package core

import (
	"fmt"
	"math"

	"git.urbach.dev/cli/q/src/asm"
	"git.urbach.dev/cli/q/src/cpu"
	"git.urbach.dev/cli/q/src/errors"
	"git.urbach.dev/cli/q/src/expression"
	"git.urbach.dev/cli/q/src/types"
)

// DotToRegister moves a constant or a function address into the given register.
func (f *Function) DotToRegister(node *expression.Expression, register cpu.Register) (types.Type, error) {
	left := node.Children[0]
	right := node.Children[1]
	leftText := left.Token.Text(f.File.Bytes)
	rightText := right.Token.Text(f.File.Bytes)
	variable := f.VariableByName(leftText)

	if variable != nil {
		field := variable.Value.Typ.(*types.Pointer).To.(*types.Struct).FieldByName(rightText)

		memory := asm.Memory{
			Base:           variable.Value.Register,
			Offset:         int8(field.Offset),
			OffsetRegister: math.MaxUint8,
			Length:         byte(field.Type.Size()),
		}

		f.MemoryRegister(asm.LOAD, memory, register)
		return field.Type, nil
	}

	constant, isConst := f.All.Constants[f.Package+"."+leftText+"."+rightText]

	if isConst {
		number, err := ToNumber(constant.Token, constant.File)

		if err != nil {
			return nil, err
		}

		f.SaveRegister(register)
		f.RegisterNumber(asm.MOVE, register, number)
		return types.AnyInt, nil
	}

	uniqueName := fmt.Sprintf("%s.%s", leftText, rightText)
	function, exists := f.All.Functions[uniqueName]

	if exists {
		f.File.Imports[leftText].Used = true
		f.RegisterLabel(asm.MOVE, register, function.UniqueName)
		return types.AnyPointer, nil
	}

	return nil, errors.New(&errors.UnknownIdentifier{Name: uniqueName}, f.File, left.Token.Position)
}