# frozen_string_literal: true

# Copyright The OpenTelemetry Authors
#
# SPDX-License-Identifier: Apache-2.0

module OpenTelemetry
  module Baggage
    # Operational Baggage Manager implementation
    class Manager
      BAGGAGE_KEY = OpenTelemetry::Baggage::Propagation::ContextKeys.baggage_key
      EMPTY_BAGGAGE = {}.freeze
      private_constant(:BAGGAGE_KEY, :EMPTY_BAGGAGE)

      # Used to chain modifications to baggage. The result is a
      # context with an updated baggage. If only a single
      # modification is being made to baggage, use the other
      # methods on +Manager+, if multiple modifications are being made, use
      # this one.
      #
      # @param [optional Context] context The context to update with with new
      #   modified baggage. Defaults to +Context.current+
      # @return [Context]
      def build(context: Context.current)
        builder = Builder.new(baggage_for(context).dup)
        yield builder
        context.set_value(BAGGAGE_KEY, builder.entries)
      end

      # Returns a new context with empty baggage
      #
      # @param [optional Context] context Context to clear baggage from. Defaults
      #   to +Context.current+
      # @return [Context]
      def clear(context: Context.current)
        context.set_value(BAGGAGE_KEY, EMPTY_BAGGAGE)
      end

      # Returns the corresponding baggage.entry (or nil) for key
      #
      # @param [String] key The lookup key
      # @param [optional Context] context The context from which to retrieve
      #   the key.
      #   Defaults to +Context.current+
      # @return [String]
      def value(key, context: Context.current)
        baggage_for(context)[key]&.value
      end

      # Returns the baggage
      #
      # @param [optional Context] context The context from which to retrieve
      #   the baggage.
      #   Defaults to +Context.current+
      # @return [Hash]
      def values(context: Context.current)
        baggage_for(context).transform_values(&:value)
      end

      # @api private
      def raw_entries(context: Context.current)
        baggage_for(context).dup.freeze
      end

      # Returns a new context with new key-value pair
      #
      # @param [String] key The key to store this value under
      # @param [String] value String value to be stored under key
      # @param [optional String] metadata This is here to store properties
      #   received from other W3C Baggage impelmentations but is not exposed in
      #   OpenTelemetry. This is condsidered private API and not for use by
      #   end-users.
      # @param [optional Context] context The context to update with new
      #   value. Defaults to +Context.current+
      # @return [Context]
      def set_value(key, value, metadata: nil, context: Context.current)
        new_baggage = baggage_for(context).dup
        new_baggage[key] = Entry.new(value, metadata)
        context.set_value(BAGGAGE_KEY, new_baggage)
      end

      # Returns a new context with value at key removed
      #
      # @param [String] key The key to remove
      # @param [optional Context] context The context to remove baggage
      #   from. Defaults to +Context.current+
      # @return [Context]
      def remove_value(key, context: Context.current)
        baggage = baggage_for(context)
        return context unless baggage.key?(key)

        new_baggage = baggage.dup
        new_baggage.delete(key)
        context.set_value(BAGGAGE_KEY, new_baggage)
      end

      private

      def baggage_for(context)
        context.value(BAGGAGE_KEY) || EMPTY_BAGGAGE
      end
    end
  end
end