/*
** The implementation of the TH core. This file contains the parser, and
** the implementation of the interface in th.h.
*/

#include "config.h"
#include "th.h"
#include <string.h>
#include <assert.h>

typedef struct Th_Command   Th_Command;
typedef struct Th_Frame     Th_Frame;
typedef struct Th_Variable  Th_Variable;

/*
** Interpreter structure.
*/
struct Th_Interp {
  Th_Vtab *pVtab;     /* Copy of the argument passed to Th_CreateInterp() */
  char *zResult;      /* Current interpreter result (Th_Malloc()ed) */
  int nResult;        /* number of bytes in zResult */
  Th_Hash *paCmd;     /* Table of registered commands */
  Th_Frame *pFrame;   /* Current execution frame */
  int isListMode;     /* True if thSplitList() should operate in "list" mode */
};

/*

** Each stack frame (variable scope) is represented by an instance
** of this structure. Variable values set using the Th_SetVar command
** are stored in the Th_Frame.paVar hash table member of the associated
** stack frame object.
**
** When an interpreter is created, a single Th_Frame structure is also
** allocated - the global variable scope. Th_Interp.pFrame (the current
** interpreter frame) is initialised to point to this Th_Frame. It is
** not deleted for the lifetime of the interpreter (because the global
** frame never goes out of scope).
**
** New stack frames are created by the Th_InFrame() function. Before
** invoking its callback function, Th_InFrame() allocates a new Th_Frame
** structure with pCaller set to the current frame (Th_Interp.pFrame),
** and sets the current frame to the new frame object. After the callback
** has been invoked, the allocated Th_Frame is deleted and the value
** of the current frame pointer restored.
**
** By default, the Th_SetVar(), Th_UnsetVar() and Th_GetVar() functions
** access variable values in the current frame. If they need to access
** the global frame, they do so by traversing the pCaller pointer list.
** Likewise, the Th_LinkVar() function uses the pCaller pointers to
** link to variables located in the global or other stack frames.
*/
struct Th_Frame {
  Th_Hash *paVar;               /* Variables defined in this scope */
  Th_Frame *pCaller;            /* Calling frame */
};

** a hash table mapping between array key name (a th1 string) and
** a pointer to the Th_Variable structure holding the scalar
** value.
*/
struct Th_Variable {
  int nRef;                   /* Number of references to this structure */
  int nData;                  /* Number of bytes at Th_Variable.zData */
  char *zData;                /* Data for scalar variables */
  Th_Hash *pHash;             /* Data for array variables */
};

/*
** Hash table API:
*/
#define TH_HASHSIZE 257

static void thPopFrame(Th_Interp*);

static void thFreeVariable(Th_HashEntry*, void*);
static void thFreeCommand(Th_HashEntry*, void*);

/*
** The following are used by both the expression and language parsers.
** Given that the start of the input string (z, n) is a language
** construct of the relevant type (a command enclosed in [], an escape
** sequence etc.), these functions determine the number of bytes
** of the input consumed by the construct. For example:
**
**   int nByte;
**   thNextCommand(interp, "[expr $a+1] $nIter", 18, &nByte);
**
** results in variable nByte being set to 11. Or,
**
**   thNextVarname(interp, "$a+1", 4, &nByte);
**
** results in nByte being set to 2.
*/
static int thNextCommand(Th_Interp*, const char *z, int n, int *pN);
static int thNextEscape (Th_Interp*, const char *z, int n, int *pN);
static int thNextVarname(Th_Interp*, const char *z, int n, int *pN);
static int thNextNumber (Th_Interp*, const char *z, int n, int *pN);
static int thNextSpace  (Th_Interp*, const char *z, int n, int *pN);

/*
** Given that the input string (z, n) contains a language construct of
** the relevant type (a command enclosed in [], an escape sequence
** like "\xFF" or a variable reference like "${varname}", perform
** substitution on the string and store the resulting string in
** the interpreter result.
*/
static int thSubstCommand(Th_Interp*, const char *z, int n);
static int thSubstEscape (Th_Interp*, const char *z, int n);
static int thSubstVarname(Th_Interp*, const char *z, int n);

/*
** Given that there is a th1 word located at the start of the input
** string (z, n), determine the length in bytes of that word. If the
** isCmd argument is non-zero, then an unescaped ";" byte not
** located inside of a block or quoted string is considered to mark
** the end of the word.
*/
static int thNextWord(Th_Interp*, const char *z, int n, int *pN, int isCmd);

/*
** Perform substitution on the word contained in the input string (z, n).
** Store the resulting string in the interpreter result.

/*
** Append nAdd bytes of content copied from zAdd to the end of buffer
** pBuffer. If there is not enough space currently allocated, resize
** the allocation to make space.
*/
static int thBufferWrite(
  Th_Interp *interp,
  Buffer *pBuffer,
  const char *zAdd,
  int nAdd
){
  int nReq;

  if( nAdd<0 ){
    nAdd = th_strlen(zAdd);
  }

  Th_Frame *pFrame = interp->pFrame;
  Th_HashIterate(interp, pFrame->paVar, thFreeVariable, (void *)interp);
  Th_HashDelete(interp, pFrame->paVar);
  interp->pFrame = pFrame->pCaller;
}

/*
** The first part of the string (zInput,nInput) contains an escape
** sequence. Set *pnEscape to the number of bytes in the escape sequence.
** If there is a parse error, return TH_ERROR and set the interpreter
** result to an error message. Otherwise return TH_OK.
*/
static int thNextEscape(
  Th_Interp *interp,
  const char *zInput,
  int nInput,
  int *pnEscape
){
  int i = 2;

  assert(nInput>0);
  assert(zInput[0]=='\\');

  }
  *pnEscape = i;
  return TH_OK;
}

/*
** The first part of the string (zInput,nInput) contains a variable
** reference. Set *pnVarname to the number of bytes in the variable
** reference. If there is a parse error, return TH_ERROR and set the
** interpreter result to an error message. Otherwise return TH_OK.
*/
int thNextVarname(
  Th_Interp *interp,
  const char *zInput,
  int nInput,
  int *pnVarname
){
  int i;

  assert(nInput>0);
  assert(zInput[0]=='$');

