require 'google/apis/sheets_v4'
class Form < ApplicationRecord
  # Hash to translate an index to a A1 notation. e.g. 1 => 'B', 27 => 'AA'
  COLUMN_INDEX_TO_LETTER = Hash.new {|hash,key| hash[key] = hash[key - 1].next }.merge({0 => "A"})

  belongs_to :user
  has_many :submissions, dependent: :destroy
  after_create :create_spreadsheet

  has_secure_token

  validates_presence_of :title

  def create_spreadsheet
    sheets = Google::Apis::SheetsV4::SheetsService.new
    sheets.authorization = user.google_authorization
    create_object = Google::Apis::SheetsV4::Spreadsheet.new(properties: { title: title})
    spreadsheet = sheets.create_spreadsheet(create_object)
    update(google_spreadsheet_id: spreadsheet.spreadsheet_id)
  end

  def spreadsheet_service
    @spreadsheet_service ||= Google::Apis::SheetsV4::SheetsService.new.tap do |s|
      s.authorization = user.google_authorization
    end
  end

  def header_values
    @header_values ||= begin
                         values = spreadsheet_service.get_spreadsheet_values(google_spreadsheet_id, 'A1:An').values
                         # if there are no headers yet, return an empty array
                         if values
                          values[0].map(&:strip)
                         else
                           []
                         end
                       end
  end

  def append(data)
    data = data.with_indifferent_access
    check_spreadsheed_headers!(data)

    values = header_values.map { |key| data[key] }
    range = "A1:A#{COLUMN_INDEX_TO_LETTER[values.length]}1"
    value_range = Google::Apis::SheetsV4::ValueRange.new(values: [values], major_dimension: 'ROWS')

    spreadsheet_service.append_spreadsheet_value(google_spreadsheet_id, range, value_range, value_input_option: 'USER_ENTERED')
  end

  def check_spreadsheed_headers!(data)
    missing_headers = data.keys.map { |k| k.to_s.strip } - header_values
    append_missing_headers(missing_headers) unless missing_headers.empty?
  end

  def append_missing_headers(missing_headers)
    start_column = COLUMN_INDEX_TO_LETTER[header_values.length]
    end_column = COLUMN_INDEX_TO_LETTER[header_values.length + missing_headers.length]
    range = "#{start_column}1:#{end_column}1"
    value_range = Google::Apis::SheetsV4::ValueRange.new(values: [missing_headers], major_dimension: 'ROWS')
    spreadsheet_service.update_spreadsheet_value(google_spreadsheet_id, range, value_range, value_input_option: 'USER_ENTERED')
    @header_values = nil # reset header values to refresh memoization on next access
  end

  def to_param
    token
  end

end