1 files changed, 121 insertions, 0 deletions
diff --git a/src/NXP/Classes/Lexer.php b/src/NXP/Classes/Lexer.php
new file mode 100644
index 0000000..676962d
--- /dev/null
+++ b/src/NXP/Classes/Lexer.php
@@ -0,0 +1,121 @@
+<?php
+/**
+ * This file is part of the MathExecutor package
+ *
+ * (c) Alexander Kiryukhin
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code
+ */
+
+namespace NXP\Classes;
+use NXP\Classes\Token\AbstractOperator;
+use NXP\Classes\Token\InterfaceOperator;
+use NXP\Classes\Token\TokenComma;
+use NXP\Classes\Token\TokenFunction;
+use NXP\Classes\Token\TokenLeftBracket;
+use NXP\Classes\Token\TokenNumber;
+use NXP\Classes\Token\TokenRightBracket;
+use NXP\Exception\IncorrectBracketsException;
+use NXP\Exception\IncorrectExpressionException;
+
+/**
+ * @author Alexander Kiryukhin <alexander@symdev.org>
+ */
+class Lexer
+{
+    /**
+     * @var TokenFactory
+     */
+    private $tokenFactory;
+
+    public function __construct($tokenFactory)
+    {
+        $this->tokenFactory = $tokenFactory;
+    }
+
+    /**
+     * @param  string                                      $input Source string of equation
+     * @return array                                       Tokens stream
+     * @throws \NXP\Exception\IncorrectExpressionException
+     */
+    public function stringToTokensStream($input)
+    {
+        $matches = array();
+        preg_match_all($this->tokenFactory->getTokenParserRegex(), $input, $matches);
+        $tokensStream = array_map(
+            function ($token) {
+                return $this->tokenFactory->createToken($token);
+            },
+            $matches[0]
+        );
+
+        return $tokensStream;
+    }
+
+    /**
+     * @param  array                                       $tokensStream Tokens stream
+     * @return array                                       Array of tokens in revers polish notation
+     * @throws \NXP\Exception\IncorrectExpressionException
+     */
+    public function buildReversePolishNotation($tokensStream)
+    {
+        $output = array();
+        $stack = array();
+
+        foreach ($tokensStream as $token) {
+            if ($token instanceof TokenNumber) {
+                $output[] = $token;
+            }
+            if ($token instanceof TokenFunction) {
+                array_push($stack, $token);
+            }
+            if ($token instanceof TokenLeftBracket) {
+                array_push($stack, $token);
+            }
+            if ($token instanceof TokenComma) {
+                while (($current = array_pop($stack)) && (!$current instanceof TokenLeftBracket)) {
+                    $output[] = $current;
+                    if (empty($stack)) {
+                        throw new IncorrectExpressionException();
+                    }
+                }
+            }
+            if ($token instanceof TokenRightBracket) {
+                while (($current = array_pop($stack)) && (!$current instanceof TokenLeftBracket)) {
+                    $output[] = $current;
+                }
+                if (!empty($stack) && ($stack[count($stack)-1] instanceof TokenFunction)) {
+                    $output[] = array_pop($stack);
+                }
+            }
+
+            if ($token instanceof AbstractOperator) {
+                while (
+                    count($stack) > 0 &&
+                    ($stack[count($stack)-1] instanceof InterfaceOperator) &&
+                    (
+                        $token->getAssociation() == AbstractOperator::LEFT_ASSOC &&
+                        $token->getPriority() <= $stack[count($stack)-1]->getPriority()
+                    ) || (
+                        $token->getAssociation() == AbstractOperator::RIGHT_ASSOC &&
+                        $token->getPriority() < $stack[count($stack)-1]->getPriority()
+                    )
+                ) {
+                    $output[] = array_pop($stack);
+                }
+
+                array_push($stack, $token);
+            }
+        }
+        while (!empty($stack)) {
+            $token = array_pop($stack);
+            if ($token instanceof TokenLeftBracket || $token instanceof TokenRightBracket) {
+                throw new IncorrectBracketsException();
+            }
+            $output[] = $token;
+        }
+
+        return $output;
+    }
+}