remote_file kitten: Go connection-data parsing and ssh helpers

kittens/remote_file/ssh.go

@@ -0,0 +1,107 @@
+// License: GPLv3 Copyright: 2026, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package remote_file
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Must match kittens/remote_file/main.py is_ssh_kitten_sentinel
+const is_ssh_kitten_sentinel = `!#*&$#($ssh-kitten)(##$`
+
+type SSHConnectionData struct {
+	Binary           string
+	Hostname         string
+	Port             int
+	IdentityFile     string
+	IsSSHKitten      bool
+	SSHKittenCmdline []string
+}
+
+func parse_conn_data(raw string) (*SSHConnectionData, error) {
+	var items []any
+	if err := json.Unmarshal([]byte(raw), &items); err != nil {
+		return nil, fmt.Errorf("invalid --ssh-connection-data: %w", err)
+	}
+	if len(items) < 2 {
+		return nil, fmt.Errorf("invalid --ssh-connection-data: need at least binary and hostname")
+	}
+	first, _ := items[0].(string)
+	ans := &SSHConnectionData{}
+	if first == is_ssh_kitten_sentinel {
+		// Python: SSHConnectionData(sentinel, cli_data[-1], -1, identity_file=json.dumps(cli_data[1:]))
+		// with the cmdline stripped of -t flags and its last two items.
+		ans.IsSSHKitten = true
+		ans.Hostname, _ = items[len(items)-1].(string)
+		cmdline := make([]string, 0, len(items)-1)
+		for _, x := range items[1:] {
+			s, _ := x.(string)
+			if s != "-t" {
+				cmdline = append(cmdline, s)
+			}
+		}
+		if len(cmdline) >= 2 {
+			cmdline = cmdline[:len(cmdline)-2]
+		}
+		ans.SSHKittenCmdline = cmdline
+		return ans, nil
+	}
+	ans.Binary = first
+	ans.Hostname, _ = items[1].(string)
+	if len(items) > 2 {
+		if p, ok := items[2].(float64); ok {
+			ans.Port = int(p)
+		}
+	}
+	if len(items) > 3 {
+		ans.IdentityFile, _ = items[3].(string)
+	}
+	return ans, nil
+}
+
+func (c *SSHConnectionData) cmd_prefix() []string {
+	if c.IsSSHKitten {
+		return append([]string{}, c.SSHKittenCmdline...)
+	}
+	ans := []string{
+		c.Binary, "-o", fmt.Sprintf("ControlPath=~/.ssh/kitty-rf-%d-%%C", os.Getpid()),
+		"-o", "TCPKeepAlive=yes", "-o", "ControlPersist=yes",
+	}
+	if c.Port > 0 {
+		ans = append(ans, "-p", fmt.Sprint(c.Port))
+	}
+	if c.IdentityFile != "" {
+		ans = append(ans, "-i", c.IdentityFile)
+	}
+	return ans
+}
+
+func (c *SSHConnectionData) batch_cmd_prefix() []string {
+	if c.IsSSHKitten {
+		return c.cmd_prefix()
+	}
+	return append(c.cmd_prefix(), "-o", "BatchMode=yes")
+}
+
+func hostname_matches(from_hyperlink, actual string) bool {
+	if from_hyperlink == actual {
+		return true
+	}
+	fl, _, _ := strings.Cut(from_hyperlink, ".")
+	al, _, _ := strings.Cut(actual, ".")
+	return fl == al
+}
+
+func auto_rename_dest(dest string, exists func(string) bool) string {
+	q := dest
+	ext := filepath.Ext(dest)
+	base := strings.TrimSuffix(dest, ext)
+	for c := 1; exists(q); c++ {
+		q = fmt.Sprintf("%s-%d%s", base, c, ext)
+	}
+	return q
+}

kittens/remote_file/ssh_test.go

@@ -0,0 +1,77 @@
+// License: GPLv3 Copyright: 2026, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package remote_file
+
+import (
+	"fmt"
+	"os"
+	"slices"
+	"testing"
+)
+
+func TestParseConnData(t *testing.T) {
+	c, err := parse_conn_data(`["ssh", "myhost", 2222, "/id/file"]`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if c.Binary != "ssh" || c.Hostname != "myhost" || c.Port != 2222 || c.IdentityFile != "/id/file" || c.IsSSHKitten {
+		t.Fatalf("bad conn data: %+v", c)
+	}
+
+	c, err = parse_conn_data(`["ssh", "shorthost"]`)
+	if err != nil || c.Port != 0 || c.IdentityFile != "" {
+		t.Fatalf("optional fields: %+v err=%v", c, err)
+	}
+
+	raw := fmt.Sprintf(`["%s", "kitten", "ssh", "-t", "somehost", "cmd"]`, is_ssh_kitten_sentinel)
+	c, err = parse_conn_data(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !c.IsSSHKitten || c.Hostname != "cmd" || !slices.Equal(c.SSHKittenCmdline, []string{"kitten", "ssh"}) {
+		t.Fatalf("ssh kitten form: %+v", c)
+	}
+}
+
+func TestCmdPrefixes(t *testing.T) {
+	c := &SSHConnectionData{Binary: "ssh", Hostname: "h", Port: 2222, IdentityFile: "/id"}
+	p := c.cmd_prefix()
+	want := []string{
+		"ssh", "-o", fmt.Sprintf("ControlPath=~/.ssh/kitty-rf-%d-%%C", os.Getpid()),
+		"-o", "TCPKeepAlive=yes", "-o", "ControlPersist=yes", "-p", "2222", "-i", "/id",
+	}
+	if !slices.Equal(p, want) {
+		t.Fatalf("cmd_prefix:\n got %q\nwant %q", p, want)
+	}
+	b := c.batch_cmd_prefix()
+	if !slices.Equal(b, append(slices.Clone(want), "-o", "BatchMode=yes")) {
+		t.Fatalf("batch_cmd_prefix: %q", b)
+	}
+	sk := &SSHConnectionData{IsSSHKitten: true, SSHKittenCmdline: []string{"kitten", "ssh"}}
+	if !slices.Equal(sk.batch_cmd_prefix(), []string{"kitten", "ssh"}) {
+		t.Fatalf("ssh-kitten batch prefix must not add BatchMode: %q", sk.batch_cmd_prefix())
+	}
+}
+
+func TestHostnameMatches(t *testing.T) {
+	for _, tc := range []struct {
+		a, b string
+		want bool
+	}{
+		{"foo", "foo", true},
+		{"foo.example.com", "foo.local", true},
+		{"foo", "bar", false},
+	} {
+		if hostname_matches(tc.a, tc.b) != tc.want {
+			t.Fatalf("hostname_matches(%q, %q) != %v", tc.a, tc.b, tc.want)
+		}
+	}
+}
+
+func TestAutoRenameDest(t *testing.T) {
+	taken := map[string]bool{"/x/a.txt": true, "/x/a-1.txt": true}
+	got := auto_rename_dest("/x/a.txt", func(p string) bool { return taken[p] })
+	if got != "/x/a-2.txt" {
+		t.Fatalf("auto_rename_dest: %q", got)
+	}
+}