use std::io::Write;
use std::{fs::OpenOptions, path::Path};

use serde::Serialize;
use x25519_dalek::{PublicKey, StaticSecret};

#[derive(Serialize)]
pub struct Keypair {
    sk: Vec<u8>,
    pk: Vec<u8>,
}

fn generate_keypair() -> Keypair {
    let sk = StaticSecret::random();
    let pk = PublicKey::from(&sk);

    Keypair {
        sk: sk.as_bytes().to_vec(),
        pk: pk.as_bytes().to_vec(),
    }
}

pub fn generate_keys_to_file(
    pks_path: impl AsRef<Path>,
    sks_path: impl AsRef<Path>,
    num: usize,
) -> std::io::Result<()> {
    let mut pks_file = OpenOptions::new()
        .write(true)
        .append(true)
        .create(true)
        .open(pks_path)?;

    let mut sks_file = OpenOptions::new()
        .write(true)
        .append(true)
        .create(true)
        .open(sks_path)?;

    for _ in 0..num {
        let kp = generate_keypair();

        writeln!(pks_file, "{}", serde_json::to_string(&kp.pk)?)?;
        writeln!(sks_file, "{}", serde_json::to_string(&kp.sk)?)?;
    }

    Ok(())
}