Parse FITS keywords

src/FitsHeader.php

@@ -4,7 +4,52 @@ declare(strict_types=1);
 
 namespace Dumbastro\FitsPhp;
 
+use Dumbastro\FitsPhp\Keyword;
+
 class FitsHeader
 {
+    private string $headerBlock;
+    /**
+    * @var Keyword[] $keywords
+    */
+    public readonly array $keywords;
+
+    public function __construct(string $headerBlock)
+    {
+        $this->headerBlock = $headerBlock;
+        $this->keywords = $this->readKeywords();
+    }
+    /**
+    * Initialize the keyword records array
+    * 
+    * From the spec: each keyword record, including
+    * any comments, is at most 80 bytes long
+    * @return Keyword[]
+    */
+    private function readKeywords(): array
+    {
+        $records = str_split($this->headerBlock, 80);
+
+        $records = array_filter(
+            $records,
+            fn (string $r) => trim($r) !== '' && !str_starts_with($r, 'END')
+        );
+
+        $keywords = [];
+
+        foreach ($records as $record) {
+            $splitByComment = explode('/', $record);
+            $comment = isset($splitByComment[1]) ? trim($splitByComment[1]) : null;
+            $nameValue = explode('=', $splitByComment[0]);
+
+            $keywords[] = new Keyword(
+                name : trim($nameValue[0]),
+                value : trim($nameValue[1]),
+                comment : $comment,
+            );
+        }
+
+        return $keywords;
+    }
 }