package scheduler

import (
	"context"
	"errors"
	"log/slog"
	"sync"
	"sync/atomic"
	"time"
)

// RenewalServicer defines the interface for renewal operations used by the scheduler.
type RenewalServicer interface {
	CheckExpiringCertificates(ctx context.Context) error
	ExpireShortLivedCertificates(ctx context.Context) error
}

// JobServicer defines the interface for job processing used by the scheduler.
//
// RetryFailedJobs was added to close coverage gap I-001: JobService.RetryFailedJobs
// existed and was unit-tested but had no runtime caller prior to this loop being
// wired. The scheduler now drives it on an independent tick so failed jobs whose
// attempt counter is below MaxAttempts are periodically reset to Pending for the
// job processor to pick up again. maxRetries is advisory (per-job gating uses
// each job's own Attempts/MaxAttempts fields).
type JobServicer interface {
	ProcessPendingJobs(ctx context.Context) error
	RetryFailedJobs(ctx context.Context, maxRetries int) error
}

// AgentServicer defines the interface for agent health checks used by the scheduler.
type AgentServicer interface {
	MarkStaleAgentsOffline(ctx context.Context, interval time.Duration) error
}

// NotificationServicer defines the interface for notification processing used by the scheduler.
//
// RetryFailedNotifications was added to close coverage gap I-005: the retry
// sweep transitions eligible Failed notifications to Pending on an independent
// tick, using exponential backoff with a 1h cap and a 5-attempt DLQ budget.
// Mirrors the I-001 job retry loop topology.
type NotificationServicer interface {
	ProcessPendingNotifications(ctx context.Context) error
	RetryFailedNotifications(ctx context.Context) error
}

// NetworkScanServicer defines the interface for network scanning used by the scheduler.
type NetworkScanServicer interface {
	ScanAllTargets(ctx context.Context) error
}

// DigestServicer defines the interface for digest email processing used by the scheduler.
type DigestServicer interface {
	ProcessDigest(ctx context.Context) error
}

// HealthCheckServicer defines the interface for endpoint TLS health monitoring used by the scheduler.
type HealthCheckServicer interface {
	RunHealthChecks(ctx context.Context) error
}

// CloudDiscoveryServicer defines the interface for cloud secret manager discovery used by the scheduler.
type CloudDiscoveryServicer interface {
	DiscoverAll(ctx context.Context) (int, []error)
}

// JobReaperService defines the interface for job timeout reaping used by the scheduler.
type JobReaperService interface {
	ReapTimedOutJobs(ctx context.Context, csrTTL, approvalTTL time.Duration) error
	// Bundle C / Audit M-016 (CWE-754): closes the gap left by ReapTimedOutJobs
	// (which only handles AwaitingCSR / AwaitingApproval). Jobs in Running
	// status whose owning agent has been silent for longer than agentTTL get
	// transitioned to Failed with reason "agent_offline" so I-001's retry
	// loop can re-queue them on a healthy agent.
	ReapJobsWithOfflineAgents(ctx context.Context, agentTTL time.Duration) error
}

// Scheduler manages background jobs and periodic tasks for the certificate control plane.
// It runs multiple concurrent loops for renewal checks, job processing, agent health checks,
// and notification processing.
type Scheduler struct {
	renewalService        RenewalServicer
	jobService            JobServicer
	agentService          AgentServicer
	notificationService   NotificationServicer
	networkScanService    NetworkScanServicer
	digestService         DigestServicer
	healthCheckService    HealthCheckServicer
	cloudDiscoveryService CloudDiscoveryServicer
	jobReaper             JobReaperService
	logger                *slog.Logger

