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

// Execute executes an operation on a register with a value operand.
func (f *Function) Execute(operation token.Token, register cpu.Register, value *expression.Expression) error {
	if value.IsLeaf() {
		return f.ExecuteLeaf(operation, register, value.Token)
	}

	temporary, found := f.CPU.FindFree(f.CPU.General)

	if !found {
		panic("no free registers")
	}

	f.CPU.Use(temporary)
	defer f.CPU.Free(temporary)
	err := f.ExpressionToRegister(value, temporary)

	if err != nil {
		return err
	}

	return f.ExecuteRegisterRegister(operation, register, temporary)
}

// ExecuteLeaf performs an operation on a register with the given leaf operand.
func (f *Function) ExecuteLeaf(operation token.Token, register cpu.Register, 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.ExecuteRegisterNumber(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.ExecuteRegisterRegister(operation, register, variable.Register)
	}

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

// ExecuteRegisterNumber performs an operation on a register and a number.
func (f *Function) ExecuteRegisterNumber(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)

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

	default:
		return errors.New(&errors.InvalidOperator{Operator: operation.Text()}, f.File, operation.Position)
	}

	return nil
}

// ExecuteRegisterRegister performs an operation on two registers.
func (f *Function) ExecuteRegisterRegister(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)

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

	default:
		return errors.New(&errors.InvalidOperator{Operator: operation.Text()}, f.File, operation.Position)
	}

	return nil
}