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package ca.allanwang.kau.kotlin
import ca.allanwang.kau.logging.KL
import java.util.concurrent.Executors
import java.util.concurrent.TimeUnit
/**
* Created by Allan Wang on 2017-08-05.
*
* Thread safe function wrapper to allow for debouncing
* With reference to <a href="https://stackoverflow.com/a/20978973/4407321">Stack Overflow</a>
*/
/**
* The debouncer base
* Implements everything except for the callback,
* as the number of variables is different between implementations
* You may still use this without extending it, but you'll have to pass a callback each time
*/
open class Debouncer(var interval: Long) {
private val sched = Executors.newScheduledThreadPool(1)
private var task: DebounceTask? = null
/**
* Generic invocation to pass a callback to the new task
* Pass a new callback for the task
* If another task is pending, it will be invalidated
*/
operator fun invoke(callback: () -> Unit) {
synchronized(this) {
task?.invalidate()
val newTask = DebounceTask(callback)
KL.v { "Debouncer task created: $newTask in $this" }
sched.schedule(newTask, interval, TimeUnit.MILLISECONDS)
task = newTask
}
}
/**
* Call to cancel all pending requests and shutdown the thread pool
* The debouncer cannot be used after this
*/
fun terminate() {
task?.invalidate()
task = null
sched.shutdownNow()
}
/**
* Invalidate any pending tasks
*/
fun cancel() {
synchronized(this) {
if (task != null) KL.v { "Debouncer cancelled for $task in $this" }
task?.invalidate()
task = null
}
}
}
/*
* Helper extensions for functions with 0 to 3 arguments
*/
/**
* The debounced task
* Holds a callback to execute if the time has come and it is still valid
* All methods can be viewed as synchronous as the invocation is synchronous
*/
private class DebounceTask(inline val callback: () -> Unit) : Runnable {
private var valid = true
fun invalidate() {
valid = false
}
override fun run() {
if (!valid) return
valid = false
KL.v { "Debouncer task executed $this" }
try {
callback()
} catch (e: Exception) {
KL.e(e) { "DebouncerTask exception" }
}
}
}
/**
* A zero input debouncer
*/
class Debouncer0 internal constructor(interval: Long, val callback: () -> Unit) : Debouncer(interval) {
operator fun invoke() = invoke(callback)
}
fun debounce(interval: Long, callback: () -> Unit) = Debouncer0(interval, callback)
fun (() -> Unit).debounce(interval: Long) = debounce(interval, this)
/**
* A one argument input debouncer
*/
class Debouncer1<T> internal constructor(interval: Long, val callback: (T) -> Unit) : Debouncer(interval) {
operator fun invoke(key: T) = invoke { callback(key) }
}
fun <T> debounce(interval: Long, callback: (T) -> Unit) = Debouncer1(interval, callback)
fun <T> ((T) -> Unit).debounce(interval: Long) = debounce(interval, this)
/**
* A two argument input debouncer
*/
class Debouncer2<T, V> internal constructor(interval: Long, val callback: (T, V) -> Unit) : Debouncer(interval) {
operator fun invoke(arg0: T, arg1: V) = invoke { callback(arg0, arg1) }
}
fun <T, V> debounce(interval: Long, callback: (T, V) -> Unit) = Debouncer2(interval, callback)
fun <T, V> ((T, V) -> Unit).debounce(interval: Long) = debounce(interval, this)
/**
* A three argument input debouncer
*/
class Debouncer3<T, U, V> internal constructor(interval: Long, val callback: (T, U, V) -> Unit) : Debouncer(interval) {
operator fun invoke(arg0: T, arg1: U, arg2: V) = invoke { callback(arg0, arg1, arg2) }
}
fun <T, U, V> debounce(interval: Long, callback: ((T, U, V) -> Unit)) = Debouncer3(interval, callback)
fun <T, U, V> ((T, U, V) -> Unit).debounce(interval: Long) = debounce(interval, this)
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