class SeparateErasureCompiler
	super SeparateCompiler

	private var class_ids: Map[MClass, Int] is noinit
	private var class_colors: Map[MClass, Int] is noinit
	protected var vt_colors: Map[MVirtualTypeProp, Int] is noinit

	init do

		# Class coloring
		var poset = mainmodule.flatten_mclass_hierarchy
		var mclasses = new HashSet[MClass].from(poset)
		var colorer = new POSetColorer[MClass]
		colorer.colorize(poset)
		class_ids = colorer.ids
		class_colors = colorer.colors
		class_tables = self.build_class_typing_tables(mclasses)

		# lookup vt to build layout with
		var vts = new HashMap[MClass, Set[MVirtualTypeProp]]
		for mclass in mclasses do
			vts[mclass] = new HashSet[MVirtualTypeProp]
			for mprop in self.mainmodule.properties(mclass) do
				if mprop isa MVirtualTypeProp then
					vts[mclass].add(mprop)
				end
			end
		end

		# vt coloration
		var vt_colorer = new POSetBucketsColorer[MClass, MVirtualTypeProp](poset, colorer.conflicts)
		vt_colors = vt_colorer.colorize(vts)
		vt_tables = build_vt_tables(mclasses)
	end

	fun build_vt_tables(mclasses: Set[MClass]): Map[MClass, Array[nullable MPropDef]] do
		var tables = new HashMap[MClass, Array[nullable MPropDef]]
		for mclass in mclasses do
			var table = new Array[nullable MPropDef]
			# first, fill table from parents by reverse linearization order
			var parents = new Array[MClass]
			if mainmodule.flatten_mclass_hierarchy.has(mclass) then
				parents = mclass.in_hierarchy(mainmodule).greaters.to_a
				self.mainmodule.linearize_mclasses(parents)
			end
			for parent in parents do
				if parent == mclass then continue
				for mproperty in self.mainmodule.properties(parent) do
					if not mproperty isa MVirtualTypeProp then continue
					var color = vt_colors[mproperty]
					if table.length <= color then
						for i in [table.length .. color[ do
							table[i] = null
						end
					end
					for mpropdef in mproperty.mpropdefs do
						if mpropdef.mclassdef.mclass == parent then
							table[color] = mpropdef
						end
					end
				end
			end

			# then override with local properties
			for mproperty in self.mainmodule.properties(mclass) do
				if not mproperty isa MVirtualTypeProp then continue
				var color = vt_colors[mproperty]
				if table.length <= color then
					for i in [table.length .. color[ do
						table[i] = null
					end
				end
				for mpropdef in mproperty.mpropdefs do
					if mpropdef.mclassdef.mclass == mclass then
						table[color] = mpropdef
					end
				end
			end
			tables[mclass] = table
		end
		return tables
	end

	# Build class tables
	fun build_class_typing_tables(mclasses: Set[MClass]): Map[MClass, Array[nullable MClass]] do
		var tables = new HashMap[MClass, Array[nullable MClass]]
		for mclass in mclasses do
			var table = new Array[nullable MClass]
			var supers = new Array[MClass]
			if mainmodule.flatten_mclass_hierarchy.has(mclass) then
				supers = mclass.in_hierarchy(mainmodule).greaters.to_a
			end
			for sup in supers do
				var color = class_colors[sup]
				if table.length <= color then
					for i in [table.length .. color[ do
						table[i] = null
					end
				end
				table[color] = sup
			end
			tables[mclass] = table
		end
		return tables
	end

	redef fun compile_header_structs do
		self.header.add_decl("typedef void(*nitmethod_t)(void); /* general C type representing a Nit method. */")
		self.compile_header_attribute_structs
		self.header.add_decl("struct class \{ int id; const char *name; int box_kind; int color; const struct vts_table *vts_table; const struct type_table *type_table; nitmethod_t vft[]; \}; /* general C type representing a Nit class. */")
		self.header.add_decl("struct type_table \{ int size; int table[]; \}; /* colorized type table. */")
		self.header.add_decl("struct vts_entry \{ short int is_nullable; const struct class *class; \}; /* link (nullable or not) between the vts and is bound. */")
		self.header.add_decl("struct vts_table \{ int dummy; const struct vts_entry vts[]; \}; /* vts list of a C type representation. */")
		self.header.add_decl("typedef struct instance \{ const struct class *class; nitattribute_t attrs[1]; \} val; /* general C type representing a Nit instance. */")
	end

