package license

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/sha256"
    "encoding/base64"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "os/exec"
    "strings"
    "time"
)

var key = []byte("914a3f206e294edc96b79818ad61d768")

type License struct {
    ProductID string `json:"product_id"`
    UniqueID  string `json:"unique_id"`
    Expiry    string `json:"expiry"`
}

func decrypt(encryptedText string) (string, error) {
    cipherText, err := base64.StdEncoding.DecodeString(encryptedText)
    if err != nil {
        return "", err
    }
    block, err := aes.NewCipher(key)
    if err != nil {
        return "", err
    }
    cfb := cipher.NewCFBDecrypter(block, key[:aes.BlockSize])
    plaintext := make([]byte, len(cipherText))
    cfb.XORKeyStream(plaintext, cipherText)
    return string(plaintext), nil
}

func getMachineID() (string, error) {
    data, err := ioutil.ReadFile("/etc/machine-id")
    if err != nil {
        return "", err
    }
    return strings.TrimSpace(string(data)), nil
}

func getDiskUUIDs() (string, error) {
    output, err := exec.Command("blkid").Output()
    if err != nil {
        return "", err
    }
    return string(output), nil
}

func GetUniqueID() (string, error) {
    machineID, err := getMachineID()
    if err != nil {
        return "", err
    }
    diskUUIDs, err := getDiskUUIDs()
    if err != nil {
        return "", err
    }
    combinedID := machineID + diskUUIDs
    hash := sha256.Sum256([]byte(combinedID))
    return fmt.Sprintf("%x", hash), nil
}

func ValidateLicense(encryptedLicense string) (bool, error) {
    layout := "2006-01-02"
    now := time.Now()
    decrypted, err := decrypt(encryptedLicense)
    if err != nil {
        return false, err
    }
    var license License
    err = json.Unmarshal([]byte(decrypted), &license)
    if err != nil {
        return false, err
    }
    if license.ProductID != "rtp-app" {
        return false, err
    }
    date, err := time.Parse(layout, license.Expiry)
    if err != nil {
        return false, err
    }
    if date.Before(now) {
        return false, err
    }
    return true, nil
}