package conditions

import (
	"context"
	"os"
	"testing"
	"time"

	"github.com/nats-io/nats.go/jetstream"

	"github.com/novox/mesh-controller/internal/broker"
)

// The condition store against a real server: compare-and-set, an unreadable store refused, and the
// history read back by time are claims about what the bus does.

func busStoreForTest(t *testing.T) (*broker.JetStream, Backend, History) {
	t.Helper()
	url := os.Getenv("MESH_TEST_NATS")
	if url == "" {
		t.Skip("MESH_TEST_NATS unset")
	}
	js, err := broker.Dial(url)
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(js.Close)
	api, err := jetstream.New(js.Conn())
	if err != nil {
		t.Fatal(err)
	}
	_ = api.DeleteKeyValue(t.Context(), broker.ConditionsBucket)
	_ = api.DeleteKeyValue(t.Context(), broker.ConditionHistoryBucket)
	if err := js.EnsureControllerBuckets(); err != nil {
		t.Fatal(err)
	}
	store, history, err := OnTheBus(t.Context(), js.Conn())
	if err != nil {
		t.Fatal(err)
	}
	return js, store, history
}

// **A condition outlives the controller that raised it**, and two writers on the bus cannot lose each
// other's word: a stale revision is refused as moved.
func TestNatsTheStoreKeepsConditionsByCompareAndSet(t *testing.T) {
	_, store, history := busStoreForTest(t)
	ctx := t.Context()
	told := &Told{}
	k := NewKeeper(ctx, Options{Store: store, History: history, Teller: told})
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	k.Close(context.Background())

	again := NewKeeper(ctx, Options{Store: store, History: history})
	defer again.Close(context.Background())
	open, err := again.Open(ctx)
	if err != nil {
		t.Fatal(err)
	}
	if len(open) != 1 || open[0].Observations != 2 {
		t.Fatalf("a new keeper read %+v", open)
	}
	e, _, err := store.Get(ctx, "machine.ace.silent")
	if err != nil {
		t.Fatal(err)
	}
	if err := store.Update(ctx, "machine.ace.silent", []byte(`{}`), e.Revision-1); err != ErrMoved {
		t.Fatalf("a write at a stale revision answered %v", err)
	}
	if err := store.Create(ctx, "machine.ace.silent", []byte(`{}`)); err != ErrMoved {
		t.Fatalf("creating an open condition answered %v", err)
	}
	if err := store.Delete(ctx, "machine.ace.silent", e.Revision-1); err != ErrMoved {
		t.Fatalf("a delete at a stale revision answered %v", err)
	}
	if cleared, err := again.Clear(ctx, "machine.ace.silent", "heard"); err != nil || !cleared {
		t.Fatalf("cleared %v: %v", cleared, err)
	}
	// Raised again at once: the store takes a key whose last word was a delete.
	if _, err := again.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	got, _, _ := again.Get(ctx, "machine.ace.silent")
	if got.Count != 2 {
		t.Fatalf("raised again after its clearing as %+v", got)
	}
}

// **The history is read back from a moment, oldest first**, through the stream under its bucket.
func TestNatsTheHistoryIsReadByTime(t *testing.T) {
	_, store, history := busStoreForTest(t)
	ctx := t.Context()
	k := NewKeeper(ctx, Options{Store: store, History: history})
	if _, err := k.Observe(ctx, silent("ace")); err != nil {
		t.Fatal(err)
	}
	if _, err := k.Clear(ctx, "machine.ace.silent", "heard"); err != nil {
		t.Fatal(err)
	}
	k.Close(context.Background())
	all, err := history.Since(ctx, time.Now().Add(-time.Hour))
	if err != nil {
		t.Fatal(err)
	}
	if len(all) != 2 || all[0].Change != ChangeRaised || all[1].Change != ChangeCleared {
		t.Fatalf("history %+v", all)
	}
	none, err := history.Since(ctx, time.Now().Add(time.Hour))
	if err != nil || len(none) != 0 {
		t.Fatalf("history from the future: %+v %v", none, err)
	}
}