require 'csv_generator/version'

class CsvGenerator
  attr_reader :io

  class << self
    def generate(path, options = {}, &block)
      mode = options[:mode] || 'w'
      permission = options[:permission] || 0644

      File.open(path, mode, permission) do |io|
        with io, options, &block
      end
    end

    def with(io, options = {})
      generator = new(io, options)

      yield generator if block_given?
      generator
    end
  end

  def initialize(io, options = {})
    @io = io
    @options = options
  end

  def <<(row_values)
    io.write row_generator.generate(row_values)
  end

  private

  def row_generator
    @row_generator ||= RowGenerator.new(@options)
  end

  class RowGenerator
    KNOWN_OPTIONS = %i(line_separator field_separator quote_charactor).freeze

    attr_reader(*KNOWN_OPTIONS)
    attr_reader :escaped_quote

    def initialize(options = {})
      default_config.merge(filter_options options).each do |k, v|
        instance_variable_set :"@#{k}", v
      end

      @escaped_quote = quote_charactor * 2
    end

    private

    def filter_options(hash)
      hash.select { |k, _| KNOWN_OPTIONS.include? k }
    end

    def default_config
      {
        line_separator: "\r\n",
        field_separator: ',',
        quote_charactor: '"',
      }
    end

    def escape_quote_character(c)
      c * 2
    end

    public

    def generate(row_values)
      row_values.map { |value| stringify value }.join(field_separator) + line_separator
    end

    private

    def stringify(value)
      case value
      when nil
        ''
      when String
        quote value
      else
        value
      end
    end

    def quote(str)
      escaped_string = str.gsub quote_charactor, escaped_quote
      %("#{escaped_string}")
    end
  end
end