package disk

import (
	"errors"
	"os"
	"path/filepath"
	"strings"
	"syscall"

	"github.com/google/uuid"
)

type DiskState string

const (
	DiskAbsent  DiskState = "absent"
	DiskForeign DiskState = "foreign"
	DiskKnown   DiskState = "known"
)

type DiskInfo struct {
	State      DiskState `json:"state"`
	DiskID     string    `json:"disk_id"`
	TotalBytes int64     `json:"total_bytes"`
	FreeBytes  int64     `json:"free_bytes"`
	MountPath  string    `json:"mount_path"`
}

const markerDir = ".jukebox"
const idFile = "disk.id"

func Probe(mountPath string) (DiskInfo, error) {
	info := DiskInfo{MountPath: mountPath, State: DiskAbsent}

	entries, err := os.ReadDir(mountPath)
	if err != nil || len(entries) == 0 {
		return info, nil
	}

	total, free, err := DiskUsage(mountPath)
	if err != nil {
		return info, nil
	}
	info.TotalBytes = total
	info.FreeBytes = free

	idPath := filepath.Join(mountPath, markerDir, idFile)
	data, err := os.ReadFile(idPath)
	if errors.Is(err, os.ErrNotExist) {
		info.State = DiskForeign
		return info, nil
	}
	if err != nil {
		info.State = DiskForeign
		return info, nil
	}

	info.DiskID = strings.TrimSpace(string(data))
	info.State = DiskKnown
	return info, nil
}

func InitDisk(mountPath string) (string, error) {
	dir := filepath.Join(mountPath, markerDir)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", err
	}
	id := uuid.New().String()
	idPath := filepath.Join(dir, idFile)
	if err := os.WriteFile(idPath, []byte(id), 0o644); err != nil {
		return "", err
	}
	return id, nil
}

func DBPath(mountPath string) string {
	return filepath.Join(mountPath, markerDir, "history.db")
}

func DiskUsage(mountPath string) (total, free int64, err error) {
	var stat syscall.Statfs_t
	if err = syscall.Statfs(mountPath, &stat); err != nil {
		return 0, 0, err
	}
	total = int64(stat.Blocks) * int64(stat.Bsize)
	free = int64(stat.Bavail) * int64(stat.Bsize)
	return total, free, nil
}