Synapse/ios/App/App/FileSync/Data+ChaChaPoly.swift

//
//  Data+ChaChaPoly.swift
//  Logseq
//
//  Created by Mono Wang on 5/20/R4.
//

import Foundation
import CryptoKit

extension Data {
    /**
     Encrypts current data using ChaChaPoly cipher.
     */
    public func sealChaChaPoly(with passphrase: String) -> Data? {
        guard let symmetricKey = try? SymmetricKey(passwordString: passphrase) else {
            return nil
        }

        let nonce = try? ChaChaPoly.Nonce(data: Data(repeating: 0x00, count: 12))
        if let encrypted = try? ChaChaPoly.seal(self, using: symmetricKey, nonce: nonce!).combined {
            var ret = Data(hexEncoded: "4c530031")
            ret?.append(encrypted)
            return ret
        }
        return nil
    }

    /**
     Decrypts current combined ChaChaPoly Selead box data (nonce || ciphertext || tag) using ChaChaPoly cipher.
     */
    public func openChaChaPoly(with passphrase: String) -> Data? {
        if self.count <= 4 {
            return nil
        }
        guard let symmetricKey = try? SymmetricKey(passwordString: passphrase) else {
            return nil
        }
        guard let chaChaPolySealedBox = try? ChaChaPoly.SealedBox(combined: self[4...]) else {
            return nil
        }

        return try? ChaChaPoly.open(chaChaPolySealedBox, using: symmetricKey)
    }
}