Refactor under tests yay

lib/magic_comment_hydrator.rb

@@ -12,46 +12,79 @@ def hydrate
   end
 
   def next_magic_element
-    eval_ruby_regex = %r{<(eval-ruby)>(.*?)</eval-ruby>}m
-    include_in_header_regex =
-      %r{<(include-in-header)>(.*?)</include-in-header>}m
-    content.match(eval_ruby_regex) || content.match(include_in_header_regex)
+    IncludeInHeader.recognize(content) || EvalRuby.recognize(content, self)
   end
 
   def next
     fail "No more hydrating to do!" if next_magic_element.nil?
+    return self.class.new(content: next_magic_element.result, data: data)
+  end
+
+  private
+
+  class IncludeInHeader
+    attr_reader :content
+    attr_reader :match
+
+    def self.recognize(content)
+      match = content.match(%r{<include-in-header>(.*?)</include-in-header>}m)
+      new(content:, match:) if match
+    end
+
+    def initialize(content:, match:)
+      @content = content
+      @match = match
+    end
+
+    def end_of_head
+      content.index("</head>")
+    end
+
+    def entire_magic_element
+      match[0]
+    end
+
+    def children
+      match[1]
+    end
+
+    def result
+      content.sub(entire_magic_element, "").insert(end_of_head, children)
+    end
+  end
+
+  class EvalRuby
+    attr_reader :content
+    attr_reader :hydrator
+    attr_reader :match
+
+    def self.recognize(content, hydrator)
+      match = content.match(%r{<eval-ruby>(.*?)</eval-ruby>}m)
+      new(content:, match:, hydrator:) if match
+    end
+
+    def initialize(content:, match:, hydrator:)
+      @content = content
+      @match = match
+      @hydrator = hydrator
+    end
 
-    entire_magic_element = next_magic_element[0]
-    magic_element_name = next_magic_element[1]
-    magic_element_children = next_magic_element[2]
-
-    replacement =
-      case magic_element_name
-      when "eval-ruby"
-        eval(magic_element_children).to_s.strip
-      when "include-in-header"
-        magic_element_children.to_s.strip
-      else
-        fail "Don't know how to handle #{magic_element_name}"
-      end
-
-    insert_at =
-      case magic_element_name
-      when "include-in-header"
-        content.index("</head>")
-      when "eval-ruby"
-        content.index(entire_magic_element)
-      else
-        fail "Don't know how to handle #{magic_element_name}"
-      end
-
-    if insert_at > content.index(entire_magic_element)
-      fail "Magic element cannot appear before the targeted replacement position, yet"
-    end
-
-    next_content =
-      content.sub(entire_magic_element, "").insert(insert_at, replacement)
-
-    self.class.new(content: next_content, data: data)
+    def entire_magic_element
+      match[0]
+    end
+
+    def ruby_code
+      match[1]
+    end
+
+    # Eval in the context of hydrator to have access to data
+    def replacement
+      hydrator.instance_eval(ruby_code).to_s
+    end
+
+    def result
+      position = content.index(entire_magic_element)
+      content.sub(entire_magic_element, "").insert(position, replacement)
+    end
   end
 end