A parameter completion wrapper for (t)csh. It can be called from the built-in csh complete command

csh_complete_wrapper.rb

#!/usr/bin/env ruby
#
# This is a wrapper to query the appropiate command/parameter 
# completions for (t)csh.
#
# Armin Widegreen (c) 2013
#
# A call returns a space-seperated string 
# of the possible completions, e.g.:
#  ParameterCompletion.getCompletionString("cmd1 diff")
#  returns: "-1 -2 -s -r"
#
# The definition of possible completions is done in a hash, see below. 
# The implementation relies on the termination of the last hash-element entry
# with nil.
#
# More examples: 
#  in: cm > "cmd1 cmd2"
#  in: cmd1 di > "diff history"
#  in: cmd2 d  > "" ; no return needed

class ParameterCompletion
  @@complete_hash = {
    "cmd1" => 
    {
      "diff"    => 
      { 
        "-1" => nil,
        "-2" => nil, 
        "-s" => nil,
        "-r" => nil
      }, 
      "history" => 
      {
        "-l" => nil,
        "-a" => nil
      }
    },
    "cmd2" => 
    {
      "s" => nil,
      "d" => nil
    }
  }

  def self.getCompletion(comp_hash, tokens, position)
    token = tokens[position]
    if comp_hash[token].is_a?(Hash) 
      # has sub-hash with sub-param
      return getCompletion(comp_hash[token], tokens, position+1)
    elsif position == tokens.length - 1 &&  
          comp_hash.has_key?(token)
      # last element and has key, no completion!
      return ""
    else 
      # last element (no hash), but no match 
      return comp_hash.keys.join(" ")
    end
  end

  def self.getCompletionString(command)
    tokens = command.split(" ")
    getCompletion(@@complete_hash, tokens, 0)
  end
end

### example call
puts ParameterCompletion.getCompletionString(ARGV.join(" "))