/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2023 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use std::collections::HashMap;

use crypto_box::{
    aead::{Aead, AeadCore},
    SalsaBox,
};
use rand::rngs::OsRng;

use crate::{
    settings::{ChannelInfo, ContactInfo},
    Privmsg,
};

/// The format we're using is nonce+ciphertext, where nonce is 24 bytes.
fn try_decrypt(salt_box: &SalsaBox, ciphertext: &str) -> Option<String> {
    let bytes = match bs58::decode(ciphertext).into_vec() {
        Ok(v) => v,
        Err(_) => return None,
    };

    if bytes.len() < 25 {
        return None
    }

    // Try extracting the nonce
    let nonce = match bytes[0..24].try_into() {
        Ok(v) => v,
        Err(_) => return None,
    };

    // Take the remaining ciphertext
    let message = &bytes[24..];

    // Try decrypting the message
    match salt_box.decrypt(nonce, message) {
        Ok(v) => Some(String::from_utf8_lossy(&v).to_string()),
        Err(_) => None,
    }
}

/// The format we're using is nonce+ciphertext, where nonce is 24 bytes.
pub fn encrypt(salt_box: &SalsaBox, plaintext: &str) -> String {
    let nonce = SalsaBox::generate_nonce(&mut OsRng);
    let mut ciphertext = salt_box.encrypt(&nonce, plaintext.as_bytes()).unwrap();

    let mut concat = vec![];
    concat.append(&mut nonce.as_slice().to_vec());
    concat.append(&mut ciphertext);

    bs58::encode(concat).into_string()
}

/// Decrypt PrivMsg target
pub fn decrypt_target(
    contact: &mut String,
    privmsg: &mut Privmsg,
    configured_chans: HashMap<String, ChannelInfo>,
    configured_contacts: HashMap<String, ContactInfo>,
) {
    for chan_name in configured_chans.keys() {
        let chan_info = configured_chans.get(chan_name).unwrap();
        if !chan_info.joined {
            continue
        }

        let salt_box = chan_info.salt_box.clone();

        if let Some(salt_box) = salt_box {
            let decrypted_target = try_decrypt(&salt_box, &privmsg.target);
            if decrypted_target.is_none() {
                continue
            }

            let target = decrypted_target.unwrap();
            if *chan_name == target {
                privmsg.target = target;
                return
            }
        }
    }

    for cnt_name in configured_contacts.keys() {
        let cnt_info = configured_contacts.get(cnt_name).unwrap();

        let salt_box = cnt_info.salt_box.clone();
        if let Some(salt_box) = salt_box {
            let decrypted_target = try_decrypt(&salt_box, &privmsg.target);
            if decrypted_target.is_none() {
                continue
            }

            let target = decrypted_target.unwrap();
            privmsg.target = target;
            *contact = cnt_name.into();
            return
        }
    }
}

/// Decrypt PrivMsg nickname and message
pub fn decrypt_privmsg(salt_box: &SalsaBox, privmsg: &mut Privmsg) {
    let decrypted_nick = try_decrypt(&salt_box.clone(), &privmsg.nickname);
    let decrypted_msg = try_decrypt(&salt_box.clone(), &privmsg.message);

    if decrypted_nick.is_none() && decrypted_msg.is_none() {
        return
    }
    privmsg.nickname = decrypted_nick.unwrap();
    privmsg.message = decrypted_msg.unwrap();
}

/// Encrypt PrivMsg
pub fn encrypt_privmsg(salt_box: &SalsaBox, privmsg: &mut Privmsg) {
    privmsg.nickname = encrypt(salt_box, &privmsg.nickname);
    privmsg.target = encrypt(salt_box, &privmsg.target);
    privmsg.message = encrypt(salt_box, &privmsg.message);
}