class RuboCop::Cop::Generator::RequireFileInjector

def initialize(source_path:, root_file_path:, output: $stdout)
  @source_path = Pathname(source_path)
  @root_file_path = Pathname(root_file_path)
  @require_entries = File.readlines(root_file_path)
  @output = output
end

def inject
  return if require_exists? || !target_line
  File.write(root_file_path, updated_directives)
  require = injectable_require_directive.chomp
  output.puts "[modify] #{root_file_path} - `#{require}` was injected."
end

def injectable_require_directive
  "require_relative '#{require_path}'\n"
end

def require_exists?
  require_entries.any? do |entry|
    entry == injectable_require_directive
  end
end

def require_path
  path = source_path.relative_path_from(root_file_path.dirname)
  path.to_s.sub('.rb', '')
end

def require_path_fragments(require_directove)
  path = require_directove.match(REQUIRE_PATH)
  path ? path.captures.first.split('/') : []
end

def target_line
  @target_line ||= begin
    in_the_same_department = false
    inject_parts = require_path_fragments(injectable_require_directive)
    require_entries.find.with_index do |entry, index|
      current_entry_parts = require_path_fragments(entry)
      if inject_parts[0..-2] == current_entry_parts[0..-2]
        in_the_same_department = true
        break index if inject_parts.last < current_entry_parts.last
      elsif in_the_same_department
        break index
      end
    end
  end
end

def updated_directives
  require_entries.insert(target_line,
                         injectable_require_directive).join
end