// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity.  If not, see <http://www.gnu.org/licenses/>.

use compute::{calculate_dag_item, FNV_PRIME};
use keccak::H256;
use shared::{get_data_size, Node, ETHASH_ACCESSES, ETHASH_MIX_BYTES};

const PROGPOW_CACHE_BYTES: usize = 16 * 1024;
const PROGPOW_CACHE_WORDS: usize = PROGPOW_CACHE_BYTES / 4;
const PROGPOW_CNT_CACHE: usize = 12;
const PROGPOW_CNT_MATH: usize = 20;
const PROGPOW_CNT_DAG: usize = ETHASH_ACCESSES;
const PROGPOW_DAG_LOADS: usize = 4;
const PROGPOW_MIX_BYTES: usize = 2 * ETHASH_MIX_BYTES;
const PROGPOW_PERIOD_LENGTH: usize = 50; // blocks per progpow epoch (N)
const PROGPOW_LANES: usize = 16;
const PROGPOW_REGS: usize = 32;

const FNV_HASH: u32 = 0x811c9dc5;

const KECCAKF_RNDC: [u32; 24] = [
    0x00000001, 0x00008082, 0x0000808a, 0x80008000, 0x0000808b, 0x80000001, 0x80008081, 0x00008009,
    0x0000008a, 0x00000088, 0x80008009, 0x8000000a, 0x8000808b, 0x0000008b, 0x00008089, 0x00008003,
    0x00008002, 0x00000080, 0x0000800a, 0x8000000a, 0x80008081, 0x00008080, 0x80000001, 0x80008008,
];

const KECCAKF_ROTC: [u32; 24] = [
    1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 2, 14, 27, 41, 56, 8, 25, 43, 62, 18, 39, 61, 20, 44,
];

const KECCAKF_PILN: [usize; 24] = [
    10, 7, 11, 17, 18, 3, 5, 16, 8, 21, 24, 4, 15, 23, 19, 13, 12, 2, 20, 14, 22, 9, 6, 1,
];

fn keccak_f800_round(st: &mut [u32; 25], r: usize) {
    // Theta
    let mut bc = [0u32; 5];
    for i in 0..bc.len() {
        bc[i] = st[i] ^ st[i + 5] ^ st[i + 10] ^ st[i + 15] ^ st[i + 20];
    }

    for i in 0..bc.len() {
        let t = bc[(i + 4) % 5] ^ bc[(i + 1) % 5].rotate_left(1);
        for j in (0..st.len()).step_by(5) {
            st[j + i] ^= t;
        }
    }

    // Rho Pi
    let mut t = st[1];

    debug_assert_eq!(KECCAKF_ROTC.len(), 24);
    for i in 0..24 {
        let j = KECCAKF_PILN[i];
        bc[0] = st[j];
        st[j] = t.rotate_left(KECCAKF_ROTC[i]);
        t = bc[0];
    }

    // Chi
    for j in (0..st.len()).step_by(5) {
        for i in 0..bc.len() {
            bc[i] = st[j + i];
        }
        for i in 0..bc.len() {
            st[j + i] ^= (!bc[(i + 1) % 5]) & bc[(i + 2) % 5];
        }
    }

    // Iota
    debug_assert!(r < KECCAKF_RNDC.len());
    st[0] ^= KECCAKF_RNDC[r];
}

fn keccak_f800(header_hash: H256, nonce: u64, result: [u32; 8], st: &mut [u32; 25]) {
    for i in 0..8 {
        st[i] = (header_hash[4 * i] as u32)
            + ((header_hash[4 * i + 1] as u32) << 8)
            + ((header_hash[4 * i + 2] as u32) << 16)
            + ((header_hash[4 * i + 3] as u32) << 24);
    }

    st[8] = nonce as u32;
    st[9] = (nonce >> 32) as u32;

    for i in 0..8 {
        st[10 + i] = result[i];
    }

    for r in 0..22 {
        keccak_f800_round(st, r);
    }
}

pub fn keccak_f800_short(header_hash: H256, nonce: u64, result: [u32; 8]) -> u64 {
    let mut st = [0u32; 25];
    keccak_f800(header_hash, nonce, result, &mut st);
    (st[0].swap_bytes() as u64) << 32 | st[1].swap_bytes() as u64
}

pub fn keccak_f800_long(header_hash: H256, nonce: u64, result: [u32; 8]) -> H256 {
    let mut st = [0u32; 25];
    keccak_f800(header_hash, nonce, result, &mut st);

