package session

import (
	"testing"

	"nub/internal/llm"
)

func textMsg(role llm.Role, text string) llm.Message {
	return llm.Message{Role: role, Content: []llm.Block{{Kind: llm.KindText, Text: text}}}
}

func TestSession_PathToHead_OrdersRootToHead(t *testing.T) {
	s := New("s1")
	n1 := NewNode("", textMsg(llm.RoleUser, "one"), NodeMeta{})
	must(t, s.Append(n1))
	n2 := NewNode(n1.ID, textMsg(llm.RoleAssistant, "two"), NodeMeta{})
	must(t, s.Append(n2))
	n3 := NewNode(n2.ID, textMsg(llm.RoleUser, "three"), NodeMeta{})
	must(t, s.Append(n3))

	msgs := s.PathToHead()
	if len(msgs) != 3 {
		t.Fatalf("len = %d, want 3", len(msgs))
	}
	want := []string{"one", "two", "three"}
	for i, w := range want {
		if msgs[i].Content[0].Text != w {
			t.Errorf("msgs[%d] = %q, want %q", i, msgs[i].Content[0].Text, w)
		}
	}
}

func TestSession_PathToHead_StopsAtSummary(t *testing.T) {
	s := New("s1")
	n1 := NewNode("", textMsg(llm.RoleUser, "old-1"), NodeMeta{})
	must(t, s.Append(n1))
	n2 := NewNode(n1.ID, textMsg(llm.RoleAssistant, "old-2"), NodeMeta{})
	must(t, s.Append(n2))

	summary := &Node{
		ID:       "summary-1",
		ParentID: n2.ID,
		Kind:     NodeSummary,
		Message:  textMsg(llm.RoleUser, "SUMMARY of old-1/old-2"),
		Replaces: []string{n1.ID, n2.ID},
	}
	must(t, s.Append(summary))

	n3 := NewNode(summary.ID, textMsg(llm.RoleUser, "new"), NodeMeta{})
	must(t, s.Append(n3))

	msgs := s.PathToHead()
	if len(msgs) != 2 {
		t.Fatalf("len = %d, want 2 (summary + new)", len(msgs))
	}
	if msgs[0].Content[0].Text != "SUMMARY of old-1/old-2" {
		t.Errorf("msgs[0] = %q", msgs[0].Content[0].Text)
	}
	if msgs[1].Content[0].Text != "new" {
		t.Errorf("msgs[1] = %q", msgs[1].Content[0].Text)
	}
}

func TestSession_Branch_CreatesSecondPath(t *testing.T) {
	s := New("s1")
	n1 := NewNode("", textMsg(llm.RoleUser, "root"), NodeMeta{})
	must(t, s.Append(n1))
	n2a := NewNode(n1.ID, textMsg(llm.RoleAssistant, "branch-a"), NodeMeta{})
	must(t, s.Append(n2a))

	must(t, s.Branch(n1.ID))
	n2b := NewNode(n1.ID, textMsg(llm.RoleAssistant, "branch-b"), NodeMeta{})
	must(t, s.Append(n2b))

	if s.Head != n2b.ID {
		t.Fatalf("head = %s, want %s", s.Head, n2b.ID)
	}

	must(t, s.Branch(n2a.ID))
	msgsA := s.PathToHead()
	if msgsA[len(msgsA)-1].Content[0].Text != "branch-a" {
		t.Errorf("branch a tip = %q", msgsA[len(msgsA)-1].Content[0].Text)
	}

	must(t, s.Branch(n2b.ID))
	msgsB := s.PathToHead()
	if msgsB[len(msgsB)-1].Content[0].Text != "branch-b" {
		t.Errorf("branch b tip = %q", msgsB[len(msgsB)-1].Content[0].Text)
	}
}

func TestSession_Append_RejectsUnknownParent(t *testing.T) {
	s := New("s1")
	n := NewNode("does-not-exist", textMsg(llm.RoleUser, "x"), NodeMeta{})
	if err := s.Append(n); err == nil {
		t.Fatal("expected error for unknown parent")
	}
}

func must(t *testing.T, err error) {
	t.Helper()
	if err != nil {
		t.Fatal(err)
	}
}