#  Phusion Passenger - https://www.phusionpassenger.com/
#  Copyright (c) 2010-2015 Phusion
#
#  "Phusion Passenger" is a trademark of Hongli Lai & Ninh Bui.
#
#  Permission is hereby granted, free of charge, to any person obtaining a copy
#  of this software and associated documentation files (the "Software"), to deal
#  in the Software without restriction, including without limitation the rights
#  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
#  copies of the Software, and to permit persons to whom the Software is
#  furnished to do so, subject to the following conditions:
#
#  The above copyright notice and this permission notice shall be included in
#  all copies or substantial portions of the Software.
#
#  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
#  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
#  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
#  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
#  THE SOFTWARE.

require 'thread'
PhusionPassenger.require_passenger_lib 'union_station/connection'
PhusionPassenger.require_passenger_lib 'union_station/transaction'
PhusionPassenger.require_passenger_lib 'utils'
PhusionPassenger.require_passenger_lib 'utils/lock'
PhusionPassenger.require_passenger_lib 'debug_logging'

module PhusionPassenger
  module UnionStation

    class Core
      RETRY_SLEEP = 0.2
      NETWORK_ERRORS = [Errno::EPIPE, Errno::ECONNREFUSED, Errno::ECONNRESET,
        Errno::EHOSTUNREACH, Errno::ENETDOWN, Errno::ENETUNREACH, Errno::ETIMEDOUT]

      include Utils
      include DebugLogging

      def self.new_from_options(options)
        if options["analytics"] && options["ust_router_address"]
          return new(options["ust_router_address"],
            options["ust_router_username"],
            options["ust_router_password"],
            options["node_name"])
        else
          return nil
        end
      end

      attr_accessor :max_connect_tries
      attr_accessor :reconnect_timeout

      def initialize(ust_router_address, username, password, node_name)
        @server_address = ust_router_address
        @username = username
        @password = password
        if node_name && !node_name.empty?
          @node_name = node_name
        else
          @node_name = `hostname`.strip
        end
        @random_dev = File.open("/dev/urandom")

        # This mutex protects the following instance variables, but
        # not the contents of @connection.
        @mutex = Mutex.new

        @connection = Connection.new(nil)
        if @server_address && local_socket_address?(@server_address)
          @max_connect_tries = 10
        else
          @max_connect_tries = 1
        end
        @reconnect_timeout = 1
        @next_reconnect_time = Time.utc(1980, 1, 1)
      end

      def clear_connection
        @mutex.synchronize do
          @connection.synchronize do
            @random_dev = File.open("/dev/urandom") if @random_dev.closed?
            @connection.unref
            @connection = Connection.new(nil)
          end
        end
      end

      def close
        @mutex.synchronize do
          @connection.synchronize do
            @random_dev.close
            @connection.unref
            @connection = nil
          end
        end
      end

      def new_transaction(group_name, category = :requests, union_station_key = "-")
        if !@server_address
          return Transaction.new
        elsif !group_name || group_name.empty?
          raise ArgumentError, "Group name may not be empty"
        end

        txn_id = (Core.current_time.to_i / 60).to_s(36)
        txn_id << "-#{random_token(11)}"

        Utils::Lock.new(@mutex).synchronize do |lock|
          if current_time < @next_reconnect_time
            return Transaction.new
          end

          Utils::Lock.new(@connection.mutex).synchronize do |connection_lock|
            if !@connection.connected?
              begin
                connect
                connection_lock.reset(@connection.mutex)
              rescue SystemCallError, IOError
                @connection.disconnect
                warn("Cannot connect to the UstRouter at #{@server_address}; " +
                  "retrying in #{@reconnect_timeout} second(s).")
                @next_reconnect_time = current_time + @reconnect_timeout
                return Transaction.new
              rescue Exception => e
                @connection.disconnect
                raise e
              end
            end