    // NOTE: transmute from `[u32; 8]` to `[u8; 32]`
    unsafe { std::mem::transmute([st[0], st[1], st[2], st[3], st[4], st[5], st[6], st[7]]) }
}

#[inline]
fn fnv1a_hash(h: u32, d: u32) -> u32 {
    (h ^ d).wrapping_mul(FNV_PRIME)
}

#[derive(Clone)]
struct Kiss99 {
    z: u32,
    w: u32,
    jsr: u32,
    jcong: u32,
}

impl Kiss99 {
    fn new(z: u32, w: u32, jsr: u32, jcong: u32) -> Kiss99 {
        Kiss99 { z, w, jsr, jcong }
    }

    #[inline]
    fn next_u32(&mut self) -> u32 {
        self.z = 36969u32
            .wrapping_mul(self.z & 65535)
            .wrapping_add(self.z >> 16);
        self.w = 18000u32
            .wrapping_mul(self.w & 65535)
            .wrapping_add(self.w >> 16);
        let mwc = (self.z << 16).wrapping_add(self.w);
        self.jsr ^= self.jsr << 17;
        self.jsr ^= self.jsr >> 13;
        self.jsr ^= self.jsr << 5;
        self.jcong = 69069u32.wrapping_mul(self.jcong).wrapping_add(1234567);

        (mwc ^ self.jcong).wrapping_add(self.jsr)
    }
}

fn fill_mix(seed: u64, lane_id: u32) -> [u32; PROGPOW_REGS] {
    // Use FNV to expand the per-warp seed to per-lane
    // Use KISS to expand the per-lane seed to fill mix
    let z = fnv1a_hash(FNV_HASH, seed as u32);
    let w = fnv1a_hash(z, (seed >> 32) as u32);
    let jsr = fnv1a_hash(w, lane_id);
    let jcong = fnv1a_hash(jsr, lane_id);

    let mut rnd = Kiss99::new(z, w, jsr, jcong);

    let mut mix = [0; PROGPOW_REGS];

    debug_assert_eq!(PROGPOW_REGS, 32);
    for i in 0..32 {
        mix[i] = rnd.next_u32();
    }

    mix
}

// Merge new data from b into the value in a. Assuming A has high entropy only
// do ops that retain entropy even if B is low entropy (IE don't do A&B)
fn merge(a: u32, b: u32, r: u32) -> u32 {
    match r % 4 {
        0 => a.wrapping_mul(33).wrapping_add(b),
        1 => (a ^ b).wrapping_mul(33),
        2 => a.rotate_left(((r >> 16) % 31) + 1) ^ b,
        _ => a.rotate_right(((r >> 16) % 31) + 1) ^ b,
    }
}

fn math(a: u32, b: u32, r: u32) -> u32 {
    match r % 11 {
        0 => a.wrapping_add(b),
        1 => a.wrapping_mul(b),
        2 => ((a as u64).wrapping_mul(b as u64) >> 32) as u32,
        3 => a.min(b),
        4 => a.rotate_left(b),
        5 => a.rotate_right(b),
        6 => a & b,
        7 => a | b,
        8 => a ^ b,
        9 => a.leading_zeros() + b.leading_zeros(),
        _ => a.count_ones() + b.count_ones(),
    }
}

fn progpow_init(seed: u64) -> (Kiss99, [u32; PROGPOW_REGS], [u32; PROGPOW_REGS]) {
    let z = fnv1a_hash(FNV_HASH, seed as u32);
    let w = fnv1a_hash(z, (seed >> 32) as u32);
    let jsr = fnv1a_hash(w, seed as u32);
    let jcong = fnv1a_hash(jsr, (seed >> 32) as u32);

    let mut rnd = Kiss99::new(z, w, jsr, jcong);

