/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

package com.sun.glass.ui.monocle;

class LookaheadTouchFilter implements TouchFilter {

    private TouchState previousState = new TouchState();
    private TouchState tmpState = new TouchState();
    private boolean assignIDs;

    private enum FilterState {
        
No events processed yet /** No events processed yet */
        CLEAN,
        
previousState contains an event that must be sent as is. This will
happen when an event is the first to be processed on this pulse, or
"Substantially different" means that two events differ in the number
of touch points or in the IDs assigned to those points.
/**
         * previousState contains an event that must be sent as is. This will
         * happen when an event is the first to be processed on this pulse, or
         * "Substantially different" means that two events differ in the number
         * of touch points or in the IDs assigned to those points.
         */
        PENDING_UNMODIFIABLE,
        
previousState contains an event that we are allowed to change before
sending. An event can be modified if it is substantially different
neither from the event that preceded it nor from the event that
follows it.
/**
         * previousState contains an event that we are allowed to change before
         * sending. An event can be modified if it is substantially different
         * neither from the event that preceded it nor from the event that
         * follows it.
         */
        PENDING_MODIFIABLE
    }

    private FilterState filterState = FilterState.CLEAN;

    
Creates a new LookaheadTouchFilter
Params:
assignIDs – Sets whether or not we are asking the touch pipeline to
                 assign touch point IDs/**
     * Creates a new LookaheadTouchFilter
     *
     * @param assignIDs Sets whether or not we are asking the touch pipeline to
     *                  assign touch point IDs
     */
    LookaheadTouchFilter(boolean assignIDs) {
        this.assignIDs = assignIDs;
    }

    @Override
    public boolean filter(TouchState state) {
        state.sortPointsByID();
        switch (filterState) {
            case CLEAN:
                state.copyTo(previousState);
                filterState = FilterState.PENDING_UNMODIFIABLE;
                return true;
            case PENDING_UNMODIFIABLE:
                // send the previous state and hold the new state as pending
                state.copyTo(tmpState);
                previousState.copyTo(state);
                tmpState.copyTo(previousState);
                if (state.canBeFoldedWith(previousState, assignIDs)) {
                    filterState = FilterState.PENDING_MODIFIABLE;
                }
                return false;
            case PENDING_MODIFIABLE:
                if (state.canBeFoldedWith(previousState, assignIDs)) {
                    state.copyTo(previousState);
                    return true;
                } else {
                    // send the previous state and hold the new state as pending
                    state.copyTo(tmpState);
                    previousState.copyTo(state);
                    tmpState.copyTo(previousState);
                    filterState = FilterState.PENDING_UNMODIFIABLE;
                    return false;
                }
            default:
                return false;
        }
    }

    @Override
    public boolean flush(TouchState state) {
        switch (filterState) {
            case PENDING_MODIFIABLE:
            case PENDING_UNMODIFIABLE:
                previousState.copyTo(state);
                filterState = FilterState.CLEAN;
                return true;
            default:
                return false;
        }
    }

    @Override
    public int getPriority() {
        return PRIORITY_PRE_ID + 1;
    }

    @Override
    public String toString() {
        return "Lookahead[previousState="
                + previousState
                + ",filterState=" + filterState
                + "]";
    }

}