package pagination

import (

	"fmt"

	"reflect"

	"github.com/gophercloud/gophercloud"

)

// MarkerPage is a stricter Page interface that describes additional functionality required for use with NewMarkerPager.

// For convenience, embed the MarkedPageBase struct.

type MarkerPage interface {

	Page

	// LastMarker returns the last "marker" value on this page.

	LastMarker() (string, error)

}

// MarkerPageBase is a page in a collection that's paginated by "limit" and "marker" query parameters.

type MarkerPageBase struct {

	PageResult

	// Owner is a reference to the embedding struct.

	Owner MarkerPage

}

// NextPageURL generates the URL for the page of results after this one.

func (current MarkerPageBase) NextPageURL() (string, error) {

	currentURL := current.URL

	mark, err := current.Owner.LastMarker()

	if err != nil {

		return "", err

	}

	q := currentURL.Query()

	q.Set("marker", mark)

	currentURL.RawQuery = q.Encode()

	return currentURL.String(), nil

}

// IsEmpty satisifies the IsEmpty method of the Page interface

func (current MarkerPageBase) IsEmpty() (bool, error) {

	if b, ok := current.Body.([]interface{}); ok {

		return len(b) == 0, nil

	}

	err := gophercloud.ErrUnexpectedType{}

	err.Expected = "[]interface{}"

	err.Actual = fmt.Sprintf("%v", reflect.TypeOf(current.Body))

	return true, err

}

// GetBody returns the linked page's body. This method is needed to satisfy the

// Page interface.

func (current MarkerPageBase) GetBody() interface{} {

	return current.Body

}