#include "Laplacian.h"

sparse_matrix_arr* Elad_Laplacian( int *fa , int nf , int nv )
{
        int i , j , t1 , t2 , nnz;
        sparse_matrix_arr *lplcn;
        sparse_matrix_lst *temp = allocate_sparse_matrix_lst(nv);
        cell_t *cell;

        nnz = nv;

        // Initialize the temp sml.
        for ( i = 0 ; i < nv ; i++ )
        {
                cell = create_cell_t( i , i , 0.0 );
                insert_NEW_cell_into_matrix( cell, temp );
        }

        // Shape the temp sml into the desired Laplacian matrix thingie thing.
        for ( i = 0 ; i < nv ; i++ )
                for ( j = 0 ; j < (nf*3) ; j += 3 )
                        if ( fa[j+0] == i || fa[j+1] == i || fa[j+2] == i )
                        {
                                t1 = ( fa[j+0] != i ) ? j+0 : j+1;
                                t2 = ( fa[j+2] != i ) ? j+2 : j+1;

                                if ( is_zero( i , fa[t1] , temp ) )
                                {
                                        cell = create_cell_t(i,fa[t1],-1.0);
                                        insert_NEW_cell_into_matrix( cell, temp);
                                        increment_non_zero_element(i,i,temp);
                                        nnz++;
                                }

                                if ( is_zero( i , fa[t2] , temp ) )
                                {
                                        cell = create_cell_t(i,fa[t2],-1.0);
                                        insert_NEW_cell_into_matrix( cell, temp);
                                        increment_non_zero_element(i,i,temp);
                                        nnz++;
                                }

                        }

        lplcn = allocate_sparse_matrix_arr(nv,nnz);
        sml_to_sma(temp,lplcn);
        free_sparse_matrix_lst(temp);
        return lplcn;
}

void sml_to_sma( sparse_matrix_lst *source , sparse_matrix_arr *target )
{
        int inserted = 0 , j = 0 , previously;
        cell_t *cell;

        target->colptr[0] = 0;

        while ( j < source->n )
        {
                cell = source->cols[j++];

                previously = inserted;

                while ( cell != NULL )
                {
                        target->values[inserted] = cell->value;
                        target->rowind[inserted] = cell->rowind;
                        cell = cell->col_next;
                        inserted++;
                }

                target->colptr[j] = target->colptr[j-1] + inserted - previously;
        }
}