refactor: enhance NewClient to support environment variable fallback and add tests

README.md

@@ -7,7 +7,11 @@ Go client library and CLI for the [Mail-in-a-Box](https://mailinabox.email/) adm
 ```go
 import miab "gitea.koszewscy.waw.pl/koszewscy/mailinabox-go"
 
-c := miab.NewClient("box.example.com", "admin@example.com", "password")
+// Explicit credentials:
+c, err := miab.NewClient("box.example.com", "admin@example.com", "password")
+
+// From environment variables (MIAB_* or MAILINABOX_* style):
+c, err := miab.NewClient("", "", "")
 
 c.SetRecord("foo.example.com", "TXT", "v=spf1 ~all")
 c.AddRecord("foo.example.com", "A", "1.2.3.4")
@@ -18,18 +22,30 @@ records, _ := c.ListRecords("TXT")
 
 ## CLI
 
-Install:
+Install from registry:
 
 ```sh
 go install gitea.koszewscy.waw.pl/koszewscy/mailinabox-go/cmd/miab@latest
 ```
 
-Credentials via environment variables:
+Build locally:
 
 ```sh
+go build -o miab ./cmd/miab
+```
+
+Credentials via environment variables (either style is accepted):
+
+```sh
+# MIAB style
 export MIAB_HOST=box.example.com
 export MIAB_USERNAME=admin@example.com
 export MIAB_PASSWORD=password
+
+# Mail-in-a-Box style
+export MAILINABOX_BASE_URL=https://box.example.com
+export MAILINABOX_EMAIL=admin@example.com
+export MAILINABOX_PASSWORD=password
 ```
 
 Commands:

cmd/miab/main.go

@@ -8,6 +8,7 @@ import (
 	miab "gitea.koszewscy.waw.pl/koszewscy/mailinabox-go"
 )
 
+
 func usage() {
 	fmt.Fprintf(os.Stderr, `Usage: miab <command> [options]
 
@@ -17,33 +18,21 @@ Commands:
   delete  Delete a DNS record
   add     Add a DNS record
 
-Credentials are read from environment variables:
+Credentials: any empty parameter falls back to environment variables.
-  MIAB_HOST      Mail-in-a-Box hostname (e.g. box.example.com)
+  MIAB_HOST / MAILINABOX_BASE_URL      Mail-in-a-Box hostname (MIAB_HOST takes precedence;
-  MIAB_USERNAME  Admin email address
+                                       hostname is parsed from MAILINABOX_BASE_URL if set)
-  MIAB_PASSWORD  Admin password
+  MIAB_USERNAME / MAILINABOX_EMAIL     Admin email address
+  MIAB_PASSWORD / MAILINABOX_PASSWORD  Admin password
 `)
 }
 
 func mustClient() *miab.Client {
-	host := os.Getenv("MIAB_HOST")
+	c, err := miab.NewClient("", "", "")
-	username := os.Getenv("MIAB_USERNAME")
+	if err != nil {
-	password := os.Getenv("MIAB_PASSWORD")
+		fmt.Fprintln(os.Stderr, err)
-
-	var missing []string
-	if host == "" {
-		missing = append(missing, "MIAB_HOST")
-	}
-	if username == "" {
-		missing = append(missing, "MIAB_USERNAME")
-	}
-	if password == "" {
-		missing = append(missing, "MIAB_PASSWORD")
-	}
-	if len(missing) > 0 {
-		fmt.Fprintf(os.Stderr, "miab: missing required environment variables: %v\n", missing)
 		os.Exit(1)
 	}
-	return miab.NewClient(host, username, password)
+	return c
 }
 
 func main() {

dns.go

@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
+	"os"
 	"strings"
 	"time"
 )
@@ -24,8 +26,51 @@ type DNSRecord struct {
 	Value string `json:"value"`
 }
 
-// NewClient constructs a Client. host should be the bare hostname (e.g. "box.example.com").
+// NewClient constructs a Client. Any empty parameter is filled from environment variables:
-func NewClient(host, username, password string) *Client {
+//
+//	host:     MIAB_HOST or hostname parsed from MAILINABOX_BASE_URL
+//	username: MIAB_USERNAME or MAILINABOX_EMAIL
+//	password: MIAB_PASSWORD or MAILINABOX_PASSWORD
+//
+// Returns an error if a value is still empty after the env lookup.
+func NewClient(host, username, password string) (*Client, error) {
+	if host == "" {
+		host = os.Getenv("MIAB_HOST")
+		if host == "" {
+			if base := os.Getenv("MAILINABOX_BASE_URL"); base != "" {
+				if u, err := url.Parse(base); err == nil {
+					host = u.Hostname()
+				}
+			}
+		}
+	}
+	if username == "" {
+		username = os.Getenv("MIAB_USERNAME")
+		if username == "" {
