module Berkshelf
  # @author Jamie Winsor <jamie@vialstudios.com>
  class Berksfile
    extend Forwardable

    class << self
      # @param [String] file
      #   a path on disk to a Berksfile to instantiate from
      #
      # @return [Berksfile]
      def from_file(file)
        content = File.read(file)
        object = new(file)
        object.load(content)
      rescue Errno::ENOENT => e
        raise BerksfileNotFound, "No Berksfile or Berksfile.lock found at: #{file}"
      end

      # @param [Array] sources
      #   an array of sources to filter
      # @param [Array, Symbol] excluded
      #   an array of symbols or a symbol representing the group or group(s)
      #   to exclude
      #
      # @return [Array<Berkshelf::CookbookSource>]
      #   an array of sources that are not members of the excluded group(s)
      def filter_sources(sources, excluded)
        excluded = Array(excluded)
        excluded.collect!(&:to_sym)

        sources.select { |source| (excluded & source.groups).empty? }
      end
    end

    @@active_group = nil

    # @return [String]
    #   The path on disk to the file representing this instance of Berksfile
    attr_reader :filepath
    
    # @return [Berkshelf::Downloader]
    attr_reader :downloader

    def_delegator :downloader, :add_location
    def_delegator :downloader, :locations

    def initialize(path)
      @filepath = path
      @sources = Hash.new
      @downloader = Downloader.new(Berkshelf.cookbook_store)
    end

    # Add a cookbook source to the Berksfile to be retrieved and have it's dependencies recurisvely retrieved
    # and resolved.
    #
    # @example a cookbook source that will be retrieved from one of the default locations
    #   cookbook 'artifact'
    #
    # @example a cookbook source that will be retrieved from a path on disk
    #   cookbook 'artifact', path: '/Users/reset/code/artifact'
    #
    # @example a cookbook source that will be retrieved from a remote community site
    #   cookbook 'artifact', site: 'http://cookbooks.opscode.com/api/v1/cookbooks'
    #
    # @example a cookbook source that will be retrieved from the latest API of the Opscode Community Site
    #   cookbook 'artifact', site: :opscode
    #
    # @example a cookbook source that will be retrieved from a Git server
    #   cookbook 'artifact', git: 'git://github.com/RiotGames/artifact-cookbook.git'
    #
    # @example a cookbook source that will be retrieved from a Chef API (Chef Server)
    #   cookbook 'artifact', chef_api: 'https://api.opscode.com/organizations/vialstudios', node_name: 'reset', client_key: '/Users/reset/.chef/knife.rb'
    #
    # @example a cookbook source that will be retrieved from a Chef API using your Knife config
    #   cookbook 'artifact', chef_api: :knife
    #
    # @overload cookbook(name, version_constraint, options = {})
    #   @param [#to_s] name
    #   @param [#to_s] version_constraint
    #   @param [Hash] options
    #
    #   @option options [Symbol, Array] :group
    #     the group or groups that the cookbook belongs to
    #   @option options [String, Symbol] :chef_api
    #     a URL to a Chef API. Alternatively the symbol :knife can be provided
    #     which will instantiate this location with the values found in your
    #     knife configuration.
    #   @option options [String] :site
    #     a URL pointing to a community API endpoint
    #   @option options [String] :path
    #     a filepath to the cookbook on your local disk
    #   @option options [String] :git
    #     the Git URL to clone
    #
    #   @see ChefAPILocation
    #   @see SiteLocation
    #   @see PathLocation
    #   @see GitLocation
    # @overload cookbook(name, options = {})
    #   @param [#to_s] name
    #   @param [Hash] options
    #
    #   @option options [Symbol, Array] :group
    #     the group or groups that the cookbook belongs to
    #   @option options [String, Symbol] :chef_api
    #     a URL to a Chef API. Alternatively the symbol :knife can be provided
    #     which will instantiate this location with the values found in your
    #     knife configuration.
    #   @option options [String] :site
    #     a URL pointing to a community API endpoint
    #   @option options [String] :path
    #     a filepath to the cookbook on your local disk
    #   @option options [String] :git
    #     the Git URL to clone
    #
    #   @see ChefAPILocation
    #   @see SiteLocation
    #   @see PathLocation
    #   @see GitLocation
    def cookbook(*args)
      options = args.last.is_a?(Hash) ? args.pop : Hash.new
      name, constraint = args

      options[:group] = Array(options[:group])
      
      if @@active_group
        options[:group] += @@active_group
      end

      add_source(name, constraint, options)
    end


    def group(*args)
      @@active_group = args
      yield
      @@active_group = nil
    end

