python-plus-plus/ppp_interpreter.py

from dataclasses import dataclass
from typing import Dict, List as List_, Optional, Tuple

from ppp_ast import *
from ppp_lexer import Lexer
from ppp_object import Bool, EnumValue, Function, Int, Object, Str, Struct, Tuple as TupleObject, List as ListObject, TypeObject, Void
from ppp_parser import is_valid_target, parse_statement
from ppp_tokens import EofToken
from ppp_stdlib import variables
from ppp_types import EnumType, FunctionType, GenericType, Int as IntType, ListType, Str as StrType, StructType, TupleType, Type, TypeType, VariableType, Void as VoidType

@dataclass
class Declared:
	type: Type
	value: Object

	@staticmethod
	def from_obj(obj: Object) -> 'Declared':
		return Declared(obj.get_type(), obj)

@dataclass
class Undeclared:
	type: Type

@dataclass
class Constant:
	type: Type
	value: Object

	@staticmethod
	def from_obj(obj: Object) -> 'Declared':
		return Declared(obj.get_type(), obj)

VariableState = Declared | Undeclared | Constant

Module = Dict[str, VariableState]

@dataclass
class ProgramState:
	modules: Dict[str, Module] # TODO: What is the type of module?
	contexts: List_[Dict[str, VariableState]]

	def push_context(self, variables: Dict[str, VariableState]): self.contexts.append(variables)
	def pop_context(self): self.contexts.pop()

	def declare_variable(self, name: str, type: Type):
		assert not (name in self.contexts[-1]), f"'{name}' has already been declared!"
		self.contexts[-1][name] = Undeclared(type)

	def assign_variable(self, name: str, value: Object):
		for context in self.contexts[::-1]:
			if name in context:
				assert value.get_type().is_subtype_of(context[name].type), f"In the assignment of '{name}', expected value of type {context[name].type.represent()}, but got a value of type {value.get_type().represent()}!"
				context[name] = Declared(context[name].type, value)
				return
		assert False, f"'{name}' doesn't exist!"

	def declare_and_assign_variable(self, name: str, value: Object):
		self.declare_variable(name, value.get_type())
		self.assign_variable(name, value)

	def exists(self, name: str) -> bool:
		for context in self.contexts[::-1]:
			if name in context: return True
		return False

	def access_variable(self, name: str) -> Object:
		for context in self.contexts[::-1]:
			if name in context:
				value = context[name]
				assert not isinstance(value, Undeclared), f"{name} is not declared!"
				return value.value
		assert False, f"'{name}' is not defined!"

def is_truthy(object: Object) -> bool:
	match object:
		case Bool(value): return value
		case _: assert False, ("Unimplemented", object)

def calculate_expression(expression: Expression, program: ProgramState) -> Object:
	match expression:
		case FunctionCall(function_, arguments_):
			function = calculate_expression(function_, program)
			assert isinstance(function, Function), (function_, function)
			name, parameters, return_type, body, func = function.function

			arguments = [calculate_expression(argument, program) for argument in arguments_]
			assert len(arguments) == len(parameters), f"{name} expected {len(parameters)} arguments, but got {len(arguments)}!"

