//go:build linux

package storage

import (
	"encoding/json"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"gitea.dooplex.hu/admin/felhom-controller/internal/util"
)

// lsblkOutput matches the top-level JSON from lsblk -J.
type lsblkOutput struct {
	BlockDevices []lsblkDevice `json:"blockdevices"`
}

// lsblkDevice is the raw JSON structure from lsblk.
type lsblkDevice struct {
	Name       string        `json:"name"`
	Path       string        `json:"path"`
	Size       interface{}   `json:"size"` // may be float64 or string
	Type       string        `json:"type"`
	FSType     *string       `json:"fstype"`
	MountPoint *string       `json:"mountpoint"`
	Model      *string       `json:"model"`
	RM         interface{}   `json:"rm"` // removable: bool or "0"/"1"
	Children   []lsblkDevice `json:"children"`
}

func (d *lsblkDevice) sizeBytes() int64 {
	switch v := d.Size.(type) {
	case float64:
		return int64(v)
	case string:
		// M3: lsblk can return size as a string on some kernel versions.
		n, _ := strconv.ParseUint(v, 10, 64)
		return int64(n)
	}
	return 0
}

func (d *lsblkDevice) sizeHuman() string {
	bytes := d.sizeBytes()
	const (
		GB = 1024 * 1024 * 1024
		TB = GB * 1024
	)
	switch {
	case bytes >= TB:
		return fmt.Sprintf("%.1f TB", float64(bytes)/float64(TB))
	case bytes >= GB:
		return fmt.Sprintf("%.1f GB", float64(bytes)/float64(GB))
	default:
		return fmt.Sprintf("%d MB", bytes/(1024*1024))
	}
}

func (d *lsblkDevice) isRemovable() bool {
	switch v := d.RM.(type) {
	case bool:
		return v
	case float64:
		return v != 0
	case string:
		return v == "1" || strings.EqualFold(v, "true")
	}
	return false
}

func (d *lsblkDevice) fsType() string {
	if d.FSType != nil {
		return *d.FSType
	}
	return ""
}

func (d *lsblkDevice) mountPoint() string {
	if d.MountPoint != nil {
		return *d.MountPoint
	}
	return ""
}

func (d *lsblkDevice) model() string {
	if d.Model != nil {
		return strings.TrimSpace(*d.Model)
	}
	return ""
}

// getSystemDiskNames returns the set of parent disk names (e.g., "sda")
// that contain system partitions (/, /boot, /boot/efi, swap).
// It reads the host's fstab (mounted at /host-fstab in the container)
// and resolves UUIDs to device paths via blkid.
func getSystemDiskNames() map[string]bool {
	systemDisks := map[string]bool{}

	// Step 1: Find and parse fstab
	fstabPath := "/host-fstab"
	if _, err := os.Stat(fstabPath); err != nil {
		fstabPath = "/etc/fstab"
	}

	data, err := os.ReadFile(fstabPath)
	if err != nil {
		return systemDisks
	}

	systemMounts := map[string]bool{"/": true, "/boot": true, "/boot/efi": true}

	var systemUUIDs []string
	var systemDevices []string

	for _, line := range strings.Split(string(data), "\n") {
		line = strings.TrimSpace(line)
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		fields := strings.Fields(line)
		if len(fields) < 3 {
			continue
		}
		source := fields[0]
		mountPoint := fields[1]
		fsType := fields[2]

		if !systemMounts[mountPoint] && fsType != "swap" {
			continue
		}

		if strings.HasPrefix(source, "UUID=") {
			systemUUIDs = append(systemUUIDs, strings.TrimPrefix(source, "UUID="))
		} else if strings.HasPrefix(source, "/dev/") {
			systemDevices = append(systemDevices, source)
		}
	}

	// Step 2: Resolve UUIDs to device paths via blkid
	for _, uuid := range systemUUIDs {
		out, err := exec.Command("blkid", "-U", uuid).Output()
		if err == nil {
			devPath := strings.TrimSpace(string(out))
			if devPath != "" {
				systemDevices = append(systemDevices, devPath)
			}
		}
	}

	// Step 3: Extract parent disk names from device paths
	for _, devPath := range systemDevices {
		diskName := partitionToParentDisk(devPath)
		if diskName != "" {
			systemDisks[diskName] = true
		}
	}

	return systemDisks
}

// partitionToParentDisk extracts the parent disk name from a partition device path.
// "/dev/sda2" → "sda", "/dev/nvme0n1p2" → "nvme0n1", "/dev/mmcblk0p1" → "mmcblk0"
func partitionToParentDisk(devPath string) string {
	name := filepath.Base(devPath)

	// H10: Handle mmcblk0p1 and nvme0n1p1 patterns where 'p' separates disk# from partition#.
	// The prefix before 'p' must end with a digit (e.g., mmcblk0, nvme0n1) to be a disk number.
	if idx := strings.LastIndex(name, "p"); idx > 0 {
		prefix := name[:idx]
		suffix := name[idx+1:]
		if len(suffix) > 0 && suffix[0] >= '0' && suffix[0] <= '9' &&
			len(prefix) > 0 && prefix[len(prefix)-1] >= '0' && prefix[len(prefix)-1] <= '9' {
			// Verify suffix is all digits (partition number, not part of device name)
			allDigits := true
			for _, c := range suffix {
				if c < '0' || c > '9' {
					allDigits = false
					break
				}
			}
			if allDigits {
				return prefix // e.g., mmcblk0, nvme0n1
			}
		}
	}

	// Standard: sda2 → sda, sdb1 → sdb
	return strings.TrimRight(name, "0123456789")
}