	// Configurable tick intervals
	renewalCheckInterval          time.Duration
	jobProcessorInterval          time.Duration
	jobRetryInterval              time.Duration
	agentHealthCheckInterval      time.Duration
	notificationProcessInterval   time.Duration
	notificationRetryInterval     time.Duration
	shortLivedExpiryCheckInterval time.Duration
	networkScanInterval           time.Duration
	digestInterval                time.Duration
	healthCheckInterval           time.Duration
	cloudDiscoveryInterval        time.Duration
	jobTimeoutInterval            time.Duration
	// agentOfflineJobTTL: per-tick threshold for reaping Running jobs whose
	// owning agent has been silent. Bundle C / Audit M-016. Defaults below.
	agentOfflineJobTTL time.Duration
	awaitingCSRTimeout            time.Duration
	awaitingApprovalTimeout       time.Duration

	// Idempotency guards: prevent duplicate execution of slow jobs
	renewalCheckRunning          atomic.Bool
	jobProcessorRunning          atomic.Bool
	jobRetryRunning              atomic.Bool
	agentHealthCheckRunning      atomic.Bool
	notificationProcessRunning   atomic.Bool
	notificationRetryRunning     atomic.Bool
	shortLivedExpiryCheckRunning atomic.Bool
	networkScanRunning           atomic.Bool
	digestRunning                atomic.Bool
	healthCheckRunning           atomic.Bool
	cloudDiscoveryRunning        atomic.Bool
	jobTimeoutRunning            atomic.Bool

	// Graceful shutdown: wait for in-flight work to complete
	wg sync.WaitGroup
}

// NewScheduler creates a new scheduler with configurable intervals.
func NewScheduler(
	renewalService RenewalServicer,
	jobService JobServicer,
	agentService AgentServicer,
	notificationService NotificationServicer,
	networkScanService NetworkScanServicer,
	logger *slog.Logger,
) *Scheduler {
	return &Scheduler{
		renewalService:      renewalService,
		jobService:          jobService,
		agentService:        agentService,
		notificationService: notificationService,
		networkScanService:  networkScanService,
		logger:              logger,

		// Default intervals
		renewalCheckInterval:          1 * time.Hour,
		jobProcessorInterval:          30 * time.Second,
		jobRetryInterval:              5 * time.Minute,
		agentHealthCheckInterval:      2 * time.Minute,
		notificationProcessInterval:   1 * time.Minute,
		notificationRetryInterval:     2 * time.Minute,
		shortLivedExpiryCheckInterval: 30 * time.Second,
		networkScanInterval:           6 * time.Hour,
		digestInterval:                24 * time.Hour,
		healthCheckInterval:           60 * time.Second,
		cloudDiscoveryInterval:        6 * time.Hour,
		jobTimeoutInterval:            10 * time.Minute,
		// 5 minutes is 5×agentHealthCheckInterval default of 1m; an agent
		// must miss multiple heartbeats before its in-flight jobs are reaped.
		agentOfflineJobTTL: 5 * time.Minute,
	}
}

// SetDigestService sets the digest service for the 7th scheduler loop.
// Called after construction since digest is optional.
func (s *Scheduler) SetDigestService(ds DigestServicer) {
	s.digestService = ds
}

// SetDigestInterval configures the interval for digest email processing.
func (s *Scheduler) SetDigestInterval(d time.Duration) {
	s.digestInterval = d
}

// SetRenewalCheckInterval configures the interval for renewal checks.
func (s *Scheduler) SetRenewalCheckInterval(d time.Duration) {
	s.renewalCheckInterval = d
}

// SetJobProcessorInterval configures the interval for job processing.
func (s *Scheduler) SetJobProcessorInterval(d time.Duration) {
	s.jobProcessorInterval = d
}

// SetJobRetryInterval configures the interval for the failed-job retry loop
// (coverage gap I-001). Defaults to 5 minutes; honors
// CERTCTL_SCHEDULER_RETRY_INTERVAL when wired from config.
func (s *Scheduler) SetJobRetryInterval(d time.Duration) {
	s.jobRetryInterval = d
}

// SetAgentHealthCheckInterval configures the interval for agent health checks.
func (s *Scheduler) SetAgentHealthCheckInterval(d time.Duration) {
	s.agentHealthCheckInterval = d
}

