BayernMessenger/app/src/main/java/im/vector/riotredesign/core/epoxy/KotlinEpoxyHolder.kt

/*
 *
 *  * Copyright 2019 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.riotredesign.core.epoxy

import android.view.View
import com.airbnb.epoxy.EpoxyHolder
import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty

/**
 * A pattern for easier view binding with an [EpoxyHolder]
 *
 * See [SampleKotlinModelWithHolder] for a usage example.
 */
abstract class KotlinEpoxyHolder : EpoxyHolder() {
    private lateinit var view: View

    override fun bindView(itemView: View) {
        view = itemView
    }

    protected fun <V : View> bind(id: Int): ReadOnlyProperty<KotlinEpoxyHolder, V> =
            Lazy { holder: KotlinEpoxyHolder, prop ->
                holder.view.findViewById(id) as V?
                ?: throw IllegalStateException("View ID $id for '${prop.name}' not found.")
            }

    /**
     * Taken from Kotterknife.
     * https://github.com/JakeWharton/kotterknife
     */
    private class Lazy<V>(
            private val initializer: (KotlinEpoxyHolder, KProperty<*>) -> V
    ) : ReadOnlyProperty<KotlinEpoxyHolder, V> {
        private object EMPTY

        private var value: Any? = EMPTY

        override fun getValue(thisRef: KotlinEpoxyHolder, property: KProperty<*>): V {
            if (value == EMPTY) {
                value = initializer(thisRef, property)
            }
            @Suppress("UNCHECKED_CAST")
            return value as V
        }
    }
}