package patterns_test

import (
	"testing"

	"gitty.informatik.th-mannheim.de/steger/pr3-sose2026/go/04-design-pattern/patterns"
)

// MockObserver is a test implementation of the Observer interface, used to verify that the Notify method correctly calls the Update method on registered observers
type MockObserver struct {
	callCount int
}

// Update increments the callCount to track how many times the Update method has been called on this observer
func (mo *MockObserver) Update() {
	mo.callCount++
}

// Table driven tests for the Subject's Notify method, covering various scenarios of registered and unregistered observers
func TestSubject_Notify(t *testing.T) {
	type observer struct {
		MockObserver
		toRegister        bool
		expectedCallcount int
	}
	tests := []struct {
		name      string
		observers []*observer
	}{
		{"No observers", []*observer{}},
		{"Single unregistered observer", []*observer{&observer{MockObserver{0}, false, 0}}},
		{"Single registered observer", []*observer{&observer{MockObserver{0}, true, 1}}},
		{"Two registered observers", []*observer{&observer{MockObserver{0}, true, 1}, &observer{MockObserver{0}, true, 1}}},
		{"One registered and one unregistered observers", []*observer{&observer{MockObserver{0}, true, 1}, &observer{MockObserver{0}, false, 0}}},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			s := patterns.NewSubject()

			for _, o := range tt.observers {
				if o.toRegister {
					s.Register(o)
				}
			}

			s.Notify()

			for _, o := range tt.observers {
				if o.callCount != o.expectedCallcount {
					t.Errorf("%s: expected a callcount of %v, actual: %v", tt.name, o.expectedCallcount, o.callCount)
				}

				//reset callcount & unregister
				o.callCount = 0
				s.Unregister(o)
			}

			//call notify when all observers are unregistered
			s.Notify()

			//expect a callcount of 0
			for _, o := range tt.observers {
				if o.callCount != 0 {
					t.Errorf("%s: expected a callcount of 0, actual: %v", tt.name, o.callCount)
				}
			}
		})
	}
}