from llvmlite import ir

from AST import Node, NodeType, Program, Expression
from AST import ExpressionStatement, AssignmentStatement, BlockStatement, ReturnStatement, FunctionStatement, ReassignStatement, IfStatement
from AST import InfixExpression, CallExpression
from AST import IntegerLiteral, FloatLiteral, IdentifierLiteral, BooleanLiteral, StringLiteral
from AST import FunctionParameter

from environment import Environment


class Compiler:
	def __init__(self) -> None:
		self.type_map: dict[str, ir.type] = {
			"Bool": ir.IntType(1),
			"Byte": ir.IntType(8),
			"Short": ir.IntType(16),
			"Int": ir.IntType(32),
			"Long": ir.IntType(64),
			"Float": ir.FloatType(),
			"Double": ir.DoubleType(),
			"String": ir.PointerType(ir.IntType(8)),
			"Nil": ir.VoidType()
		}

		self.module: ir.Module = ir.Module("main")
		self.builder: ir.IRBuilder = ir.IRBuilder()
		self.environment: Environment = Environment()
		self.errors: list[str] = []

		self.counter = 0

		self.__initialize_builtins()

	def __initialize_builtins(self) -> None:
		def __init_print() -> ir.Function:
			fnty: ir.FunctionType = ir.FunctionType(
				self.type_map["Int"],
				[ir.IntType(8).as_pointer()],
				var_arg=True
			)
			return ir.Function(self.module, fnty, "printf")

		def __init_booleans() -> tuple[ir.GlobalVariable, ir.GlobalVariable]:
			bool_type: ir.Type = self.type_map["Bool"]

			true_var = ir.GlobalVariable(self.module, bool_type, "true")
			true_var.initializer = ir.Constant(bool_type, 1)
			true_var.global_constant = True

			false_var = ir.GlobalVariable(self.module, bool_type, "false")
			false_var.initializer = ir.Constant(bool_type, 0)
			false_var.global_constant = True

			return true_var, false_var
		
		self.environment.define("print", __init_print(), ir.IntType(32))
		
		true_var, false_var = __init_booleans()
		self.environment.define("true", true_var, true_var.type)
		self.environment.define("false", false_var, false_var.type)

	def __increment_counter(self) -> int:
		self.counter += 1
		return self.counter

	def compile(self, node: Node) -> None:
		match node.type():
			case NodeType.Program:
				self.__visit_program(node)

			# Statements
			case NodeType.ExpressionStatement:
				self.__visit_expression_statement(node)
			case NodeType.AssignmentStatement:
				self.__visit_assignment_statement(node)
			case NodeType.FunctionStatement:
				self.__visit_function_statement(node)
			case NodeType.BlockStatement:
				self.__visit_block_statement(node)
			case NodeType.ReturnStatement:
				self.__visit_return_statement(node)
			case NodeType.ReassignStatement:
				self.__visit_reassign_statement(node)
			case NodeType.IfStatement:
				self.__visit_if_statement(node)

			# Expressions
			case NodeType.InfixExpression:
				self.__visit_infix_expression(node)
			case NodeType.CallExpression:
				self.__visit_call_expression(node)

	# region Visit Methods
	def __visit_program(self, node: Program) -> None:
		for stmt in node.statements:
			self.compile(stmt)

	# region Statements
	def __visit_expression_statement(self, node: ExpressionStatement) -> None:
		self.compile(node.expr)

	def __visit_assignment_statement(self, node: AssignmentStatement) -> None:
		name: str = node.name.value
		value: Expression = node.value
		value_type: str = node.value_type # TODO: implemented

		value, Type = self.__resolve_value(node=value)

		if self.environment.lookup(name) is None:
			# Define and allocate the new variable
			ptr = self.builder.alloca(Type)

