package build

import (
	"strconv"

	"git.akyoto.dev/cli/q/src/build/asm"
	"git.akyoto.dev/cli/q/src/build/cpu"
	"git.akyoto.dev/cli/q/src/build/token"
	"git.akyoto.dev/cli/q/src/errors"
)

// Calculate performs an operation on a register with the given operand.
func (f *Function) Calculate(register cpu.Register, operation token.Token, operand token.Token) error {
	switch operand.Kind {
	case token.Number:
		value := operand.Text()
		number, err := strconv.Atoi(value)

		if err != nil {
			return err
		}

		return f.CalculateRegisterNumber(operation, register, number)

	case token.Identifier:
		name := operand.Text()
		variable, exists := f.Variables[name]

		if !exists {
			return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, operand.Position)
		}

		return f.CalculateRegisterRegister(operation, register, variable.Register)
	}

	return errors.New(errors.NotImplemented, f.File, operation.Position)
}

// CalculateRegisterNumber performs an operation on a register and a number.
func (f *Function) CalculateRegisterNumber(operation token.Token, register cpu.Register, number int) error {
	switch operation.Text() {
	case "+", "+=":
		f.Assembler.RegisterNumber(asm.ADD, register, number)

	case "-", "-=":
		f.Assembler.RegisterNumber(asm.SUB, register, number)

	case "*", "*=":
		f.Assembler.RegisterNumber(asm.MUL, register, number)

	case "/", "/=":
		f.Assembler.RegisterNumber(asm.DIV, register, number)

	default:
		return errors.New(errors.NotImplemented, f.File, operation.Position)
	}

	return nil
}

// CalculateRegisterRegister performs an operation on two registers.
func (f *Function) CalculateRegisterRegister(operation token.Token, destination cpu.Register, source cpu.Register) error {
	switch operation.Text() {
	case "+", "+=":
		f.Assembler.RegisterRegister(asm.ADD, destination, source)

	case "-", "-=":
		f.Assembler.RegisterRegister(asm.SUB, destination, source)

	case "*", "*=":
		f.Assembler.RegisterRegister(asm.MUL, destination, source)

	case "/", "/=":
		f.Assembler.RegisterRegister(asm.DIV, destination, source)

	default:
		return errors.New(errors.NotImplemented, f.File, operation.Position)
	}

	return nil
}