class SpreadsheetParser
  # Based on file's extension opens file (used for importing)
  def self.open_spreadsheet(file)
    filename = file.original_filename
    file_path = file.path

    if file.class == Paperclip::Attachment && file.is_stored_on_s3?
      fa = file.fetch
      file_path = fa.path
    end

    case File.extname(filename)
    when '.csv'
      Roo::CSV.new(file_path, extension: :csv)
    when '.tsv'
      Roo::CSV.new(file_path, csv_options: { col_sep: "\t" })
    when '.txt'
      # This assumption is based purely on biologist's habits
      Roo::CSV.new(file_path, csv_options: { col_sep: "\t" })
    when '.xlsx'
      # Roo Excel parcel was replaced with Creek, but it can be enabled back,
      # just swap lines below. But only one can be enabled at the same time.
      # Roo::Excelx.new(file_path)
      Creek::Book.new(file_path).sheets[0]
    else
      raise TypeError
    end
  end

  def self.spreadsheet_enumerator(sheet)
    if sheet.is_a?(Roo::CSV)
      sheet
    elsif sheet.is_a?(Roo::Excelx)
      sheet.each_row_streaming
    else
      sheet.rows
    end
  end

  def self.first_two_rows(sheet)
    rows = spreadsheet_enumerator(sheet)
    header = []
    columns = []
    i = 1
    rows.each do |row|
      # Creek XLSX parser returns Hash of the row, Roo - Array
      row = row.is_a?(Hash) ? row.values.map(&:to_s) : row.map(&:to_s)
      header = row if i == 1 && row
      columns = row if i == 2 && row
      i += 1
      break if i > 2
    end
    return header, columns
  end
end