require 'json/pure'

module LeapCli
  module Config

    #
    # A class to manage all the objects in all the configuration files.
    #
    class Manager

      attr_reader :services, :tags, :nodes, :provider, :common

      ##
      ## IMPORT EXPORT
      ##

      #
      # load .json configuration files
      #
      def load(provider_dir=Path.provider)
        @services = load_all_json(Path.named_path([:service_config, '*'], provider_dir))
        @tags     = load_all_json(Path.named_path([:tag_config, '*'],     provider_dir))
        @nodes    = load_all_json(Path.named_path([:node_config, '*'],    provider_dir))
        @common   = load_json(Path.named_path(:common_config,   provider_dir))
        @provider = load_json(Path.named_path(:provider_config, provider_dir))

        Util::assert!(@provider, "Failed to load provider.json")
        Util::assert!(@common, "Failed to load common.json")

        @nodes.each do |name, node|
          @nodes[name] = apply_inheritance(node)
        end
      end

      #
      # save compiled hiera .yaml files
      #
      def export(dir=Path.named_path(:hiera_dir))
        existing_files = Dir.glob(dir + '/*.yaml')
        updated_files = []
        @nodes.each do |name, node|
          filepath = "#{dir}/#{name}.yaml"
          updated_files << filepath
          Util::write_file!(filepath, node.dump)
        end
        (existing_files - updated_files).each do |filepath|
          Util::remove_file!(filepath)
        end
      end

      ##
      ## FILTERING
      ##

      #
      # returns a node list consisting only of nodes that satisfy the filter criteria.
      #
      # filter: condition [condition] [condition] [+condition]
      # condition: [node_name | service_name | tag_name]
      #
      # if conditions is prefixed with +, then it works like an AND. Otherwise, it works like an OR.
      #
      def filter(filters)
        if filters.empty?
          return nodes
        end
        if filters[0] =~ /^\+/
          # don't let the first filter have a + prefix
          filters[0] = filters[0][1..-1]
        end

        node_list = Config::ObjectList.new
        filters.each do |filter|
          if filter =~ /^\+/
            keep_list = nodes_for_name(filter[1..-1])
            node_list.delete_if do |name, node|
              if keep_list[name]
                false
              else
                true
              end
            end
          else
            node_list.merge!(nodes_for_name(filter))
          end
        end
        return node_list
      end

      #
      # same as filter(), but exits if there is no matching nodes
      #
      def filter!(filters)
        node_list = filter(filters)
        Util::assert! node_list.any?, "Could not match any nodes from '#{filters}'"
        return node_list
      end

      #
      # returns a single Config::Object that corresponds to a Node.
      #
      def node(name)
        nodes[name]
      end

      private

      def load_all_json(pattern)
        results = Config::ObjectList.new
        Dir.glob(pattern).each do |filename|
          obj = load_json(filename)
          if obj
            name = File.basename(filename).sub(/\.json$/,'')
            obj['name'] ||= name
            results[name] = obj
          end
        end
        results
      end

      def load_json(filename)
        #
        # read file, strip out comments
        # (File.read(filename) would be faster, but we like ability to have comments)
        #
        buffer = StringIO.new
        File.open(filename) do |f|
          while (line = f.gets)
            next if line =~ /^\s*#/
            buffer << line
          end
        end

        # parse json
        begin
          hash = JSON.parse(buffer.string, :object_class => Hash, :array_class => Array) || {}
        rescue SyntaxError => exc
          log0 'Error in file "%s":' % filename
          log0 exc.to_s
          return nil
        end
        object = Config::Object.new(self)
        object.deep_merge!(hash)
        return object
      end

      #
      # remove all the nesting from a hash.
      #
      # def flatten_hash(input = {}, output = {}, options = {})
      #   input.each do |key, value|
      #     key = options[:prefix].nil? ? "#{key}" : "#{options[:prefix]}#{options[:delimiter]||"_"}#{key}"
      #     if value.is_a? Hash
      #       flatten_hash(value, output, :prefix => key, :delimiter => options[:delimiter])
      #     else
      #       output[key]  = value
      #     end
      #   end
      #   output.replace(input)
      #   output
      # end

      #
      # makes a node inherit options from appropriate the common, service, and tag json files.
      #
      def apply_inheritance(node)
        new_node = Config::Object.new(self)
        name = node.name

        # inherit from common
        new_node.deep_merge!(@common)

        # inherit from services
        if node['services']
          node['services'].to_a.sort.each do |node_service|
            service = @services[node_service]
            if service.nil?
              log0('Error in node "%s": the service "%s" does not exist.' % [node['name'], node_service])
            else
              new_node.deep_merge!(service)
              service.node_list.add(name, new_node)
            end
          end
        end

        # inherit from tags
        if node['tags']
          node['tags'].to_a.sort.each do |node_tag|
            tag = @tags[node_tag]
            if tag.nil?
              log0('Error in node "%s": the tag "%s" does not exist.' % [node['name'], node_tag])
            else
              new_node.deep_merge!(tag)
              tag.node_list.add(name, new_node)
            end
          end
        end

        # inherit from node
        new_node.deep_merge!(node)
        return new_node
      end

      #
      # returns a set of nodes corresponding to a single name, where name could be a node name, service name, or tag name.
      #
      def nodes_for_name(name)
        if node = self.nodes[name]
          Config::ObjectList.new(node)
        elsif service = self.services[name]
          service.node_list
        elsif tag = self.tags[name]
          tag.node_list
        end
      end

    end
  end
end