package announce

import (
	"encoding/json"
	"strings"
	"testing"
	"time"

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

	"github.com/novox/mesh-tools/node-tools/internal/bus"
	mt "github.com/novox/mesh-tools/node-tools/internal/meshtest"
)

func connect(t *testing.T, module, node string) *bus.Conn {
	t.Helper()
	c, err := bus.Connect(bus.Credential{URL: mt.URL(t), Module: module, Node: node})
	if err != nil {
		t.Fatal(err)
	}
	c.Logf = func(string, ...any) {}
	t.Cleanup(c.Close)
	return c
}

// lagging answers PING at once and INFO after `lag` — or never, with a negative lag: a runtime whose
// one large answer is slow to cross the bus, as the laptop's was (2026-10-05).
func lagging(t *testing.T, conn *bus.Conn, s Service, lag time.Duration, endpoints []Endpoint) {
	t.Helper()
	ping, _ := json.Marshal(micro.Ping{ServiceIdentity: s.identity(), Type: micro.PingResponseType})
	stop, err := conn.Raw("$SRV.PING", func(string, []byte) []byte { return ping })
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(stop)
	stop, err = conn.Raw("$SRV.INFO", func(string, []byte) []byte {
		if lag < 0 {
			return nil
		}
		time.Sleep(lag)
		body, _ := json.Marshal(Info(s, endpoints))
		return body
	})
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(stop)
	conn.Flush()
}

// A runtime whose answer arrives after the window is waited for, because it said it was there; one
// that never says what it serves is named, not dropped. With the fixed 750 ms window the laptop's
// modules were said to run nowhere whenever its answer was late (2026-10-05).
func TestDiscoveryWaitsForEveryRuntimeThatSaidItIsThere(t *testing.T) {
	was := Patience
	Patience = 2500 * time.Millisecond
	t.Cleanup(func() { Patience = was })

	fast := connect(t, "node-tools", "desk")
	stopFast, err := Serve(fast, Service{Name: "node-tools", ID: "desk", Metadata: map[string]string{"node": "desk"}}, func() []Endpoint {
		return []Endpoint{{Kind: KindTool, Module: "alpha", Tool: "one", Node: "desk", Subject: "mesh.mod.alpha.tool.one.desk"}}
	})
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(stopFast)
	fast.Flush()
	slow := connect(t, "node-tools", "laptop")
	lagging(t, slow, Service{Name: "node-tools", ID: "laptop", Metadata: map[string]string{"node": "laptop"}}, Window+400*time.Millisecond,
		[]Endpoint{{Kind: KindTool, Module: "slack", Tool: "slack_check", Node: "laptop", Subject: "mesh.mod.slack.tool.slack_check.laptop"}})
	mute := connect(t, "node-tools", "sleeper")
	lagging(t, mute, Service{Name: "node-tools", ID: "sleeper", Metadata: map[string]string{"node": "sleeper"}}, -1, nil)

	asker := connect(t, "console", "desk")
	start := time.Now()
	d, err := Gather(asker)
	if err != nil {
		t.Fatal(err)
	}
	took := time.Since(start)

	heard := map[string]Heard{}
	for _, h := range d.Heard {
		heard[h.Info.ID] = h
	}
	if h, ok := heard["laptop"]; !ok {
		t.Fatalf("the slow runtime was not heard: %+v", d.Heard)
	} else if h.Took <= Window || h.Machine() != "laptop" || h.Bytes == 0 {
		t.Errorf("the slow runtime's answer: took %s (window %s), machine %q, %d bytes", h.Took, Window, h.Machine(), h.Bytes)
	}
	if _, ok := heard["desk"]; !ok {
		t.Errorf("the fast runtime was not heard: %+v", d.Heard)
	}
	if len(d.Silent) != 1 || d.Silent[0].ID != "sleeper" || d.Silent[0].Machine != "sleeper" {
		t.Errorf("the runtime that never said what it serves is not named: %+v", d.Silent)
	}
	if took < Patience || took > Patience+time.Second {
		t.Errorf("waited %s with a silent runtime; patience is %s", took, Patience)
	}
}

// With nobody slow, discovery takes the window and no longer.
func TestDiscoveryDoesNotWaitWhenEveryoneAnswered(t *testing.T) {
	fast := connect(t, "node-tools", "desk")
	stop, err := Serve(fast, Service{Name: "node-tools", ID: "desk"}, func() []Endpoint { return nil })
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(stop)
	fast.Flush()
	start := time.Now()
	d, err := Gather(connect(t, "console", "desk"))
	if err != nil {
		t.Fatal(err)
	}
	if took := time.Since(start); took > Window+500*time.Millisecond || len(d.Silent) != 0 || len(d.Heard) == 0 {
		t.Errorf("took %s, heard %d, silent %+v", took, len(d.Heard), d.Silent)
	}
}

// Too large even with first lines, descriptions are left out — and the answer says which, without
// touching the service's own metadata.
func TestAnAnswerTooLargeIsShortenedUntilItFits(t *testing.T) {
	long := strings.Repeat("A sentence that is long. ", 20)
	var endpoints []Endpoint
	for i := 0; i < 50; i++ {
		endpoints = append(endpoints, Endpoint{Kind: KindTool, Module: "m", Tool: "t" + strings.Repeat("x", i), Node: "laptop",
			Description: long, Subject: "mesh.mod.m.tool.t"})
	}
	own := map[string]string{"node": "laptop"}
	info := Info(Service{Name: "node-tools", ID: "laptop", Metadata: own}, endpoints)
	full, _ := json.Marshal(info)
	firstLines := 0
	for range endpoints {
		firstLines += len(firstLine(long))
	}
	limit := int64(len(full) - len(long)*len(endpoints) + firstLines/2) // first lines alone do not fit
	var said []string
	got := shorten(func(f string, a ...any) { said = append(said, f) }, info, full, limit)
	if int64(len(got)) > limit {
		t.Fatalf("still %d bytes, beyond %d", len(got), limit)
	}
	var back micro.Info
	if err := json.Unmarshal(got, &back); err != nil {
		t.Fatal(err)
	}
	if back.Metadata[Shortened] != "descriptions left out" || back.Metadata["node"] != "laptop" {
		t.Errorf("metadata: %v", back.Metadata)
	}
	if _, has := own[Shortened]; has {
		t.Error("the service's own metadata was changed")
	}
	if len(said) != 2 {
		t.Errorf("each step is said: %v", said)
	}
}