Extracting Halstead Calculations from the Visitor

src/Business/Cognitive/Parser.php

@@ -4,6 +4,7 @@
 
 namespace Phauthentic\CognitiveCodeAnalysis\Business\Cognitive;
 
+use Phauthentic\CognitiveCodeAnalysis\Business\Halstead\HalsteadMetricsCalculator;
 use Phauthentic\CognitiveCodeAnalysis\CognitiveAnalysisException;
 use Phauthentic\CognitiveCodeAnalysis\PhpParser\AnnotationVisitor;
 use Phauthentic\CognitiveCodeAnalysis\PhpParser\CognitiveMetricsVisitor;
@@ -25,6 +26,7 @@ class Parser
     protected CyclomaticComplexityVisitor $cyclomaticComplexityVisitor;
     protected HalsteadMetricsVisitor $halsteadMetricsVisitor;
     protected CombinedMetricsVisitor $combinedVisitor;
+    protected HalsteadMetricsCalculator $halsteadCalculator;
 
     public function __construct(
         ParserFactory $parserFactory,
@@ -44,7 +46,8 @@ public function __construct(
         $this->cyclomaticComplexityVisitor->setAnnotationVisitor($this->annotationVisitor);
         $this->traverser->addVisitor($this->cyclomaticComplexityVisitor);
 
-        $this->halsteadMetricsVisitor = new HalsteadMetricsVisitor();
+        $this->halsteadCalculator = new HalsteadMetricsCalculator();
+        $this->halsteadMetricsVisitor = new HalsteadMetricsVisitor($this->halsteadCalculator);
         $this->halsteadMetricsVisitor->setAnnotationVisitor($this->annotationVisitor);
         $this->traverser->addVisitor($this->halsteadMetricsVisitor);
 

src/Business/Halstead/HalsteadMetricsCalculator.php

@@ -0,0 +1,106 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phauthentic\CognitiveCodeAnalysis\Business\Halstead;
+
+/**
+ * @SuppressWarnings("PHPMD.ShortVariable")
+ */
+class HalsteadMetricsCalculator implements HalsteadMetricsCalculatorInterface
+{
+    /**
+     * Calculate complete Halstead metrics for given operators and operands.
+     *
+     * @param array<string> $operators Array of operator types
+     * @param array<string> $operands Array of operand values
+     * @param string $identifier Identifier for the metrics (class name or method FQN)
+     * @return array<string, mixed> Array containing all Halstead metrics
+     */
+    public function calculateMetrics(array $operators, array $operands, string $identifier): array
+    {
+        // Step 1: Count distinct and total occurrences of operators and operands
+        $distinctOperators = count(array_unique($operators));
+        $distinctOperands = count(array_unique($operands));
+        $totalOperators = count($operators);
+        $totalOperands = count($operands);
+
+        // Step 2: Calculate basic metrics
+        $programLength = $this->calculateProgramLength($totalOperators, $totalOperands);
+        $programVocabulary = $this->calculateProgramVocabulary($distinctOperators, $distinctOperands);
+
+        // Step 3: Calculate advanced metrics
+        $volume = $this->calculateVolume($programLength, $programVocabulary);
+        $difficulty = $this->calculateDifficulty($distinctOperators, $totalOperands, $distinctOperands);
+        $effort = $difficulty * $volume;
+
+        // Step 4: Prepare the results array
+        return [
+            'n1' => $distinctOperators,
+            'n2' => $distinctOperands,
+            'N1' => $totalOperators,
+            'N2' => $totalOperands,
+            'programLength' => $programLength,
+            'programVocabulary' => $programVocabulary,
+            'volume' => $volume,
+            'difficulty' => $difficulty,
+            'effort' => $effort,
+            'fqName' => $identifier,
+        ];
+    }
+
+    /**
+     * Calculate the program length.
+     *
+     * @param int $N1 The total occurrences of operators
+     * @param int $N2 The total occurrences of operands
+     * @return int The program length
+     */
+    public function calculateProgramLength(int $N1, int $N2): int
+    {
+        return $N1 + $N2;
+    }
+
+    /**
+     * Calculate the program vocabulary.
+     *
+     * @param int $n1 The count of distinct operators
+     * @param int $n2 The count of distinct operands
+     * @return int The program vocabulary
+     */
+    public function calculateProgramVocabulary(int $n1, int $n2): int
+    {
+        return $n1 + $n2;
+    }
+
+    /**
+     * Calculate the volume of the program.
+     *
+     * @param int $programLength The length of the program
+     * @param int $programVocabulary The vocabulary of the program
+     * @return float The volume of the program
+     */
+    public function calculateVolume(int $programLength, int $programVocabulary): float
+    {
+        if ($programVocabulary <= 0) {
+            return 0.0;
+        }
+        return $programLength * log($programVocabulary, 2);
+    }
+
+    /**
+     * Calculate the difficulty of the program.
+     *
+     * @param int $n1 The count of distinct operators
+     * @param int $N2 The total occurrences of operands
+     * @param int $n2 The count of distinct operands
+     * @return float The difficulty of the program
+     */
+    public function calculateDifficulty(int $n1, int $N2, int $n2): float
+    {
+        if ($n2 === 0) {
+            return 0.0;
+        }
+        return ($n1 / 2) * ($N2 / $n2);
+    }
+}

