/*
** This module implements a class encapsulating a Tcl list.
** Author:  Mark Smith, 7B Software, Inc. mark.smith@7bsoftware.com
*/

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <tcl.h>

/*
** A single instance of the following class represents a Tcl list.
*/
class SsTclList {
private:

  int id;                 // List identifier.  Used for debugging.
  Tcl_Interp *interp;     // Tcl interpreter for this list
  Tcl_Obj *pList;         // the Tcl list being managed
  int lastElement;        // Index of the last Tcl element visited 
                          // while traversing the list.
public:
  SsTclList::SsTclList(Tcl_Interp *pInterp);
  SsTclList::SsTclList(Tcl_Interp *pInterp, const char *zStr);
  SsTclList::~SsTclList();
  void SsTclList::set(const char *zStr);
  void SsTclList::append(const char *zStr);
  void SsTclList::append(int num);
  int SsTclList::isnull();
  char *SsTclList::first();
  char *SsTclList::next();
  char *SsTclList::render();
};

static int nextId;  // Next available list ID.  Used in debugging
static int nLists;  // Number of lists currently existing.

SsTclList::SsTclList(Tcl_Interp *pInterp){
  id = nextId++;
  interp = pInterp;
  pList = Tcl_NewListObj(0, 0);
  lastElement = -1;
  Tcl_IncrRefCount(pList);
  ++nLists;
}

/*
** This method initializes the value of the list in pList to the string in zStr.
** If zStr isn't the string representation of a valid Tcl list, 
** then bad things could happen.
*/
SsTclList::SsTclList(Tcl_Interp *pInterp, const char *zStr){
  id = nextId++;
  interp = pInterp;
  pList = Tcl_NewListObj(0, 0);
  lastElement = -1;
  Tcl_IncrRefCount(pList);
  ++nLists;
  set(zStr);
}

SsTclList::~SsTclList(){
  Tcl_DecrRefCount(pList);
  --nLists;
}

/*
** This method sets the value of the list in pList to the string in zStr.
** If zStr isn't the string representation of a valid Tcl list, 
** then bad things could happen.
*/
void SsTclList::set(const char *zStr){
  Tcl_SetStringObj(pList, zStr, -1);
}

/*
** Append zStr to the list
*/
void SsTclList::append(const char *zStr){
  Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(zStr, -1));
}

/*
** Append "num" to the list.
*/
void SsTclList::append(int num){
  Tcl_ListObjAppendElement(interp, pList, Tcl_NewIntObj(num));
}

/*
** Return nonzero if the list contains no elements
*/
int SsTclList::isnull(){
  int objc;
  Tcl_Obj **objv;
  int ret = Tcl_ListObjGetElements(interp, pList, &objc, &objv);
  if( ret!=TCL_OK ){
    return 0;
  }
  return (objc==0);
}

/*
** Return the first element on the list as a character string, or 0 if none
*/
char *SsTclList::first(){
  int objc;
  Tcl_Obj **objv;
  lastElement = 0;
  int ret = Tcl_ListObjGetElements(interp, pList, &objc, &objv);
  if( ret!=TCL_OK ){
    return 0;
  }
  if( objc>lastElement ){
    return Tcl_GetString(objv[lastElement]);
  } else {
    lastElement = -1;
    return 0;
  }
}

/*
** Return the next element on the list, or 0 if none left.
*/
char *SsTclList::next(){
  int objc;
  Tcl_Obj **objv;
  lastElement++;
  int ret = Tcl_ListObjGetElements(interp, pList, &objc, &objv);
  if( ret!=TCL_OK ){
    return 0;
  }
  if( objc>lastElement ){
    return Tcl_GetString(objv[lastElement]);
  } else {
    lastElement = -1;
    return 0;
  }
}

/*
** Render the string representation of the Tcl list
*/
char *SsTclList::render(){
  return Tcl_GetString(pList);
}