Enhancement: Sniff new-line character sequence

composer.json

@@ -17,7 +17,7 @@
   "require": {
     "php": "^7.1",
     "justinrainbow/json-schema": "^4.0.0 || ^5.0.0",
-    "localheinz/json-printer": "^1.0.0"
+    "localheinz/json-printer": "^2.0.0"
   },
   "require-dev": {
     "infection/infection": "~0.8.1",

src/Format/Format.php

@@ -20,6 +20,11 @@ final class Format implements FormatInterface
      */
     private const PATTERN_INDENT = '/^[ \t]+$/';
 
+    /**
+     * Constant for a regular expression matching valid new-line character sequence.
+     */
+    private const PATTERN_NEW_LINE = '/^(?>\r\n|\n|\r)$/';
+
     /**
      * @var int
      */
@@ -35,14 +40,20 @@ final class Format implements FormatInterface
      */
     private $hasFinalNewLine;
 
+    /**
+     * @var string
+     */
+    private $newLine;
+
     /**
      * @param int    $jsonEncodeOptions
      * @param string $indent
+     * @param string $newLine
      * @param bool   $hasFinalNewLine
      *
      * @throws \InvalidArgumentException
      */
-    public function __construct(int $jsonEncodeOptions, string $indent, bool $hasFinalNewLine)
+    public function __construct(int $jsonEncodeOptions, string $indent, string $newLine, bool $hasFinalNewLine)
     {
         if (0 > $jsonEncodeOptions) {
             throw new \InvalidArgumentException(\sprintf(
@@ -58,8 +69,16 @@ public function __construct(int $jsonEncodeOptions, string $indent, bool $hasFin
             ));
         }
 
+        if (1 !== \preg_match(self::PATTERN_NEW_LINE, $newLine)) {
+            throw new \InvalidArgumentException(\sprintf(
+                '"%s" is not a valid new-line character sequence.',
+                $newLine
+            ));
+        }
+
         $this->jsonEncodeOptions = $jsonEncodeOptions;
         $this->indent = $indent;
+        $this->newLine = $newLine;
         $this->hasFinalNewLine = $hasFinalNewLine;
     }
 
@@ -73,6 +92,11 @@ public function indent(): string
         return $this->indent;
     }
 
+    public function newLine(): string
+    {
+        return $this->newLine;
+    }
+
     public function hasFinalNewLine(): bool
     {
         return $this->hasFinalNewLine;
@@ -110,6 +134,22 @@ public function withIndent(string $indent): FormatInterface
         return $mutated;
     }
 
+    public function withNewLine(string $newLine): FormatInterface
+    {
+        if (1 !== \preg_match(self::PATTERN_NEW_LINE, $newLine)) {
+            throw new \InvalidArgumentException(\sprintf(
+                '"%s" is not a valid new-line character sequence.',
+                $newLine
+            ));
+        }
+
+        $mutated = clone $this;
+
+        $mutated->newLine = $newLine;
+
+        return $mutated;
+    }
+
     public function withHasFinalNewLine(bool $hasFinalNewLine): FormatInterface
     {
         $mutated = clone $this;

src/Format/FormatInterface.php

@@ -19,8 +19,19 @@ public function jsonEncodeOptions(): int;
 
     public function indent(): string;
 
+    public function newLine(): string;
+
     public function hasFinalNewLine(): bool;
 
+    /**
+     * @param int $jsonEncodeOptions
+     *
+     * @throws \InvalidArgumentException
+     *
+     * @return FormatInterface
+     */
+    public function withJsonEncodeOptions(int $jsonEncodeOptions): self;
+
     /**
      * @param string $indent
      *
@@ -31,13 +42,13 @@ public function hasFinalNewLine(): bool;
     public function withIndent(string $indent): self;
 
     /**
-     * @param int $jsonEncodeOptions
+     * @param string $newLine
      *
      * @throws \InvalidArgumentException
      *
      * @return FormatInterface
      */
-    public function withJsonEncodeOptions(int $jsonEncodeOptions): self;
+    public function withNewLine(string $newLine): self;
 
     public function withHasFinalNewLine(bool $hasFinalNewLine): self;
 }

src/Format/Formatter.php

@@ -45,13 +45,14 @@ public function format(string $json, FormatInterface $format): string
 
         $printed = $this->printer->print(
             $encoded,
-            $format->indent()
+            $format->indent(),
+            $format->newLine()
         );
 
         if (!$format->hasFinalNewLine()) {
             return $printed;
         }
 
-        return $printed . PHP_EOL;
+        return $printed . $format->newLine();
     }
 }

src/Format/Sniffer.php

@@ -27,6 +27,7 @@ public function sniff(string $json): FormatInterface
         return new Format(
             $this->jsonEncodeOptions($json),
             $this->indent($json),
+            $this->newLine($json),
             $this->hasFinalNewLine($json)
         );
     }
@@ -55,6 +56,15 @@ private function indent(string $json): string
         return '    ';
     }
 
+    private function newLine(string $json): string
+    {
+        if (1 === \preg_match('/(?P<newLine>\r\n|\n|\r)/', $json, $match)) {
+            return $match['newLine'];
+        }
+
+        return PHP_EOL;
+    }
+
     private function hasFinalNewLine(string $json): bool
     {
         if (\rtrim($json, " \t") === \rtrim($json)) {