parser.scala

package parser

import lexical.tokens.Token
import lexical.tokens.cond.Operator._
import lexical.tokens.cond.OperatorToken
import parser.utils.Tree

/**
	* Created by wannabe on 05.01.16.
	*/
sealed trait NonTerminal {

	def evaluate(tokens: BufferedIterator[Option[Token[_]]]): Tree[Token[_]]
}

case object Expression extends NonTerminal {

	override def evaluate(tokens: BufferedIterator[Option[Token[_]]]): Tree[Token[_]] = {
		val tree: Tree[Token[_]] = new Tree(None, None, None)
		tree.l = Some(SimpleExpression.evaluate(tokens))
		tree.v = tokens.next()
		tree.r = Some(SimpleExpression.evaluate(tokens))
		tree
	}
}

case object SimpleExpression extends NonTerminal {

	override def evaluate(tokens: BufferedIterator[Option[Token[_]]]): Tree[Token[_]] = {
		val tree: Tree[Token[_]] = new Tree(None, None, None)
		if (tokens.hasNext) {
			tree.v = tokens.next()
			if (tokens.hasNext) {
				tokens.head.get match {
					case operator: OperatorToken => operator.value match {
						case PLUS | MINUS | MULTIPLY | DIVIDE =>
							tree.l = Some(new Tree[Token[_]](tree.v, None, None))
							tree.v = tokens.next()
							tree.r = Some(SimpleExpression.evaluate(tokens))
						case none =>
					}
				}
			}
		}
		tree
	}
}

object Parser {

	def parse(tokens: BufferedIterator[Option[Token[_]]]): Tree[Token[_]] = {
		Expression.evaluate(tokens)
	}
}