require 'pathname'
require 'gratr'
require 'gratr/dot'
require 'chrysalis/repository'
require 'chrysalis/core_ext/string'


module Chrysalis
  
  # Represents a software development project, typically an application or
  # library.
  class Project
    attr_accessor :name
    attr_accessor :version
    attr_accessor :working_copy
    
    def initialize
      Chrysalis::Manifest.instance << self
      
      @working_copy = nil
      @tasks = {}
      @dependencies = []
      yield self if block_given?
    end
    
    def url
      Chrysalis::Manifest.instance[self]
    end
    
    # Add a dependency, located at +url+, to the project.
    def dependency(url, params = {})
      @dependencies << [url, params]
    end
    alias_method :dependency=, :dependency
    
    
    def task(name, comment)
      desc = (@tasks.has_key?(name) ? @tasks[name] : '')
      desc.concat_sep(comment, " / ")
      @tasks[name] = desc
    end
    
    def task?(name)
      @tasks.has_key? name
    end
    
    # Retrieve all dependencies required by the project.
    def retrieve
      # A project can be declared as a dependency multiple times, which is a
      # common occurance for shared libraries.  After the initial retrieval, the
      # retrieved flag is set.  Subsequent retrievals are unnessesary.
      return if @retrieved
      @retrieved = true
      
      FileUtils.mkdir_p(Chrysalis.options.prefix)
      
      # Retrieve each direct dependency from its repository, and load it into
      # the manifest.
      @dependencies.each do |url, params|
        # If the URL of the project is already in the manifest, it has already
        # been loaded.
        if !Chrysalis::Manifest.instance[url]
          working_copy = Repository.retrieve(url, Chrysalis.options.prefix, params)
          Chrysalis::Loader.instance.load(url, working_copy)
        end
      end
      
      # Transitively retrieve dependencies.
      @dependencies.each do |url, params|
        Chrysalis::Manifest.instance[url].retrieve
      end
    end
    
    def info
      n = (@name ? @name : "<Unknown Name>")
      v = (@version ? "(#{@version})" : "")
      
      printf "- %s %s\n", n, v
      puts   "  #{self.url}" if self.url.is_a?(String)

      if Rake.application.options.trace
        @tasks.each do |name, comment|
          printf "     %-18s # %s\n", name, comment
        end
      end
    end
    
    def graph(g = GRATR::Digraph.new)
      @dependencies.each do |url, params|
        raise "Illegal declaration of dependency on self." if self.url == url
        
        # If an arc has already been connected between a project and a
        # dependency, a cycle has been induced.  This needs to be detected to
        # prevent this function from looping indefinately.
        #
        # For example:
        #  libone ---depends-on--> libtwo
        #  libtwo ---depends-on--> libone
        #
        # Would graph as follows:
        #  libone --> libtwo
        #    ^           |
        #    '-----------'
        #
        # If not prevented this will keep adding edges from libone -> libtwo ->
        # libone -> libtwo -> libone, and on and on and on, ad infinitum.
        if !g.edge?(self.url, url)
          g.add_edge!(self.url, url)
          
          # Build the graph recursively, by telling the dependency to construct
          # its portion.
          dep = Chrysalis::Manifest.instance[url]
          dep.graph(g) if !dep.nil?
        end
      end
      
      return g.add_vertex!(self.url)
    end
    
    def task_exec_order
      g = graph
      raise "Cyclic dependency detected." if g.cyclic?
      
      g.topsort.reverse
    end
    
  end
  
end