// Copyright (c) 2017-2026, Lawrence Livermore National Security, LLC and other CEED contributors.
// All Rights Reserved. See the top-level LICENSE and NOTICE files for details.
//
// SPDX-License-Identifier: BSD-2-Clause
//
// This file is part of CEED:  http://github.com/ceed

#include <ceed/types.h>

CEED_QFUNCTION(setup)(void *ctx, const CeedInt Q, const CeedScalar *const *in, CeedScalar *const *out) {
  // At every quadrature point, compute qw/det(J).adj(J).adj(J)^T and store
  // the symmetric part of the result.

  // in[0] is Jacobians with shape [2, nc=2, Q]
  // in[1] is quadrature weights, size (Q)
  const CeedScalar *J = in[0], *qw = in[1];

  // out[0] is qdata, size (Q)
  CeedScalar *qd = out[0];

  // Quadrature point loop
  for (CeedInt i = 0; i < Q; i++) {
    // J: 0 2   qd: 0 2   adj(J):  J22 -J12
    //    1 3       2 1           -J21  J11
    const CeedScalar J11 = J[i + Q * 0];
    const CeedScalar J21 = J[i + Q * 1];
    const CeedScalar J12 = J[i + Q * 2];
    const CeedScalar J22 = J[i + Q * 3];
    const CeedScalar w   = qw[i] / (J11 * J22 - J21 * J12);
    qd[i + Q * 0]        = w * (J12 * J12 + J22 * J22);
    qd[i + Q * 2]        = w * (J11 * J11 + J21 * J21);
    qd[i + Q * 1]        = -w * (J11 * J12 + J21 * J22);
  }

  return 0;
}

CEED_QFUNCTION(diff)(void *ctx, const CeedInt Q, const CeedScalar *const *in, CeedScalar *const *out) {
  CeedInt num_comp = *(CeedInt *)ctx;
  // in[0] is gradient u, shape [2, nc=1, Q]
  // in[1] is quadrature data, size (3*Q)
  const CeedScalar *du = in[0], *qd = in[1];

  // out[0] is output to multiply against gradient v, shape [2, nc=1, Q]
  CeedScalar *dv = out[0];

  // Quadrature point loop
  for (CeedInt i = 0; i < Q; i++) {
    for (CeedInt c = 0; c < num_comp; c++) {
      const CeedScalar du0 = du[i + Q * (2 * c + 0)];
      const CeedScalar du1 = du[i + Q * (2 * c + 1)];

      dv[i + Q * (2 * c + 0)] = qd[i + Q * 0] * du0 + qd[i + Q * 2] * du1;
      dv[i + Q * (2 * c + 1)] = qd[i + Q * 2] * du0 + qd[i + Q * 1] * du1;
    }
  }

  return 0;
}