    // Create a random sequence of mix destinations for merge() and mix sources
    // for cache reads guarantees every destination merged once and guarantees
    // no duplicate cache reads, which could be optimized away. Uses
    // Fisher-Yates shuffle.
    let mut mix_seq_dst = [0u32; PROGPOW_REGS];
    let mut mix_seq_cache = [0u32; PROGPOW_REGS];
    for i in 0..mix_seq_dst.len() {
        mix_seq_dst[i] = i as u32;
        mix_seq_cache[i] = i as u32;
    }

    for i in (1..mix_seq_dst.len()).rev() {
        let j = rnd.next_u32() as usize % (i + 1);
        mix_seq_dst.swap(i, j);

        let j = rnd.next_u32() as usize % (i + 1);
        mix_seq_cache.swap(i, j);
    }

    (rnd, mix_seq_dst, mix_seq_cache)
}

pub type CDag = [u32; PROGPOW_CACHE_WORDS];

fn progpow_loop(
    seed: u64,
    loop_: usize,
    mix: &mut [[u32; PROGPOW_REGS]; PROGPOW_LANES],
    cache: &[Node],
    c_dag: &CDag,
    data_size: usize,
) {
    // All lanes share a base address for the global load. Global offset uses
    // mix[0] to guarantee it depends on the load result.
    let g_offset = mix[loop_ % PROGPOW_LANES][0] as usize
        % (64 * data_size / (PROGPOW_LANES * PROGPOW_DAG_LOADS));

    // 256 bytes of dag data
    let mut dag_item = [0u32; 64];

    // Fetch DAG nodes (64 bytes each)
    for l in 0..PROGPOW_DAG_LOADS {
        let index = g_offset * PROGPOW_LANES * PROGPOW_DAG_LOADS + l * 16;
        let node = calculate_dag_item(index as u32 / 16, cache);
        dag_item[l * 16..(l + 1) * 16].clone_from_slice(node.as_words());
    }

    let (rnd, mix_seq_dst, mix_seq_cache) = progpow_init(seed);

    // Lanes can execute in parallel and will be convergent
    for l in 0..mix.len() {
        let mut rnd = rnd.clone();

        // Initialize the seed and mix destination sequence
        let mut mix_seq_dst_cnt = 0;
        let mut mix_seq_cache_cnt = 0;

        let mut mix_dst = || {
            let res = mix_seq_dst[mix_seq_dst_cnt % PROGPOW_REGS] as usize;
            mix_seq_dst_cnt += 1;
            res
        };
        let mut mix_cache = || {
            let res = mix_seq_cache[mix_seq_cache_cnt % PROGPOW_REGS] as usize;
            mix_seq_cache_cnt += 1;
            res
        };

        for i in 0..PROGPOW_CNT_CACHE.max(PROGPOW_CNT_MATH) {
            if i < PROGPOW_CNT_CACHE {
                // Cached memory access, lanes access random 32-bit locations
                // within the first portion of the DAG
                let offset = mix[l][mix_cache()] as usize % PROGPOW_CACHE_WORDS;
                let data = c_dag[offset];
                let dst = mix_dst();

                mix[l][dst] = merge(mix[l][dst], data, rnd.next_u32());
            }

            if i < PROGPOW_CNT_MATH {
                // Random math
                // Generate 2 unique sources
                let src_rnd = rnd.next_u32() % (PROGPOW_REGS * (PROGPOW_REGS - 1)) as u32;
                let src1 = src_rnd % PROGPOW_REGS as u32; // 0 <= src1 < PROGPOW_REGS
                let mut src2 = src_rnd / PROGPOW_REGS as u32; // 0 <= src2 < PROGPOW_REGS - 1
                if src2 >= src1 {
                    src2 += 1; // src2 is now any reg other than src1
                }

                let data = math(mix[l][src1 as usize], mix[l][src2 as usize], rnd.next_u32());
                let dst = mix_dst();

                mix[l][dst] = merge(mix[l][dst], data, rnd.next_u32());
            }
        }

        // Global load to sequential locations
        let mut data_g = [0u32; PROGPOW_DAG_LOADS];
        let index = ((l ^ loop_) % PROGPOW_LANES) * PROGPOW_DAG_LOADS;
        for i in 0..PROGPOW_DAG_LOADS {
            data_g[i] = dag_item[index + i];
        }