// SetNotificationProcessInterval configures the interval for notification processing.
func (s *Scheduler) SetNotificationProcessInterval(d time.Duration) {
	s.notificationProcessInterval = d
}

// SetNotificationRetryInterval configures the interval for the failed-notification
// retry sweep (coverage gap I-005). Defaults to 2 minutes; honors
// CERTCTL_NOTIFICATION_RETRY_INTERVAL when wired from config.
func (s *Scheduler) SetNotificationRetryInterval(d time.Duration) {
	s.notificationRetryInterval = d
}

// SetNetworkScanInterval configures the interval for network scanning.
func (s *Scheduler) SetNetworkScanInterval(d time.Duration) {
	s.networkScanInterval = d
}

// SetShortLivedExpiryCheckInterval configures the interval for short-lived certificate expiry checks.
func (s *Scheduler) SetShortLivedExpiryCheckInterval(d time.Duration) {
	s.shortLivedExpiryCheckInterval = d
}

// SetHealthCheckService sets the health check service for the 8th scheduler loop.
// Called after construction since health monitoring is optional.
func (s *Scheduler) SetHealthCheckService(hcs HealthCheckServicer) {
	s.healthCheckService = hcs
}

// SetHealthCheckInterval configures the interval for endpoint TLS health checks.
func (s *Scheduler) SetHealthCheckInterval(d time.Duration) {
	s.healthCheckInterval = d
}

// SetCloudDiscoveryService sets the cloud discovery service for the 9th scheduler loop.
// Called after construction since cloud discovery is optional.
func (s *Scheduler) SetCloudDiscoveryService(cds CloudDiscoveryServicer) {
	s.cloudDiscoveryService = cds
}

// SetCloudDiscoveryInterval configures the interval for cloud secret manager discovery.
func (s *Scheduler) SetCloudDiscoveryInterval(d time.Duration) {
	s.cloudDiscoveryInterval = d
}

// SetJobReaperService sets the job reaper service (I-003).
func (s *Scheduler) SetJobReaperService(jr JobReaperService) {
	s.jobReaper = jr
}

// SetAgentOfflineJobTTL sets the threshold past which a Running job whose
// owning agent has gone silent is reaped to Failed. Bundle C / Audit M-016.
// Zero or negative values are ignored (the default of 5 minutes is kept).
func (s *Scheduler) SetAgentOfflineJobTTL(d time.Duration) {
	if d <= 0 {
		return
	}
	s.agentOfflineJobTTL = d
}

// SetJobTimeoutInterval sets the job timeout reaper tick interval (I-003).
func (s *Scheduler) SetJobTimeoutInterval(d time.Duration) {
	s.jobTimeoutInterval = d
}

// SetAwaitingCSRTimeout sets the AwaitingCSR TTL (I-003).
func (s *Scheduler) SetAwaitingCSRTimeout(d time.Duration) {
	s.awaitingCSRTimeout = d
}

// SetAwaitingApprovalTimeout sets the AwaitingApproval TTL (I-003).
func (s *Scheduler) SetAwaitingApprovalTimeout(d time.Duration) {
	s.awaitingApprovalTimeout = d
}

// Start initiates all background scheduler loops. It returns a channel that signals
// when the scheduler has started all loops. The scheduler runs until the context is cancelled.
func (s *Scheduler) Start(ctx context.Context) <-chan struct{} {
	startedChan := make(chan struct{})

	go func() {
		s.logger.Info("scheduler starting")

