module MetricFu

  def self.graph
    @graph ||= Graph.new
  end

  class Graph

    attr_accessor :graphers

    def initialize
      self.graphers = []
    end

    def add(graph_type, graph_engine, output_directory = MetricFu::Io::FileSystem.directory('output_directory'))
      grapher = grapher_from_type_and_engine(graph_type, graph_engine)
      self.graphers.push grapher.new.tap{|g| g.output_directory = output_directory }
    rescue NameError => e
      mf_log "#{e.message} called in MetricFu::Graph.add with #{graph_type}"
    end


    def generate
      return if self.graphers.empty?
      mf_log "Generating graphs"
      generate_graphs_for_files
      graph!
    rescue NameError => e
      mf_log "#{e.message} called in MetricFu::Graph generate"
    end

    private

    def grapher_from_type_and_engine(graph_type, graph_engine)
      grapher_name = graph_type.to_s.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase } + graph_engine.to_s.capitalize + "Grapher"
      MetricFu.const_get(grapher_name)
    end
    def metric_files
      Dir[File.join(MetricFu::Io::FileSystem.directory('data_directory'), '*.yml')].sort
    end

    def generate_graphs_for_files
      metric_files.each do |metric_file|
        generate_graphs_for_file(metric_file)
      end
    end

    def generate_graphs_for_file(metric_file)
      mf_log "Generating graphs for #{metric_file}"
      date_parts = year_month_day_from_filename(metric_file)
      metrics = load_yaml_metric_file(metric_file)

      build_graph(metrics, "#{date_parts[:m]}/#{date_parts[:d]}")
    rescue NameError => e
      mf_log "#{e.message} called in MetricFu::Graph.generate with #{metric_file}"
    end

    def load_yaml_metric_file(metric_file)
      YAML.load(File.open(metric_file))
    end

    def build_graph(metrics, sortable_prefix)
      self.graphers.each do |grapher|
        grapher.get_metrics(metrics, sortable_prefix)
      end
    end

    def graph!
      self.graphers.each do |grapher|
        grapher.graph!
      end
    end

    def year_month_day_from_filename(path_to_file_with_date)
      date = path_to_file_with_date.match(/\/(\d+).yml$/)[1]
      {:y => date[0..3].to_i, :m => date[4..5].to_i, :d => date[6..7].to_i}
    end
  end
end