package calc

import (
	"errors"
	"testing"
)

func TestNewEngine_DefaultsToDEC(t *testing.T) {
	e := NewEngine()
	if e.CurrentBase() != BaseDEC {
		t.Errorf("expected DEC, got %s", e.CurrentBase())
	}
	if !e.IsInteger() {
		t.Error("0 should be integer")
	}
}

func TestCycleBase_IntegerOK(t *testing.T) {
	e := NewEngine()
	e.value = 42 // integer

	if err := e.CycleBase(); err != nil {
		t.Fatalf("unexpected error cycling from integer: %v", err)
	}
	if e.CurrentBase() != BaseHEX {
		t.Errorf("expected HEX after one cycle, got %s", e.CurrentBase())
	}
}

func TestCycleBase_FractionalCERR(t *testing.T) {
	e := NewEngine()
	e.value = 23.0 / 6.0 // 3.8333...

	err := e.CycleBase()
	if !errors.Is(err, ErrConversionNotPossible) {
		t.Fatalf("expected ErrConversionNotPossible, got %v", err)
	}
	if e.CurrentBase() != BaseDEC {
		t.Error("base must not change on CERR")
	}
}

// TODO (phase 2): more tests for FormatForDisplay (hex/bin/oct of integers),
// ops, clears, entry, combined fractional + multiple BASE presses, etc.