	redef fun compile_class_if_universal(ccinfo, v)
	do
		var mclass = ccinfo.mclass
		var mtype = ccinfo.mtype
		var c_name = mclass.c_name
		var is_dead = ccinfo.is_dead

		if mtype.is_c_primitive or mtype.mclass.name == "Pointer" then
			#Build instance struct
			self.header.add_decl("struct instance_{c_name} \{")
			self.header.add_decl("const struct class *class;")
			self.header.add_decl("{mtype.ctype} value;")
			self.header.add_decl("\};")

			#Build BOX
			self.provide_declaration("BOX_{c_name}", "val* BOX_{c_name}({mtype.ctype_extern});")
			v.add_decl("/* allocate {mtype} */")
			v.add_decl("val* BOX_{mtype.c_name}({mtype.ctype_extern} value) \{")
			v.add("struct instance_{c_name}*res = nit_alloc(sizeof(struct instance_{c_name}));")
			v.require_declaration("class_{c_name}")
			v.add("res->class = &class_{c_name};")
			v.add("res->value = value;")
			v.add("return (val*)res;")
			v.add("\}")

			if mtype.mclass.name != "Pointer" then return true

			v = new_visitor
			self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}();")
			v.add_decl("/* allocate {mtype} */")
			v.add_decl("{mtype.ctype} NEW_{c_name}() \{")
			if is_dead then
				v.add_abort("{mclass} is DEAD")
			else
				var res = v.new_named_var(mtype, "self")
				res.is_exact = true
				v.add("{res} = nit_alloc(sizeof(struct instance_{mtype.c_name}));")
				v.require_declaration("class_{c_name}")
				v.add("{res}->class = &class_{c_name};")
				v.add("((struct instance_{mtype.c_name}*){res})->value = NULL;")
				v.add("return {res};")
			end
			v.add("\}")
			return true
		else if mclass.name == "NativeArray" then
			#Build instance struct
			self.header.add_decl("struct instance_{c_name} \{")
			self.header.add_decl("const struct class *class;")
			self.header.add_decl("int length;")
			self.header.add_decl("val* values[];")
			self.header.add_decl("\};")

			#Build NEW
			self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(int length);")
			v.add_decl("/* allocate {mtype} */")
			v.add_decl("{mtype.ctype} NEW_{c_name}(int length) \{")
			var res = v.get_name("self")
			v.add_decl("struct instance_{c_name} *{res};")
			var mtype_elt = mtype.arguments.first
			v.add("{res} = nit_alloc(sizeof(struct instance_{c_name}) + length*sizeof({mtype_elt.ctype}));")
			v.require_declaration("class_{c_name}")
			v.add("{res}->class = &class_{c_name};")
			v.add("{res}->length = length;")
			v.add("return (val*){res};")
			v.add("\}")
			return true
                else if mclass.name == "RoutineRef" then
                        self.header.add_decl("struct instance_{c_name} \{")
                        self.header.add_decl("const struct class *class;")
                        self.header.add_decl("val* recv;")
                        self.header.add_decl("nitmethod_t method;")
                        self.header.add_decl("\};")

                        self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(val* recv, nitmethod_t method, const struct class* class);")
                        v.add_decl("/* allocate {mtype} */")
                        v.add_decl("{mtype.ctype} NEW_{c_name}(val* recv, nitmethod_t method, const struct class* class)\{")
                        var res = v.get_name("self")
                        v.add_decl("struct instance_{c_name} *{res};")
                        var alloc = v.nit_alloc("sizeof(struct instance_{c_name})", mclass.full_name)
                        v.add("{res} = {alloc};")
                        v.add("{res}->class = class;")
                        v.add("{res}->recv = recv;")
                        v.add("{res}->method = method;")
                        v.add("return (val*){res};")
                        v.add("\}")
                        return true
		else if mtype.mclass.kind == extern_kind and mtype.mclass.name != "CString" then
			var pointer_type = mainmodule.pointer_type