  *pnVarname = i;
  return TH_OK;
}

/*
** The first part of the string (zInput,nInput) contains a command
** enclosed in a "[]" block. Set *pnCommand to the number of bytes in
** the variable reference. If there is a parse error, return TH_ERROR
** and set the interpreter result to an error message. Otherwise return
** TH_OK.
*/
int thNextCommand(
  Th_Interp *interp,
  const char *zInput,
  int nInput,
  int *pnCommand
){
  int nBrace = 0;
  int nSquare = 0;
  int i;

  assert(nInput>0);

  *pnCommand = i;

  return TH_OK;
}

/*
** Set *pnSpace to the number of whitespace bytes at the start of
** input string (zInput, nInput). Always return TH_OK.
*/
int thNextSpace(
  Th_Interp *interp,
  const char *zInput,
  int nInput,
  int *pnSpace
){
  int i;
  for(i=0; i<nInput && th_isspace(zInput[i]); i++);
  *pnSpace = i;
  return TH_OK;
}

/*
** The first byte of the string (zInput,nInput) is not white-space.
** Set *pnWord to the number of bytes in the th1 word that starts
** with this byte. If a complete word cannot be parsed or some other
** error occurs, return TH_ERROR and set the interpreter result to
** an error message. Otherwise return TH_OK.
**
** If the isCmd argument is non-zero, then an unescaped ";" byte not
** located inside of a block or quoted string is considered to mark
** the end of the word.
*/
static int thNextWord(
  Th_Interp *interp,
  const char *zInput,
  int nInput,
  int *pnWord,
  int isCmd
){
  int iEnd = 0;

  assert( !th_isspace(zInput[0]) );

  assert(nWord>=2);
  assert(zWord[0]=='[' && zWord[nWord-1]==']');
  return thEvalLocal(interp, &zWord[1], nWord-2);
}

/*
** The input string (zWord, nWord) contains a th1 variable reference
** (a '$' byte followed by a variable name). Perform substitution on
** the input string and store the resulting string in the interpreter
** result.
*/
static int thSubstVarname(
  Th_Interp *interp,
  const char *zWord,
  int nWord
){

    }
  }
  return Th_GetVar(interp, &zWord[1], nWord-1);
}

/*
** The input string (zWord, nWord) contains a th1 escape sequence.
** Perform substitution on the input string and store the resulting
** string in the interpreter result.
*/
static int thSubstEscape(
  Th_Interp *interp,
  const char *zWord,
  int nWord
){

  Th_SetResult(interp, &c, 1);
  return TH_OK;
}

/*
** The input string (zWord, nWord) contains a th1 word. Perform
** substitution on the input string and store the resulting
** string in the interpreter result.
*/
static int thSubstWord(
  Th_Interp *interp,
  const char *zWord,
  int nWord
){

      int nGet;

      int (*xGet)(Th_Interp *, const char*, int, int *) = 0;
      int (*xSubst)(Th_Interp *, const char*, int) = 0;

      switch( zWord[i] ){
        case '\\':
          xGet = thNextEscape; xSubst = thSubstEscape;
          break;
        case '[':
          if( !interp->isListMode ){
            xGet = thNextCommand; xSubst = thSubstCommand;
            break;
          }
        case '$':
          if( !interp->isListMode ){
            xGet = thNextVarname; xSubst = thSubstVarname;
            break;
          }
        default: {
          thBufferWrite(interp, &output, &zWord[i], 1);
          continue; /* Go to the next iteration of the for(...) loop */
        }
      }

/*
** Return true if one of the following is true of the buffer pointed
** to by zInput, length nInput:
**
**   + It is empty, or
**   + It contains nothing but white-space, or
**   + It contains no non-white-space characters before the first
**     newline character.
**
** Otherwise return false.
*/
static int thEndOfLine(const char *zInput, int nInput){
  int i;
  for(i=0; i<nInput && zInput[i]!='\n' && th_isspace(zInput[i]); i++);

**     Th_SplitList(interp, zList, nList, &argv, &argl, &argc);
**
**     // Free all memory allocated by Th_SplitList(). The arrays pointed
**     // to by argv and argl are invalidated by this call.
**     //
**     Th_Free(interp, argv);
**
*/
static int thSplitList(
  Th_Interp *interp,      /* Interpreter context */
  const char *zList,      /* Pointer to buffer containing input list */
  int nList,              /* Size of buffer pointed to by zList */
  char ***pazElem,        /* OUT: Array of list elements */
  int **panElem,          /* OUT: Lengths of each list element */
  int *pnCount            /* OUT: Number of list elements */
){
  int rc = TH_OK;

  Buffer strbuf;
  Buffer lenbuf;

    }
  }
  assert((lenbuf.nBuf/sizeof(int))==nCount);

  assert((pazElem && panElem) || (!pazElem && !panElem));
  if( pazElem && rc==TH_OK ){
    int i;
    char *zElem;
    int *anElem;
    char **azElem = Th_Malloc(interp,
      sizeof(char*) * nCount +       /* azElem */
      sizeof(int) * nCount +         /* anElem */
      strbuf.nBuf                    /* space for list element strings */
    );
    anElem = (int *)&azElem[nCount];
    zElem = (char *)&anElem[nCount];
    memcpy(anElem, lenbuf.zBuf, lenbuf.nBuf);
    memcpy(zElem, strbuf.zBuf, strbuf.nBuf);
    for(i=0; i<nCount;i++){
      azElem[i] = zElem;
      zElem += (anElem[i] + 1);
    }
    *pazElem = azElem;
    *panElem = anElem;
  }
  if( pnCount ){
    *pnCount = nCount;
  }

 finish:
  thBufferFree(interp, &strbuf);
  thBufferFree(interp, &lenbuf);
  return rc;
}

/*

      /* Call the command procedure. */
      if( rc==TH_OK ){
        Th_Command *p = (Th_Command *)(pEntry->pData);
        const char **azArg = (const char **)argv;
        rc = p->xProc(interp, p->pContext, argc, azArg, argl);
      }

      /* If an error occurred, add this command to the stack trace report. */
      if( rc==TH_ERROR ){
        char *zRes;
        int nRes;
        char *zStack = 0;
        int nStack = 0;

        zRes = Th_TakeResult(interp, &nRes);
        if( TH_OK==Th_GetVar(interp, (char *)"::th_stack_trace", -1) ){
          zStack = Th_TakeResult(interp, &nStack);
        }
        Th_ListAppend(interp, &zStack, &nStack, zFirst, zInput-zFirst);
        Th_SetVar(interp, (char *)"::th_stack_trace", -1, zStack, nStack);
        Th_SetResult(interp, zRes, nRes);

