package hvpnnode3

import (
	"errors"
	"fmt"
	"log/slog"
	"os"

	"github.com/google/uuid"
)

const UUID_PATH = "/etc/hvpn/uuid"
const CONFIG_PATH = "/etc/hvpn"
const UUIDV4_LEN = 16

// Gets or creates a UUID for this node
func InitNodeUUID() (*uuid.UUID, error) {

    // TODO: check and write to os.UserHomeDir() to avoid root
    _, err := os.Stat(UUID_PATH)
    if err != nil {
        if errors.Is(err, os.ErrNotExist) {
            slog.Info(UUID_PATH + " does not exist. Creating...")
            return createNodeUUID()
        }
    }

    slog.Debug("UUID: Reading UUID")
    f, err := os.Open(UUID_PATH)
    if err != nil {
        return nil, err
    }
    buffer := make([]byte, UUIDV4_LEN)
    n, err := f.Read(buffer)
    if err != nil {
        return nil, err
    }
    slog.Debug("UUID: Read " + fmt.Sprint(n) + "bytes" )

    uuid, err := uuid.FromBytes(buffer)
    return &uuid, err
}

func createNodeUUID() (*uuid.UUID, error) {
    uuid, err := uuid.NewRandom()
    if err != nil {
        return nil, err
    }

    err = os.MkdirAll(CONFIG_PATH, 0755)
    if err != nil {
        slog.Error(err.Error())
        slog.Warn("Could not create /etc/hvpn directory!")
        slog.Info("Proccedig without saving node UUID")
        return &uuid, nil
    }

    mode := os.O_RDWR | os.O_CREATE | os.O_EXCL
    f, err := os.OpenFile(UUID_PATH, mode, 0644)
    if err != nil {
        slog.Error(err.Error())
        slog.Warn("Could not open uuid file")
        slog.Info("Proccedig without saving node UUID")
        return &uuid, nil 
    }
    n, err := f.Write(uuid[:])
    if err != nil {
        slog.Error(err.Error())
        slog.Warn("Could not write to uuid file")
        slog.Info("Proccesing without saving node UUID")
        return &uuid, nil
    }
    slog.Debug("UUID: Wrote " + fmt.Sprint(n) + "bytes")
    return &uuid, nil  
}