			for (argument, (parameter_name, parameter)) in zip(arguments, parameters):
				assert argument.get_type().is_subtype_of(parameter), f"For argument '{parameter_name}' of '{name}', expected value of type {parameter.represent()}, but got {argument.get_type().represent()}!"
			return_value = func(name, parameters, return_type, body, *arguments)
			assert isinstance(return_value, Object), return_value
			assert return_value.get_type().is_subtype_of(return_type)
			return return_value
		case Variable(name):
			return program.access_variable(name)
		case String(string):
			return Str(string)
		case Number(number):
			return Int(number)
		case TupleExpr(elements_):
			tuple_elements = [calculate_expression(element, program) for element in elements_]
			return TupleObject(TupleType([element.get_type() for element in tuple_elements]), tuple(tuple_elements))
		case Ternary(condition_, if_true, if_false):
			return calculate_expression(if_true, program) if is_truthy(calculate_expression(condition_, program)) else calculate_expression(if_false, program)
		case Or(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			assert isinstance(left_value, Bool)
			if left_value.value: return Bool(True)
			right_value = calculate_expression(rhs, program)
			assert isinstance(right_value, Bool)
			return Bool(left_value.value or right_value.value)
		case And(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			assert isinstance(left_value, Bool)
			if not left_value.value: return Bool(False)
			right_value = calculate_expression(rhs, program)
			assert isinstance(right_value, Bool)
			return Bool(left_value.value and right_value.value)
		case Bor(lhs, rhs):
			assert False, ("Unimplemented", lhs, rhs)
		case Bxor(lhs, rhs):
			assert False, ("Unimplemented", lhs, rhs)
		case Band(lhs, rhs):
			assert False, ("Unimplemented", lhs, rhs)
		case Equal(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			if left_value.get_type() != right_value.get_type(): return Bool(False)
			return Bool(left_value == right_value)
		case NotEqual(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			if left_value.get_type() != right_value.get_type(): return Bool(True)
			return Bool(left_value != right_value)
		case LessThan(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			assert isinstance(left_value, Int)
			assert isinstance(right_value, Int)
			return Bool(left_value.num < right_value.num)
		case GreaterThan(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			assert isinstance(left_value, Int)
			assert isinstance(right_value, Int)
			return Bool(left_value.num > right_value.num)
		case LessThanOrEqual(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			assert isinstance(left_value, Int)
			assert isinstance(right_value, Int)
			return Bool(left_value.num <= right_value.num)
		case GreaterThanOrEqual(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			assert isinstance(left_value, Int)
			assert isinstance(right_value, Int)
			return Bool(left_value.num >= right_value.num)
		case ShiftLeft(lhs, rhs):
			assert False, ("Unimplemented", lhs, rhs)
		case ShiftRight(lhs, rhs):
			assert False, ("Unimplemented", lhs, rhs)
		case Addition(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			if isinstance(left_value, Int):
				assert isinstance(right_value, Int)
				return Int(left_value.num + right_value.num)
			elif isinstance(left_value, Str):
				assert isinstance(right_value, Str)
				return Str(left_value.str + right_value.str)
			elif isinstance(left_value, ListObject):
				assert isinstance(right_value, ListObject)
				if left_value.type.type == VariableType(""): return right_value
				if right_value.type.type == VariableType(""): return left_value
				assert left_value.type == right_value.type, (left_value, right_value)
				return ListObject(left_value.type, left_value.list + right_value.list)
			else:
				assert False, f"Expected two ints or two strs. Got {left_value.get_type().represent()} and {right_value.get_type().represent()}!"
		case Subtract(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			assert isinstance(left_value, Int)
			assert isinstance(right_value, Int)
			return Int(left_value.num - right_value.num)
		case Multiplication(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			assert isinstance(left_value, Int)
			assert isinstance(right_value, Int)
			return Int(left_value.num * right_value.num)
		case Division(lhs, rhs):
			assert False, ("Unimplemented", lhs, rhs)
		case Modulo(lhs, rhs):
			left_value = calculate_expression(lhs, program)
			right_value = calculate_expression(rhs, program)
			if isinstance(left_value, Int):
				assert isinstance(right_value, Int), f"Expected int, got {right_value.get_type().represent()}!"
				return Int(left_value.num % right_value.num)
			elif isinstance(left_value, Str):
				# TODO: Maybe actually just implement C-style string formatting? This code is a mess
				match right_value:
					case TupleObject(_, tuple_obj_elements):
						assert left_value.str.count("%"+"s") == len(tuple_obj_elements), (left_value.str.count("%%s"), len(tuple_obj_elements))
						the_elements: Tuple[str, ...] = ()
						for element in tuple_obj_elements:
							assert isinstance(element, Str)
							the_elements += (element.str,)