** Th_Frame structure. If unsuccessful (no such frame), return 0 and
** leave an error message in the interpreter result.
**
** Argument iFrame is interpreted as follows:
**
**   * If iFrame is 0, this means the current frame.
**
**   * If iFrame is negative, then the nth frame up the stack, where
**     n is the absolute value of iFrame. A value of -1 means the
**     calling procedure.
**
**   * If iFrame is +ve, then the nth frame from the bottom of the
**     stack. An iFrame value of 1 means the toplevel (global) frame.
*/
static Th_Frame *getFrame(Th_Interp *interp, int iFrame){
  Th_Frame *p = interp->pFrame;
  int i;
  if( iFrame>0 ){
    for(i=0; p; i++){

  return p;
}


/*
** Evaluate th1 script (zProgram, nProgram) in the frame identified by
** argument iFrame. Leave either an error message or a result in the
** interpreter result and return a th1 error code (TH_OK, TH_ERROR,
** TH_RETURN, TH_CONTINUE or TH_BREAK).
*/
int Th_Eval(Th_Interp *interp, int iFrame, const char *zProgram, int nProgram){
  int rc = TH_OK;
  Th_Frame *pSavedFrame = interp->pFrame;

  /* Set Th_Interp.pFrame to the frame that this script is to be
  ** evaluated in. The current frame is saved in pSavedFrame and will
  ** be restored before this function returns.
  */
  interp->pFrame = getFrame(interp, iFrame);

  if( !interp->pFrame ){
    rc = TH_ERROR;
  }else{
    int nInput = nProgram;

    if( nInput<0 ){
      nInput = th_strlen(zProgram);
    }
    rc = thEvalLocal(interp, zProgram, nInput);
  }

  interp->pFrame = pSavedFrame;

** array variable. If the variable is a scalar, *pzInner is set to 0.
** If it is an array variable, (*pzInner, *pnInner) is set to the
** array key name.
*/
static int thAnalyseVarname(
  const char *zVarname,
  int nVarname,
  const char **pzOuter,      /* OUT: Pointer to scalar/array name */
  int *pnOuter,              /* OUT: Number of bytes at *pzOuter */
  const char **pzInner,      /* OUT: Pointer to array key (or null) */
  int *pnInner,              /* OUT: Number of bytes at *pzInner */
  int *pisGlobal             /* OUT: Set to true if this is a global ref */
){
  const char *zOuter = zVarname;
  int nOuter;
  const char *zInner = 0;
  int nInner = 0;

  *pnInner = nInner;
  *pisGlobal = isGlobal;
  return TH_OK;
}

/*
** Input string (zVar, nVar) contains a variable name. This function locates
** the Th_Variable structure associated with the named variable. The
** variable name may be a global or local scalar or array variable
**
** If the create argument is non-zero and the named variable does not exist
** it is created. Otherwise, an error is left in the interpreter result
** and NULL returned.
**
** If the arrayok argument is false and the named variable is an array,
** an error is left in the interpreter result and NULL returned. If
** arrayok is true an array name is Ok.
*/
static Th_Variable *thFindValue(
  Th_Interp *interp,
  const char *zVar,      /* Pointer to variable name */
  int nVar,              /* Number of bytes at nVar */
  int create,            /* If true, create the variable if not found */
  int arrayok,           /* If true, an array is Ok. Otherwise array==error */
  int noerror            /* If false, set interpreter result to error message */
){
  const char *zOuter;
  int nOuter;

  thAnalyseVarname(zVar, nVar, &zOuter, &nOuter, &zInner, &nInner, &isGlobal);
  if( isGlobal ){
    while( pFrame->pCaller ) pFrame = pFrame->pCaller;
  }

  pEntry = Th_HashFind(interp, pFrame->paVar, zOuter, nOuter, create);
  assert(pEntry || create<=0);
  if( !pEntry ){
    goto no_such_var;
  }

  pValue = (Th_Variable *)pEntry->pData;
  if( !pValue ){
    assert(create);

  if( !noerror ){
    Th_ErrorMessage(interp, "no such variable:", zVar, nVar);
  }
  return 0;
}

/*
** String (zVar, nVar) must contain the name of a scalar variable or
** array member. Look up the variable, store its current value in
** the interpreter result and return TH_OK.
**
** If the named variable does not exist, return TH_ERROR and leave
** an error message in the interpreter result.
*/
int Th_GetVar(Th_Interp *interp, const char *zVar, int nVar){
  Th_Variable *pValue;

** array member. If the variable does not exist it is created. The
** variable is set to the value supplied in string (zValue, nValue).
**
** If (zVar, nVar) refers to an existing array, TH_ERROR is returned
** and an error message left in the interpreter result.
*/
int Th_SetVar(
  Th_Interp *interp,
  const char *zVar,
  int nVar,
  const char *zValue,
  int nValue
){
  Th_Variable *pValue;

  pValue = thFindValue(interp, zVar, nVar, 1, 0, 0);

/*
** Create a variable link so that accessing variable (zLocal, nLocal) is
** the same as accessing variable (zLink, nLink) in stack frame iFrame.
*/
int Th_LinkVar(
  Th_Interp *interp,                 /* Interpreter */
  const char *zLocal, int nLocal,    /* Local varname */
  int iFrame,                        /* Stack frame of linked var */
  const char *zLink, int nLink       /* Linked varname */
){
  Th_Frame *pSavedFrame = interp->pFrame;
  Th_Frame *pFrame;
  Th_HashEntry *pEntry;
  Th_Variable *pValue;

  pFrame = getFrame(interp, iFrame);

  Th_Variable *pValue;

  pValue = thFindValue(interp, zVar, nVar, 0, 1, 0);
  if( !pValue ){
    return TH_ERROR;
  }

  if( pValue->zData ){
    Th_Free(interp, pValue->zData);
    pValue->zData = 0;
  }
  if( pValue->pHash ){
    Th_HashIterate(interp, pValue->pHash, thFreeVariable, (void *)interp);
    Th_HashDelete(interp, pValue->pHash);
    pValue->pHash = 0;
  }

  thFindValue(interp, zVar, nVar, -1, 1, 1); /* Finally, delete from frame */
  return TH_OK;
}

/*
** Return an allocated buffer containing a copy of string (z, n). The
** caller is responsible for eventually calling Th_Free() to free
** the returned buffer.

