from typing import Callable, Dict, List, Optional, Tuple
from ppp_lexer import Lexer
from ppp_tokens import IdentifierToken, Keyword, KeywordToken, NumberToken, StringToken, Symbol, SymbolToken
from ppp_ast import *

def parse_identifier(lexer: Lexer) -> str:
        identifier = lexer.assert_tokenkind(IdentifierToken)
        assert isinstance(identifier.contents, IdentifierToken)
        return identifier.contents.identifier

def parse_number(lexer: Lexer) -> int:
	number = lexer.assert_tokenkind(NumberToken)
	assert isinstance(number.contents, NumberToken)
	return number.contents.number

def parse_string(lexer: Lexer) -> str:
	string = lexer.assert_tokenkind(StringToken)
	assert isinstance(string.contents, StringToken)
	return string.contents.string

def parse_type_primary(lexer: Lexer) -> TypeExpression:
	base_type: TypeExpression
	if lexer.take_token(SymbolToken(Symbol.Open)):
		if lexer.take_token(SymbolToken(Symbol.Close)): return TupleTypeExpr([])

		types: List[TypeExpression] = [parse_type(lexer)]
		while lexer.take_token(SymbolToken(Symbol.Comma)):
			types.append(parse_type(lexer))
		lexer.assert_token(SymbolToken(Symbol.Close))
		base_type = TupleTypeExpr(types)
	elif lexer.take_token(SymbolToken(Symbol.OpenSquare)):
		type = parse_type(lexer)
		lexer.assert_token(SymbolToken(Symbol.CloseSquare))
		base_type = ListTypeExpr(type)
	else:
		name = parse_identifier(lexer)
		base_type = TypeName(name)

	while (opening_token := lexer.take_tokens(SymbolToken(Symbol.OpenSquare), SymbolToken(Symbol.Left))):
		assert isinstance(opening_token.contents, SymbolToken)
		opening = opening_token.contents.symbol

		if opening == Symbol.OpenSquare and lexer.check_tokenkind(NumberToken):
			number = parse_number(lexer)
			lexer.assert_token(SymbolToken(Symbol.CloseSquare))
			base_type = ArrayTypeExpr(base_type, number)
			continue

		opening2closing_map: Dict[Symbol, Symbol] = {
			Symbol.OpenSquare: Symbol.CloseSquare,
			Symbol.Left: Symbol.Right
		}
		assert opening in opening2closing_map, "Unreachable"
		closing = opening2closing_map[opening]

		if opening == Symbol.OpenSquare and lexer.take_token(SymbolToken(closing)):
			base_type = ListTypeExpr(base_type)
			continue

		generics: List[TypeExpression] = [parse_type(lexer)]
		while lexer.take_token(SymbolToken(Symbol.Comma)): generics.append(parse_type(lexer))

		lexer.assert_token(SymbolToken(closing))
		assert not isinstance(base_type, TypeSpecification)
		base_type = TypeSpecification(base_type, generics)

	return base_type

def parse_type(lexer: Lexer) -> TypeExpression:
	base_type = parse_type_primary(lexer)
	if not lexer.take_token(SymbolToken(Symbol.Arrow)): return base_type
	return_type = parse_type(lexer)
	return FunctionTypeExpr([base_type] if not isinstance(base_type, TupleTypeExpr) else base_type.types, return_type)

def parse_type_declaration(lexer: Lexer) -> TypeDeclaration:
	entry_name = parse_identifier(lexer)
	lexer.assert_token(SymbolToken(Symbol.Colon))
	entry_type = parse_type(lexer)
	return TypeDeclaration(entry_name, entry_type)

def parse_enum_entry(lexer: Lexer) -> EnumEntry:
	entry_name = parse_identifier(lexer)
	if not lexer.take_token(SymbolToken(Symbol.Open)):
		return EnumEntry(entry_name, [])

	entry_types: List[TypeExpression] = [parse_type(lexer)]
	while lexer.take_token(SymbolToken(Symbol.Comma)):
		entry_types.append(parse_type(lexer))
	lexer.assert_token(SymbolToken(Symbol.Close))
	return EnumEntry(entry_name, entry_types)