						return Str(left_value.str % the_elements)
					case Str(string):
						return Str(left_value.str % string)
					case _:
						assert False, f"Format string expected either a string or a tuple of strings, but got a '{right_value.get_type().represent()}'!\n{lhs, rhs, right_value}"
				match right_value:
					case Int(num): return Str(left_value.str % num)
					case _: assert False, ("Unimplemented", right_value)
			assert False, ("Unimplemented", lhs, rhs)
		case StructInstantiation(struct_, arguments_):
			struct = calculate_expression(struct_, program)
			assert isinstance(struct, TypeObject)
			assert isinstance(struct.type, StructType)

			struct_arguments = {name: calculate_expression(expression, program) for (name, expression) in arguments_}

			for field in struct_arguments:
				assert field in struct.type.members, f"The struct {struct.type.name} does not have the field '{field}'!"
				assert struct_arguments[field].get_type().is_subtype_of(struct.type.members[field]), f"'{struct.type.name}.{field}' field expected value of type {struct.type.members[field].represent()}, but got a value of type {struct_arguments[field].get_type().represent()}!"

			for field in struct.type.members:
				assert field in struct_arguments, f"Missing field '{field}' of type {struct.type.represent()}."

			return Struct(struct.type, struct_arguments)
		case FieldAccess(expression_, field):
			value = calculate_expression(expression_, program)
			match value:
				case TypeObject(type):
					match type:
						case EnumType(name, members, _):
							assert field in members, f"{type.represent()} does not contain the member '{field}'!"
							member = members[field]
							if not member: return EnumValue(type, field, [])
							def return_member(name: str, parameters: List_[Tuple[str, Type]], return_type: Type, _statement: Statement, *args: Object):
								assert isinstance(return_type, EnumType)
								assert len(args) == len(parameters)
								for (arg, (_, parameter)) in zip(args, parameters):
									assert arg.get_type().is_subtype_of(parameter)
								return EnumValue(return_type, name, list(args))
							return Function(FunctionType(member, type), (field, [('', member_type) for member_type in member], type, Statements([]), return_member))

						case _: assert False, ("Unimplemented", type, field)
				case Struct(type, fields):
					assert field in fields, f"Struct '{type.represent()}' does not have the field '{field}'!"
					return fields[field]
				case _: assert False, ("Unimplemented", value, field)
		case ArrayAccess(array_, index_):
			array = calculate_expression(array_, program)
			assert array.get_type().is_indexable(), f"Objects of type {array.get_type().represent()} cannot be indexed!"
			if isinstance(array, Str):
				index = calculate_expression(index_, program)
				assert isinstance(index, Int), f"Index must be '{IntType.represent()}', got '{index.get_type().represent()}'!"
				assert 0 <= index.num < len(array.str), f"Index out of bounds. Str of length {len(array.str)} accessed at index {index.num}. {array_, index_}"
				return Str(array.str[index.num])
			elif isinstance(array, TupleObject):
				index = calculate_expression(index_, program)
				assert isinstance(index, Int), f"Index must be '{IntType.represent()}', got '{index.get_type().represent()}'!"
				assert 0 <= index.num <= len(array.tuple), f"Index out of bounds. Tuple of length {len(array.tuple)} accessed at index {index.num}. {array_, index_}"
				return array.tuple[index.num]
			elif isinstance(array, ListObject):
				array_type = array.type.type
				index = calculate_expression(index_, program)
				assert isinstance(index, Int), f"Index must be '{IntType.represent()}', got '{index.get_type().represent()}'!"
				assert 0 <= index.num < len(array.list), f"Index out of bounds. List of length {len(array.list)} accessed at index {index.num}"
				element = array.list[index.num]
				assert element.get_type().is_subtype_of(array_type)
				return element
			else:
				assert False, "Unreachable"
		case Bnot(expression_):
			assert False, ("Unimplemented", expression_)
		case Not(expression_):
			value = calculate_expression(expression_, program)
			assert isinstance(value, Bool)
			return Bool(not value.value)
		case UnaryPlus(expression_):
			assert False, ("Unimplemented", expression_)
		case UnaryMinus (expression_):
			assert False, ("Unimplemented", expression_)
		case Array(element_type_, array_):
			element_type = calculate_type_expression(element_type_, program)
			array_elements_: List_[Object] = []
			for element_ in array_:
				element = calculate_expression(element_, program)
				assert element.get_type().is_subtype_of(element_type), (element, element_type)
				array_elements_.append(element)
			return ListObject(ListType(element_type), array_elements_)
		case LoopComprehension(element_type_, body_, variable, array_):
			element_type = calculate_type_expression(element_type_, program)
			array = calculate_expression(array_, program)
			assert array.get_type().is_indexable()
			if isinstance(array, ListObject):
				elements: List_[Object] = []
				for element in array.list:
					program.push_context({variable: Declared.from_obj(element)})
					elements.append(calculate_expression(body_, program))
					program.pop_context()
					assert elements[-1].get_type().is_subtype_of(element_type)
				return ListObject(ListType(element_type), elements)
			else:
				assert False, ("Unimplemented", array)
		case _:
			assert False, ("Unimplemented", expression)
	assert False

