package notifier

import (
	"context"
	"fmt"
	"log"
	"time"

	"naviwatcher/internal/config"
	"naviwatcher/internal/database"
	"naviwatcher/internal/scanner"
)

// NotifyOnce queries for releases that have not yet been notified, builds a
// digest, sends it through the given Sender, and marks each release as sent.
// Releases already present in notifications_sent are excluded upstream by
// GetUnnotifiedReleases, so this is idempotent across runs.
//
// If there are no unnotified releases the digest reports "no new missing
// releases" and nothing is marked sent (there is nothing to mark).
//
// uiBaseURL is the externally-reachable base URL of the Web UI, appended to the
// digest so operators can jump to the dashboard.
func NotifyOnce(ctx context.Context, db *database.DB, sender Sender, cfg config.TelegramConfig, uiBaseURL string) (int, error) {
	if sender == nil {
		return 0, fmt.Errorf("notifier: sender must not be nil")
	}

	unnotified, err := database.GetUnnotifiedReleases(db)
	if err != nil {
		return 0, fmt.Errorf("notifier: query unnotified releases: %w", err)
	}

	missing := make([]scanner.MissingRelease, 0, len(unnotified))
	for _, r := range unnotified {
		missing = append(missing, scanner.MissingRelease{
			RGID:        r.RGID,
			ArtistID:    r.ArtistID,
			Title:       r.Title,
			Type:        r.Type,
			ReleaseDate: r.ReleaseDate,
		})
	}

	message := FormatDigest(missing, uiBaseURL)
	if err := sender.Send(ctx, message); err != nil {
		return 0, fmt.Errorf("notifier: send digest: %w", err)
	}

	for _, r := range unnotified {
		if err := database.MarkNotificationSent(db, r.RGID); err != nil {
			return 0, fmt.Errorf("notifier: mark sent for %s: %w", r.RGID, err)
		}
	}
	return len(unnotified), nil
}

// Schedule produces the next firing time strictly after the given time. It
// mirrors the robfig/cron Schedule interface so cron specs and simple
// interval-based schedules are interchangeable and testable.
type Schedule interface {
	Next(time.Time) time.Time
}

// notifyFunc is the unit of work the scheduler runs on each firing. It mirrors
// the signature of NotifyOnce so the scheduler can be tested with a stub.
type notifyFunc func(ctx context.Context) error

// StartScheduler runs the notify function on a schedule until ctx is cancelled.
// It is no-op-safe: if enabled is false it returns immediately without starting
// a goroutine. Each firing runs in its own goroutine so a slow send does not
// delay the next scheduled tick; the scheduler still computes the next tick from
// the wall clock and does not drift.
//
// The schedule and notify function are injectable so tests can drive a fixed or
// frequent schedule without a real cron spec or Telegram server.
func StartScheduler(ctx context.Context, enabled bool, schedule Schedule, notify notifyFunc, now func() time.Time) {
	if !enabled || schedule == nil || notify == nil {
		log.Println("Notifier scheduler disabled or misconfigured; not starting.")
		return
	}
	if now == nil {
		now = time.Now
	}

	go func() {
		timer := time.NewTimer(0)
		defer timer.Stop()
		// Fire immediately on start (startup digest), then schedule subsequent runs.
		first := true
		for {
			var wait time.Duration
			if first {
				first = false
				wait = 0
			} else {
				next := schedule.Next(now())
				if next.IsZero() {
					log.Println("Notifier schedule has no next fire; stopping scheduler.")
					return
				}
				wait = time.Until(next)
				if wait < 0 {
					wait = 0
				}
			}

			timer.Reset(wait)
			select {
			case <-ctx.Done():
				log.Println("Notifier scheduler stopped.")
				return
			case <-timer.C:
				go func() {
					if err := notify(ctx); err != nil {
						if ctx.Err() != nil {
							return
						}
						log.Printf("Notifier run failed: %v", err)
					}
				}()
			}
		}
	}()
}