/* -*- c++ -*- */
/*
 * Copyright 2015 Free Software Foundation, Inc.
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "fec_mtrx_impl.h"
#include <algorithm>
#include <cmath>
#include <fstream>
#include <iostream>
#include <sstream>
#include <stdexcept>
#include <vector>

namespace gr {
namespace fec {
namespace code {

// For use when casting to a matrix_sptr to provide the proper
// callback to free the memory when the reference count goes to
// 0. Needed to know how to cast from our matrix to gsl_matrix.
void matrix_free(matrix* x) { gsl_matrix_free((gsl_matrix*)x); }


matrix_sptr read_matrix_from_file(const std::string filename)
{
    std::ifstream inputFile;
    unsigned int ncols, nrows;

    // Open the alist file (needs a C-string)
    inputFile.open(filename.c_str());
    if (!inputFile) {
        std::stringstream s;
        s << "There was a problem opening file '" << filename << "' for reading.";
        throw std::runtime_error(s.str());
    }

    // First line of file is matrix size: # columns, # rows
    inputFile >> ncols >> nrows;

    // Now we can allocate memory for the GSL matrix
    gsl_matrix* temp_matrix = gsl_matrix_alloc(nrows, ncols);
    gsl_matrix_set_zero(temp_matrix);

    // The next few lines in the file are not necessary in
    // constructing the matrix.
    std::string tempBuffer;
    unsigned int counter;
    for (counter = 0; counter < 4; counter++) {
        getline(inputFile, tempBuffer);
    }

    // These next lines list the indices for where the 1s are in
    // each column.
    unsigned int column_count = 0;
    std::string row_number;

    while (column_count < ncols) {
        getline(inputFile, tempBuffer);
        std::stringstream ss(tempBuffer);

        while (ss >> row_number) {
            int row_i = atoi(row_number.c_str());
            // alist files index starting from 1, not 0, so decrement
            row_i--;
            // set the corresponding matrix element to 1
            gsl_matrix_set(temp_matrix, row_i, column_count, 1);
        }
        column_count++;
    }

    // Close the alist file
    inputFile.close();

    // Stash the pointer
    matrix_sptr H = matrix_sptr((matrix*)temp_matrix, matrix_free);

    return H;
}

void write_matrix_to_file(const std::string filename, matrix_sptr M)
{
    std::ofstream outputfile;

    // Open the output file
    outputfile.open(filename.c_str());
    if (!outputfile) {
        std::stringstream s;
        s << "There was a problem opening file '" << filename << "' for writing.";
        throw std::runtime_error(s.str());
    }

    unsigned int ncols = M->size2;
    unsigned int nrows = M->size1;
    std::vector<unsigned int> colweights(ncols, 0);
    std::vector<unsigned int> rowweights(nrows, 0);
    std::stringstream colout;
    std::stringstream rowout;

    for (unsigned int c = 0; c < ncols; c++) {
        for (unsigned int r = 0; r < nrows; r++) {
            double x = gsl_matrix_get((gsl_matrix*)(M.get()), r, c);
            if (x == 1) {
                colout << (r + 1) << " ";
                colweights[c]++;
            }
        }
        colout << std::endl;
    }

    for (unsigned int r = 0; r < nrows; r++) {
        for (unsigned int c = 0; c < ncols; c++) {
            double x = gsl_matrix_get((gsl_matrix*)(M.get()), r, c);
            if (x == 1) {
                rowout << (c + 1) << " ";
                rowweights[r]++;
            }
        }
        rowout << std::endl;
    }

    outputfile << ncols << " " << nrows << std::endl;
    outputfile << (*std::max_element(colweights.begin(), colweights.end())) << " "
               << (*std::max_element(rowweights.begin(), rowweights.end())) << std::endl;

    for (const auto& weight : colweights) {
        outputfile << weight << " ";
    }
    outputfile << std::endl;

    for (const auto& weight : rowweights) {
        outputfile << weight << " ";
    }
    outputfile << std::endl;

    outputfile << colout.str() << rowout.str();

    // Close the alist file
    outputfile.close();
}

matrix_sptr generate_G_transpose(matrix_sptr H_obj)
{
    unsigned int k = H_obj->size1;
    unsigned int n = H_obj->size2;
    unsigned int row_index, col_index;

    gsl_matrix* G_transp = gsl_matrix_alloc(n, k);

    // Grab P' matrix (P' denotes P transposed)
    gsl_matrix* P_transpose = gsl_matrix_alloc(n - k, k);
    for (row_index = 0; row_index < n - k; row_index++) {
        for (col_index = 0; col_index < k; col_index++) {
            int value = gsl_matrix_get((gsl_matrix*)(H_obj.get()), row_index, col_index);
            gsl_matrix_set(P_transpose, row_index, col_index, value);
        }
    }

