// Copyright 2014 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 com.android.browser.appmenu;

import android.animation.TimeAnimator;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.res.Resources;
import android.graphics.Rect;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.ListPopupWindow;
import android.widget.ListView;

import com.android.browser.R;

import java.util.ArrayList;

/**
 * Handles the drag touch events on AppMenu that start from the menu button.
 *
 * Lint suppression for NewApi is added because we are using TimeAnimator class that was marked
 * hidden in API 16.
 */
@SuppressLint("NewApi")
class AppMenuDragHelper {
    private final Activity mActivity;
    private final AppMenu mAppMenu;

    // Internally used action constants for dragging.
    private static final int ITEM_ACTION_HIGHLIGHT = 0;
    private static final int ITEM_ACTION_PERFORM = 1;
    private static final int ITEM_ACTION_CLEAR_HIGHLIGHT_ALL = 2;

    private static final float AUTO_SCROLL_AREA_MAX_RATIO = 0.25f;

    // Dragging related variables, i.e., menu showing initiated by touch down and drag to navigate.
    private final float mAutoScrollFullVelocity;
    private final TimeAnimator mDragScrolling = new TimeAnimator();
    private float mDragScrollOffset;
    private int mDragScrollOffsetRounded;
    private volatile float mDragScrollingVelocity;
    private volatile float mLastTouchX;
    private volatile float mLastTouchY;
    private final int mItemRowHeight;
    private boolean mIsSingleTapUpHappened;
    GestureDetector mGestureSingleTapDetector;

    // These are used in a function locally, but defined here to avoid heap allocation on every
    // touch event.
    private final Rect mScreenVisibleRect = new Rect();
    private final int[] mScreenVisiblePoint = new int[2];

    AppMenuDragHelper(Activity activity, AppMenu appMenu, int itemRowHeight) {
        mActivity = activity;
        mAppMenu = appMenu;
        mItemRowHeight = itemRowHeight;
        Resources res = mActivity.getResources();
        mAutoScrollFullVelocity = res.getDimensionPixelSize(R.dimen.auto_scroll_full_velocity);
        // If user is dragging and the popup ListView is too big to display at once,
        // mDragScrolling animator scrolls mPopup.getListView() automatically depending on
        // the user's touch position.
        mDragScrolling.setTimeListener(new TimeAnimator.TimeListener() {
            @Override
            public void onTimeUpdate(TimeAnimator animation, long totalTime, long deltaTime) {
                ListPopupWindow popup = mAppMenu.getPopup();
                if (popup == null || popup.getListView() == null) return;

                // We keep both mDragScrollOffset and mDragScrollOffsetRounded because
                // the actual scrolling is by the rounded value but at the same time we also
                // want to keep the precise scroll value in float.
                mDragScrollOffset += (deltaTime * 0.001f) * mDragScrollingVelocity;
                int diff = Math.round(mDragScrollOffset - mDragScrollOffsetRounded);
                mDragScrollOffsetRounded += diff;
                popup.getListView().smoothScrollBy(diff, 0);

                // Force touch move event to highlight items correctly for the scrolled position.
                if (!Float.isNaN(mLastTouchX) && !Float.isNaN(mLastTouchY)) {
                    menuItemAction(Math.round(mLastTouchX), Math.round(mLastTouchY),
                            ITEM_ACTION_HIGHLIGHT);
                }
            }
        });
        mGestureSingleTapDetector = new GestureDetector(activity, new SimpleOnGestureListener() {
            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                mIsSingleTapUpHappened = true;
                return true;
            }
        });
    }

    /**
     * Sets up all the internal state to prepare for menu dragging.
     * @param startDragging      Whether dragging is started. For example, if the app menu
     *                           is showed by tapping on a button, this should be false. If it is
     *                           showed by start dragging down on the menu button, this should be
     *                           true.
     */
    void onShow(boolean startDragging) {
        mLastTouchX = Float.NaN;
        mLastTouchY = Float.NaN;
        mDragScrollOffset = 0.0f;
        mDragScrollOffsetRounded = 0;
        mDragScrollingVelocity = 0.0f;
        mIsSingleTapUpHappened = false;

        if (startDragging) mDragScrolling.start();
    }

    /**
     * Dragging mode will be stopped by calling this function. Note that it will fall back to normal
     * non-dragging mode.
     */
    void finishDragging() {
        menuItemAction(0, 0, ITEM_ACTION_CLEAR_HIGHLIGHT_ALL);
        mDragScrolling.cancel();
    }

    /**
     * Gets all the touch events and updates dragging related logic. Note that if this app menu
     * is initiated by software UI control, then the control should set onTouchListener and forward
     * all the events to this method because the initial UI control that processed ACTION_DOWN will
     * continue to get all the subsequent events.
     *
     * @param event Touch event to be processed.
     * @return Whether the event is handled.
     */
    boolean handleDragging(MotionEvent event) {
        if (!mAppMenu.isShowing() || !mDragScrolling.isRunning()) return false;

