From 51155a7d9cd2c28b38accb9d9b49018bd4868040 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20Sch=C3=B6nlaub?= <manuel.schoenlaub@gmail.com>
Date: Mon, 6 May 2024 20:22:56 +0200
Subject: [PATCH] feat: add hook hints (#135)
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Signed-off-by: Manuel Schönlaub <manuel.schoenlaub@gmail.com>
---
 lib/open_feature/sdk/hooks/hints.rb       | 32 +++++++++++++++
 spec/open_feature/sdk/hooks/hints_spec.rb | 48 +++++++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 lib/open_feature/sdk/hooks/hints.rb
 create mode 100644 spec/open_feature/sdk/hooks/hints_spec.rb

diff --git a/lib/open_feature/sdk/hooks/hints.rb b/lib/open_feature/sdk/hooks/hints.rb
new file mode 100644
index 0000000..c9a0f73
--- /dev/null
+++ b/lib/open_feature/sdk/hooks/hints.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module OpenFeature
+  module SDK
+    module Hooks
+      class Hints < DelegateClass(Hash)
+        ALLOWED_TYPES = [String, Symbol, Numeric, TrueClass, FalseClass, Time, Hash, Array].freeze
+
+        def initialize(hash = {})
+          hash.each do |key, value|
+            assert_allowed_key(key)
+            assert_allowed_value(value)
+          end
+          @hash = hash.dup
+          super(@hash)
+          freeze
+        end
+
+        private
+
+        def assert_allowed_key(key)
+          raise ArgumentError, "Only String or Symbol are allowed as keys." unless key.is_a?(String) || key.is_a?(Symbol)
+        end
+
+        def assert_allowed_value(value)
+          allowed_type = ALLOWED_TYPES.any? { |t| value.is_a?(t) }
+          raise ArgumentError, "Only #{ALLOWED_TYPES.join(", ")} are allowed as values." unless allowed_type
+        end
+      end
+    end
+  end
+end
diff --git a/spec/open_feature/sdk/hooks/hints_spec.rb b/spec/open_feature/sdk/hooks/hints_spec.rb
new file mode 100644
index 0000000..f73d253
--- /dev/null
+++ b/spec/open_feature/sdk/hooks/hints_spec.rb
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+require "open_feature/sdk/hooks/hints"
+
+RSpec.describe OpenFeature::SDK::Hooks::Hints do
+  let(:hint_hash) { {key: [], nested: {key: []}} }
+  subject(:hints) { described_class.new(hint_hash) }
+  context "Immutability" do
+    it "is frozen" do
+      expect(hints).to be_frozen
+    end
+
+    it "does not allow addition of new keys" do
+      expect { hints[:new_key] = "new_value" }.to raise_error(FrozenError)
+    end
+
+    it "does allow modification of existing values" do
+      expect(hints[:key]).to_not be_frozen
+      expect { hints[:key] << "abc" }.to_not raise_error
+    end
+
+    it "does not allow deletion of keys" do
+      expect { hints.delete(:key) }.to raise_error(FrozenError)
+    end
+
+    it "allows reading of keys" do
+      expect(hints[:key]).to eq([])
+    end
+
+    it "only allows string keys" do
+      expect { described_class.new(1 => []) }.to raise_error(ArgumentError) do |e|
+        expect(e.message).to include("Only String or Symbol are allowed as keys")
+      end
+    end
+
+    it "only allows values of certain types" do
+      expect { described_class.new(key: Object.new) }.to raise_error(ArgumentError) do |e|
+        expect(e.message).to include("Only String, Symbol, Numeric, TrueClass, FalseClass, Time, Hash, Array are allowed as values")
+      end
+    end
+
+    it "does not freeze the original hash" do
+      expect(hint_hash).not_to be_frozen
+    end
+  end
+end