			self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}();")
			v.add_decl("/* allocate {mtype} */")
			v.add_decl("{mtype.ctype} NEW_{c_name}() \{")
			if is_dead then
				v.add_abort("{mclass} is DEAD")
			else
				var res = v.new_named_var(mtype, "self")
				res.is_exact = true
				v.add("{res} = nit_alloc(sizeof(struct instance_{pointer_type.c_name}));")
				#v.add("{res}->type = type;")
				v.require_declaration("class_{c_name}")
				v.add("{res}->class = &class_{c_name};")
				v.add("((struct instance_{pointer_type.c_name}*){res})->value = NULL;")
				v.add("return {res};")
			end
			v.add("\}")
			return true
		end
		return false
	end

	redef fun compile_class_vft(ccinfo, v)
	do
		var mclass = ccinfo.mclass
		var mtype = ccinfo.mtype
		var c_name = mclass.c_name
		var is_dead = ccinfo.is_dead
		var rta = runtime_type_analysis

		# Build class vft
		self.provide_declaration("class_{c_name}", "extern const struct class class_{c_name};")

		v.add_decl("const struct class class_{c_name} = \{")
		v.add_decl("{class_ids[mclass]},")
		v.add_decl("\"{mclass.name}\", /* class_name_string */")
		v.add_decl("{self.box_kind_of(mclass)}, /* box_kind */")
		v.add_decl("{class_colors[mclass]},")
		if not is_dead then
			if build_class_vts_table(mclass) then
				v.require_declaration("vts_table_{c_name}")
				v.add_decl("&vts_table_{c_name},")
			else
				v.add_decl("NULL,")
			end
			v.add_decl("&type_table_{c_name},")
			v.add_decl("\{")
			var vft = self.method_tables.get_or_null(mclass)
			if vft != null then for i in [0 .. vft.length[ do
				var mpropdef = vft[i]
				if mpropdef == null then
					v.add_decl("NULL, /* empty */")
				else
					assert mpropdef isa MMethodDef
					if rta != null and not rta.live_methoddefs.has(mpropdef) then
						v.add_decl("NULL, /* DEAD {mclass.intro_mmodule}:{mclass}:{mpropdef} */")
						continue
					end
					var rf = mpropdef.virtual_runtime_function
					v.require_declaration(rf.c_name)
					v.add_decl("(nitmethod_t){rf.c_name}, /* pointer to {mpropdef.full_name} */")
				end
			end
			v.add_decl("\}")
		end
		v.add_decl("\};")
	end

	protected fun compile_class_type_table(ccinfo: ClassCompilationInfo, v: SeparateCompilerVisitor)
	do
		var mclass = ccinfo.mclass
		var c_name = mclass.c_name
		var class_table = self.class_tables[mclass]

		# Build class type table
		v.add_decl("const struct type_table type_table_{c_name} = \{")
		v.add_decl("{class_table.length},")
		v.add_decl("\{")
		for msuper in class_table do
			if msuper == null then
				v.add_decl("-1, /* empty */")
			else
				v.add_decl("{self.class_ids[msuper]}, /* {msuper} */")
			end
		end
		v.add_decl("\}")
		v.add_decl("\};")
	end

	redef fun compile_default_new(ccinfo, v)
	do
		var mclass = ccinfo.mclass
		var mtype = ccinfo.mtype
		var c_name = mclass.c_name
		var is_dead = ccinfo.is_dead

		#Build NEW
		self.provide_declaration("NEW_{c_name}", "{mtype.ctype} NEW_{c_name}(void);")
		v.add_decl("/* allocate {mtype} */")
		v.add_decl("{mtype.ctype} NEW_{c_name}(void) \{")
		if is_dead then
			v.add_abort("{mclass} is DEAD")
		else

			var res = v.new_named_var(mtype, "self")
			res.is_exact = true
			var attrs = self.attr_tables.get_or_null(mclass)
			if attrs == null then
				v.add("{res} = nit_alloc(sizeof(struct instance));")
			else
				v.add("{res} = nit_alloc(sizeof(struct instance) + {attrs.length}*sizeof(nitattribute_t));")
			end
			v.require_declaration("class_{c_name}")
			v.add("{res}->class = &class_{c_name};")
			if attrs != null then
				self.generate_init_attr(v, res, mtype)
				v.set_finalizer res
			end
			v.add("return {res};")
		end
		v.add("\}")
	end

