1 files changed, 97 insertions, 0 deletions
diff --git a/tool/lrama/lib/lrama/lexer/location.rb b/tool/lrama/lib/lrama/lexer/location.rb
new file mode 100644
index 0000000000..aefce3e16b
--- /dev/null
+++ b/tool/lrama/lib/lrama/lexer/location.rb
@@ -0,0 +1,97 @@
+module Lrama
+  class Lexer
+    class Location
+      attr_reader :grammar_file, :first_line, :first_column, :last_line, :last_column
+
+      def initialize(grammar_file:, first_line:, first_column:, last_line:, last_column:)
+        @grammar_file = grammar_file
+        @first_line = first_line
+        @first_column = first_column
+        @last_line = last_line
+        @last_column = last_column
+      end
+
+      def ==(other)
+        self.class == other.class &&
+        self.grammar_file == other.grammar_file &&
+        self.first_line == other.first_line &&
+        self.first_column == other.first_column &&
+        self.last_line == other.last_line &&
+        self.last_column == other.last_column
+      end
+
+      def partial_location(left, right)
+        offset = -first_column
+        new_first_line = -1
+        new_first_column = -1
+        new_last_line = -1
+        new_last_column = -1
+
+        _text.each.with_index do |line, index|
+          new_offset = offset + line.length + 1
+
+          if offset <= left && left <= new_offset
+            new_first_line = first_line + index
+            new_first_column = left - offset
+          end
+
+          if offset <= right && right <= new_offset
+            new_last_line = first_line + index
+            new_last_column = right - offset
+          end
+
+          offset = new_offset
+        end
+
+        Location.new(
+          grammar_file: grammar_file,
+          first_line: new_first_line, first_column: new_first_column,
+          last_line: new_last_line, last_column: new_last_column
+        )
+      end
+
+      def to_s
+        "#{path} (#{first_line},#{first_column})-(#{last_line},#{last_column})"
+      end
+
+      def generate_error_message(error_message)
+        <<~ERROR.chomp
+          #{path}:#{first_line}:#{first_column}: #{error_message}
+          #{line_with_carets}
+        ERROR
+      end
+
+      def line_with_carets
+        <<~TEXT
+          #{text}
+          #{carets}
+        TEXT
+      end
+
+      private
+
+      def path
+        grammar_file.path
+      end
+
+      def blanks
+        (text[0...first_column] or raise "#{first_column} is invalid").gsub(/[^\t]/, ' ')
+      end
+
+      def carets
+        blanks + '^' * (last_column - first_column)
+      end
+
+      def text
+        @text ||= _text.join("\n")
+      end
+
+      def _text
+        @_text ||=begin
+          range = (first_line - 1)...last_line
+          grammar_file.lines[range] or raise "#{range} is invalid"
+        end
+      end
+    end
+  end
+end