class ElasticSearchFacetScanner

# File lib/elasticsearch_facet_scanner.rb, line 11
def initialize(url, field, size=100, max_retries = 5)
  @url = url
  @field = field
  @aggregation_name = "#{field}_terms"
  @size = size
  @max_retries = max_retries
  @has_more = true
  @total_request_time = 0.0
  @total_elasticsearch_time = 0.0
end

# File lib/elasticsearch_facet_scanner.rb, line 32
def each
  each_batch do |results|
    results.each do |result|
      yield result
    end
  end
end

# File lib/elasticsearch_facet_scanner.rb, line 22
def each_batch
  yield search

  while has_more?
    yield search
  end

  nil
end

# File lib/elasticsearch_facet_scanner.rb, line 40
def has_more?
  @has_more
end

# File lib/elasticsearch_facet_scanner.rb, line 84
def make_request(http, req)
  request_started_at = Time.now
  res = http.request(req)
  @total_request_time += (Time.now - request_started_at)
  data = JSON.parse(res.body)
  @total_elasticsearch_time += data['took']
  aggregation = data['aggregations'][@aggregation_name]
  @has_more = aggregation['sum_other_doc_count'] > 0
  @field_max_value = aggregation['buckets'].size > 0 ? aggregation['buckets'].last['key'] : nil
  aggregation['buckets']
rescue Net::ReadTimeout => e
  attempts ||= 0
  attempts += 1
  if attempts < @max_retries
    sleep([0.1, 0.2, 0.4, 1.0][attempts-1] || 1.0)
    retry
  end
  raise e
end

# File lib/elasticsearch_facet_scanner.rb, line 75
def search
  uri = URI(@url)
  http = Net::HTTP.new(uri.host, uri.port)
  req = Net::HTTP::Post.new(uri.request_uri, 'Content-Type' => 'application/json')
  req.body = (@field_max_value ? search_payload_with_range : search_payload).to_json

  make_request(http, req)
end

# File lib/elasticsearch_facet_scanner.rb, line 46
def search_payload
  {
    size: 0,
    aggs: {
      @aggregation_name => {
        terms: {
          field: @field,
          size: @size,
          order: {
            _term: :asc
          }
        }
      }
    }
  }
end

# File lib/elasticsearch_facet_scanner.rb, line 63
def search_payload_with_range
  search_payload.merge(
    query: {
      range: {
        @field => {
         gt:  @field_max_value
        }
      }
    }
  )
end