package delivery

import (
	"context"
	"log/slog"
	"net"
	"net/http"
	"net/netip"
	"net/url"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"go.uber.org/fx"
	"gorm.io/gorm"
	"sneak.berlin/go/webhooker/internal/archive"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/metrics"
)

// Exported constants for test access.
const (
	ExportDeliveryChannelSize     = deliveryChannelSize
	ExportRetryChannelSize        = retryChannelSize
	ExportDefaultFailureThreshold = defaultFailureThreshold
	ExportDefaultCooldown         = defaultCooldown

	// ExportMaxBodyLog is the cap the engine applies to a
	// recorded response body. The event log's handling of a cut
	// response is written against this number, so a test has to
	// be able to name it.
	ExportMaxBodyLog = maxBodyLog

	// ExportPendingSweepMinAge is how long a delivery must sit at
	// pending before the sweep treats it as stranded. A test has to
	// name it to age a row past the bound.
	ExportPendingSweepMinAge = pendingSweepMinAge
)

// NewTestGuard builds an SSRF Guard from an explicit egress
// allowlist, without going through config. Passing no prefixes
// yields the default guard, which blocks every private/reserved
// range.
func NewTestGuard(allowed ...netip.Prefix) *Guard {
	return &Guard{allowed: allowed}
}

// ExportCheckIP exposes the guard's single decision point, so a
// test can assert the policy both the validator and the dialer
// inherit without needing a live destination.
func (g *Guard) ExportCheckIP(ip net.IP) error {
	return g.checkIP(ip)
}

// ExportAlwaysBlockedNetworks exposes alwaysBlockedNetworks.
func ExportAlwaysBlockedNetworks() []*net.IPNet {
	return alwaysBlockedNetworks
}

// ExportBlockedNetworks exposes blockedNetworks.
func ExportBlockedNetworks() []*net.IPNet {
	return blockedNetworks
}

// ExportBlockedPublicNetworks exposes blockedPublicNetworks.
func ExportBlockedPublicNetworks() []*net.IPNet {
	return blockedPublicNetworks
}

// ExportIsForwardableHeader exposes isForwardableHeader.
func ExportIsForwardableHeader(name string) bool {
	return isForwardableHeader(name)
}

// ExportApplyRequestHeaders exposes applyRequestHeaders, so a test
// can inspect the header set an outbound delivery actually carries
// and the origin-scoped names it reports for the redirect policy.
func ExportApplyRequestHeaders(
	req *http.Request,
	event *database.Event,
	cfg *HTTPTargetConfig,
	userAgent string,
) []string {
	return applyRequestHeaders(req, event, cfg, userAgent)
}

// ExportTruncate exposes truncate for testing.
func ExportTruncate(s string, maxLen int) string {
	return truncate(s, maxLen)
}

// ExportDeliverHTTP delivers via the http target for testing.
func (e *Engine) ExportDeliverHTTP(
	ctx context.Context,
	webhookDB *gorm.DB,
	d *database.Delivery,
	task *Task,
) {
	e.httpTarget.Deliver(ctx, webhookDB, d, task, e)
}

// ExportDeliverHTTPWithScheduler delivers via the http target, handing
// any retry to sched instead of the engine, so a test can see the
// delay each retry is given.
func (e *Engine) ExportDeliverHTTPWithScheduler(
	ctx context.Context,
	webhookDB *gorm.DB,
	d *database.Delivery,
	task *Task,
	sched Scheduler,
) {
	e.httpTarget.Deliver(ctx, webhookDB, d, task, sched)
}

// ExportDeliverDatabase delivers via the database target.
func (e *Engine) ExportDeliverDatabase(
	webhookDB *gorm.DB, d *database.Delivery,
) {
	e.targets[database.TargetTypeDatabase].Deliver(
		context.Background(), webhookDB, d, &Task{}, e,
	)
}

