athityakumar/daru-io

require 'daru/io/base'

module Daru
  module IO
    module Importers
      # Base Importer Class that contains generic helper methods, to be
      # used by other Importers via inheritence
      class Base < Daru::IO::Base
        # Guesses the `Daru::DataFrame` from the parsed set of key-value pairs.
        #
        # @param keys [Array] A set of keys from given key-value pairs
        # @param vals [Array] A set of values from given key-value pairs
        #
        # @example When key-value pairs contains values that is Array of Hashes
        #   Daru::IO::Importers::Base.guess_parse([:a], [[{ x: 1, y: 2 },{ x: 3, y: 4 }]])
        #
        #   #=> #<Daru::DataFrame(2x2)>
        #   #      x   y
        #   #  0   1   2
        #   #  1   3   4
        #
        # @example When key-value pairs contains values that is Arrays
        #   Daru::IO::Importers::Base.guess_parse([:x, :y], [[1,3], [2,4]])
        #
        #   #=> #<Daru::DataFrame(2x2)>
        #   #      x   y
        #   #  0   1   2
        #   #  1   3   4
        #
        # @example When key-value pairs contains Array of keys contain value Hashes
        #   Daru::IO::Importers::Base.guess_parse([:a, :b], [{ x: 1, y: 2 }, { x: 3, y: 4 }])
        #
        #   #=> #<Daru::DataFrame(2x2)>
        #   #      x   y
        #   #  a   1   2
        #   #  b   3   4
        def self.guess_parse(keys, vals)
          case vals.first
          when Array
            case vals.first.first
            when Hash then Daru::DataFrame.new(vals.flatten)
            else Daru::DataFrame.rows(vals.transpose, order: keys)
            end
          when Hash then Daru::DataFrame.new(vals.flatten, index: keys)
          end
        end

        # Adds the `from` class method to all inheriting children Importer classes, which
        # calls corresponding Importer's `initialize` and instance method `from`.
        def self.from(relation)
          new.from(relation)
        end

        # Adds the `read` class method to all inheriting children Importer classes, which
        # calls corresponding Importer's `initialize` and instance method `read`.
        def self.read(path)
          new.read(path)
        end
      end
    end
  end
end