    // Set G transpose matrix (used for encoding)
    gsl_matrix_set_zero(G_transp);
    for (row_index = 0; row_index < k; row_index++) {
        col_index = row_index;
        gsl_matrix_set(G_transp, row_index, col_index, 1);
    }
    for (row_index = k; row_index < n; row_index++) {
        for (col_index = 0; col_index < k; col_index++) {
            int value = gsl_matrix_get(P_transpose, row_index - k, col_index);
            gsl_matrix_set(G_transp, row_index, col_index, value);
        }
    }

    // Stash the pointer
    matrix_sptr G = matrix_sptr((matrix*)G_transp, matrix_free);

    // Free memory
    gsl_matrix_free(P_transpose);

    return G;
}

matrix_sptr generate_G(matrix_sptr H_obj)
{
    matrix_sptr G_trans = generate_G_transpose(H_obj);

    unsigned int k = H_obj->size1;
    unsigned int n = H_obj->size2;
    gsl_matrix* G = gsl_matrix_alloc(k, n);

    gsl_matrix_transpose_memcpy(G, (gsl_matrix*)(G_trans.get()));

    matrix_sptr Gret = matrix_sptr((matrix*)G, matrix_free);
    return Gret;
}

matrix_sptr generate_H(matrix_sptr G_obj)
{
    unsigned int row_index, col_index;

    unsigned int n = G_obj->size2;
    unsigned int k = G_obj->size1;

    gsl_matrix* G_ptr = (gsl_matrix*)(G_obj.get());
    gsl_matrix* H_ptr = gsl_matrix_alloc(n - k, n);

    // Grab P matrix
    gsl_matrix* P = gsl_matrix_alloc(k, n - k);
    for (row_index = 0; row_index < k; row_index++) {
        for (col_index = 0; col_index < n - k; col_index++) {
            int value = gsl_matrix_get(G_ptr, row_index, col_index + k);
            gsl_matrix_set(P, row_index, col_index, value);
        }
    }

    // Calculate P transpose
    gsl_matrix* P_transpose = gsl_matrix_alloc(n - k, k);
    gsl_matrix_transpose_memcpy(P_transpose, P);

    // Set H matrix. H = [-P' I] but since we are doing mod 2,
    // -P = P, so H = [P' I]
    gsl_matrix_set_zero(H_ptr);
    for (row_index = 0; row_index < n - k; row_index++) {
        for (col_index = 0; col_index < k; col_index++) {
            int value = gsl_matrix_get(P_transpose, row_index, col_index);
            gsl_matrix_set(H_ptr, row_index, col_index, value);
        }
    }

    for (row_index = 0; row_index < n - k; row_index++) {
        col_index = row_index + k;
        gsl_matrix_set(H_ptr, row_index, col_index, 1);
    }

    // Free memory
    gsl_matrix_free(P);
    gsl_matrix_free(P_transpose);

    matrix_sptr H = matrix_sptr((matrix*)H_ptr, matrix_free);
    return H;
}


void print_matrix(const matrix_sptr M, bool numpy)
{
    if (!numpy) {
        for (size_t i = 0; i < M->size1; i++) {
            for (size_t j = 0; j < M->size2; j++) {
                std::cout << gsl_matrix_get((gsl_matrix*)(M.get()), i, j) << " ";
            }
            std::cout << std::endl;
        }
        std::cout << std::endl;
    } else {
        std::cout << "numpy.matrix([ ";
        for (size_t i = 0; i < M->size1; i++) {
            std::cout << "[ ";
            for (size_t j = 0; j < M->size2; j++) {
                std::cout << gsl_matrix_get((gsl_matrix*)(M.get()), i, j) << ", ";
            }
            std::cout << "], ";
        }
        std::cout << "])" << std::endl;
    }
}


fec_mtrx_impl::fec_mtrx_impl()
{
    // Assume the convention that parity bits come last in the
    // codeword
    d_par_bits_last = true;
}

const gsl_matrix* fec_mtrx_impl::H() const
{
    const gsl_matrix* H_ptr = (gsl_matrix*)(d_H_sptr.get());
    return H_ptr;
}

unsigned int fec_mtrx_impl::n() const { return d_n; }

unsigned int fec_mtrx_impl::k() const { return d_k; }

void fec_mtrx_impl::add_matrices_mod2(gsl_matrix* result,
                                      const gsl_matrix* matrix1,
                                      const gsl_matrix* matrix2) const
{
    // This function returns ((matrix1 + matrix2) % 2).

