1 files changed, 85 insertions, 0 deletions
diff --git a/internal/tmux/tmux.go b/internal/tmux/tmux.go
new file mode 100644
index 0000000..63b5660
--- /dev/null
+++ b/internal/tmux/tmux.go
@@ -0,0 +1,85 @@
+package tmux
+
+import (
+    "os"
+    "os/exec"
+    "strconv"
+    "strings"
+)
+
+// Available reports whether tmux is available and we appear to be in a tmux session.
+func Available() bool { return HasBinary() && InSession() }
+
+// HasBinary reports whether the tmux binary is on PATH.
+var lookPath = exec.LookPath
+var command = exec.Command
+
+func HasBinary() bool { _, err := lookPath("tmux"); return err == nil }
+
+// InSession reports whether we seem to be running inside a tmux session.
+func InSession() bool { return strings.TrimSpace(os.Getenv("TMUX")) != "" }
+
+// SplitOpts controls how a new pane is created for running a command.
+type SplitOpts struct {
+	Target   string // optional pane target, e.g. ":."
+	Vertical bool   // true => split vertically (-v); false => horizontally (-h)
+	Percent  int    // 1..100; 0 means use tmux default
+}
+
+// SplitRun splits the current tmux window and runs argv in the new pane.
+// It returns once tmux has launched the child process.
+func SplitRun(opts SplitOpts, argv []string) error {
+	if len(argv) == 0 {
+		return nil
+	}
+	args := []string{"split-window"}
+	if opts.Vertical {
+		args = append(args, "-v")
+	} else {
+		args = append(args, "-h")
+	}
+	if opts.Percent > 0 && opts.Percent <= 100 {
+		args = append(args, "-p", strconv.Itoa(opts.Percent))
+	}
+	if strings.TrimSpace(opts.Target) != "" {
+		args = append(args, "-t", opts.Target)
+	}
+	// tmux takes a single command string. Use a conservative shell join.
+	cmdStr := shellJoin(argv)
+	args = append(args, cmdStr)
+    c := command("tmux", args...)
+    return c.Run()
+}
+
+// shellJoin quotes argv elements for safe use in a single shell command string.
+// It avoids interpretation by wrapping in single quotes and escaping embedded single quotes.
+func shellJoin(argv []string) string {
+	out := make([]string, 0, len(argv))
+	for _, a := range argv {
+		if a == "" {
+			out = append(out, "''")
+			continue
+		}
+		if isSafeBare(a) {
+			out = append(out, a)
+			continue
+		}
+		// single-quote wrapping with escaped single quotes
+		// ' => '\'' (close, escaped quote, reopen)
+		esc := strings.ReplaceAll(a, "'", "'\\''")
+		out = append(out, "'"+esc+"'")
+	}
+	return strings.Join(out, " ")
+}
+
+// isSafeBare returns true if a contains only safe characters for bare words.
+func isSafeBare(s string) bool {
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		if (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9') || b == '-' || b == '_' || b == '.' || b == '/' || b == ':' {
+			continue
+		}
+		return false
+	}
+	return true
+}