package delivery_test

import (
	"context"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/google/uuid"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/delivery"
)

// These tests pin the rule that decides whether a delivery may be
// handed back to a worker: the engine re-dispatches only what it does
// not already own. Age alone is not that rule — a healthy delivery
// waiting in a 10000-deep channel is old and must not be re-sent. See
// https://git.eeqj.de/sneak/webhooker/issues/256.

// fSweepSetup seeds the main database with the webhook row the sweep
// enumerates, and returns the setup.
func fSweepSetup(
	t *testing.T, targetID, name string,
) iSetup {
	t.Helper()

	s := newISetup(t)

	iCreateTarget(t, s.MainDB, targetID,
		s.WebhookID, name,
		database.TargetTypeLog, "", 0,
	)

	require.NoError(t, s.MainDB.Create(&database.Webhook{
		BaseModel: database.BaseModel{ID: s.WebhookID},
		UserID:    uuid.New().String(),
		Name:      name,
	}).Error)

	return s
}

// fDrain collects every task the engine has queued.
//
// Every caller drives the dispatch paths synchronously and has already
// waited for them to return, so anything they queued is in the channel
// by now. The short grace covers nothing but scheduler jitter, and is
// kept small because one of these tests runs the drain forty times.
func fDrain(e *delivery.Engine) []delivery.Task {
	var out []delivery.Task

	for {
		select {
		case task := <-e.ExportDeliveryCh():
			out = append(out, task)
		case task := <-e.ExportRetryCh():
			out = append(out, task)
		case <-time.After(25 * time.Millisecond):
			return out
		}
	}
}

// TestArchiveHandleIsWAL closes the last gap in the durability
// evidence: the main and per-webhook tiers each assert their journal
// mode on a live handle, and the archive tier gets its settings from
// the same code path but nothing checked the running file.
func TestArchiveHandleIsWAL(t *testing.T) {
	t.Parallel()

	w := delivery.NewExportArchiveWriter(
		filepath.Join(t.TempDir(), "archive-wal.db"),
		archiveTestLogger(), 0,
	)

	require.NoError(t, w.Open(0))

	var mode string

	row := w.DB().Raw("pragma journal_mode").Row()
	require.NoError(t, row.Scan(&mode))
	assert.Equal(t, "wal", strings.ToLower(mode))

	var busy string

	row = w.DB().Raw("pragma busy_timeout").Row()
	require.NoError(t, row.Scan(&busy))
	assert.Equal(t, "10000", busy)
}

// TestSweepLeavesAQueuedDeliveryAlone is the case the age bound cannot
// see. The delivery is queued and untouched, so its row is arbitrarily
// old and still perfectly healthy; only ownership distinguishes it
// from a stranded one.
func TestSweepLeavesAQueuedDeliveryAlone(t *testing.T) {
	t.Parallel()

	targetID := uuid.New().String()
	s := fSweepSetup(t, targetID, "queued")

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"queued":true}`,
	)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusPending,
	)
	rAgePending(t, s.WebhookDB, d.ID)

	// Queued exactly as the receiver queues it, and never dequeued:
	// no workers are running in this engine.
	s.Engine.Notify([]delivery.Task{{
		DeliveryID: d.ID,
		EventID:    event.ID,
		WebhookID:  s.WebhookID,
		TargetID:   targetID,
	}})

	require.Equal(t, 1, s.Engine.ExportInflightHeld())

	s.Engine.ExportSweepWebhookRetries(
		context.Background(), s.WebhookID,
	)

	tasks := fDrain(s.Engine)
	assert.Len(
		t, tasks, 1,
		"the sweep must not queue a delivery that is "+
			"already waiting for a worker",
	)
}

// TestRecoveryAndSweepDoNotDoubleDispatch drives the two entry points
// the engine starts concurrently against one aged pending row. Before
// ownership they both dispatched it.
func TestRecoveryAndSweepDoNotDoubleDispatch(t *testing.T) {
	t.Parallel()

	targetID := uuid.New().String()
	s := fSweepSetup(t, targetID, "racing")

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"racing":true}`,
	)

	ctx := context.Background()

	for range 40 {
		d := iSeedDelivery(
			t, s.WebhookDB, event.ID, targetID,
			database.DeliveryStatusPending,
		)
		rAgePending(t, s.WebhookDB, d.ID)

		var wg sync.WaitGroup

		wg.Go(func() {
			s.Engine.ExportRecoverPendingDeliveries(
				ctx, s.WebhookDB, s.WebhookID,
			)
		})
		wg.Go(func() {
			s.Engine.ExportSweepWebhookRetries(
				ctx, s.WebhookID,
			)
		})
		wg.Wait()

		tasks := fDrain(s.Engine)
		require.Len(
			t, tasks, 1,
			"delivery %s dispatched %d times",
			d.ID, len(tasks),
		)

		// No worker runs in this engine, so the reference the winner
		// took is never released and earlier iterations' deliveries
		// stay owned — which is itself the property under test, since
		// both paths see them on every subsequent pass.
	}
}

// TestConcurrentClaimsOfOneDeliveryYieldOneOwner exercises the
// exclusion directly, rather than arguing it from a SQL predicate.
func TestConcurrentClaimsOfOneDeliveryYieldOneOwner(
	t *testing.T,
) {
	t.Parallel()

	eng := newISetup(t).Engine
	deliveryID := uuid.New().String()

	var (
		wg  sync.WaitGroup
		mu  sync.Mutex
		won int
	)

	for range 64 {
		wg.Go(func() {
			if eng.ExportRetainDelivery(deliveryID) {
				mu.Lock()
				won++
				mu.Unlock()
			}
		})
	}

	wg.Wait()

	assert.Equal(t, 1, won)
	assert.Equal(t, 1, eng.ExportInflightHeld())
}

// TestOwnershipIsReleasedAfterDelivery guards the other direction: a
// leaked reference hides a delivery from every sweep for the life of
// the process.
func TestOwnershipIsReleasedAfterDelivery(t *testing.T) {
	t.Parallel()

	s := newISetup(t)
	targetID := uuid.New().String()

	iCreateTarget(t, s.MainDB, targetID,
		s.WebhookID, "released",
		database.TargetTypeLog, "", 0,
	)

