ActiveRecord Shell

README

ActiveRecord SHell (or ARSH for short).

Here's the code that actually works. I have been working on a
half-baked pager for the shell, but the code's so ugly I'm not willing
to share it. At least this allows someone to continue the "project".

The original idea was this:

- ls should list available ActiveRecord classes and modules containing
  ActiveRecord classes.
- cd should enter an ActiveRecord class or module. If it's a module, ls
  will display the classes and/or modules in that. If it's a class, ls
  will display the available objects as numbered files (with a pager).
- cat should display the object's content in YAML format.
- ed should start a person's $EDITOR and let him edit that object's YAML.
- find should search in objects. Like find -field string ClassName.
- Support class paths by adding forward slashes, like ClassName/4315
- Fully support tab completion where possible.

arsh

#!/usr/bin/env ruby

# The magic
require File.join(File.dirname(__FILE__), '..', 'lib', 'arsh')

# Rails boot
begin
  puts "Loading Rails..."
  require File.join('.', 'config', 'application')
  require File.join('.', 'config', 'boot')
  Rails.application.require_environment!
rescue
  $stderr.puts "Please run #{$0} in your Rails root."
  exit 1
end

ARSH::Shell.new self.class

arsh.rb

require 'readline'

# ARSH - the ActiveRecord SHell.
module ARSH
  # The commands used in ARSH.
  class Commands
    # Standard output of the command.
    attr_reader :out
    
    # Parses the command in line and starts the right function.
    def initialize(line, shell)
      @params = line.split.reverse
      command = @params.pop
      @params.reverse!
      @shell = shell
      @out = ""
      
      # Rails has some awesome deprecation warnings we don't like.
      # So temporarily send those to /dev/null.
      #old_stderr = $stderr
      #$stderr = File.open('/dev/null', 'a+')

      case command
      when 'exit'
        @shell.bye
      when 'pwd'
        @out = @shell.pwd.to_s
      when 'ls'
        ls
      when 'cd'
        cd
      else
        @out = "No such command: #{command}"
      end

      #$stderr = old_stderr
    end

    # Directory listing.
    def ls
      ar_classes = @shell.pwd.constants.map do |c|
        klass = @shell.pwd.const_get c

        if klass.is_a?(Class) && klass.ancestors.include?(ActiveRecord::Base)
          klass.to_s
        end
      end.compact

      if @shell.pwd == Object && @params.first
        if ar_classes.include? @params.first
          klass = @shell.pwd.const_get @params.first.to_sym
          ls_files klass
        else
          @out = "No such directory: #{@params.first}"
        end
      elsif @shell.pwd == Object
        @out = ar_classes.join ' '
      else
        ls_files @shell.pwd
      end
    end

    # Lists files in a directory.
    def ls_files(klass)
      files = klass.limit(50).map do |obj|
        klass.name.downcase + '_' + obj.id.to_s
      end

      @out = ""
      if files.length == 50
        @out = files.join(' ') + "\nThere's a lot of files to list. Maybe you'd like to use find instead\?"
      else
        @out = files.join ' '
      end
    end

    # Change directory.
    def cd
      if !@params.first || @params.first == '..'
        @shell.pwd = Object
      else
        klass = @shell.pwd.const_get @params.first.to_sym
        if !klass || !klass.ancestors.include?(ActiveRecord::Base)
          @out = "No such directory: #{@params.first}"
        else
          @shell.pwd = klass
        end
      end
    end
  end

  # Shell wrapper for ARSH.
  class Shell
    PROMPT = "#{self.name} %s$ "

    # The parent directory, e.g. the parent class.
    attr_accessor :pwd

    # Start the shell with 'pwd' as starter class.
    def initialize(pwd)
      @pwd = pwd

      # Make sure our shell stays clean after an exit.
      @stty_save = `stty -g`.chomp
      trap('INT') { bye }

      runner
    end

    # Quit.
    def bye
      puts "Bye!"
      system('stty', @stty_save)
      exit
    end

    # The shell itself.
    def runner
      loop do
        prompt = PROMPT % @pwd.name
        line = Readline.readline(prompt, true)

        bye unless line

        out = Commands.new(line, self).out
        puts out unless out.empty?
      end
    end
  end
end