def parse_primary(lexer: Lexer) -> Expression:
	base_expression: Expression
	if lexer.take_token(SymbolToken(Symbol.Open)):
		if lexer.take_token(SymbolToken(Symbol.Close)):
			base_expression = TupleExpr([])
		else:
			elements: List[Expression] = [parse_expression(lexer)]
			singleton: bool = False
			while lexer.take_token(SymbolToken(Symbol.Comma)):
				if lexer.check_token(SymbolToken(Symbol.Close)) and len(elements) == 1:
					singleton = True
					break
				elements.append(parse_expression(lexer))
			lexer.assert_token(SymbolToken(Symbol.Close))
			if singleton or len(elements) > 1:
				base_expression = TupleExpr(elements)
			else:
				base_expression = elements[0]
	elif lexer.take_token(SymbolToken(Symbol.OpenSquare)):
		lexer.assert_token(SymbolToken(Symbol.Colon))
		element_type = parse_type(lexer)
		
		if lexer.take_token(SymbolToken(Symbol.CloseSquare)):
			base_expression = Array(element_type, [])
		else:
			lexer.assert_token(SymbolToken(Symbol.Comma))
			expressions: List[Expression] = [parse_expression(lexer)]
			if lexer.take_token(KeywordToken(Keyword.For)):
				variable = parse_identifier(lexer) # TODO: Pattern matching
				lexer.assert_token(KeywordToken(Keyword.In))
				expression = parse_expression(lexer)
				lexer.assert_token(SymbolToken(Symbol.CloseSquare))
				base_expression = LoopComprehension(element_type, expressions[0], variable, expression)
			else:
				while lexer.take_token(SymbolToken(Symbol.Comma)):
					expressions.append(parse_expression(lexer))
				lexer.assert_token(SymbolToken(Symbol.CloseSquare))
				base_expression = Array(element_type, expressions)
	elif lexer.check_tokenkind(StringToken):
		base_expression = String(parse_string(lexer))
	elif lexer.check_tokenkind(NumberToken):
		base_expression = Number(parse_number(lexer))
	else:
		base_expression = Variable(parse_identifier(lexer))

	while (token := lexer.take_tokens(SymbolToken(Symbol.Open), SymbolToken(Symbol.OpenSquare), SymbolToken(Symbol.Dot))):
		match token.contents:
			case SymbolToken(symbol):
				match symbol:
					case Symbol.Dot:
						next_token = lexer.next_token()
						match next_token.contents:
							case IdentifierToken(identifier=field):
								base_expression = FieldAccess(base_expression, field)
							case NumberToken(number=number):
								base_expression = FieldAccess(base_expression, str(number))
							case SymbolToken(symbol=symbol):
								match symbol:
									case Symbol.OpenCurly:
										if lexer.take_token(SymbolToken(Symbol.CloseCurly)):
											base_expression = StructInstantiation(base_expression, [])
										else:
											def parse_argument() -> Tuple[str, Expression]:
												parameter = parse_identifier(lexer)
												lexer.assert_token(SymbolToken(Symbol.Equal))
												return (parameter, parse_expression(lexer))

											struct_arguments: List[Tuple[str, Expression]] = [parse_argument()]
											while lexer.take_token(SymbolToken(Symbol.Comma)): struct_arguments.append(parse_argument())
											lexer.assert_token(SymbolToken(Symbol.CloseCurly))
											base_expression = StructInstantiation(base_expression, struct_arguments)
									case _:
										raise SyntaxError(f"{next_token.loc}: Unexpected symbol: {repr(str(symbol))}")
							case _:
								raise SyntaxError(f"{next_token.loc}: Unexpected: {next_token.contents}")
					case Symbol.Open:
						if lexer.take_token(SymbolToken(Symbol.Close)):
							base_expression = FunctionCall(base_expression, [])
						else:
							arguments: List[Expression] = [parse_expression(lexer)]
							while lexer.take_token(SymbolToken(Symbol.Comma)):
								arguments.append(parse_expression(lexer))
							lexer.assert_token(SymbolToken(Symbol.Close))
							base_expression = FunctionCall(base_expression, arguments)
					case Symbol.OpenSquare:
						index = parse_expression(lexer)
						lexer.assert_token(SymbolToken(Symbol.CloseSquare))
						base_expression = ArrayAccess(base_expression, index)
					case _: assert False, ("Unimplemented", symbol)
			case _: assert False, ("Unimplemented", token)

	return base_expression

def parse_unary(lexer: Lexer) -> Expression:
	if lexer.take_token(SymbolToken(Symbol.Tilde)): return Bnot(parse_unary(lexer))
	if lexer.take_token(SymbolToken(Symbol.Exclamation)): return Not(parse_unary(lexer))
	if lexer.take_token(SymbolToken(Symbol.Plus)): return UnaryPlus(parse_unary(lexer))
	if lexer.take_token(SymbolToken(Symbol.Dash)): return UnaryMinus(parse_unary(lexer))
	return parse_primary(lexer)

