namespace :exchange_rates do
  desc "Fetch exchange rates from openexchangerates.org"
  task sync: :environment do
    app_id = ENV["OPEN_EXCHANGE_APP_ID"]
    MININUM_DATE_RANGE = 30.days
    MAXIMUM_DATE_RANGE = 120.days

    # First, check what plan the user is on at OXR
    # If the user is on the Developer plan, we can only fetch exchange rates for the past 30 days and must use the historical endpoint
    account_check = Faraday.get("https://openexchangerates.org/api/usage.json") do |req|
      req.params["app_id"] = app_id
    end
    account_details = JSON.parse(account_check.body)
    quota_limit = account_details["data"]["usage"]["requests_quota"]

    if quota_limit <= 10000
      # First loop through all Currency records and fetch exchange rates for each, but use the historical endpoint, which only allows fetching one day at a time. For each currency, set the base currency to the currency's iso_code and the symbols to all other currencies' iso_codes
      Currency.all.each do |currency|
        (Date.today - MININUM_DATE_RANGE).upto(Date.today) do |date|
          response = Faraday.get("https://openexchangerates.org/api/historical/#{date}.json") do |req|
            req.params["app_id"] = app_id
            req.params["base"] = currency.iso_code
            req.params["symbols"] = Currency.where.not(iso_code: currency.iso_code).pluck(:iso_code).join(",")
          end

          if response.success?
            rates = JSON.parse(response.body)["rates"]

            rates.each do |currency_iso_code, value|
              ExchangeRate.find_or_create_by(date: date, base_currency: currency.iso_code, converted_currency: currency_iso_code) do |exchange_rate|
                exchange_rate.rate = value
              end
              puts "#{currency.iso_code} to #{currency_iso_code} on #{date}: #{value}"
            end
          else
            puts "Failed to fetch exchange rates for #{currency.iso_code} on #{date}: #{response.status}"
          end
        end
      end
    else
      # Use Faraday to make a request openexchangerates.org time series endpoint
      # Use the response to create or update exchange rates in the database
      url = "https://openexchangerates.org/api/time-series.json"
      start_date = (Date.today - MAXIMUM_DATE_RANGE).to_s
      end_date = Date.today.to_s

      # Loop through all Currency records and fetch exchange rates for each
      Currency.all.each do |currency|
        start_period = Date.parse(start_date)
        end_period = Date.parse(end_date)

        while start_period < end_period
          current_end_date = [ start_period + 30.days, end_period ].min

          response = Faraday.get(url) do |req|
            req.params["app_id"] = app_id
            req.params["start"] = start_period.to_s
            req.params["end"] = current_end_date.to_s
            req.params["base"] = currency.iso_code
            req.params["symbols"] = Currency.where.not(iso_code: currency.iso_code).pluck(:iso_code).join(",")
          end

          if response.success?
            rates = JSON.parse(response.body)["rates"]

            rates.each do |date, rate|
              rate.each do |currency_iso_code, value|
                ExchangeRate.find_or_create_by(date: date, base_currency: currency.iso_code, converted_currency: currency_iso_code) do |exchange_rate|
                  exchange_rate.rate = value
                end
                puts "#{currency.iso_code} to #{currency_iso_code} on #{date}: #{value}"
              end
            end
          else
            puts "Failed to fetch exchange rates for period #{start_period} to #{current_end_date}: #{response.status}"
          end

          start_period = current_end_date + 1.day
        end
      end
    end
  end
end