# encoding: utf-8

require 'forwardable'
require 'one_apm/support/dotted_hash'
require 'one_apm/configuration/yaml_source'
require 'one_apm/configuration/server_source'
require 'one_apm/configuration/manual_source'
require 'one_apm/configuration/default_source'
require 'one_apm/configuration/environment_source'
require 'one_apm/configuration/high_security_source'

module OneApm
  module Configuration

    MASK_DEFAULTS = {
      :'thread_profiler' =>         Proc.new { !OneApm::Agent::Threading::BacktraceService.is_supported? },
      :'thread_profiler.enabled' => Proc.new { !OneApm::Agent::Threading::BacktraceService.is_supported? }
    }

    class Manager

      attr_reader :stripped_exceptions_whitelist

      def initialize
        reset_to_defaults
        @callbacks = Hash.new {|hash,key| hash[key] = [] }

        register_callback(:'strip_exception_messages.whitelist') do |whitelist|
          if whitelist
            @stripped_exceptions_whitelist = parse_constant_list(whitelist).compact
          else
            @stripped_exceptions_whitelist = []
          end
        end
      end

      # Defining these explicitly saves object allocations that we incur
      # if we use Forwardable and def_delegators.
      def [](key)
        @cache[key]
      end

      def has_key?(key)
        @cache.has_key?[key]
      end

      def keys
        @cache.keys
      end

      def add_config_for_testing(source, level=0)
        raise 'Invalid config type for testing' unless [Hash, OneApm::Support::DottedHash].include?(source.class)
        invoke_callbacks(:add, source)
        @configs_for_testing << [source.freeze, level]
        reset_cache
        log_config(:add, source)
      end

      def remove_config_type(sym)
        source = case sym
        when :high_security then @high_security_source
        when :environment   then @environment_source
        when :server        then @server_source
        when :manual        then @manual_source
        when :yaml          then @yaml_source
        when :default       then @default_source
        end

        remove_config(source)
      end

      def remove_config(source)
        case source
        when HighSecuritySource then @high_security_source = nil
        when EnvironmentSource  then @environment_source   = nil
        when ServerSource       then @server_source        = nil
        when ManualSource       then @manual_source        = nil
        when YamlSource         then @yaml_source          = nil
        when DefaultSource      then @default_source       = nil
        else
          @configs_for_testing.delete_if {|src,lvl| src == source}
        end

        reset_cache
        invoke_callbacks(:remove, source)
        log_config(:remove, source)
      end

      def replace_or_add_config(source)
        source.freeze
        was_finished = finished_configuring?

        invoke_callbacks(:add, source)
        case source
        when HighSecuritySource then @high_security_source = source
        when EnvironmentSource  then @environment_source   = source
        when ServerSource       then @server_source        = source
        when ManualSource       then @manual_source        = source
        when YamlSource         then @yaml_source          = source
        when DefaultSource      then @default_source       = source
        else
          OneApm::Manager.logger.warn("Invalid config format; config will be ignored: #{source}")
        end

        reset_cache
        log_config(:add, source)

        notify_finished_configuring if !was_finished && finished_configuring?
      end

      def source(key)
        config_stack.each do |config|
          if config.respond_to?(key.to_sym) || config.has_key?(key.to_sym)
            return config
          end
        end
      end

      def fetch(key)
        config_stack.each do |config|
          next unless config
          accessor = key.to_sym

          if config.has_key?(accessor)
            evaluated = evaluate_procs(config[accessor])

            begin
              return apply_transformations(accessor, evaluated)
            rescue
              next
            end
          end
        end

        nil
      end

      def evaluate_procs(value)
        if value.respond_to?(:call)
          instance_eval(&value)
        else
          value
        end
      end

      def apply_transformations(key, value)
        if transform = transform_from_default(key)
          begin
            transform.call(value)
          rescue => e
            OneApm::Manager.logger.error("Error applying transformation for #{key}, falling back to #{value}.", e)
            raise e
          end
        else
          value
        end
      end

      def transform_from_default(key)
        ::OneApm::Configuration::DefaultSource.transform_for(key)
      end

      def register_callback(key, &proc)
        @callbacks[key] << proc
        proc.call(@cache[key])
      end

      def invoke_callbacks(direction, source)
        return unless source
        source.keys.each do |key|

          if @cache[key] != source[key]
            @callbacks[key].each do |proc|
              if direction == :add
                proc.call(source[key])
              else
                proc.call(@cache[key])
              end
            end
          end
        end
      end

      def notify_finished_configuring
        OneApm::Manager.agent.events.notify(:finished_configuring)
      end

      def finished_configuring?
        !@server_source.nil?
      end

      def flattened
        config_stack.reverse.inject({}) do |flat,layer|
          thawed_layer = layer.to_hash.dup
          thawed_layer.each do |k,v|
            begin
              thawed_layer[k] = instance_eval(&v) if v.respond_to?(:call)
            rescue => e
              OneApm::Manager.logger.debug("#{e.class.name} : #{e.message} - when accessing config key #{k}")
              thawed_layer[k] = nil
            end
            thawed_layer.delete(:config)
          end
          flat.merge(thawed_layer.to_hash)
        end
      end

      def apply_mask(hash)
        MASK_DEFAULTS. \
          select {|_, proc| proc.call}. \
          each {|key, _| hash.delete(key) }
        hash
      end

      def to_collector_hash
        OneApm::Support::DottedHash.new(apply_mask(flattened)).to_hash.delete_if do |k, v|
          default = DEFAULTS[k]
          if default
            default[:local_only]
          else
            # In our tests, we add totally bogus configs, because testing.
            # In those cases, there will be no default. So we'll just let
            # them through.
            false
          end
        end
      end

      def app_names
        case OneApm::Manager.config[:app_name]
        when Array then OneApm::Manager.config[:app_name]
        when String then OneApm::Manager.config[:app_name].split(';')
        else []
        end
      end

      MALFORMED_LABELS_WARNING = "Skipping malformed labels configuration"
      PARSING_LABELS_FAILURE   = "Failure during parsing labels. Ignoring and carrying on with connect."