    # Use a Cookbook metadata file to determine additional cookbook sources to retrieve. All
    # sources found in the metadata will use the default locations set in the Berksfile (if any are set)
    # or the default locations defined by Berkshelf.
    #
    # @param [Hash] options
    #
    # @option options [String] :path
    #   path to the metadata file
    def metadata(options = {})
      path = options[:path] || File.dirname(filepath)

      metadata_file = Berkshelf.find_metadata(path)

      unless metadata_file
        raise CookbookNotFound, "No 'metadata.rb' found at #{path}"
      end

      metadata = Chef::Cookbook::Metadata.new
      metadata.from_file(metadata_file.to_s)

      name = if metadata.name.empty? || metadata.name.nil?
        File.basename(File.dirname(metadata_file))
      else
        metadata.name
      end

      constraint = "= #{metadata.version}"

      add_source(name, constraint, path: File.dirname(metadata_file))
    end

    # Add a 'Site' default location which will be used to resolve cookbook sources that do not
    # contain an explicit location.
    #
    # @note
    #   specifying the symbol :opscode as the value of the site default location is an alias for the
    #   latest API of the Opscode Community Site.
    #
    # @example
    #   site :opscode
    #   site "http://cookbooks.opscode.com/api/v1/cookbooks"
    #
    # @param [String, Symbol] value
    #
    # @return [Hash]
    def site(value)
      add_location(:site, value)
    end

    # Add a 'Chef API' default location which will be used to resolve cookbook sources that do not
    # contain an explicit location.
    #
    # @note
    #   specifying the symbol :knife as the value of the chef_api default location will attempt to use the
    #   contents of your user's Knife.rb to find the Chef API to interact with.
    #
    # @example using the symbol :knife to add a Chef API default location
    #   chef_api :knife
    #
    # @example using a URL, node_name, and client_key to add a Chef API default location
    #   chef_api "https://api.opscode.com/organizations/vialstudios", node_name: "reset", client_key: "/Users/reset/.chef/knife.rb"
    #
    # @param [String, Symbol] value
    # @param [Hash] options
    #
    # @return [Hash]
    def chef_api(value, options = {})
      add_location(:chef_api, value, options)
    end

    # Add a source of the given name and constraint to the array of sources.
    #
    # @param [String] name
    #   the name of the source to add
    # @param [String, Solve::Constraint] constraint
    #   the constraint to lock the source to
    # @param [Hash] options
    #
    # @raise [DuplicateSourceDefined] if a source is added whose name conflicts
    #   with a source who has already been added.
    #
    # @return [Array<Berkshelf::CookbookSource]
    def add_source(name, constraint = nil, options = {})
      if has_source?(name)
        raise DuplicateSourceDefined, "Berksfile contains two sources named '#{name}'. Remove one and try again."
      end

      options[:constraint] = constraint

      @sources[name] = CookbookSource.new(name, options)
    end

    # @param [#to_s] source
    #   the source to remove
    #
    # @return [Berkshelf::CookbookSource]
    def remove_source(source)
      @sources.delete(source.to_s)
    end

    # @param [#to_s] source
    #   the source to check presence of
    #
    # @return [Boolean]
    def has_source?(source)
      @sources.has_key?(source.to_s)
    end

    # @option options [Symbol, Array] :exclude 
    #   Group(s) to exclude to exclude from the returned Array of sources
    #   group to not be installed
    #
    # @return [Array<Berkshelf::CookbookSource>]
    def sources(options = {})
      l_sources = @sources.collect { |name, source| source }.flatten

      if options[:exclude]
        self.class.filter_sources(l_sources, options[:exclude])
      else
        l_sources
      end
    end

    # @return [Hash]
    #   a hash containing group names as keys and an array of CookbookSources
    #   that are a member of that group as values
    #
    #   Example:
    #     {
    #       nautilus: [
    #         #<Berkshelf::CookbookSource @name="nginx">,
    #         #<Berkshelf::CookbookSource @name="mysql">,
    #       ],
    #       skarner: [
    #         #<Berkshelf::CookbookSource @name="nginx">
    #       ]
    #     }
    def groups
      {}.tap do |groups|
        sources.each do |source|
          source.groups.each do |group|
            groups[group] ||= []
            groups[group] << source
          end
        end
      end
    end