// enrichWithBlkid fills in missing FSType, UUID, and Label on partitions using blkid.
// Probes each partition individually via /host-dev (Docker overrides /dev with its own
// tmpfs, so the host block devices are accessible at /host-dev instead).
func enrichWithBlkid(disks []BlockDevice, logger *log.Logger, debug bool) {
	dbg := func(format string, args ...interface{}) {
		if debug && logger != nil {
			logger.Printf("[DEBUG] [storage] enrichWithBlkid: "+format, args...)
		}
	}

	for i := range disks {
		for j := range disks[i].Partitions {
			p := &disks[i].Partitions[j]
			hostPath := HostDevicePath(p.Path) // "/dev/sdb1" → "/host-dev/sdb1"

			if p.FSType == "" {
				if out, err := exec.Command("blkid", "-o", "value", "-s", "TYPE", hostPath).Output(); err == nil {
					p.FSType = strings.TrimSpace(string(out))
					dbg("blkid TYPE %s → %q", hostPath, p.FSType)
				} else {
					dbg("blkid TYPE %s failed: %v", hostPath, err)
				}
			}
			if p.UUID == "" {
				if out, err := exec.Command("blkid", "-o", "value", "-s", "UUID", hostPath).Output(); err == nil {
					p.UUID = strings.TrimSpace(string(out))
					dbg("blkid UUID %s → %q", hostPath, p.UUID)
				} else {
					dbg("blkid UUID %s failed: %v", hostPath, err)
				}
			}
			if p.Label == "" {
				if out, err := exec.Command("blkid", "-o", "value", "-s", "LABEL", hostPath).Output(); err == nil {
					p.Label = strings.TrimSpace(string(out))
					dbg("blkid LABEL %s → %q", hostPath, p.Label)
				} else {
					dbg("blkid LABEL %s failed: %v", hostPath, err)
				}
			}
		}
	}
}

// ScanDisks detects all block devices and classifies them into
// available (not mounted, not system) and system/mounted disks.
func ScanDisks(logger *log.Logger, debug bool) (*ScanResult, error) {
	dbg := func(format string, args ...interface{}) {
		if debug && logger != nil {
			logger.Printf("[DEBUG] [storage] ScanDisks: "+format, args...)
		}
	}

	if logger != nil {
		logger.Printf("[INFO] [storage] Scanning disks")
	}
	dbg("starting disk scan")
	scanStart := time.Now()

	out, err := exec.Command(
		"lsblk", "-J", "-b",
		"-o", "NAME,PATH,SIZE,TYPE,FSTYPE,MOUNTPOINT,MODEL,RM",
	).Output()
	if err != nil {
		return nil, fmt.Errorf("lsblk failed: %w", err)
	}

	dbg("raw lsblk JSON: %s", util.TruncateStr(string(out), 500))

	var parsed lsblkOutput
	if err := json.Unmarshal(out, &parsed); err != nil {
		return nil, fmt.Errorf("lsblk JSON parse failed: %w", err)
	}

	dbg("lsblk returned %d block devices", len(parsed.BlockDevices))

	// Get system disk names from host fstab (works correctly inside container)
	systemDiskNames := getSystemDiskNames()

	result := &ScanResult{}

	for _, dev := range parsed.BlockDevices {
		if dev.Type != "disk" {
			continue
		}

		bd := BlockDevice{
			Name:      dev.Name,
			Path:      dev.Path,
			Size:      dev.sizeHuman(),
			SizeBytes: dev.sizeBytes(),
			Model:     dev.model(),
			Type:      dev.Type,
			Removable: dev.isRemovable(),
		}
		if bd.Path == "" {
			bd.Path = "/dev/" + bd.Name
		}

		anyMounted := false
		for _, child := range dev.Children {
			if child.Type != "part" && child.Type != "lvm" && child.Type != "crypt" {
				continue
			}
			part := Partition{
				Name:       child.Name,
				Path:       child.Path,
				Size:       child.sizeHuman(),
				SizeBytes:  child.sizeBytes(),
				FSType:     child.fsType(),
				MountPoint: child.mountPoint(),
			}
			if part.Path == "" {
				part.Path = "/dev/" + part.Name
			}
			bd.Partitions = append(bd.Partitions, part)
			if part.MountPoint != "" {
				anyMounted = true
			}
		}

		// Also check if the disk itself is directly mounted (no partition table)
		if dev.mountPoint() != "" {
			anyMounted = true
		}

		isSystem := systemDiskNames[dev.Name]
		bd.Mounted = anyMounted || isSystem

		classification := "available"
		if isSystem || anyMounted {
			classification = "system"
			result.SystemDisks = append(result.SystemDisks, bd)
		} else {
			result.AvailableDisks = append(result.AvailableDisks, bd)
		}

		dbg("disk %s: model=%q size=%s partitions=%d removable=%v classification=%s",
			bd.Name, bd.Model, bd.Size, len(bd.Partitions), bd.Removable, classification)

		for _, p := range bd.Partitions {
			dbg("  partition %s: fstype=%q mountpoint=%q size=%s", p.Name, p.FSType, p.MountPoint, p.Size)
		}
	}

	dbg("classification result: %d available, %d system", len(result.AvailableDisks), len(result.SystemDisks))

	// Enrich FSType, UUID, Label from blkid (lsblk can't probe fstype in container)
	enrichWithBlkid(result.AvailableDisks, logger, debug)
	enrichWithBlkid(result.SystemDisks, logger, debug)

	if logger != nil {
		logger.Printf("[INFO] [storage] Found %d disks", len(result.AvailableDisks)+len(result.SystemDisks))
	}
	dbg("disk scan completed in %s", time.Since(scanStart).Round(time.Millisecond))

	return result, nil
}