Initial work on shortner package

shortner/normalize_url.go

@@ -0,0 +1,65 @@
+package shortner
+
+import (
+	"errors"
+	"net/url"
+)
+
+var errURLFileSchema = errors.New("Schema 'file://' not allowed")
+var errURLInvalid = errors.New("Invalid URL")
+
+var slashByte = byte(47)
+var maxLengthURL = 2048
+
+// NormalizeURL validates and normalizes given rawURL string.
+func NormalizeURL(rawURL []byte) ([]byte, error) {
+	url, err := normalizeURLPassOne(rawURL)
+	if err != nil {
+		return []byte{}, err
+	}
+
+	url, err = normalizeURLPassTwo(url)
+	if err != nil {
+		return []byte{}, err
+	}
+
+	return url, nil
+}
+
+func normalizeURLPassOne(rawURL []byte) ([]byte, error) {
+	if len(rawURL) > maxLengthURL {
+		return []byte{}, errURLInvalid
+	}
+
+	u, err := url.Parse(string(rawURL))
+	if err != nil {
+		return []byte{}, errURLInvalid
+	}
+
+	if u.Scheme == "" {
+		u.Scheme = "http"
+	}
+
+	if u.Scheme == "file" {
+		return []byte{}, errURLFileSchema
+	}
+
+	if u.Host == "" && (u.Path == "" || u.Path[0] == slashByte) {
+		return []byte{}, errURLInvalid
+	}
+
+	return []byte(u.String()), nil
+}
+
+func normalizeURLPassTwo(rawURL []byte) ([]byte, error) {
+	u, err := url.Parse(string(rawURL))
+	if err != nil {
+		return []byte{}, errURLInvalid
+	}
+
+	if u.Host != "" && u.Path == "" {
+		u.Path = "/"
+	}
+
+	return []byte(u.String()), nil
+}