package api

import (
	"context"
	"fmt"
	"time"

	"github.com/ponzischeme89/memby/server/internal/scheduler"
	"github.com/ponzischeme89/memby/server/internal/store"
)

// RegisterHousekeeping declares the gateway's background jobs.
//
// This list is deliberately readable top to bottom: it is the answer to "what does the
// server do when nobody is watching", and before the scheduler existed that answer was
// spread across four `go someTicker(ctx, …)` calls in main with no shared vocabulary,
// no history and no way for an operator to run one by hand. Two of the jobs below —
// analytics retention and the idle-session sweep — were exactly those tickers.
//
// Each Run returns the sentence the console prints beside the run, and returns an *empty*
// one when nothing happened. That emptiness is what keeps the notification bell quiet:
// see scheduler.announce.
func (s *Server) RegisterHousekeeping(sched *scheduler.Scheduler) {
	if sched == nil {
		return
	}

	sched.Register(scheduler.Task{
		ID:    "login-retention",
		Name:  "Login history retention",
		Group: "Housekeeping",
		Description: fmt.Sprintf("Removes sign-in records older than %d days.",
			int(store.LoginRetention/(24*time.Hour))),
		Interval: 24 * time.Hour,
		Run: func(ctx context.Context) (string, error) {
			removed, err := s.store.PruneLoginEvents(ctx, store.LoginRetention)
			return countDetail(removed, "sign-in record"), err
		},
	})

	sched.Register(scheduler.Task{
		ID:    "notification-cleanup",
		Name:  "Notification cleanup",
		Group: "Housekeeping",
		Description: fmt.Sprintf("Removes administrative events older than %d days.",
			int(store.AdminEventRetention/(24*time.Hour))),
		Interval: 24 * time.Hour,
		Run: func(ctx context.Context) (string, error) {
			removed, err := s.store.PruneAdminEvents(ctx, store.AdminEventRetention)
			return countDetail(removed, "notification"), err
		},
	})

	sched.Register(scheduler.Task{
		ID:          "integration-cleanup",
		Name:        "Integration delivery cleanup",
		Group:       "Housekeeping",
		Description: "Keeps the most recent hundred delivery attempts for each integration.",
		Interval:    12 * time.Hour,
		Run: func(ctx context.Context) (string, error) {
			removed, err := s.store.PruneIntegrationDeliveries(ctx, 100)
			return countDetail(removed, "delivery record"), err
		},
	})

	sched.Register(scheduler.Task{
		ID:          "task-history-cleanup",
		Name:        "Task history cleanup",
		Group:       "Housekeeping",
		Description: "Removes this table's own old rows, so the scheduler cannot outgrow the database it reports from.",
		Interval:    24 * time.Hour,
		Run: func(ctx context.Context) (string, error) {
			removed, err := s.store.PruneTaskRuns(ctx, store.TaskRunRetention)
			return countDetail(removed, "task run"), err
		},
	})

	// Was pruneAnalytics in main. Retention is configuration rather than a constant here
	// because engagement telemetry is the one dataset an operator might genuinely want to
	// keep for a season or discard within a week.
	if s.cfg.AnalyticsRetention > 0 {
		sched.Register(scheduler.Task{
			ID:    "analytics-retention",
			Name:  "Analytics retention",
			Group: "Analytics",
			Description: fmt.Sprintf(
				"Removes row engagement and journey events older than %d days.",
				int(s.cfg.AnalyticsRetention/(24*time.Hour))),
			Interval: 24 * time.Hour,
			Run: func(ctx context.Context) (string, error) {
				removed, err := s.store.PruneRowEvents(ctx, s.cfg.AnalyticsRetention)
				return countDetail(removed, "analytics event"), err
			},
		})
	}

	// Was sweepIdleSessions in main. It matters more than it looks: a session row holds a
	// live Emby token, so a television that was factory-reset leaves working upstream
	// credentials in the database until this runs.
	sched.Register(scheduler.Task{
		ID:    "session-sweep",
		Name:  "Idle session sweep",
		Group: "Housekeeping",
		Description: fmt.Sprintf(
			"Retires gateway tokens unused for %d days, along with the Emby token each one holds.",
			int(s.cfg.SessionIdleExpiry/(24*time.Hour))),
		Interval: 6 * time.Hour,
		Run: func(ctx context.Context) (string, error) {
			removed, err := s.store.DeleteIdleSessions(ctx, s.cfg.SessionIdleExpiry)
			return countDetail(removed, "idle session"), err
		},
	})

	// Not a prune: Redis is configured with no persistence and an LRU eviction policy, so
	// nothing here has to delete anything. What it checks is that the cache is *reachable*
	// — a gateway whose Redis has gone away still serves every page, slowly, with no error
	// anybody sees, and this is the one thing that would say so.
	sched.Register(scheduler.Task{
		ID:          "cache-check",
		Name:        "Cache health check",
		Group:       "System",
		Description: "Confirms Redis is answering. Nothing is deleted: the cache evicts by itself.",
		Interval:    30 * time.Minute,
		Timeout:     30 * time.Second,
		Run: func(ctx context.Context) (string, error) {
			if s.cache == nil {
				return "", nil
			}
			if err := s.cache.Ping(ctx); err != nil {
				return "", fmt.Errorf("redis did not answer: %w", err)
			}
			// A successful check reports nothing, so a healthy cache is silent and only a
			// failure reaches the notification feed.
			return "", nil
		},
	})

	sched.Register(scheduler.Task{
		ID:          "database-check",
		Name:        "Database health check",
		Group:       "System",
		Description: "Confirms Postgres is answering.",
		Interval:    30 * time.Minute,
		Timeout:     30 * time.Second,
		Run: func(ctx context.Context) (string, error) {
			if err := s.store.Ping(ctx); err != nil {
				return "", fmt.Errorf("postgres did not answer: %w", err)
			}
			return "", nil
		},
	})
}

// countDetail is the one line a housekeeping run reports, and returns empty for zero.
//
// Empty is not a formatting nicety — it is what stops a job running every six hours
// announcing "0 removed" into the operator's notification bell every six hours, which is
// how a feed becomes something nobody reads.
func countDetail(count int64, noun string) string {
	if count <= 0 {
		return ""
	}
	if count == 1 {
		return "1 " + noun + " removed"
	}
	return fmt.Sprintf("%d %ss removed", count, noun)
}