Add boolean literals to expression parser

app/Cfnpp/Expression/Expression.php

@@ -20,6 +20,7 @@ class Expression
 	 * @var string[]
 	 */
 	public const TOKEN_TYPES = [
+		Token\BooleanLiteral::class,
 		Token\NumericLiteral::class,
 		Token\OperatorUnary::class,
 		Token\OperatorBinary::class,

app/Cfnpp/Expression/Token/BooleanLiteral.php

@@ -0,0 +1,75 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Cfnpp\Expression\Token;
+
+use App\Cfnpp\Expression\Token;
+use App\Cfnpp\Expression\TokenLiteral;
+
+/**
+ * A boolean literal (true/false).
+ *
+ * @author Adam Pippin <hello@adampippin.ca>
+ */
+class BooleanLiteral extends TokenLiteral
+{
+	/**
+	 * Value of this literal.
+	 * @var bool
+	 */
+	protected $value;
+
+	/**
+	 * New boolean literal.
+	 *
+	 * @param bool $value
+	 */
+	public function __construct(bool $value)
+	{
+		$this->value = $value;
+	}
+
+	/**
+	 * Get the value of this literal.
+	 *
+	 * @return bool
+	 */
+	public function getValue(): bool
+	{
+		return $this->value;
+	}
+
+	public static function isToken(string $stream): bool
+	{
+		return
+			(strlen($stream) >= 4 && strtolower(substr($stream, 0, 4)) == 'true') ||
+			(strlen($stream) >= 5 && strtolower(substr($stream, 0, 5)) == 'false');
+	}
+
+	public static function getToken(string &$stream): Token
+	{
+		if (strlen($stream) >= 4 && strtolower(substr($stream, 0, 4)) == 'true')
+		{
+			$stream = substr($stream, 4);
+			return new BooleanLiteral(true);
+		}
+		elseif (strlen($stream) >= 5 && strtolower(substr($stream, 0, 5)) == 'false')
+		{
+			$stream = substr($stream, 5);
+			return new BooleanLiteral(false);
+		}
+		throw new \Exception('Unparseable boolean');
+	}
+
+	/**
+	 * Get the value of this token.
+	 *
+	 * @param  ?\App\Util\GraphNode[]                $arguments
+	 * @return \App\Util\GraphNode|Token|scalar|null
+	 */
+	public function execute(?array $arguments = null)
+	{
+		return $this->getValue();
+	}
+}