require "socket"
begin
  require "mongo"
rescue LoadError
  raise LoadError,
        'Gem mongo is required for logging to MongoDB. Please add the gem "mongo" v2.0 or greater to your Gemfile.'
end

module SemanticLogger
  module Appender
    # The Mongo Appender for the SemanticLogger
    #
    # Mongo Document Schema:
    #    _id:         ObjectId("4d9cbcbf7abb3abdaf9679cd"),
    #    time:        ISODate("2011-04-06T19:19:27.006Z"),
    #    host:        'Name of the host on which this log entry originated',
    #    application  'Name of application or service logging the data - clarity_base, nginx, tomcat',
    #    pid:         process id
    #    thread:      "name or id of thread",
    #    name:        "com.clarity.MyClass",
    #    level:       'trace|debug|info|warn|error|fatal'
    #    level_index: 0|1|2|3|4|5
    #    message:     "Message supplied to the logging call",
    #    duration:    'human readable duration',
    #    duration_ms: ms,
    #    tags:        ["id1", "id2"]
    #    exception: {
    #      name:        'MyException',
    #      message:     'Invalid value',
    #      stack_trace: []
    #    }
    #    # When a backtrace is captured
    #    file_name:   'my_class.rb'
    #    line_number: 42
    #
    # Example:
    #   require 'semantic_logger'
    #
    #   client   = Mongo::MongoClient.new
    #   database = client['test']
    #
    #   appender = SemanticLogger::Appender::MongoDB.new(
    #     db:              database,
    #     collection_size: 1024**3 # 1.gigabyte
    #   )
    #   SemanticLogger.add_appender(appender: appender)
    #
    #   logger = SemanticLogger['Example']
    #
    #   # Log some messages
    #   logger.info 'This message is written to mongo as a document'
    class MongoDB < SemanticLogger::Subscriber
      attr_reader :client, :collection

      # Create a MongoDB Appender instance
      #
      # Parameters:
      #   uri: [String]
      #     Mongo connection string.
      #     Example:
      #       mongodb://127.0.0.1:27017/test
      #
      #   collection_name: [String]
      #     Name of the collection to store log data in
      #     Default: semantic_logger
      #
      #   write_concern: [Integer]
      #     Write concern to use
      #     see: http://docs.mongodb.org/manual/reference/write-concern/
      #     Default: 0
      #
      #   collection_size: [Integer]
      #     The size of the MongoDB capped collection to create in bytes
      #     Default: 1 GB
      #     Examples:
      #       Prod: 25GB (.5GB per day across 4 servers over 10 days)
      #       Dev: .5GB
      #       Test: File
      #       Release: 4GB
      #
      #   collection_max: [Integer]
      #     Maximum number of log entries that the capped collection will hold.
      #     Default: no max limit
      #
      #   level: [:trace | :debug | :info | :warn | :error | :fatal]
      #     Override the log level for this appender.
      #     Default: SemanticLogger.default_level
      #
      #   formatter: [Object|Proc|Symbol]
      #     An instance of a class that implements #call, or a Proc to be used to format
      #     the output from this appender
      #     Default: Use the built-in formatter (See: #call)
      #
      #   filter: [Regexp|Proc]
      #     RegExp: Only include log messages where the class name matches the supplied.
      #     regular expression. All other messages will be ignored.
      #     Proc: Only include log messages where the supplied Proc returns true
      #           The Proc must return true or false.
      #
      #   host: [String]
      #     Name of this host to appear in log messages.
      #     Default: SemanticLogger.host
      #
      #   application: [String]
      #     Name of this application to appear in log messages.
      #     Default: SemanticLogger.application
      def initialize(uri:,
                     collection_name: "semantic_logger",
                     write_concern: 0,
                     collection_size: 1024**3,
                     collection_max: nil,
                     **args,
                     &block)
        @client          = Mongo::Client.new(uri, logger: logger)
        @collection_name = collection_name
        @options         = {
          capped: true,
          size:   collection_size,
          write:  {w: write_concern}
        }
        @options[:max] = collection_max if collection_max

        reopen

        # Create the collection and necessary indexes
        create_indexes

        super(**args, &block)
      end

      # After forking an active process call #reopen to re-open
      # open the handles to resources
      def reopen
        @collection = client[@collection_name, @options]
      end

      # Create the required capped collection.
      #
      # Features of capped collection:
      # * No indexes by default (not even on _id)
      # * Documents cannot be deleted,
      # * Document updates cannot make them any larger
      # * Documents are always stored in insertion order
      #   * A find will always return the documents in their insertion order
      #
      # Creates an index based on tags to support faster searches.
      def create_indexes
        # Create Capped collection
        begin
          @collection.create
        rescue Mongo::Error::OperationFailure
          nil
        end

        @collection.indexes.create_one(tags: 1)
      end

      # Purge all data from the capped collection by dropping the collection
      # and recreating it.
      # Also useful when the size of the capped collection needs to be changed
      def purge_all
        collection.drop
        reopen
        create_indexes
      end

      # Log the message to MongoDB
      def log(log)
        # Insert log entry into Mongo
        collection.insert_one(formatter.call(log, self))
        true
      end

      private

      def default_formatter
        SemanticLogger::Formatters::Raw.new
      end
    end
  end
end