package scheduler

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"time"

	"github.com/calendarapi/internal/repository"
	"github.com/calendarapi/internal/utils"
	"github.com/google/uuid"
	"github.com/hibiken/asynq"
)

const TypeReminder = "reminder:send"
const TypeSubscriptionSync = "subscription:sync"

type ReminderPayload struct {
	EventID    uuid.UUID `json:"event_id"`
	ReminderID uuid.UUID `json:"reminder_id"`
	UserID     uuid.UUID `json:"user_id"`
}

type Scheduler struct {
	client *asynq.Client
}

func NewScheduler(redisAddr string) *Scheduler {
	client := asynq.NewClient(asynq.RedisClientOpt{Addr: redisAddr})
	return &Scheduler{client: client}
}

func (s *Scheduler) ScheduleReminder(_ context.Context, eventID, reminderID, userID uuid.UUID, triggerAt time.Time) error {
	payload, err := json.Marshal(ReminderPayload{
		EventID:    eventID,
		ReminderID: reminderID,
		UserID:     userID,
	})
	if err != nil {
		return fmt.Errorf("marshal reminder payload: %w", err)
	}

	task := asynq.NewTask(TypeReminder, payload)
	_, err = s.client.Enqueue(task,
		asynq.ProcessAt(triggerAt),
		asynq.MaxRetry(5),
		asynq.Queue("reminders"),
	)
	if err != nil {
		return fmt.Errorf("enqueue reminder: %w", err)
	}

	return nil
}

type SubscriptionSyncPayload struct {
	SubscriptionID string `json:"subscription_id"`
}

func (s *Scheduler) EnqueueSubscriptionSync(ctx context.Context, subscriptionID string) error {
	payload, err := json.Marshal(SubscriptionSyncPayload{SubscriptionID: subscriptionID})
	if err != nil {
		return fmt.Errorf("marshal subscription sync payload: %w", err)
	}
	task := asynq.NewTask(TypeSubscriptionSync, payload)
	_, err = s.client.Enqueue(task,
		asynq.MaxRetry(3),
		asynq.Queue("subscriptions"),
	)
	if err != nil {
		return fmt.Errorf("enqueue subscription sync: %w", err)
	}
	return nil
}

func (s *Scheduler) Close() error {
	return s.client.Close()
}

// StartSubscriptionEnqueuer runs a goroutine that every interval lists subscriptions due for sync
// and enqueues a sync task for each. Call with a cancellable context to stop.
func StartSubscriptionEnqueuer(ctx context.Context, queries *repository.Queries, sched *Scheduler, interval time.Duration) {
	ticker := time.NewTicker(interval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			subs, err := queries.ListSubscriptionsDueForSync(ctx)
			if err != nil {
				log.Printf("subscription enqueuer: list due for sync: %v", err)
				continue
			}
			for _, sub := range subs {
				subID := utils.FromPgUUID(sub.ID)
				if err := sched.EnqueueSubscriptionSync(ctx, subID.String()); err != nil {
					log.Printf("subscription enqueuer: enqueue %s: %v", subID, err)
				}
			}
			if len(subs) > 0 {
				log.Printf("subscription enqueuer: enqueued %d subscriptions", len(subs))
			}
		}
	}
}

type NoopScheduler struct{}

func (NoopScheduler) ScheduleReminder(_ context.Context, _, _, _ uuid.UUID, _ time.Time) error {
	return nil
}

func (NoopScheduler) Close() error { return nil }