		// Track all loop goroutines in the WaitGroup so WaitForCompletion
		// blocks until they've fully exited (prevents test races).
		// Base count is 8: renewal, job processor, job retry (I-001),
		// job timeout (I-003), agent health, notification, notification retry
		// (I-005), short-lived expiry. Optional loops (network scan, digest,
		// health check, cloud discovery) add to this.
		loopCount := 8
		if s.networkScanService != nil {
			loopCount++
		}
		if s.digestService != nil {
			loopCount++
		}
		if s.healthCheckService != nil {
			loopCount++
		}
		if s.cloudDiscoveryService != nil {
			loopCount++
		}
		s.wg.Add(loopCount)

		go func() { defer s.wg.Done(); s.renewalCheckLoop(ctx) }()
		go func() { defer s.wg.Done(); s.jobProcessorLoop(ctx) }()
		go func() { defer s.wg.Done(); s.jobRetryLoop(ctx) }()
		go func() { defer s.wg.Done(); s.jobTimeoutLoop(ctx) }()
		go func() { defer s.wg.Done(); s.agentHealthCheckLoop(ctx) }()
		go func() { defer s.wg.Done(); s.notificationProcessLoop(ctx) }()
		go func() { defer s.wg.Done(); s.notificationRetryLoop(ctx) }()
		go func() { defer s.wg.Done(); s.shortLivedExpiryCheckLoop(ctx) }()
		if s.networkScanService != nil {
			go func() { defer s.wg.Done(); s.networkScanLoop(ctx) }()
		}
		if s.digestService != nil {
			go func() { defer s.wg.Done(); s.digestLoop(ctx) }()
		}
		if s.healthCheckService != nil {
			go func() { defer s.wg.Done(); s.healthCheckLoop(ctx) }()
		}
		if s.cloudDiscoveryService != nil {
			go func() { defer s.wg.Done(); s.cloudDiscoveryLoop(ctx) }()
		}

		// Signal that all loops are launched
		close(startedChan)

		// Wait for context cancellation
		<-ctx.Done()
		s.logger.Info("scheduler shutting down", "reason", ctx.Err())
	}()

	return startedChan
}

// renewalCheckLoop runs every renewalCheckInterval and checks for expiring certificates.
// If an error occurs, it logs the error but continues running.
// Uses atomic.Bool to prevent duplicate execution if the previous check is still running.
func (s *Scheduler) renewalCheckLoop(ctx context.Context) {
	ticker := time.NewTicker(s.renewalCheckInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.renewalCheckRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.renewalCheckRunning.Store(false)
		s.runRenewalCheck(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.renewalCheckRunning.CompareAndSwap(false, true) {
				s.logger.Warn("renewal check still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.renewalCheckRunning.Store(false)
				s.runRenewalCheck(ctx)
			}()
		}
	}
}

// runRenewalCheck executes a single renewal check with error recovery.
func (s *Scheduler) runRenewalCheck(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 5*time.Minute)
	defer cancel()
	if err := s.renewalService.CheckExpiringCertificates(opCtx); err != nil {
		s.logger.Error("renewal check failed",
			"error", err,
			"interval", s.renewalCheckInterval.String())
	} else {
		s.logger.Debug("renewal check completed")
	}
}

// jobProcessorLoop runs every jobProcessorInterval and processes pending jobs.
// It picks up pending jobs, executes them, and handles the results.
// If an error occurs, it logs the error but continues running.
// Uses atomic.Bool to prevent duplicate execution if the previous job is still running.
func (s *Scheduler) jobProcessorLoop(ctx context.Context) {
	ticker := time.NewTicker(s.jobProcessorInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.jobProcessorRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.jobProcessorRunning.Store(false)
		s.runJobProcessor(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.jobProcessorRunning.CompareAndSwap(false, true) {
				s.logger.Warn("job processor still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.jobProcessorRunning.Store(false)
				s.runJobProcessor(ctx)
			}()
		}
	}
}

// runJobProcessor executes a single job processing cycle with error recovery.
func (s *Scheduler) runJobProcessor(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	if err := s.jobService.ProcessPendingJobs(opCtx); err != nil {
		s.logger.Error("job processor failed",
			"error", err,
			"interval", s.jobProcessorInterval.String())
	} else {
		s.logger.Debug("job processor completed")
	}
}

