Externalize sync targets from hardcoded constants to env/config

- Added SyncTargets and SyncRemoteDir to internal/config.Config.
- Replaced the package-level syncTargets and syncRemoteDir constants in
  cmd/snonux/sync.go with default values, populated lazily via
  resolveSyncConfig().
- Accept --sync-targets and --sync-remote-dir CLI flags; fall back to
  SNONUX_SYNC_TARGETS and SNONUX_SYNC_REMOTE_DIR env vars; then fall back
  to the previous hardcoded defaults (pi0/pi1, /var/www/html/snonux/).

4 files changed, 195 insertions, 9 deletions

diff --git a/cmd/snonux/main.go b/cmd/snonux/main.go
index 75e386e..659bd19 100644
--- a/cmd/snonux/main.go
+++ b/cmd/snonux/main.go
@@ -66,7 +66,7 @@ func main() {
 	}
 
 	if cfg.Sync {
-		if err := syncOutput(cfg.OutputDir); err != nil {
+		if err := syncOutput(cfg); err != nil {
 			log.Fatalf("error: %v", err)
 		}
 	}
@@ -91,12 +91,19 @@ func parseFlags(args []string) (*config.Config, cliMode, error) {
 	fs.StringVar(&cfg.OutputDir, "output", "./dist", "root directory for generated static site output")
 	fs.StringVar(&cfg.BaseURL, "base-url", "https://snonux.foo", "canonical base URL used in Atom feed links")
 	fs.StringVar(&cfg.Theme, "theme", "random", "visual theme name, or \"random\" to pick one at random")
-	fs.BoolVar(&cfg.Sync, "sync", false, "after a successful run, rsync -output to pi0/pi1 when both are pingable (SSH user: SNONUX_SYNC_USER or login name)")
+	fs.BoolVar(&cfg.Sync, "sync", false, "after a successful run, rsync -output to mirror hosts when all are pingable (SSH user: SNONUX_SYNC_USER or login name)")
+	var syncTargets string
+	fs.StringVar(&syncTargets, "sync-targets", "", "comma-separated list of rsync target hosts (overrides SNONUX_SYNC_TARGETS and defaults)")
+	fs.StringVar(&cfg.SyncRemoteDir, "sync-remote-dir", "", "remote destination directory on target hosts (overrides SNONUX_SYNC_REMOTE_DIR and default)")
 
 	if err := fs.Parse(args); err != nil {
 		return nil, modeRun, fmt.Errorf("%w: %w", errParseFlags, err)
 	}
 
+	if syncTargets != "" {
+		cfg.SyncTargets = splitAndTrim(syncTargets)
+	}
+
 	if showVersion {
 		return nil, modeVersion, nil
 	}
diff --git a/cmd/snonux/main_test.go b/cmd/snonux/main_test.go
index a4fe22f..b8a5a82 100644
--- a/cmd/snonux/main_test.go
+++ b/cmd/snonux/main_test.go
@@ -121,6 +121,47 @@ func TestParseFlags_sync(t *testing.T) {
 	if !cfg.Sync {
 		t.Fatal("expected cfg.Sync")
 	}
+	// Defaults should be empty until resolved at sync time.
+	if len(cfg.SyncTargets) != 0 {
+		t.Fatalf("expected no sync targets from flags alone, got %v", cfg.SyncTargets)
+	}
+	if cfg.SyncRemoteDir != "" {
+		t.Fatalf("expected empty remote dir from flags alone, got %q", cfg.SyncRemoteDir)
+	}
+}
+
+func TestParseFlags_syncTargetsAndRemoteDir(t *testing.T) {
+	t.Parallel()
+
+	cfg, mode, err := parseFlags([]string{
+		"-input", "./in",
+		"-output", "./out",
+		"-theme", "neon",
+		"-sync",
+		"-sync-targets", "host1, host2,host3",
+		"-sync-remote-dir", "/var/www/custom/",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if mode != modeRun {
+		t.Fatalf("mode %v", mode)
+	}
+	if !cfg.Sync {
+		t.Fatal("expected cfg.Sync")
+	}
+	want := []string{"host1", "host2", "host3"}
+	if len(cfg.SyncTargets) != len(want) {
+		t.Fatalf("got targets %v, want %v", cfg.SyncTargets, want)
+	}
+	for i, v := range want {
+		if cfg.SyncTargets[i] != v {
+			t.Fatalf("target[%d] = %q, want %q", i, cfg.SyncTargets[i], v)
+		}
+	}
+	if cfg.SyncRemoteDir != "/var/www/custom/" {
+		t.Fatalf("got remote dir %q", cfg.SyncRemoteDir)
+	}
 }
 
