/*
 * Copyright 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.riotx.core.animations

import com.google.android.material.appbar.AppBarLayout
import com.google.android.material.appbar.AppBarLayout.OnOffsetChangedListener
import kotlin.math.abs

abstract class AppBarStateChangeListener : OnOffsetChangedListener {

    enum class State {
        EXPANDED, COLLAPSED, IDLE
    }

    var currentState = State.IDLE
        private set

    override fun onOffsetChanged(appBarLayout: AppBarLayout, i: Int) {
        currentState = if (i == 0) {
            if (currentState != State.EXPANDED) {
                onStateChanged(appBarLayout, State.EXPANDED)
            }
            State.EXPANDED
        } else if (abs(i) >= appBarLayout.totalScrollRange) {
            if (currentState != State.COLLAPSED) {
                onStateChanged(appBarLayout, State.COLLAPSED)
            }
            State.COLLAPSED
        } else {
            if (currentState != State.IDLE) {
                onStateChanged(appBarLayout, State.IDLE)
            }
            State.IDLE
        }
    }

    abstract fun onStateChanged(appBarLayout: AppBarLayout, state: State)
}
