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link.go
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link.go
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package api
import (
"fmt"
"net/http"
"net/url"
"strings"
)
// GetNextLink reads the `Link` response headers, and returns the first URI
// tagged as `rel="next"`. Relative URIs are evaluated against the original
// request if possible. See RFC 5899.
func GetNextLink(resp *http.Response) (*url.URL, error) {
rawuri, ok := uriFromLinks(resp.Header.Values("Link"), `rel`, `next`)
if !ok {
return nil, fmt.Errorf(`rel="next": no match`)
}
if resp.Request != nil && resp.Request.URL != nil {
return resp.Request.URL.Parse(rawuri)
}
return url.Parse(rawuri)
}
func uriFromLinks(links []string, k, v string) (string, bool) {
for _, link := range links {
if rawuri, ok := uriFromLink(link, k, v); ok {
return rawuri, true
}
}
return "", false
}
func uriFromLink(link, k, v string) (string, bool) {
var rawuri string
for _, param := range strings.Split(link, ";") {
param = strings.TrimSpace(param)
if param == "" {
continue
}
if rawuri == "" && param[0] == '<' && param[len(param)-1] == '>' {
rawuri = strings.Trim(param, "<>")
continue
}
keyval := strings.SplitN(param, "=", 2)
if len(keyval) != 2 {
continue
}
key := strings.TrimSpace(keyval[0])
if !strings.EqualFold(key, k) {
continue
}
var val string
val = keyval[1]
val = strings.TrimSpace(val)
val = strings.Trim(val, `"`)
val = strings.TrimSpace(val)
if !strings.EqualFold(val, v) {
continue
}
if rawuri != "" {
return rawuri, true
}
}
return "", false
}