class Pry
  class NoCommandError < StandardError
    def initialize(name, owner)
      super "Command '#{name}' not found in command set #{owner}"
    end
  end

  # This class is used to create sets of commands. Commands can be imported from
  # different sets, aliased, removed, etc.
  class CommandSet
    include Enumerable
    include Pry::Helpers::BaseHelpers

    attr_reader :commands
    attr_reader :helper_module

    # @param [Array<CommandSet>] imported_sets Sets which will be imported
    #   automatically
    # @yield Optional block run to define commands
    def initialize(*imported_sets, &block)
      @commands      = {}
      @helper_module = Module.new

      define_default_commands
      import(*imported_sets)

      instance_eval(&block) if block
    end

    # Defines a new Pry command.
    # @param [String, Regexp] name The name of the command. Can be
    #   Regexp as well as String.
    # @param [String] description A description of the command.
    # @param [Hash] options The optional configuration parameters.
    # @option options [Boolean] :keep_retval Whether or not to use return value
    #   of the block for return of `command` or just to return `nil`
    #   (the default).
    # @option options [Array<String>] :requires_gem Whether the command has
    #   any gem dependencies, if it does and dependencies not met then
    #   command is disabled and a stub proc giving instructions to
    #   install command is provided.
    # @option options [Boolean] :interpolate Whether string #{} based
    #   interpolation is applied to the command arguments before
    #   executing the command. Defaults to true.
    # @option options [String] :listing The listing name of the
    #   command. That is the name by which the command is looked up by
    #   help and by show-command. Necessary for regex based commands.
    # @option options [Boolean] :use_prefix Whether the command uses
    #   `Pry.config.command_prefix` prefix (if one is defined). Defaults
    #   to true.
    # @option options [Boolean] :shellwords Whether the command's arguments
    #   should be split using Shellwords instead of just split on spaces.
    #   Defaults to true.
    # @yield The action to perform. The parameters in the block
    #   determines the parameters the command will receive. All
    #   parameters passed into the block will be strings. Successive
    #   command parameters are separated by whitespace at the Pry prompt.
    # @example
    #   MyCommands = Pry::CommandSet.new do
    #     command "greet", "Greet somebody" do |name|
    #       puts "Good afternoon #{name.capitalize}!"
    #     end
    #   end
    #
    #   # From pry:
    #   # pry(main)> _pry_.commands = MyCommands
    #   # pry(main)> greet john
    #   # Good afternoon John!
    #   # pry(main)> help greet
    #   # Greet somebody
    # @example Regexp command
    #   MyCommands = Pry::CommandSet.new do
    #     command /number-(\d+)/, "number-N regex command", :listing => "number" do |num, name|
    #       puts "hello #{name}, nice number: #{num}"
    #     end
    #   end
    #
    #   # From pry:
    #   # pry(main)> _pry_.commands = MyCommands
    #   # pry(main)> number-10 john
    #   # hello john, nice number: 10
    #   # pry(main)> help number
    #   # number-N regex command
    def block_command(name, description="No description.", options={}, &block)
      description, options = ["No description.", description] if description.is_a?(Hash)
      options = default_options(name).merge!(options)

      commands[name] = Pry::BlockCommand.subclass(name, description, options, helper_module, &block)
    end
    alias_method :command, :block_command

    # Defines a new Pry command class.
    #
    # @param [String, Regexp] name The name of the command. Can be
    #   Regexp as well as String.
    # @param [String] description A description of the command.
    # @param [Hash] options The optional configuration parameters, see {#command}
    # @param &Block  The class body's definition.
    #
    # @example
    #   Pry::Commands.create_command "echo", "echo's the input", :shellwords => false do
    #     def options(opt)
    #       opt.banner "Usage: echo [-u | -d] <string to echo>"
    #       opt.on :u, :upcase, "ensure the output is all upper-case"
    #       opt.on :d, :downcase, "ensure the output is all lower-case"
    #     end
    #
    #     def process
    #       raise Pry::CommandError, "-u and -d makes no sense" if opts.present?(:u) && opts.present?(:d)
    #       result = args.join(" ")
    #       result.downcase! if opts.present?(:downcase)
    #       result.upcase! if opts.present?(:upcase)
    #       output.puts result
    #     end
    #   end
    #
    def create_command(name, description="No description.", options={}, &block)
      description, options = ["No description.", description] if description.is_a?(Hash)
      options = default_options(name).merge!(options)

      commands[name] = Pry::ClassCommand.subclass(name, description, options, helper_module, &block)
      commands[name].class_eval(&block)
      commands[name]
    end

