#include "Rabin_fingerprint.hpp"

Rabin_fingerprint::Rabin_fingerprint(uint32_t p, size_t window_size_in_bits) {
    set_modulo_polynomial(p);
    set_shift_polynomial(window_size_in_bits);
}

void Rabin_fingerprint::set_modulo_polynomial (uint32_t p) {
    polynomial = p & ((uint32_t)pow(2, 31)-1);
}

void Rabin_fingerprint::set_shift_polynomial (size_t window_size_in_bits) {
    #ifndef NDEBUG
    if (polynomial == 0)
        throw std::logic_error("Call set_modulo_polynomial first, as this function depends on the polynomial variable being set.");
    #endif

    shift_polynomial = 1;

    // NOTE: We shift the bit 1 space too long, since we are removing the bit that has been pushed outside the window
    for (size_t i = 0; i < window_size_in_bits; i++) {
        shift_polynomial <<= 1;
        if ((shift_polynomial & (uint32_t)pow(2, 31)) != 0)
            shift_polynomial ^= polynomial;
    }
}


void Rabin_fingerprint::push_char (char c) {
    std::bitset<8> b(c);
    for (char i = 7; i >= 0; i--) {
        push_bit((bool)b[i]);
    }
}

void Rabin_fingerprint::push_bit (bool b) {
    fingerprint <<= 1;
    fingerprint |= b;
    if ((fingerprint & (uint32_t)pow(2, 31)) != 0)
        fingerprint ^= polynomial;
}

void Rabin_fingerprint::shift_bit (bool b) {
    #ifndef NDEBUG
    if (shift_polynomial == 0)
        throw std::logic_error("Call set_shift_polynomial first, as this function depends on the shift_polynomial variable being set.");
    #endif

    if (b)
        fingerprint ^= shift_polynomial;
}

void Rabin_fingerprint::slide_char (char c_in, char c_out) {
    std::bitset<8> b_in(c_in);
    std::bitset<8> b_out(c_out);
    for (char i = 7; i >= 0; i--) {
        slide_bit((bool)b_in[i], (bool)b_out[i]);
    }
}

/* #include <iostream> */
void Rabin_fingerprint::slide_bit (bool b_in, bool b_out) {
    /* std::cout << "bitset b(c):  " << b << std::endl; */
        /* std::cout << "push bit " << b[i] << std::endl; */
    /* std::cout << "push bit " << b_in << std::endl; */
    push_bit(b_in);
    /* std::cout << "shift bit " << b_out << std::endl; */
    shift_bit(b_out);
}

uint32_t Rabin_fingerprint::get_fingerprint () {
    return fingerprint;
}