// ExportDeliverLog delivers via the log target for testing.
func (e *Engine) ExportDeliverLog(
	webhookDB *gorm.DB, d *database.Delivery,
) {
	e.targets[database.TargetTypeLog].Deliver(
		context.Background(), webhookDB, d, &Task{}, e,
	)
}

// ExportDeliverSlack delivers via the slack target for
// testing.
func (e *Engine) ExportDeliverSlack(
	ctx context.Context,
	webhookDB *gorm.DB,
	d *database.Delivery,
) {
	task := &Task{
		DeliveryID:  d.ID,
		TargetID:    d.TargetID,
		MaxAttempts: d.Target.MaxAttempts,
		AttemptNum:  1,
	}

	e.targets[database.TargetTypeSlack].Deliver(
		ctx, webhookDB, d, task, e,
	)
}

// ExportUpdateDeliveryStatus exposes updateDeliveryStatus. It passes no
// target type, so no metric moves.
func (e *Engine) ExportUpdateDeliveryStatus(
	webhookDB *gorm.DB,
	d *database.Delivery,
	status database.DeliveryStatus,
) error {
	return e.updateDeliveryStatus(webhookDB, d, "", status)
}

// ExportProcessNewTask exposes processNewTask.
func (e *Engine) ExportProcessNewTask(
	ctx context.Context, task *Task,
) {
	e.processNewTask(ctx, task)
}

// ExportProcessRetryTask exposes processRetryTask.
func (e *Engine) ExportProcessRetryTask(
	ctx context.Context, task *Task,
) {
	e.processRetryTask(ctx, task)
}

// ExportEventForTask exposes the event reconstruction the delivery
// paths run: buildEventFromTask followed by hydrateEvent.
func (e *Engine) ExportEventForTask(
	webhookDB *gorm.DB, task *Task,
) (database.Event, error) {
	return e.hydrateEvent(
		webhookDB, buildEventFromTask(task), task,
	)
}

// ExportProcessDelivery exposes processDelivery.
func (e *Engine) ExportProcessDelivery(
	ctx context.Context,
	webhookDB *gorm.DB,
	d *database.Delivery,
	task *Task,
) {
	e.processDelivery(ctx, webhookDB, d, task)
}

// ExportGetCircuitBreaker exposes the http target's
// getCircuitBreaker.
func (e *Engine) ExportGetCircuitBreaker(
	targetID string,
) *CircuitBreaker {
	return e.httpTarget.getCircuitBreaker(targetID)
}

// ExportSetCircuitBreaker makes cb the http target's circuit breaker
// for targetID, so a test can use one with a short cooldown.
func (e *Engine) ExportSetCircuitBreaker(
	targetID string, cb *CircuitBreaker,
) {
	e.httpTarget.circuitBreakers.Store(targetID, cb)
}

// ExportSetSlackCircuitBreaker is ExportSetCircuitBreaker for the
// slack target.
func (e *Engine) ExportSetSlackCircuitBreaker(
	targetID string, cb *CircuitBreaker,
) {
	e.slackTarget.circuitBreakers.Store(targetID, cb)
}

// ExportParseHTTPConfig exposes parseHTTPConfig.
func (e *Engine) ExportParseHTTPConfig(
	configJSON string,
) (*HTTPTargetConfig, error) {
	return parseHTTPConfig(configJSON)
}

// ExportParseSlackConfig exposes parseSlackConfig.
func (e *Engine) ExportParseSlackConfig(
	configJSON string,
) (*SlackTargetConfig, error) {
	return parseSlackConfig(configJSON)
}

// ExportDoHTTPRequest exposes the http target's
// doHTTPRequest.
func (e *Engine) ExportDoHTTPRequest(
	ctx context.Context,
	cfg *HTTPTargetConfig,
	event *database.Event,
) (int, string, int64, error) {
	return e.httpTarget.doHTTPRequest(ctx, cfg, event)
}

