add pango markup converter

src/Pango.php

@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Yggverse\Gemini;
+
+class Pango
+{
+    public static function fromGemtext(
+        string $gemtext
+    ): string
+    {
+        return self::fromBody(
+            new \Yggverse\Gemini\Gemtext\Body(
+                $gemtext
+            )
+        );
+    }
+
+    public static function fromBody(
+        \Yggverse\Gemini\Gemtext\Body $body
+    ): string
+    {
+        // Format body
+        $lines = $body->getLines();
+
+        $escaped = [];
+
+        /// Format H1
+        foreach ($body->getH1() as $index => $h1)
+        {
+            $lines[$index] = sprintf(
+                '<span size="xx-large">%s</span>',
+                htmlentities(
+                    $h1
+                )
+            );
+
+            $escaped[] = $index;
+        }
+
+        /// Format H2
+        foreach ($body->getH2() as $index => $h2)
+        {
+            $lines[$index] = sprintf(
+                '<span size="x-large">%s</span>',
+                htmlentities(
+                    $h2
+                )
+            );
+
+            $escaped[] = $index;
+        }
+
+        /// Format H3
+        foreach ($body->getH3() as $index => $h3)
+        {
+            $lines[$index] = sprintf(
+                '<span size="large">%s</span>',
+                htmlentities(
+                    $h3
+                )
+            );
+
+            $escaped[] = $index;
+        }
+
+        /// Escape entities
+        foreach ($lines as $index => $line)
+        {
+            if (!in_array($index, $escaped))
+            {
+                $lines[$index] = htmlentities(
+                    $line
+                );
+            }
+        }
+
+        // @TODO links, code, escape entities
+
+        return implode(
+            PHP_EOL,
+            $lines
+        );
+    }
+}