def calculate_type_expression(expression: TypeExpression, program: ProgramState, must_resolve:bool=True) -> Type:
	match expression:
		case TypeName(name):
			if not program.exists(name) and not must_resolve: return VariableType(name)
			type_obj = program.access_variable(name)
			assert isinstance(type_obj, TypeObject)
			return type_obj.type
		case ListTypeExpr(type_):
			return ListType(calculate_type_expression(type_, program, must_resolve))
		case TupleTypeExpr(types_):
			return TupleType([calculate_type_expression(type, program, must_resolve) for type in types_])
		case FunctionTypeExpr(arguments_, return_type_):
			return FunctionType([calculate_type_expression(argument, program, must_resolve) for argument in arguments_], calculate_type_expression(return_type_, program, must_resolve))
		case TypeSpecification(type_, types_):
			type = calculate_type_expression(type_, program, must_resolve)
			assert isinstance(type, GenericType)
			assert len(type.variables) == len(types_)
			types = [calculate_type_expression(type_, program, must_resolve) for type_ in types_]
			result_type = type.substitute(types)
			return result_type
		case _:
			assert False, ("Unimplemented", expression)
	assert False, "Unreachable"

def match_enum_expression(enum: Type, value: Object, expression: Expression) -> Optional[Dict[str, Object]]:
	assert isinstance(enum, EnumType)
	assert isinstance(value, EnumValue)
	match expression:
		case Variable(name):
			if name.startswith('_'): return {name: value}
			assert name in enum.members, f"Enum '{enum.represent()}' does not contain the member '{name}'!"
			assert enum.members[name] == [], f"Enum member '{enum.represent()}.{name}' has {len(enum.members[name])} fields that have not been captured!"
			if name != value.name or value.values: return None
			return {}
		case FunctionCall(function, arguments):
			assert isinstance(function, Variable)
			assert function.name in enum.members, f"Enum '{enum.represent()}' does not contain the member '{function.name}'!"
			if function.name != value.name: return None
			member = enum.members[function.name]
			assert isinstance(member, list) # TODO: Report calling a struct enum member with parentheses
			assert isinstance(value.values, list) # Same as above but like inverse
			assert len(arguments) == len(member), f"{value.get_type().represent()}.{value.name} expected {len(member)} args, but got {len(arguments)}!"
			assert len(member) == len(value.values)
			new_variables: Dict[str, Object] = {}
			for argument, element in zip(arguments, value.values):
				assert isinstance(argument, Variable) # TODO
				new_variables[argument.name] = element
			return new_variables
		case _:
			assert False, ("Unimplemented", expression)
	assert False, ("Unimplemented", value, expression)

def update_types(type: Type, program: ProgramState):
	assert isinstance(type, EnumType) or isinstance(type, StructType)
	for context in program.contexts:
		for variable_ in context:
			variable = context[variable_]
			match variable:
				case Declared(type_, value):
					if isinstance(variable.value, TypeObject):
						assert type_ == TypeType
						assert isinstance(value, TypeObject)
						value.type.fill({type.name: type}, [])
				case Undeclared(type_): pass
				case _: assert False, ("Unimplemented", variable)