*/
int Th_ErrorMessage(Th_Interp *interp, const char *zPre, const char *z, int n){
  if( interp ){
    char *zRes = 0;
    int nRes = 0;

    Th_SetVar(interp, (char *)"::th_stack_trace", -1, 0, 0);

    Th_StringAppend(interp, &zRes, &nRes, zPre, -1);
    if( zRes[nRes-1]=='"' ){
      Th_StringAppend(interp, &zRes, &nRes, z, n);
      Th_StringAppend(interp, &zRes, &nRes, (const char *)"\"", 1);
    }else{
      Th_StringAppend(interp, &zRes, &nRes, (const char *)" ", 1);
      Th_StringAppend(interp, &zRes, &nRes, z, n);

    return zResult;
  }else{
    return (char *)Th_Malloc(pInterp, 1);
  }
}


/*
** Wrappers around the supplied malloc() and free()
*/
void *Th_Malloc(Th_Interp *pInterp, int nByte){
  void *p = pInterp->pVtab->xMalloc(nByte);
  if( p ){
    memset(p, 0, nByte);
  }
  return p;
}
void Th_Free(Th_Interp *pInterp, void *z){
  if( z ){
    pInterp->pVtab->xFree(z);
  }
}

/*
** Install a new th1 command.
**
** If a command of the same name already exists, it is deleted automatically.
*/
int Th_CreateCommand(
  Th_Interp *interp,
  const char *zName,                 /* New command name */
  Th_CommandProc xProc,              /* Command callback proc */
  void *pContext,                    /* Value to pass as second arg to xProc */
  void (*xDel)(Th_Interp *, void *)  /* Command destructor callback */
){
  Th_HashEntry *pEntry;
  Th_Command *pCommand;

  }else{
    pCommand = Th_Malloc(interp, sizeof(Th_Command));
  }
  pCommand->xProc = xProc;
  pCommand->pContext = pContext;
  pCommand->xDel = xDel;
  pEntry->pData = (void *)pCommand;

  return TH_OK;
}

/*
** Rename the existing command (zName, nName) to (zNew, nNew). If nNew is 0,
** the command is deleted instead of renamed.
**
** If successful, TH_OK is returned. If command zName does not exist, or
** if command zNew already exists, an error message is left in the
** interpreter result and TH_ERROR is returned.
*/
int Th_RenameCommand(
  Th_Interp *interp,
  const char *zName,             /* Existing command name */
  int nName,                     /* Number of bytes at zName */
  const char *zNew,              /* New command name */
  int nNew                       /* Number of bytes at zNew */
){
  Th_HashEntry *pEntry;
  Th_HashEntry *pNewEntry;

  pEntry = Th_HashFind(interp, interp->paCmd, zName, nName, 0);
  if( !pEntry ){

** Split a th1 list into its component elements. The list to split is
** passed via arguments (zList, nList). If successful, TH_OK is returned.
** If an error occurs (if (zList, nList) is not a valid list) an error
** message is left in the interpreter result and TH_ERROR returned.
**
** If successful, *pnCount is set to the number of elements in the list.
** panElem is set to point at an array of *pnCount integers - the lengths
** of the element values. *pazElem is set to point at an array of
** pointers to buffers containing the array element's data.
**
** To free the arrays allocated at *pazElem and *panElem, the caller
** should call Th_Free() on *pazElem only. Exactly one such call to
** Th_Free() must be made per call to Th_SplitList().
**
** Example:

**     }
**
**     Th_Free(interp, azElem);
**
*/
int Th_SplitList(
  Th_Interp *interp,
  const char *zList,              /* Pointer to buffer containing list */
  int nList,                      /* Number of bytes at zList */
  char ***pazElem,                /* OUT: Array of pointers to element data */
  int **panElem,                  /* OUT: Array of element data lengths */
  int *pnCount                    /* OUT: Number of elements in list */
){
  int rc;
  interp->isListMode = 1;
  rc = thSplitList(interp, zList, nList, pazElem, panElem, pnCount);
  interp->isListMode = 0;
  if( rc ){
    Th_ErrorMessage(interp, "Expected list, got: \"", zList, nList);
  }
  return rc;
}

/*
** Append a new element to an existing th1 list. The element to append
** to the list is (zElem, nElem).
**
** A pointer to the existing list must be stored at *pzList when this
** function is called. The length must be stored in *pnList. The value
** of *pzList must either be NULL (in which case *pnList must be 0), or
** a pointer to memory obtained from Th_Malloc().
**
** This function calls Th_Free() to free the buffer at *pzList and sets
** *pzList to point to a new buffer containing the new list value. *pnList
** is similarly updated before returning. The return value is always TH_OK.
**
** Example:
**
**     char *zList = 0;
**     int nList = 0;
**     for (...) {
**       char *zElem = <some expression>;
**       Th_ListAppend(interp, &zList, &nList, zElem, -1);
**     }
**     Th_SetResult(interp, zList, nList);
**     Th_Free(interp, zList);
**
*/
int Th_ListAppend(
  Th_Interp *interp,           /* Interpreter context */
  char **pzList,               /* IN/OUT: Ptr to ptr to list */
  int *pnList,                 /* IN/OUT: Current length of *pzList */
  const char *zElem,           /* Data to append */
  int nElem                    /* Length of nElem */
){
  Buffer output;
  int i;

  int hasSpecialChar = 0;
  int hasEscapeChar = 0;

/*
** Append a new element to an existing th1 string. This function uses
** the same interface as the Th_ListAppend() function.
*/
int Th_StringAppend(
  Th_Interp *interp,           /* Interpreter context */
  char **pzStr,                /* IN/OUT: Ptr to ptr to list */
  int *pnStr,                  /* IN/OUT: Current length of *pzStr */
  const char *zElem,           /* Data to append */
  int nElem                    /* Length of nElem */
){
  char *zNew;
  int nNew;

  if( nElem<0 ){
    nElem = th_strlen(zElem);

