From 6562efb11ea5c3e9c279778d609a02ee095eed8c Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 25 Oct 2017 09:29:34 -0700
Subject: [PATCH] ircd::json: Add 'defaults' construct to iov.

---
 include/ircd/json/iov.h | 18 ++++++++++++++++++
 ircd/json.cc            | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/include/ircd/json/iov.h b/include/ircd/json/iov.h
index ab1559a0f..cc662256a 100644
--- a/include/ircd/json/iov.h
+++ b/include/ircd/json/iov.h
@@ -54,6 +54,8 @@ struct ircd::json::iov
 	struct add_if;
 	struct set;
 	struct set_if;
+	struct defaults;
+	struct defaults_if;
 
   public:
 	bool has(const string_view &key) const;
@@ -103,3 +105,19 @@ struct ircd::json::iov::set_if
 	set_if(iov &, const bool &, member);
 	set_if() = default;
 };
+
+/// Add member to the object vector if doesn't exist; otherwise ignored
+struct ircd::json::iov::defaults
+:protected ircd::json::iov::node
+{
+	defaults(iov &, member);
+	defaults() = default;
+};
+
+/// iov::defaults only if the bool argument is true for your condition
+struct ircd::json::iov::defaults_if
+:protected ircd::json::iov::node
+{
+	defaults_if(iov &, const bool &, member);
+	defaults_if() = default;
+};
diff --git a/ircd/json.cc b/ircd/json.cc
index 57b7b3e5c..c938d7560 100644
--- a/ircd/json.cc
+++ b/ircd/json.cc
@@ -434,6 +434,38 @@ ircd::json::iov::set_if::set_if(iov &iov,
 		iov.pop_front();
 }
 
+ircd::json::iov::defaults::defaults(iov &iov,
+                                    member member)
+:node
+{
+	iov, std::move(member)
+}
+{
+	const auto count
+	{
+		std::count_if(std::begin(iov), std::end(iov), [&member]
+		(const auto &existing)
+		{
+			return string_view{existing.first} == string_view{member.first};
+		})
+	};
+
+	if(count > 1)
+		iov.pop_front();
+}
+
+ircd::json::iov::defaults_if::defaults_if(iov &iov,
+                                          const bool &b,
+                                          member member)
+:node
+{
+	iov, std::move(member)
+}
+{
+	if(!b)
+		iov.pop_front();
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // json/member.h