extra validations when specifying custom endpoint

config.go

@@ -1,9 +1,12 @@
 package posthog
 
 import (
-	"github.com/xtgo/uuid"
 	"net/http"
+	"net/url"
+	"strings"
 	"time"
+
+	"github.com/xtgo/uuid"
 )
 
 // Instances of this type carry the different configuration options that may
@@ -13,8 +16,9 @@ import (
 // default value defined by the library.
 type Config struct {
 
-	// The endpoint to which the client connect and send their messages, set to
-	// `DefaultEndpoint` by default.
+	// The endpoint to which the client connects and send their messages to;
+	// endpoint should be a URL such as https://your.domain.com;
+	// set to `DefaultEndpoint` by default.
 	Endpoint string
 
 	// You must specify a Personal API Key to use feature flags
@@ -116,6 +120,29 @@ func (c *Config) validate() error {
 		}
 	}
 
+	if c.Endpoint != "" {
+		u, err := url.ParseRequestURI(c.Endpoint)
+		if err != nil {
+			return ConfigError{
+				Reason: "invalid endpoint URL",
+				Field:  "Endpoint",
+				Value:  c.Endpoint,
+			}
+		}
+
+		// Need a stricter check because url.ParseRequestURI() can parse a host
+		// address as the scheme in some situations (ie. "localhost:8080")
+		if u.Scheme != "" && u.Host == "" {
+			return ConfigError{
+				Reason: "missing URL scheme in endpoint URL",
+				Field:  "Endpoint",
+				Value:  c.Endpoint,
+			}
+		}
+
+		c.Endpoint = strings.TrimSuffix(c.Endpoint, "/")
+	}
+
 	return nil
 }
 

posthog_test.go

@@ -503,6 +503,56 @@ func TestClientConfigError(t *testing.T) {
 	}
 }
 
+func TestNewWithConfigEndpoints(t *testing.T) {
+	type testCase struct {
+		description string
+		value       string
+		mustError   bool
+	}
+
+	testCases := []testCase{
+		{
+			description: "valid config 1",
+			value:       "http://localhost:9999",
+		},
+		{
+			description: "valid config 2",
+			value:       "https://some-domain/",
+		},
+		{
+			description: "invalid url",
+			value:       "invalid-url",
+			mustError:   true,
+		},
+		{
+			description: "URL without scheme",
+			value:       "localhost:9999",
+			mustError:   true,
+		},
+	}
+
+	for _, v := range testCases {
+		client, err := NewWithConfig("0123456789", Config{
+			Endpoint: v.value,
+		})
+		if client != nil {
+			defer client.Close()
+		}
+
+		if err != nil && !v.mustError {
+			t.Errorf("expected no error, got error (case: '%s', value: '%s'): %s",
+				v.description, v.value, err)
+			continue
+		}
+
+		if err == nil && v.mustError {
+			t.Errorf("expected error, got nil (case: '%s', value: '%s'): %s",
+				v.description, v.value, err)
+			continue
+		}
+	}
+}
+
 func TestClientEnqueueError(t *testing.T) {
 	client := New("0123456789")
 	defer client.Close()