#![no_std]

pub mod bloom_filter {
    use konst::primitive::{parse_usize, parse_u32};
    use konst::unwrap_ctx;
    use konst::option::unwrap_or;

    pub const ADDRESS_BITS: usize = unwrap_ctx!(parse_usize(unwrap_or!(option_env!("BLOOMFILTER_ADDRESS_BITS"), "30"))); // default = 0x1E = 30
    pub const BITS: usize = 1 << ADDRESS_BITS; // default = 0x40_000_000 = 128MB
    pub const ADDRESS_MASK: usize = BITS - 1;

    pub const WORD_BITS: usize = 0x8; // 8
    pub type WordType = u8;
    pub const ADDRESS_BITS_WORD: usize = 0x3; // log_2(0x8)
    pub const ADDRESS_MASK_WORD: usize = WORD_BITS - 1; // 0x7

    pub const ADDRESS_BITS_CHUNK: usize = unwrap_ctx!(parse_usize(unwrap_or!(option_env!("BLOOMFILTER_ADDRESS_BITS_CHUNK"), "18"))); // default = 0x12 = 18 = log_2(32KB)
    pub const CHUNK_BITS: usize = 1 << ADDRESS_BITS_CHUNK; // default = 0x40000  = 32KB (per-cpu map value size limit)
    pub const CHUNK_BYTES: usize = CHUNK_BITS >> 0x3;
    pub const CHUNK_SIZE: usize = CHUNK_BITS >> ADDRESS_BITS_WORD; // WORD_SIZE * CHUNK_SIZE = 32Kb
    pub type ChunkType = [WordType; CHUNK_SIZE];
    pub const ADDRESS_MASK_CHUNK: usize = CHUNK_BITS - 1;

    pub const BUFFER_SIZE: usize = BITS >> ADDRESS_BITS_WORD; // 0x20_0000
    pub const MAP_SIZE: usize = BITS >> ADDRESS_BITS_CHUNK;

    pub const HASH_COUNT: u32 = unwrap_ctx!(parse_u32(unwrap_or!(option_env!("BLOOMFILTER_HASH_COUNT"), "10")));
    // Hashing based on jhash.h from kernel // TODO improve reference
    const HASH_INITVAL: u32 = 0xdeadbeef;

    #[inline(always)]
    pub fn hash(key: u32, initial_value: u32) -> u32 {
        let mut b = HASH_INITVAL.wrapping_add(initial_value);
        let mut c = b;

        let mut a = key.wrapping_add(b);

        c ^= b;
        c = c.wrapping_sub(b.rotate_left(14));
        a ^= c;
        a = a.wrapping_sub(c.rotate_left(11));
        b ^= a;
        b = b.wrapping_sub(a.rotate_left(25));
        c ^= b;
        c = c.wrapping_sub(b.rotate_left(16));
        a ^= c;
        a = a.wrapping_sub(c.rotate_left(4));
        b ^= a;
        b = b.wrapping_sub(a.rotate_left(14));
        c ^= b;
        c = c.wrapping_sub(b.rotate_left(24));

        return c & ADDRESS_MASK as u32;
    }
}