/*
 * Copyright (c) 2020 New Vector Ltd
 *
 * 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 im.vector.app.core.utils

import java.util.concurrent.atomic.AtomicBoolean

/**
 * Use this container to read a value only once
 */
class ReadOnce<T>(
        private val value: T
) {
    private val valueHasBeenRead = AtomicBoolean(false)

    fun get(): T? {
        return if (valueHasBeenRead.getAndSet(true)) {
            null
        } else {
            value
        }
    }
}

/**
 * Only the first call to isTrue() will return true
 */
class ReadOnceTrue {
    private val readOnce = ReadOnce(true)

    fun isTrue() = readOnce.get() == true
}
