commonMain.org.brightify.hyperdrive.property.impl.BindingObservableProperty.kt Maven / Gradle / Ivy

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Hyperdrive implementation that's needed for observations and such

There is a newer version: 0.1.159

package org.brightify.hyperdrive.property.impl

import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.collect
import org.brightify.hyperdrive.CancellationToken
import org.brightify.hyperdrive.Lifecycle
import org.brightify.hyperdrive.property.MutableObservableProperty
import org.brightify.hyperdrive.property.ObservableProperty
import org.brightify.hyperdrive.property.defaultEqualityPolicy

internal class BindingObservableProperty(
    initialValue: T,
    private val boundFlow: Flow,
    lifecycle: Lifecycle,
    private val equalityPolicy: ObservableProperty.EqualityPolicy = defaultEqualityPolicy(),
    private val readMapping: (U) -> T,
    private val setter: (T) -> Unit,
): MutableObservableProperty {

    private var valueStorage: T = initialValue
    override var value: T
        get() = valueStorage
        set(newValue) {
            if (equalityPolicy.isEqual(value, newValue)) { return }
            listeners.runNotifyingListeners(newValue) {
                valueStorage = it
                setter(it)
            }
        }

    private val listeners = ValueChangeListenerHandler(this)

    init {
        lifecycle.whileAttached {
            // TODO: We want to ignore changes we made. Equality policy should be enough, but we better do it smarter.
            boundFlow.collect { newValue ->
                val mappedNewValue = readMapping(newValue)
                if (equalityPolicy.isEqual(value, mappedNewValue)) { return@collect }
                listeners.runNotifyingListeners(mappedNewValue) {
                    valueStorage = it
                }
            }
        }
    }

    override fun addListener(listener: ObservableProperty.Listener): CancellationToken = listeners.addListener(listener)

    override fun removeListener(listener: ObservableProperty.Listener) = listeners.removeListener(listener)
}