package core

import (
	"fmt"
	"math"

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

// EvaluateDot evaluates an access with the dot operator.
func (f *Function) EvaluateDot(expr *expression.Expression) (eval.Value, error) {
	left := expr.Children[0]
	right := expr.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)

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

		return value, 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
		}

		value := eval.Number{
			Typ:    types.AnyInt,
			Number: number,
		}

		return value, nil
	}

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

	if exists {
		f.File.Imports[leftText].Used = true

		value := eval.Label{
			Typ:   types.AnyPointer,
			Label: function.UniqueName,
		}

		return value, nil
	}

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