package link

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"log"
	"testing"
	"time"

	amqp "github.com/rabbitmq/amqp091-go"
)

type saidTo struct{ acked, nacked, requeued bool }

func (a *saidTo) Ack(uint64, bool) error { a.acked = true; return nil }
func (a *saidTo) Nack(_ uint64, _ bool, requeue bool) error {
	a.nacked, a.requeued = true, requeue
	return nil
}
func (a *saidTo) Reject(uint64, bool) error { return nil }

type heardWith struct{ err error }

func (h heardWith) Heard(context.Context, Report) error { return h.err }

func aReport(t *testing.T, to *saidTo) amqp.Delivery {
	t.Helper()
	body, err := json.Marshal(Report{Node: "anchor", Applied: []string{"store"}})
	if err != nil {
		t.Fatal(err)
	}
	return amqp.Delivery{Acknowledger: to, RoutingKey: KeyReport, Body: body}
}

// A report the store could not take right now goes back to the broker to be asked again; one the
// store answered no to is acknowledged, or it would come back for ever (novox/hq issue 082).
func TestAReportTheStoreCouldNotTakeIsKeptAndOneItRefusedIsNot(t *testing.T) {
	quiet := log.New(io.Discard, "", 0)

	notNow := &saidTo{}
	s := &Server{listener: heardWith{err: errors.Join(ErrTryAgain, errors.New("starting up"))}, log: quiet, again: 1}
	s.handleReport(context.Background(), aReport(t, notNow))
	if notNow.acked || !notNow.nacked || !notNow.requeued {
		t.Fatalf("a report the store could not take yet was not handed back to be asked again: %+v", notNow)
	}

	refused := &saidTo{}
	s = &Server{listener: heardWith{err: errors.New("a report named no node")}, log: quiet, again: 1}
	s.handleReport(context.Background(), aReport(t, refused))
	if !refused.acked || refused.nacked {
		t.Fatalf("a report the store answered no to was not acknowledged, so it would spin: %+v", refused)
	}

	recorded := &saidTo{}
	s = &Server{listener: heardWith{}, log: quiet}
	s.handleReport(context.Background(), aReport(t, recorded))
	if !recorded.acked || recorded.nacked {
		t.Fatalf("a recorded report was not acknowledged: %+v", recorded)
	}
}

// A store that has not come back within the bound is not restarting: the report is let go, loudly,
// rather than holding every enrolment and report behind it for ever (novox/hq issue 082, review).
func TestAReportIsLetGoOnceTheStoreHasBeenGoneTooLong(t *testing.T) {
	quiet := log.New(io.Discard, "", 0)
	s := &Server{listener: heardWith{err: errors.Join(ErrTryAgain, errors.New("connection refused"))},
		log: quiet, again: 1, giveUp: time.Millisecond}

	first := &saidTo{}
	s.handleReport(context.Background(), aReport(t, first))
	if !first.requeued {
		t.Fatalf("the first failure was not handed back: %+v", first)
	}
	time.Sleep(5 * time.Millisecond)
	later := &saidTo{}
	s.handleReport(context.Background(), aReport(t, later))
	if !later.acked || later.nacked {
		t.Fatalf("a report past the bound was not let go, so it would hold the queue for ever: %+v", later)
	}
	// Let go, and forgotten: the same report arriving fresh starts a new clock.
	again := &saidTo{}
	s.handleReport(context.Background(), aReport(t, again))
	if !again.requeued {
		t.Fatalf("a report let go was not forgotten, so its next arrival is given no chance: %+v", again)
	}
}

// Shutting down does not wait out the pause.
func TestAReportBeingTriedAgainDoesNotHoldUpShutdown(t *testing.T) {
	quiet := log.New(io.Discard, "", 0)
	s := &Server{listener: heardWith{err: errors.Join(ErrTryAgain, errors.New("starting up"))},
		log: quiet, again: time.Hour}
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	done := make(chan struct{})
	go func() { s.handleReport(ctx, aReport(t, &saidTo{})); close(done) }()
	select {
	case <-done:
	case <-time.After(5 * time.Second):
		t.Fatal("a cancelled context still waited out the pause")
	}
}