//------------------------------------------------------------------------------
// gbkronecker: sparse matrix Kronecker product
//------------------------------------------------------------------------------

// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2021, All Rights Reserved.
// SPDX-License-Identifier: GPL-3.0-or-later

//------------------------------------------------------------------------------

// gbkronecker is an interface to GrB_kronecker

// Usage:

// C = gbkronecker (op, A, B)
// C = gbkronecker (op, A, B, desc)
// C = gbkronecker (Cin, accum, op, A, B, desc)
// C = gbkronecker (Cin, M, op, A, B, desc)
// C = gbkronecker (Cin, M, accum, op, A, B, desc)

// If Cin is not present then it is implicitly a matrix with no entries, of the
// right size (which depends on A, B, and the descriptor).

#include "gb_matlab.h"

#define USAGE "usage: C = GrB.kronecker (Cin, M, accum, op, A, B, desc)"

void mexFunction
(
    int nargout,
    mxArray *pargout [ ],
    int nargin,
    const mxArray *pargin [ ]
)
{

    //--------------------------------------------------------------------------
    // check inputs
    //--------------------------------------------------------------------------

    gb_usage (nargin >= 3 && nargin <= 7 && nargout <= 2, USAGE) ;

    //--------------------------------------------------------------------------
    // find the arguments
    //--------------------------------------------------------------------------

    mxArray *Matrix [4], *String [2], *Cell [2] ;
    base_enum_t base ;
    kind_enum_t kind ;
    GxB_Format_Value fmt ;
    int nmatrices, nstrings, ncells, sparsity ;
    GrB_Descriptor desc ;
    gb_get_mxargs (nargin, pargin, USAGE, Matrix, &nmatrices, String, &nstrings,
        Cell, &ncells, &desc, &base, &kind, &fmt, &sparsity) ;

    CHECK_ERROR (nmatrices < 2 || nstrings < 1 || ncells > 0, USAGE) ;

    //--------------------------------------------------------------------------
    // get the matrices
    //--------------------------------------------------------------------------

    GrB_Type atype, btype, ctype = NULL ;
    GrB_Matrix C = NULL, M = NULL, A, B ;

    if (nmatrices == 2)
    { 
        A = gb_get_shallow (Matrix [0]) ;
        B = gb_get_shallow (Matrix [1]) ;
    }
    else if (nmatrices == 3)
    { 
        C = gb_get_deep    (Matrix [0]) ;
        A = gb_get_shallow (Matrix [1]) ;
        B = gb_get_shallow (Matrix [2]) ;
    }
    else // if (nmatrices == 4)
    { 
        C = gb_get_deep    (Matrix [0]) ;
        M = gb_get_shallow (Matrix [1]) ;
        A = gb_get_shallow (Matrix [2]) ;
        B = gb_get_shallow (Matrix [3]) ;
    }

    OK (GxB_Matrix_type (&atype, A)) ;
    OK (GxB_Matrix_type (&btype, B)) ;
    if (C != NULL)
    { 
        OK (GxB_Matrix_type (&ctype, C)) ;
    }

    //--------------------------------------------------------------------------
    // get the operators
    //--------------------------------------------------------------------------

    GrB_BinaryOp accum = NULL, op ;

    if (nstrings == 1)
    { 
        op    = gb_mxstring_to_binop (String [0], atype, btype) ;
    }
    else 
    { 
        // if accum appears, then Cin must also appear
        CHECK_ERROR (C == NULL, USAGE) ;
        accum = gb_mxstring_to_binop (String [0], ctype, ctype) ;
        op    = gb_mxstring_to_binop (String [1], atype, btype) ;
    }

    //--------------------------------------------------------------------------
    // construct C if not present on input
    //--------------------------------------------------------------------------

    // If C is NULL, then it is not present on input.
    // Construct C of the right size and type.

    if (C == NULL)
    {
        // get the descriptor contents to determine if A and B are transposed
        GrB_Desc_Value in0, in1 ;
        OK (GxB_Desc_get (desc, GrB_INP0, &in0)) ;
        OK (GxB_Desc_get (desc, GrB_INP1, &in1)) ;
        bool A_transpose = (in0 == GrB_TRAN) ;
        bool B_transpose = (in1 == GrB_TRAN) ;

        // get the size of A and B
        GrB_Index anrows, ancols, bnrows, bncols ;
        if (A_transpose)
        { 
            OK (GrB_Matrix_nrows (&ancols, A)) ;
            OK (GrB_Matrix_ncols (&anrows, A)) ;
        }
        else
        { 
            OK (GrB_Matrix_nrows (&anrows, A)) ;
            OK (GrB_Matrix_ncols (&ancols, A)) ;
        }
        if (B_transpose)
        { 
            OK (GrB_Matrix_nrows (&bncols, B)) ;
            OK (GrB_Matrix_ncols (&bnrows, B)) ;
        }
        else
        { 
            OK (GrB_Matrix_nrows (&bnrows, B)) ;
            OK (GrB_Matrix_ncols (&bncols, B)) ;
        }

        // determine the size of C
        GrB_Index cnrows = anrows * bnrows ;
        GrB_Index cncols = ancols * bncols ;

        // use the ztype of the op as the type of C
        OK (GxB_BinaryOp_ztype (&ctype, op)) ;

        // create the matrix C and set its format and sparsity
        fmt = gb_get_format (cnrows, cncols, A, B, fmt) ;
        sparsity = gb_get_sparsity (A, B, sparsity) ;
        C = gb_new (ctype, cnrows, cncols, fmt, sparsity) ;
    }

    //--------------------------------------------------------------------------
    // compute C<M> += kron (A,B)
    //--------------------------------------------------------------------------

    OK1 (C, GrB_Matrix_kronecker_BinaryOp (C, M, accum, op, A, B, desc)) ;

    //--------------------------------------------------------------------------
    // free shallow copies
    //--------------------------------------------------------------------------

    OK (GrB_Matrix_free (&M)) ;
    OK (GrB_Matrix_free (&A)) ;
    OK (GrB_Matrix_free (&B)) ;
    OK (GrB_Descriptor_free (&desc)) ;

    //--------------------------------------------------------------------------
    // export the output matrix C back to MATLAB
    //--------------------------------------------------------------------------

    pargout [0] = gb_export (&C, kind) ;
    pargout [1] = mxCreateDoubleScalar (kind) ;
    GB_WRAPUP ;
}