Precedence = Dict[Symbol, Callable[[Expression, Expression], Expression]]

precedences: List[Precedence] = [
	{Symbol.Dpipe: Or},
	{Symbol.Dampersand: And},
	{Symbol.Pipe: Bor},
	{Symbol.Carot: Bxor},
	{Symbol.Ampersand: Band},
	{Symbol.Dequal: Equal, Symbol.NotEqual: NotEqual},
	{Symbol.Left: LessThan, Symbol.Right: GreaterThan, Symbol.LesserEqual: LessThanOrEqual, Symbol.GreaterEqual: GreaterThanOrEqual},
	{Symbol.Dleft: ShiftLeft, Symbol.Dright: ShiftRight},
	{Symbol.Plus: Addition, Symbol.Dash: Subtract},
	{Symbol.Asterisk: Multiplication, Symbol.Slash: Division, Symbol.Percent: Modulo}
]

def parse_expression_at_level(lexer: Lexer, level: int=0) -> Expression:
	if level >= len(precedences): return parse_unary(lexer)
	left = parse_expression_at_level(lexer, level+1)
	tokens = [SymbolToken(symbol) for symbol in precedences[level]]
	while (token := lexer.take_tokens(*tokens)):
		assert isinstance(token.contents, SymbolToken)
		left = precedences[level][token.contents.symbol](left, parse_expression_at_level(lexer, level+1))
	return left

def parse_ternary(lexer: Lexer) -> Expression:
	expression = parse_expression_at_level(lexer)
	if not lexer.take_token(SymbolToken(Symbol.QuestionMark)): return expression
	if_true = parse_expression_at_level(lexer)
	lexer.assert_token(SymbolToken(Symbol.Colon))
	if_false = parse_ternary(lexer)
	return Ternary(expression, if_true, if_false)

def parse_expression(lexer: Lexer) -> Expression:
	if lexer.take_token(KeywordToken(Keyword.Lambda)):
		parameters: List[TypeDeclaration]
		if lexer.take_token(SymbolToken(Symbol.EqualArrow)):
			parameters = []
		else:
			parameters = [parse_type_declaration(lexer)]
			while lexer.take_token(SymbolToken(Symbol.Comma)):
				parameters.append(parse_type_declaration(lexer))
			lexer.assert_token(SymbolToken(Symbol.EqualArrow))
		return Lambda(parameters, parse_expression(lexer))
	return parse_ternary(lexer)

def is_valid_target(expression: Expression) -> bool:
	match expression:
		case FieldAccess(subexpression, _): return is_valid_target(subexpression)
		case Variable(_): return True
		case ArrayAccess(array, _): return is_valid_target(array)
		case _: assert False, ("Unimplemeneted", expression)
	assert False, "Unreachable"

def parse_statement(lexer: Lexer) -> Statement:
	if lexer.take_token(KeywordToken(Keyword.Enum)):
		enum_name = parse_identifier(lexer)
		lexer.assert_token(SymbolToken(Symbol.OpenCurly))

		if lexer.take_token(SymbolToken(Symbol.CloseCurly)): return EnumDefinition(enum_name, [])

		enum_entries: List[EnumEntry] = [parse_enum_entry(lexer)]
		while lexer.take_token(SymbolToken(Symbol.Comma)):
			enum_entries.append(parse_enum_entry(lexer))

		lexer.assert_token(SymbolToken(Symbol.CloseCurly))
		return EnumDefinition(enum_name, enum_entries)
	elif lexer.take_token(KeywordToken(Keyword.Struct)):
		struct_name = parse_identifier(lexer)
		lexer.assert_token(SymbolToken(Symbol.OpenCurly))

		if lexer.take_token(SymbolToken(Symbol.CloseCurly)): return StructDefinition(struct_name, [])

		struct_entries: List[TypeDeclaration] = [parse_type_declaration(lexer)]
		while lexer.take_token(SymbolToken(Symbol.Comma)):
			struct_entries.append(parse_type_declaration(lexer))

		lexer.assert_token(SymbolToken(Symbol.CloseCurly))
		return StructDefinition(struct_name, struct_entries)
	elif lexer.take_token(KeywordToken(Keyword.Func)):
		function_name = parse_identifier(lexer)
		lexer.assert_token(SymbolToken(Symbol.Open))
		function_arguments: List[TypeDeclaration] = []
		if not lexer.take_token(SymbolToken(Symbol.Close)):
			function_arguments.append(parse_type_declaration(lexer))
			while lexer.take_token(SymbolToken(Symbol.Comma)):
				function_arguments.append(parse_type_declaration(lexer))
			lexer.assert_token(SymbolToken(Symbol.Close))
		function_return_type: Optional[TypeExpression] = None
		if lexer.take_token(SymbolToken(Symbol.Arrow)):
			function_return_type = parse_type(lexer)