 func TestResolvePaths(t *testing.T) {
diff --git a/cmd/snonux/sync.go b/cmd/snonux/sync.go
index 46993e2..f5d2e9e 100644
--- a/cmd/snonux/sync.go
+++ b/cmd/snonux/sync.go
@@ -8,23 +8,60 @@ import (
 	"os/exec"
 	"os/user"
 	"path/filepath"
+	"strings"
 	"time"
+
+	"codeberg.org/snonux/snonux/internal/config"
 )
 
 // SNONUX_SYNC_USER overrides the SSH username for rsync (default: current login name).
 const envSyncUser = "SNONUX_SYNC_USER"
 
-var syncTargets = []string{
+// defaultSyncTargets are the built-in mirror hosts used when no configuration overrides them.
+var defaultSyncTargets = []string{
 	"pi0.lan.buetow.org",
 	"pi1.lan.buetow.org",
 }
 
-const syncRemoteDir = "/var/www/html/snonux/"
+const defaultSyncRemoteDir = "/var/www/html/snonux/"
+
+// resolveSyncConfig populates cfg.SyncTargets and cfg.SyncRemoteDir from the
+// environment if they are empty, applying sensible defaults.
+func resolveSyncConfig(cfg *config.Config) {
+	if len(cfg.SyncTargets) == 0 {
+		if v := os.Getenv("SNONUX_SYNC_TARGETS"); v != "" {
+			cfg.SyncTargets = splitAndTrim(v)
+		} else {
+			cfg.SyncTargets = append([]string(nil), defaultSyncTargets...)
+		}
+	}
+	if cfg.SyncRemoteDir == "" {
+		if v := os.Getenv("SNONUX_SYNC_REMOTE_DIR"); v != "" {
+			cfg.SyncRemoteDir = strings.TrimSpace(v)
+		} else {
+			cfg.SyncRemoteDir = defaultSyncRemoteDir
+		}
+	}
+}
+
+func splitAndTrim(s string) []string {
+	parts := strings.Split(s, ",")
+	out := make([]string, 0, len(parts))
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p != "" {
+			out = append(out, p)
+		}
+	}
+	return out
+}
 
 // syncOutput rsyncs localOutput (trailing-slash source) to each sync target over SSH
 // port 22. It runs only if every target answers ICMP ping (Linux iputils: ping -c 1 -W …).
-func syncOutput(localOutput string) error {
-	for _, host := range syncTargets {
+func syncOutput(cfg *config.Config) error {
+	resolveSyncConfig(cfg)
+
+	for _, host := range cfg.SyncTargets {
 		if !hostPingable(host) {
 			log.Printf("sync skipped: %q not pingable (all mirror hosts must be reachable)", host)
 			return nil
@@ -40,15 +77,15 @@ func syncOutput(localOutput string) error {
 		sshUser = u.Username
 	}
 
-	absOut, err := filepath.Abs(localOutput)
+	absOut, err := filepath.Abs(cfg.OutputDir)
 	if err != nil {
 		return fmt.Errorf("sync output dir: %w", err)
 	}
 	src := filepath.Clean(absOut) + string(filepath.Separator)
 
