/*
 * Copyright (C) 2014 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.settings;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.PixelFormat;
import android.graphics.Rect;

import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;

/**
 * A draggable/sortable listview
 */
public class DraggableSortListView extends ListView {

    public interface DragListener {
        void drag(int from, int to);
    }

    public interface DropListener {
        void drop(int from, int to);
    }

    private ImageView mDragView;
    private WindowManager mWindowManager;
    private WindowManager.LayoutParams mWindowParams;
    private int mDragPos;
    private int mFirstDragPos;
    private int mDragPoint;
    private int mCoordOffset;
    private DragListener mDragListener;
    private DropListener mDropListener;
    private int mUpperBound;
    private int mLowerBound;
    private int mHeight;
    private Rect mTempRect = new Rect();
    private Bitmap mDragBitmap;
    private final int mTouchSlop;
    private int mItemHeight;

    public DraggableSortListView(Context context) {
        super(context);
        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if ((mDragListener != null || mDropListener != null) && getChildCount() > 1) {
            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;
                    }
                    ViewGroup item = (ViewGroup) getChildAt(itemnum - getFirstVisiblePosition());
                    mItemHeight = item.getHeight();
                    mDragPoint = y - item.getTop();
                    mCoordOffset = ((int) ev.getRawY()) - y;
                    View dragger = item.findViewById(com.android.internal.R.id.icon);

                    // The dragger icon itself is quite small, so pretend the
                    // touch area is bigger
                    int x1 = item.getLeft() + dragger.getLeft() - (dragger.getWidth() / 2);
                    int x2 = item.getLeft() + dragger.getRight() + (dragger.getWidth() / 2);
                    if (x > x1 && x < x2) {
                        // Fix x position while dragging
                        int[] itemPos = new int[2];
                        item.getLocationOnScreen(itemPos);

                        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, itemPos[0], y);
                        mDragPos = itemnum;
                        mFirstDragPos = mDragPos;
                        mHeight = getHeight();
                        int touchSlop = mTouchSlop;
                        mUpperBound = Math.min(y - touchSlop, mHeight / 3);
                        mLowerBound = Math.max(y + touchSlop, mHeight * 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 + mItemHeight);
            if (pos > 0) {
                return pos - 1;
            }
        }

        Rect frame = mTempRect;
        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 - mDragPoint - (mItemHeight / 2);
        int pos = myPointToPosition(0, adjustedy);
        if (pos >= 0) {
            if (pos <= mFirstDragPos) {
                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 >= mHeight / 3) {
            mUpperBound = mHeight / 3;
        }
        if (y <= mHeight * 2 / 3) {
            mLowerBound = mHeight * 2 / 3;
        }
    }

    /*
     * Restore size and visibility for all listitems
     */
    private void unExpandViews(boolean deletion) {
        for (int i = 0;; i++) {
            View v = getChildAt(i);
            if (v == null) {
                if (deletion) {
                    // HACK force update of mItemCount
                    int position = getFirstVisiblePosition();
                    int y = getChildAt(0).getTop();
                    setAdapter(getAdapter());
                    setSelectionFromTop(position, y);
                    // end hack
                }
                layoutChildren(); // force children to be recreated where needed
                v = getChildAt(i);
                if (v == null) {
                    break;
                }
            }
            ViewGroup.LayoutParams params = v.getLayoutParams();
            params.height = mItemHeight;
            v.setLayoutParams(params);
            v.setVisibility(View.VISIBLE);
            // Reset the drawing cache, the positions might have changed.
            // We don't want the cache to be wrong.
            v.setDrawingCacheEnabled(false);
        }
    }

    /*
     * 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 = mDragPos - getFirstVisiblePosition();
        if (mDragPos > mFirstDragPos) {
            childnum++;
        }

        View first = getChildAt(mFirstDragPos - getFirstVisiblePosition());

        for (int i = 0;; i++) {
            View vv = getChildAt(i);
            if (vv == null) {
                break;
            }
            int height = mItemHeight;
            int visibility = View.VISIBLE;
            if (vv.equals(first)) {
                // processing the item that is being dragged
                if (mDragPos == mFirstDragPos) {
                    // hovering over the original location
                    visibility = View.INVISIBLE;
                } else {
                    // not hovering over it
                    height = 1;
                }
            } else if (i == childnum) {
                if (mDragPos < getCount() - 1) {
                    height = mItemHeight * 2;
                }
            }
            ViewGroup.LayoutParams params = vv.getLayoutParams();
            params.height = height;
            vv.setLayoutParams(params);
            vv.setVisibility(visibility);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if ((mDragListener != null || mDropListener != null) && mDragView != null) {
            int action = ev.getAction();
            switch (action) {
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_CANCEL:
                    Rect r = mTempRect;
                    mDragView.getDrawingRect(r);
                    stopDragging();
                    if (mDropListener != null && mDragPos >= 0 && mDragPos < getCount()) {
                        mDropListener.drop(mFirstDragPos, mDragPos);
                    }
                    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 != mDragPos) {
                            if (mDragListener != null) {
                                mDragListener.drag(mDragPos, itemnum);
                            }
                            mDragPos = itemnum;
                            doExpansion();
                        }
                        int speed = 0;
                        adjustScrollBounds(y);
                        if (y > mLowerBound) {
                            // scroll the list up a bit
                            speed = y > (mHeight + mLowerBound) / 2 ? 16 : 4;
                        } else if (y < mUpperBound) {
                            // scroll the list down a bit
                            speed = y < mUpperBound / 2 ? -16 : -4;
                        }
                        if (speed != 0) {
                            int ref = pointToPosition(0, mHeight / 2);
                            if (ref == AdapterView.INVALID_POSITION) {
                                // we hit a divider or an invisible view, check
                                // somewhere else
                                ref = pointToPosition(0, mHeight / 2 + getDividerHeight() + 64);
                            }
                            View v = getChildAt(ref - getFirstVisiblePosition());
                            if (v != null) {
                                int pos = v.getTop();
                                setSelectionFromTop(ref, pos - speed);
                            }
                        }
                    }
                    break;
            }
            return true;
        }
        return super.onTouchEvent(ev);
    }

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

        mWindowParams = new WindowManager.LayoutParams();
        mWindowParams.gravity = Gravity.TOP | Gravity.LEFT;
        mWindowParams.x = x;
        mWindowParams.y = y - mDragPoint + mCoordOffset;

        mWindowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
        mWindowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
        mWindowParams.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;
        mWindowParams.format = PixelFormat.TRANSLUCENT;
        mWindowParams.windowAnimations = 0;

        Context context = getContext();
        ImageView v = new ImageView(context);
        int backGroundColor = context.getResources().getColor(R.color.theme_accent);
        v.setAlpha((float) 0.7);
        v.setBackgroundColor(backGroundColor);
        v.setImageBitmap(bm);
        mDragBitmap = bm;

        mWindowManager = (WindowManager) context.getSystemService("window");
        mWindowManager.addView(v, mWindowParams);
        mDragView = v;
    }

    private void dragView(int x, int y) {
        mWindowParams.y = y - mDragPoint + mCoordOffset;
        mWindowManager.updateViewLayout(mDragView, mWindowParams);
    }

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

    public void setDragListener(DragListener l) {
        mDragListener = l;
    }

    public void setDropListener(DropListener l) {
        mDropListener = l;
    }
}