package main

import (
	"fmt"
	"log"

	"github.com/status-im/doubleratchet"
)

func main() {
	// The shared key both parties have already agreed upon before the communication.
	sk := [32]byte{
		0xeb, 0x8, 0x10, 0x7c, 0x33, 0x54, 0x0, 0x20,
		0xe9, 0x4f, 0x6c, 0x84, 0xe4, 0x39, 0x50, 0x5a,
		0x2f, 0x60, 0xbe, 0x81, 0xa, 0x78, 0x8b, 0xeb,
		0x1e, 0x2c, 0x9, 0x8d, 0x4b, 0x4d, 0xc1, 0x40,
	}

	// Diffie-Hellman key pair generated by one of the parties during key exchange or
	// by any other means. The public key MUST be sent to another party for initialization
	// before the communication begins.
	keyPair, err := doubleratchet.DefaultCrypto{}.GenerateDH()
	if err != nil {
		log.Fatal(err)
	}

	// Bob MUST be created with the shared secret and a DH key pair.
	bob, err := doubleratchet.New([]byte("bob-session-id"), sk, keyPair, nil)
	if err != nil {
		log.Fatal(err)
	}

	// Alice MUST be created with the shared secret and Bob's public key.
	alice, err := doubleratchet.NewWithRemoteKey([]byte("alice-session-id"), sk, keyPair.PublicKey(), nil)
	if err != nil {
		log.Fatal(err)
	}

	// Alice can now encrypt messages under the Double Ratchet session.
	m, err := alice.RatchetEncrypt([]byte("Hi Bob!"), nil)

	if err != nil {
		log.Fatal(err)
	}

	// Which Bob can decrypt.
	plaintext, err := bob.RatchetDecrypt(m, nil)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(string(plaintext))
}

doubleratchet.New(
    sk, keyPair,
    
    // Your own cryptography supplement implementing doubleratchet.Crypto.
    WithCrypto(c),
    
    // Custom storage for skipped keys implementing doubleratchet.KeysStorage.
    WithKeysStorage(ks),
    
    // The maximum number of skipped keys. Error will be raised in an attempt to store more keys
    // in a single chain while decrypting.
    WithMaxSkip(1200),
    
    // The number of Diffie-Hellman ratchet steps skipped keys will be stored.
    WithMaxKeep(90),
)