// jobRetryLoop runs every jobRetryInterval and transitions eligible Failed jobs
// back to Pending so the job processor can pick them up again. Closes coverage
// gap I-001 — JobService.RetryFailedJobs had no runtime caller prior to this
// loop being wired. Runs immediately on start, then every interval.
// Uses atomic.Bool to prevent duplicate execution if the previous retry sweep
// is still running.
func (s *Scheduler) jobRetryLoop(ctx context.Context) {
	ticker := time.NewTicker(s.jobRetryInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.jobRetryRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.jobRetryRunning.Store(false)
		s.runJobRetry(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.jobRetryRunning.CompareAndSwap(false, true) {
				s.logger.Warn("job retry still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.jobRetryRunning.Store(false)
				s.runJobRetry(ctx)
			}()
		}
	}
}

// runJobRetry executes a single failed-job retry cycle with error recovery.
// Uses the same 2-minute per-tick timeout as runJobProcessor; RetryFailedJobs
// issues one SELECT and one UPDATE per eligible job (cheap), so this headroom
// covers very large failure backlogs without starving the loop.
func (s *Scheduler) runJobRetry(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	// maxRetries is advisory at the service layer (per-job gating uses each
	// job's own Attempts/MaxAttempts). Passing 3 matches the conventional
	// default seen across the codebase's job creation paths.
	if err := s.jobService.RetryFailedJobs(opCtx, 3); err != nil {
		s.logger.Error("job retry failed",
			"error", err,
			"interval", s.jobRetryInterval.String())
	} else {
		s.logger.Debug("job retry completed")
	}
}

// jobTimeoutLoop runs every jobTimeoutInterval and transitions jobs stuck in
// AwaitingCSR or AwaitingApproval to Failed if they exceed their TTL. I-001's
// retry loop then auto-promotes eligible Failed jobs back to Pending. Closes
// coverage gap I-003. Uses atomic.Bool to prevent duplicate execution.
func (s *Scheduler) jobTimeoutLoop(ctx context.Context) {
	ticker := time.NewTicker(s.jobTimeoutInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.jobTimeoutRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.jobTimeoutRunning.Store(false)
		s.runJobTimeout(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.jobTimeoutRunning.CompareAndSwap(false, true) {
				s.logger.Warn("job timeout reaper still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.jobTimeoutRunning.Store(false)
				s.runJobTimeout(ctx)
			}()
		}
	}
}

// runJobTimeout executes a single job timeout reaping cycle with error recovery.
// When no JobReaperService has been wired (e.g. in tests that don't exercise
// I-003) the call is a safe no-op, preserving the always-on loop topology
// described in I-003 without forcing every consumer to wire a reaper.
//
// Bundle C / Audit M-016: the reaping cycle now has TWO arms:
//
//  1. ReapTimedOutJobs handles AwaitingCSR / AwaitingApproval timeouts (I-003).
//  2. ReapJobsWithOfflineAgents handles Running jobs whose owning agent has
//     gone silent (M-016). Reuses the same agentHealthCheckTimeout as the
//     mark-stale-agents-offline path for consistency: if the agent is judged
//     offline by AgentService.MarkStaleAgentsOffline, its in-flight jobs
//     should be reaped on the same cadence.
func (s *Scheduler) runJobTimeout(ctx context.Context) {
	if s.jobReaper == nil {
		return
	}
	opCtx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	if err := s.jobReaper.ReapTimedOutJobs(opCtx, s.awaitingCSRTimeout, s.awaitingApprovalTimeout); err != nil {
		s.logger.Error("job timeout reaper failed",
			"error", err,
			"interval", s.jobTimeoutInterval.String())
	} else {
		s.logger.Debug("job timeout reaper completed")
	}
	// Second arm: offline-agent reaper. Uses agentOfflineTimeout (defaults to
	// 5 minutes — same value the agent-health-check path uses to flip an
	// agent to Offline). A sensible default of 5×agentHealthCheckInterval
	// catches agents that miss multiple consecutive heartbeats while leaving
	// a single missed beat as a transient blip that does NOT reap.
	offlineCtx, offlineCancel := context.WithTimeout(ctx, 2*time.Minute)
	defer offlineCancel()
	if err := s.jobReaper.ReapJobsWithOfflineAgents(offlineCtx, s.agentOfflineJobTTL); err != nil {
		s.logger.Error("offline-agent job reaper failed",
			"error", err,
			"agent_offline_ttl", s.agentOfflineJobTTL.String())
	} else {
		s.logger.Debug("offline-agent job reaper completed")
	}
}