    # Execute a block of code before a command is invoked. The block also
    # gets access to parameters that will be passed to the command and
    # is evaluated in the same context.
    # @param [String, Regexp] name The name of the command.
    # @yield The block to be run before the command.
    # @example Display parameter before invoking command
    #   Pry.commands.before_command("whereami") do |n|
    #     output.puts "parameter passed was #{n}"
    #   end
    def before_command(name, &block)
      cmd = find_command_by_name_or_listing(name)
      cmd.hooks[:before].unshift block
    end

    # Execute a block of code after a command is invoked. The block also
    # gets access to parameters that will be passed to the command and
    # is evaluated in the same context.
    # @param [String, Regexp] name The name of the command.
    # @yield The block to be run after the command.
    # @example Display text 'command complete' after invoking command
    #   Pry.commands.after_command("whereami") do |n|
    #     output.puts "command complete!"
    #   end
    def after_command(name, &block)
      cmd = find_command_by_name_or_listing(name)
      cmd.hooks[:after] << block
    end

    def each &block
      @commands.each(&block)
    end

    # Removes some commands from the set
    # @param [Array<String>] names name of the commands to remove
    def delete(*names)
      names.each do |name|
        cmd = find_command_by_name_or_listing(name)
        commands.delete cmd.name
      end
    end

    # Imports all the commands from one or more sets.
    # @param [Array<CommandSet>] sets Command sets, all of the commands of which
    #   will be imported.
    def import(*sets)
      sets.each do |set|
        commands.merge! set.commands
        helper_module.send :include, set.helper_module
      end
    end

    # Imports some commands from a set
    # @param [CommandSet] set Set to import commands from
    # @param [Array<String>] names Commands to import
    def import_from(set, *names)
      helper_module.send :include, set.helper_module
      names.each do |name|
        cmd = set.find_command_by_name_or_listing(name)
        commands[cmd.name] = cmd
      end
    end

    # @param [String, Regexp] name_or_listing The name or listing name
    #   of the command to retrieve.
    # @return [Command] The command object matched.
    def find_command_by_name_or_listing(name_or_listing)
      if commands[name_or_listing]
        cmd = commands[name_or_listing]
      else
        _, cmd = commands.find { |name, command| command.options[:listing] == name_or_listing }
      end

      raise ArgumentError, "Cannot find a command with name: '#{name_or_listing}'!" if !cmd
      cmd
    end
    protected :find_command_by_name_or_listing

    # Aliases a command
    # @param [String] new_name New name of the command.
    # @param [String] old_name Old name of the command.
    # @param [String, nil] desc New description of the command.
    def alias_command(new_name, old_name, desc="")
      orig_command = find_command_by_name_or_listing(old_name)
      commands[new_name] = orig_command.dup
      commands[new_name].name = new_name
      commands[new_name].description = desc
    end

    # Rename a command. Accepts either actual name or listing name for
    # the `old_name`.
    # `new_name` must be the actual name of the new command.
    # @param [String, Regexp] new_name The new name for the command.
    # @param [String, Regexp] old_name The command's current name.
    # @param [Hash] options The optional configuration parameters,
    #   accepts the same as the `command` method, but also allows the
    #   command description to be passed this way too.
    # @example Renaming the `ls` command and changing its description.
    #   Pry.config.commands.rename "dir", "ls", :description => "DOS friendly ls"
    def rename_command(new_name, old_name, options={})
      cmd = find_command_by_name_or_listing(old_name)

      options = {
        :listing     => new_name,
        :description => cmd.description
      }.merge!(options)

      commands[new_name] = cmd.dup
      commands[new_name].name = new_name
      commands[new_name].description = options.delete(:description)
      commands[new_name].options.merge!(options)
      commands.delete(cmd.name)
    end

    # Sets or gets the description for a command (replacing the old
    # description). Returns current description if no description
    # parameter provided.
    # @param [String, Regexp] name The command name.
    # @param [String] description The command description.
    # @example Setting
    #   MyCommands = Pry::CommandSet.new do
    #     desc "help", "help description"
    #   end
    # @example Getting
    #   Pry.config.commands.desc "amend-line"
    def desc(name, description=nil)
      cmd = find_command_by_name_or_listing(name)
      return cmd.description if !description

      cmd.description = description
    end

    # Defines helpers methods for this command sets.
    # Those helpers are only defined in this command set.
    #
    # @yield A block defining helper methods
    # @example
    #   helpers do
    #     def hello
    #       puts "Hello!"
    #     end
    #
    #     include OtherModule
    #   end
    def helpers(&block)
      helper_module.class_eval(&block)
    end


