use rand_chacha::rand_core::SeedableRng;
use rand_core::RngCore;
use rand_chacha::{ChaCha8Rng};

const MAXF64: f64 = 9007199254740992.0;

pub struct Source{
    source:ChaCha8Rng,
}

impl Source{
    pub fn new(seed: [u8;32]) -> Source{
        Source{source:ChaCha8Rng::from_seed(seed)}
    }

    pub fn new_seed(&mut self) -> [u8;32]{
        let mut seed: [u8; 32] = [0u8;32];
        self.source.fill_bytes(&mut seed);
        seed
    }

    #[inline(always)]
    pub fn next_u64(&mut self) -> u64{
        self.source.next_u64()
    }

    #[inline(always)]
    pub fn next_u64n(&mut self, max: u64, mask: u64) -> u64{
        let mut x: u64 = self.next_u64() & mask;
        while x >= max{
            x = self.next_u64() & mask;
        }
        x
    }

    #[inline(always)]
    pub fn next_f64(&mut self, min: f64, max: f64) -> f64{
        min + ((self.next_u64()<<11>>11) as f64)/MAXF64 * (max-min)
    }

    #[inline(always)]
    pub fn fill_bytes(&mut self, bytes: &mut [u8]){
        self.source.fill_bytes(bytes)
    }
}