cli: split banger.go god file into focused files

Pure code motion — banger.go 3508→240 LOC, same-package
decomposition keeps all identifiers visible without export changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/cli/daemon_lifecycle.go

@@ -0,0 +1,138 @@
+package cli
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+	"time"
+
+	"banger/internal/api"
+	"banger/internal/config"
+	"banger/internal/model"
+	"banger/internal/paths"
+	"banger/internal/rpc"
+)
+
+// ensureDaemon pings the socket; on miss it auto-starts bangerd, on
+// version mismatch it restarts. Every CLI command that needs to talk
+// to the daemon routes through here.
+func ensureDaemon(ctx context.Context) (paths.Layout, model.DaemonConfig, error) {
+	layout, err := paths.Resolve()
+	if err != nil {
+		return paths.Layout{}, model.DaemonConfig{}, err
+	}
+	cfg, err := config.Load(layout)
+	if err != nil {
+		return paths.Layout{}, model.DaemonConfig{}, err
+	}
+	if ping, err := daemonPingFunc(ctx, layout.SocketPath); err == nil {
+		if daemonOutdated(ping.PID) {
+			if err := restartDaemon(ctx, layout, ping.PID); err != nil {
+				return paths.Layout{}, model.DaemonConfig{}, err
+			}
+			return layout, cfg, nil
+		}
+		return layout, cfg, nil
+	}
+	if err := startDaemon(ctx, layout); err != nil {
+		return paths.Layout{}, model.DaemonConfig{}, err
+	}
+	return layout, cfg, nil
+}
+
+// daemonOutdated reports whether the running daemon binary differs
+// from the one on disk — useful after `make install` when the user's
+// session still holds a handle to an old daemon. os.SameFile compares
+// inode + dev, so a fresh binary at the same path registers as
+// different.
+func daemonOutdated(pid int) bool {
+	if pid <= 0 {
+		return false
+	}
+	daemonBin, err := bangerdPathFunc()
+	if err != nil {
+		return false
+	}
+	currentInfo, err := os.Stat(daemonBin)
+	if err != nil {
+		return false
+	}
+	runningInfo, err := os.Stat(daemonExePath(pid))
+	if err != nil {
+		return false
+	}
+	return !os.SameFile(currentInfo, runningInfo)
+}
+
+func restartDaemon(ctx context.Context, layout paths.Layout, pid int) error {
+	stopCtx, cancel := context.WithTimeout(ctx, 2*time.Second)
+	defer cancel()
+
+	_, _ = rpc.Call[api.ShutdownResult](stopCtx, layout.SocketPath, "shutdown", api.Empty{})
+	if waitForPIDExit(pid, 2*time.Second) {
+		return startDaemon(ctx, layout)
+	}
+	if proc, err := os.FindProcess(pid); err == nil {
+		_ = proc.Signal(syscall.SIGTERM)
+	}
+	if !waitForPIDExit(pid, 2*time.Second) {
+		return fmt.Errorf("timed out restarting stale daemon pid %d", pid)
+	}
+	return startDaemon(ctx, layout)
+}
+
+func waitForPIDExit(pid int, timeout time.Duration) bool {
+	deadline := time.Now().Add(timeout)
+	for time.Now().Before(deadline) {
+		if !pidRunning(pid) {
+			return true
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+	return !pidRunning(pid)
+}
+
+func pidRunning(pid int) bool {
+	if pid <= 0 {
+		return false
+	}
+	proc, err := os.FindProcess(pid)
+	if err != nil {
+		return false
+	}
+	return proc.Signal(syscall.Signal(0)) == nil
+}
+
+func startDaemon(ctx context.Context, layout paths.Layout) error {
+	if err := paths.Ensure(layout); err != nil {
+		return err
+	}
+	logFile, err := os.OpenFile(layout.DaemonLog, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
+	if err != nil {
+		return err
+	}
+	defer logFile.Close()
+
+	daemonBin, err := paths.BangerdPath()
+	if err != nil {
+		return err
+	}
+	cmd := buildDaemonCommand(daemonBin)
+	cmd.Stdout = logFile
+	cmd.Stderr = logFile
+	cmd.Stdin = nil
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+	if err := rpc.WaitForSocket(layout.SocketPath, 5*time.Second); err != nil {
+		return fmt.Errorf("daemon failed to start; inspect %s: %w", layout.DaemonLog, err)
+	}
+	return nil
+}
+
+func buildDaemonCommand(daemonBin string) *exec.Cmd {
+	return exec.Command(daemonBin)
+}