# encoding: utf-8
# frozen_string_literal: true

require 'pathname'

module RuboCop
  module Cop
    module Style
      # This cop makes sure that Ruby source files have snake_case
      # names. Ruby scripts (i.e. source files with a shebang in the
      # first line) are ignored.
      class FileName < Cop
        MSG_SNAKE_CASE = 'The name of this source file (`%s`) ' \
                         'should use snake_case.'.freeze
        MSG_NO_DEFINITION = '%s should define a class or module ' \
                            'called `%s`.'.freeze
        MSG_REGEX = '`%s` should match `%s`.'.freeze

        SNAKE_CASE = /^[\da-z_.?!]+$/

        def investigate(processed_source)
          file_path = processed_source.buffer.name
          return if config.file_to_include?(file_path)

          for_bad_filename(file_path) do |range, msg|
            add_offense(nil, range, msg)
          end
        end

        private

        def for_bad_filename(file_path)
          basename = File.basename(file_path)
          msg = if filename_good?(basename)
                  return unless expect_matching_definition?
                  return if find_class_or_module(processed_source.ast,
                                                 to_namespace(file_path))
                  no_definition_message(basename, file_path)
                else
                  return if cop_config['IgnoreExecutableScripts'] &&
                            shebang?(first_line)
                  other_message(basename)
                end

          yield source_range(processed_source.buffer, 1, 0), msg
        end

        def first_line
          processed_source.lines.first
        end

        def no_definition_message(basename, file_path)
          format(MSG_NO_DEFINITION,
                 basename,
                 to_namespace(file_path).join('::'))
        end

        def other_message(basename)
          if regex
            format(MSG_REGEX, basename, regex)
          else
            format(MSG_SNAKE_CASE, basename)
          end
        end

        def shebang?(line)
          line && line.start_with?('#!')
        end

        def expect_matching_definition?
          cop_config['ExpectMatchingDefinition']
        end

        def regex
          cop_config['Regex']
        end

        def filename_good?(basename)
          basename = basename.sub(/\.[^\.]+$/, '')
          basename =~ (regex || SNAKE_CASE)
        end

        def find_class_or_module(node, namespace)
          return nil if node.nil?
          name = namespace.pop

          on_node([:class, :module, :casgn], node) do |child|
            next unless (const = child.defined_module)

            const_namespace, const_name = *const
            next unless name == const_name

            return node if namespace.empty?
            return node if match_namespace(child, const_namespace, namespace)
          end
          nil
        end

        def match_namespace(node, namespace, expected)
          expected = expected.dup

          match_partial = lambda do |ns|
            next if ns.nil?
            while ns
              return expected.empty? || expected == [:Object] if ns.cbase_type?
              ns, name = *ns
              name == expected.last ? expected.pop : (return false)
            end
          end

          match_partial.call(namespace)

          node.each_ancestor(:class, :module, :sclass, :casgn) do |ancestor|
            return false if ancestor.sclass_type?
            match_partial.call(ancestor.defined_module)
          end

          expected.empty? || expected == [:Object]
        end

        def to_namespace(path)
          components = Pathname(path).each_filename.to_a
          # To convert a pathname to a Ruby namespace, we need a starting point
          # But RC can be run from any working directory, and can check any path
          # We can't assume that the working directory, or any other, is the
          # "starting point" to build a namespace
          start = %w(lib spec test src)
          start_index = nil

          # To find the closest namespace root take the path components, and
          # then work through them backwards until we find a candidate. This
          # makes sure we work from the actual root in the case of a path like
          # /home/user/src/project_name/lib.
          components.reverse.each_with_index do |c, i|
            if start.include?(c)
              start_index = components.size - i
              break
            end
          end

          if start_index.nil?
            [to_module_name(components.last)]
          else
            components[start_index..-1].map { |c| to_module_name(c) }
          end
        end

        def to_module_name(basename)
          words = basename.sub(/\..*/, '').split('_')
          words.map(&:capitalize).join.to_sym
        end
      end
    end
  end
end