# ===========================================================================
# Project:   Abbot - SproutCore Build Tools
# Copyright: ©2009 Apple Inc.
#            portions copyright @2006-2009 Sprout Systems, Inc.
#            and contributors
# ===========================================================================

module SC

  # Manages a set of tasks.  Borrowed from Rake 0.8.3
  module TaskManager
    # Track the last comment made in the Rakefile.
    attr_accessor :last_description
    alias :last_comment :last_description    # Backwards compatibility

    attr_accessor :last_task_options

    def initialize
      super
      @task_cache = Hash.new {|h,k| h[k] = {} }
      @tasks = Hash.new
      @rules = Array.new
      @scope = Array.new
      @last_description = nil
    end

    def create_rule(*args, &block)
      pattern, arg_names, deps = resolve_args(args)
      pattern = Regexp.new(Regexp.quote(pattern) + '$') if String === pattern
      @rules << [pattern, deps, block]
    end

    def define_task(task_class, *args, &block)
      task_name, arg_names, deps = resolve_args(args)
      task_name = task_class.scope_name(@scope, task_name)
      deps = [deps] unless deps.respond_to?(:to_ary)
      deps = deps.collect {|d| d.to_s }
      task = intern(task_class, task_name)
      task.set_arg_names(arg_names) unless arg_names.empty?
      task.add_description(@last_description)
      task.add_options(@last_task_options)
      @last_description = nil
      task.enhance(deps, &block)
      task
    end

    # Lookup a task.  Return an existing task if found, otherwise
    # create a task of the current type.
    def intern(task_class, task_name)
      @tasks[task_name.to_s] ||= task_class.new(task_name, self)
    end

    # Find a matching task for +task_name+.
    def [](task_name, scopes=nil)
      lookup(task_name, scopes) or
        raise "Don't know how to build task '#{task_name}'"
    end

    # Resolve the arguments for a task/rule.  Returns a triplet of
    # [task_name, arg_name_list, prerequisites].
    def resolve_args(args)
      if args.last.is_a?(Hash)
        deps = args.pop
        resolve_args_with_dependencies(args, deps)
      else
        resolve_args_without_dependencies(args)
      end
    end

    # Resolve task arguments for a task or rule when there are no
    # dependencies declared.
    #
    # The patterns recognized by this argument resolving function are:
    #
    #   task :t
    #   task :t, [:a]
    #   task :t, :a                 (deprecated)
    #
    def resolve_args_without_dependencies(args)
      task_name = args.shift
      if args.size == 1 && args.first.respond_to?(:to_ary)
        arg_names = args.first.to_ary
      else
        arg_names = args
      end
      [task_name, arg_names, []]
    end
    private :resolve_args_without_dependencies

    # Resolve task arguments for a task or rule when there are
    # dependencies declared.
    #
    # The patterns recognized by this argument resolving function are:
    #
    #   task :t => [:d]
    #   task :t, [a] => [:d]
    #   task :t, :needs => [:d]                 (deprecated)
    #   task :t, :a, :needs => [:d]             (deprecated)
    #
    def resolve_args_with_dependencies(args, hash) # :nodoc:
      fail "Task Argument Error" if hash.size != 1
      key, value = hash.map { |k, v| [k,v] }.first
      if args.empty?
        task_name = key
        arg_names = []
        deps = value
      elsif key == :needs
        task_name = args.shift
        arg_names = args
        deps = value
      else
        task_name = args.shift
        arg_names = key
        deps = value
      end
      deps = [deps] unless deps.respond_to?(:to_ary)
      [task_name, arg_names, deps]
    end
    private :resolve_args_with_dependencies

    # List of all defined tasks in this application.
    def tasks
      @tasks.values.sort_by { |t| t.name }
    end

    # Clear all tasks in this application.
    def clear
      @tasks.clear
      @rules.clear
    end

    # Lookup a task, using scope and the scope hints in the task name.
    # This method performs straight lookups without trying to
    # synthesize file tasks or rules.  Special scope names (e.g. '^')
    # are recognized.  If no scope argument is supplied, use the
    # current scope.  Return nil if the task cannot be found.
    def lookup(task_name, initial_scope=nil)
      @task_cache[initial_scope][task_name] ||= begin
        initial_scope ||= @scope
        task_name = task_name.to_s
        if task_name =~ /^rake:/
          scopes = []
          task_name = task_name.sub(/^rake:/, '')
        elsif task_name =~ /^(\^+)/
          scopes = initial_scope[0, initial_scope.size - $1.size]
          task_name = task_name.sub(/^(\^+)/, '')
        else
          scopes = initial_scope
        end
        lookup_in_scope(task_name, scopes)
      end
    end

    # Lookup the task name
    def lookup_in_scope(name, scope)
      n = scope.size
      while n >= 0
        tn = (scope[0,n] + [name]).join(':')
        task = @tasks[tn]
        return task if task
        n -= 1
      end
      nil
    end
    private :lookup_in_scope

    # Return the list of scope names currently active in the task
    # manager.
    def current_scope
      @scope.dup
    end

    # Evaluate the block in a nested namespace named +name+.  Create
    # an anonymous namespace if +name+ is nil.
    def in_namespace(name)
      name ||= generate_name
      @scope.push(name)
      ns = NameSpace.new(self, @scope)
      yield(ns)
      ns
    ensure
      @scope.pop
    end

    private

    # Generate an anonymous namespace name.
    def generate_name
      @seed ||= 0
      @seed += 1
      "_anon_#{@seed}"
    end

  end # TaskManager
end