package backup

import (
	"os"
	"strings"
	"time"
)

// R-897 (2026-10-07): after a host restart the agent binds each drive under /mnt/felhom-drives, and when the guest
// started after that first bind it NORMALIZES it once more (umount + mount, felhom-agent localapi/intermediary.go). A
// recovery-unit capture that ran in that second failed — `mkdir /mnt/felhom-drives/hdd_1/backups: permission
// denied` — and the operator got a backup failure for a healthy app. The kernel lane restarts boxes at night, so this
// would have come after every kernel step.
//
// The rule: for DriveWaitWindow after the controller starts, a capture for an app on a drive runs only once that
// drive's bind is LIVE in this process's mount namespace (the same signal the startup app gate uses,
// web/intermediary.go driveBindLive). A periodic refresh skips the app until then (it runs every 5 minutes anyway);
// a data run waits for it. After the window the capture runs whatever the bind says, and says so once at WARN. The
// agent's bind order is unchanged. Pinned by driveready_test.go.

// DriveWaitWindow is how long after the controller starts a capture waits for a drive's bind.
const DriveWaitWindow = 10 * time.Minute

const drivesParent = "/mnt/felhom-drives/"

// driveRootOf is "/mnt/felhom-drives/<name>" for a path under it, "" for any other path (the system-data SSD).
func driveRootOf(p string) string {
	if !strings.HasPrefix(p, drivesParent) {
		return ""
	}
	name := strings.SplitN(strings.TrimPrefix(p, drivesParent), "/", 2)[0]
	if name == "" {
		return ""
	}
	return drivesParent + name
}

// mountinfoHasTarget reports whether root is a mount target in this process's own mount namespace.
func mountinfoHasTarget(root string) bool {
	data, err := os.ReadFile("/proc/self/mountinfo")
	if err != nil {
		return false
	}
	for _, line := range strings.Split(string(data), "\n") {
		if f := strings.Fields(line); len(f) >= 5 && f[4] == root {
			return true
		}
	}
	return false
}

func (m *Manager) now() time.Time {
	if m.nowFn != nil {
		return m.nowFn()
	}
	return time.Now()
}

// driveReady says whether a capture for an app at drivePath may run now (true outside the post-boot window, for a
// non-drive path, or once the bind is live). dataRun: wait (poll) for the bind until the window ends instead of
// skipping.
func (m *Manager) driveReady(drivePath string, dataRun bool) bool {
	root := driveRootOf(drivePath)
	if root == "" || m.startedAt.IsZero() {
		return true
	}
	live := m.driveLive
	if live == nil {
		live = mountinfoHasTarget
	}
	deadline := m.startedAt.Add(DriveWaitWindow)
	for {
		if live(root) {
			return true
		}
		if !m.now().Before(deadline) {
			m.driveMu.Lock()
			warned := m.driveWarned[root]
			if m.driveWarned == nil {
				m.driveWarned = map[string]bool{}
			}
			m.driveWarned[root] = true
			m.driveMu.Unlock()
			if !warned {
				m.logger.Printf("[WARN] [backup] %s is still not bound live %s after the controller started — capturing anyway (R-897)",
					root, DriveWaitWindow)
			}
			return true
		}
		if !dataRun {
			if m.isDebug() {
				m.logger.Printf("[DEBUG] [backup] recovery-unit refresh waits for %s — its bind is not live yet after the start (R-897)", root)
			}
			return false
		}
		sleep := m.driveWaitPoll
		if sleep == nil {
			sleep = time.Sleep
		}
		m.logger.Printf("[INFO] [backup] waiting for %s to be bound live before the capture (post-boot, R-897)", root)
		sleep(5 * time.Second)
	}
}