From 400c0adc9738767cdf6fabb596e4e4d85dfa2246 Mon Sep 17 00:00:00 2001
From: eno <eno@open-lab.org>
Date: Sat, 20 Apr 2019 13:34:49 +0200
Subject: [PATCH] Adds lazy JSON parsing

This class implements lazy JSON parsing. When enabled via
<tt>Simple::SQL::JSON.lazy!</tt> it should improve performance if data
is fetched from the database in a JSON format, and is consumed via
a JSON encoder.

This seems a bit far-fetched, but that use case is actually quite common
when implementing a JSON API.
---
 lib/simple/sql/helpers.rb         |  1 +
 lib/simple/sql/helpers/decoder.rb |  4 ++--
 lib/simple/sql/json.rb            | 37 +++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 lib/simple/sql/json.rb

diff --git a/lib/simple/sql/helpers.rb b/lib/simple/sql/helpers.rb
index 0f236c6..b6eddf3 100644
--- a/lib/simple/sql/helpers.rb
+++ b/lib/simple/sql/helpers.rb
@@ -1,6 +1,7 @@
 module ::Simple::SQL::Helpers
 end
 
+require_relative "./json.rb"
 require_relative "helpers/decoder.rb"
 require_relative "helpers/encoder.rb"
 require_relative "helpers/row_converter.rb"
diff --git a/lib/simple/sql/helpers/decoder.rb b/lib/simple/sql/helpers/decoder.rb
index 3ae7c55..c27bc5b 100644
--- a/lib/simple/sql/helpers/decoder.rb
+++ b/lib/simple/sql/helpers/decoder.rb
@@ -21,8 +21,8 @@ def decode_value(type, s)
     when :"timestamp without time zone" then ::Time.parse(s)
     when :"timestamp with time zone"    then ::Time.parse(s)
     when :hstore                        then HStore.parse(s)
-    when :json                          then ::JSON.parse(s)
-    when :jsonb                         then ::JSON.parse(s)
+    when :json                          then ::Simple::SQL::JSON.parse(s)
+    when :jsonb                         then ::Simple::SQL::JSON.parse(s)
     when :boolean                       then s == "t"
     else
       # unknown value, we just return the string here.
diff --git a/lib/simple/sql/json.rb b/lib/simple/sql/json.rb
new file mode 100644
index 0000000..2474d42
--- /dev/null
+++ b/lib/simple/sql/json.rb
@@ -0,0 +1,37 @@
+# rubocop:disable Style/DoubleNegation
+
+# This class implements lazy JSON parsing. When enabled it should improve
+# performance if data is fetched from the database in a JSON format, and is
+# consumed via a JSON encoder.
+#
+# This seems a bit far-fetched, but that use case is actually quite common
+# when implementing a JSON API.
+class Simple::SQL::JSON < BasicObject
+  def self.parse(str)
+    new(str)
+  end
+
+  def initialize(json_string)
+    @json_string = json_string
+  end
+
+  def method_missing(sym, *args, &block)
+    parsed.send(sym, *args, &block) || super
+  end
+
+  def respond_to_missing?(name, include_private = false)
+    parsed.send(:respond_to_missing?, name, include_private) || super
+  end
+
+  def parsed
+    @parsed ||= ::JSON.parse(@json_string)
+  end
+
+  def ==(other)
+    super || (parsed == other)
+  end
+
+  def to_json(*_args)
+    @json_string
+  end
+end