Sleeper.scala

package peterlavalle.pg3

import peterlavalle.{E, *}

/**
 *
 * @param create some function to open a resource
 * @tparam I the full key needed to open a resource (file or socket, parapmeters, etc)
 * @tparam V the resource handle and any key or whatever that's needed
 */
class Sleeper[I, V](create: I => E[V]) {

	/**
	 * an empty item, which uses this create but doesn't have anything open yet
	 */
	object Initial extends Dreamer {
		override def map[O](f: List[V] => E[O]): E[O] = f(Nil)
	}

	/**
	 * an instance with some count of open things
	 */
	trait Dreamer {

		/**
		 * open something and return the next state and the created handle
		 *
		 * @param i the key/parameters to open the resource
		 * @return the next state and the handle to whatever we made
		 */
		def bind(i: I): E[(Dreamer, V)] =
			for {
				v <- create(i)
			} yield {
				Dream(v, this) -> v
			}

		/**
		 * do something with all opened resource handles (FIFO)
		 *
		 * @param f the function to build some result
		 * @tparam O
		 * @return the result we built - possibly a runnable instance of the AI that ties together all the resource handles
		 */
		def map[O](f: List[V] => E[O]): E[O]

		private class Dream(v: V, from: Dreamer) extends Dreamer {
			override def map[O](f: List[V] => E[O]): E[O] =
				for {
					l <- from
				} yield {
					f(l :+ v)
				}
		}
	}
}