package storage

import (
	"path/filepath"
	"regexp"
	"strings"

	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
)

// Device ROLE classification — the protection tier the AGENT assigns a storage/device by its OWN
// inspection (the PVE storage view + the host mount/topology reads it already gathers), NEVER from
// the controller's or the hub's claim. This is the storage analog of classify.go's data-bearing
// verdict: "provenance is agent-internal, never populated from an external input, else a compromised
// hub could relabel a protected device to walk the gate."
//
// The tier decides who may authorize a destructive wipe of the device:
//   - system    : the appliance's OS/boot/EFI/guest-rootfs storage. Operator-signature ONLY.
//   - backup    : the backup safety-net (PBS). Operator-signature ONLY (wiping it destroys the net).
//   - user-data : a customer external data drive — already within the controller's blast radius
//     (it bind-mounts /mnt), so a customer informed-confirmation may authorize a wipe.
//
// On ANY ambiguity the agent defaults to the MOST-PROTECTED role (system) — consistent with the
// destructive-on-ambiguity invariant: an unrecognized device is treated as protected, never silently
// user-data.
type DeviceRole string

const (
	RoleSystem   DeviceRole = "system"
	RoleBackup   DeviceRole = "backup"
	RoleUserData DeviceRole = "user-data"
)

// reWholeDisk matches a whole raw disk path (no partition suffix): /dev/sda, /dev/vdb, /dev/nvme0n1.
var reWholeDisk = regexp.MustCompile(`^/dev/(?:sd|hd|vd)[a-z]+$|^/dev/nvme[0-9]+n[0-9]+$`)

// systemMountPoints are the host mountpoints whose backing whole-disk is, by definition, the OS /
// system disk. A mounted ESP (/boot/efi) pins the OS disk directly; an LVM/device-mapper root is
// traced to its physical parents by the root-free sysfs slaves/ walk (v0.87.0 — before that, a
// legacy-boot host with no mounted ESP resolved NOTHING and the all-system fail-safe killed the
// drive wizard permanently, IA finding 2).
var systemMountPoints = map[string]bool{"/": true, "/boot": true, "/boot/efi": true}

// SystemDisks resolves the set of whole-disk device paths that host the OS (the disks backing /,
// /boot and /boot/efi). Virtual backing devices (device-mapper/LVM, md-raid — the legacy-boot
// common case where / sits on /dev/mapper/pve-root and no ESP is mounted) are walked recursively
// through the sysfs slaves/ chain down to their physical parent disks (operator ruling
// 2026-07-13: walk topology, never VG names). ok=false ONLY when the topology could not be fully
// grounded — no system mountpoint found, or ANY system mount whose backing device the walk could
// not resolve to physical disks — and callers then treat every candidate as system (most
// protected). That all-system fail-safe is back to being the ERROR case, not the legacy-boot
// common case. Root-free: mount table + /dev symlinks + world-readable sysfs only.
func SystemDisks(host HostReader) (set map[string]bool, ok bool) {
	if host == nil {
		return nil, false
	}
	mounts, err := host.Mounts()
	if err != nil {
		return nil, false
	}
	set = map[string]bool{}
	for _, m := range mounts {
		if !systemMountPoints[cleanMountPath(m.MountPoint)] {
			continue
		}
		disks, dok := physicalDisksOf(host, m.Device)
		if !dok {
			// A system mount we cannot ground in physical disks — the WHOLE resolution is
			// undeterminable. Never return a partial set as ok: a root-backing disk missing
			// from the set is exactly the catastrophic direction (a system disk offered as
			// a wizard candidate).
			return nil, false
		}
		for _, d := range disks {
			set[d] = true
		}
	}
	return set, len(set) > 0
}

// physicalDisksOf resolves a mounted device to the PHYSICAL whole disks backing it. Plain
// disks/partitions resolve directly (wholeDiskOf); a virtual device (dm-*, md*) is walked via
// its sysfs slaves. ok=false when the device cannot be grounded (network/dataset sources,
// unknown names, or any unresolvable slave branch).
func physicalDisksOf(host HostReader, device string) ([]string, bool) {
	if device == "" {
		return nil, false
	}
	dev := device
	if resolved, err := filepath.EvalSymlinks(device); err == nil {
		dev = resolved // canonicalize /dev/mapper/pve-root → /dev/dm-1, by-uuid links, …
	}
	if wd, wok := wholeDiskOf(dev); wok {
		return []string{wd}, true // already a raw disk or a recognizable partition
	}
	if !strings.HasPrefix(dev, "/dev/") {
		return nil, false // ZFS dataset, NFS, overlay, … — not a block topology we can walk
	}
	return walkSlaves(host, filepath.Base(dev), map[string]bool{})
}

