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Interact with your Home Assistant server using Kotlin.
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package hassemble.entities.devices

import hassemble.HomeAssistantApiClient
import hassemble.core.mapping.ObjectMapper
import hassemble.core.observing.CircularArray
import hassemble.entities.Attributes
import hassemble.entities.State
import hassemble.errorHandling.ObserverExceptionHandler
import hassemble.observability.*
import hassemble.observability.ObservableDelegateNoInitial
import hassemble.observability.Observer
import hassemble.observability.ObserverImpl
import kotlinx.serialization.json.JsonObject
import kotlin.reflect.KClass

/**
 * An Sensor holding entity state and attributes
 *
 * In Hassemble, the Sensor is the immutable representation of an entity in home assistant.
 *
 * @param S the type of the state object that represents all state values of the entity. Has to implement the [State] interface.
 * @param A the type of the attributes object that represents all attribute values of the entity. Has to implement the [Attributes] interface.
 */
class Sensor, A : Attributes>(
    private val connection: HomeAssistantApiClient,
    private val mapper: ObjectMapper,
    private val stateType: KClass<*>,
    private val attributesType: KClass<*>
) : Observable>, WithHistory>, WithAttributes {
    private val observers: MutableList>> = mutableListOf()

    /**
     * Represents the current attributes of the sensor entity.
     */
    override lateinit var attributes: A
    private val _history = CircularArray>(10)

    /**
     * Represents the current state of the sensor entity.
     */
    var measurement: S by ObservableDelegateNoInitial(this, observers, _history)

    override val history: List>
        get() = _history.toList()

    /**
     * Number of observers attached to the sensor.
     */
    val observerCount: Int
        get() = observers.size

    override fun attachObserver(observer: ObserverFunction>): Switchable =
        ObserverImpl(
            observer,
            ObserverExceptionHandler(connection.observerExceptionHandler)
        ).also { observers.add(it) }

    fun trySetActualStateFromAny(newState: JsonObject) {
        @Suppress("UNCHECKED_CAST")
        measurement = mapper.fromJson(newState, stateType) as S
        checkNotNull(measurement.value) { "State value shall not be null. Please check your State definition " }
    }

    fun trySetAttributesFromAny(newAttributes: JsonObject) {
        @Suppress("UNCHECKED_CAST")
        attributes = mapper.fromJson(newAttributes, attributesType) as A
    }
}