Add next version generation

Author: z4kn4fein

README.md

@@ -24,12 +24,12 @@ use z4kn4fein\SemVer\Version;
 
 $version = Version::parse('2.5.6-alpha.12+build.34');
 
-echo $version->getMajor();          // 2
-echo $version->getMinor();          // 5
-echo $version->getPatch();          // 6
-echo $version->getPreRelease();     // alpha.12
-echo $version->getBuildMeta();      // build.34
-echo $version->getVersionString();  // 2.5.6-alpha.12+build.34
+echo $version->getMajor();                  // 2
+echo $version->getMinor();                  // 5
+echo $version->getPatch();                  // 6
+echo (string)$version->getPreRelease();     // alpha.12
+echo $version->getBuildMeta();              // build.34
+echo (string)$version;                      // 2.5.6-alpha.12+build.34
 ```
 #### Comparing two versions
 ```php
@@ -53,5 +53,18 @@ echo $version->isGreaterThan('2.5.6');               // false
 echo $version->isLessThanOrEqual('2.5.6-alpha.12');  // true
 echo $version->isEqual('2.5.6-alpha.12+build.56');   // true
 ```
+#### Producing incremented versions
+```php
+<?php
+
+use z4kn4fein\SemVer\Version;
+
+$version = Version::create(2, 3, 5, "alpha.4", "build.2");
+
+echo (string)$version->getNextMajorVersion();        // 3.0.0
+echo (string)$version->getNextMinorVersion();        // 2.4.0
+echo (string)$version->getNextPatchVersion();        // 2.3.5
+echo (string)$version->getNextPreReleaseVersion();   // 2.3.5-alpha.5
+```
 ## Invalid version handling
 When the version parsing fails due to an invalid format, the library throws a specific `VersionFormatException`.

src/PreRelease.php

@@ -7,6 +7,15 @@ class PreRelease
     /** @var array */
     private $preReleaseParts;
 
+    /**
+     * PreRelease constructor.
+     * @param array $preReleaseParts The prerelease parts.
+     */
+    private function __construct($preReleaseParts)
+    {
+        $this->preReleaseParts = $preReleaseParts;
+    }
+
     /**
      * @return PreRelease The incremented prerelease
      */
@@ -39,9 +48,7 @@ public function __toString()
 
     private function copy()
     {
-        $result = new PreRelease();
-        $result->preReleaseParts = $this->preReleaseParts;
-        return $result;
+        return new PreRelease($this->preReleaseParts);
     }
 
     /**
@@ -52,20 +59,22 @@ private function validate()
         foreach ($this->preReleaseParts as $part) {
             if ($this->hasOnlyNumbers($part)) {
                 if (strlen($part) > 1 && $part[0] == "0") {
-                    throw new VersionFormatException(sprintf("The prerelease part '%s' is numeric but contains a leading zero.", $part));
+                    throw new VersionFormatException(sprintf(
+                        "The prerelease part '%s' is numeric but contains a leading zero.", $part));
                 } else {
                     continue;
                 }
             }
 
             if (!$this->hasOnlyAlphanumericsAndHyphen($part)) {
-                throw new VersionFormatException(sprintf("The prerelease part '%s' contains invalid character.", $part));
+                throw new VersionFormatException(sprintf(
+                    "The prerelease part '%s' contains invalid character.", $part));
             }
         }
     }
 
     /**
-     * @param $part string part to check.
+     * @param string $part part to check.
      * @return bool True when the part is containing only numbers.
      */
     private function hasOnlyNumbers($part)
@@ -74,7 +83,7 @@ private function hasOnlyNumbers($part)
     }
 
     /**
-     * @param $part string The part to check.
+     * @param string $part The part to check.
      * @return bool True when the part is only containing alphanumerics.
      */
     private function hasOnlyAlphanumericsAndHyphen($part)
@@ -83,7 +92,17 @@ private function hasOnlyAlphanumericsAndHyphen($part)
     }
 
     /**
-     * @param $preReleaseString string The prerelease string.
+     * Creates a new prerelease tag with initial default value (-0).
+     *
+     * @return PreRelease The default prerelease tag.
+     */
+    public static function createDefault()
+    {
+        return new PreRelease([0]);
+    }
+
+    /**
+     * @param string $preReleaseString The prerelease string.
      * @return PreRelease The parsed prerelease part.
      * @throws VersionFormatException When the given prerelease string is invalid.
      */
@@ -94,17 +113,15 @@ public static function parse($preReleaseString)
             throw new VersionFormatException("preReleaseString cannot be empty.");
         }
 
-        $preRelease = new PreRelease();
-
-        $preRelease->preReleaseParts = explode('.', $preReleaseString);
+        $preRelease = new PreRelease(explode('.', $preReleaseString));
         $preRelease->validate();
 
         return $preRelease;
     }
 
     /**
-     * @param $p1 string|PreRelease The left side of the comparison.
-     * @param $p2 string|PreRelease The right side of the comparison.
+     * @param string|PreRelease $p1 The left side of the comparison.
+     * @param string|PreRelease $p2 The right side of the comparison.
      * @return int -1 when $p1 < $p2, 0 when $p1 == $p2, 1 when $p1 > $p2.
      * @throws VersionFormatException When the given prerelease values are invalid.
      */
@@ -134,8 +151,8 @@ public static function compare($p1, $p2)
     }
 
     /**
-     * @param $a mixed The left side of the comparison.
-     * @param $b mixed The right side of the comparison.
+     * @param mixed $a The left side of the comparison.
+     * @param mixed $b The right side of the comparison.
      * @return int -1 when $a < $b, 0 when $a == $b, 1 when $v1 > $b.
      */
     private static function comparePart($a, $b)