// agentHealthCheckLoop runs every agentHealthCheckInterval and marks stale agents as offline.
// An agent is considered stale if it hasn't sent a heartbeat within the health check interval.
// If an error occurs, it logs the error but continues running.
// Uses atomic.Bool to prevent duplicate execution if the previous check is still running.
func (s *Scheduler) agentHealthCheckLoop(ctx context.Context) {
	ticker := time.NewTicker(s.agentHealthCheckInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.agentHealthCheckRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.agentHealthCheckRunning.Store(false)
		s.runAgentHealthCheck(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.agentHealthCheckRunning.CompareAndSwap(false, true) {
				s.logger.Warn("agent health check still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.agentHealthCheckRunning.Store(false)
				s.runAgentHealthCheck(ctx)
			}()
		}
	}
}

// runAgentHealthCheck executes a single agent health check with error recovery.
func (s *Scheduler) runAgentHealthCheck(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
	defer cancel()
	if err := s.agentService.MarkStaleAgentsOffline(opCtx, s.agentHealthCheckInterval); err != nil {
		s.logger.Error("agent health check failed",
			"error", err,
			"interval", s.agentHealthCheckInterval.String())
	} else {
		s.logger.Debug("agent health check completed")
	}
}

// notificationProcessLoop runs every notificationProcessInterval and processes pending notifications.
// If an error occurs, it logs the error but continues running.
// Uses atomic.Bool to prevent duplicate execution if the previous process is still running.
func (s *Scheduler) notificationProcessLoop(ctx context.Context) {
	ticker := time.NewTicker(s.notificationProcessInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.notificationProcessRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.notificationProcessRunning.Store(false)
		s.runNotificationProcess(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.notificationProcessRunning.CompareAndSwap(false, true) {
				s.logger.Warn("notification processor still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.notificationProcessRunning.Store(false)
				s.runNotificationProcess(ctx)
			}()
		}
	}
}

// runNotificationProcess executes a single notification processing cycle with error recovery.
func (s *Scheduler) runNotificationProcess(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
	defer cancel()
	if err := s.notificationService.ProcessPendingNotifications(opCtx); err != nil {
		s.logger.Error("notification processor failed",
			"error", err,
			"interval", s.notificationProcessInterval.String())
	} else {
		s.logger.Debug("notification processor completed")
	}
}

// notificationRetryLoop runs every notificationRetryInterval and transitions
// eligible Failed notifications back to Pending so the notification processor
// can pick them up again. Closes coverage gap I-005 — NotificationService.
// RetryFailedNotifications had no runtime caller prior to this loop being
// wired. Runs immediately on start, then every interval.
// Uses atomic.Bool to prevent duplicate execution if the previous retry sweep
// is still running. Mirrors the I-001 jobRetryLoop topology byte-for-byte.
func (s *Scheduler) notificationRetryLoop(ctx context.Context) {
	ticker := time.NewTicker(s.notificationRetryInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.notificationRetryRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.notificationRetryRunning.Store(false)
		s.runNotificationRetry(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.notificationRetryRunning.CompareAndSwap(false, true) {
				s.logger.Warn("notification retry still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.notificationRetryRunning.Store(false)
				s.runNotificationRetry(ctx)
			}()
		}
	}
}

