package delivery_test

import (
	"context"
	"encoding/json"
	"io"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"

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

// tsEventCreatedAt is the receipt time seeded on the events these
// tests deliver. It is far enough from both the zero time and from
// now that neither can be mistaken for it.
func tsEventCreatedAt() time.Time {
	return time.Date(
		2026, time.March, 4, 5, 6, 7, 0, time.UTC,
	)
}

// tsZeroStamp is what a Slack message renders when the event handed
// to FormatSlackMessage carries no CreatedAt.
const tsZeroStamp = "*Timestamp:* `0001-01-01T00:00:00Z`"

// tsEventBody is the body seeded on every event in this file. It is
// small enough that a Task can inline it.
const tsEventBody = `{"hello":"world"}`

// tsUndeliverableHook stands in for a Slack incoming webhook on the
// tests that never send: the config parser requires a URL, but no
// request is made.
const tsUndeliverableHook = "https://hooks.slack.com/services/T/B/x"

// tsSink is a stand-in Slack incoming webhook that records the raw
// body posted to it.
type tsSink struct {
	*httptest.Server

	bodies chan []byte
}

func newTSSink(t *testing.T) *tsSink {
	t.Helper()

	s := &tsSink{bodies: make(chan []byte, 8)}

	s.Server = httptest.NewServer(http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			body, _ := io.ReadAll(r.Body)

			select {
			case s.bodies <- body:
			default:
			}

			w.WriteHeader(http.StatusOK)
		},
	))

	t.Cleanup(s.Close)

	return s
}

// text returns the Slack message text from the single payload the
// sink received.
func (s *tsSink) text(t *testing.T) string {
	t.Helper()

	select {
	case raw := <-s.bodies:
		t.Logf("raw slack payload: %s", raw)

		var payload struct {
			Text string `json:"text"`
		}

		require.NoError(t, json.Unmarshal(raw, &payload))

		return payload.Text
	case <-time.After(5 * time.Second):
		t.Fatal("slack sink received no payload")

		return ""
	}
}

func tsSlackConfig(t *testing.T, url string) string {
	t.Helper()

	data, err := json.Marshal(
		delivery.SlackTargetConfig{WebhookURL: url},
	)
	require.NoError(t, err)

	return string(data)
}

// tsSeedEvent writes an event whose CreatedAt is tsEventCreatedAt
// rather than the write time, so an assertion on the rendered
// timestamp cannot pass by accident against "roughly now".
func tsSeedEvent(
	t *testing.T, db *gorm.DB, webhookID string,
) database.Event {
	t.Helper()

	event := database.Event{
		WebhookID:    webhookID,
		EntrypointID: uuid.New().String(),
		Method:       http.MethodPost,
		Headers:      `{}`,
		Body:         tsEventBody,
		ContentType:  "application/json",
	}
	event.ID = uuid.New().String()
	event.CreatedAt = tsEventCreatedAt()
	event.UpdatedAt = tsEventCreatedAt()

	require.NoError(t, db.Create(&event).Error)

	var stored database.Event

	require.NoError(t,
		db.First(&stored, "id = ?", event.ID).Error,
	)
	require.Equal(t,
		tsEventCreatedAt().UTC(), stored.CreatedAt.UTC(),
		"seeded created_at did not round-trip",
	)

	return event
}

// tsSeedTarget writes the slack target row into the main database.
// The retry path confirms the target still exists before sending.
func tsSeedTarget(
	t *testing.T, mainDB *gorm.DB, webhookID, config string,
) database.Target {
	t.Helper()

	target := database.Target{
		WebhookID: webhookID,
		Name:      "slack-sink",
		Type:      database.TargetTypeSlack,
		Config:    config,
		Active:    true,
	}

	require.NoError(t, mainDB.Create(&target).Error)