// ExportClientForRequest exposes the http target's
// clientForRequest.
func (e *Engine) ExportClientForRequest(
	cfg *HTTPTargetConfig,
	originScoped []string,
) *http.Client {
	return e.httpTarget.clientForRequest(cfg, originScoped)
}

// ErrExportTooManyRedirects exposes the sentinel the redirect
// policy returns once a chain exceeds the hop cap. It carries the
// Err prefix rather than this file's usual Export one because it
// is a sentinel error.
var ErrExportTooManyRedirects = errTooManyRedirects

// ExportMaxDeliveryRedirects exposes the redirect hop cap.
const ExportMaxDeliveryRedirects = maxDeliveryRedirects

// ExportSameDeliveryOrigin exposes sameDeliveryOrigin.
func ExportSameDeliveryOrigin(origin, dest *url.URL) bool {
	return sameDeliveryOrigin(origin, dest)
}

// ExportClient returns the http target's shared HTTP client.
func (e *Engine) ExportClient() *http.Client {
	return e.httpTarget.client
}

// ExportScheduleRetry exposes ScheduleRetry.
func (e *Engine) ExportScheduleRetry(
	task Task, delay time.Duration,
) {
	e.ScheduleRetry(task, delay)
}

// ExportRecoverPendingDeliveries exposes
// recoverPendingDeliveries.
func (e *Engine) ExportRecoverPendingDeliveries(
	ctx context.Context,
	webhookDB *gorm.DB,
	webhookID string,
) {
	e.recoverPendingDeliveries(
		ctx, webhookDB, webhookID,
	)
}

// ExportRecoverWebhookDeliveries exposes
// recoverWebhookDeliveries.
func (e *Engine) ExportRecoverWebhookDeliveries(
	ctx context.Context, webhookID string,
) {
	e.recoverWebhookDeliveries(ctx, webhookID)
}

// ExportRecoverInFlight exposes recoverInFlight.
func (e *Engine) ExportRecoverInFlight(
	ctx context.Context,
) {
	e.recoverInFlight(ctx)
}

// ExportSweepWebhookRetries exposes sweepWebhookRetries.
func (e *Engine) ExportSweepWebhookRetries(
	ctx context.Context, webhookID string,
) {
	e.sweepWebhookRetries(ctx, webhookID)
}

// ExportStart exposes start for testing.
func (e *Engine) ExportStart() {
	e.start()
}

// ExportRegisterHooks registers the engine's real fx lifecycle
// hooks on a lifecycle supplied by a test, so a test can drive
// the exact OnStart/OnStop functions the application runs and
// hand OnStart the kind of context fx actually supplies.
func (e *Engine) ExportRegisterHooks(lc fx.Lifecycle) {
	e.registerHooks(lc)
}

// ExportStop exposes stop for testing.
func (e *Engine) ExportStop(ctx context.Context) error {
	return e.stop(ctx)
}

// ExportWedgeWorker adds a goroutine to the engine's WaitGroup
// that never observes cancellation and returns only when release
// is closed. It stands in for a worker stuck inside a delivery
// target that never returns, which is the only way stop can be
// made to outlast its context.
func (e *Engine) ExportWedgeWorker(release <-chan struct{}) {
	e.wg.Go(func() {
		<-release
	})
}

// ExportInflightHeld reports how many deliveries the engine currently
// owns, so a test can prove ownership is released rather than leaked.
func (e *Engine) ExportInflightHeld() int {
	return e.inflight.held()
}

// ExportRetainDelivery takes the first reference on a delivery, as the
// queueing side does. It lets a test put a delivery into the state a
// worker or a full channel would, without running the pool.
func (e *Engine) ExportRetainDelivery(deliveryID string) bool {
	return e.inflight.retainIdle(deliveryID)
}

// ExportRecoverRetryingDeliveries exposes recoverRetryingDeliveries.
func (e *Engine) ExportRecoverRetryingDeliveries(
	webhookDB *gorm.DB, webhookID string,
) {
	e.recoverRetryingDeliveries(webhookDB, webhookID)
}

