package link

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

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

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

// An answer too large for one message is recorded as paged, and a call's record says so: `calls` no
// longer reads "answered" for an answer nobody received (novox/hq issue 314).
func TestAPagedAnswerIsSaidInCalls(t *testing.T) {
	l, a := NewCallLog(), newAnswers(t)
	big := strings.Repeat("x", 5000)
	l.serveCallWithin("mesh-controller", "conditions", nil, "_INBOX.operator.ABCDEFGHIJKLMNOPQRSTUV",
		func(context.Context, json.RawMessage) (any, error) { return big, nil }, a.respond, 2048, nil)
	got := a.only()
	said, _ := got["error"].(string)
	paged, _ := got["paged"].(map[string]any)
	if !strings.Contains(said, "more than the bus carries") || paged == nil || paged["parts"].(float64) < 3 {
		t.Fatalf("answered %v", got)
	}
	recent, _ := l.Recent()
	if len(recent) != 1 || recent[0].Paged == "" || strings.Contains(string(recent[0].Answer), "in full") {
		t.Fatalf("kept %+v", recent[0])
	}
}

// An answer the bus refuses anyway is said to its caller and to `calls`, never only to the journal.
func TestAnAnswerTheBusRefusesIsSaid(t *testing.T) {
	l := NewCallLog()
	var sent [][]byte
	respond := func(body []byte) error {
		if len(body) > 1000 {
			return nats.ErrMaxPayload
		}
		sent = append(sent, body)
		return nil
	}
	l.serveCallWithin("mesh-controller", "status", nil, "_INBOX.x.1",
		func(context.Context, json.RawMessage) (any, error) { return strings.Repeat("y", 4000), nil }, respond, 0, nil)
	if len(sent) != 1 || !strings.Contains(string(sent[0]), "would not carry it") {
		t.Fatalf("the caller was told %q", sent)
	}
	recent, _ := l.Recent()
	if recent[0].Refused == "" {
		t.Fatalf("calls does not say the answer was not sent: %+v", recent[0])
	}
}

// A part goes only to the caller its answer was paged to, on the verb that answered it.
func TestAPartGoesOnlyToItsCaller(t *testing.T) {
	conn, err := nats.Connect(testbus.URL(t))
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()
	l := NewCallLog()
	c := l.begin("mesh-controller", "status", nil, "_INBOX.operator.ABCDEFGHIJKLMNOPQRSTUV")
	l.page(c, []byte(strings.Repeat("z", 5000)), 2048)
	sub, err := conn.Subscribe("pages.test", func(m *nats.Msg) { l.servePage("mesh-controller", "status", m, nil) })
	if err != nil {
		t.Fatal(err)
	}
	defer sub.Unsubscribe()
	_, err = askPart(context.Background(), conn, "pages.test", Paged{Call: c.ID, Parts: 3}, 0)
	if err == nil || !strings.Contains(err.Error(), "another caller") {
		t.Fatalf("a part was handed to a caller it was not paged to: %v", err)
	}
	_, err = askPart(context.Background(), conn, "pages.test", Paged{Call: "call-0-0", Parts: 3}, 0)
	if err == nil || !strings.Contains(err.Error(), "not held here") {
		t.Fatalf("a part of nothing held: %v", err)
	}
}

// A part that cannot be had fails the whole answer, naming it — never a shorter answer.
func TestAMissingPartFailsTheWhole(t *testing.T) {
	conn, err := nats.Connect(testbus.URL(t))
	if err != nil {
		t.Fatal(err)
	}
	defer conn.Close()
	sub, err := conn.Subscribe("pages.none", func(m *nats.Msg) { _ = m.Respond([]byte(`{"error":"gone"}`)) })
	if err != nil {
		t.Fatal(err)
	}
	defer sub.Unsubscribe()
	first, _ := json.Marshal(map[string]any{"error": "too large", "paged": Paged{Call: "call-1-1", Bytes: 10, Parts: 2}})
	_, err = Whole(context.Background(), conn, "pages.none", first)
	if err == nil || !strings.Contains(err.Error(), "part 0") || !strings.Contains(err.Error(), "gone") {
		t.Fatalf("a missing part read as %v", err)
	}
	if plain, err := Whole(context.Background(), conn, "pages.none", []byte(`{"result":1}`)); err != nil ||
		string(plain) != `{"result":1}` {
		t.Fatalf("an answer that fits was changed: %s %v", plain, err)
	}
}