name.lakhin.eliah.projects.papacarlo.syntax.rules.ChoiceRule.scala Maven / Gradle / Ivy
/*
Copyright 2013 Ilya Lakhin (Илья Александрович Лахин)
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package name.lakhin.eliah.projects
package papacarlo.syntax.rules
import name.lakhin.eliah.projects.papacarlo.syntax.{Rule, Session}
import name.lakhin.eliah.projects.papacarlo.syntax.Result._
final case class ChoiceRule(choices: List[Rule]) extends Rule {
def apply(session: Session): Int = {
session.syntax.onRuleEnter.trigger(this, session.state)
val initialState = session.state
var bestResult = (Failed, session.state)
for (choice <- choices) {
choice(session) match {
case Successful =>
session.syntax.onRuleLeave.trigger(this, session.state, Successful)
return Successful
case Recoverable =>
if (bestResult._1 < Recoverable ||
bestResult._2.virtualPosition < session.state.virtualPosition)
bestResult = (Recoverable, session.state)
session.state = initialState
case Failed =>
if (bestResult._1 == Failed) bestResult = (Failed, session.state)
session.state = initialState
}
}
session.state = bestResult._2
session.syntax.onRuleLeave.trigger(this, session.state, bestResult._1)
bestResult._1
}
override val show = choices.map(_.showOperand(2)).mkString(" | ") -> 2
override val captures = choices.map(_.captures).reduce(_ ++ _)
override val branches = choices.map(_.branches).reduce {
(left, right) =>
var result = left
for ((key, values) <- right)
result += key -> (result.getOrElse(key, Set.empty) ++ values)
result
}
}