// runNotificationRetry executes a single failed-notification retry cycle with
// error recovery. Uses a 2-minute per-tick timeout matching runJobRetry;
// RetryFailedNotifications issues one SELECT and one UPDATE per eligible row
// (cheap), so this headroom covers very large failure backlogs without
// starving the loop. The service layer swallows per-row send errors (mirrors
// ProcessPendingNotifications) and only returns the List error from the
// initial ListRetryEligible call.
func (s *Scheduler) runNotificationRetry(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	if err := s.notificationService.RetryFailedNotifications(opCtx); err != nil {
		s.logger.Error("notification retry failed",
			"error", err,
			"interval", s.notificationRetryInterval.String())
	} else {
		s.logger.Debug("notification retry completed")
	}
}

// shortLivedExpiryCheckLoop runs every shortLivedExpiryCheckInterval and marks expired
// short-lived certificates. For certs with TTL < 1 hour, expiry IS revocation —
// no CRL/OCSP needed.
// Uses atomic.Bool to prevent duplicate execution if the previous check is still running.
func (s *Scheduler) shortLivedExpiryCheckLoop(ctx context.Context) {
	ticker := time.NewTicker(s.shortLivedExpiryCheckInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.shortLivedExpiryCheckRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.shortLivedExpiryCheckRunning.Store(false)
		s.runShortLivedExpiryCheck(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.shortLivedExpiryCheckRunning.CompareAndSwap(false, true) {
				s.logger.Warn("short-lived expiry check still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.shortLivedExpiryCheckRunning.Store(false)
				s.runShortLivedExpiryCheck(ctx)
			}()
		}
	}
}

// runShortLivedExpiryCheck executes a single short-lived expiry check with error recovery.
func (s *Scheduler) runShortLivedExpiryCheck(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()
	if err := s.renewalService.ExpireShortLivedCertificates(opCtx); err != nil {
		s.logger.Error("short-lived expiry check failed",
			"error", err,
			"interval", s.shortLivedExpiryCheckInterval.String())
	} else {
		s.logger.Debug("short-lived expiry check completed")
	}
}

// networkScanLoop runs every networkScanInterval and performs active TLS scanning
// of configured network targets.
// Uses atomic.Bool to prevent duplicate execution if the previous scan is still running.
func (s *Scheduler) networkScanLoop(ctx context.Context) {
	ticker := time.NewTicker(s.networkScanInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.networkScanRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.networkScanRunning.Store(false)
		s.runNetworkScan(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.networkScanRunning.CompareAndSwap(false, true) {
				s.logger.Warn("network scan still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.networkScanRunning.Store(false)
				s.runNetworkScan(ctx)
			}()
		}
	}
}

// runNetworkScan executes a single network scan cycle with error recovery.
func (s *Scheduler) runNetworkScan(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 30*time.Minute)
	defer cancel()
	if err := s.networkScanService.ScanAllTargets(opCtx); err != nil {
		s.logger.Error("network scan failed",
			"error", err,
			"interval", s.networkScanInterval.String())
	} else {
		s.logger.Debug("network scan completed")
	}
}

// digestLoop runs every digestInterval and generates/sends certificate digest emails.
// Uses atomic.Bool to prevent duplicate execution if the previous digest is still running.
func (s *Scheduler) digestLoop(ctx context.Context) {
	ticker := time.NewTicker(s.digestInterval)
	defer ticker.Stop()

	// Do NOT run immediately on start for digest — wait for the first tick.
	// Digests are infrequent (24h default) and shouldn't fire on every restart.

