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package pagination
import "fmt"
// LinkedPageBase may be embedded to implement a page that provides navigational "Next" and "Previous" links within its result.
type LinkedPageBase struct {
PageResult
// LinkPath lists the keys that should be traversed within a response to arrive at the "next" pointer.
// If any link along the path is missing, an empty URL will be returned.
// If any link results in an unexpected value type, an error will be returned.
// When left as "nil", []string{"links", "next"} will be used as a default.
LinkPath []string
}
// NextPageURL extracts the pagination structure from a JSON response and returns the "next" link, if one is present.
// It assumes that the links are available in a "links" element of the top-level response object.
// If this is not the case, override NextPageURL on your result type.
func (current LinkedPageBase) NextPageURL() (string, error) {
var path []string
var key string
if current.LinkPath == nil {
path = []string{"links", "next"}
} else {
path = current.LinkPath
}
submap, ok := current.Body.(map[string]interface{})
if !ok {
return "", fmt.Errorf("Expected an object, but was %#v", current.Body)
}
for {
key, path = path[0], path[1:len(path)]
value, ok := submap[key]
if !ok {
return "", nil
}
if len(path) > 0 {
submap, ok = value.(map[string]interface{})
if !ok {
return "", fmt.Errorf("Expected an object, but was %#v", value)
}
} else {
if value == nil {
// Actual null element.
return "", nil
}
url, ok := value.(string)
if !ok {
return "", fmt.Errorf("Expected a string, but was %#v", value)
}
return url, nil
}
}
}
// GetBody returns the linked page's body. This method is needed to satisfy the
// Page interface.
func (current LinkedPageBase) GetBody() interface{} {
return current.Body
}
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