store_nested_param

# File actionpack/lib/action_dispatch/http/param_builder.rb, line 65
      def store_nested_param(params, name, v, depth, encoding_template = nil)
        raise ParamsTooDeepError if depth >= param_depth_limit

        if !name
          # nil name, treat same as empty string (required by tests)
          k = after = ""
        elsif depth == 0
          if ignore_leading_brackets || (ignore_leading_brackets.nil? && LEADING_BRACKETS_COMPAT)
            # Rack 2 compatible behavior, ignore leading brackets
            if name =~ /\A[\[\]]*([^\[\]]+)\]*/
              k = $1
              after = $' || ""

              if !ignore_leading_brackets && (k != $& || !after.empty? && !after.start_with?("["))
                ActionDispatch.deprecator.warn("Skipping over leading brackets in parameter name #{name.inspect} is deprecated and will parse differently in Rails 8.1 or Rack 3.0.")
              end
            else
              k = name
              after = ""
            end
          else
            # Start of parsing, don't treat [] or [ at start of string specially
            if start = name.index("[", 1)
              # Start of parameter nesting, use part before brackets as key
              k = name[0, start]
              after = name[start, name.length]
            else
              # Plain parameter with no nesting
              k = name
              after = ""
            end
          end
        elsif name.start_with?("[]")
          # Array nesting
          k = "[]"
          after = name[2, name.length]
        elsif name.start_with?("[") && (start = name.index("]", 1))
          # Hash nesting, use the part inside brackets as the key
          k = name[1, start - 1]
          after = name[start + 1, name.length]
        else
          # Probably malformed input, nested but not starting with [
          # treat full name as key for backwards compatibility.
          k = name
          after = ""
        end

        return if k.empty?

        if depth == 0 && String === v
          # We have to wait until we've found the top part of the name,
          # because that's what the encoding template is configured with
          if encoding_template && (designated_encoding = encoding_template[k]) && !v.frozen?
            v.force_encoding(designated_encoding)
          end

          # ... and we can't validate the encoding until after we've
          # applied any template override
          unless v.valid_encoding?
            raise InvalidParameterError, "Invalid encoding for parameter: #{v.scrub}"
          end
        end

        if after == ""
          if k == "[]" && depth != 0
            return (v || !ActionDispatch::Request::Utils.perform_deep_munge) ? [v] : []
          else
            params[k] = v
          end
        elsif after == "["
          params[name] = v
        elsif after == "[]"
          params[k] ||= []
          raise ParameterTypeError, "expected Array (got #{params[k].class.name}) for param `#{k}'" unless params[k].is_a?(Array)
          params[k] << v if v || !ActionDispatch::Request::Utils.perform_deep_munge
        elsif after.start_with?("[]")
          # Recognize x[][y] (hash inside array) parameters
          unless after[2] == "[" && after.end_with?("]") && (child_key = after[3, after.length - 4]) && !child_key.empty? && !child_key.index("[") && !child_key.index("]")
            # Handle other nested array parameters
            child_key = after[2, after.length]
          end
          params[k] ||= []
          raise ParameterTypeError, "expected Array (got #{params[k].class.name}) for param `#{k}'" unless params[k].is_a?(Array)
          if params_hash_type?(params[k].last) && !params_hash_has_key?(params[k].last, child_key)
            store_nested_param(params[k].last, child_key, v, depth + 1)
          else
            params[k] << store_nested_param(make_params, child_key, v, depth + 1)
          end
        else
          params[k] ||= make_params
          raise ParameterTypeError, "expected Hash (got #{params[k].class.name}) for param `#{k}'" unless params_hash_type?(params[k])
          params[k] = store_nested_param(params[k], after, v, depth + 1)
        end

        params
      end