    # @param [String] name
    #   name of the source to return
    #
    # @return [Berkshelf::CookbookSource]
    def [](name)
      @sources[name]
    end
    alias_method :get_source, :[]

    # @option options [Symbol, Array] :without 
    #   Group(s) to exclude which will cause any sources marked as a member of the 
    #   group to not be installed
    # @option options [String, Pathname] :shims
    #   Path to a directory of shims each pointing to a Cookbook Version that is
    #   part of the dependency solution. Each shim is a hard link on disk.
    def install(options = {})
      resolver = Resolver.new(
        self.downloader,
        sources: sources(exclude: options[:without])
      )

      solution = resolver.resolve
      if options[:shims]
        write_shims(options[:shims], solution)
        Berkshelf.formatter.shims_written options[:shims]
      end
      write_lockfile(resolver.sources) unless lockfile_present?
    end

    # @param [String] chef_server_url
    #   the full URL to the Chef Server to upload to
    #
    #     "https://api.opscode.com/organizations/vialstudios"
    #
    # @option options [Symbol, Array] :without 
    #   Group(s) to exclude which will cause any sources marked as a member of the 
    #   group to not be installed
    # @option options [String] :node_name
    #   the name of the client used to sign REST requests to the Chef Server
    # @option options [String] :client_key
    #   the filepath location for the client's key used to sign REST requests
    #   to the Chef Server
    # @option options [Boolean] :force Upload the Cookbook even if the version 
    #   already exists and is frozen on the target Chef Server
    # @option options [Boolean] :freeze Freeze the uploaded Cookbook on the Chef 
    #   Server so that it cannot be overwritten
    def upload(chef_server_url, options = {})
      uploader = Uploader.new(chef_server_url, options)
      solution = resolve(options)

      solution.each do |cb|
        Berkshelf.formatter.upload cb.cookbook_name, cb.version, chef_server_url
        uploader.upload(cb, options)
      end
    end

    # Finds a solution for the Berksfile and returns an array of CachedCookbooks.
    #
    # @option options [Symbol, Array] :without 
    #   Group(s) to exclude which will cause any sources marked as a member of the 
    #   group to not be resolved
    #
    # @return [Array<Berkshelf::CachedCookbooks]
    def resolve(options = {})
      Resolver.new(
        self.downloader,
        sources: sources(exclude: options[:without])
      ).resolve
    end

    # Write a collection of hard links to the given path representing the given
    # CachedCookbooks. Useful for getting Cookbooks in a single location for 
    # consumption by Vagrant, or another tool that expect this structure.
    #
    # @example 
    #   Given the path: '/Users/reset/code/pvpnet/cookbooks'
    #   And a CachedCookbook: 'nginx' verison '0.100.5' at '/Users/reset/.berkshelf/nginx-0.100.5'
    #
    #   A hardlink will be created at: '/Users/reset/code/pvpnet/cookbooks/nginx'
    #
    # @param [Pathname, String] path
    # @param [Array<Berkshelf::CachedCookbook>] cached_cookbooks
    def write_shims(path, cached_cookbooks)
      path        = File.expand_path(path)
      actual_path = nil

      if descendant_directory?(path, Dir.pwd)
        actual_path = path
        FileUtils.rm_rf(actual_path)
        path = File.join(Berkshelf.tmp_dir, "shims")
      end

      FileUtils.mkdir_p(path)
      cached_cookbooks.each do |cached_cookbook|
        destination = File.expand_path(File.join(path, cached_cookbook.cookbook_name))
        FileUtils.rm_rf(destination)
        FileUtils.ln_r(cached_cookbook.path, destination, force: true)
      end

      if actual_path
        FileUtils.mv(path, actual_path)
      end
    end

    # Reload this instance of Berksfile with the given content. The content
    # is a string that may contain terms from the included DSL.
    #
    # @param [String] content
    #
    # @raise [BerksfileReadError] if Berksfile contains bad content
    #
    # @return [Berksfile]
    def load(content)
      begin
        instance_eval(content)
      rescue => e
        raise BerksfileReadError.new(e), "An error occurred while reading the Berksfile: #{e.to_s}"
      end
      self
    end

    private

      def descendant_directory?(candidate, parent)
        hack = FileUtils::Entry_.new('/tmp')
        hack.send(:descendant_diretory?, candidate, parent)
      end

      def lockfile_present?
        File.exist?(Berkshelf::Lockfile::DEFAULT_FILENAME)
      end

      def write_lockfile(sources)
        Berkshelf::Lockfile.new(sources).write
      end
  end
end