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}
	a := testSigner(t, 1)
	for i, cid := range []string{"bafyR1", "bafyR2"} {
		storeClaims(t, stor, signed(t, a, cid, "title", "T", 1), signed(t, a, cid, "n", string(rune('a'+i)), 1))
	}
	r1, r2 := stor.ResolveRoot("bafyR1"), stor.ResolveRoot("bafyR2")

	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"`)
	storeClaims(t, stor, signed(t, a, "bafyR1", "title", "changed", 2))
	waitFor(`event: set`)
	time.Sleep(300 * time.Millisecond)
	cancel()
	<-done

	body := rec.body()
	keys := []string{"file:" + r1 + "/title", "file:" + r1 + "/n", "file:" + r2 + "/title", "file:" + r2 + "/n",
		"file:" + r1 + "/cids/bafyR1", "file:" + r2 + "/cids/bafyR2"}
	for _, k := range keys {
		if !strings.Contains(body, `"key":"`+k+`"`) {
			t.Errorf("snapshot is missing %s", k)
		}
	}
	events := strings.Split(strings.TrimSpace(body), "\n\n")
	if len(events) != 7 {
		t.Fatalf("want 6 snapshot events + 1 live event, got %d:\n%s", len(events), body)
	}
	for i, e := range events[:5] {
		if strings.Contains(e, "id: ") {
			t.Errorf("snapshot event %d carries an id: %q", i, e)
		}
	}
	if !strings.HasPrefix(events[5], "id: ") || !strings.HasPrefix(events[6], "id: ") {
		t.Fatalf("the last snapshot event and the live event must carry ids:\n%s", body)
	}
	if !strings.Contains(events[6], `"key":"file:`+r1+`/title"`) {
		t.Fatalf("live tail did not follow the snapshot: %q", events[6])
	}
}

// A cursor older than the last cache rebuild gets `gap` (reason rebuild): the
// rebuild published no per-key events, so the consumer must re-snapshot.
func TestMetaEventsGapAfterRebuild(t *testing.T) {
	stor := newTestStorage(t)
	s := &Server{storage: stor}
	storeClaims(t, stor, signed(t, testSigner(t, 1), "bafyA", "title", "T", 1))
	if err := stor.Rebuild(); 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", "1000-0")
	rec := &syncRecorder{ResponseRecorder: httptest.NewRecorder()}
	done := make(chan struct{})
	go func() { s.handleEventsMeta(rec, req); close(done) }()
	deadline := time.Now().Add(5 * time.Second)
	for !strings.Contains(rec.body(), "event: gap") {
		if time.Now().After(deadline) {
			t.Fatalf("no gap after rebuild:\n%s", rec.body())
		}
		time.Sleep(20 * time.Millisecond)
	}
	cancel()
	<-done
	if !strings.Contains(rec.body(), `"reason":"rebuild"`) {
		t.Fatalf("gap reason: %s", rec.body())
	}
}