            begin
              @connection.channel.write("openTransaction",
                txn_id, group_name, "", category,
                Core.timestamp_string,
                union_station_key,
                true,
                true)
              result = @connection.channel.read
              if result != ["ok"]
                raise "Expected the UstRouter to respond with 'ok', but got #{result.inspect} instead"
              end
              return Transaction.new(@connection, txn_id)
            rescue SystemCallError, IOError
              @connection.disconnect
              warn("The UstRouter at #{@server_address}" <<
                " closed the connection; will reconnect in " <<
                "#{@reconnect_timeout} second(s).")
              @next_reconnect_time = current_time + @reconnect_timeout
              return Transaction.new
            rescue Exception => e
              @connection.disconnect
              raise e
            end
          end
        end
      end

      def continue_transaction(txn_id, group_name, category = :requests, union_station_key = "-")
        if !@server_address
          return Transaction.new
        elsif !txn_id || txn_id.empty?
          raise ArgumentError, "Transaction ID may not be empty"
        end

        Utils::Lock.new(@mutex).synchronize do |lock|
          if current_time < @next_reconnect_time
            return Transaction.new
          end

          Utils::Lock.new(@connection.mutex).synchronize do |connection_lock|
            if !@connection.connected?
              begin
                connect
                connection_lock.reset(@connection.mutex)
              rescue SystemCallError, IOError
                @connection.disconnect
                warn("Cannot connect to the UstRouter at #{@server_address}; " +
                  "retrying in #{@reconnect_timeout} second(s).")
                @next_reconnect_time = current_time + @reconnect_timeout
                return Transaction.new
              rescue Exception => e
                @connection.disconnect
                raise e
              end
            end

            begin
              @connection.channel.write("openTransaction",
                txn_id, group_name, "", category,
                Core.timestamp_string,
                union_station_key,
                true)
              return Transaction.new(@connection, txn_id)
            rescue SystemCallError, IOError
              @connection.disconnect
              warn("The UstRouter at #{@server_address}" <<
                " closed the connection; will reconnect in " <<
                "#{@reconnect_timeout} second(s).")
              @next_reconnect_time = current_time + @reconnect_timeout
              return Transaction.new
            rescue Exception => e
              @connection.disconnect
              raise e
            end
          end
        end
      end

    private
      RANDOM_CHARS = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
        'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
        'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9']

      def connect
        socket  = connect_to_server(@server_address)
        channel = MessageChannel.new(socket)

        result = channel.read
        if result.nil?
          raise EOFError
        elsif result.size != 2 || result[0] != "version"
          raise IOError, "The UstRouter didn't sent a valid version identifier"
        elsif result[1] != "1"
          raise IOError, "Unsupported UstRouter protocol version #{result[1]}"
        end

        channel.write_scalar(@username)
        channel.write_scalar(@password)

        result = channel.read
        if result.nil?
          raise EOFError
        elsif result[0] != "ok"
          raise SecurityError, result[0]
        end

        channel.write("init", @node_name)
        args = channel.read
        if !args
          raise Errno::ECONNREFUSED, "Cannot connect to UstRouter"
        elsif args.size != 1
          raise IOError, "UstRouter returned an invalid reply for the 'init' command"
        elsif args[0] == "server shutting down"
          raise Errno::ECONNREFUSED, "Cannot connect to UstRouter"
        elsif args[0] != "ok"
          raise IOError, "UstRouter returned an invalid reply for the 'init' command"
        end

        @connection.unref
        @connection = Connection.new(socket)
      rescue Exception => e
        socket.close if socket && !socket.closed?
        raise e
      end

      def random_token(length)
        token = ""
        @random_dev.read(length).each_byte do |c|
          token << RANDOM_CHARS[c % RANDOM_CHARS.size]
        end
        return token
      end

      def current_time
        return self.class.current_time
      end

      def self.current_time
        return Time.now
      end

      def self.timestamp_string(time = current_time)
        timestamp = time.to_i * 1_000_000 + time.usec
        return timestamp.to_s(36)
      end
    end

  end # module UnionStation
end # module PhusionPassenger