// ExportFailMissingTarget exposes failMissingTarget, so a test can hand
// it a delivery as a batch read it earlier.
func (e *Engine) ExportFailMissingTarget(
	webhookDB *gorm.DB,
	webhookID string,
	d *database.Delivery,
) {
	e.failMissingTarget(webhookDB, webhookID, d)
}

// ExportSendRecoveredDeliveries exposes sendRecoveredDeliveries, so a
// test can hand it a target map that lacks a delivery's target.
func (e *Engine) ExportSendRecoveredDeliveries(
	ctx context.Context,
	webhookDB *gorm.DB,
	deliveries []database.Delivery,
	webhookID string,
	targetMap map[string]database.Target,
	settled map[string]struct{},
) {
	e.sendRecoveredDeliveries(
		ctx, webhookDB, deliveries, webhookID, targetMap, settled,
	)
}

// ExportDeliveryCh returns the delivery channel.
func (e *Engine) ExportDeliveryCh() chan Task {
	return e.deliveryCh
}

// ExportRetryCh returns the retry channel.
func (e *Engine) ExportRetryCh() chan Task {
	return e.retryCh
}

// NewTestEngine creates an Engine for unit tests without
// database dependencies. Its archive writers have no data
// directory, so a delivery to a database target fails.
func NewTestEngine(
	log *slog.Logger,
	client *http.Client,
	workers int,
) *Engine {
	e := &Engine{
		log:        log,
		deliveryCh: make(chan Task, deliveryChannelSize),
		retryCh:    make(chan Task, retryChannelSize),
		workers:    workers,
		mtr:        metrics.New(prometheus.NewRegistry()),
		archives:   archive.NewWriters(archive.WritersParams{Logger: log}),
	}
	e.initTargets(client)

	return e
}

// NewTestEngineSmallRetry creates an Engine with a tiny
// retry channel buffer for overflow testing.
func NewTestEngineSmallRetry(
	log *slog.Logger,
) *Engine {
	e := &Engine{
		log:      log,
		retryCh:  make(chan Task, 1),
		mtr:      metrics.New(prometheus.NewRegistry()),
		archives: archive.NewWriters(archive.WritersParams{Logger: log}),
	}
	e.initTargets(nil)

	return e
}

// NewTestEngineWithDB creates an Engine with a real
// database and dbManager for integration tests, and archive
// writers of its own over the same two.
func NewTestEngineWithDB(
	db *database.Database,
	dbMgr *database.WebhookDBManager,
	log *slog.Logger,
	client *http.Client,
	workers int,
) *Engine {
	e := &Engine{
		database:   db,
		dbManager:  dbMgr,
		log:        log,
		deliveryCh: make(chan Task, deliveryChannelSize),
		retryCh:    make(chan Task, retryChannelSize),
		workers:    workers,
		mtr:        metrics.New(prometheus.NewRegistry()),
		archives: archive.NewWriters(archive.WritersParams{
			Database:  db,
			DBManager: dbMgr,
			Logger:    log,
		}),
	}
	e.initTargets(client)

	return e
}

// ExportArchives returns the engine's archive writers.
func (e *Engine) ExportArchives() *archive.Writers {
	return e.archives
}

// ExportSetMetrics substitutes the engine's metric set, so a test can
// assert on collectors registered on a registry it holds.
func (e *Engine) ExportSetMetrics(mtr *metrics.Set) {
	e.mtr = mtr
}

// ExportSampleQueueDepths runs one queue depth sample synchronously.
func (e *Engine) ExportSampleQueueDepths(ctx context.Context) {
	e.sampleQueueDepths(ctx)
}

// NewTestCircuitBreaker creates a CircuitBreaker with
// custom settings for testing.
func NewTestCircuitBreaker(
	threshold int, cooldown time.Duration,
) *CircuitBreaker {
	return &CircuitBreaker{
		state:     CircuitClosed,
		threshold: threshold,
		cooldown:  cooldown,
	}
}