			# Storing the value to the ptr
			self.builder.store(value, ptr)

			# Add the variable to the environment
			self.environment.define(name, ptr, Type)
		else:
			ptr, _ = self.environment.lookup(name)
			self.builder.store(value, ptr)

	def __visit_block_statement(self, node: BlockStatement) -> None:
		for stmt in node.statements:
			self.compile(stmt)

	def __visit_return_statement(self, node: ReturnStatement) -> None:
		value: Expression = node.return_value

		value, Type = self.__resolve_value(value)

		self.builder.ret(value)

	def __visit_function_statement(self, node: FunctionStatement) -> None:
		name: str = node.name.value
		body: BlockStatement = node.body

		params: list[FunctionParameter] = node.parameters
		param_names: list[str] = [p.name for p in params]
		param_types: list[ir.Type] = [self.type_map[p.value_type] for p in params]

		return_type: ir.Type = self.type_map[node.return_type]

		fnty: ir.FunctionType = ir.FunctionType(return_type, param_types)
		func: ir.Function = ir.Function(self.module, fnty, name)

		block: ir.Block = func.append_basic_block(f"{name}_entry")

		previous_builder = self.builder

		self.builder = ir.IRBuilder(block)

		# storing the pointers to each parameter
		params_ptr = []
		for i, typ in enumerate(param_types):
			ptr = self.builder.alloca(typ)
			self.builder.store(func.args[i], ptr)
			params_ptr.append(ptr)

		# adding the params to the environment		
		previous_env = self.environment		
		self.environment = Environment(parent=self.environment)
		for i, x in enumerate(zip(param_types, param_names)):
			typ = param_types[i]
			ptr = params_ptr[i]

			self.environment.define(x[1], ptr, typ)

		self.environment.define(name, func, return_type)

		self.compile(body)

		self.environment = previous_env
		self.environment.define(name, func, return_type)

		self.builder = previous_builder

	def __visit_reassign_statement(self, node: ReassignStatement) -> None:
		name: str = node.ident.value
		value: Expression = node.right_value

		value, Type = self.__resolve_value(value)

		if self.environment.lookup(name) is None:
			self.errors.append(f"Identifier {name} has not been declared before it was re-assigned.")
		else:
			ptr, _ = self.environment.lookup(name)
			self.builder.store(value, ptr)

	def __visit_if_statement(self, node: IfStatement) -> None:
		condition = node.condition
		consequence = node.consequence
		alternative = node.alternative

		test, _ = self.__resolve_value(condition)

		if alternative is None:
			with self.builder.if_then(test):
				self.compile(consequence)
		else:
			with self.builder.if_else(test) as (true, otherwise):
				# Creating a condition branch
				#      condition
				#        / \
				#     true  false
				#       /   \
				#      /     \
				# if block  else block
				with true:
					self.compile(consequence)

				with otherwise:
					self.compile(alternative)
	# endregion	

	# region Expressions
	def __visit_infix_expression(self, node: InfixExpression) -> None:
		operator: str = node.operator

		left_value, left_type = self.__resolve_value(node.left_node)
		right_value, right_type = self.__resolve_value(node.right_node)

		value = None
		Type = None
		if isinstance(right_type, ir.IntType) and isinstance(left_type, ir.IntType):
			Type = self.type_map["Int"]
			match operator:
				case "+":
					value = self.builder.add(left_value, right_value)
				case "-":
					value = self.builder.sub(left_value, right_value)
				case "*":
					value = self.builder.mul(left_value, right_value)
				case "/":
					value = self.builder.sdiv(left_value, right_value)
				case "%":
					value = self.builder.srem(left_value, right_value)
				case "^":
					# TODO
					pass
				case "<":
					value = self.builder.icmp_signed('<', left_value, right_value)
					Type = ir.IntType(1)
				case "<=":
					value = self.builder.icmp_signed('<=', left_value, right_value)
					Type = ir.IntType(1)
				case ">":
					value = self.builder.icmp_signed('>', left_value, right_value)
					Type = ir.IntType(1)
				case ">=":
					value = self.builder.icmp_signed('>=', left_value, right_value)
					Type = ir.IntType(1)
				case "==":
					value = self.builder.icmp_signed('==', left_value, right_value)
					Type = ir.IntType(1)
				case "!=":
					value = self.builder.icmp_signed('!=', left_value, right_value)
					Type = ir.IntType(1)
		elif isinstance(right_type, ir.FloatType) and isinstance(left_type, ir.FloatType):
			Type = self.type_map["Float"]
			match operator:
				case "+":
					value = self.builder.fadd(left_value, right_value)
				case "-":
					value = self.builder.fsub(left_value, right_value)
				case "*":
					value = self.builder.fmul(left_value, right_value)
				case "/":
					value = self.builder.fdiv(left_value, right_value)
				case "%":
					value = self.builder.frem(left_value, right_value)
				case "^":
					# TODO
					pass
				case "<":
					value = self.builder.fcmp_ordered('<', left_value, right_value)
					Type = ir.IntType(1)
				case "<=":
					value = self.builder.fcmp_ordered('<=', left_value, right_value)
					Type = ir.IntType(1)
				case ">":
					value = self.builder.fcmp_ordered('>', left_value, right_value)
					Type = ir.IntType(1)
				case ">=":
					value = self.builder.fcmp_ordered('>=', left_value, right_value)
					Type = ir.IntType(1)
				case "==":
					value = self.builder.fcmp_ordered('==', left_value, right_value)
					Type = ir.IntType(1)
				case "!=":
					value = self.builder.fcmp_ordered('!=', left_value, right_value)
					Type = ir.IntType(1)
		
