/* Mersenne Twister 移植
 * Leonardone @ NEETSDKASU
 * BSD-2-Clause License
 */

//! メルセンヌツイスタをRustに移植してみたもの。正しく移植・実装できているかの保証はできません。  
//!
//! 移植元のライセンスに関してはソースコード下部に記載してあります。
//!
//! # Example
//!
//! ```
//! use mersenne_twister_rs::MersenneTwister;
//! let seed: u32 = 12_3456_7890;
//! let mut mt = Box::new(MersenneTwister::new(seed));
//! println!("u32 [0,0xffffffff] value: {}", mt.genrand_u32());
//! println!("i32 [0,0x7fffffff] value: {}", mt.genrand_i31());
//! println!("f64 [0,1) value: {}", mt.genrand_real2());
//! ```

const N: usize = 624;
const M: usize = 397;
const MATRIX_A: u32 = 0x9908b0df_u32;
const UPPER_MASK: u32 = 0x80000000_u32;
const LOWER_MASK: u32 = 0x7fffffff_u32;

/// デフォルトとして使用されるSEED。  
///
/// ※本番環境での使用は推奨しません。  
///
/// ※デフォルトSEEDは移植元には存在せず、私が追加したコードとなります。
pub const DEFAULT_SEED: u32 = 5489_u32;

static MAG01: [u32; 2] = [0x0_u32, MATRIX_A];

/// メルセンヌツイスタの実装の本体。
///
/// メルセンヌツイスタをRustに移植してみたもの。正しく移植・実装できているかの保証はできません。
///
/// 移植元のライセンスに関してはソースコード下部に記載してあります。  
///
/// ※フィールドに`[u32; 624]`の固定長配列を持つのでこれをスタックメモリ上で維持したくない場合は[Box]でヒープメモリを使用するなど適宜対処してください。  
///
/// ※初期化に用いるseedやkeyは保持しないため必要な場合は別途管理してください。  
///
/// # Example
///
/// ```
/// use mersenne_twister_rs::MersenneTwister;
/// let seed: u32 = 12_3456_7890;
/// let mut mt = Box::new(MersenneTwister::new(seed));
/// println!("u32 [0,0xffffffff] value: {}", mt.genrand_u32());
/// println!("i32 [0,0x7fffffff] value: {}", mt.genrand_i31());
/// println!("f64 [0,1) value: {}", mt.genrand_real2());
/// ```
#[derive(Debug, Clone)]
pub struct MersenneTwister {
    mt: [u32; N],
    mti: usize,
}

impl std::default::Default for MersenneTwister {
    /// [DEFAULT_SEED]で生成。  
    ///
    /// ※本番環境での使用は推奨しません。  
    ///
    /// ※[DEFAULT_SEED]は移植元には存在せず、私が追加したコードとなります。
    fn default() -> Self {
        MersenneTwister::new(DEFAULT_SEED)
    }
}

impl MersenneTwister {
    /// 指定のseedで生成。  
    ///
    /// seedにはu32型の任意の値を使用できます。  
    pub fn new(seed: u32) -> Self {
        let mut mt = MersenneTwister { mt: [0; N], mti: 0 };
        mt.init(seed);
        mt
    }

    /// 指定のkeyで生成。  
    ///
    /// keyにはu32型の任意の値を列挙したスライスを使用できます。  
    pub fn new_by_array(key: &[u32]) -> Self {
        let mut mt = MersenneTwister { mt: [0; N], mti: 0 };
        mt.init_by_array(key);
        mt
    }

    /// [DEFAULT_SEED]を用いて再初期化します。  
    ///
    /// ※本番環境での使用は推奨しません。  
    ///
    /// ※[DEFAULT_SEED]は移植元には存在せず、私が追加したコードとなります。
    pub fn init_by_default_seed(&mut self) {
        self.init(DEFAULT_SEED);
    }

    /* initializes mt[N] with a seed */
    /// initializes with a seed  
    ///
    /// 指定のseedを用いて再初期化します。
    ///
    /// seedにはu32型の任意の値を使用できます。
    pub fn init(&mut self, seed: u32) {
        self.mti = N;
        let mt = &mut self.mt;
        mt[0] = seed;
        for i in 1..N {
            mt[i] = 1812433253_u32
                .wrapping_mul(mt[i - 1] ^ (mt[i - 1] >> 30))
                .wrapping_add(i as u32);
        }
    }

    /* initialize by an array */
    /// initialize by an array  
    ///
    /// 指定のkeyを用いて再初期化します。
    ///
    /// keyにはu32型の任意の値を列挙したスライスを使用できます。
    pub fn init_by_array(&mut self, key: &[u32]) {
        self.init(19650218_u32);
        let mt = &mut self.mt;
        let mut i: usize = 1;
        let mut j: usize = 0;
        let mut k: usize = key.len().max(N);
        while k > 0 {
            mt[i] = (mt[i] ^ ((mt[i - 1] ^ (mt[i - 1] >> 30)).wrapping_mul(1664525_u32)))
                .wrapping_add(key[j])
                .wrapping_add(j as u32);
            i += 1;
            if i >= N {
                mt[0] = mt[N - 1];
                i = 1;
            }
            j += 1;
            if j >= key.len() {
                j = 0;
            }
            k -= 1;
        }
        k = N - 1;
        while k > 0 {
            mt[i] = (mt[i] ^ ((mt[i - 1] ^ (mt[i - 1] >> 30)).wrapping_mul(1566083941_u32)))
                .wrapping_sub(i as u32);
            i += 1;
            if i >= N {
                mt[0] = mt[N - 1];
                i = 1;
            }
            k -= 1;
        }
        mt[0] = 0x80000000_u32;
    }

