package link

import (
	"bytes"
	"context"
	"encoding/json"
	"log"
	"strings"
	"testing"
	"time"

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

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

// The calls bucket against a real server (novox/hq to-be 45 §6): whether a call's outcome is
// readable by id from a controller that did not serve it is a claim about what the bus keeps.

func callsBucket(t *testing.T) *BusCalls {
	t.Helper()
	js := aBus(t)
	api, err := jetstream.New(js.Conn())
	if err != nil {
		t.Fatal(err)
	}
	_ = api.DeleteKeyValue(t.Context(), broker.CallsBucket)
	if err := js.EnsureControllerBuckets(); err != nil {
		t.Fatal(err)
	}
	keeper, err := CallsOnTheBus(t.Context(), js.Conn())
	if err != nil {
		t.Fatal(err)
	}
	return keeper
}

// waitKept waits until the keeper holds a call in a state, the writes being queued.
func waitKept(t *testing.T, keeper CallKeeper, id, state string) Call {
	t.Helper()
	deadline := time.Now().Add(5 * time.Second)
	for {
		c, found, err := keeper.Kept(context.Background(), id)
		if err == nil && found && c.State == state {
			return c
		}
		if time.Now().After(deadline) {
			t.Fatalf("%s never kept as %q: %+v %v %v", id, state, c, found, err)
		}
		time.Sleep(20 * time.Millisecond)
	}
}

// **A controller restart keeps every call's outcome** (to-be 45 Phase 0): a call one controller
// answered is read whole by id from the next, and a call it left running is said abandoned rather
// than running for ever.
func TestNatsACallsOutcomeOutlivesItsController(t *testing.T) {
	keeper := callsBucket(t)
	first := NewCallLog()
	if err := first.Durably(t.Context(), keeper, "controller@one", nil); err != nil {
		t.Fatal(err)
	}
	a := newAnswers(t)
	first.serveCall("mesh-controller", "push", json.RawMessage(`{"node":"anchor","values":"secret"}`),
		"_INBOX.node-tools.g14.Pe3sGzAtv8jUBYQ6sKSvKz.1",
		func(context.Context, json.RawMessage) (any, error) { return "anchor told", nil }, a.respond, nil)
	recent, _ := first.Recent()
	finished := waitKept(t, keeper, recent[0].ID, CallAnswered)
	// A second call, still running when its controller stops.
	left := first.begin("mesh-controller", "plans", json.RawMessage(`{}`), "")
	waitKept(t, keeper, left.ID, CallRunning)

	var said bytes.Buffer
	second := NewCallLog()
	if err := second.Durably(t.Context(), keeper, "controller@two", log.New(&said, "", 0)); err != nil {
		t.Fatal(err)
	}
	c, found, err := second.Get(finished.ID)
	if err != nil || !found {
		t.Fatalf("the next controller cannot read %s: %v %v", finished.ID, found, err)
	}
	if !strings.Contains(string(c.Answer), "anchor told") || c.Caller != "node-tools.g14" || c.Holder != "controller@one" {
		t.Fatalf("kept %+v", c)
	}
	if strings.Contains(string(c.Args), "secret") {
		t.Fatalf("a setting was kept: %s", c.Args)
	}
	abandoned, _, _ := second.Get(left.ID)
	if abandoned.State != CallAbandoned || !strings.Contains(said.String(), left.ID) {
		t.Fatalf("a call left running reads %q, and was said: %q", abandoned.State, said.String())
	}
	listed, err := second.Recent()
	if err != nil || len(listed) != 2 {
		t.Fatalf("the next controller lists %d calls: %v", len(listed), err)
	}
	// Its own running calls are not its predecessor's: a controller starting again under the same
	// name leaves them alone.
	mine := second.begin("mesh-controller", "status", nil, "")
	waitKept(t, keeper, mine.ID, CallRunning)
	if err := second.Durably(t.Context(), keeper, "controller@two", nil); err != nil {
		t.Fatal(err)
	}
	if c, _, _ := keeper.Kept(t.Context(), mine.ID); c.State != CallRunning {
		t.Fatalf("a controller marked its own running call %q", c.State)
	}
}

// The bucket holds the last thousand calls or fourteen days: a call is two keys, so the stream under
// it holds twice as many messages, and asserting it again keeps the count.
func TestNatsTheCallsBucketIsBounded(t *testing.T) {
	callsBucket(t)
	js := aBus(t)
	if err := js.EnsureControllerBuckets(); err != nil {
		t.Fatal(err)
	}
	info, err := js.Context().StreamInfo("KV_" + broker.CallsBucket)
	if err != nil {
		t.Fatal(err)
	}
	if info.Config.MaxMsgs != 2*broker.KeptCallsDurably || info.Config.MaxAge != broker.CallsKeptFor {
		t.Fatalf("kept %d messages for %s", info.Config.MaxMsgs, info.Config.MaxAge)
	}
}

// An answer larger than the bound is cut and says so, and the record is still written.
func TestNatsAnAnswerLargerThanTheBoundIsCut(t *testing.T) {
	keeper := callsBucket(t)
	big, _ := json.Marshal(map[string]string{"result": strings.Repeat("x", broker.CallAnswerBytes+10)})
	c := Call{ID: "call-1-1", Seat: "mesh-controller", Verb: "plan", State: CallAnswered, Answer: big}
	if err := keeper.Keep(t.Context(), c); err != nil {
		t.Fatal(err)
	}
	got, found, err := keeper.Kept(t.Context(), "call-1-1")
	if err != nil || !found || !strings.Contains(string(got.Answer), "the first") {
		t.Fatalf("%v %v %.200s", found, err, got.Answer)
	}
}

// Who asked is read from the inbox the answer goes to.
func TestTheCallerIsTheInboxsPrincipal(t *testing.T) {
	for reply, want := range map[string]string{
		"_INBOX.node-tools.g14.Pe3sGzAtv8jUBYQ6sKSvKz.1": "node-tools.g14",
		"_INBOX.jochen.Pe3sGzAtv8jUBYQ6sKSvKz":           "jochen",
		"_INBOX.x.1":                                     "",
		"mesh.control.one":                               "",
		"":                                               "",
	} {
		if got := callerOf(reply); got != want {
			t.Errorf("%q: %q, want %q", reply, got, want)
		}
	}
}