src/Business/Halstead/HalsteadMetricsCalculatorInterface.php

@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phauthentic\CognitiveCodeAnalysis\Business\Halstead;
+
+/**
+ * @SuppressWarnings("PHPMD.ShortVariable")
+ */
+interface HalsteadMetricsCalculatorInterface
+{
+    /**
+     * Calculate complete Halstead metrics for given operators and operands.
+     *
+     * @param array<string> $operators Array of operator types
+     * @param array<string> $operands Array of operand values
+     * @param string $identifier Identifier for the metrics (class name or method FQN)
+     * @return array<string, mixed> Array containing all Halstead metrics
+     */
+    public function calculateMetrics(array $operators, array $operands, string $identifier): array;
+
+    /**
+     * Calculate the volume of the program.
+     *
+     * @param int $programLength The length of the program
+     * @param int $programVocabulary The vocabulary of the program
+     * @return float The volume of the program
+     */
+    public function calculateVolume(int $programLength, int $programVocabulary): float;
+
+    /**
+     * Calculate the difficulty of the program.
+     *
+     * @param int $n1 The count of distinct operators
+     * @param int $N2 The total occurrences of operands
+     * @param int $n2 The count of distinct operands
+     * @return float The difficulty of the program
+     */
+    public function calculateDifficulty(int $n1, int $N2, int $n2): float;
+
+    /**
+     * Calculate the program length.
+     *
+     * @param int $N1 The total occurrences of operators
+     * @param int $N2 The total occurrences of operands
+     * @return int The program length
+     */
+    public function calculateProgramLength(int $N1, int $N2): int;
+
+    /**
+     * Calculate the program vocabulary.
+     *
+     * @param int $n1 The count of distinct operators
+     * @param int $n2 The count of distinct operands
+     * @return int The program vocabulary
+     */
+    public function calculateProgramVocabulary(int $n1, int $n2): int;
+}

src/PhpParser/CombinedMetricsVisitor.php

@@ -4,6 +4,7 @@
 
 namespace Phauthentic\CognitiveCodeAnalysis\PhpParser;
 
+use Phauthentic\CognitiveCodeAnalysis\Business\Halstead\HalsteadMetricsCalculator;
 use PhpParser\Node;
 use PhpParser\NodeVisitor;
 
@@ -18,13 +19,15 @@ class CombinedMetricsVisitor implements NodeVisitor
     private CognitiveMetricsVisitor $cognitiveVisitor;
     private CyclomaticComplexityVisitor $cyclomaticVisitor;
     private HalsteadMetricsVisitor $halsteadVisitor;
+    private HalsteadMetricsCalculator $halsteadCalculator;
 
     public function __construct()
     {
         $this->annotationVisitor = new AnnotationVisitor();
         $this->cognitiveVisitor = new CognitiveMetricsVisitor();
         $this->cyclomaticVisitor = new CyclomaticComplexityVisitor();
-        $this->halsteadVisitor = new HalsteadMetricsVisitor();
+        $this->halsteadCalculator = new HalsteadMetricsCalculator();
+        $this->halsteadVisitor = new HalsteadMetricsVisitor($this->halsteadCalculator);
     }
 
     /**