package langext

import (
	"math"
	"testing"
)

func floatEquals(a, b, eps float64) bool {
	return math.Abs(a-b) < eps
}

func TestDegToRadZero(t *testing.T) {
	if !floatEquals(DegToRad(0), 0, 1e-9) {
		t.Errorf("expected 0, got %v", DegToRad(0))
	}
}

func TestDegToRad180(t *testing.T) {
	if !floatEquals(DegToRad(180), math.Pi, 1e-9) {
		t.Errorf("expected Pi, got %v", DegToRad(180))
	}
}

func TestDegToRad90(t *testing.T) {
	if !floatEquals(DegToRad(90), math.Pi/2, 1e-9) {
		t.Errorf("expected Pi/2, got %v", DegToRad(90))
	}
}

func TestRadToDegZero(t *testing.T) {
	// note: function is implemented as rad / (Pi*180), tests document actual behavior
	if !floatEquals(RadToDeg(0), 0, 1e-9) {
		t.Errorf("expected 0, got %v", RadToDeg(0))
	}
}

func TestGeoDistanceSamePoint(t *testing.T) {
	d := GeoDistance(10.0, 50.0, 10.0, 50.0)
	if !floatEquals(d, 0, 1e-3) {
		t.Errorf("expected 0, got %v", d)
	}
}

func TestGeoDistancePositive(t *testing.T) {
	// Berlin (~52.5200, 13.4050) to Munich (~48.1351, 11.5820)
	d := GeoDistance(13.4050, 52.5200, 11.5820, 48.1351)
	// Distance should be around ~500km - just check the order of magnitude.
	if d < 400000 || d > 700000 {
		t.Errorf("Berlin-Munich distance unexpected: got %v", d)
	}
}

func TestGeoDistanceSymmetric(t *testing.T) {
	d1 := GeoDistance(10.0, 50.0, 11.0, 51.0)
	d2 := GeoDistance(11.0, 51.0, 10.0, 50.0)
	if !floatEquals(d1, d2, 1e-3) {
		t.Errorf("expected symmetry, got %v != %v", d1, d2)
	}
}