package models

import (
	"fmt"
	"time"

	"gorm.io/gorm"
)

const maintenanceStartNotificationPrefix = "maintenance:%d:start:"

// MaintenanceStartNotificationKey uniquely identifies one contact's warning
// for one schedule revision and occurrence. Updated windows get a new revision
// while concurrent scheduler replicas share the same key.
func MaintenanceStartNotificationKey(maintenanceID int64, revision, startsAt time.Time, timezone string, notificationID, contactID int64) string {
	loc, err := time.LoadLocation(timezone)
	if err != nil || timezone == "SAME_AS_SERVER" || timezone == "" {
		loc = time.UTC
	}
	// A fall-back hour can have two UTC instants for one wall-clock occurrence.
	// Warnings are once per civil occurrence, matching the recurrence editor.
	civilOccurrence := startsAt.In(loc).Format("200601021504")
	return fmt.Sprintf("maintenance:%d:start:%d:%s:notification:%d:contact:%d", maintenanceID, revision.UnixNano(), civilOccurrence, notificationID, contactID)
}

// CancelMaintenanceStartNotificationsTx prevents queued warnings from being
// delivered after an operator pauses, changes, or deletes the maintenance.
// Leased work may already be executing and cannot be recalled from a worker.
func CancelMaintenanceStartNotificationsTx(tx *gorm.DB, maintenanceID int64, reason string) error {
	prefix := fmt.Sprintf(maintenanceStartNotificationPrefix, maintenanceID) + "%"
	var tasks []Task
	if err := tx.Clauses(SkipLockedClause).Where("idempotency_key LIKE ? AND state IN ?", prefix, []string{TaskStateQueued, TaskStateFailedRetry}).Find(&tasks).Error; err != nil {
		return err
	}
	for i := range tasks {
		if err := tx.Model(&Task{}).Where("id = ? AND state IN ?", tasks[i].ID, []string{TaskStateQueued, TaskStateFailedRetry}).Updates(map[string]any{"state": TaskStateDead, "last_error": "canceled: " + reason, "payload": []byte(`{}`), "lease_owner": "", "lease_token": "", "lease_expires_at": nil}).Error; err != nil {
			return err
		}
		if err := FinalizeNotificationTaskTx(tx, &tasks[i], "canceled", "canceled: "+reason); err != nil {
			return err
		}
	}
	return nil
}