LibPDF: Propagate errors in Parser and Document

Userland/Libraries/LibPDF/Error.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2022, Matthew Olsson <mattco@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+
+namespace PDF {
+
+class Error {
+public:
+    enum class Type {
+        Parse,
+        Internal,
+        MalformedPDF,
+    };
+
+    Error(Type type, String const& message)
+        : m_type(type)
+    {
+        switch (type) {
+        case Type::Parse:
+            m_message = String::formatted("Failed to parse PDF file: {}", message);
+            break;
+        case Type::Internal:
+            m_message = String::formatted("Internal error while processing PDF file: {}", message);
+            break;
+        case Type::MalformedPDF:
+            m_message = String::formatted("Malformed PDF file: {}", message);
+            break;
+        }
+    }
+
+    Type type() const { return m_type; }
+    String const& message() const { return m_message; }
+
+private:
+    Type m_type;
+    String m_message;
+};
+
+template<typename T>
+using PDFErrorOr = ErrorOr<T, Error>;
+
+}