/// This module has wrappers for cryptography with RSA algorithms.
/// Its main structs - `PublicKey` and `Keys` implement all functions for key generation, signatures and asymmetric encryption
use alloc::vec::Vec;
use serde::{Deserialize, Serialize};
use rsa::{RsaPublicKey, RsaPrivateKey, PaddingScheme, PublicKey as RPK};
use rsa::errors::Result as RsaRes;
use rand::rngs::OsRng;

static KEY_LENGTH: usize = 2048;


/// Public key of a node
#[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
pub struct PublicKey {
    pub key: RsaPublicKey,
}

impl PublicKey {
    /// Check if the sign is valid for given data and key
    pub fn verify_sign(&self, data: &[u8], sign: &[u8]) -> bool {
        self.key.verify(PaddingScheme::PKCS1v15Sign { hash: None }, data, sign).is_ok()
    }

    /// Encrypt some data for a user with this public key
    pub fn encrypt_data(&self, data: &[u8]) -> RsaRes<Vec<u8>> {
        self.key.encrypt(&mut OsRng {}, PaddingScheme::PKCS1v15Encrypt, data)
    }
}

/// Key pair (public and secret) for a node, should be stored locally
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct Keys {
    public_key: RsaPublicKey,
    private_key: RsaPrivateKey,
}

impl Keys {
    /// Generate new random key
    pub fn generate() -> Self {
        let mut rng = OsRng;
        let private_key = RsaPrivateKey::new(&mut rng, KEY_LENGTH).expect("failed to generate a key");
        let public_key = RsaPublicKey::from(&private_key);
        Self {
            private_key,
            public_key,
        }
    }
}

impl Keys {
    /// Sign content using these keys
    pub fn sign(&self, content: &[u8]) -> RsaRes<Vec<u8>> {
        self.private_key.sign(PaddingScheme::PKCS1v15Sign { hash: None }, content)
    }

    /// Decrypt data
    pub fn decrypt_data(&self, data_encrypted: &[u8]) -> RsaRes<Vec<u8>> {
        self.private_key.decrypt(PaddingScheme::PKCS1v15Encrypt, data_encrypted)
    }

    /// Get public key
    pub fn get_public(&self) -> PublicKey {
        PublicKey { key: self.public_key.clone() }
    }
}

#[test]
fn test_encrypt() {
    let data = vec![0, 5, 8, 135, 67];
    let keys = Keys::generate();
    assert_eq!(
        keys.decrypt_data(&keys.get_public().encrypt_data(&data).unwrap()).unwrap(),
        data
    );
}

#[cfg(test)]
use alloc::vec;

#[test]
fn test_invalid_encrypt() {
    let data = vec![0, 5, 8, 135, 67];
    let keys_1 = Keys::generate();
    let keys_2 = Keys::generate();
    assert!(keys_2.decrypt_data(&keys_1.get_public().encrypt_data(&data).unwrap()).is_err());
}

#[test]
fn test_signing() {
    let data = vec![0, 5, 8, 135, 67];
    let keys = Keys::generate();
    assert!(keys.get_public().verify_sign(&data, &keys.sign(&data).unwrap()));
}

#[test]
fn test_invalid_signing() {
    let data = vec![0, 5, 8, 135, 67];
    let keys_1 = Keys::generate();
    let keys_2 = Keys::generate();
    assert!(!keys_2.get_public().verify_sign(&data, &keys_1.sign(&data).unwrap()));
}