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"released":true}`,
	)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusPending,
	)

	s.Engine.ExportStart()

	defer func() {
		require.NoError(
			t, s.Engine.ExportStop(context.Background()),
		)
	}()

	body := `{"released":true}`

	s.Engine.Notify([]delivery.Task{{
		DeliveryID:   d.ID,
		EventID:      event.ID,
		WebhookID:    s.WebhookID,
		TargetID:     targetID,
		TargetName:   "released",
		TargetType:   database.TargetTypeLog,
		Body:         &body,
		EntrypointID: event.EntrypointID,
	}})

	iWaitForDelivered(t, s.WebhookDB, d.ID)

	assert.Eventually(
		t,
		func() bool {
			return s.Engine.ExportInflightHeld() == 0
		},
		2*time.Second, 20*time.Millisecond,
		"the delivery stayed owned after it was delivered",
	)
}

// TestRetryingRecoverySkipsASuccessfulResult is the retrying-side twin
// of the pending reconcile. A second attempt that reached the receiver
// and whose status write then failed sits at retrying holding a
// successful result, and re-sending it is the same duplicate.
func TestRetryingRecoverySkipsASuccessfulResult(t *testing.T) {
	t.Parallel()

	targetID := uuid.New().String()
	s := fSweepSetup(t, targetID, "retry-settled")

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"retry":true}`,
	)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusRetrying,
	)
	rSeedResult(t, s.WebhookDB, d.ID, 1, false)
	rSeedResult(t, s.WebhookDB, d.ID, 2, true)

	s.Engine.ExportRecoverRetryingDeliveries(
		s.WebhookDB, s.WebhookID,
	)

	assert.Empty(
		t, fDrain(s.Engine),
		"a retrying delivery holding a successful result "+
			"must not be sent again",
	)

	iAssertStatus(
		t, s.WebhookDB, d.ID,
		database.DeliveryStatusDelivered,
	)
}

// TestRetryingSweepSkipsASuccessfulResult is the same rule on the
// periodic sweep's retrying arm.
func TestRetryingSweepSkipsASuccessfulResult(t *testing.T) {
	t.Parallel()

	targetID := uuid.New().String()
	s := fSweepSetup(t, targetID, "retry-swept")

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"swept":true}`,
	)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusRetrying,
	)
	rSeedResult(t, s.WebhookDB, d.ID, 1, false)
	rSeedResult(t, s.WebhookDB, d.ID, 2, true)

	s.Engine.ExportSweepWebhookRetries(
		context.Background(), s.WebhookID,
	)

	assert.Empty(t, fDrain(s.Engine))

	iAssertStatus(
		t, s.WebhookDB, d.ID,
		database.DeliveryStatusDelivered,
	)

	var attempts int64

	require.NoError(t, s.WebhookDB.
		Model(&database.DeliveryResult{}).
		Where("delivery_id = ?", d.ID).
		Count(&attempts).Error)
	assert.Equal(
		t, int64(2), attempts,
		"settling must not invent an attempt",
	)
}

// TestScheduledRetryIsNotSweptDuringBackoff closes the window between
// a target scheduling a retry and the timer firing. The row says
// retrying and nothing is running, which is exactly what an orphaned
// retry looks like from the database.
func TestScheduledRetryIsNotSweptDuringBackoff(t *testing.T) {
	t.Parallel()

	targetID := uuid.New().String()
	s := fSweepSetup(t, targetID, "backoff")

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"backoff":true}`,
	)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusRetrying,
	)

	s.Engine.ExportScheduleRetry(delivery.Task{
		DeliveryID: d.ID,
		EventID:    event.ID,
		WebhookID:  s.WebhookID,
		TargetID:   targetID,
		AttemptNum: 2,
	}, time.Hour)

	require.Equal(t, 1, s.Engine.ExportInflightHeld())

	s.Engine.ExportSweepWebhookRetries(
		context.Background(), s.WebhookID,
	)

	assert.Empty(
		t, fDrain(s.Engine),
		"the sweep must not duplicate a retry that is "+
			"already scheduled",
	)
}

// TestRedispatchStampsTheRow pins the cadence control: a stranded
// delivery that has just been handed out is not selected again by the
// next tick a minute later.
func TestRedispatchStampsTheRow(t *testing.T) {
	t.Parallel()

	targetID := uuid.New().String()
	s := fSweepSetup(t, targetID, "stamped")

	event := iSeedEvent(
		t, s.WebhookDB, s.WebhookID, `{"stamped":true}`,
	)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, targetID,
		database.DeliveryStatusPending,
	)
	rAgePending(t, s.WebhookDB, d.ID)

	ctx := context.Background()

	s.Engine.ExportSweepWebhookRetries(ctx, s.WebhookID)
	require.Len(t, fDrain(s.Engine), 1)

	var row database.Delivery

	require.NoError(t, s.WebhookDB.
		First(&row, "id = ?", d.ID).Error)
	assert.WithinDuration(
		t, time.Now(), row.UpdatedAt, time.Minute,
		"a re-dispatched delivery must be stamped so the "+
			"next tick does not select it again",
	)
}