Add HashUtils.deep_transform_keys

lib/format_parser.rb

@@ -5,6 +5,7 @@
 # top-level methods of the library.
 module FormatParser
   require_relative 'format_parser/version'
+  require_relative 'hash_utils'
   require_relative 'attributes_json'
   require_relative 'image'
   require_relative 'audio'

lib/hash_utils.rb

@@ -0,0 +1,19 @@
+# based on https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/hash/keys.rb#L116
+# I chose to copy this method instead of adding activesupport as a dependency
+# because we want to have the least number of dependencies
+module FormatParser
+  class HashUtils
+    def self.deep_transform_keys(object, &block)
+      case object
+      when Hash
+        object.each_with_object({}) do |(key, value), result|
+          result[yield(key)] = deep_transform_keys(value, &block)
+        end
+      when Array
+        object.map { |e| deep_transform_keys(e, &block) }
+      else
+        object
+      end
+    end
+  end
+end

spec/hash_utils_spec.rb

@@ -0,0 +1,42 @@
+require 'spec_helper'
+
+describe FormatParser::HashUtils do
+  describe '.deep_transform_keys' do
+    it 'transforms all the keys in a hash' do
+      hash = { aa: 1, 'bb' => 2 }
+      result = described_class.deep_transform_keys(hash, &:to_s)
+
+      expect(result).to eq('aa' => 1, 'bb' => 2)
+    end
+
+    it 'transforms all the keys in a array of hashes' do
+      array = [{ aa: 1, bb: 2 }, { cc: 3, dd: [{c: 2, d: 3}] }]
+      result = described_class.deep_transform_keys(array, &:to_s)
+
+      expect(result).to eq(
+        [{'aa' => 1, 'bb' => 2}, {'cc' => 3, 'dd' => [{'c' => 2, 'd' => 3}]}]
+      )
+    end
+
+    it 'transforms all the keys in a hash recursively' do
+      hash = { aa: 1, bb: { cc: 22, dd: 3 } }
+      result = described_class.deep_transform_keys(hash, &:to_s)
+
+      expect(result).to eq('aa' => 1, 'bb' => { 'cc' => 22, 'dd' => 3})
+    end
+
+    it 'does nothing for an non array/hash object' do
+      object = Object.new
+      result = described_class.deep_transform_keys(object, &:to_s)
+
+      expect(result).to eq(object)
+    end
+
+    it 'returns the last value if different keys are transformed into the same one' do
+      hash = { aa: 0, 'bb' => 2, bb: 1 }
+      result = described_class.deep_transform_keys(hash, &:to_s)
+
+      expect(result).to eq('aa' => 0, 'bb' => 1)
+    end
+  end
+end