// NextPageURL is invoked when a paginated collection of networks has reached
// the end of a page and the pager seeks to traverse over a new one. In order
// to do this, it needs to construct the next page's URL.
func (r NetworkPage) NextPageURL() (string, error) {
	var s struct {
		Links []gophercloud.Link `json:"networks_links"`
	}
	err := r.ExtractInto(&s)
	if err != nil {
		return "", err
	}
	return gophercloud.ExtractNextURL(s.Links)
}

// NextPageURL will retrieve the next page URL.
func (page DBPage) NextPageURL() (string, error) {
	var s struct {
		Links []gophercloud.Link `json:"databases_links"`
	}
	err := page.ExtractInto(&s)
	if err != nil {
		return "", err
	}
	return gophercloud.ExtractNextURL(s.Links)
}

// NextPageURL is invoked when a paginated collection of firewall rules has
// reached the end of a page and the pager seeks to traverse over a new one.
// In order to do this, it needs to construct the next page's URL.
func (r RulePage) NextPageURL() (string, error) {
	var s struct {
		Links []gophercloud.Link `json:"firewall_rules_links"`
	}
	err := r.ExtractInto(&s)
	if err != nil {
		return "", err
	}
	return gophercloud.ExtractNextURL(s.Links)
}

// NextPageURL is invoked when a paginated collection of security group rules has
// reached the end of a page and the pager seeks to traverse over a new one. In
// order to do this, it needs to construct the next page's URL.
func (r SecGroupRulePage) NextPageURL() (string, error) {
	var s struct {
		Links []gophercloud.Link `json:"security_group_rules_links"`
	}
	err := r.ExtractInto(&s)
	if err != nil {
		return "", err
	}
	return gophercloud.ExtractNextURL(s.Links)
}

// NextPageURL is invoked when a paginated collection of routers has reached
// the end of a page and the pager seeks to traverse over a new one. In order
// to do this, it needs to construct the next page's URL.
func (r LoadBalancerPage) NextPageURL() (string, error) {
	var s struct {
		Links []gophercloud.Link `json:"loadbalancers_links"`
	}
	err := r.ExtractInto(&s)
	if err != nil {
		return "", err
	}
	return gophercloud.ExtractNextURL(s.Links)
}

// NextPageURL is invoked when a paginated collection of monitors has reached
// the end of a page and the pager seeks to traverse over a new one. In order
// to do this, it needs to construct the next page's URL.
func (r MonitorPage) NextPageURL() (string, error) {
	var s struct {
		Links []gophercloud.Link `json:"health_monitors_links"`
	}
	err := r.ExtractInto(&s)
	if err != nil {
		return "", err
	}

	return gophercloud.ExtractNextURL(s.Links)
}