenWidthDp = resources.getConfiguration().screenWidthDp;
        float dpToPx = resources.getDisplayMetrics().density;
        int padding =
                (int) (((screenWidthDp - UiConfig.WIDE_DISPLAY_STYLE_MIN_WIDTH_DP) / 2.f) * dpToPx);
        padding = Math.max(mMinWidePaddingPixels, padding);

        return padding;
    }
}
