/*
 * Jitsi, the OpenSource Java VoIP and Instant Messaging client.
 *
 * Distributable under LGPL license. See terms of license at gnu.org.
 */
package org.atalk.android.gui.widgets;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.*;
import android.util.AttributeSet;
import android.view.*;
import android.widget.*;

import org.atalk.android.R;

import timber.log.Timber;

/**
 * Modified version of class of the same name from android source of the music app. The widget displays a list of items.
 * User can set order of items by dragging them on the screen.<br/>
 * This <code>View</code> requires following XML attributes:<br/>
 * - <code>itemHeight</code> the height of list item<br/>
 * - <code>itemExpandedHeight</code> the height that will be set to expanded item(the one tha makes space for dragged item)<br/>
 * - <code>dragRegionStartX</code> and <code>dragRegionEndX</code> item can be grabbed when start x coordinate is between them
 *
 * @author Pawel Domas
 * @author Eng Chong Meng
 */
public class TouchInterceptor extends ListView
{
    /**
     * The view representing dragged item
     */
    private ImageView dragView;
    /**
     * The {@link android.view.WindowManager} used to display dragged view
     */
    private WindowManager windowManager;
    /**
     * Layout parameters of dragged view
     */
    private WindowManager.LayoutParams windowParams;
    /**
     * At which position is the item currently being dragged. Note that this takes in to account header items.
     */
    private int dragPos;
    /**
     * At which position was the item being dragged originally
     */
    private int srcDragPos;
    /**
     * At what x offset inside the item did the user grab it
     */
    private int dragPointX;
    /**
     * At what y offset inside the item did the user grab it
     */
    private int dragPointY;
    /**
     * The difference between screen coordinates and coordinates in this view
     */
    private int xOffset;
    /**
     * The difference between screen coordinates and coordinates in this view
     */
    private int yOffset;
    /**
     * The {@link DragListener}
     */
    private DragListener dragListener;
    /**
     * The {@link DropListener}
     */
    private DropListener dropListener;
    /**
     * Upper boundary, when reached the view is scrolled up
     */
    private int upperBound;
    /**
     * Lower boundary, when reached the view is scrolled down
     */
    private int lowerBound;
    /**
     * View's height
     */
    private int height;
    /**
     *
     */
    private Rect tempRect = new Rect();
    /**
     * The background of dragged <code>View</code>
     */
    private Bitmap dragBitmap;
    /**
     * The touch slop
     */
    private final int touchSlop;
    /**
     * Normal list item's height
     */
    private int itemHeightNormal;
    /**
     * The height of expanded item
     */
    private int itemHeightExpanded;
    /**
     * Half of the normal item's height
     */
    private int itemHeightHalf;
    /**
     * Start x coordinate of draggable area
     */
    private int dragRegionStartX;
    /**
     * End x coordinate of draggable area
     */
    private int dragRegionEndX;

    /**
     * Creates new instance of {@link TouchInterceptor}. The attribute set must contain:</br> - <code>itemHeight</code> the
     * height of list item<br/>
     * - <code>itemExpandedHeight</code> the height that will be set to expanded item<br/>
     * - <code>dragRegionStartX</code> and <code>dragRegionEndX</code> item can be grabbed when start x coordinate is between
     * them
     *
     * @param context the {@link android.content.Context}
     * @param attrs the {@link android.util.AttributeSet}
     */
    public TouchInterceptor(Context context, AttributeSet attrs)
    {
        super(context, attrs);

        touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.TouchInterceptor, 0, 0);
        try {
            itemHeightNormal = a.getDimensionPixelSize(R.styleable.TouchInterceptor_itemHeight, -1);
            itemHeightHalf = itemHeightNormal / 2;

            if (itemHeightNormal == -1)
                throw new IllegalArgumentException("Item height attribute unspecified");

            itemHeightExpanded = a.getDimensionPixelSize(R.styleable.TouchInterceptor_itemExpandedHeight, -1);

            if (itemHeightExpanded == -1)
                throw new IllegalArgumentException("Expanded item height attribute unspecified");

            dragRegionStartX = a.getDimensionPixelSize(R.styleable.TouchInterceptor_dragRegionStartX, -1);
            dragRegionEndX = a.getDimensionPixelSize(R.styleable.TouchInterceptor_dragRegionEndX, -1);

            if (dragRegionStartX == -1 || dragRegionEndX == -1)
                throw new IllegalArgumentException("Drag region attributes unspecified");
        } finally {
            a.recycle();
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev)
    {
        if (dragListener != null || dropListener != null) {
            if (!isEnabled()) {
                return true;
            }
            switch (ev.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    int x = (int) ev.getX();
                    int y = (int) ev.getY();
                    int itemnum = pointToPosition(x, y);
                    if (itemnum == AdapterView.INVALID_POSITION) {
                        break;
                    }
                    View item = getChildAt(itemnum - getFirstVisiblePosition());
                    dragPointX = x - ((item == null) ? 0 : item.getLeft());
                    dragPointY = y - ((item == null) ? 0 : item.getTop());
                    xOffset = ((int) ev.getRawX()) - x;
                    yOffset = ((int) ev.getRawY()) - y;
                    Timber.d("Dragging %s, %s sxy: %s, %s", x, y, dragRegionStartX, dragRegionEndX);

