require 'chronicle/etl'

module Chronicle
  module Shell
    class ShellHistoryExtractor < Chronicle::ETL::Extractor
      register_connector do |r|
        r.source = :shell
        r.type = :command
        r.strategy = :local
        r.description = 'shell command history'
      end

      setting :input
      setting :shell, default: 'bash'

      BASH_TIMESTAMP_REGEX = /^\#(?<timestamp>[0-9]{10})/

      def prepare
        @commands = load_commands
      end

      def results_count
        @commands.count
      end

      def extract
        @commands.each do |command|
          meta = {
            username:,
            hostname:,
            shell_name: @config.shell
          }
          yield build_extraction(data: command, meta:)
        end
      end

      private

      # TODO: modularize the shell-specific stuff
      def history_filename
        # Ideally we coudl just use ENV['HISTFILE] but it's not available outside of Bash
        @config.input&.first || __send__("history_filename_default_#{@config.shell}")
      end

      def history_filename_default_bash
        File.join(Dir.home, '.bash_history')
      end

      def history_filename_default_zsh
        File.join(Dir.home, '.zsh_history')
      end

      def username
        @username ||= Etc.getlogin
      end

      def hostname
        @hostname ||= begin
          require 'socket'
          Socket.gethostname
        end
      end

      def load_commands
        commands = []

        case @config.shell.to_sym
        when :bash
          load_commands_from_bash do |command|
            process_command(command, commands)
          end
        when :zsh
          load_commands_from_zsh do |command|
            process_command(command, commands)
          end
        else
          raise "Unknown loader: #{@config.shell}"
        end

        commands = commands.first(@config.limit) if @config.limit

        commands
      end

      def process_command(command, commands)
        return if @config.since && command[:timestamp] < @config.since
        return if @config.until && command[:timestamp] > @config.until

        if block_given?
          yield command
        else
          commands << command
        end
      end

      def load_commands_from_bash
        command = nil
        File.readlines(history_filename).reverse_each do |line|
          timestamp_line = line.scrub.match(BASH_TIMESTAMP_REGEX)
          if timestamp_line && command
            timestamp = Time.at(timestamp_line[:timestamp].to_i)
            command = { timestamp:, command: }
            yield command
          else
            command = line.scrub.strip
          end
        end
      end

      def load_commands_from_zsh
        # TODO: implement this
        raise NotImplementedError
      end
    end
  end
end