  Th_Free(interp, *pzStr);
  *pzStr = zNew;
  *pnStr = nNew;

  return TH_OK;
}

/*
** Delete an interpreter.
*/
void Th_DeleteInterp(Th_Interp *interp){
  assert(interp->pFrame);
  assert(0==interp->pFrame->pCaller);

  /* Delete the contents of the global frame. */
  thPopFrame(interp);

  /* Delete any result currently stored in the interpreter. */
  Th_SetResult(interp, 0, 0);

  /* Delete all registered commands and the command hash-table itself. */
  Th_HashIterate(interp, interp->paCmd, thFreeCommand, (void *)interp);
  Th_HashDelete(interp, interp->paCmd);

  /* Delete the interpreter structure itself. */
  Th_Free(interp, (void *)interp);
}

/*
** Create a new interpreter.
*/
Th_Interp * Th_CreateInterp(Th_Vtab *pVtab){
  Th_Interp *p;

  /* Allocate and initialise the interpreter and the global frame */
  p = pVtab->xMalloc(sizeof(Th_Interp) + sizeof(Th_Frame));

typedef struct Expr Expr;
struct Expr {
  Operator *pOp;
  Expr *pParent;
  Expr *pLeft;
  Expr *pRight;

  char *zValue;      /* Pointer to literal value */
  int nValue;        /* Length of literal value buffer */
};

/* Unary operators */
#define OP_UNARY_MINUS  2
#define OP_UNARY_PLUS   3
#define OP_BITWISE_NOT  4

  /* Note: all unary operators have (iPrecedence==1) */
  {"-",  OP_UNARY_MINUS,    1, ARG_NUMBER},
  {"+",  OP_UNARY_PLUS,     1, ARG_NUMBER},
  {"~",  OP_BITWISE_NOT,    1, ARG_INTEGER},
  {"!",  OP_LOGICAL_NOT,    1, ARG_INTEGER},

  /* Binary operators. It is important to the parsing in Th_Expr() that
   * the two-character symbols ("==") appear before the one-character
   * ones ("="). And that the priorities of all binary operators are
   * integers between 2 and 12.
   */
  {"<<", OP_LEFTSHIFT,      4, ARG_INTEGER},
  {">>", OP_RIGHTSHIFT,     4, ARG_INTEGER},
  {"<=", OP_LE,             5, ARG_NUMBER},
  {">=", OP_GE,             5, ARG_NUMBER},

  {"|",  OP_BITWISE_OR,    10, ARG_INTEGER},

  {0,0,0,0}
};

/*
** The first part of the string (zInput,nInput) contains a number.
** Set *pnVarname to the number of bytes in the numeric string.
*/
static int thNextNumber(
  Th_Interp *interp,
  const char *zInput,
  int nInput,
  int *pnLiteral
){
  int i;
  int seenDot = 0;
  for(i=0; i<nInput; i++){
    char c = zInput[i];
    if( (seenDot || c!='.') && !th_isdigit(c) ) break;

    if( rc==TH_OK ){
      eArgType = pExpr->pOp->eArgType;
      if( eArgType==ARG_NUMBER ){
        if( (zLeft==0 || TH_OK==Th_ToInt(0, zLeft, nLeft, &iLeft))
         && (zRight==0 || TH_OK==Th_ToInt(0, zRight, nRight, &iRight))
        ){
          eArgType = ARG_INTEGER;
        }else if(
          (zLeft && TH_OK!=Th_ToDouble(interp, zLeft, nLeft, &fLeft)) ||
          (zRight && TH_OK!=Th_ToDouble(interp, zRight, nRight, &fRight))
        ){
          /* A type error. */
          rc = TH_ERROR;
        }
      }else if( eArgType==ARG_INTEGER ){
        rc = Th_ToInt(interp, zLeft, nLeft, &iLeft);
        if( rc==TH_OK && zRight ){
          rc = Th_ToInt(interp, zRight, nRight, &iRight);
        }
      }
    }

    if( rc==TH_OK && eArgType==ARG_INTEGER ){
      int iRes = 0;
      switch( pExpr->pOp->eOp ) {
        case OP_MULTIPLY:     iRes = iLeft*iRight;  break;
        case OP_DIVIDE:

  assert(nToken>0);
#define ISTERM(x) (apToken[x] && (!apToken[x]->pOp || apToken[x]->pLeft))

  for(jj=0; jj<nToken; jj++){
    if( apToken[jj]->pOp && apToken[jj]->pOp->eOp==OP_OPEN_BRACKET ){
      int nNest = 1;
      int iLeft = jj;

      for(jj++; jj<nToken; jj++){
        Operator *pOp = apToken[jj]->pOp;
        if( pOp && pOp->eOp==OP_OPEN_BRACKET ) nNest++;
        if( pOp && pOp->eOp==OP_CLOSE_BRACKET ) nNest--;
        if( nNest==0 ) break;
      }

}

/*
** Parse a string containing a TH expression to a list of tokens.
*/
static int exprParse(
  Th_Interp *interp,        /* Interpreter to leave error message in */
  const char *zExpr,        /* Pointer to input string */
  int nExpr,                /* Number of bytes at zExpr */
  Expr ***papToken,         /* OUT: Array of tokens. */
  int *pnToken              /* OUT: Size of token array */
){
  int i;

  int rc = TH_OK;

          assert( !pNew->pOp );
          pNew->zValue = Th_Malloc(interp, pNew->nValue);
          memcpy(pNew->zValue, z, pNew->nValue);
          i += pNew->nValue;
        }
        if( (nToken%16)==0 ){
          /* Grow the apToken array. */
          Expr **apTokenOld = apToken;
          apToken = Th_Malloc(interp, sizeof(Expr *)*(nToken+16));
          memcpy(apToken, apTokenOld, sizeof(Expr *)*nToken);
        }

        /* Put the new token at the end of the apToken array */
        apToken[nToken] = pNew;
        nToken++;

