static const char help[] = "Tests PETSc -- Mathematica connection\n";
#include <petscksp.h>
#include <mathlink.h>

typedef enum {
  MATHEMATICA_LINK_CREATE,
  MATHEMATICA_LINK_CONNECT,
  MATHEMATICA_LINK_LAUNCH
} LinkMode;

static PetscErroCode setupConnection(MLENV *env, MLINK *link, const char *linkhost, LinkMode linkmode) {
  int   argc = 5;
  char *argv[5];
  char  hostname[256];
  long  lerr;
  int   ierr;

  PetscFunctionBegin;
  /* Link name */
  argv[0] = "-linkname";
  argv[1] = "8001";

  /* Link host */
  argv[2] = "-linkhost";
  if (!linkhost) {
    PetscCall(PetscGetHostName(hostname, sizeof(hostname)));
    argv[3] = hostname;
  } else argv[3] = (char *)linkhost;

  /* Link mode */
  switch (linkmode) {
  case MATHEMATICA_LINK_CREATE: argv[4] = "-linkcreate"; break;
  case MATHEMATICA_LINK_CONNECT: argv[4] = "-linkconnect"; break;
  case MATHEMATICA_LINK_LAUNCH: argv[4] = "-linklaunch"; break;
  }

  *env = MLInitialize(0);
  for (lerr = 0; lerr < argc; lerr++) printf("argv[%ld] = %s\n", lerr, argv[lerr]);
  *link = MLOpenInEnv(*env, argc, argv, &lerr);
  printf("lerr = %ld\n", lerr);
  PetscFunctionReturn(0);
}

static PetscErrorCode printIndent(int indent) {
  int i;

  PetscFunctionBegin;
  for (i = 0; i < indent; i++) printf(" ");
  PetscFunctionReturn(0);
}

static PetscErrorCode processPacket(MLINK link, int indent, int *result) {
  static int isHead    = 0;
  int        tokenType = MLGetNext(link);
  int        ierr;

  PetscFunctionBegin;
  PetscCall(printIndent(indent));
  switch (tokenType) {
  case MLTKFUNC: {
    long numArguments;
    int  arg;

    printf("Function:\n");
    MLGetArgCount(link, &numArguments);
    /* Process head */
    printf("  Head:\n");
    isHead = 1;
    PetscCall(processPacket(link, indent + 4, result));
    if (*result) PetscFunctionReturn(0);
    isHead = 0;
    /* Process arguments */
    printf("  Arguments:\n");
    for (arg = 0; arg < numArguments; arg++) PetscCall(processPacket(link, indent + 4));
  } break;
  case MLTKSYM: {
    const char *symbol;

    MLGetSymbol(link, &symbol);
    printf("Symbol: %s\n", symbol);
    if (isHead && !strcmp(symbol, "Shutdown")) {
      MLDisownSymbol(link, symbol);
      *result = 2;
      PetscFunctionReturn(0);
    }
    MLDisownSymbol(link, symbol);
  } break;
  case MLTKINT: {
    int i;

    MLGetInteger(link, &i);
    printf("Integer: %d\n", i);
  } break;
  case MLTKREAL: {
    double r;

    MLGetReal(link, &r);
    printf("Real: %g\n", r);
  } break;
  case MLTKSTR: {
    const char *string;

    MLGetString(link, &string);
    printf("String: %s\n", string);
    MLDisownString(link, string);
  } break;
  default:
    printf("Unknown code %d\n", tokenType);
    MLClearError(link);
    fprintf(stderr, "ERROR: %s\n", (char *)MLErrorMessage(link));
    *result = 1;
    PetscFunctionReturn(0);
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode processPackets(MLINK link) {
  int packetType;
  int loop   = 1;
  int errors = 0;
  int err, result;

  PetscFunctionBegin;
  while (loop) {
    while ((packetType = MLNextPacket(link)) && (packetType != RETURNPKT)) {
      switch (packetType) {
      case BEGINDLGPKT: printf("Begin dialog packet\n"); break;
      case CALLPKT: printf("Call packet\n"); break;
      case DISPLAYPKT: printf("Display packet\n"); break;
      case DISPLAYENDPKT: printf("Display end packet\n"); break;
      case ENDDLGPKT: printf("End dialog packet\n"); break;
      case ENTERTEXTPKT: printf("Enter text packet\n"); break;
      case ENTEREXPRPKT: printf("Enter expression packet\n"); break;
      case EVALUATEPKT: printf("Evaluate packet\n"); break;
      case INPUTPKT: printf("Input packet\n"); break;
      case INPUTNAMEPKT: printf("Input name packet\n"); break;
      case INPUTSTRPKT: printf("Input string packet\n"); break;
      case MENUPKT: printf("Menu packet\n"); break;
      case MESSAGEPKT: printf("Message packet\n"); break;
      case OUTPUTNAMEPKT: printf("Output name packet\n"); break;
      case RESUMEPKT: printf("Resume packet\n"); break;
      case RETURNTEXTPKT: printf("Return text packet\n"); break;
      case RETURNEXPRPKT: printf("Return expression packet\n"); break;
      case SUSPENDPKT: printf("Suspend packet\n"); break;
      case SYNTAXPKT: printf("Syntax packet\n"); break;
      case TEXTPKT: printf("Text packet\n"); break;
      }
      MLNewPacket(link);
    }

    /* Got a Return packet */
    if (!packetType) {
      MLClearError(link);
      printf("ERROR: %s\n", (char *)MLErrorMessage(link));
      errors++;
    } else if (packetType == RETURNPKT) {
      PetscCall(processPacket(link, result));
      if (result == 2) loop = 0;
    } else {
      fprintf(stderr, "Invalid packet type %d\n", packetType);
      loop = 0;
    }
    if (errors > 10) loop = 0;
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode cleanupConnection(MLENV env, MLINK link) {
  PetscFunctionBegin;
  MLClose(link);
  MLDeinitialize(env);
  PetscFunctionReturn(0);
}

int main(int argc, char *argv[]) {
  MLENV env;
  MLINK link;

  PetscCall(PetscInitialize(&argc, &argv, NULL, help));
  PetscCall(setupConnection(&env, &link, "192.168.119.1", MATHEMATICA_LINK_CONNECT));
  PetscCall(processPackets(link));
  PetscCall(cleanupConnection(env, link));
  PetscCall(PetscFinalize());
  return 0;
}