implement Header entity support

src/Document.php

@@ -32,6 +32,20 @@ class Document
 
                 break;
 
+                // Header
+                case Parser\Header::match($line):
+
+                    $this->_entities[] = new Entity\Header(
+                        Parser\Header::getLevel(
+                            $line
+                        ),
+                        Parser\Header::getText(
+                            $line
+                        )
+                    );
+
+                break;
+
                 // Link
                 case Parser\Link::match($line):
 

src/Entity/Header.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yggverse\Gemtext\Entity;
+
+class Header
+{
+    public const TAG = '#';
+
+    private int $_level;
+
+    private ?string $_text;
+
+    public function __construct(
+        int $level,
+        ?string $text = null
+    ) {
+        $this->setLevel(
+            $level
+        );
+
+        $this->setText(
+            $text
+        );
+    }
+
+    public function setLevel(
+        int $level
+    ): void
+    {
+        if (!in_array($level, [1, 2, 3]))
+        {
+            throw new \Exception(
+                _('Incorrect header level')
+            );
+        }
+
+        $this->_level = $level;
+    }
+
+    public function getLevel(): int
+    {
+        return $this->_level;
+    }
+
+    public function setText(
+        ?string $text
+    ): void
+    {
+        if ($text)
+        {
+            $text = trim(
+                $text
+            );
+        }
+
+        $this->_text = $text;
+    }
+
+    public function getText(): ?string
+    {
+        return $this->_text;
+    }
+
+    public function toString(): string
+    {
+        return str_repeat(
+            self::TAG,
+            $this->_level
+        ) . $this->_text;
+    }
+}

src/Parser/Header.php

@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yggverse\Gemtext\Parser;
+
+class Header
+{
+    public static function match(
+        string $line,
+        array &$matches = []
+    ): bool
+    {
+        return (bool) preg_match(
+            '/^(?<level>#{1,3})(?<text>.*)$/m',
+            $line,
+            $matches
+        );
+    }
+
+    public static function getLevel(
+        string $line
+    ): ?int
+    {
+        $matches = [];
+
+        if (self::match($line, $matches))
+        {
+            if (isset($matches['level']))
+            {
+                return (int) strlen(
+                    $matches['level']
+                );
+            }
+        }
+
+        return null;
+    }
+
+    public static function getText(
+        string $line
+    ): ?string
+    {
+        $matches = [];
+
+        if (self::match($line, $matches))
+        {
+            if (isset($matches['text']))
+            {
+                $text = trim(
+                    $matches['text']
+                );
+
+                if ($text)
+                {
+                    return $text;
+                }
+            }
+        }
+
+        return null;
+    }
+}