}

/*
** Evaluate the string (zExpr, nExpr) as a Th expression. Store
** the result in the interpreter interp and return TH_OK if
** successful. If an error occurs, store an error message in
** the interpreter result and return an error code.
*/
int Th_Expr(Th_Interp *interp, const char *zExpr, int nExpr){
  int rc;                           /* Return Code */
  int i;                            /* Loop counter */

  int nToken = 0;
  Expr **apToken = 0;

  if( nExpr<0 ){
    nExpr = th_strlen(zExpr);
  }

  /* Parse the expression to a list of tokens. */
  rc = exprParse(interp, zExpr, nExpr, &apToken, &nToken);

  /* If the parsing was successful, create an expression tree from
  ** the parsed list of tokens. If successful, apToken[0] is set
  ** to point to the root of the expression tree.
  */
  if( rc==TH_OK ){
    rc = exprMakeTree(interp, apToken, nToken);
  }

  if( rc!=TH_OK ){
    Th_ErrorMessage(interp, "syntax error in expression: \"", zExpr, nExpr);

/*
** Iterate through all values currently stored in the hash table. Invoke
** the callback function xCallback for each entry. The second argument
** passed to xCallback is a copy of the fourth argument passed to this
** function.
*/
void Th_HashIterate(
  Th_Interp *interp,
  Th_Hash *pHash,
  void (*xCallback)(Th_HashEntry *pEntry, void *pContext),
  void *pContext
){
  int i;
  for(i=0; i<TH_HASHSIZE; i++){
    Th_HashEntry *pEntry;

  if( pHash ){
    Th_HashIterate(interp, pHash, xFreeHashEntry, (void *)interp);
    Th_Free(interp, pHash);
  }
}

/*
** This function is used to insert or delete hash table items, or to
** query a hash table for an existing item.
**
** If parameter op is less than zero, then the hash-table element
** identified by (zKey, nKey) is removed from the hash-table if it
** exists. NULL is returned.
**
** Otherwise, if the hash-table contains an item with key (zKey, nKey),
** a pointer to the associated Th_HashEntry is returned. If parameter
** op is greater than zero, then a new entry is added if one cannot
** be found. If op is zero, then NULL is returned if the item is
** not already present in the hash-table.
*/
Th_HashEntry *Th_HashFind(
  Th_Interp *interp,
  Th_Hash *pHash,
  const char *zKey,
  int nKey,
  int op                      /* -ve = delete, 0 = find, +ve = insert */
){
  unsigned int iKey = 0;
  int i;

**     '\n'   0x0A
**     '\v'   0x0B
**     '\f'   0x0C
**     '\r'   0x0D
**
** Whitespace characters have the 0x01 flag set. Decimal digits have the
** 0x2 flag set. Single byte printable characters have the 0x4 flag set.
** Alphabet characters have the 0x8 bit set.
**
** The special list characters have the 0x10 flag set
**
**    { } [ ] \ ; ' "
**
**    " 0x22
**

  }
  *pResult = sign<0 ? -v1 : v1;
  return z - zBegin;
}

/*
** Try to convert the string passed as arguments (z, n) to an integer.
** If successful, store the result in *piOut and return TH_OK.
**
** If the string cannot be converted to an integer, return TH_ERROR.
** If the interp argument is not NULL, leave an error message in the
** interpreter result too.
*/
int Th_ToInt(Th_Interp *interp, const char *z, int n, int *piOut){
  int i = 0;
  int iOut = 0;

  if( n<0 ){

  *piOut = iOut;
  return TH_OK;
}

/*
** Try to convert the string passed as arguments (z, n) to a double.
** If successful, store the result in *pfOut and return TH_OK.
**
** If the string cannot be converted to a double, return TH_ERROR.
** If the interp argument is not NULL, leave an error message in the
** interpreter result too.
*/
int Th_ToDouble(
  Th_Interp *interp,
  const char *z,
  int n,
  double *pfOut
){
  if( !sqlite3IsNumber((const char *)z, 0) ){
    Th_ErrorMessage(interp, "expected number, got: \"", z, n);
    return TH_ERROR;
  }

/*
** Set the result of the interpreter to the th1 representation of
** the double fVal and return TH_OK.
*/
int Th_SetResultDouble(Th_Interp *interp, double fVal){
  int i;                /* Iterator variable */
  double v = fVal;      /* Input value */
  char zBuf[128];       /* Output buffer */
  char *z = zBuf;       /* Output cursor */
  int iDot = 0;         /* Digit after which to place decimal point */
  int iExp = 0;         /* Exponent (NN in eNN) */
  const char *zExp;     /* String representation of iExp */

  /* Precision: */
  #define INSIGNIFICANT 0.000000000001
  #define ROUNDER       0.0000000000005
  double insignificant = INSIGNIFICANT;

  /* If the real value is negative, write a '-' character to the
   * output and transform v to the corresponding positive number.
   */
  if( v<0.0 ){
    *z++ = '-';
    v *= -1.0;
  }

  /* Normalize v to a value between 1.0 and 10.0. Integer
   * variable iExp is set to the exponent. i.e the original
   * value is (v * 10^iExp) (or the negative thereof).
   */
  if( v>0.0 ){
    while( (v+ROUNDER)>=10.0 ) { iExp++; v *= 0.1; }
    while( (v+ROUNDER)<1.0 )   { iExp--; v *= 10.0; }
  }
  v += ROUNDER;

  /* For a small (<12) positive exponent, move the decimal point

typedef struct Th_Vtab Th_Vtab;

/*
** Opaque handle for interpeter.
*/
typedef struct Th_Interp Th_Interp;

/*
** Create and delete interpreters.
*/
Th_Interp * Th_CreateInterp(Th_Vtab *pVtab);
void Th_DeleteInterp(Th_Interp *);

/*
** Evaluate an TH program in the stack frame identified by parameter
** iFrame, according to the following rules:
**
**   * If iFrame is 0, this means the current frame.
**
**   * If iFrame is negative, then the nth frame up the stack, where n is
**     the absolute value of iFrame. A value of -1 means the calling
**     procedure.
**
**   * If iFrame is +ve, then the nth frame from the bottom of the stack.
**     An iFrame value of 1 means the toplevel (global) frame.
*/
int Th_Eval(Th_Interp *interp, int iFrame, const char *zProg, int nProg);

/*
** Evaluate a TH expression. The result is stored in the
** interpreter result.
*/
int Th_Expr(Th_Interp *interp, const char *, int);