    // Verify that matrix sizes are appropriate
    unsigned int matrix1_rows = (*matrix1).size1;
    unsigned int matrix1_cols = (*matrix1).size2;
    unsigned int matrix2_rows = (*matrix2).size1;
    unsigned int matrix2_cols = (*matrix2).size2;

    if (matrix1_rows != matrix2_rows) {
        std::cout << "Error in add_matrices_mod2. Matrices do"
                  << " not have the same number of rows.\n";
        exit(1);
    }
    if (matrix1_cols != matrix2_cols) {
        std::cout << "Error in add_matrices_mod2. Matrices do"
                  << " not have the same number of columns.\n";
        exit(1);
    }

    // Copy matrix1 into result
    gsl_matrix_memcpy(result, matrix1);

    // Do subtraction. This is not mod 2 yet.
    gsl_matrix_add(result, matrix2);

    // Take care of mod 2 manually
    unsigned int row_index, col_index;
    for (row_index = 0; row_index < matrix1_rows; row_index++) {
        for (col_index = 0; col_index < matrix1_cols; col_index++) {
            int value = gsl_matrix_get(result, row_index, col_index);
            int new_value = abs(value) % 2;
            gsl_matrix_set(result, row_index, col_index, new_value);
        }
    }
}

void fec_mtrx_impl::mult_matrices_mod2(gsl_matrix* result,
                                       const gsl_matrix* matrix1,
                                       const gsl_matrix* matrix2) const
{
    // Verify that matrix sizes are appropriate
    unsigned int a = (*matrix1).size1; // # of rows
    unsigned int b = (*matrix1).size2; // # of columns
    unsigned int c = (*matrix2).size1; // # of rows
    unsigned int d = (*matrix2).size2; // # of columns
    if (b != c) {
        std::cout << "Error in "
                  << "fec_mtrx_impl::mult_matrices_mod2."
                  << " Matrix dimensions do not allow for matrix "
                  << "multiplication operation:\nmatrix1 is " << a << " x " << b
                  << ", and matrix2 is " << c << " x " << d << ".\n";
        exit(1);
    }

    // Perform matrix multiplication. This is not mod 2.
    gsl_blas_dgemm(CblasNoTrans, CblasNoTrans, 1.0, matrix1, matrix2, 0.0, result);

    // Take care of mod 2 manually.
    unsigned int row_index, col_index;
    unsigned int rows = (*result).size1, cols = (*result).size2;
    for (row_index = 0; row_index < rows; row_index++) {
        for (col_index = 0; col_index < cols; col_index++) {
            int value = gsl_matrix_get(result, row_index, col_index);
            int new_value = value % 2;
            gsl_matrix_set(result, row_index, col_index, new_value);
        }
    }
}

gsl_matrix* fec_mtrx_impl::calc_inverse_mod2(const gsl_matrix* original_matrix) const
{

    // Let n represent the size of the n x n square matrix
    unsigned int n = (*original_matrix).size1;
    unsigned int row_index, col_index;

    // Make a copy of the original matrix, call it matrix_altered.
    // This matrix will be modified by the GSL functions.
    gsl_matrix* matrix_altered = gsl_matrix_alloc(n, n);
    gsl_matrix_memcpy(matrix_altered, original_matrix);

    // In order to find the inverse, GSL must perform a LU
    // decomposition first.
    gsl_permutation* permutation = gsl_permutation_alloc(n);
    int signum;
    gsl_linalg_LU_decomp(matrix_altered, permutation, &signum);

    // Allocate memory to store the matrix inverse
    gsl_matrix* matrix_inverse = gsl_matrix_alloc(n, n);

    // Find matrix inverse. This is not mod2.
    int status = gsl_linalg_LU_invert(matrix_altered, permutation, matrix_inverse);

    if (status) {
        // Inverse not found by GSL functions.
        throw "Error in calc_inverse_mod2(): inverse not found.";
    }

    // Find determinant
    float determinant = gsl_linalg_LU_det(matrix_altered, signum);

    // Multiply the matrix inverse by the determinant.
    gsl_matrix_scale(matrix_inverse, determinant);

    // Take mod 2 of each element in the matrix.
    for (row_index = 0; row_index < n; row_index++) {
        for (col_index = 0; col_index < n; col_index++) {

            float value = gsl_matrix_get(matrix_inverse, row_index, col_index);

            // take care of mod 2
            int value_cast_as_int = static_cast<int>(value);
            int temp_value = abs(fmod(value_cast_as_int, 2));

            gsl_matrix_set(matrix_inverse, row_index, col_index, temp_value);
        }
    }

    int max_value = gsl_matrix_max(matrix_inverse);
    if (!max_value) {
        throw "Error in calc_inverse_mod2(): The matrix inverse found is all zeros.";
    }

    // Verify that the inverse was found by taking matrix
    // product of original_matrix and the inverse, which should
    // equal the identity matrix.
    gsl_matrix* test = gsl_matrix_alloc(n, n);
    mult_matrices_mod2(test, original_matrix, matrix_inverse);

    gsl_matrix* identity = gsl_matrix_alloc(n, n);
    gsl_matrix_set_identity(identity);
    // int test_if_equal = gsl_matrix_equal(identity,test);
    gsl_matrix_sub(identity, test); // should be null set if equal

    double test_if_not_equal = gsl_matrix_max(identity);

    if (test_if_not_equal > 0) {
        throw "Error in calc_inverse_mod2(): The matrix inverse found is not valid.";
    }

    return matrix_inverse;
}

bool fec_mtrx_impl::parity_bits_come_last() const { return d_par_bits_last; }

fec_mtrx_impl::~fec_mtrx_impl() {}

} /* namespace code */
} /* namespace fec */
} /* namespace gr */
