package units

import "testing"

func TestRegistryResolve(t *testing.T) {
	reg := NewRegistry()
	if err := reg.Register(StaticFactory{UnitSystem: "us", Converter: USConverter{}}); err != nil {
		t.Fatalf("register us: %v", err)
	}
	if err := reg.Register(StaticFactory{UnitSystem: "metric", Converter: MetricConverter{}}); err != nil {
		t.Fatalf("register metric: %v", err)
	}

	converter, err := reg.Resolve("US")
	if err != nil {
		t.Fatalf("resolve us: %v", err)
	}
	if converter.System() != "us" {
		t.Fatalf("expected us converter, got %q", converter.System())
	}

	converter, err = reg.Resolve(" metric ")
	if err != nil {
		t.Fatalf("resolve metric: %v", err)
	}
	if converter.System() != "metric" {
		t.Fatalf("expected metric converter, got %q", converter.System())
	}
}

func TestRegistryRejectsInvalidRegistration(t *testing.T) {
	reg := NewRegistry()
	if err := reg.Register(nil); err == nil {
		t.Fatalf("expected error for nil factory")
	}

	if err := reg.Register(StaticFactory{UnitSystem: "", Converter: USConverter{}}); err == nil {
		t.Fatalf("expected error for empty unit system")
	}

	if err := reg.Register(StaticFactory{UnitSystem: "us", Converter: nil}); err == nil {
		t.Fatalf("expected error for nil converter")
	}

	if err := reg.Register(StaticFactory{UnitSystem: "us", Converter: USConverter{}}); err != nil {
		t.Fatalf("register us: %v", err)
	}
	if err := reg.Register(StaticFactory{UnitSystem: "US", Converter: USConverter{}}); err == nil {
		t.Fatalf("expected duplicate registration error")
	}
}

func TestRegistryResolveUnknown(t *testing.T) {
	reg := NewRegistry()
	if err := reg.Register(StaticFactory{UnitSystem: "us", Converter: USConverter{}}); err != nil {
		t.Fatalf("register us: %v", err)
	}

	if _, err := reg.Resolve("metric"); err == nil {
		t.Fatalf("expected unsupported unit system error")
	}
}