 	ssh := "ssh -p 22 -o BatchMode=yes -o ConnectTimeout=15"
-	for _, host := range syncTargets {
-		dest := fmt.Sprintf("%s@%s:%s", sshUser, host, syncRemoteDir)
+	for _, host := range cfg.SyncTargets {
+		dest := fmt.Sprintf("%s@%s:%s", sshUser, host, cfg.SyncRemoteDir)
 		log.Printf("rsync %s -> %s", src, dest)
 		cmd := exec.Command("rsync", "-az", "-e", ssh, src, dest)
 		cmd.Stdout = os.Stdout
diff --git a/cmd/snonux/sync_test.go b/cmd/snonux/sync_test.go
new file mode 100644
index 0000000..d45a916
--- /dev/null
+++ b/cmd/snonux/sync_test.go
@@ -0,0 +1,101 @@
+package main
+
+import (
+	"os"
+	"reflect"
+	"testing"
+
+	"codeberg.org/snonux/snonux/internal/config"
+)
+
+func TestSplitAndTrim(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		in   string
+		want []string
+	}{
+		{"a,b,c", []string{"a", "b", "c"}},
+		{" a , b ", []string{"a", "b"}},
+		{"a,,c", []string{"a", "c"}},
+		{"", []string{}},
+		{",,", []string{}},
+	}
+
+	for _, c := range cases {
+		got := splitAndTrim(c.in)
+		if !reflect.DeepEqual(got, c.want) {
+			t.Errorf("splitAndTrim(%q) = %v; want %v", c.in, got, c.want)
+		}
+	}
+}
+
+func TestResolveSyncConfig_defaults(t *testing.T) {
+	t.Parallel()
+
+	cfg := &config.Config{}
+	resolveSyncConfig(cfg)
+	want := []string{"pi0.lan.buetow.org", "pi1.lan.buetow.org"}
+	if !reflect.DeepEqual(cfg.SyncTargets, want) {
+		t.Fatalf("got targets %v, want %v", cfg.SyncTargets, want)
+	}
+	if cfg.SyncRemoteDir != "/var/www/html/snonux/" {
+		t.Fatalf("got remote dir %q", cfg.SyncRemoteDir)
+	}
+}
+
+func TestResolveSyncConfig_envTargets(t *testing.T) {
+	t.Parallel()
+
+	orig := os.Getenv("SNONUX_SYNC_TARGETS")
+	defer os.Setenv("SNONUX_SYNC_TARGETS", orig)
+
+	os.Setenv("SNONUX_SYNC_TARGETS", "h1, h2 ,h3")
+	cfg := &config.Config{}
+	resolveSyncConfig(cfg)
+	want := []string{"h1", "h2", "h3"}
+	if !reflect.DeepEqual(cfg.SyncTargets, want) {
+		t.Fatalf("got targets %v, want %v", cfg.SyncTargets, want)
+	}
+}
+
+func TestResolveSyncConfig_envRemoteDir(t *testing.T) {
+	t.Parallel()
+
+	orig := os.Getenv("SNONUX_SYNC_REMOTE_DIR")
+	defer os.Setenv("SNONUX_SYNC_REMOTE_DIR", orig)
+
+	os.Setenv("SNONUX_SYNC_REMOTE_DIR", "/custom/path/")
+	cfg := &config.Config{}
+	resolveSyncConfig(cfg)
+	if cfg.SyncRemoteDir != "/custom/path/" {
+		t.Fatalf("got remote dir %q", cfg.SyncRemoteDir)
+	}
+}
+
+func TestResolveSyncConfig_flagsOverrideEnv(t *testing.T) {
+	t.Parallel()
+
+	origTargets := os.Getenv("SNONUX_SYNC_TARGETS")
+	origDir := os.Getenv("SNONUX_SYNC_REMOTE_DIR")
+	defer func() {
+		os.Setenv("SNONUX_SYNC_TARGETS", origTargets)
+		os.Setenv("SNONUX_SYNC_REMOTE_DIR", origDir)
+	}()
+
+	os.Setenv("SNONUX_SYNC_TARGETS", "from-env")
+	os.Setenv("SNONUX_SYNC_REMOTE_DIR", "/env/dir/")
+
+	cfg := &config.Config{
+		SyncTargets:     []string{"from-flag"},
+		SyncRemoteDir:   "/flag/dir/",
+	}
+	resolveSyncConfig(cfg)
+
+	if !reflect.DeepEqual(cfg.SyncTargets, []string{"from-flag"}) {
+		t.Fatalf("flag targets should override env: got %v", cfg.SyncTargets)
+	}
+	if cfg.SyncRemoteDir != "/flag/dir/" {
+		t.Fatalf("flag dir should override env: got %q", cfg.SyncRemoteDir)
+	}
+}