        // Consume the global load data at the very end of the loop to allow
        // full latency hiding. Always merge into `mix[0]` to feed the offset
        // calculation.
        mix[l][0] = merge(mix[l][0], data_g[0], rnd.next_u32());
        for i in 1..PROGPOW_DAG_LOADS {
            let dst = mix_dst();
            mix[l][dst] = merge(mix[l][dst], data_g[i], rnd.next_u32());
        }
    }
}

pub fn progpow(
    header_hash: H256,
    nonce: u64,
    block_number: u64,
    cache: &[Node],
    c_dag: &CDag,
) -> (H256, H256) {
    let mut mix = [[0u32; PROGPOW_REGS]; PROGPOW_LANES];
    let mut lane_results = [0u32; PROGPOW_LANES];
    let mut result = [0u32; 8];

    let data_size = get_data_size(block_number) / PROGPOW_MIX_BYTES;

    // NOTE: This assert is required to aid the optimizer elide the non-zero
    // remainder check in `progpow_loop`.
    assert!(data_size > 0);

    // Initialize mix for all lanes
    let seed = keccak_f800_short(header_hash, nonce, result);

    for l in 0..mix.len() {
        mix[l] = fill_mix(seed, l as u32);
    }

    // Execute the randomly generated inner loop
    let period = block_number / PROGPOW_PERIOD_LENGTH as u64;
    for i in 0..PROGPOW_CNT_DAG {
        progpow_loop(period, i, &mut mix, cache, c_dag, data_size);
    }

    // Reduce mix data to a single per-lane result
    for l in 0..lane_results.len() {
        lane_results[l] = FNV_HASH;
        for i in 0..PROGPOW_REGS {
            lane_results[l] = fnv1a_hash(lane_results[l], mix[l][i]);
        }
    }

    // Reduce all lanes to a single 128-bit result
    result = [FNV_HASH; 8];
    for l in 0..PROGPOW_LANES {
        result[l % 8] = fnv1a_hash(result[l % 8], lane_results[l]);
    }

    let digest = keccak_f800_long(header_hash, seed, result);

    // NOTE: transmute from `[u32; 8]` to `[u8; 32]`
    let result = unsafe { ::std::mem::transmute(result) };

    (digest, result)
}

pub fn generate_cdag(cache: &[Node]) -> CDag {
    let mut c_dag = [0u32; PROGPOW_CACHE_WORDS];

    for i in 0..PROGPOW_CACHE_WORDS / 16 {
        let node = calculate_dag_item(i as u32, cache);
        for j in 0..16 {
            c_dag[i * 16 + j] = node.as_words()[j];
        }
    }

    c_dag
}

#[cfg(test)]
mod test {
    use tempdir::TempDir;

    use super::*;
    use cache::{NodeCacheBuilder, OptimizeFor};
    use keccak::H256;
    use rustc_hex::FromHex;
    use serde_json::{self, Value};
    use std::collections::VecDeque;

    fn h256(hex: &str) -> H256 {
        let bytes = FromHex::from_hex(hex).unwrap();
        let mut res = [0; 32];
        res.copy_from_slice(&bytes);
        res
    }

    #[test]
    fn test_cdag() {
        let builder = NodeCacheBuilder::new(OptimizeFor::Memory, u64::max_value());
        let tempdir = TempDir::new("").unwrap();
        let cache = builder.new_cache(tempdir.into_path(), 0);

        let c_dag = generate_cdag(cache.as_ref());

        let expected = vec![
            690150178u32,
            1181503948,
            2248155602,
            2118233073,
            2193871115,
            1791778428,
            1067701239,
            724807309,
            530799275,
            3480325829,
            3899029234,
            1998124059,
            2541974622,
            1100859971,
            1297211151,
            3268320000,
            2217813733,
            2690422980,
            3172863319,
            2651064309,
        ];

        assert_eq!(c_dag.iter().take(20).cloned().collect::<Vec<_>>(), expected,);
    }

    #[test]
    fn test_random_merge() {
        let tests = [
            (1000000u32, 101u32, 33000101u32),
            (2000000, 102, 66003366),
            (3000000, 103, 6000103),
            (4000000, 104, 2000104),
            (1000000, 0, 33000000),
            (2000000, 0, 66000000),
            (3000000, 0, 6000000),
            (4000000, 0, 2000000),
        ];

        for (i, &(a, b, expected)) in tests.iter().enumerate() {
            assert_eq!(merge(a, b, i as u32), expected,);
        }
    }