    /* generates a random number on [0,0xffffffff]-interval */
    /// generates a random number on \[0,0xffffffff\]-interval  
    ///
    /// 0以上0xFFFF_FFFF以下のu32型の乱数を生成します。
    pub fn genrand_u32(&mut self) -> u32 {
        let mut y: u32;

        if self.mti >= N {
            /* generate N words at one time */
            self.mti = 0;
            let mt = &mut self.mt;
            let mut kk: usize = 0;
            while kk < N - M {
                y = (mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK);
                mt[kk] = mt[kk + M] ^ (y >> 1) ^ MAG01[(y & 0x1) as usize];
                kk += 1;
            }
            while kk < N - 1 {
                y = (mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK);
                mt[kk] = mt[kk + M - N] ^ (y >> 1) ^ MAG01[(y & 0x1) as usize];
                kk += 1;
            }
            y = (mt[N - 1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
            mt[N - 1] = mt[M - 1] ^ (y >> 1) ^ MAG01[(y & 0x1) as usize];
        }

        y = self.mt[self.mti];
        self.mti += 1;

        /* Tempering */
        y ^= y >> 11;
        y ^= (y << 7) & 0x9d2c5680_u32;
        y ^= (y << 15) & 0xefc60000_u32;
        y ^= y >> 18;

        y
    }

    /* generates a random number on [0,0x7fffffff]-interval */
    /// generates a random number on \[0,0x7fffffff\]-interval  
    ///
    /// 0以上0x7FFF_FFFF以下のi32型の乱数を生成します。
    pub fn genrand_i31(&mut self) -> i32 {
        (self.genrand_u32() >> 1) as i32
    }

    /* generates a random number on [0,1]-real-interval */
    /// generates a random number on \[0,1\]-real-interval  
    ///
    /// 0以上1以下のf64型の乱数を生成します。
    pub fn genrand_real1(&mut self) -> f64 {
        (self.genrand_u32() as f64) * (1.0 / 4294967295.0)
        /* divided by 2^32-1 */
    }

    /* generates a random number on [0,1)-real-interval */
    /// generates a random number on \[0,1)-real-interval  
    ///
    /// 0以上1未満のf64型の乱数を生成します。
    pub fn genrand_real2(&mut self) -> f64 {
        (self.genrand_u32() as f64) * (1.0 / 4294967296.0)
        /* divided by 2^32 */
    }

    /* generates a random number on (0,1)-real-interval */
    /// generates a random number on (0,1)-real-interval  
    ///
    /// 1未満のf64型の正数の乱数を生成します。  
    pub fn genrand_real3(&mut self) -> f64 {
        (self.genrand_u32() as f64 + 0.5) * (1.0 / 4294967296.0)
        /* divided by 2^32 */
    }

    /* generates a random number on [0,1) with 53-bit resolution　*/
    /// generates a random number on \[0,1) with 53-bit resolution
    pub fn genrand_res53(&mut self) -> f64 {
        let a = self.genrand_u32() >> 5;
        let b = self.genrand_u32() >> 6;
        (a as f64 * 67108864.0 + b as f64) * (1.0 / 9007199254740992.0)
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn it_works() {
        use crate::MersenneTwister;
        use std::fs::{self, File};
        use std::io::Write;

        let mut b: Vec<u8> = Vec::new();

        let init_key: [u32; 4] = [0x123, 0x234, 0x345, 0x456];

        let mut mt = MersenneTwister::new_by_array(&init_key);

        writeln!(&mut b, "1000 outputs of genrand_int32()").unwrap();
        for i in 0..1000 {
            write!(&mut b, "{:10} ", mt.genrand_u32()).unwrap();
            if i % 5 == 4 {
                writeln!(&mut b).unwrap();
            }
        }
        writeln!(&mut b).unwrap();

        writeln!(&mut b, "1000 outputs of genrand_real2()").unwrap();
        for i in 0..1000 {
            write!(&mut b, "{:10.8} ", mt.genrand_real2()).unwrap();
            if i % 5 == 4 {
                writeln!(&mut b).unwrap();
            }
        }

        let original = fs::read("mt19937ar.out").unwrap();

        assert_eq!(b, original);

        File::create("mt19937ar-rs.out")
            .unwrap()
            .write_all(&b)
            .unwrap();
    }
}

/*
 *  疑似乱数生成機(RNG)  移植(Porting)
 *  Information of Original Source
 *  Mersenne Twister with improved initialization (2002)
 *  http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/mt.html
 *  http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/mt19937ar.html
 */
// = 移植元ラインセンス (License of Original Source) =======================================================
// ======================================================================
/*
   A C-program for MT19937, with initialization improved 2002/1/26.
   Coded by Takuji Nishimura and Makoto Matsumoto.

   Before using, initialize the state by using init_genrand(seed)
   or init_by_array(init_key, key_length).

   Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.

     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.

     3. The names of its contributors may not be used to endorse or promote
        products derived from this software without specific prior written
        permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


   Any feedback is very welcome.
   http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
   email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
*/
// ======================================================================