/*
** Access TH variables in the current stack frame. If the variable name
** begins with "::", the lookup is in the top level (global) frame.
*/
int Th_ExistsVar(Th_Interp *, const char *, int);
int Th_GetVar(Th_Interp *, const char *, int);
int Th_SetVar(Th_Interp *, const char *, int, const char *, int);
int Th_LinkVar(Th_Interp *, const char *, int, int, const char *, int);
int Th_UnsetVar(Th_Interp *, const char *, int);

typedef int (*Th_CommandProc)(Th_Interp *, void *, int, const char **, int *);

/*
** Register new commands.
*/
int Th_CreateCommand(
  Th_Interp *interp,
  const char *zName,
  /* int (*xProc)(Th_Interp *, void *, int, const char **, int *), */
  Th_CommandProc xProc,
  void *pContext,
  void (*xDel)(Th_Interp *, void *)
);

/*
** Delete or rename commands.
*/
int Th_RenameCommand(Th_Interp *, const char *, int, const char *, int);

/*
** Push a new stack frame (local variable context) onto the interpreter
** stack, call the function supplied as parameter xCall with the two
** context arguments,
**
**   xCall(interp, pContext1, pContext2)
**
** , then pop the frame off of the interpreter stack. The value returned
** by the xCall() function is returned as the result of this function.
**
** This is intended for use by the implementation of commands such as
** those created by [proc].
*/
int Th_InFrame(Th_Interp *interp,
  int (*xCall)(Th_Interp *, void *pContext1, void *pContext2),
  void *pContext1,
  void *pContext2
);

/*
** Valid return codes for xProc callbacks.
*/
#define TH_OK       0
#define TH_ERROR    1
#define TH_BREAK    2
#define TH_RETURN   3
#define TH_CONTINUE 4

/*
** Set and get the interpreter result.
*/
int Th_SetResult(Th_Interp *, const char *, int);
const char *Th_GetResult(Th_Interp *, int *);
char *Th_TakeResult(Th_Interp *, int *);

/*
** Set an error message as the interpreter result. This also
** sets the global stack-trace variable $::th_stack_trace.
*/
int Th_ErrorMessage(Th_Interp *, const char *, const char *, int);

/*
** Access the memory management functions associated with the specified
** interpreter.
*/
void *Th_Malloc(Th_Interp *, int);
void Th_Free(Th_Interp *, void *);

/*
** Functions for handling TH lists.
*/
int Th_ListAppend(Th_Interp *, char **, int *, const char *, int);
int Th_SplitList(Th_Interp *, const char *, int, char ***, int **, int *);

int Th_StringAppend(Th_Interp *, char **, int *, const char *, int);

/*
** Functions for handling numbers and pointers.
*/
int Th_ToInt(Th_Interp *, const char *, int, int *);
int Th_ToDouble(Th_Interp *, const char *, int, double *);
int Th_SetResultInt(Th_Interp *, int);
int Th_SetResultDouble(Th_Interp *, double);

/*
** This file contains the implementation of all of the TH language
** built-in commands.
**
** All built-in commands are implemented using the public interface
** declared in th.h, so this file serves as both a part of the language
** implementation and an example of how to extend the language with
** new commands.
*/

#include "config.h"
#include "th.h"
#include <string.h>
#include <assert.h>

int Th_WrongNumArgs(Th_Interp *interp, const char *zMsg){
  Th_ErrorMessage(interp, "wrong # args: should be \"", zMsg, -1);
  return TH_ERROR;
}

/*
** Syntax:
**
**   catch script ?varname?
*/
static int catch_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int rc;

  if( argc!=2 && argc!=3 ){
    return Th_WrongNumArgs(interp, "catch script ?varname?");
  }

  rc = Th_Eval(interp, 0, argv[1], -1);
  if( argc==3 ){
    int nResult;
    const char *zResult = Th_GetResult(interp, &nResult);
    Th_SetVar(interp, argv[2], argl[2], zResult, nResult);
  }

  Th_SetResultInt(interp, rc);
  return TH_OK;
}

/*
** TH Syntax:
**
**   if expr1 body1 ?elseif expr2 body2? ? ?else? bodyN?
*/
static int if_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int rc = TH_OK;

  int iCond;           /* Result of evaluating expression */
  int i;

  return rc;

wrong_args:
  return Th_WrongNumArgs(interp, "if ...");
}

/*
** TH Syntax:
**
**   expr expr
*/
static int expr_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  if( argc!=2 ){
    return Th_WrongNumArgs(interp, "expr expression");
  }

  return Th_Expr(interp, argv[1], argl[1]);
}

/*
** Evaluate the th1 script (zBody, nBody) in the local stack frame.
** Return the result of the evaluation, except if the result
** is TH_CONTINUE, return TH_OK instead.
*/
static int eval_loopbody(Th_Interp *interp, const char *zBody, int nBody){
  int rc = Th_Eval(interp, 0, zBody, nBody);
  if( rc==TH_CONTINUE ){
    rc = TH_OK;
  }
  return rc;
}

/*
** TH Syntax:
**
**   for init condition incr script
*/
static int for_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int rc;
  int iCond;

  if( argc!=5 ){
    return Th_WrongNumArgs(interp, "for init condition incr script");
  }

  /* Evaluate the 'init' script */
  rc = Th_Eval(interp, 0, argv[1], -1);

  while( rc==TH_OK
     && TH_OK==(rc = Th_Expr(interp, argv[2], -1))
     && TH_OK==(rc = Th_ToInt(interp, Th_GetResult(interp, 0), -1, &iCond))
     && iCond
     && TH_OK==(rc = eval_loopbody(interp, argv[4], argl[4]))
  ){
    rc = Th_Eval(interp, 0, argv[3], -1);
  }

  if( rc==TH_BREAK ) rc = TH_OK;
  return rc;
}

/*
** TH Syntax:
**
**   list ?arg1 ?arg2? ...?
*/
static int list_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  char *zList = 0;
  int nList = 0;
  int i;

  for(i=1; i<argc; i++){
    Th_ListAppend(interp, &zList, &nList, argv[i], argl[i]);
  }

  Th_SetResult(interp, zList, nList);
  Th_Free(interp, zList);

  return TH_OK;
}

/*
** TH Syntax:
**
**   lindex list index
*/
static int lindex_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int iElem;
  int rc;

  char **azElem;
  int *anElem;

