package main

import (
	"bufio"
	"os"
	"path/filepath"
	"strings"

	"go.wit.com/log"
)

func isBlockDeviceInUse(dev string) bool {
	base := filepath.Base(dev)

	// 1. Check /proc/mounts
	if isMounted(dev, base) {
		log.Info(dev, "dev is mounted (/proc/mounts)")
		return true
	}

	// 2. Check /proc/swaps
	if isSwap(dev) {
		log.Info(dev, "dev is used by swap (/proc/swaps)")
		return true
	}

	// 3. Check /proc/mdstat for RAID
	if isInRAID(base) {
		log.Info(dev, "dev is in software raid (/proc/mdstat)")
		return true
	}

	// 4. Check sysfs for device-mapper or LVM use
	if hasDMHolders(base) {
		log.Info(dev, "dev has lvm partitions")
		return true
	}

	log.Info(dev, "dev appears to be unused")
	return false
}

func isMounted(dev, base string) bool {
	f, err := os.Open("/proc/mounts")
	if err != nil {
		return false
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		if strings.HasPrefix(scanner.Text(), dev) || strings.Contains(scanner.Text(), base) {
			return true
		}
	}
	return false
}

func isSwap(dev string) bool {
	f, err := os.Open("/proc/swaps")
	if err != nil {
		return false
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		if strings.HasPrefix(scanner.Text(), dev) {
			return true
		}
	}
	return false
}

func isInRAID(base string) bool {
	f, err := os.Open("/proc/mdstat")
	if err != nil {
		return false
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		if strings.Contains(scanner.Text(), base) {
			return true
		}
	}
	return false
}

func hasDMHolders(base string) bool {
	path := filepath.Join("/sys/block", base, "holders")
	entries, err := os.ReadDir(path)
	return err == nil && len(entries) > 0
}