		function_body = parse_statement(lexer)

		return FunctionDefinition(function_name, function_arguments, function_return_type, function_body)
	elif lexer.take_token(KeywordToken(Keyword.If)):
		return IfStatement(
			parse_expression(lexer),
			parse_statement(lexer),
			parse_statement(lexer) if lexer.take_token(KeywordToken(Keyword.Else)) else None
		)
	elif lexer.take_token(KeywordToken(Keyword.Else)):
		assert False, "Unmatched else"
	elif lexer.take_token(KeywordToken(Keyword.While)):
		return WhileStatement(
			parse_expression(lexer),
			parse_statement(lexer)
		)
	elif lexer.take_token(KeywordToken(Keyword.Break)):
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return BreakStatement()
	elif lexer.take_token(KeywordToken(Keyword.Continue)):
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return ContinueStatement()
	elif lexer.take_token(KeywordToken(Keyword.Return)):
		expression = parse_expression(lexer)
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return ReturnStatement(expression)
	elif lexer.take_token(KeywordToken(Keyword.Do)):
		body = parse_statement(lexer)
		condition: Optional[Expression] = None
		if lexer.take_token(KeywordToken(Keyword.While)):
			condition = parse_expression(lexer)
			lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return DoWhileStatement(body, condition)
	elif lexer.take_token(KeywordToken(Keyword.Match)):
		value = parse_expression(lexer)
		lexer.assert_token(SymbolToken(Symbol.OpenCurly))

		cases: List[Tuple[Expression, Statement]] = []
		while lexer.take_token(KeywordToken(Keyword.Case)): cases.append((parse_expression(lexer), parse_statement(lexer)))
		lexer.assert_token(SymbolToken(Symbol.CloseCurly))
		return MatchStatement(value, cases)
	elif lexer.take_token(KeywordToken(Keyword.Assert)):
		condition = parse_expression(lexer)
		message = parse_expression(lexer) if lexer.take_token(SymbolToken(Symbol.Comma)) else None
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return AssertStatement(condition, message)
	elif lexer.take_token(KeywordToken(Keyword.For)):
		variable = parse_identifier(lexer) # TODO: Allow for pattern matching here
		lexer.assert_token(KeywordToken(Keyword.In))
		expression = parse_expression(lexer)
		body = parse_statement(lexer)
		return ForLoop(variable, expression, body)
	elif lexer.take_token(KeywordToken(Keyword.Import)):
		file = parse_string(lexer)
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return Import(file)
	elif lexer.take_token(KeywordToken(Keyword.Type)):
		name = parse_identifier(lexer)
		lexer.assert_token(SymbolToken(Symbol.Equal))
		type_expression = parse_type(lexer)
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		return TypeDefinition(name, type_expression)
	elif lexer.take_token(KeywordToken(Keyword.Defer)):
		statement = parse_statement(lexer)
		return DeferStatement(statement)
	elif lexer.check_tokenkind(KeywordToken) and not lexer.check_token(KeywordToken(Keyword.Lambda)): # TODO: Maybe use '\' for lambda instead of a keyword
		token = lexer.next_token()
		assert isinstance(token.contents, KeywordToken)
		raise SyntaxError(f"{token.loc}: Unexpected keyword: '{token.contents.keyword}'")
	elif lexer.take_token(SymbolToken(Symbol.OpenCurly)):
		statements: List[Statement] = []
		while not lexer.take_token(SymbolToken(Symbol.CloseCurly)):
			statements.append(parse_statement(lexer))
		return Statements(statements)
	else:
		expression = parse_expression(lexer)
		type: Optional[TypeExpression] = None
		if lexer.take_token(SymbolToken(Symbol.Colon)):
			assert isinstance(expression, Variable), "Cannot declare types for anything besides a variable"
			type = parse_type(lexer)

		if lexer.take_token(SymbolToken(Symbol.Equal)):
			assert is_valid_target(expression), ("Invalid target!", expression)
			right_expression = parse_expression(lexer)
			lexer.assert_token(SymbolToken(Symbol.Semicolon))
			return Assignment(expression, right_expression, type)
		lexer.assert_token(SymbolToken(Symbol.Semicolon))
		if type and isinstance(expression, Variable):
			return TypeDeclarationStatement(TypeDeclaration(expression.name, type))
		return ExpressionStatement(expression)