		return value, Type
	
	def __visit_call_expression(self, node: CallExpression) -> tuple[ir.Instruction, ir.Type]:
		name: str = node.function.value
		params: list[Expression] = node.arguments

		args = []
		types = []
		if len(params) > 0:
			for x in params:
				p_val, p_type = self.__resolve_value(x)
				args.append(p_val)
				types.append(p_type)

		match name:
			case "print":
				ret = self.builtin_print(params=args, return_type=types[0])
				ret_type = self.type_map["Int"]
			case _:
				func, ret_type = self.environment.lookup(name)
				ret = self.builder.call(func, args)

		return ret, ret_type
	# endregion

	# endregion

	# region Helper Methods
	def __resolve_value(self, node: Expression) -> tuple[ir.Value, ir.Type]:
		match node.type():
			case NodeType.IntegerLiteral:
				node: IntegerLiteral = node
				value, Type = node.value, self.type_map['Int']
				return ir.Constant(Type, value), Type
			case NodeType.FloatLiteral:
				node: FloatLiteral = node
				value, Type = node.value, self.type_map['Float']
				return ir.Constant(Type, value), Type
			case NodeType.IdentifierLiteral:
				node: IdentifierLiteral = node
				ptr, Type = self.environment.lookup(node.value)
				return self.builder.load(ptr), Type
			case NodeType.BooleanLiteral:
				node: BooleanLiteral = node
				return ir.Constant(ir.IntType(1), 1 if node.value else 0), ir.IntType(1)
			case NodeType.StringLiteral:
				node: StringLiteral = node
				string, Type = self.__convert_string(node.value)
				return string, Type

			# expression value
			case NodeType.InfixExpression:
				return self.__visit_infix_expression(node)
			case NodeType.CallExpression:
				return self.__visit_call_expression(node)
			
	def __convert_string(self, string: str) -> tuple[ir.Constant, ir.ArrayType]:
		string = string.replace("\\n", "\n\0")

		fmt: str = f"{string}\0"
		c_fmt: ir.Constant = ir.Constant(ir.ArrayType(ir.IntType(8), len(fmt)), bytearray(fmt.encode("utf-8")))

		global_fmt = ir.GlobalVariable(self.module, c_fmt.type, name=f"__str_{self.__increment_counter()}")
		global_fmt.linkage = "internal"
		global_fmt.global_constant = True
		global_fmt.initializer = c_fmt

		return global_fmt, global_fmt.type

	def builtin_print(self, params: list[ir.Instruction], return_type: ir.Type) -> None:
		func, _ = self.environment.lookup("print")

		c_str = self.builder.alloca(return_type)
		self.builder.store(params[0], c_str)

		rest_params = params[1:]

		if isinstance(params[0], ir.LoadInstr):
			# printing from a variable load instruction
			c_fmt: ir.LoadInstr = params[0]
			g_var_ptr = c_fmt.operands[0]
			string_val = self.builder.load(g_var_ptr)
			fmt_arg = self.builder.bitcast(string_val, ir.IntType(8).as_pointer())
			return self.builder.call(func, [fmt_arg, *rest_params])
		else:
			# printing from a normal string
			fmt_arg = self.builder.bitcast(self.module.get_global(f"__str_{self.counter}"), ir.IntType(8).as_pointer())
			return self.builder.call(func, [fmt_arg, *rest_params])
	# endregion