We-Eat/client/src/main/scala/com/weEat/modules/SearchBar.scala

package com.weEat.modules

import org.scalajs.dom.raw.Event
import scala.concurrent.duration._
import scala.concurrent.{ExecutionContext,Future,Promise}
import scala.scalajs.js.timers.{clearTimeout, setTimeout}
import mhtml.Rx
import mhtml.future.syntax._
import scala.util.Try
import cats.implicits._
import mhtml.implicits.cats._
import cats.Traverse._
import scala.xml.{Node,Elem,UnprefixedAttribute}
import com.weEat.modules._
import com.weEat.util.MHtmlHelpers._

case class SearchBar[T](
  searchFn: (String) => Future[T],
  minLength: Int = 3,
  delay: FiniteDuration = 500 milliseconds
)(implicit val ec: ExecutionContext = ExecutionContext.global) extends Module {

  // TODO: Refactor these out into utility classes
  def setTimeoutResult[T](delay: FiniteDuration)(body: => T) = {
    val promise = Promise[T]()
    setTimeout(delay) {
      promise.success(body)
    }
    promise.future
  }
  implicit class RxRxFlattener[T](outer: Rx[Rx[T]]) {
    def flatten = outer.flatMap(identity)
  }


  private val (_render, _inputTerm) =
    (<input type="text" class="form-control input-sm" />).value()
  val render = _render

  val searchTerm = _inputTerm.map[Option[String]](Some(_))
    .keepIf(_.map(_.length >= minLength).getOrElse(false))(None)
    .dropRepeats.impure.sharing

  // Nested futures give us a hellish type web to unweave
  val result: Rx[Option[Try[T]]] = searchTerm.flatMap({ term =>
    term.map({ termAtStart =>
      setTimeoutResult(delay) {
        searchTerm.map({ termAfterDelay =>
          if (Some(termAtStart) == termAfterDelay)
            searchFn(termAtStart).toRx
          else
            Rx(None)
        }).flatten
      }.toRx.map(
        _.map(
          _.sequence[Rx, Option[Try[T]]].map(
            _.flatSequence[Option, T]
          )
        )
      ).map(_.flatSequence[Rx, Try[T]]).flatten
    }).flatSequence[Rx, Try[T]]
  }).impure.sharing
}