@dataclass
class ReturnResult:
	value: Object

@dataclass
class ContinueResult:
	pass

@dataclass
class BreakResult:
	pass

@dataclass
class NothingResult:
	pass

StatementsResult = ReturnResult | ContinueResult | BreakResult | NothingResult

def interpret_statements(statements: List_[Statement], program: ProgramState) -> StatementsResult:
	for statement in statements:
		match statement:
			case ExpressionStatement(expression):
				calculate_expression(expression, program)
			case Assignment(lhs, rhs, type_):
				assert is_valid_target(lhs)
				match lhs:
					case Variable(name):
						value = calculate_expression(rhs, program)
						if type_:
							type = calculate_type_expression(type_, program)
							program.declare_variable(name, type)
						program.assign_variable(name, value)
					case FieldAccess(expression_, field):
						expr = calculate_expression(expression_, program)
						assert isinstance(expr, Struct)
						struct_type = expr.get_type()
						assert isinstance(struct_type, StructType)
						assert field in struct_type.members, f"Struct '{struct_type.represent()}' does not contain the field '{field}'!"
						value = calculate_expression(rhs, program)
						assert value.get_type().is_subtype_of(struct_type.members[field])
						expr.fields[field] = value
					case ArrayAccess(array_, index_):
						array = calculate_expression(array_, program)
						index = calculate_expression(index_, program)
						value = calculate_expression(rhs, program)
						assert array.get_type().is_indexable(), array
						match array:
							case _: assert False, ("Unimplemented", array)
					case _:
						assert False, ("Unimplemented", lhs)
			case IfStatement(condition, body, else_body):
				if is_truthy(calculate_expression(condition, program)):
					program.push_context({})
					return_value = interpret_statements([body], program)
					program.pop_context()
					if not isinstance(return_value, NothingResult): return return_value
				elif else_body:
					program.push_context({})
					return_value = interpret_statements([else_body], program)
					program.pop_context()
					if not isinstance(return_value, NothingResult): return return_value
			case Statements(statements):
				# TODO: Proper context and scoping
				program.push_context({})
				return_value = interpret_statements(statements, program)
				program.pop_context()
				if not isinstance(return_value, NothingResult): return return_value
			case FunctionDefinition(name, arguments_, return_type_, body):
				def run_function(name: str, arguments: List_[Tuple[str, Type]], return_type: Type, body: Statement, *args: Object) -> Object:
					assert len(args) == len(arguments), f"'{name}' expected {len(arguments)} arguments, but got {len(args)} instead!"
					new_program = ProgramState(program.modules, program.contexts[:2])
					new_program.push_context({})
					for (argument, (argument_name, argument_type)) in zip(args, arguments):
						assert argument.get_type().is_subtype_of(argument_type), f"'{name}' expected argument '{argument_name}' to have a value of type {argument_type.represent()}, but got {argument.get_type().represent()} instead!"
						new_program.declare_variable(argument_name, argument_type)
						new_program.assign_variable(argument_name, argument)
					return_value = interpret_statements([body], new_program)
					new_program.pop_context()
					assert len(new_program.contexts) == 2
					match return_value:
						case ReturnResult(value):
							assert value.get_type().is_subtype_of(return_type), f"'{name}' expected a return value of type {return_type.represent()}, but got {value.get_type().represent()}!"
							return value
						case NothingResult():
							assert return_type.is_subtype_of(VoidType), f"'{name}' expected a return type of {return_type.represent()} but got nothing!"
							return Void
						case _: assert False, ("Unimplemented", return_value)

				arguments = [(argument.name, calculate_type_expression(argument.type, program)) for argument in arguments_]
				return_type = calculate_type_expression(return_type_, program) if return_type_ else VoidType
				function_type = FunctionType([argument[1] for argument in arguments], return_type)
				object = Function(function_type, (name, arguments, return_type, body, run_function))

