#include <petsc/private/snesimpl.h>             /*I   "petscsnes.h"   I*/

typedef struct {PetscErrorCode (*solve)(SNES,Vec);void *ctx;} SNES_Shell;

/*@C
   SNESShellSetSolve - Sets routine to apply as solver

   Logically Collective on SNES

   Input Parameters:
+  snes - the nonlinear solver context
-  apply - the application-provided solver routine

   Calling sequence of solve:
.vb
   PetscErrorCode apply (SNES snes,Vec xout)
.ve

+  snes - the preconditioner, get the application context with SNESShellGetContext()
-  xout - solution vector

   Notes:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: SNESSHELL, SNESShellSetContext(), SNESShellGetContext()
@*/
PetscErrorCode  SNESShellSetSolve(SNES snes,PetscErrorCode (*solve)(SNES,Vec))
{
  PetscFunctionBegin;
  PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
  PetscTryMethod(snes,"SNESShellSetSolve_C",(SNES,PetscErrorCode (*)(SNES,Vec)),(snes,solve));
  PetscFunctionReturn(0);
}

PetscErrorCode SNESReset_Shell(SNES snes)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

PetscErrorCode SNESDestroy_Shell(SNES snes)
{
  PetscFunctionBegin;
  PetscCall(SNESReset_Shell(snes));
  PetscCall(PetscFree(snes->data));
  PetscFunctionReturn(0);
}

PetscErrorCode SNESSetUp_Shell(SNES snes)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

PetscErrorCode SNESSetFromOptions_Shell(PetscOptionItems *PetscOptionsObject,SNES snes)
{
  PetscFunctionBegin;
  PetscCall(PetscOptionsHead(PetscOptionsObject,"SNES Shell options"));
  PetscFunctionReturn(0);
}

PetscErrorCode SNESView_Shell(SNES snes, PetscViewer viewer)
{
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

/*@
    SNESShellGetContext - Returns the user-provided context associated with a shell SNES

    Not Collective

    Input Parameter:
.   snes - should have been created with SNESSetType(snes,SNESSHELL);

    Output Parameter:
.   ctx - the user provided context

    Level: advanced

    Notes:
    This routine is intended for use within various shell routines

.seealso: SNESCreateShell(), SNESShellSetContext()
@*/
PetscErrorCode  SNESShellGetContext(SNES snes,void *ctx)
{
  PetscBool      flg;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
  PetscValidPointer(ctx,2);
  PetscCall(PetscObjectTypeCompare((PetscObject)snes,SNESSHELL,&flg));
  if (!flg) *(void**)ctx = NULL;
  else      *(void**)ctx = ((SNES_Shell*)(snes->data))->ctx;
  PetscFunctionReturn(0);
}

/*@
    SNESShellSetContext - sets the context for a shell SNES

   Logically Collective on SNES

    Input Parameters:
+   snes - the shell SNES
-   ctx - the context

   Level: advanced

   Fortran Notes:
    The context can only be an integer or a PetscObject
      unfortunately it cannot be a Fortran array or derived type.

.seealso: SNESCreateShell(), SNESShellGetContext()
@*/
PetscErrorCode  SNESShellSetContext(SNES snes,void *ctx)
{
  SNES_Shell     *shell = (SNES_Shell*)snes->data;
  PetscBool      flg;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
  PetscCall(PetscObjectTypeCompare((PetscObject)snes,SNESSHELL,&flg));
  if (flg) shell->ctx = ctx;
  PetscFunctionReturn(0);
}

PetscErrorCode SNESSolve_Shell(SNES snes)
{
  SNES_Shell     *shell = (SNES_Shell*) snes->data;

  PetscFunctionBegin;
  PetscCheck(shell->solve,PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"Must call SNESShellSetSolve() first");
  snes->reason = SNES_CONVERGED_ITS;
  PetscCall((*shell->solve)(snes,snes->vec_sol));
  PetscFunctionReturn(0);
}

PetscErrorCode  SNESShellSetSolve_Shell(SNES snes,PetscErrorCode (*solve)(SNES,Vec))
{
  SNES_Shell *shell = (SNES_Shell*)snes->data;

  PetscFunctionBegin;
  shell->solve = solve;
  PetscFunctionReturn(0);
}

/*MC
  SNESSHELL - a user provided nonlinear solver

   Level: advanced

.seealso: SNESCreate(), SNES, SNESSetType(), SNESType (for list of available types)
M*/

PETSC_EXTERN PetscErrorCode SNESCreate_Shell(SNES snes)
{
  SNES_Shell     *shell;

  PetscFunctionBegin;
  snes->ops->destroy        = SNESDestroy_Shell;
  snes->ops->setup          = SNESSetUp_Shell;
  snes->ops->setfromoptions = SNESSetFromOptions_Shell;
  snes->ops->view           = SNESView_Shell;
  snes->ops->solve          = SNESSolve_Shell;
  snes->ops->reset          = SNESReset_Shell;

  snes->usesksp = PETSC_FALSE;
  snes->usesnpc = PETSC_FALSE;

  snes->alwayscomputesfinalresidual = PETSC_FALSE;

  PetscCall(PetscNewLog(snes,&shell));
  snes->data = (void*) shell;
  PetscCall(PetscObjectComposeFunction((PetscObject)snes,"SNESShellSetSolve_C",SNESShellSetSolve_Shell));
  PetscFunctionReturn(0);
}