	return target
}

func tsTask(
	d database.Delivery,
	event database.Event,
	webhookID string,
	target database.Target,
	attemptNum int,
	body *string,
) delivery.Task {
	return delivery.Task{
		DeliveryID:   d.ID,
		EventID:      event.ID,
		WebhookID:    webhookID,
		EntrypointID: event.EntrypointID,
		TargetID:     target.ID,
		TargetName:   target.Name,
		TargetType:   database.TargetTypeSlack,
		TargetConfig: target.Config,
		MaxRetries:   0,
		Method:       event.Method,
		Headers:      event.Headers,
		ContentType:  event.ContentType,
		Body:         body,
		AttemptNum:   attemptNum,
	}
}

func tsAssertRealTimestamp(t *testing.T, text string) {
	t.Helper()

	assert.NotContains(t, text, tsZeroStamp,
		"slack message carries the zero timestamp",
	)
	assert.Contains(t, text,
		"*Timestamp:* `"+
			tsEventCreatedAt().UTC().Format(time.RFC3339)+"`",
		"slack message does not carry the event's receipt time",
	)
}

// tsCase is one end-to-end delivery of a seeded event to a slack
// sink, over whichever engine path `process` names.
type tsCase struct {
	// status is the delivery row's status before the engine runs.
	// The retry path refuses a delivery that is not retrying.
	status database.DeliveryStatus

	// inlineBody mirrors a Task built for a body under
	// MaxInlineBodySize. When false the engine reads the body back
	// from the stored row.
	inlineBody bool

	attemptNum int

	process func(
		ctx context.Context, e *delivery.Engine, task *delivery.Task,
	)
}

// run delivers one event through the named path and returns the
// Slack message text the sink received.
func (c tsCase) run(t *testing.T) (iSetup, database.Delivery, string) {
	t.Helper()

	s := newISetup(t)
	sink := newTSSink(t)

	cfg := tsSlackConfig(t, sink.URL)
	target := tsSeedTarget(t, s.MainDB, s.WebhookID, cfg)
	event := tsSeedEvent(t, s.WebhookDB, s.WebhookID)

	d := iSeedDelivery(
		t, s.WebhookDB, event.ID, target.ID, c.status,
	)

	var body *string

	if c.inlineBody {
		bodyStr := event.Body
		body = &bodyStr
	}

	task := tsTask(
		d, event, s.WebhookID, target, c.attemptNum, body,
	)

	c.process(context.TODO(), s.Engine, &task)

	return s, d, sink.text(t)
}

// TestSlackFirstAttemptCarriesEventTimestamp covers the path an
// event takes on its first delivery: the task comes from the
// receiver and the engine reconstructs the event from it.
func TestSlackFirstAttemptCarriesEventTimestamp(t *testing.T) {
	t.Parallel()

	s, d, text := tsCase{
		status:     database.DeliveryStatusPending,
		inlineBody: true,
		attemptNum: 1,
		process: func(
			ctx context.Context,
			e *delivery.Engine,
			task *delivery.Task,
		) {
			e.ExportProcessNewTask(ctx, task)
		},
	}.run(t)

	tsAssertRealTimestamp(t, text)

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

// TestSlackFirstAttemptLargeBodyCarriesEventTimestamp covers the
// first-attempt path for an event whose body exceeded
// MaxInlineBodySize, so the task carries no body and the engine
// reads it back from the stored row.
func TestSlackFirstAttemptLargeBodyCarriesEventTimestamp(
	t *testing.T,
) {
	t.Parallel()

	_, _, text := tsCase{
		status:     database.DeliveryStatusPending,
		inlineBody: false,
		attemptNum: 1,
		process: func(
			ctx context.Context,
			e *delivery.Engine,
			task *delivery.Task,
		) {
			e.ExportProcessNewTask(ctx, task)
		},
	}.run(t)

	tsAssertRealTimestamp(t, text)
}

// TestSlackRetryCarriesEventTimestamp covers the retry path, which
// reconstructs the event from the same task the first attempt used.
func TestSlackRetryCarriesEventTimestamp(t *testing.T) {
	t.Parallel()

	s, d, text := tsCase{
		status:     database.DeliveryStatusRetrying,
		inlineBody: true,
		attemptNum: 2,
		process: func(
			ctx context.Context,
			e *delivery.Engine,
			task *delivery.Task,
		) {
			e.ExportProcessRetryTask(ctx, task)
		},
	}.run(t)

	tsAssertRealTimestamp(t, text)