+			username = os.Getenv("MAILINABOX_EMAIL")
+		}
+	}
+	if password == "" {
+		password = os.Getenv("MIAB_PASSWORD")
+		if password == "" {
+			password = os.Getenv("MAILINABOX_PASSWORD")
+		}
+	}
+
+	var missing []string
+	if host == "" {
+		missing = append(missing, "MIAB_HOST or MAILINABOX_BASE_URL")
+	}
+	if username == "" {
+		missing = append(missing, "MIAB_USERNAME or MAILINABOX_EMAIL")
+	}
+	if password == "" {
+		missing = append(missing, "MIAB_PASSWORD or MAILINABOX_PASSWORD")
+	}
+	if len(missing) > 0 {
+		return nil, fmt.Errorf("miab: missing required environment variables: %v", missing)
+	}
+
 	return &Client{
 		host:     host,
 		username: username,
@@ -33,7 +78,7 @@ func NewClient(host, username, password string) *Client {
 		httpClient: &http.Client{
 			Timeout: 30 * time.Second,
 		},
-	}
+	}, nil
 }
 
 // SetRecord replaces all existing records of the given type for name with value (HTTP PUT).

dns_test.go

@@ -10,8 +10,74 @@ import (
 	"testing"
 )
 
+func TestNewClient_miabStyle(t *testing.T) {
+	t.Setenv("MIAB_HOST", "box.example.com")
+	t.Setenv("MIAB_USERNAME", "user@example.com")
+	t.Setenv("MIAB_PASSWORD", "secret")
+
+	c, err := NewClient("", "", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.host != "box.example.com" || c.username != "user@example.com" || c.password != "secret" {
+		t.Errorf("unexpected client fields: %+v", c)
+	}
+}
+
+func TestNewClient_mailinaboxStyle(t *testing.T) {
+	t.Setenv("MAILINABOX_BASE_URL", "https://box.example.com")
+	t.Setenv("MAILINABOX_EMAIL", "user@example.com")
+	t.Setenv("MAILINABOX_PASSWORD", "secret")
+
+	c, err := NewClient("", "", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.host != "box.example.com" || c.username != "user@example.com" || c.password != "secret" {
+		t.Errorf("unexpected client fields: %+v", c)
+	}
+}
+
+func TestNewClient_miabTakesPrecedence(t *testing.T) {
+	t.Setenv("MIAB_HOST", "miab.example.com")
+	t.Setenv("MIAB_USERNAME", "miab@example.com")
+	t.Setenv("MIAB_PASSWORD", "miabpass")
+	t.Setenv("MAILINABOX_BASE_URL", "https://other.example.com")
+	t.Setenv("MAILINABOX_EMAIL", "other@example.com")
+	t.Setenv("MAILINABOX_PASSWORD", "otherpass")
+
+	c, err := NewClient("", "", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.host != "miab.example.com" || c.username != "miab@example.com" || c.password != "miabpass" {
+		t.Errorf("MIAB_* vars should take precedence, got: %+v", c)
+	}
+}
+
+func TestNewClient_missingVars(t *testing.T) {
+	_, err := NewClient("", "", "")
+	if err == nil {
+		t.Fatal("expected error when no env vars set")
+	}
+}
+
+func TestNewClient_explicitParamsTakePrecedence(t *testing.T) {
+	t.Setenv("MIAB_HOST", "env.example.com")
+	t.Setenv("MIAB_USERNAME", "env@example.com")
+	t.Setenv("MIAB_PASSWORD", "envpass")
+
+	c, err := NewClient("explicit.example.com", "explicit@example.com", "explicitpass")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.host != "explicit.example.com" || c.username != "explicit@example.com" || c.password != "explicitpass" {
+		t.Errorf("explicit params should take precedence, got: %+v", c)
+	}
+}
+
 func TestBuildURL(t *testing.T) {
-	c := NewClient("box.example.com", "user", "pass")
+	c, _ := NewClient("box.example.com", "user", "pass")
 
 	tests := []struct {
 		name, recordType, want string
@@ -153,7 +219,10 @@ func TestErrorResponse(t *testing.T) {
 
 // testClient builds a Client pointed at the test server's host.
 func testClient(srv *httptest.Server) *Client {
-	c := NewClient(strings.TrimPrefix(srv.URL, "http://"), "user@example.com", "secret")
+	c, err := NewClient(strings.TrimPrefix(srv.URL, "http://"), "user@example.com", "secret")
+	if err != nil {
+		panic(err)
+	}
 	c.httpClient = srv.Client()
 	// Override buildURL to use http instead of https for the test server.
 	// We do this by wrapping the httpClient transport (no-op) and patching