package gophercloud

// CommonResult acts as a base struct that other results can embed. It contains
// the deserialized JSON structure returned from the server (Resp), and any
// errors that might have occurred during transport or deserialization.
type CommonResult struct {
	Resp map[string]interface{}
	Err  error
}

// RFC3339Milli describes a time format used by API responses.
const RFC3339Milli = "2006-01-02T15:04:05.999999Z"

// Link represents a structure that enables paginated collections how to
// traverse backward or forward. The "Rel" field is usually either "next".
type Link struct {
	Href string `mapstructure:"href"`
	Rel  string `mapstructure:"rel"`
}

// ExtractNextURL attempts to extract the next URL from a JSON structure. It
// follows the common structure of nesting back and next links.
func ExtractNextURL(links []Link) (string, error) {
	var url string

	for _, l := range links {
		if l.Rel == "next" {
			url = l.Href
		}
	}

	if url == "" {
		return "", nil
	}

	return url, nil
}