	redef fun build_class_compilation_info(mclass)
	do
		var ccinfo = super
		var mtype = ccinfo.mtype
		var rta = runtime_type_analysis
		var is_dead = false # mclass.kind == abstract_kind or mclass.kind == interface_kind
		if not is_dead and rta != null and not rta.live_classes.has(mclass) and not mtype.is_c_primitive and mclass.name != "NativeArray" then
			is_dead = true
		end
		ccinfo.is_dead = is_dead
		return ccinfo
	end

	redef fun compile_class_to_c(mclass: MClass)
	do
		var ccinfo = build_class_compilation_info(mclass)
		var v = new_visitor
		v.add_decl("/* runtime class {mclass.c_name} */")
		self.provide_declaration("class_{mclass.c_name}", "extern const struct class class_{mclass.c_name};")
		v.add_decl("extern const struct type_table type_table_{mclass.c_name};")
		self.compile_class_vft(ccinfo, v)
		self.compile_class_type_table(ccinfo, v)
		if not self.compile_class_if_universal(ccinfo, v) then
			self.compile_default_new(ccinfo, v)
		end
	end

	private fun build_class_vts_table(mclass: MClass): Bool do
		if self.vt_tables[mclass].is_empty then return false

		self.provide_declaration("vts_table_{mclass.c_name}", "extern const struct vts_table vts_table_{mclass.c_name};")

		var v = new_visitor
		v.add_decl("const struct vts_table vts_table_{mclass.c_name} = \{")
		v.add_decl("0, /* dummy */")
		v.add_decl("\{")

		for vt in self.vt_tables[mclass] do
			if vt == null then
				v.add_decl("\{-1, NULL\}, /* empty */")
			else
				var is_null = 0
				var bound = retrieve_vt_bound(mclass.intro.bound_mtype, vt.as(MVirtualTypeDef).bound)
				while bound isa MNullableType do
					bound = retrieve_vt_bound(mclass.intro.bound_mtype, bound.mtype)
					is_null = 1
				end
				var vtclass = bound.as(MClassType).mclass
				v.require_declaration("class_{vtclass.c_name}")
				v.add_decl("\{{is_null}, &class_{vtclass.c_name}\}, /* {vt} */")
			end
		end
		v.add_decl("\},")
		v.add_decl("\};")
		return true
	end

	private fun retrieve_vt_bound(anchor: MClassType, mtype: nullable MType): MType do
		if mtype == null then
			print "NOT YET IMPLEMENTED: retrieve_vt_bound on null"
			abort
		end
		if mtype isa MVirtualType then
			return mtype.anchor_to(mainmodule, anchor)
		else if mtype isa MParameterType then
			return mtype.anchor_to(mainmodule, anchor)
		else
			return mtype
		end
	end

	redef fun compile_types
	do
		compile_color_consts(vt_colors)
	end

	redef fun new_visitor do return new SeparateErasureCompilerVisitor(self)

	# Stats

	private var class_tables: Map[MClass, Array[nullable MClass]] is noinit
	private var vt_tables: Map[MClass, Array[nullable MPropDef]] is noinit

	redef fun display_sizes
	do
		print "# size of subtyping tables"
		print "\ttotal \tholes"
		var total = 0
		var holes = 0
		for t, table in class_tables do
			total += table.length
			for e in table do if e == null then holes += 1
		end
		print "\t{total}\t{holes}"

		print "# size of resolution tables"
		print "\ttotal \tholes"
		total = 0
		holes = 0
		for t, table in vt_tables do
			total += table.length
			for e in table do if e == null then holes += 1
		end
		print "\t{total}\t{holes}"

		print "# size of methods tables"
		print "\ttotal \tholes"
		total = 0
		holes = 0
		for t, table in method_tables do
			total += table.length
			for e in table do if e == null then holes += 1
		end
		print "\t{total}\t{holes}"

		print "# size of attributes tables"
		print "\ttotal \tholes"
		total = 0
		holes = 0
		for t, table in attr_tables do
			total += table.length
			for e in table do if e == null then holes += 1
		end
		print "\t{total}\t{holes}"
	end
end