module AbsApi

# File lib/abs_api.rb, line 28
def fetch_population(row, fetch: nil)
  region = region_code_for(row)
  return nil if region[:code].empty?

  url = population_url(region_code: region[:code], region_type: region[:type])
  payload = if fetch
              JSON.parse(fetch.call(url))
            else
              RabbotHttp.fetch_json(url, headers: { "Accept" => ACCEPT })
            end
  parse_latest_observation(payload)
rescue StandardError
  nil
end

# File lib/abs_api.rb, line 60
def first_observation_value(observations)
  return nil unless observations.is_a?(Hash) && observations.any?

  _key, values = observations.first
  value = Array(values).first
  return nil if value.nil?

  value.to_i
end

# File lib/abs_api.rb, line 43
def parse_latest_observation(payload)
  return nil unless payload.is_a?(Hash)

  data_sets = payload.dig("data", "dataSets") || payload["dataSets"]
  return nil if data_sets.nil? || data_sets.empty?

  data_set = data_sets[0]
  value = first_observation_value(data_set["observations"])
  return value if value

  series = data_set["series"]
  return nil unless series.is_a?(Hash) && series.any?

  _series_key, entry = series.first
  first_observation_value(entry["observations"])
end

# File lib/abs_api.rb, line 15
def population_url(region_code:, region_type: "GCCSA")
  key = "#{MEASURE}.#{region_type}.#{region_code}.#{FREQ}"
  "#{BASE_URL}/#{DATAFLOW}/#{key}?format=jsondata&detail=dataonly&lastNObservations=1"
end

# File lib/abs_api.rb, line 20
def region_code_for(row)
  code = row["region_code"].to_s.strip
  code = row["sa4_code"].to_s.strip if code.empty?
  type = row["region_type"].to_s.strip
  type = "GCCSA" if type.empty?
  { code: code, type: type }
end