#!/usr/bin/ruby

require "apache_log_regex"
require "file-tail"
require "json"

def categorise_uri(line)
  uri = line.split(" ")[1]

  case uri
  when %r{api/0\.6/map} then :map
  when %r{api/0\.6/changeset/[0-9]*/upload} then :upload
  when %r{api/0\.6/amf} then :amf
  when %r{api/0\.6/(node|way|relation)/[0-9]*/history} then :history
  when %r{api/0\.6/(node|way|relation)/[0-9]*/full} then :full
  when %r{api/0\.6/trackpoints} then :trkpts
  when %r{api/0\.6/} then :other
  else :web
  end
end

parser = ApacheLogRegex.new('%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\" %Dus %{UNIQUE_ID}e %{SSL_PROTOCOL}x %{SSL_CIPHER}x')
last_write = Time.now

statistics = {
  :status => Hash.new(0),
  :uri => Hash.new(0),
  :count => Hash.new(0),
  :bytes => Hash.new(0),
  :seconds => Hash.new(0.0),
  :ssl => Hash.new(0)
}

File::Tail::Logfile.tail("/var/log/apache2/access.log") do |line|
  begin
    hash = parser.parse(line)

    uri = categorise_uri(hash["%r"])
    status = hash["%>s"]
    bytes = hash["%O"].to_i
    seconds = hash["%Dus"].to_f / 1000000
    protocol = hash["%{SSL_PROTOCOL}x"]
    cipher = hash["%{SSL_CIPHER}x"]

    statistics[:status][status] += 1
    statistics[:uri][uri] += 1
    statistics[:count][[uri, status]] += 1
    statistics[:bytes][[uri, status]] += bytes
    statistics[:seconds][[uri, status]] += seconds
    statistics[:ssl][[protocol, cipher]] += 1 unless protocol == "-"
  rescue ApacheLogRegex::ParseError
    # nil
  end

  if Time.now - last_write > 10
    File.write("/srv/www.openstreetmap.org/rails/tmp/statistics.json", statistics.slice(:status, :uri).to_json)

    File.open("/var/lib/prometheus/node-exporter/api.tmp", "w") do |file|
      file.puts "# HELP api_call_count_total Number of calls by type and status"
      file.puts "# TYPE api_call_count_total counter"

      statistics[:count].each do |key, value|
        uri, status = key

        file.puts "api_call_count_total{uri=\"#{uri}\",status=\"#{status}\"} #{value}"
      end

      file.puts "# HELP api_call_bytes_total Number of bytes returned by type and status"
      file.puts "# TYPE api_call_bytes_total counter"

      statistics[:bytes].each do |key, value|
        uri, status = key

        file.puts "api_call_bytes_total{uri=\"#{uri}\",status=\"#{status}\"} #{value}"
      end

      file.puts "# HELP api_call_seconds_total Number of seconds returned by type and status"
      file.puts "# TYPE api_call_seconds_total counter"

      statistics[:seconds].each do |key, value|
        uri, status = key

        file.puts "api_call_seconds_total{uri=\"#{uri}\",status=\"#{status}\"} #{value}"
      end

      file.puts "# HELP api_call_ssl_total Number of calls by SSL protocol and cipher"
      file.puts "# TYPE api_call_ssl_total counter"

      statistics[:ssl].each do |key, value|
        protocol, cipher = key

        file.puts "api_call_ssl_total{protocol=\"#{protocol}\",cipher=\"#{cipher}\"} #{value}"
      end
    end

    File.rename("/var/lib/prometheus/node-exporter/api.tmp", "/var/lib/prometheus/node-exporter/api.prom")

    last_write = Time.now
  end
end