        // We will only use the screen space coordinate (rawX, rawY) to reduce confusion.
        // This code works across many different controls, so using local coordinates will be
        // a disaster.

        final float rawX = event.getRawX();
        final float rawY = event.getRawY();
        final int roundedRawX = Math.round(rawX);
        final int roundedRawY = Math.round(rawY);
        final int eventActionMasked = event.getActionMasked();
        final ListView listView = mAppMenu.getPopup().getListView();

        mLastTouchX = rawX;
        mLastTouchY = rawY;

        if (eventActionMasked == MotionEvent.ACTION_CANCEL) {
            mAppMenu.dismiss();
            return true;
        }

        if (!mIsSingleTapUpHappened) {
            mGestureSingleTapDetector.onTouchEvent(event);
            if (mIsSingleTapUpHappened) {
                finishDragging();
            }
        }

        // After this line, drag scrolling is happening.
        if (!mDragScrolling.isRunning()) return false;

        boolean didPerformClick = false;
        int itemAction = ITEM_ACTION_CLEAR_HIGHLIGHT_ALL;
        switch (eventActionMasked) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                itemAction = ITEM_ACTION_HIGHLIGHT;
                break;
            case MotionEvent.ACTION_UP:
                itemAction = ITEM_ACTION_PERFORM;
                break;
            default:
                break;
        }
        didPerformClick = menuItemAction(roundedRawX, roundedRawY, itemAction);

        if (eventActionMasked == MotionEvent.ACTION_UP && !didPerformClick) {
            mAppMenu.dismiss();
        } else if (eventActionMasked == MotionEvent.ACTION_MOVE) {
            // Auto scrolling on the top or the bottom of the listView.
            if (listView.getHeight() > 0) {
                float autoScrollAreaRatio = Math.min(AUTO_SCROLL_AREA_MAX_RATIO,
                        mItemRowHeight * 1.2f / listView.getHeight());
                float normalizedY =
                        (rawY - getScreenVisibleRect(listView).top) / listView.getHeight();
                if (normalizedY < autoScrollAreaRatio) {
                    // Top
                    mDragScrollingVelocity = (normalizedY / autoScrollAreaRatio - 1.0f)
                            * mAutoScrollFullVelocity;
                } else if (normalizedY > 1.0f - autoScrollAreaRatio) {
                    // Bottom
                    mDragScrollingVelocity = ((normalizedY - 1.0f) / autoScrollAreaRatio + 1.0f)
                            * mAutoScrollFullVelocity;
                } else {
                    // Middle or not scrollable.
                    mDragScrollingVelocity = 0.0f;
                }
            }
        }

        return true;
    }

    /**
     * Performs the specified action on the menu item specified by the screen coordinate position.
     * @param screenX X in screen space coordinate.
     * @param screenY Y in screen space coordinate.
     * @param action  Action type to perform, it should be one of ITEM_ACTION_* constants.
     * @return true whether or not a menu item is performed (executed).
     */
    private boolean menuItemAction(int screenX, int screenY, int action) {
        ListView listView = mAppMenu.getPopup().getListView();

        ArrayList<View> itemViews = new ArrayList<View>();
        for (int i = 0; i < listView.getChildCount(); ++i) {
            boolean hasImageButtons = false;
            if (listView.getChildAt(i) instanceof LinearLayout) {
                LinearLayout layout = (LinearLayout) listView.getChildAt(i);
                for (int j = 0; j < layout.getChildCount(); ++j) {
                    itemViews.add(layout.getChildAt(j));
                    if (layout.getChildAt(j) instanceof ImageButton) hasImageButtons = true;
                }
            }
            if (!hasImageButtons) itemViews.add(listView.getChildAt(i));
        }

        boolean didPerformClick = false;
        for (int i = 0; i < itemViews.size(); ++i) {
            View itemView = itemViews.get(i);

            boolean shouldPerform = itemView.isEnabled() && itemView.isShown() &&
                    getScreenVisibleRect(itemView).contains(screenX, screenY);

            switch (action) {
                case ITEM_ACTION_HIGHLIGHT:
                    itemView.setPressed(shouldPerform);
                    break;
                case ITEM_ACTION_PERFORM:
                    if (shouldPerform) {
                        itemView.performClick();
                        didPerformClick = true;
                    }
                    break;
                case ITEM_ACTION_CLEAR_HIGHLIGHT_ALL:
                    itemView.setPressed(false);
                    break;
                default:
                    assert false;
                    break;
            }
        }
        return didPerformClick;
    }

    /**
     * @return Visible rect in screen coordinates for the given View.
     */
    private Rect getScreenVisibleRect(View view) {
        view.getLocalVisibleRect(mScreenVisibleRect);
        view.getLocationOnScreen(mScreenVisiblePoint);
        mScreenVisibleRect.offset(mScreenVisiblePoint[0], mScreenVisiblePoint[1]);
        return mScreenVisibleRect;
    }
}