commonMain.collections.LazyMap.kt Maven / Gradle / Ivy

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/**
 * Copyright (C) 2020 Dr. David H. Akehurst (http://dr.david.h.akehurst.net)
 *
 * 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 net.akehurst.language.collections

internal fun  lazyMap(accessor: (K) -> V) = LazyMap(accessor)

internal class LazyMap(val accessor: (K) -> V) : Map {

    val map = mutableMapOf()

    override operator fun get(key:K): V? {
        return if(map.containsKey(key)) {
            map.get(key)
        } else {
            val v = accessor.invoke(key)
            map[key] = v
            v
        }
    }

    override val entries: Set>
        get() = map.entries

    override val keys: Set
        get() = map.keys

    override val size: Int
        get() = map.size

    override val values: Collection
        get() = map.values

    override fun containsKey(key: K): Boolean {
        return map.containsKey(
            key
        )
    }

    override fun containsValue(value: V): Boolean {
        return map.containsValue(value)
    }

    override fun isEmpty(): Boolean {
        return map.isEmpty()
    }

}