added function to fetch NIP-11 documents

nip11/fetch.go

@@ -0,0 +1,54 @@
+package nip11
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"net/http"
+	"net/url"
+	"strings"
+
+	"time"
+)
+
+
+// Fetch fetches the NIP-11 RelayInformationDocument.
+func Fetch(ctx context.Context, u string) (info *RelayInformationDocument, err error) {
+	if _, ok := ctx.Deadline(); !ok {
+		// if no timeout is set, force it to 7 seconds
+		var cancel context.CancelFunc
+		ctx, cancel = context.WithTimeout(ctx, 7*time.Second)
+		defer cancel()
+	}
+
+	// normalize URL to start with http:// or https://
+	if !strings.HasPrefix(u, "http") && !strings.HasPrefix(u, "ws") {
+		u = "wss://" + u
+	}
+	p, err := url.Parse(u)
+	if err != nil {
+		return nil, fmt.Errorf("Cannot parse url: %s", u)
+	}
+	if p.Scheme == "ws" {
+		p.Scheme = "http"
+	} else if p.Scheme == "wss" {
+		p.Scheme = "https"
+	}
+	p.Path = strings.TrimRight(p.Path, "/")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, p.String(), nil)
+
+	// add the NIP-11 header
+	req.Header.Add("Accept", "application/nostr+json")
+
+	// send the request
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	info = &RelayInformationDocument{}
+	dec := json.NewDecoder(resp.Body)
+	err = dec.Decode(info)
+	return info, err
+}

normalize.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 )
 
+// NormalizeURL normalizes the url and replaces http://, https:// schemes by ws://, wss://.
 func NormalizeURL(u string) string {
 	if u == "" {
 		return ""