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.digestRunning.CompareAndSwap(false, true) {
				s.logger.Warn("digest processor still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.digestRunning.Store(false)
				s.runDigest(ctx)
			}()
		}
	}
}

// runDigest executes a single digest processing cycle with error recovery.
func (s *Scheduler) runDigest(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 5*time.Minute)
	defer cancel()
	if err := s.digestService.ProcessDigest(opCtx); err != nil {
		s.logger.Error("digest processor failed",
			"error", err,
			"interval", s.digestInterval.String())
	} else {
		s.logger.Debug("digest processor completed")
	}
}

// healthCheckLoop runs every healthCheckInterval and performs endpoint TLS health checks.
// Do NOT run immediately on start — health checks are frequent (60s default) and may be
// resource-intensive. Wait for the first tick.
// Uses atomic.Bool to prevent duplicate execution if the previous check is still running.
func (s *Scheduler) healthCheckLoop(ctx context.Context) {
	ticker := time.NewTicker(s.healthCheckInterval)
	defer ticker.Stop()

	// Do NOT run immediately on start for health checks — wait for the first tick.
	// Health checks are frequent and shouldn't fire on every restart.

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.healthCheckRunning.CompareAndSwap(false, true) {
				s.logger.Debug("health check still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.healthCheckRunning.Store(false)
				s.runHealthCheck(ctx)
			}()
		}
	}
}

// runHealthCheck executes a single health check cycle with error recovery.
func (s *Scheduler) runHealthCheck(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 5*time.Minute)
	defer cancel()
	if err := s.healthCheckService.RunHealthChecks(opCtx); err != nil {
		s.logger.Error("health check run failed",
			"error", err,
			"interval", s.healthCheckInterval.String())
	} else {
		s.logger.Debug("health check completed")
	}
}

// cloudDiscoveryLoop runs every cloudDiscoveryInterval and discovers certificates from cloud secret managers.
// Runs immediately on start, then on each tick. Same idempotency pattern as networkScanLoop.
// Uses atomic.Bool to prevent duplicate execution if the previous scan is still running.
func (s *Scheduler) cloudDiscoveryLoop(ctx context.Context) {
	ticker := time.NewTicker(s.cloudDiscoveryInterval)
	defer ticker.Stop()

	// Run immediately on start (with idempotency guard)
	s.cloudDiscoveryRunning.Store(true)
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		defer s.cloudDiscoveryRunning.Store(false)
		s.runCloudDiscovery(ctx)
	}()

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			if !s.cloudDiscoveryRunning.CompareAndSwap(false, true) {
				s.logger.Warn("cloud discovery still running, skipping tick")
				continue
			}
			s.wg.Add(1)
			go func() {
				defer s.wg.Done()
				defer s.cloudDiscoveryRunning.Store(false)
				s.runCloudDiscovery(ctx)
			}()
		}
	}
}

// runCloudDiscovery executes a single cloud discovery cycle with error recovery.
func (s *Scheduler) runCloudDiscovery(ctx context.Context) {
	opCtx, cancel := context.WithTimeout(ctx, 30*time.Minute)
	defer cancel()
	total, errs := s.cloudDiscoveryService.DiscoverAll(opCtx)
	if len(errs) > 0 {
		s.logger.Error("cloud discovery completed with errors",
			"certificates_found", total,
			"errors", len(errs),
			"interval", s.cloudDiscoveryInterval.String())
		for _, err := range errs {
			if !errors.Is(err, context.Canceled) {
				s.logger.Error("cloud discovery error", "error", err)
			}
		}
	} else {
		s.logger.Debug("cloud discovery completed",
			"certificates_found", total)
	}
}

// WaitForCompletion waits for all in-flight scheduler work to complete.
// It respects the provided timeout and returns an error if work is still in progress after timeout.
// Call this after the scheduler context has been cancelled to ensure graceful shutdown.
func (s *Scheduler) WaitForCompletion(timeout time.Duration) error {
	done := make(chan struct{})
	go func() {
		s.wg.Wait()
		close(done)
	}()

	select {
	case <-done:
		s.logger.Info("all scheduler work completed")
		return nil
	case <-time.After(timeout):
		s.logger.Warn("scheduler work did not complete within timeout", "timeout", timeout.String())
		return ErrSchedulerShutdownTimeout
	}
}

// ErrSchedulerShutdownTimeout is returned when scheduler graceful shutdown times out.
var ErrSchedulerShutdownTimeout = errors.New("scheduler graceful shutdown timeout")