      MAX_LABEL_COUNT  = 64
      MAX_LABEL_LENGTH = 255

      def parsed_labels
        case OneApm::Manager.config[:labels]
        when String
          parse_labels_from_string
        else
          parse_labels_from_dictionary
        end
      rescue => e
        OneApm::Manager.logger.error(PARSING_LABELS_FAILURE, e)
        []
      end

      def parse_labels_from_string
        labels = OneApm::Manager.config[:labels]
        label_pairs = break_label_string_into_pairs(labels)
        make_label_hash(label_pairs, labels)
      end

      def break_label_string_into_pairs(labels)
        stripped_labels = labels.strip
        stripped_labels.split(';').map do |pair|
          pair.split(':').map(&:strip)
        end
      end

      def valid_label_pairs?(label_pairs)
        label_pairs.all? do |pair|
          pair.length == 2 && valid_label_item?(pair.first) && valid_label_item?(pair.last)
        end
      end

      def valid_label_item?(item)
        case item
        when String  then !item.empty?
        when Numeric then true
        when true    then true
        when false   then true
        else false
        end
      end

      def make_label_hash(pairs, labels = nil)
        # This can accept a hash, so force it down to an array of pairs first
        pairs = Array(pairs)

        unless valid_label_pairs?(pairs)
          OneApm::Manager.logger.warn("#{MALFORMED_LABELS_WARNING}: #{labels||pairs}")
          return []
        end

        pairs = limit_number_of_labels(pairs)
        pairs = remove_duplicates(pairs)
        pairs.map do |key, value|
          {
            'label_type'  => truncate(key),
            'label_value' => truncate(value.to_s, key)
          }
        end
      end

      def truncate(text, key=nil)
        if text.length > MAX_LABEL_LENGTH
          if key
            msg = "The value for the label '#{key}' is longer than the allowed #{MAX_LABEL_LENGTH} and will be truncated. Value = '#{text}'"
          else
            msg = "Label name longer than the allowed #{MAX_LABEL_LENGTH} will be truncated. Name = '#{text}'"
          end
          OneApm::Manager.logger.warn(msg)
          text[0..MAX_LABEL_LENGTH-1]
        else
          text
        end
      end

      def limit_number_of_labels(pairs)
        if pairs.length > MAX_LABEL_COUNT
          OneApm::Manager.logger.warn("Too many labels defined. Only taking first #{MAX_LABEL_COUNT}")
          pairs[0...64]
        else
          pairs
        end
      end

      # We only take the last value provided for a given label type key
      def remove_duplicates(pairs)
        grouped_by_type = pairs.group_by(&:first)
        grouped_by_type.values.map(&:last)
      end

      def parse_labels_from_dictionary
        make_label_hash(OneApm::Manager.config[:labels])
      end

      # Generally only useful during initial construction and tests
      def reset_to_defaults
        @high_security_source = nil
        @environment_source   = EnvironmentSource.new
        @server_source        = nil
        @manual_source        = nil
        @yaml_source          = nil
        @default_source       = DefaultSource.new

        @configs_for_testing  = []

        reset_cache
      end

      def reset_cache
        @cache = Hash.new {|hash,key| hash[key] = self.fetch(key) }
      end

      def log_config(direction, source)
        # Just generating this log message (specifically calling
        # flattened.inspect) is expensive enough that we don't want to do it
        # unless we're actually going to be logging the message based on our
        # current log level.
        OneApm::Manager.logger.debug do
          "Updating config (#{direction}) from #{source.class}. Results: #{flattened.inspect}"
        end
      end

      def delete_all_configs_for_testing
        @high_security_source = nil
        @environment_source   = nil
        @server_source        = nil
        @manual_source        = nil
        @yaml_source          = nil
        @default_source       = nil
        @configs_for_testing  = []
      end

      def num_configs_for_testing
        config_stack.size
      end

      def config_classes_for_testing
        config_stack.map(&:class)
      end

      private

      def config_stack
        stack = [
          @high_security_source,
          @environment_source,
          @server_source,
          @manual_source,
          @yaml_source,
          @default_source
        ]

        stack.compact!

        @configs_for_testing.each do |config, at_start|
          if at_start
            stack.insert(0, config)
          else
            stack.push(config)
          end
        end

        stack
      end

      def parse_constant_list(list)
        list.split(/\s*,\s*/).map do |class_name|
          const = constantize(class_name)

          unless const
            OneApm::Manager.logger.warn "Configuration referenced undefined constant: #{class_name}"
          end

          const
        end
      end

      def constantize(class_name)
        namespaces = class_name.split('::')

        namespaces.inject(Object) do |namespace, name|
          return unless namespace
          namespace.const_get(name) if namespace.const_defined?(name)
        end
      end
    end
  end
end