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package com.pitchedapps.frost.rx
import io.reactivex.Single
import io.reactivex.schedulers.Schedulers
import java.util.concurrent.TimeUnit
/**
* Created by Allan Wang on 07/01/18.
*
* Reactive flyweight to help deal with prolonged executions
* Each call will output a [Single], which may be new if none exist or the old one is invalidated,
* or reused if an old one is still valid
*
* Types:
* T input argument for caller
* C condition condition to check against for validity
* R response response within reactive output
*/
abstract class RxFlyweight<in T : Any, C : Any, R : Any> {
/**
* Given an input emit the desired response
* This will be executed in a separate thread
*/
protected abstract fun call(input: T): R
/**
* Given an input and condition, check if
* we may used cache data or if we need to make a new request
* Return [true] to use cache, [false] otherwise
*/
protected abstract fun validate(input: T, cond: C): Boolean
/**
* Given an input, create a new condition to be used
* for future requests
*/
protected abstract fun cache(input: T): C
private val conditionals = mutableMapOf<T, C>()
private val sources = mutableMapOf<T, Single<R>>()
private val lock = Any()
/**
* Entry point to give an input a receive a [Single]
* Note that the observer is not bound to any particular thread,
* as it is dependent on [createNewSource]
*/
operator fun invoke(input: T): Single<R> {
synchronized(lock) {
val source = sources[input]
// update condition and retrieve old one
val condition = conditionals.put(input, cache(input))
// check to reuse observable
if (source != null && condition != null && validate(input, condition))
return source
val newSource = createNewSource(input).cache().doOnError { sources.remove(input) }
sources[input] = newSource
return newSource
}
}
/**
* Open source creator
* Result will then be created with [Single.cache]
* If you don't have a need for cache,
* you likely won't have a need for flyweights
*/
protected open fun createNewSource(input: T): Single<R> =
Single.fromCallable { call(input) }
.timeout(15, TimeUnit.SECONDS)
.subscribeOn(Schedulers.io())
fun reset() {
synchronized(lock) {
sources.clear()
conditionals.clear()
}
}
}
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