                    if (x >= dragRegionStartX && x <= dragRegionEndX) {
                        item.setDrawingCacheEnabled(true);
                        // Create a copy of the drawing cache so that it does
                        // not get recycled by the framework when the list tries
                        // to clean up memory
                        Bitmap bitmap = Bitmap.createBitmap(item.getDrawingCache());
                        startDragging(bitmap, x, y);
                        dragPos = itemnum;
                        srcDragPos = dragPos;
                        height = getHeight();
                        int touchSlop = this.touchSlop;
                        upperBound = Math.min(y - touchSlop, height / 3);
                        lowerBound = Math.max(y + touchSlop, height * 2 / 3);
                        return false;
                    }
                    stopDragging();
                    break;
            }
        }
        return super.onInterceptTouchEvent(ev);
    }

    /*
     * pointToPosition() doesn't consider invisible views, but we need to, so implement a slightly different version.
     */
    private int myPointToPosition(int x, int y)
    {

        if (y < 0) {
            // when dragging off the top of the screen, calculate position
            // by going back from a visible item
            int pos = myPointToPosition(x, y + itemHeightNormal);
            if (pos > 0) {
                return pos - 1;
            }
        }

        Rect frame = tempRect;
        final int count = getChildCount();
        for (int i = count - 1; i >= 0; i--) {
            final View child = getChildAt(i);
            child.getHitRect(frame);
            if (frame.contains(x, y)) {
                return getFirstVisiblePosition() + i;
            }
        }
        return INVALID_POSITION;
    }

    private int getItemForPosition(int y)
    {
        int adjustedy = y - dragPointY - itemHeightHalf;
        int pos = myPointToPosition(0, adjustedy);
        if (pos >= 0) {
            if (pos <= srcDragPos) {
                pos += 1;
            }
        }
        else if (adjustedy < 0) {
            // this shouldn't happen anymore now that myPointToPosition deals
            // with this situation
            pos = 0;
        }
        return pos;
    }

    private void adjustScrollBounds(int y)
    {
        if (y >= height / 3) {
            upperBound = height / 3;
        }
        if (y <= height * 2 / 3) {
            lowerBound = height * 2 / 3;
        }
    }

    /*
     * Restore size and visibility for all listitems
     */
    private void unExpandViews(boolean deletion)
    {
        int y0 = (getChildAt(0) == null) ? 0: getChildAt(0).getTop();

        for (int i = 0; ; i++) {
            View v = getChildAt(i);
            if (v == null) {
                if (deletion) {
                    // HACK force update of mItemCount
                    int position = getFirstVisiblePosition();
                     getChildAt(0);
                    setAdapter(getAdapter());
                    setSelectionFromTop(position, y0);
                    // end hack
                }
                try {
                    // force children to be recreated where needed
                    layoutChildren();
                    v = getChildAt(i);
                } catch (IllegalStateException ex) {
                    // layoutChildren throws this sometimes, presumably because
                    // we're in the process of being torn down but are still
                    // getting touch events
                }
                if (v == null) {
                    return;
                }
            }
            ViewGroup.LayoutParams params = v.getLayoutParams();
            params.height = itemHeightNormal;
            v.setLayoutParams(params);
            v.setVisibility(View.VISIBLE);
        }
    }

    /*
     * Adjust visibility and size to make it appear as though an item is being dragged around and other items are making
     * room for it: If dropping the item would result in it still being in the same place, then make the dragged
     * listitem's size normal, but make the item invisible. Otherwise, if the dragged listitem is still on screen, make
     * it as small as possible and expand the item below the insert point. If the dragged item is not on screen, only
     * expand the item below the current insertpoint.
     */
    private void doExpansion()
    {
        int childnum = dragPos - getFirstVisiblePosition();
        if (dragPos > srcDragPos) {
            childnum++;
        }
        int numheaders = getHeaderViewsCount();