    #[test]
    fn test_random_math() {
        let tests = [
            (20u32, 22u32, 42u32),
            (70000, 80000, 1305032704),
            (70000, 80000, 1),
            (1, 2, 1),
            (3, 10000, 196608),
            (3, 0, 3),
            (3, 6, 2),
            (3, 6, 7),
            (3, 6, 5),
            (0, 0xffffffff, 32),
            (3 << 13, 1 << 5, 3),
            (22, 20, 42),
            (80000, 70000, 1305032704),
            (80000, 70000, 1),
            (2, 1, 1),
            (10000, 3, 80000),
            (0, 3, 0),
            (6, 3, 2),
            (6, 3, 7),
            (6, 3, 5),
            (0, 0xffffffff, 32),
            (3 << 13, 1 << 5, 3),
        ];

        for (i, &(a, b, expected)) in tests.iter().enumerate() {
            assert_eq!(math(a, b, i as u32), expected,);
        }
    }

    #[test]
    fn test_keccak_256() {
        let expected = "5dd431e5fbc604f499bfa0232f45f8f142d0ff5178f539e5a7800bf0643697af";
        assert_eq!(keccak_f800_long([0; 32], 0, [0; 8]), h256(expected),);
    }

    #[test]
    fn test_keccak_64() {
        let expected: u64 = 0x5dd431e5fbc604f4;
        assert_eq!(keccak_f800_short([0; 32], 0, [0; 8]), expected,);
    }

    #[test]
    fn test_progpow_hash() {
        let builder = NodeCacheBuilder::new(OptimizeFor::Memory, u64::max_value());
        let tempdir = TempDir::new("").unwrap();
        let cache = builder.new_cache(tempdir.into_path(), 0);
        let c_dag = generate_cdag(cache.as_ref());

        let header_hash = [0; 32];

        let (digest, result) = progpow(header_hash, 0, 0, cache.as_ref(), &c_dag);

        let expected_digest =
            FromHex::from_hex("63155f732f2bf556967f906155b510c917e48e99685ead76ea83f4eca03ab12b")
                .unwrap();
        let expected_result =
            FromHex::from_hex("faeb1be51075b03a4ff44b335067951ead07a3b078539ace76fd56fc410557a3")
                .unwrap();

        assert_eq!(digest.to_vec(), expected_digest,);

        assert_eq!(result.to_vec(), expected_result,);
    }

    #[test]
    fn test_progpow_testvectors() {
        struct ProgpowTest {
            block_number: u64,
            header_hash: H256,
            nonce: u64,
            mix_hash: H256,
            final_hash: H256,
        }

        let tests: Vec<VecDeque<Value>> =
            serde_json::from_slice(include_bytes!("../res/progpow_testvectors.json")).unwrap();

        let tests: Vec<ProgpowTest> = tests
            .into_iter()
            .map(|mut test: VecDeque<Value>| {
                assert!(test.len() == 5);

                let block_number: u64 = serde_json::from_value(test.pop_front().unwrap()).unwrap();
                let header_hash: String =
                    serde_json::from_value(test.pop_front().unwrap()).unwrap();
                let nonce: String = serde_json::from_value(test.pop_front().unwrap()).unwrap();
                let mix_hash: String = serde_json::from_value(test.pop_front().unwrap()).unwrap();
                let final_hash: String = serde_json::from_value(test.pop_front().unwrap()).unwrap();

                ProgpowTest {
                    block_number,
                    header_hash: h256(&header_hash),
                    nonce: u64::from_str_radix(&nonce, 16).unwrap(),
                    mix_hash: h256(&mix_hash),
                    final_hash: h256(&final_hash),
                }
            })
            .collect();

        for test in tests {
            let builder = NodeCacheBuilder::new(OptimizeFor::Memory, u64::max_value());
            let tempdir = TempDir::new("").unwrap();
            let cache = builder.new_cache(tempdir.path().to_owned(), test.block_number);
            let c_dag = generate_cdag(cache.as_ref());

            let (digest, result) = progpow(
                test.header_hash,
                test.nonce,
                test.block_number,
                cache.as_ref(),
                &c_dag,
            );

            assert_eq!(digest, test.final_hash);
            assert_eq!(result, test.mix_hash);
        }
    }
}