package state

import "testing"

func TestValidTransitions(t *testing.T) {
	m := NewMachine(ConversationSession{CallID: "c"})
	steps := []ConversationEvent{
		{Type: EventCallStarted},
		{Type: EventGreetingPlayed},
		{Type: EventLanguageSelected, Language: LanguageRU},
		{Type: EventRegionSelected, Region: RegionSelection{Code: "almaty_city", Status: RegionSelected}},
		{Type: EventQuestionReceived, Question: "q"},
		{Type: EventAnswerCompleted},
		{Type: EventHandoffRequested},
		{Type: EventCallEnded},
	}
	want := []ConversationState{StateGreeting, StateReadyToHelp, StateReadyToHelp, StateReadyToHelp, StateQuestionAnswering, StateReadyToHelp, StateHandoff, StateEnded}
	for i, step := range steps {
		res, err := m.Apply(step)
		if err != nil {
			t.Fatalf("step %d: %v", i, err)
		}
		if res.To != want[i] {
			t.Fatalf("step %d state=%s want=%s", i, res.To, want[i])
		}
	}
	if len(m.Session().TransitionHistory) != len(steps) {
		t.Fatalf("transition history length mismatch")
	}
}

func TestInvalidTransitionsDoNotMutate(t *testing.T) {
	m := NewMachine(ConversationSession{CallID: "c"})
	if _, err := m.Apply(ConversationEvent{Type: EventQuestionReceived}); err == nil {
		t.Fatal("expected invalid transition")
	}
	if m.CurrentState() != StateCallStarted {
		t.Fatalf("state mutated to %s", m.CurrentState())
	}
	_, _ = m.Apply(ConversationEvent{Type: EventCallEnded})
	if _, err := m.Apply(ConversationEvent{Type: EventLanguageSelected, Language: LanguageRU}); err == nil {
		t.Fatal("expected ended state error")
	}
	if m.CurrentState() != StateEnded {
		t.Fatalf("ended state mutated to %s", m.CurrentState())
	}
}

func TestQuestionAllowedWithoutExplicitLanguageAndRegion(t *testing.T) {
	m := NewMachine(ConversationSession{CallID: "c", State: StateRegionSelection, Language: LanguageRU})
	if _, err := m.Apply(ConversationEvent{Type: EventQuestionReceived}); err == nil {
		t.Fatal("region selection state should not answer directly")
	}
	m = NewMachine(ConversationSession{CallID: "c", State: StateReadyToHelp, Region: RegionSelection{Code: "almaty_city", Status: RegionSelected}})
	if _, err := m.Apply(ConversationEvent{Type: EventQuestionReceived}); err == nil {
		return
	}
	t.Fatal("question should be allowed without explicit language")
}