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Kotlin Standard Library for JVM

There is a newer version: 2.1.0-Beta1

package kotlin.dom

import java.io.Closeable
import org.w3c.dom.Node
import org.w3c.dom.events.*

/**
* Turns an event handler function into an [EventListener]
*/
fun eventHandler(handler: (Event) -> Unit): EventListener {
    return EventListenerHandler(handler)
}

private class EventListenerHandler(val handler: (Event) -> Unit): EventListener {
    public override fun handleEvent(e: Event) {
        if (e != null) {
            handler(e)
        }
    }
/*
    TODO: needs KT-2507 fixed

    public override fun toString(): String? = "EventListenerHandler($handler)"
*/
}

fun mouseEventHandler(handler: (MouseEvent) -> Unit): EventListener {
    return eventHandler { e ->
        if (e is MouseEvent) {
            handler(e)
        }
    }
}

/**
 * Registers a handler on the named event
 */
public fun Node?.on(name: String, capture: Boolean, handler: (Event) -> Unit): Closeable? {
    return on(name, capture, eventHandler(handler))
}

/**
 * Registers an [EventListener] on the named event
 */
public fun Node?.on(name: String, capture: Boolean, listener: EventListener): Closeable? {
    return if (this is EventTarget) {
        addEventListener(name, listener, capture)
        CloseableEventListener(this, listener, name, capture)
    } else {
        null
    }
}

private class CloseableEventListener(val target: EventTarget, val listener: EventListener, val name: String, val capture: Boolean): Closeable {
    public override fun close() {
        target.removeEventListener(name, listener, capture)
    }

/*
    TODO: needs KT-2507 fixed

    public override fun toString(): String? = "CloseableEventListener($target, $name)"
*/
}

public fun Node?.onClick(capture: Boolean = false, handler: (MouseEvent) -> Unit): Closeable? {
    return on("click", capture, mouseEventHandler(handler))
}

public fun Node?.onDoubleClick(capture: Boolean = false, handler: (MouseEvent) -> Unit): Closeable? {
    return on("dblclick", capture, mouseEventHandler(handler))
}