package history

import (
	"context"
	"errors"
	"io"
	"log/slog"
	"strings"
	"testing"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/db"
)

// testLogger returns a logger that writes nowhere, keeping test output clean.
func testLogger() *slog.Logger {
	return slog.New(slog.NewTextHandler(io.Discard, nil))
}

// newStore opens an isolated in-memory DB and returns a Store on it.
func newStore(t *testing.T) *Store {
	t.Helper()
	ctx := context.Background()
	conn, err := db.Open(ctx, ":memory:", testLogger())
	if err != nil {
		t.Fatalf("open memory db: %v", err)
	}
	t.Cleanup(func() { _ = conn.Close() })
	st, err := NewStore(ctx, conn, testLogger())
	if err != nil {
		t.Fatalf("new store: %v", err)
	}
	return st
}

func TestNewStoreNilDB(t *testing.T) {
	t.Parallel()
	if _, err := NewStore(context.Background(), nil, testLogger()); !errors.Is(err, ErrNilDB) {
		t.Fatalf("err = %v, want wrap of ErrNilDB", err)
	}
}

func TestAppendAndListNewestFirst(t *testing.T) {
	t.Parallel()
	st := newStore(t)
	ctx := context.Background()

	for i, ts := range []int64{1000, 2000, 3000} {
		m := Message{SessionID: MainSessionID, Role: RoleUser, Content: "hi", CreatedAt: ts}
		if err := st.Append(ctx, m); err != nil {
			t.Fatalf("append %d: %v", i, err)
		}
	}

	msgs, err := st.List(ctx, MainSessionID, 0, 50)
	if err != nil {
		t.Fatalf("list: %v", err)
	}
	if len(msgs) != 3 {
		t.Fatalf("len = %d, want 3", len(msgs))
	}
	// Newest first.
	if msgs[0].CreatedAt != 3000 || msgs[1].CreatedAt != 2000 || msgs[2].CreatedAt != 1000 {
		t.Fatalf("order = %+v, want [3000 2000 1000]", []int64{msgs[0].CreatedAt, msgs[1].CreatedAt, msgs[2].CreatedAt})
	}
	// Id/timestamp assigned when the caller omits them.
	empty := Message{SessionID: MainSessionID, Role: RoleAssistant, Content: "ok"}
	if err := st.Append(ctx, empty); err != nil {
		t.Fatalf("append no ts: %v", err)
	}
	msgs, err = st.List(ctx, MainSessionID, 0, 50)
	if err != nil {
		t.Fatalf("list after append: %v", err)
	}
	if msgs[0].ID == "" || msgs[0].CreatedAt == 0 {
		t.Fatalf("append did not fill id/created_at: %+v", msgs[0])
	}
}

func TestListPaginationBefore(t *testing.T) {
	t.Parallel()
	st := newStore(t)
	ctx := context.Background()

	for _, ts := range []int64{1000, 2000, 3000, 4000, 5000, 6000} {
		if err := st.Append(ctx, Message{SessionID: MainSessionID, Role: RoleUser, Content: "x", CreatedAt: ts}); err != nil {
			t.Fatalf("append %d: %v", ts, err)
		}
	}

	// First page: newest 2.
	page, err := st.List(ctx, MainSessionID, 0, 2)
	if err != nil {
		t.Fatalf("first page: %v", err)
	}
	if len(page) != 2 || page[0].CreatedAt != 6000 || page[1].CreatedAt != 5000 {
		t.Fatalf("first page = %+v, want [6000 5000]", page)
	}
	// Cursor on the page's oldest (5000) → older page [4000 3000].
	next, err := st.List(ctx, MainSessionID, page[1].CreatedAt, 2)
	if err != nil {
		t.Fatalf("next page: %v", err)
	}
	if len(next) != 2 || next[0].CreatedAt != 4000 || next[1].CreatedAt != 3000 {
		t.Fatalf("next page = %+v, want [4000 3000]", next)
	}
	// Past the start → empty.
	tail, err := st.List(ctx, MainSessionID, 1000, 50)
	if err != nil {
		t.Fatalf("tail: %v", err)
	}
	if len(tail) != 0 {
		t.Fatalf("tail = %+v, want empty", tail)
	}
}

func TestRecentChronological(t *testing.T) {
	t.Parallel()
	st := newStore(t)
	ctx := context.Background()

	for _, ts := range []int64{1000, 2000, 3000, 4000, 5000} {
		if err := st.Append(ctx, Message{SessionID: MainSessionID, Role: RoleUser, Content: "x", CreatedAt: ts}); err != nil {
			t.Fatalf("append %d: %v", ts, err)
		}
	}
	recent, err := st.Recent(ctx, MainSessionID, 3)
	if err != nil {
		t.Fatalf("recent: %v", err)
	}
	if len(recent) != 3 || recent[0].CreatedAt != 3000 || recent[1].CreatedAt != 4000 || recent[2].CreatedAt != 5000 {
		t.Fatalf("recent = %+v, want [3000 4000 5000]", recent)
	}
}

func TestNewSubSessionAndListSessions(t *testing.T) {
	t.Parallel()
	st := newStore(t)
	ctx := context.Background()

	// Main session exists by default.
	sessions, err := st.ListSessions(ctx)
	if err != nil {
		t.Fatalf("list sessions initial: %v", err)
	}
	if len(sessions) != 1 || sessions[0].ID != MainSessionID || sessions[0].Type != SessionMain {
		t.Fatalf("initial sessions = %+v, want [main web]", sessions)
	}

	id, err := st.NewSubSession(ctx, "owner")
	if err != nil {
		t.Fatalf("new sub: %v", err)
	}
	if !strings.HasPrefix(id, MainSessionID+":") {
		t.Fatalf("sub id = %q, want prefix web:", id)
	}

	sessions, err = st.ListSessions(ctx)
	if err != nil {
		t.Fatalf("list sessions: %v", err)
	}
	if len(sessions) != 2 || sessions[0].ID != MainSessionID || sessions[0].Type != SessionMain {
		t.Fatalf("sessions[0] = %+v, want main web first", sessions[0])
	}
	if sessions[1].ID != id || sessions[1].Type != SessionSub {
		t.Fatalf("sessions[1] = %+v, want sub %s", sessions[1], id)
	}
}

func TestDeleteSession(t *testing.T) {
	t.Parallel()
	st := newStore(t)
	ctx := context.Background()

	sub, err := st.NewSubSession(ctx, "owner")
	if err != nil {
		t.Fatalf("new sub: %v", err)
	}
	if err := st.Append(ctx, Message{SessionID: sub, Role: RoleUser, Content: "x", CreatedAt: 1000}); err != nil {
		t.Fatalf("append: %v", err)
	}

	if err := st.DeleteSession(ctx, sub); err != nil {
		t.Fatalf("delete sub: %v", err)
	}
	msgs, err := st.List(ctx, sub, 0, 50)
	if err != nil {
		t.Fatalf("list after delete: %v", err)
	}
	if len(msgs) != 0 {
		t.Fatalf("messages after delete = %+v, want empty", msgs)
	}
	sessions, err := st.ListSessions(ctx)
	if err != nil {
		t.Fatalf("list sessions after delete: %v", err)
	}
	if len(sessions) != 1 {
		t.Fatalf("sessions after delete = %+v, want [main]", sessions)
	}

	// Main session is immutable.
	if err := st.DeleteSession(ctx, MainSessionID); !errors.Is(err, ErrImmutableMain) {
		t.Fatalf("delete main err = %v, want ErrImmutableMain", err)
	}
}