module Alf
  module Shell
    class DocManager

      # Main documentation folder
      DOC_FOLDER = Path.backfind("doc")

      #
      # Called by Quickl when it's time to generate documentation of `cmd`.
      #
      def call(cmd, options = {})
        if (file = find_file(cmd)).file?
          text = file.read

          # Replace occurences of #{signature} to #{signature.to_xxx}
          # according to options
          method = (options[:method] || "shell").to_s
          text = text.gsub('#(signature)', '#(signature.to_' + method + ')')

          # Replace occurences of #{...} on single lines
          text = text.gsub(/^([ \t]*)#\(([^\)]+)\)/){|match|
            spacing, invocation  = $1, $2
            res = cmd.instance_eval(invocation).to_s
            realign(res, spacing, true)
          }

          # Replace occurences of #{...} in other places
          text = text.gsub(/#\(([^\)]+)\)/){|match|
            cmd.instance_eval($1).to_s
          }

          # Replace occurences of !{...} by the execution of the example
          text = text.gsub(/^([ \t]*)!\(([^\)]+)\)/){|match|
            spacing, invocation  = $1, $2
            args = Quickl.parse_commandline_args(invocation)[1..-1]
            op   = run_alf_command(args)
            res  = op.to_relation.to_s
            res  = realign(res, spacing, false)[0...-1]
            if options[:method] == :lispy
              invocation = Alf::Support.to_lispy(op)
            end
            realign("$ #{invocation}\n\n#{res}", spacing, false)
          }

        else
          "Sorry, no documentation available for #{cmd.command_name}"
        end
      end

    private

      def run_alf_command(argv, requester = nil)
        argv = Quickl.parse_commandline_args(argv) if argv.is_a?(String)
        argv = Quickl.split_commandline_args(argv, '|')
        argv.inject(nil) do |cmd,arr|
          arr.shift if arr.first == "alf"
          main = Alf::Shell::Main.new(Alf::Shell::DEFAULT_CONFIG)
          main.config.adapter = Alf.examples_adapter
          main.stdin_operand = cmd unless cmd.nil?
          main.run(arr, requester)
        end
      end

      def realign(txt, spacing, strip)
        rx = strip ? /^[ \t]*/ : /^/
        txt.gsub(rx, spacing)
      end

      def find_file(cmd)
        where = if cmd.command?
          "commands"
        elsif cmd.operator? && cmd.relational?
          File.join("operators", "relational")
        elsif cmd.operator? && cmd.non_relational?
          File.join("operators", "non_relational")
        else
          raise "Unexpected command #{cmd}"
        end
        DOC_FOLDER/where/"#{cmd.command_name}.md"
      end

    end # class DocManager
  end # module Shell
end # module Alf