# typed: strict

module CodeOwnership
  module Private
    module Validations
      class GithubCodeownersUpToDate
        extend T::Sig
        extend T::Helpers
        include Validator

        sig { override.params(files: T::Array[String], autocorrect: T::Boolean, stage_changes: T::Boolean).returns(T::Array[String]) }
        def validation_errors(files:, autocorrect: true, stage_changes: true)
          return [] if Private.configuration.skip_codeowners_validation

          codeowners_filepath = Pathname.pwd.join('.github/CODEOWNERS')
          FileUtils.mkdir_p(codeowners_filepath.dirname) if !codeowners_filepath.dirname.exist?

          header = <<~HEADER
            # STOP! - DO NOT EDIT THIS FILE MANUALLY
            # This file was automatically generated by "bin/codeownership validate".
            #
            # CODEOWNERS is used for GitHub to suggest code/file owners to various GitHub
            # teams. This is useful when developers create Pull Requests since the
            # code/file owner is notified. Reference GitHub docs for more details:
            # https://help.github.com/en/articles/about-code-owners
          HEADER

          expected_content_lines = [
            *header.split("\n"),
            nil, # For line between header and codeowners_file_lines
            *codeowners_file_lines,
            nil, # For end-of-file newline
          ]
          
          expected_contents = expected_content_lines.join("\n")
          actual_contents = codeowners_filepath.exist? ? codeowners_filepath.read : ""
          actual_content_lines = actual_contents.split("\n")

          codeowners_up_to_date = actual_contents == expected_contents

          errors = T.let([], T::Array[String])

          if !codeowners_up_to_date
            if autocorrect
              codeowners_filepath.write(expected_contents)
              if stage_changes
                `git add #{codeowners_filepath}`
              end
            else
              # If there is no current file or its empty, display a shorter message.
              missing_lines = expected_content_lines - actual_content_lines
              extra_lines = actual_content_lines - expected_content_lines
              missing_lines_text = if missing_lines.any?
                <<~COMMENT
                  CODEOWNERS should contain the following lines, but does not:
                  #{(expected_content_lines - actual_content_lines).map { |line| "- \"#{line}\""}.join("\n")}
                COMMENT
              end

              extra_lines_text = if extra_lines.any?
                <<~COMMENT
                  CODEOWNERS should not contain the following lines, but it does:
                  #{(actual_content_lines - expected_content_lines).map { |line| "- \"#{line}\""}.join("\n")}
                COMMENT
              end

              diff_text = if missing_lines_text && extra_lines_text
                 "#{missing_lines_text}\n#{extra_lines_text}".chomp
              elsif missing_lines_text
                missing_lines_text
              elsif extra_lines_text
                extra_lines_text
              else
                ""
              end

              if actual_contents == ""
                errors << <<~CODEOWNERS_ERROR
                  CODEOWNERS out of date. Run `bin/codeownership validate` to update the CODEOWNERS file
                CODEOWNERS_ERROR
              else
                errors << <<~CODEOWNERS_ERROR
                  CODEOWNERS out of date. Run `bin/codeownership validate` to update the CODEOWNERS file

                  #{diff_text.chomp}
                CODEOWNERS_ERROR
              end
            end
          end

          errors
        end

        private

        # Generate the contents of a CODEOWNERS file that GitHub can use to
        # automatically assign reviewers
        # https://help.github.com/articles/about-codeowners/
        sig { returns(T::Array[String]) }
        def codeowners_file_lines
          github_team_map = CodeTeams.all.each_with_object({}) do |team, map|
            team_github = TeamPlugins::Github.for(team).github
            next if team_github.do_not_add_to_codeowners_file

            map[team.name] = team_github.team
          end

          Mapper.all.flat_map do |mapper|
            codeowners_lines = mapper.codeowners_lines_to_owners.filter_map do |line, team|
              team_mapping = github_team_map[team&.name]
              next unless team_mapping

              "/#{line} #{team_mapping}"
            end
            next [] if codeowners_lines.empty?

            [
              '',
              "# #{mapper.description}",
              *codeowners_lines.sort,
            ]
          end
        end
      end
    end
  end
end