// walkSlaves recursively resolves a VIRTUAL block device name (dm-*, md*) to physical whole
// disks via /sys/block/<name>/slaves. Per-branch conservatism (operator ruling): ANY slave that
// cannot be resolved — a dangling entry, an unrecognizable name, a virtual device with no
// listable slaves — fails the WHOLE walk. The candidate/protected verdict must never rest on a
// partially-understood topology. visited doubles as the cycle/degenerate-depth guard.
func walkSlaves(host HostReader, name string, visited map[string]bool) ([]string, bool) {
	if name == "" || visited[name] || len(visited) > 32 {
		return nil, false
	}
	visited[name] = true
	slaves, hasDir := host.BlockSlaves(name)
	if !hasDir || len(slaves) == 0 {
		// No /sys/block entry (not a whole device) or nothing beneath a supposed virtual
		// device — either way this branch cannot be grounded.
		return nil, false
	}
	var out []string
	for _, s := range slaves {
		if wd, wok := wholeDiskOf("/dev/" + s); wok {
			out = append(out, wd) // a physical disk or a partition of one (sda3 → /dev/sda)
			continue
		}
		sub, sok := walkSlaves(host, s, visited)
		if !sok {
			return nil, false
		}
		out = append(out, sub...)
	}
	return out, true
}

// wholeDiskOf maps a device path (a partition, a whole disk, or a /dev/disk/by-* symlink) to its
// whole-disk /dev path. ok=false when the result is not a recognizable raw disk (device-mapper / LVM
// / network) — the caller then treats the topology as undeterminable (→ most-protected).
func wholeDiskOf(device string) (string, bool) {
	if device == "" {
		return "", false
	}
	dev := device
	if resolved, err := filepath.EvalSymlinks(device); err == nil {
		dev = resolved // canonicalize /dev/disk/by-uuid/… → /dev/sdXN
	}
	if m := reNVMePart.FindStringSubmatch(dev); m != nil {
		return m[1], true // /dev/nvme0n1p2 → /dev/nvme0n1
	}
	if m := reSDPart.FindStringSubmatch(dev); m != nil {
		return m[1], true // /dev/sdb1 → /dev/sdb
	}
	if reWholeDisk.MatchString(dev) {
		return dev, true // already a whole disk
	}
	return "", false // /dev/mapper/*, network, unrecognized → undeterminable
}

// isSystemBacked reports whether device's whole-disk is an OS/system disk. It FAILS SAFE: any
// ambiguity (system set unknown, or the device's whole-disk unrecognizable) returns true (system).
func isSystemBacked(device string, sysDisks map[string]bool, sysKnown bool) bool {
	if !sysKnown {
		return true // can't determine the system disks → treat as system (most protected)
	}
	wd, ok := wholeDiskOf(device)
	if !ok {
		return true // unrecognizable device topology → most protected
	}
	return sysDisks[wd]
}

// RoleForStorage classifies a storage TARGET (from the agent's storage view) into its protection
// tier. typ is the reported storage type; backingDevice is its resolved block device ("" for
// network/lvm/dir-on-root). sysDisks/sysKnown come from SystemDisks (resolved once per request).
func RoleForStorage(typ, backingDevice string, sysDisks map[string]bool, sysKnown bool) DeviceRole {
	switch typ {
	case hub.StorageTypePBS:
		return RoleBackup // the backup safety-net — protected
	case hub.StorageTypeUSB, hub.StorageTypeLocalDir:
		// A removable/extra dir storage is user-data ONLY when it has its OWN block device that is
		// NOT part of the system disk. No device (a dir on the root fs) or a system-disk-backed dir
		// → system. This is exactly "local-dir/usb on a non-root external device → user-data".
		if backingDevice == "" {
			return RoleSystem
		}
		if isSystemBacked(backingDevice, sysDisks, sysKnown) {
			return RoleSystem
		}
		return RoleUserData
	default:
		// local (builtin, on the root fs), lvmthin (local-lvm), lvm (thick), nfs, cifs, and anything
		// unrecognized → protected. Network shares are NOT customer-managed external drives in this
		// model and are not within the controller's blast radius, so protecting them is safe.
		return RoleSystem
	}
}

// RoleForRawDevice classifies a RAW block device (the format endpoint's target, which may not yet be
// a registered PVE storage — e.g. a fresh external disk in the init flow). It distinguishes system
// from user-data by system-disk membership. A raw /dev path is never a PBS datastore (those are
// network/API), so the backup tier is not reachable here — the storage-list view (RoleForStorage)
// tiers PBS. Defaults to system on ambiguity.
func RoleForRawDevice(device string, sysDisks map[string]bool, sysKnown bool) DeviceRole {
	if isSystemBacked(device, sysDisks, sysKnown) {
		return RoleSystem
	}
	return RoleUserData
}

// SameWholeDisk reports whether two device paths live on the same physical whole disk
// (e.g. /dev/sdb and /dev/sdb1). Storage targets carry BOTH granularities in practice (a dir
// storage's BackingDevice is the mounted PARTITION, a raw enrolled drive mounts the WHOLE disk),
// so containment checks must compare at whole-disk level — mirroring isSystemBacked. False when
// either side's whole-disk is unrecognizable (device-mapper/network) — callers fail safe.
func SameWholeDisk(a, b string) bool {
	wa, oka := wholeDiskOf(a)
	wb, okb := wholeDiskOf(b)
	return oka && okb && wa == wb
}