				program.declare_and_assign_variable(name, object)
			case EnumDefinition(name, entries):
				enum_type = EnumType(name, {entry.name: [calculate_type_expression(type, program, False) for type in entry.types] for entry in entries}, [])
				program.declare_and_assign_variable(name, TypeObject(enum_type))
				update_types(enum_type, program)
			case StructDefinition(name, entries):
				struct_type = StructType(name, {entry.name: calculate_type_expression(entry.type, program, False) for entry in entries}, [])
				program.declare_and_assign_variable(name, TypeObject(struct_type))
				update_types(struct_type, program)
			case MatchStatement(value_, cases):
				value = calculate_expression(value_, program)
				assert isinstance(value, EnumValue), f"Cannot only match over enums, got {value.get_type().represent()} instead!"
				assert isinstance(value.type, EnumType) # TODO: Pattern match things besides enums

				for case in cases:
					if (new_variables := match_enum_expression(value.type, value, case[0])) is not None:
						program.push_context({name: Declared.from_obj(new_variables[name]) for name in new_variables})
						return_value = interpret_statements([case[1]], program)
						program.pop_context()
						if not isinstance(return_value, NothingResult): return return_value
						break
			case DoWhileStatement(body, condition_):
				assert condition_ is None # TODO
				program.push_context({})
				return_value = interpret_statements([body], program)
				program.pop_context()
				if not isinstance(return_value, NothingResult): return return_value
			case WhileStatement(condition_, body):
				while is_truthy(calculate_expression(condition_, program)):
					program.push_context({})
					return_value = interpret_statements([body], program)
					program.pop_context()
					match return_value:
						case NothingResult(): pass
						case ContinueResult(): continue
						case BreakResult(): break
						case ReturnResult(_): return return_value
						case _: assert False, ("Unimplemented", return_value)
					if not isinstance(return_value, NothingResult): return return_value
			case AssertStatement(condition_, message_):
				if not is_truthy(calculate_expression(condition_, program)):
					if message_:
						message = calculate_expression(message_, program)
						assert isinstance(message, Str)
						assert False, message.str
					assert False, "Assertion failed"
			case TypeDeclarationStatement(declaration):
				program.declare_variable(declaration.name, calculate_type_expression(declaration.type, program))
			case ForLoop(variable, array_, body):
				array = calculate_expression(array_, program)
				if isinstance(array, ListObject):
					for value in array.list:
						assert isinstance(value, Object)
						assert value.get_type().is_subtype_of(array.type.type)
						program.push_context({variable: Declared.from_obj(value)})
						return_value = interpret_statements([body], program)
						program.pop_context()
						match return_value:
							case NothingResult(): pass
							case ReturnResult(_): return return_value
							case _: assert False, ("Unimplemented", return_value)
			case ContinueStatement(): return ContinueResult()
			case BreakStatement(): return BreakResult()
			case ReturnStatement(expression=expression):
				return ReturnResult(calculate_expression(expression, program))
			case Import(file):
				# TODO: Maybe an inclusion system within a preprocessor maybe
				module = interpret_file(file, program.modules) if file not in program.modules else program.modules[file]
				program.contexts[0] |= module
				if file not in program.modules:
					program.modules[file] = module
			case TypeDefinition(name, expression_):
				program.declare_and_assign_variable(name, TypeObject(calculate_type_expression(expression_, program)))
			case DeferStatement(statement=statement):
				assert False, "TODO: Defers are not implemented"
			case _:
				assert False, ("Unimplemented", statement)
	return NothingResult()

def interpret_file(file_path: str, modules: Dict[str, Module]) -> Module:
	# print(f"\tParsing {file_path}")
	lexer = Lexer.from_file(file_path)
	statements: List_[Statement] = []
	while not lexer.check_token(EofToken()): statements.append(parse_statement(lexer))
	# print(f"\tInterpreting {file_path}")
	program = ProgramState(modules, [{variable: Declared.from_obj(variables[variable]) for variable in variables}, {}])
	return_value = interpret_statements(statements, program)
	# print(f"Finished {file_path}")
	assert len(program.contexts) == 2
	match return_value:
		case NothingResult(): pass
		case ReturnResult(_): assert False, "Cannot return from outside a function!"
		case ContinueResult(): assert False, "Cannot continue from outside a loop!"
		case BreakResult(): assert False, "Cannot break from outside a loop!"
		case _: assert False, ("Unimplemented", return_value)
	return program.contexts[1]