package updates

import (
	"context"
	"testing"

	"telesrv/internal/domain"
	"telesrv/internal/store/memory"
)

func seedEvent(t *testing.T, events *memory.UpdateEventStore, userID int64, pts int) {
	t.Helper()
	if err := events.Append(context.Background(), userID, domain.UpdateEvent{
		Type:     domain.UpdateEventNewMessage,
		Pts:      pts,
		PtsCount: 1,
		Date:     1700000000 + pts,
		Message: domain.Message{
			ID:          pts,
			OwnerUserID: userID,
			Peer:        domain.Peer{Type: domain.PeerTypeUser, ID: domain.OfficialSystemUserID},
			From:        domain.Peer{Type: domain.PeerTypeUser, ID: domain.OfficialSystemUserID},
		},
	}); err != nil {
		t.Fatalf("seed event pts=%d: %v", pts, err)
	}
}

// TestGetDifferenceStopsAtHole：getDifference 只返回从 from 起连续的事件，遇在途空洞即截断，
// State.Pts 取最后连续值；后续事件到齐后下次拉取可继续，绝不跳过空洞。
func TestGetDifferenceStopsAtHole(t *testing.T) {
	ctx := context.Background()
	var authKeyID [8]byte
	userID := int64(1000000001)
	events := memory.NewUpdateEventStore()
	svc := NewService(memory.NewUpdateStateStore(), events)

	// pts 1,2,3 已提交，4 在途（缺），5,6 已提交 → 连续只到 3。
	for _, p := range []int{1, 2, 3, 5, 6} {
		seedEvent(t, events, userID, p)
	}
	diff, err := svc.GetDifference(ctx, authKeyID, userID, domain.UpdateState{})
	if err != nil {
		t.Fatalf("GetDifference: %v", err)
	}
	if len(diff.Events) != 3 || diff.State.Pts != 3 {
		t.Fatalf("diff = %d events, state.pts %d; want 3 连续事件、止于空洞(pts=3)", len(diff.Events), diff.State.Pts)
	}
	if diff.Partial {
		t.Fatalf("Partial=true，want false（被空洞而非 limit 截断）")
	}

	// 补上 pts=4（在途事务提交）后，从 3 继续应拿到 4,5,6。
	seedEvent(t, events, userID, 4)
	diff, err = svc.GetDifference(ctx, authKeyID, userID, domain.UpdateState{Pts: 3})
	if err != nil {
		t.Fatalf("GetDifference after fill: %v", err)
	}
	if len(diff.Events) != 3 || diff.State.Pts != 6 {
		t.Fatalf("events after gap filled = %d, state.pts %d; want 4,5,6 到 pts=6", len(diff.Events), diff.State.Pts)
	}
}

// TestGetDifferenceSliceOnLimit：连续事件填满 limit 时返回 Partial(=differenceSlice)，
// State.Pts 为中间态；客户端据此续拉，最终一页 Partial=false。
func TestGetDifferenceSliceOnLimit(t *testing.T) {
	ctx := context.Background()
	var authKeyID [8]byte
	userID := int64(1000000002)
	events := memory.NewUpdateEventStore()
	svc := NewService(memory.NewUpdateStateStore(), events)

	total := getDifferenceLimit + 25
	for p := 1; p <= total; p++ {
		seedEvent(t, events, userID, p)
	}
	diff, err := svc.GetDifference(ctx, authKeyID, userID, domain.UpdateState{})
	if err != nil {
		t.Fatalf("GetDifference: %v", err)
	}
	if len(diff.Events) != getDifferenceLimit || !diff.Partial || diff.State.Pts != getDifferenceLimit {
		t.Fatalf("第一页 = %d events partial %v state.pts %d; want %d/true/%d",
			len(diff.Events), diff.Partial, diff.State.Pts, getDifferenceLimit, getDifferenceLimit)
	}

	diff, err = svc.GetDifference(ctx, authKeyID, userID, domain.UpdateState{Pts: getDifferenceLimit})
	if err != nil {
		t.Fatalf("GetDifference page2: %v", err)
	}
	if len(diff.Events) != 25 || diff.Partial || diff.State.Pts != total {
		t.Fatalf("第二页 = %d events partial %v state.pts %d; want 25/false/%d",
			len(diff.Events), diff.Partial, diff.State.Pts, total)
	}
}

// TestGetStateReportsContiguousNotMax：getState 报告最大连续 pts，而非最大已提交 pts，
// 避免首次登录基线越过在途空洞而丢消息。
func TestGetStateReportsContiguousNotMax(t *testing.T) {
	ctx := context.Background()
	var authKeyID [8]byte
	userID := int64(1000000003)
	events := memory.NewUpdateEventStore()
	svc := NewService(memory.NewUpdateStateStore(), events)

	for _, p := range []int{1, 2, 3, 5, 6} { // 4 在途空洞，最大已提交=6
		seedEvent(t, events, userID, p)
	}
	st, err := svc.GetState(ctx, authKeyID, userID)
	if err != nil {
		t.Fatalf("GetState: %v", err)
	}
	if st.Pts != 3 {
		t.Fatalf("GetState.Pts=%d, want 3（最大连续，而非最大已提交 6）", st.Pts)
	}
}

func TestGetStateDoesNotConfirmUnfetchedEvents(t *testing.T) {
	ctx := context.Background()
	var authKeyID [8]byte
	authKeyID[0] = 7
	userID := int64(1000000004)
	events := memory.NewUpdateEventStore()
	states := memory.NewUpdateStateStore()
	svc := NewService(states, events)

	seedEvent(t, events, userID, 1)
	if err := states.Save(ctx, authKeyID, userID, domain.UpdateState{Pts: 1, Date: 1700000001}); err != nil {
		t.Fatalf("Save state: %v", err)
	}
	seedEvent(t, events, userID, 2)

	st, err := svc.GetState(ctx, authKeyID, userID)
	if err != nil {
		t.Fatalf("GetState: %v", err)
	}
	if st.Pts != 1 {
		t.Fatalf("GetState.Pts=%d, want existing confirmed pts=1", st.Pts)
	}

	diff, err := svc.GetDifference(ctx, authKeyID, userID, st)
	if err != nil {
		t.Fatalf("GetDifference: %v", err)
	}
	if len(diff.Events) != 1 || diff.Events[0].Pts != 2 || diff.State.Pts != 2 {
		t.Fatalf("diff = %+v, want one event at pts=2 and confirmed state pts=2", diff)
	}
	st, err = svc.GetState(ctx, authKeyID, userID)
	if err != nil {
		t.Fatalf("GetState after difference: %v", err)
	}
	if st.Pts != 2 {
		t.Fatalf("GetState after difference pts=%d, want confirmed pts=2", st.Pts)
	}
}