package store

import (
	"context"
	"fmt"
	"time"
)

// DeviceActivityRetention is how long the per-day marks are kept. They are not history
// anybody reads — the notification they produced is the record, and that is itself pruned
// at thirty days — so this only has to be long enough that a clock correction or a
// database restored from a backup cannot make yesterday look like a day that never
// happened.
const DeviceActivityRetention = 90 * 24 * time.Hour

// MarkDeviceDay records that a television was in use on a household-local day, and
// reports whether this is the first time it has been seen today.
//
// The answer comes from the insert rather than from a read followed by a write, because
// every set in the house can reach this at once and two of them racing on the same row
// must not both be told they were first. `ON CONFLICT DO NOTHING` makes the primary key
// the arbiter: exactly one insert affects a row.
//
// It is keyed on the viewer as well as the television because a household set that two
// people sign into is two people opening Memby, and an operator reading the feed wants to
// know which of them it was.
func (s *Store) MarkDeviceDay(
	ctx context.Context, deviceID, userID string, day time.Time,
) (bool, error) {
	if deviceID == "" {
		return false, nil
	}
	tag, err := s.pool.Exec(ctx, `
		INSERT INTO device_activity_days (device_id, emby_user_id, day)
		VALUES ($1, $2, $3)
		ON CONFLICT (device_id, emby_user_id, day) DO NOTHING`,
		deviceID, userID, day.Format("2006-01-02"))
	if err != nil {
		return false, fmt.Errorf("store: mark device day: %w", err)
	}
	return tag.RowsAffected() > 0, nil
}

// PruneDeviceActivityDays drops marks older than the retention window.
func (s *Store) PruneDeviceActivityDays(
	ctx context.Context, retention time.Duration,
) (int64, error) {
	if retention <= 0 {
		retention = DeviceActivityRetention
	}
	tag, err := s.pool.Exec(ctx,
		`DELETE FROM device_activity_days WHERE first_seen_at < now() - $1::interval`,
		fmt.Sprintf("%d seconds", int64(retention.Seconds())))
	if err != nil {
		return 0, fmt.Errorf("store: prune device activity days: %w", err)
	}
	return tag.RowsAffected(), nil
}

// DeleteDeviceActivityDays retires a television's marks along with the television, the
// way its build history is retired: a set that is gone must not be able to announce a
// first use it can no longer have.
func (s *Store) DeleteDeviceActivityDays(ctx context.Context, deviceIDs ...string) error {
	if len(deviceIDs) == 0 {
		return nil
	}
	_, err := s.pool.Exec(ctx,
		`DELETE FROM device_activity_days WHERE device_id = ANY($1::text[])`, deviceIDs)
	if err != nil {
		return fmt.Errorf("store: delete device activity days: %w", err)
	}
	return nil
}