use std::convert::TryInto;

use rand::{thread_rng, SeedableRng, RngCore};
use rand_chacha::ChaCha20Rng;
use spiral_rs::{client::*, discrete_gaussian::*, util::*};
use wasm_bindgen::prelude::*;

const UUID_V4_LEN: usize = 36;

// console_log! macro
#[wasm_bindgen]
extern "C" {
    #[wasm_bindgen(js_namespace = console)]
    fn log(s: &str);
}
#[allow(unused_macros)]
macro_rules! console_log {
    ($($t:tt)*) => (log(&format_args!($($t)*).to_string()))
}

// Container class for a static lifetime Client
// Avoids a lifetime in the return signature of bound Rust functions
#[wasm_bindgen]
pub struct WrappedClient {
    client: &'static mut Client<'static, ChaCha20Rng>,
}

// Very simply test to ensure random generation is not obviously biased.
fn _dg_seems_okay() {
    let params = get_test_params();
    let mut rng = thread_rng();
    let mut dg = DiscreteGaussian::init(&params, &mut rng);
    let mut v = Vec::new();
    let trials = 10000;
    let mut sum = 0;
    for _ in 0..trials {
        let val = dg.sample();
        v.push(val);
        sum += val;
    }
    let mean = sum as f64 / trials as f64;
    let std_dev = params.noise_width / f64::sqrt(2f64 * std::f64::consts::PI);
    let std_dev_of_mean = std_dev / f64::sqrt(trials as f64);
    assert!(f64::abs(mean) < std_dev_of_mean * 5f64);
}

// Initializes a client; can optionally take in a set of parameters
#[wasm_bindgen]
pub fn initialize(json_params: Option<String>, seed: Box<[u8]>) -> WrappedClient {
    // spiral_rs::ntt::test::ntt_correct();
    let cfg = r#"
        {'n': 2,
        'nu_1': 10,
        'nu_2': 6,
        'p': 512,
        'q2_bits': 21,
        's_e': 85.83255142749422,
        't_gsw': 10,
        't_conv': 4,
        't_exp_left': 16,
        't_exp_right': 56,
        'instances': 11,
        'db_item_size': 100000 }
    "#;
    let mut cfg = cfg.replace("'", "\"");
    if json_params.is_some() {
        cfg = json_params.unwrap();
    }

    let seed_buf = (*seed).try_into().unwrap();

    let params = Box::leak(Box::new(params_from_json(&cfg)));
    let rng = Box::leak(Box::new(ChaCha20Rng::from_seed(seed_buf)));

    let client = Box::leak(Box::new(Client::init(params, rng)));

    WrappedClient { client }
}

#[wasm_bindgen]
pub fn generate_public_parameters(c: &mut WrappedClient) -> Box<[u8]> {
    let res = c.client.generate_keys().serialize().into_boxed_slice();

    // important to re-seed here; only query and public key are deterministic
    let mut rng = thread_rng();
    let mut new_seed = [0u8; 32];
    rng.fill_bytes(&mut new_seed);
    *c.client.get_rng() = ChaCha20Rng::from_seed(new_seed);
    res
}

#[wasm_bindgen]
pub fn generate_query(c: &mut WrappedClient, id: &str, idx_target: usize) -> Box<[u8]> {
    assert_eq!(id.len(), UUID_V4_LEN);
    let query = c.client.generate_query(idx_target);
    let mut query_buf = query.serialize();
    let mut full_query_buf = id.as_bytes().to_vec();
    full_query_buf.append(&mut query_buf);
    full_query_buf.into_boxed_slice()
}

#[wasm_bindgen]
pub fn decode_response(c: &mut WrappedClient, data: Box<[u8]>) -> Box<[u8]> {
    c.client.decode_response(&*data).into_boxed_slice()
}

#[cfg(test)]
mod test {
    use rand::{distributions::Standard, prelude::Distribution};

    use super::*;

    #[test]
    fn chacha_is_correct() {
        let mut rng1 = ChaCha20Rng::from_seed([1u8; 32]);
        let mut rng2 = ChaCha20Rng::from_seed([1u8; 32]);
        let val1: u64 = Standard.sample(&mut rng1);
        let val2: u64 = Standard.sample(&mut rng2);
        assert_eq!(val1, val2);
    }
}