#--
# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
# All rights reserved.
# See LICENSE.txt for permissions.
#++

require 'timeout'
require 'rubygems/command'
require 'rubygems/user_interaction'

module Gem

  ####################################################################
  # The command manager registers and installs all the individual
  # sub-commands supported by the gem command.
  class CommandManager
    include UserInteraction
    
    # Return the authoratative instance of the command manager.
    def self.instance
      @command_manager ||= CommandManager.new
    end
    
    # Register all the subcommands supported by the gem command.
    def initialize
      @commands = {}
      register_command :build
      register_command :cert
      register_command :check
      register_command :cleanup
      register_command :contents
      register_command :dependency
      register_command :environment
      register_command :fetch
      register_command :generate_index
      register_command :help
      register_command :install
      register_command :list
      register_command :lock
      register_command :mirror
      register_command :outdated
      register_command :pristine
      register_command :query
      register_command :rdoc
      register_command :search
      register_command :server
      register_command :sources
      register_command :specification
      register_command :uninstall
      register_command :unpack
      register_command :update
      register_command :which
    end
    
    # Register the command object.
    def register_command(command_obj)
      @commands[command_obj] = false
    end
    
    # Return the registered command from the command name.
    def [](command_name)
      command_name = command_name.intern
      return nil if @commands[command_name].nil?
      @commands[command_name] ||= load_and_instantiate(command_name)
    end
    
    # Return a list of all command names (as strings).
    def command_names
      @commands.keys.collect {|key| key.to_s}.sort
    end
    
    # Run the config specificed by +args+.
    def run(args)
      process_args(args)
    rescue StandardError, Timeout::Error => ex
      alert_error "While executing gem ... (#{ex.class})\n    #{ex.to_s}"
      ui.errs.puts "\t#{ex.backtrace.join "\n\t"}" if
        Gem.configuration.backtrace
      terminate_interaction(1)
    rescue Interrupt
      alert_error "Interrupted"
      terminate_interaction(1)
    end

    def process_args(args)
      args = args.to_str.split(/\s+/) if args.respond_to?(:to_str)
      if args.size == 0
        say Gem::Command::HELP
        terminate_interaction(1)
      end 
      case args[0]
      when '-h', '--help'
        say Gem::Command::HELP
        terminate_interaction(0)
      when '-v', '--version'
        say Gem::RubyGemsPackageVersion
        terminate_interaction(0)
      when /^-/
        alert_error "Invalid option: #{args[0]}.  See 'gem --help'."
        terminate_interaction(1)
      else
        cmd_name = args.shift.downcase
        cmd = find_command(cmd_name)
        cmd.invoke(*args)
      end
    end

    def find_command(cmd_name)
      possibilities = find_command_possibilities(cmd_name)
      if possibilities.size > 1
        raise "Ambiguous command #{cmd_name} matches [#{possibilities.join(', ')}]"
      end
      if possibilities.size < 1
        raise "Unknown command #{cmd_name}"
      end

      self[possibilities.first]
    end

    def find_command_possibilities(cmd_name)
      len = cmd_name.length
      self.command_names.select { |n| cmd_name == n[0,len] }
    end
    
    private
    def load_and_instantiate(command_name)
      command_name = command_name.to_s
      retried = false

      begin
        const_name = command_name.capitalize.gsub(/_(.)/) { $1.upcase }
        Gem::Commands.const_get("#{const_name}Command").new
      rescue NameError
        if retried then
          raise
        else
          retried = true
          require "rubygems/commands/#{command_name}_command"
          retry
        end
      end
    end
  end
end