Csv reader refactor infer delimiter (#1948)

* Refactor delimiter inference for CSV file reading into a separate class

src/PhpSpreadsheet/Reader/Csv.php

@@ -4,6 +4,7 @@
 
 use InvalidArgumentException;
 use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
+use PhpOffice\PhpSpreadsheet\Reader\Csv\Delimiter;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
 
@@ -138,118 +139,26 @@ protected function inferSeparator(): void
             return;
         }
 
-        $potentialDelimiters = [',', ';', "\t", '|', ':', ' ', '~'];
-        $counts = [];
-        foreach ($potentialDelimiters as $delimiter) {
-            $counts[$delimiter] = [];
-        }
-
-        // Count how many times each of the potential delimiters appears in each line
-        $numberLines = 0;
-        while (($line = $this->getNextLine()) !== false && (++$numberLines < 1000)) {
-            $countLine = [];
-            for ($i = strlen($line) - 1; $i >= 0; --$i) {
-                $char = $line[$i];
-                if (isset($counts[$char])) {
-                    if (!isset($countLine[$char])) {
-                        $countLine[$char] = 0;
-                    }
-                    ++$countLine[$char];
-                }
-            }
-            foreach ($potentialDelimiters as $delimiter) {
-                $counts[$delimiter][] = $countLine[$delimiter]
-                    ?? 0;
-            }
-        }
+        $inferenceEngine = new Delimiter($this->fileHandle, $this->escapeCharacter, $this->enclosure);
 
         // If number of lines is 0, nothing to infer : fall back to the default
-        if ($numberLines === 0) {
-            $this->delimiter = reset($potentialDelimiters);
+        if ($inferenceEngine->linesCounted() === 0) {
+            $this->delimiter = $inferenceEngine->getDefaultDelimiter();
             $this->skipBOM();
 
             return;
         }
 
-        // Calculate the mean square deviations for each delimiter (ignoring delimiters that haven't been found consistently)
-        $meanSquareDeviations = [];
-        $middleIdx = floor(($numberLines - 1) / 2);
-
-        foreach ($potentialDelimiters as $delimiter) {
-            $series = $counts[$delimiter];
-            sort($series);
-
-            $median = ($numberLines % 2)
-                ? $series[$middleIdx]
-                : ($series[$middleIdx] + $series[$middleIdx + 1]) / 2;
-
-            if ($median === 0) {
-                continue;
-            }
-
-            $meanSquareDeviations[$delimiter] = array_reduce(
-                $series,
-                function ($sum, $value) use ($median) {
-                    return $sum + ($value - $median) ** 2;
-                }
-            ) / count($series);
-        }
-
-        // ... and pick the delimiter with the smallest mean square deviation (in case of ties, the order in potentialDelimiters is respected)
-        $min = INF;
-        foreach ($potentialDelimiters as $delimiter) {
-            if (!isset($meanSquareDeviations[$delimiter])) {
-                continue;
-            }
-
-            if ($meanSquareDeviations[$delimiter] < $min) {
-                $min = $meanSquareDeviations[$delimiter];
-                $this->delimiter = $delimiter;
-            }
-        }
+        $this->delimiter = $inferenceEngine->infer();
 
         // If no delimiter could be detected, fall back to the default
         if ($this->delimiter === null) {
-            $this->delimiter = reset($potentialDelimiters);
+            $this->delimiter = $inferenceEngine->getDefaultDelimiter();
         }
 
         $this->skipBOM();
     }
 
-    /**
-     * Get the next full line from the file.
-     *
-     * @return false|string
-     */
-    private function getNextLine()
-    {
-        $line = '';
-        $enclosure = ($this->escapeCharacter === '' ? ''
-            : ('(?<!' . preg_quote($this->escapeCharacter, '/') . ')'))
-            . preg_quote($this->enclosure, '/');
-
-        do {
-            // Get the next line in the file
-            $newLine = fgets($this->fileHandle);
-
-            // Return false if there is no next line
-            if ($newLine === false) {
-                return false;
-            }
-
-            // Add the new line to the line passed in
-            $line = $line . $newLine;
-
-            // Drop everything that is enclosed to avoid counting false positives in enclosures
-            $line = preg_replace('/(' . $enclosure . '.*' . $enclosure . ')/Us', '', $line);
-
-            // See if we have any enclosures left in the line
-            // if we still have an enclosure then we need to read the next line as well
-        } while (preg_match('/(' . $enclosure . ')/', $line) > 0);
-
-        return $line;
-    }
-
     /**
      * Return worksheet info (Name, Last Column Letter, Last Column Index, Total Rows, Total Columns).
      *

