/*
* 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 android.support.v7.widget;
import java.util.List;
import android.support.v7.widget.AdapterHelper.UpdateOp;
import static android.support.v7.widget.AdapterHelper.UpdateOp.ADD;
import static android.support.v7.widget.AdapterHelper.UpdateOp.MOVE;
import static android.support.v7.widget.AdapterHelper.UpdateOp.REMOVE;
import static android.support.v7.widget.AdapterHelper.UpdateOp.UPDATE;
class OpReorderer {
final Callback mCallback;
public OpReorderer(Callback callback) {
mCallback = callback;
}
void reorderOps(List<UpdateOp> ops) {
// since move operations breaks continuity, their effects on ADD/RM are hard to handle.
// we push them to the end of the list so that they can be handled easily.
int badMove;
while ((badMove = getLastMoveOutOfOrder(ops)) != -1) {
swapMoveOp(ops, badMove, badMove + 1);
}
}
private void swapMoveOp(List<UpdateOp> list, int badMove, int next) {
final UpdateOp moveOp = list.get(badMove);
final UpdateOp nextOp = list.get(next);
switch (nextOp.cmd) {
case REMOVE:
swapMoveRemove(list, badMove, moveOp, next, nextOp);
break;
case ADD:
swapMoveAdd(list, badMove, moveOp, next, nextOp);
break;
case UPDATE:
swapMoveUpdate(list, badMove, moveOp, next, nextOp);
break;
}
}
void swapMoveRemove(List<UpdateOp> list, int movePos, UpdateOp moveOp,
int removePos, UpdateOp removeOp) {
UpdateOp extraRm = null;
// check if move is nulled out by remove
boolean revertedMove = false;
final boolean moveIsBackwards;
if (moveOp.positionStart < moveOp.itemCount) {
moveIsBackwards = false;
if (removeOp.positionStart == moveOp.positionStart
&& removeOp.itemCount == moveOp.itemCount - moveOp.positionStart) {
revertedMove = true;
}
} else {
moveIsBackwards = true;
if (removeOp.positionStart == moveOp.itemCount + 1 &&
removeOp.itemCount == moveOp.positionStart - moveOp.itemCount) {
revertedMove = true;
}
}
// going in reverse, first revert the effect of add
if (moveOp.itemCount < removeOp.positionStart) {
removeOp.positionStart--;
} else if (moveOp.itemCount < removeOp.positionStart + removeOp.itemCount) {
// move is removed.
removeOp.itemCount --;
moveOp.cmd = REMOVE;
moveOp.itemCount = 1;
if (removeOp.itemCount == 0) {
list.remove(removePos);
mCallback.recycleUpdateOp(removeOp);
}
// no need to swap, it is already a remove
return;
}
// now affect of add is consumed. now apply effect of first remove
if (moveOp.positionStart <= removeOp.positionStart) {
removeOp.positionStart++;
} else if (moveOp.positionStart < removeOp.positionStart + removeOp.itemCount) {
final int remaining = removeOp.positionStart + removeOp.itemCount
- moveOp.positionStart;
extraRm = mCallback.obtainUpdateOp(REMOVE, moveOp.positionStart + 1, remaining, null);
removeOp.itemCount = moveOp.positionStart - removeOp.positionStart;
}
// if effects of move is reverted by remove, we are done.
if (revertedMove) {
list.set(movePos, removeOp);
list.remove(removePos);
mCallback.recycleUpdateOp(moveOp);
return;
}
// now find out the new locations for move actions
if (moveIsBackwards) {
if (extraRm != null) {
if (moveOp.positionStart > extraRm.positionStart) {
moveOp.positionStart -= extraRm.itemCount;
}
if (moveOp.itemCount > extraRm.positionStart) {
moveOp.itemCount -= extraRm.itemCount;
}
}
if (moveOp.positionStart > removeOp.positionStart) {
moveOp.positionStart -= removeOp.itemCount;
}
if (moveOp.itemCount > removeOp.positionStart) {
moveOp.itemCount -= removeOp.itemCount;
}
} else {
if (extraRm != null) {
if (moveOp.positionStart >= extraRm.positionStart) {
moveOp.positionStart -= extraRm.itemCount;
}
if (moveOp.itemCount >= extraRm.positionStart) {
moveOp.itemCount -= extraRm.itemCount;
}
}
if (moveOp.positionStart >= removeOp.positionStart) {
moveOp.positionStart -= removeOp.itemCount;
}
if (moveOp.itemCount >= removeOp.positionStart) {
moveOp.itemCount -= removeOp.itemCount;
}
}
list.set(movePos, removeOp);
if (moveOp.positionStart != moveOp.itemCount) {
list.set(removePos, moveOp);
} else {
list.remove(removePos);
}
if (extraRm != null) {
list.add(movePos, extraRm);
}
}
private void swapMoveAdd(List<UpdateOp> list, int move, UpdateOp moveOp, int add,
UpdateOp addOp) {
int offset = 0;
// going in reverse, first revert the effect of add
if (moveOp.itemCount < addOp.positionStart) {
offset--;
}
if (moveOp.positionStart < addOp.positionStart) {
offset++;
}
if (addOp.positionStart <= moveOp.positionStart) {
moveOp.positionStart += addOp.itemCount;
}
if (addOp.positionStart <= moveOp.itemCount) {
moveOp.itemCount += addOp.itemCount;
}
addOp.positionStart += offset;
list.set(move, addOp);
list.set(add, moveOp);
}
void swapMoveUpdate(List<UpdateOp> list, int move, UpdateOp moveOp, int update,
UpdateOp updateOp) {
UpdateOp extraUp1 = null;
UpdateOp extraUp2 = null;
// going in reverse, first revert the effect of add
if (moveOp.itemCount < updateOp.positionStart) {
updateOp.positionStart--;
} else if (moveOp.itemCount < updateOp.positionStart + updateOp.itemCount) {
// moved item is updated. add an update for it
updateOp.itemCount--;
extraUp1 = mCallback.obtainUpdateOp(UPDATE, moveOp.positionStart, 1, updateOp.payload);
}
// now affect of add is consumed. now apply effect of first remove
if (moveOp.positionStart <= updateOp.positionStart) {
updateOp.positionStart++;
} else if (moveOp.positionStart < updateOp.positionStart + updateOp.itemCount) {
final int remaining = updateOp.positionStart + updateOp.itemCount
- moveOp.positionStart;
extraUp2 = mCallback.obtainUpdateOp(UPDATE, moveOp.positionStart + 1, remaining,
updateOp.payload);
updateOp.itemCount -= remaining;
}
list.set(update, moveOp);
if (updateOp.itemCount > 0) {
list.set(move, updateOp);
} else {
list.remove(move);
mCallback.recycleUpdateOp(updateOp);
}
if (extraUp1 != null) {
list.add(move, extraUp1);
}
if (extraUp2 != null) {
list.add(move, extraUp2);
}
}
private int getLastMoveOutOfOrder(List<UpdateOp> list) {
boolean foundNonMove = false;
for (int i = list.size() - 1; i >= 0; i--) {
final UpdateOp op1 = list.get(i);
if (op1.cmd == MOVE) {
if (foundNonMove) {
return i;
}
} else {
foundNonMove = true;
}
}
return -1;
}
static interface Callback {
UpdateOp obtainUpdateOp(int cmd, int startPosition, int itemCount, Object payload);
void recycleUpdateOp(UpdateOp op);
}
}