Create indentation guide type

src/spectator/formatting/indent.cr

@@ -0,0 +1,45 @@
+module Spectator::Formatting
+  # Tracks indentation for text output.
+  # To use, create an instance and call `#increase` when a block should be indented.
+  # The `#increase` method yields, so additional `#increase` and `#line` methods can be called.
+  # Then call `#line` to produce a line of text at the current indent.
+  # ```
+  # indent = Indent.new(io)
+  # indent.increase do
+  #   indent.line("Text")
+  #   indent.increase do
+  #     indent.line("More text")
+  #   end
+  # end
+  # ```
+  private struct Indent
+    # Default number of spaces to indent by.
+    INDENT_SIZE = 2
+    
+    # Creates the identation tracker.
+    # The *io* is the stream to output to.
+    # The *indent_size* is how much (number of spaces) to indent at each level.
+    # The *initial_indent* is what the ident should be set to.
+    def initialize(@io : IO, @indent_size = INDENT_SIZE, @inital_indent = 0)
+    end
+
+    # Indents the text and yields.
+    def increase(&block)
+      increase(@indent_size, &block)
+    end
+
+    # Indents the text by a specified amount and yields.
+    def increase(amount) : Nil
+      @indent_size += amount
+      yield
+    ensure
+      @indent_size -= amount
+    end
+
+    # Produces a line of indented text.
+    def line(text)
+      @indent_size.times { io << ' ' }
+      @io.puts text
+    end
+  end
+end