src/PhpSpreadsheet/Reader/Csv/Delimiter.php

@@ -0,0 +1,144 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Reader\Csv;
+
+class Delimiter
+{
+    protected const POTENTIAL_DELIMETERS = [',', ';', "\t", '|', ':', ' ', '~'];
+
+    protected $fileHandle;
+
+    protected $escapeCharacter;
+
+    protected $enclosure;
+
+    protected $counts = [];
+
+    protected $numberLines = 0;
+
+    protected $delimiter;
+
+    public function __construct($fileHandle, $escapeCharacter, $enclosure)
+    {
+        $this->fileHandle = $fileHandle;
+        $this->escapeCharacter = $escapeCharacter;
+        $this->enclosure = $enclosure;
+
+        $this->countPotentialDelimiters();
+    }
+
+    public function getDefaultDelimiter(): string
+    {
+        return self::POTENTIAL_DELIMETERS[0];
+    }
+
+    public function linesCounted(): int
+    {
+        return $this->numberLines;
+    }
+
+    protected function countPotentialDelimiters(): void
+    {
+        $this->counts = array_fill_keys(self::POTENTIAL_DELIMETERS, []);
+        $delimiterKeys = array_flip(self::POTENTIAL_DELIMETERS);
+
+        // Count how many times each of the potential delimiters appears in each line
+        $this->numberLines = 0;
+        while (($line = $this->getNextLine()) !== false && (++$this->numberLines < 1000)) {
+            $this->countDelimiterValues($line, $delimiterKeys);
+        }
+    }
+
+    protected function countDelimiterValues(string $line, array $delimiterKeys): void
+    {
+        $splitString = str_split($line, 1);
+        if (!is_array($splitString)) {
+            return;
+        }
+
+        $distribution = array_count_values($splitString);
+        $countLine = array_intersect_key($distribution, $delimiterKeys);
+
+        foreach (self::POTENTIAL_DELIMETERS as $delimiter) {
+            $this->counts[$delimiter][] = $countLine[$delimiter] ?? 0;
+        }
+    }
+
+    public function infer(): ?string
+    {
+        // Calculate the mean square deviations for each delimiter
+        //     (ignoring delimiters that haven't been found consistently)
+        $meanSquareDeviations = [];
+        $middleIdx = floor(($this->numberLines - 1) / 2);
+
+        foreach (self::POTENTIAL_DELIMETERS as $delimiter) {
+            $series = $this->counts[$delimiter];
+            sort($series);
+
+            $median = ($this->numberLines % 2)
+                ? $series[$middleIdx]
+                : ($series[$middleIdx] + $series[$middleIdx + 1]) / 2;
+
+            if ($median === 0) {
+                continue;
+            }
+
+            $meanSquareDeviations[$delimiter] = array_reduce(
+                $series,
+                function ($sum, $value) use ($median) {
+                    return $sum + ($value - $median) ** 2;
+                }
+            ) / count($series);
+        }
+
+        // ... and pick the delimiter with the smallest mean square deviation
+        //         (in case of ties, the order in potentialDelimiters is respected)
+        $min = INF;
+        foreach (self::POTENTIAL_DELIMETERS as $delimiter) {
+            if (!isset($meanSquareDeviations[$delimiter])) {
+                continue;
+            }
+
+            if ($meanSquareDeviations[$delimiter] < $min) {
+                $min = $meanSquareDeviations[$delimiter];
+                $this->delimiter = $delimiter;
+            }
+        }
+
+        return $this->delimiter;
+    }
+
+    /**
+     * Get the next full line from the file.
+     *
+     * @return false|string
+     */
+    public function getNextLine()
+    {
+        $line = '';
+        $enclosure = ($this->escapeCharacter === '' ? ''
+                : ('(?<!' . preg_quote($this->escapeCharacter, '/') . ')'))
+            . preg_quote($this->enclosure, '/');
+
+        do {
+            // Get the next line in the file
+            $newLine = fgets($this->fileHandle);
+
+            // Return false if there is no next line
+            if ($newLine === false) {
+                return false;
+            }
+
+            // Add the new line to the line passed in
+            $line = $line . $newLine;
+
+            // Drop everything that is enclosed to avoid counting false positives in enclosures
+            $line = preg_replace('/(' . $enclosure . '.*' . $enclosure . ')/Us', '', $line);
+
+            // See if we have any enclosures left in the line
+            // if we still have an enclosure then we need to read the next line as well
+        } while (preg_match('/(' . $enclosure . ')/', $line) > 0);
+
+        return $line;
+    }
+}