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

// TestFormatSlackMessageOverTaskReconstructedEvent asserts on the
// formatted message directly, over the event the delivery paths
// reconstruct from a Task. It is the unit-level guard under the
// end-to-end tests: revert the CreatedAt population in hydrateEvent
// and this fails on the zero timestamp.
func TestFormatSlackMessageOverTaskReconstructedEvent(
	t *testing.T,
) {
	t.Parallel()

	s := newISetup(t)

	cfg := tsSlackConfig(t, tsUndeliverableHook)
	target := tsSeedTarget(t, s.MainDB, s.WebhookID, cfg)
	event := tsSeedEvent(t, s.WebhookDB, s.WebhookID)

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

	bodyStr := event.Body
	task := tsTask(d, event, s.WebhookID, target, 1, &bodyStr)

	rebuilt, err := s.Engine.ExportEventForTask(
		s.WebhookDB, &task,
	)
	require.NoError(t, err)
	assert.False(t, rebuilt.CreatedAt.IsZero(),
		"reconstructed event carries the zero time",
	)
	assert.Equal(t,
		tsEventCreatedAt().UTC(), rebuilt.CreatedAt.UTC(),
	)

	tsAssertRealTimestamp(
		t, delivery.FormatSlackMessage(&rebuilt),
	)
}

// TestFormatSlackMessageZeroTimestamp asserts the rendering choice
// directly, without going through the engine: a zero CreatedAt (the
// shape a reaped-row fallback produces) renders as "unknown" rather
// than the year-1 zero time, while a real CreatedAt still renders as
// RFC3339.
func TestFormatSlackMessageZeroTimestamp(t *testing.T) {
	t.Parallel()

	zeroEvent := database.Event{
		Method:      http.MethodPost,
		ContentType: testContentType,
		Body:        tsEventBody,
	}

	zeroText := delivery.FormatSlackMessage(&zeroEvent)

	assert.NotContains(t, zeroText, "0001-01-01",
		"slack message carries the zero-time year",
	)
	assert.Contains(t, zeroText, "*Timestamp:* `unknown`",
		"slack message does not mark an unset receipt time as unknown",
	)

	nonZeroEvent := zeroEvent
	nonZeroEvent.CreatedAt = tsEventCreatedAt()

	nonZeroText := delivery.FormatSlackMessage(&nonZeroEvent)

	assert.Contains(t, nonZeroText,
		"*Timestamp:* `"+
			tsEventCreatedAt().UTC().Format(time.RFC3339)+"`",
		"slack message does not render a real receipt time as RFC3339",
	)
}

// TestEventReconstructionSurvivesAReapedRow pins the fallback: an
// event row reaped by retention while its delivery still holds the
// body inline is still delivered, with the receipt time unset,
// rather than dropped.
func TestEventReconstructionSurvivesAReapedRow(t *testing.T) {
	t.Parallel()

	s := newISetup(t)

	cfg := tsSlackConfig(t, tsUndeliverableHook)
	target := tsSeedTarget(t, s.MainDB, s.WebhookID, cfg)
	event := tsSeedEvent(t, s.WebhookDB, s.WebhookID)

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

	bodyStr := event.Body
	task := tsTask(d, event, s.WebhookID, target, 1, &bodyStr)

	require.NoError(t, s.WebhookDB.Unscoped().Delete(
		&database.Event{}, "id = ?", event.ID,
	).Error)

	rebuilt, err := s.Engine.ExportEventForTask(
		s.WebhookDB, &task,
	)
	require.NoError(t, err)
	assert.Equal(t, bodyStr, rebuilt.Body)
	assert.True(t, rebuilt.CreatedAt.IsZero())

	// A task with no inlined body has nothing left to deliver, so
	// the same reaped row is an error there.
	noBody := task
	noBody.Body = nil

	_, err = s.Engine.ExportEventForTask(s.WebhookDB, &noBody)
	require.Error(t, err)
}