#!/usr/bin/env ruby

require 'etc'
require 'logger'
require 'ipaddr'
require 'json'
require 'yaml'
require 'rack'
require 'metriks'
require 'metriks/reporter/graphite'

require 'dyndnsd/generator/bind'
require 'dyndnsd/updater/command_with_bind_zone'
require 'dyndnsd/responder/dyndns_style'
require 'dyndnsd/responder/rest_style'
require 'dyndnsd/database'
require 'dyndnsd/helper'
require 'dyndnsd/version'

module Dyndnsd
  def self.logger
    @logger
  end

  def self.logger=(logger)
    @logger = logger
  end

  class LogFormatter
    def call(lvl, time, progname, msg)
      "[%s] %-5s %s\n" % [Time.now.strftime('%Y-%m-%d %H:%M:%S'), lvl, msg.to_s]
    end
  end

  class Daemon
    def initialize(config, db, updater)
      @users = config['users']
      @domain = config['domain']
      @db = db
      @updater = updater

      @db.load
      @db['serial'] ||= 1
      @db['hosts'] ||= {}
      (@db.save; @updater.update(@db)) if @db.changed?
    end

    def is_authorized?(username, password)
      allow = ((@users.has_key? username) and (@users[username]['password'] == password))
      if not allow
        Dyndnsd.logger.warn "Login failed for #{username}"
        Metriks.meter('requests.auth_failed').mark
      end
      allow
    end

    def call(env)
      return [422, {'X-DynDNS-Response' => 'method_forbidden'}, []] if env["REQUEST_METHOD"] != "GET"
      return [422, {'X-DynDNS-Response' => 'not_found'}, []] if env["PATH_INFO"] != "/nic/update"

      handle_dyndns_request(env)
    end

    def self.run!
      if ARGV.length != 1
        puts "Usage: dyndnsd config_file"
        exit 1
      end

      config_file = ARGV[0]

      if not File.file?(config_file)
        puts "Config file not found!"
        exit 1
      end

      puts "DynDNSd version #{Dyndnsd::VERSION}"
      puts "Using config file #{config_file}"

      config = YAML::load(File.open(config_file, 'r') { |f| f.read })

      setup_logger(config)

      Dyndnsd.logger.info "Starting..."

      # drop priviliges as soon as possible
      # NOTE: first change group than user
      Process::Sys.setgid(Etc.getgrnam(config['group']).gid) if config['group']
      Process::Sys.setuid(Etc.getpwnam(config['user']).uid) if config['user']

      setup_traps()

      setup_monitoring(config)

      setup_rack(config)
    end

    private

    def extract_v4_and_v6_address(env, params)
      return [] if not params["myip"]
      begin
        IPAddr.new(params["myip"], Socket::AF_INET)
        IPAddr.new(params["myip6"], Socket::AF_INET6)
        [params["myip"], params["myip6"]]
      rescue ArgumentError
        []
      end
    end

    def extract_myips(env, params)
      # require presence of myip parameter as valid IPAddr (v4) and valid myip6
      return extract_v4_and_v6_address(env, params) if params.has_key?("myip6")

      # check whether myip parameter has valid IPAddr
      return [params["myip"]] if params.has_key?("myip") and Helper.is_ip_valid?(params["myip"])

      # check whether X-Real-IP header has valid IPAddr
      return [env["HTTP_X_REAL_IP"]] if env.has_key?("HTTP_X_REAL_IP") and Helper.is_ip_valid?(env["HTTP_X_REAL_IP"])

      # fallback value, always present
      [env["REMOTE_ADDR"]]
    end

    def process_changes(hostnames, myips)
      changes = []
      hostnames.each do |hostname|
        # myips order is always deterministic
        if (not @db['hosts'].include? hostname) or (@db['hosts'][hostname] != myips)
          @db['hosts'][hostname] = myips
          changes << :good
          Metriks.meter('requests.good').mark
        else
          changes << :nochg
          Metriks.meter('requests.nochg').mark
        end
      end
      changes
    end

    def update_db()
      @db['serial'] += 1
      Dyndnsd.logger.info "Committing update ##{@db['serial']}"
      @db.save
      @updater.update(@db)
      Metriks.meter('updates.committed').mark
    end

    def handle_dyndns_request(env)
      params = Rack::Utils.parse_query(env["QUERY_STRING"])

      # require hostname parameter
      return [422, {'X-DynDNS-Response' => 'hostname_missing'}, []] if not params["hostname"]

      hostnames = params["hostname"].split(',')

      # check for invalid hostnames
      invalid_hostnames = hostnames.select { |hostname| not Helper.is_fqdn_valid?(hostname, @domain) }
      return [422, {'X-DynDNS-Response' => 'hostname_malformed'}, []] if invalid_hostnames.any?

      user = env["REMOTE_USER"]

      # check for hostnames that the user does not own
      forbidden_hostnames = hostnames - @users[user]['hosts']
      return [422, {'X-DynDNS-Response' => 'host_forbidden'}, []] if forbidden_hostnames.any?

      myips = extract_myips(env, params)

      # require at least one IP to update
      return [422, {'X-DynDNS-Response' => 'host_forbidden'}, []] if myips.empty?

      Metriks.meter('requests.valid').mark
      Dyndnsd.logger.info "Request to update #{hostnames} to #{myips} for user #{user}"

      changes = process_changes(hostnames, myips)

      update_db if @db.changed?

      [200, {'X-DynDNS-Response' => 'success'}, [changes, myips]]
    end

    # SETUP

    def self.setup_logger(config)
      if config['logfile']
        Dyndnsd.logger = Logger.new(config['logfile'])
      else
        Dyndnsd.logger = Logger.new(STDOUT)
      end

      Dyndnsd.logger.progname = "dyndnsd"
      Dyndnsd.logger.formatter = LogFormatter.new
    end

    def self.setup_traps()
      Signal.trap('INT') do
        Dyndnsd.logger.info "Quitting..."
        Rack::Handler::WEBrick.shutdown
      end
      Signal.trap('TERM') do
        Dyndnsd.logger.info "Quitting..."
        Rack::Handler::WEBrick.shutdown
      end
    end

    def self.setup_monitoring(config)
      # configure metriks
      if config['graphite']
        host = config['graphite']['host'] || 'localhost'
        port = config['graphite']['port'] || 2003
        options = {}
        options[:prefix] = config['graphite']['prefix'] if config['graphite']['prefix']
        reporter = Metriks::Reporter::Graphite.new(host, port, options)
        reporter.start
      else
        reporter = Metriks::Reporter::ProcTitle.new
        reporter.add 'good', 'sec' do
          Metriks.meter('requests.good').mean_rate
        end
        reporter.add 'nochg', 'sec' do
          Metriks.meter('requests.nochg').mean_rate
        end
        reporter.start
      end
    end

    def self.setup_rack(config)
      # configure daemon
      db = Database.new(config['db'])
      updater = Updater::CommandWithBindZone.new(config['domain'], config['updater']['params']) if config['updater']['name'] == 'command_with_bind_zone'
      daemon = Daemon.new(config, db, updater)

      # configure rack
      app = Rack::Auth::Basic.new(daemon, "DynDNS", &daemon.method(:is_authorized?))

      if config['responder'] == 'RestStyle'
        app = Responder::RestStyle.new(app)
      else
        app = Responder::DynDNSStyle.new(app)
      end

      Rack::Handler::WEBrick.run app, :Host => config['host'], :Port => config['port']
    end
  end
end