    # @return [Array] The list of commands provided by the command set.
    def list_commands
      commands.keys
    end

    # Find a command that matches the given line
    #
    # @param [String]  the line that may be a command invocation
    # @return [Pry::Command, nil]
    def find_command(val)
      commands.values.select{ |c| c.matches?(val) }.sort_by{ |c| c.match_score(val) }.last
    end

    # Is the given line a command invocation?
    #
    # @param [String]
    # @return [Boolean]
    def valid_command?(val)
      !!find_command(val)
    end

    # Process the given line to see whether it needs executing as a command.
    #
    # @param String  the line to execute
    # @param Hash  the context to execute the commands with
    # @return CommandSet::Result
    #
    def process_line(val, context={})
      if command = find_command(val)
        context = context.merge(:command_set => self)
        retval = command.new(context).process_line(val)
        Result.new(true, retval)
      else
        Result.new(false)
      end
    end

    # @nodoc  used for testing
    def run_command(context, name, *args)
      command = commands[name] or raise NoCommandError.new(name, self)
      command.new(context).call_safely(*args)
    end

    private

    def default_options(name)
      {
        :requires_gem => [],
        :keep_retval => false,
        :argument_required => false,
        :interpolate => true,
        :shellwords => true,
        :listing => name,
        :use_prefix => true
      }
    end

    def define_default_commands

      create_command "help" do |cmd|
        description "Show a list of commands, or help for one command"

        banner <<-BANNER
          Usage: help [ COMMAND ]

          With no arguments, help lists all the available commands in the current
          command-set along with their description.

          When given a command name as an argument, shows the help for that command.
        BANNER

        def process
          if cmd = args.first
            if command = find_command(cmd)
              output.puts command.new.help
            else
              output.puts "No info for command: #{cmd}"
            end
          else
            grouped = commands.values.group_by(&:group)

            help_text = []

            grouped.keys.sort.each do |key|

              commands = grouped[key].select do |command|
                command.description && !command.description.empty?
              end.sort_by do |command|
                command.options[:listing].to_s
              end

              unless commands.empty?
                help_text << "\n#{text.bold(key)}"
                help_text += commands.map do |command|
                  "  #{command.options[:listing].to_s.ljust(18)} #{command.description}"
                end
              end
            end

            stagger_output(help_text.join("\n"))
          end
        end
      end

      create_command "install-command", "Install a disabled command." do |name|

        banner <<-BANNER
          Usage: install-command COMMAND

          Installs the gems necessary to run the given COMMAND. You will generally not
          need to run this unless told to by an error message.
        BANNER

        def process(name)
          require 'rubygems/dependency_installer' unless defined? Gem::DependencyInstaller
          command = find_command(name)

          if command_dependencies_met?(command.options)
            output.puts "Dependencies for #{command.name} are met. Nothing to do."
            return
          end

          output.puts "Attempting to install `#{name}` command..."
          gems_to_install = Array(command.options[:requires_gem])

          gems_to_install.each do |g|
            next if gem_installed?(g)
            output.puts "Installing `#{g}` gem..."

            begin
              Gem::DependencyInstaller.new.install(g)
            rescue Gem::GemNotFoundException
              raise CommandError, "Required Gem: `#{g}` not found. Aborting command installation."
            end
          end

          Gem.refresh
          gems_to_install.each do |g|
            begin
              require g
            rescue LoadError
              raise CommandError, "Required Gem: `#{g}` installed but not found?!. Aborting command installation."
            end
          end

          output.puts "Installation of `#{name}` successful! Type `help #{name}` for information"
        end
      end
    end
  end

  # Wraps the return result of process_commands, indicates if the
  # result IS a command and what kind of command (e.g void)
  class Result
    attr_reader :retval

    def initialize(is_command, retval = nil)
      @is_command, @retval = is_command, retval
    end

    # Is the result a command?
    # @return [Boolean]
    def command?
      @is_command
    end

    # Is the result a command and if it is, is it a void command?
    # (one that does not return a value)
    # @return [Boolean]
    def void_command?
      retval == Command::VOID_VALUE
    end
  end
end