lib/glimmer/dsl/expression_handler.rb
# Copyright (c) 2007-2024 Andy Maleh
#
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# the following conditions:
#
# The above copyright notice and this permission notice shall be
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require 'glimmer/invalid_keyword_error'
module Glimmer
module DSL
# Expression handler for a Glimmer DSL specific expression
#
# Follows the Chain of Responsibility Design Pattern
#
# Handlers are configured in Glimmer::DSL in the right order
# to attempt handling Glimmer DSL interpretation calls
#
# Each handler knows the next handler in the chain of responsibility.
#
# If it handles successfully, it returns. Otherwise, it forwards to the next
# handler in the chain of responsibility
class ExpressionHandler
def initialize(expression)
@expression = expression
end
# Handles interpretation of Glimmer DSL expression if expression supports it
# If it succeeds, it returns the correct Glimmer DSL expression object
# Otherwise, it forwards to the next handler configured via `#next=` method
# If there is no handler next, then it raises an error
def handle(parent, keyword, *args, &block)
Glimmer::Config.logger.info {"Attempting to handle #{keyword} with #{@expression.class.name.split(":").last}"}
if @expression.can_interpret?(parent, keyword, *args, &block)
Glimmer::Config.logger.info {"#{@expression.class.name} will handle expression keyword #{keyword}"}
return @expression
elsif @next_expression_handler
return @next_expression_handler.handle(parent, keyword, *args, &block)
else
# TODO see if we need a better response here (e.g. dev mode error raising vs production mode silent failure)
message = "Glimmer keyword #{keyword} with args #{args} cannot be handled"
message += " inside parent #{parent}" if parent
message += "! Check the validity of the code."
raise InvalidKeywordError, message
end
end
# Sets the next handler in the expression handler chain of responsibility
def next=(next_expression_handler)
@next_expression_handler = next_expression_handler
end
end
end
end