# encoding: utf-8

module RuboCop
  module Cop
    module Lint
      # This cop checks whether the end keywords are aligned properly for do
      # end blocks.
      #
      # @example
      #
      #   variable = lambda do |i|
      #     i
      #   end
      class BlockAlignment < Cop
        include CheckAssignment

        MSG = '`end` at %d, %d is not aligned with `%s` at %d, %d%s'

        def on_block(node)
          return if ignored_node?(node)
          check_block_alignment(node, node)
        end

        def on_and(node)
          return if ignored_node?(node)

          _left, right = *node
          return unless right.type == :block

          check_block_alignment(node, right)
          ignore_node(right)
        end

        alias_method :on_or, :on_and

        def on_op_asgn(node)
          variable, _op, args = *node
          check_assignment(variable, args)
        end

        def on_send(node)
          _receiver, _method, *args = *node
          check_assignment(node, args.last)
        end

        def on_masgn(node)
          variables, args = *node
          check_assignment(variables, args)
        end

        private

        def check_assignment(begin_node, other_node)
          return unless other_node

          block_node = find_block_node(other_node)
          return unless block_node.type == :block

          # If the block is an argument in a function call, align end with
          # the block itself, and not with the function.
          if begin_node.type == :send
            _receiver, method, *_args = *begin_node
            begin_node = block_node if method.to_s =~ /^\w+$/
          end

          # Align with the expression that is on the same line
          # where the block is defined
          if begin_node.type != :mlhs && block_is_on_next_line?(begin_node,
                                                                block_node)
            return
          end
          return if ignored_node?(block_node)

          ignore_node(block_node)
          check_block_alignment(begin_node, block_node)
        end

        def find_block_node(node)
          while [:send, :lvasgn].include?(node.type)
            n = case node.type
                when :send
                  find_block_or_send_node(node) || break
                when :lvasgn
                  _variable, value = *node
                  value
                end
            node = n if n
          end
          node
        end

        def find_block_or_send_node(send_node)
          receiver, _method, args = *send_node
          [receiver, args].find do |subnode|
            subnode && [:block, :send].include?(subnode.type)
          end
        end

        def check_block_alignment(start_node, block_node)
          end_loc = block_node.loc.end
          return unless begins_its_line?(end_loc)

          start_loc = start_node.loc.expression
          return unless start_loc.column != end_loc.column

          do_loc = block_node.loc.begin # Actually it's either do or {.

          # We've found that "end" is not aligned with the start node (which
          # can be a block, a variable assignment, etc). But we also allow
          # the "end" to be aligned with the start of the line where the "do"
          # is, which is a style some people use in multi-line chains of
          # blocks.
          match = /\S.*/.match(do_loc.source_line)
          indentation_of_do_line = match.begin(0)
          return unless end_loc.column != indentation_of_do_line

          add_offense(block_node,
                      end_loc,
                      format(MSG, end_loc.line, end_loc.column,
                             start_loc.source.lines.to_a.first.chomp,
                             start_loc.line, start_loc.column,
                             alt_start_msg(match, start_loc, do_loc,
                                           indentation_of_do_line)))
        end

        def alt_start_msg(match, start_loc, do_loc, indentation_of_do_line)
          if start_loc.line == do_loc.line &&
             start_loc.column == indentation_of_do_line
            ''
          else
            " or `#{match[0]}` at #{do_loc.line}, #{indentation_of_do_line}"
          end
        end

        def message
        end

        def block_is_on_next_line?(begin_node, block_node)
          begin_node.loc.line != block_node.loc.line
        end

        def autocorrect(node)
          ancestor_node = ancestor_on_same_line(node)
          source = node.loc.expression.source_buffer

          lambda do |corrector|
            start_col = (ancestor_node || node).loc.expression.column
            starting_position_of_block_end = node.loc.end.begin_pos
            end_col = node.loc.end.column

            if end_col < start_col
              delta = start_col - end_col
              corrector.insert_before(node.loc.end, ' ' * delta)
            elsif end_col > start_col
              range_start = starting_position_of_block_end + start_col - end_col
              range = Parser::Source::Range.new(source, range_start,
                                                starting_position_of_block_end)
              corrector.remove(range)
            end
          end
        end

        def ancestor_on_same_line(node)
          node.ancestors.reverse.find do |ancestor|
            next unless ancestor.loc.respond_to?(:line)
            ancestor.loc.line == node.loc.line
          end
        end
      end
    end
  end
end