# frozen_string_literal: true

require "json"
require "net/http"

require "provider/adapters/adapter"

class Provider
  module Adapters
    # Bank of Canada daily indicative rates. Current series starts 2017-01-03.
    # Legacy noon rates (2007-2017) are available under the LEGACY_NOON_RATES group with ~65 currencies.
    class BOC < Adapter
      BASE_URL = "https://www.bankofcanada.ca/valet/observations/group/FX_RATES_DAILY/json"
      def fetch(after: nil, upto: nil)
        params = { start_date: after }
        params[:end_date] = upto if upto
        fetch_rates(**params)
      end

      def parse(json)
        data = json.is_a?(String) ? JSON.parse(json) : json

        data["observations"].flat_map do |obs|
          date = Date.parse(obs["d"])
          extract_rates(obs).map do |foreign, rate|
            { date:, base: foreign, quote: "CAD", rate: }
          end
        end
      end

      private

      def fetch_rates(**params)
        url = URI(BASE_URL)
        url.query = URI.encode_www_form(params)

        parse(Net::HTTP.get(url))
      end

      def extract_rates(observation)
        observation.each_with_object({}) do |(series, data), rates|
          next unless series.start_with?("FX")

          iso = series.delete_prefix("FX").delete_suffix("CAD")
          rates[iso] = Float(data["v"])
        end
      end
    end
  end
end