# Module MooseX
# A postmodern object DSL for Ruby
#
# Author::    Tiago Peczenyj  (mailto:tiago.peczenyj@gmail.com)
# Copyright:: Copyright (c) 2014 Tiago Peczenyj
# License::   MIT
#
require "moosex/version"

module MooseX
	
	def MooseX.included(c)
			
		c.extend(MooseX::Core)
			
		c.class_exec do 
			meta = MooseX::Meta.new

			define_singleton_method(:__meta) { meta }
		end

		def initialize(*args)	
			args = BUILDARGS(*args)
			
			self.class.__meta().init(self, args || {})

			BUILD()
		end

		def BUILDARGS(*args)
			args[0]
		end

		def BUILD
		end

		def c.inherited(subclass)
			subclass.class_exec do 
				old_meta = subclass.__meta

				meta = MooseX::Meta.new(old_meta.attrs)

				define_singleton_method(:__meta) { meta }
			end    		
   	end		
					
	end
	
	class Meta
		attr_reader :attrs
		def initialize(attrs=[])
			@attrs = attrs.map{|att| att.clone }
		end
		
		def add(attr)
			@attrs << attr
		end
		
		def init(object, args)
			@attrs.each{ |attr| attr.init(object, args) }
		end
	end	

	module Core
	
		def has(attr_name, attr_options = {})
			if attr_name.is_a? Array 
				attr_name.each do |attr| 
					has(attr, attr_options) 
				end
			elsif attr_name.is_a? Hash 
				attr_name.each_pair do |attr, options |
					has(attr, options)
				end
			else

				attr = MooseX::Attribute.new(attr_name, attr_options)

				attr.methods.each_pair do |method, proc|
					define_method method, &proc
				end

	 			if attr.is.eql?(:rwp) 
					private attr.writter
				elsif attr.is.eql?(:private)
					private attr.writter
					private attr.reader
				end

				__meta.add(attr)
			end
		end
	end	
	
	class Attribute

		attr_reader :attr_symbol, :is, :reader, :writter, :lazy, :builder, :methods
		DEFAULTS= { 
			lazy: false,
			clearer: false,
			required: false, 
			predicate: false,
			isa: lambda { |value| true },
			handles: {},
			trigger: lambda {|object,value|},  # TODO: implement
			coerce: lambda {|object| object},  # TODO: implement
		}

		REQUIRED = [ :is ]

		VALIDATE = {
			is: lambda do |is, field_name| 
				unless [:rw, :rwp, :ro, :lazy, :private].include?(is)
					raise "invalid value for field '#{field_name}' is '#{is}', must be one of :private, :rw, :rwp, :ro or :lazy"  
				end
			end,
		};

		COERCE = {
			is: lambda do |is, field_name| 
				is.to_sym 
			end,
			isa: lambda do |isa, field_name| 
				return isa if isa.is_a? Proc
				
				return lambda do |new_value| 
					unless new_value.is_a?(isa)
						raise "isa check for \"#{field_name}\" failed: is not instance of #{isa}!" 
					end 
				end	 
			end,
			default: lambda do |default, field_name|
				return default if default.is_a? Proc

				return lambda { default }		
			end,
			required: lambda do |required, field_name| 
				!!required 
			end,
			lazy: lambda do |lazy, field_name| 
				!!lazy 
			end,			
			predicate: lambda do |predicate, field_name| 
				if ! predicate
					return false
				elsif predicate.is_a? TrueClass
					return "has_#{field_name}?".to_sym
				end

				begin
					predicate.to_sym
				rescue => e
					# create a nested exception here
					raise "cannot coerce field predicate to a symbol for #{field_name}: #{e}"
				end
			end,
			clearer: lambda do|clearer, field_name| 
				if ! clearer
					return false
				elsif clearer.is_a? TrueClass
					return "clear_#{field_name}!".to_sym
				end
		
				begin
					clearer.to_sym
				rescue => e
					# create a nested exception here
					raise "cannot coerce field clearer to a symbol for #{field_name}: #{e}"
				end
			end,
			handles: lambda do |handles, field_name|
							
				unless handles.is_a? Hash 

					array_of_handles = handles

					unless array_of_handles.is_a? Array
						array_of_handles = [ array_of_handles ]
					end

					handles = array_of_handles.map do |handle|

						if handle == BasicObject
							
							raise "ops, should not use BasicObject for handles in #{field_name}"
						
						elsif handle.is_a? Class

							handle = handle.public_instance_methods - handle.superclass.public_instance_methods
						
						elsif handle.is_a? Module
							
							handle = handle.public_instance_methods

						end
						
						handle

					end.flatten.reduce({}) do |hash, method_name|
						hash.merge({ method_name => method_name })
					end
				end

