# Copyright, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

module Build
	# A rule is a function with a specific set of input and output parameters, which can match against a given set of specific inputs and outputs. For example, there might be several rules for compiling, but the specific rules depend on the language being compiled.
	class Rule
		class Parameter
			def initialize(direction, name, options = {}, &block)
				@direction = direction
				@name = name
				
				@options = options
				
				@dynamic = block_given? ? Proc.new(&block) : nil
			end
			
			attr :direction
			attr :name
			
			attr :options
			
			def input?
				@direction == :input
			end
			
			def output?
				@direction == :output
			end
			
			def dynamic?
				@dynamic != nil
			end
			
			# Do we have a default value for this parameter?
			def default?
				@options.key?(:default)
			end
			
			def implicit?
				dynamic? and @options[:implicit]
			end
			
			# Optional parameters are those that are either defined as optional or implicit.
			def optional?
				@options[:optional] || implicit? || default?
			end
			
			def applicable? arguments
				value = arguments.fetch(@name) do
					# Value couldn't be found, if it wasn't optional, this parameter didn't apply:
					return optional?
				end
				
				# If a pattern is provided, we must match it.
				if pattern = @options[:pattern]
					return Array(value).all? {|item| pattern.match(item)}
				end
				
				return true
			end
			
			def compute(arguments, scope)
				if implicit?
					# Can be replaced if supplied:
					arguments[@name] || scope.instance_exec(arguments, &@dynamic)
				elsif dynamic?
					# Argument is optional:
					scope.instance_exec(arguments[@name], arguments, &@dynamic)
				else
					arguments[@name]
				end || @options[:default]
			end
			
			def inspect
				"#{direction}:#{@name} (#{options.inspect})"
			end
		end
		
		def initialize(process_name, type)
			@name = process_name + "." + type
			@full_name = @name.gsub(/[^\w]/, '_')
			
			@process_name = process_name.gsub('-', '_').to_sym
			@type = type
			
			@apply = nil
			
			@parameters = []
		end
		
		# compile.cpp
		attr :name
		
		attr :parameters
		
		# compile
		attr :process_name
		
		# compile_cpp
		attr :full_name
		
		attr :primary_output
		
		def input(name, options = {}, &block)
			self << Parameter.new(:input, name, options, &block)
		end
		
		def parameter(name, options = {}, &block)
			self << Parameter.new(:argument, name, options, &block)
		end
		
		def output(name, options = {}, &block)
			self << Parameter.new(:output, name, options, &block)
		end
		
		def << parameter
			@parameters << parameter
			
			if parameter.output?
				@primary_output ||= parameter
			end
		end
		
		# Check if this rule can process these parameters
		def applicable?(arguments)
			@parameters.each do |parameter|
				next if parameter.implicit?
				
				return false unless parameter.applicable?(arguments)
			end
			
			return true
		end
		
		# The scope is the context in which the dynamic rule computation is done, usually an instance of Task.
		def normalize(arguments, scope)
			Hash[
				@parameters.collect do |parameter|
					[parameter.name, parameter.compute(arguments, scope)]
				end
			]
		end
		
		def files(arguments)
			input_files = []
			output_files = []
			
			@parameters.each do |parameter|
				# This could probably be improved a bit, we are assuming all parameters are file based:
				value = arguments[parameter.name]
				
				next unless value
				
				case parameter.direction
				when :input
					input_files << value
				when :output
					output_files << value
				end
			end
			
			return Build::Files::Composite.new(input_files), Build::Files::Composite.new(output_files)
		end
		
		def apply(&block)
			@apply = Proc.new(&block)
		end
		
		def apply!(scope, arguments)
			scope.instance_exec(arguments, &@apply) if @apply
		end
		
		def result(arguments)
			if @primary_output
				arguments[@primary_output.name]
			end
		end
		
		def ==(other)
			other.kind_of?(self.class) and @name == other.name and @parameters == other.parameters
		end
		
		def to_s
			"#<#{self.class} #{@name.dump}>"
		end
	end
	
	class NoApplicableRule < StandardError
		def initialize(name, arguments)
			super "No applicable rule with name #{name}.* for parameters: #{arguments.inspect}"
			
			@name = name
			@arguments = arguments
		end
	end
end