// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.

use deno_core::error::AnyError;
use deno_core::serde_json::json;
use deno_core::serde_json::Value;
use deno_core::OpState;
use deno_core::ZeroCopyBuf;
use rand::rngs::StdRng;
use rand::thread_rng;
use rand::Rng;
use rand::SeedableRng;

pub fn init(rt: &mut deno_core::JsRuntime, maybe_seed: Option<u64>) {
  if let Some(seed) = maybe_seed {
    let rng = StdRng::seed_from_u64(seed);
    let op_state = rt.op_state();
    let mut state = op_state.borrow_mut();
    state.put::<StdRng>(rng);
  }
  super::reg_json_sync(rt, "op_get_random_values", op_get_random_values);
}

fn op_get_random_values(
  state: &mut OpState,
  _args: Value,
  zero_copy: &mut [ZeroCopyBuf],
) -> Result<Value, AnyError> {
  assert_eq!(zero_copy.len(), 1);
  let maybe_seeded_rng = state.try_borrow_mut::<StdRng>();
  if let Some(seeded_rng) = maybe_seeded_rng {
    seeded_rng.fill(&mut *zero_copy[0]);
  } else {
    let mut rng = thread_rng();
    rng.fill(&mut *zero_copy[0]);
  }

  Ok(json!({}))
}