				handles.map do |key,value|
					{ key.to_sym => value.to_sym }
				end.reduce({}) do |hash,e| 
					hash.merge(e)
				end
			end,
			reader: lambda do |reader, field_name|
				reader.to_sym
			end,
			writter: lambda do |writter, field_name|
				writter.to_sym
			end,
			builder: lambda do |builder, field_name|
				unless builder.is_a? Proc
					builder_method_name = builder.to_sym
					builder = lambda do |object|
						object.send(builder_method_name)
					end
				end

				builder
			end,
			init_arg: lambda do |init_arg, field_name|
				init_arg.to_sym
			end,
			trigger: lambda do |trigger, field_name|
				unless trigger.is_a? Proc
					trigger_method_name = trigger.to_sym
					trigger = lambda do |object, value|
						object.send(trigger_method_name,value)
					end
				end

				trigger				
			end,
			coerce: lambda do |coerce, field_name|
				unless coerce.is_a? Proc
					coerce_method_name = coerce.to_sym
					coerce = lambda do |object|
						object.send(coerce_method_name)
					end
				end

				coerce				
			end,
		};

		def initialize(a, o)
			#o ||= {}
			# todo extract this to a framework, see issue #21 on facebook
			o = DEFAULTS.merge({
				reader: a,
				writter: a.to_s.concat("=").to_sym,
			  builder: "build_#{a}".to_sym,
			  init_arg: a,
			}).merge(o)

			REQUIRED.each { |field| 
				unless o.has_key?(field)
					raise "field #{field} is required for Attribute #{a}" 
				end
			}
			COERCE.each_pair do |field, coerce|
				if o.has_key? field
					o[field] = coerce.call(o[field], a)
				end
			end
			VALIDATE.each_pair do |field, validate|
				return if ! o.has_key? field

				validate.call(o[field], a)
			end

			if o[:is].eql? :ro	
				o[:writter] = nil
			elsif o[:is].eql? :lazy
				o[:lazy] = true
				o[:writter] = nil
			end

			unless o[:lazy]
				o[:builder] = nil
			end

			@attr_symbol = a
			@is          = o[:is]
			@isa         = o[:isa]
			@default     = o[:default]
			@required    = o[:required] 
			@predicate   = o[:predicate]
			@clearer     = o[:clearer]
			@handles     = o[:handles]
			@lazy        = o[:lazy]
			@reader      = o[:reader]
			@writter     = o[:writter]
			@builder     = o[:builder]
			@init_arg    = o[:init_arg]
			@trigger     = o[:trigger]
			@coerce      = o[:coerce]
			@methods     = {}

			if @reader 
				@methods[@reader] = generate_reader
			end
			
			if @writter 
				@methods[@writter] = generate_writter
			end
			inst_variable_name = "@#{@attr_symbol}".to_sym
			if @predicate
				@methods[@predicate] = Proc.new do
					instance_variable_defined? inst_variable_name
				end
			end

			if @clearer
				@methods[@clearer] = Proc.new do
					if instance_variable_defined? inst_variable_name
						remove_instance_variable inst_variable_name
					end
				end
			end
			
			attr_symbol = @attr_symbol
			@handles.each_pair do | method, target_method |
				@methods[method] = Proc.new do |*args|
					self.send(attr_symbol).send(target_method, *args)
				end
			end			
		end
		
		def init(object, args)
			value  = nil
			value_from_default = false
			
			if args.has_key? @init_arg
				value = args[ @init_arg ]
			elsif @default
				value = @default.call
				value_from_default = true
			elsif @required
				raise "attr \"#{@attr_symbol}\" is required"
			else
				return
			end
 

			value = @coerce.call(value)

			@isa.call( value )
			unless value_from_default
				@trigger.call(object, value)
			end
			
			inst_variable_name = "@#{@attr_symbol}".to_sym
			object.instance_variable_set inst_variable_name, value
		end

		private
		def generate_reader
			inst_variable_name = "@#{@attr_symbol}".to_sym
			
			builder    = @builder
			before_get = lambda {|object|  }

			if @lazy
				type_check = @isa
				coerce     = @coerce
				trigger    = @trigger
				before_get = lambda do |object|
					return if object.instance_variable_defined? inst_variable_name

					value = builder.call(object)
					value = coerce.call(value)
					type_check.call(value)
					trigger.call(object, value)
					object.instance_variable_set(inst_variable_name, value)					
				end
			end

			Proc.new do 
				before_get.call(self)
				instance_variable_get inst_variable_name 
			end
		end
		
		def generate_writter
			inst_variable_name = "@#{@attr_symbol}".to_sym
			coerce     = @coerce
			type_check = @isa
			trigger    = @trigger
			Proc.new  do |value| 
				value = coerce.call(value)
				type_check.call(value)
				trigger.call(self,value)
				instance_variable_set inst_variable_name, value
			end
		end	
	end
end