From 56f5c14d86d8abafd798dde1138ff6bd01399fb8 Mon Sep 17 00:00:00 2001
From: Sergey Bugaev <bugaevc@gmail.com>
Date: Tue, 27 Aug 2019 14:12:44 +0300
Subject: [PATCH] JSON: Add JSON serializers

These are two new types that allow serializing JSON on-the-fly
as it's generated, without building the whole JSON in memory
first.
---
 AK/JsonArraySerializer.h  | 65 +++++++++++++++++++++++++++++++++
 AK/JsonObjectSerializer.h | 77 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 142 insertions(+)
 create mode 100644 AK/JsonArraySerializer.h
 create mode 100644 AK/JsonObjectSerializer.h

diff --git a/AK/JsonArraySerializer.h b/AK/JsonArraySerializer.h
new file mode 100644
index 0000000000..46bbd14ac5
--- /dev/null
+++ b/AK/JsonArraySerializer.h
@@ -0,0 +1,65 @@
+#pragma once
+
+#include <AK/JsonValue.h>
+
+namespace AK {
+
+template<typename Builder>
+class JsonObjectSerializer;
+
+template<typename Builder>
+class JsonArraySerializer {
+public:
+    explicit JsonArraySerializer(Builder& builder)
+        : m_builder(builder)
+    {
+        m_builder.append('[');
+    }
+
+    JsonArraySerializer(const JsonArraySerializer&) = delete;
+    JsonArraySerializer(JsonArraySerializer&&) = delete;
+
+    ~JsonArraySerializer()
+    {
+        if (!m_finished)
+            finish();
+    }
+
+    void add(const JsonValue& value)
+    {
+        begin_item();
+        value.serialize(m_builder);
+    }
+
+    JsonArraySerializer<Builder> add_array()
+    {
+        begin_item();
+        return JsonArraySerializer(m_builder);
+    }
+
+    // Implemented in JsonObjectSerializer.h
+    JsonObjectSerializer<Builder> add_object();
+
+    void finish()
+    {
+        ASSERT(!m_finished);
+        m_finished = true;
+        m_builder.append(']');
+    }
+
+private:
+    void begin_item()
+    {
+        if (!m_empty)
+            m_builder.append(',');
+        m_empty = false;
+    }
+
+    Builder& m_builder;
+    bool m_empty { true };
+    bool m_finished { false };
+};
+
+}
+
+using AK::JsonArraySerializer;
diff --git a/AK/JsonObjectSerializer.h b/AK/JsonObjectSerializer.h
new file mode 100644
index 0000000000..1cdb7743fe
--- /dev/null
+++ b/AK/JsonObjectSerializer.h
@@ -0,0 +1,77 @@
+#pragma once
+
+#include <AK/JsonArraySerializer.h>
+#include <AK/JsonValue.h>
+
+namespace AK {
+
+template<typename Builder>
+class JsonObjectSerializer {
+public:
+    explicit JsonObjectSerializer(Builder& builder)
+        : m_builder(builder)
+    {
+        m_builder.append('{');
+    }
+
+    JsonObjectSerializer(const JsonObjectSerializer&) = delete;
+    JsonObjectSerializer(JsonObjectSerializer&&) = delete;
+
+    ~JsonObjectSerializer()
+    {
+        if (!m_finished)
+            finish();
+    }
+
+    void add(const StringView& key, const JsonValue& value)
+    {
+        begin_item(key);
+        value.serialize(m_builder);
+    }
+
+    JsonArraySerializer<Builder> add_array(const StringView& key)
+    {
+        begin_item(key);
+        return JsonArraySerializer(m_builder);
+    }
+
+    JsonObjectSerializer<Builder> add_object(const StringView& key)
+    {
+        begin_item(key);
+        return JsonObjectSerializer(m_builder);
+    }
+
+    void finish()
+    {
+        ASSERT(!m_finished);
+        m_finished = true;
+        m_builder.append('}');
+    }
+
+private:
+    void begin_item(const StringView& key)
+    {
+        if (!m_empty)
+            m_builder.append(',');
+        m_empty = false;
+
+        m_builder.append('"');
+        m_builder.append(key);
+        m_builder.append("\":");
+    }
+
+    Builder& m_builder;
+    bool m_empty { true };
+    bool m_finished { false };
+};
+
+template<typename Builder>
+JsonObjectSerializer<Builder> JsonArraySerializer<Builder>::add_object()
+{
+    begin_item();
+    return JsonObjectSerializer(m_builder);
+}
+
+}
+
+using AK::JsonObjectSerializer;