package api

import (
	"context"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync"
	"testing"
	"time"
)

// syncRecorder is a ResponseRecorder safe to read while the handler writes.
type syncRecorder struct {
	*httptest.ResponseRecorder
	mu sync.Mutex
}

func (r *syncRecorder) Write(b []byte) (int, error) {
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.ResponseRecorder.Write(b)
}

func (r *syncRecorder) body() string {
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.Body.String()
}

// Last-Event-ID 0-0 on meta:events returns the whole current state — one set
// per record key, only the last carrying an id — then the live tail.
func TestMetaEventsSnapshotThenTail(t *testing.T) {
	stor := newTestStorage(t)
	s := &Server{storage: stor}
	for i, id := range []string{"R1", "R2"} {
		if err := stor.SetMetadataFlat(id, map[string]string{"title": "T", "n": string(rune('a' + i))}); err != nil {
			t.Fatal(err)
		}
	}

	ctx, cancel := context.WithCancel(context.Background())
	req := httptest.NewRequest(http.MethodGet, "/api/events/meta", nil).WithContext(ctx)
	req.Header.Set("Last-Event-ID", "0-0")
	rec := &syncRecorder{ResponseRecorder: httptest.NewRecorder()}
	done := make(chan struct{})
	go func() { s.handleEventsMeta(rec, req); close(done) }()

	waitFor := func(substr string) {
		t.Helper()
		deadline := time.Now().Add(5 * time.Second)
		for !strings.Contains(rec.body(), substr) {
			if time.Now().After(deadline) {
				t.Fatalf("timed out waiting for %q in:\n%s", substr, rec.body())
			}
			time.Sleep(20 * time.Millisecond)
		}
	}
	waitFor(`"key":"file:R2/title"`)
	if err := stor.SetProperty("R1", "title", "changed"); err != nil {
		t.Fatal(err)
	}
	waitFor(`event: set`)
	time.Sleep(300 * time.Millisecond)
	cancel()
	<-done

	body := rec.body()
	for _, k := range []string{"file:R1/title", "file:R1/n", "file:R2/title", "file:R2/n"} {
		if !strings.Contains(body, `"key":"`+k+`"`) {
			t.Errorf("snapshot is missing %s", k)
		}
	}
	events := strings.Split(strings.TrimSpace(body), "\n\n")
	if len(events) != 5 {
		t.Fatalf("want 4 snapshot events + 1 live event, got %d:\n%s", len(events), body)
	}
	for i, e := range events[:3] {
		if strings.Contains(e, "id: ") {
			t.Errorf("snapshot event %d carries an id: %q", i, e)
		}
	}
	if !strings.HasPrefix(events[3], "id: ") || !strings.HasPrefix(events[4], "id: ") {
		t.Fatalf("the last snapshot event and the live event must carry ids:\n%s", body)
	}
	if !strings.Contains(events[4], `"key":"file:R1/title"`) {
		t.Fatalf("live tail did not follow the snapshot: %q", events[4])
	}
}