        View first = getChildAt(srcDragPos - getFirstVisiblePosition());
        for (int i = 0; ; i++) {
            View vv = getChildAt(i);
            if (vv == null) {
                break;
            }

            int height = itemHeightNormal;
            int visibility = View.VISIBLE;
            if (dragPos < numheaders && i == numheaders) {
                // dragging on top of the header item, so adjust the item below
                // instead
                if (vv.equals(first)) {
                    visibility = View.INVISIBLE;
                }
                else {
                    height = itemHeightExpanded;
                }
            }
            else if (vv.equals(first)) {
                // processing the item that is being dragged
                if (dragPos == srcDragPos || getPositionForView(vv) == getCount() - 1) {
                    // hovering over the original location
                    visibility = View.INVISIBLE;
                }
                else {
                    // not hovering over it
                    // Ideally the item would be completely gone, but neither
                    // setting its size to 0 nor settings visibility to GONE
                    // has the desired effect.
                    height = 1;
                }
            }
            else if (i == childnum) {
                if (dragPos >= numheaders && dragPos < getCount() - 1) {
                    height = itemHeightExpanded;
                }
            }
            ViewGroup.LayoutParams params = vv.getLayoutParams();
            params.height = height;
            vv.setLayoutParams(params);
            vv.setVisibility(visibility);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev)
    {
        if ((dragListener != null || dropListener != null) && dragView != null) {
            int action = ev.getAction();
            switch (action) {
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_CANCEL:
                    Rect r = tempRect;
                    dragView.getDrawingRect(r);
                    stopDragging();
                    if (dropListener != null && dragPos >= 0 && dragPos < getCount()) {
                        dropListener.drop(srcDragPos, dragPos);
                    }
                    unExpandViews(false);
                    break;

                case MotionEvent.ACTION_DOWN:
                case MotionEvent.ACTION_MOVE:
                    int x = (int) ev.getX();
                    int y = (int) ev.getY();
                    dragView(x, y);
                    int itemnum = getItemForPosition(y);
                    if (itemnum >= 0) {
                        if (action == MotionEvent.ACTION_DOWN || itemnum != dragPos) {
                            if (dragListener != null) {
                                dragListener.drag(dragPos, itemnum);
                            }
                            dragPos = itemnum;
                            doExpansion();
                        }
                        int speed = 0;
                        adjustScrollBounds(y);
                        if (y > lowerBound) {
                            // scroll the list up a bit
                            if (getLastVisiblePosition() < getCount() - 1) {
                                speed = y > (height + lowerBound) / 2 ? 16 : 4;
                            }
                            else {
                                speed = 1;
                            }
                        }
                        else if (y < upperBound) {
                            // scroll the list down a bit
                            speed = y < upperBound / 2 ? -16 : -4;

                            int y0 = (getChildAt(0) == null) ? 0: getChildAt(0).getTop();
                            if ((getFirstVisiblePosition() == 0) && (y0 >= getPaddingTop())) {
                                // if we're already at the top, don't try to
                                // scroll, because it causes the framework to
                                // do some extra drawing that messes up our animation
                                speed = 0;
                            }
                        }
                        if (speed != 0) {
                            smoothScrollBy(speed, 30);
                        }
                    }
                    break;
            }
            return true;
        }
        return super.onTouchEvent(ev);
    }

    private void startDragging(Bitmap bm, int x, int y)
    {
        stopDragging();

        windowParams = new WindowManager.LayoutParams();
        windowParams.gravity = Gravity.TOP | Gravity.LEFT;
        windowParams.x = xOffset;
        windowParams.y = y - dragPointY + yOffset;

        windowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
        windowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
        windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;
        windowParams.format = PixelFormat.TRANSLUCENT;
        windowParams.windowAnimations = 0;

        Context context = getContext();
        ImageView v = new ImageView(context);
        int backGroundColor = context.getResources().getColor(R.color.blue);
        v.setBackgroundColor(backGroundColor);
        v.setPadding(0, 0, 0, 0);
        v.setImageBitmap(bm);
        dragBitmap = bm;

        windowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
        windowManager.addView(v, windowParams);
        dragView = v;
    }

    private void dragView(int x, int y)
    {
        windowParams.x = xOffset;
        windowParams.y = y - dragPointY + yOffset;
        windowManager.updateViewLayout(dragView, windowParams);
    }

    private void stopDragging()
    {
        if (dragView != null) {
            dragView.setVisibility(GONE);
            WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
            wm.removeView(dragView);
            dragView.setImageDrawable(null);
            dragView = null;
        }
        if (dragBitmap != null) {
            dragBitmap.recycle();
            dragBitmap = null;
        }
    }

    /**
     * Sets the {@link DragListener} that will be notified about drag events.
     *
     * @param l the drag listener
     */
    public void setDragListener(DragListener l)
    {
        dragListener = l;
    }

    /**
     * Sets the {@link DropListener} that will be notified about drop events.
     *
     * @param l the drop listener
     */
    public void setDropListener(DropListener l)
    {
        dropListener = l;
    }

    /**
     * Drag events occur when currently dragged item moves around the screen over other items.
     */
    public interface DragListener
    {
        /**
         * Fired when item is dragged over other list item.
         *
         * @param from the position of dragged item
         * @param to the position of currently selected item
         */
        void drag(int from, int to);
    }

    /**
     * Drop events occur when the dragged item is finally dropped.
     */
    public interface DropListener
    {
        /**
         * Fired when dragged item is dropped on other list item.
         *
         * @param from the position of source item
         * @param to the destination drop position
         */
        void drop(int from, int to);
    }
}