    Th_Free(interp, azElem);
  }

  return rc;
}

/*
** TH Syntax:
**
**   llength list
*/
static int llength_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int nElem;
  int rc;

  if( argc!=2 ){
    return Th_WrongNumArgs(interp, "llength list");
  }

  rc = Th_SplitList(interp, argv[1], argl[1], 0, 0, &nElem);
  if( rc==TH_OK ){
    Th_SetResultInt(interp, nElem);
  }

  return rc;
}

/*
** TH Syntax:
**
**   set varname ?value?
*/
static int set_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  if( argc!=2 && argc!=3 ){
    return Th_WrongNumArgs(interp, "set varname ?value?");
  }

  if( argc==3 ){
    Th_SetVar(interp, argv[1], argl[1], argv[2], argl[2]);
  }
  return Th_GetVar(interp, argv[1], argl[1]);
}

/*
** When a new command is created using the built-in [proc] command, an
** instance of the following structure is allocated and populated. A
** pointer to the structure is passed as the context (second) argument
** to function proc_call1() when the new command is executed.
*/
typedef struct ProcDefn ProcDefn;
struct ProcDefn {
  int nParam;                /* Number of formal (non "args") parameters */
  char **azParam;            /* Parameter names */
  int *anParam;              /* Lengths of parameter names */
  char **azDefault;          /* Default values */
  int *anDefault;            /* Lengths of default values */
  int hasArgs;               /* True if there is an "args" parameter */
  char *zProgram;            /* Body of proc */
  int nProgram;              /* Number of bytes at zProgram */
  char *zUsage;              /* Usage message */
  int nUsage;                /* Number of bytes at zUsage */
};

/* This structure is used to temporarily store arguments passed to an
** invocation of a command created using [proc]. A pointer to an
** instance is passed as the second argument to the proc_call2() function.
*/
typedef struct ProcArgs ProcArgs;
struct ProcArgs {
  int argc;
  const char **argv;
  int *argl;

  int i;
  ProcDefn *p = (ProcDefn *)pContext1;
  ProcArgs *pArgs = (ProcArgs *)pContext2;

  /* Check if there are the right number of arguments. If there are
  ** not, generate a usage message for the command.
  */
  if( (pArgs->argc>(p->nParam+1) && !p->hasArgs)
   || (pArgs->argc<=(p->nParam) && !p->azDefault[pArgs->argc-1])
  ){
    char *zUsage = 0;
    int nUsage = 0;
    Th_StringAppend(interp, &zUsage, &nUsage, pArgs->argv[0], pArgs->argl[0]);
    Th_StringAppend(interp, &zUsage, &nUsage, p->zUsage, p->nUsage);
    Th_StringAppend(interp, &zUsage, &nUsage, (const char *)"", 1);

/*
** This function is the command callback registered for all commands
** created using the [proc] command. The second argument, pContext,
** is a pointer to the associated ProcDefn structure.
*/
static int proc_call1(
  Th_Interp *interp,
  void *pContext,
  int argc,
  const char **argv,
  int *argl
){
  int rc;

  ProcDefn *p = (ProcDefn *)pContext;
  ProcArgs procargs;

  if( rc==TH_RETURN ){
    rc = TH_OK;
  }
  return rc;
}

/*
** This function is registered as the delete callback for all commands
** created using the built-in [proc] command. It is called automatically
** when a command created using [proc] is deleted.
**
** It frees the ProcDefn structure allocated when the command was created.
*/
static void proc_del(Th_Interp *interp, void *pContext){
  ProcDefn *p = (ProcDefn *)pContext;
  Th_Free(interp, (void *)p->zUsage);
  Th_Free(interp, (void *)p);
}

/*
** TH Syntax:
**
**   proc name arglist code
*/
static int proc_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int rc;
  char *zName;

  ProcDefn *p;
  int nByte;
  int i;
  char *zSpace;

  char **azParam;
  int *anParam;
  int nParam;

  char *zUsage = 0;                /* Build up a usage message here */
  int nUsage = 0;                  /* Number of bytes at zUsage */

  if( argc!=4 ){
    return Th_WrongNumArgs(interp, "proc name arglist code");
  }
  if( Th_SplitList(interp, argv[2], argl[2], &azParam, &anParam, &nParam) ){
    return TH_ERROR;
  }

  /* Allocate the new ProcDefn structure. */
  nByte = sizeof(ProcDefn) +                        /* ProcDefn structure */
      (sizeof(char *) + sizeof(int)) * nParam +     /* azParam, anParam */
      (sizeof(char *) + sizeof(int)) * nParam +     /* azDefault, anDefault */
      argl[3] +                                     /* zProgram */
      argl[2];    /* Space for copies of parameter names and default values */
  p = (ProcDefn *)Th_Malloc(interp, nByte);

  /* If the last parameter in the parameter list is "args", then set the
  ** ProcDefn.hasArgs flag. The "args" parameter does not require an
  ** entry in the ProcDefn.azParam[] or ProcDefn.azDefault[] arrays.
  */
  if( anParam[nParam-1]==4 && 0==memcmp(azParam[nParam-1], "args", 4) ){
    p->hasArgs = 1;
    nParam--;
  }

  p->nParam    = nParam;
  p->azParam   = (char **)&p[1];
  p->anParam   = (int *)&p->azParam[nParam];
  p->azDefault = (char **)&p->anParam[nParam];
  p->anDefault = (int *)&p->azDefault[nParam];
  p->zProgram = (char *)&p->anDefault[nParam];
  memcpy(p->zProgram, argv[3], argl[3]);
  p->nProgram = argl[3];
  zSpace = &p->zProgram[p->nProgram];

  for(i=0; i<nParam; i++){
    char **az;
    int *an;
    int n;
    if( Th_SplitList(interp, azParam[i], anParam[i], &az, &an, &n) ){
      goto error_out;
    }

 error_out:
  Th_Free(interp, azParam);
  Th_Free(interp, zUsage);
  return TH_ERROR;
}

/*
** TH Syntax:
**
**   rename oldcmd newcmd
*/
static int rename_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  if( argc!=3 ){
    return Th_WrongNumArgs(interp, "rename oldcmd newcmd");
  }
  return Th_RenameCommand(interp, argv[1], argl[1], argv[2], argl[2]);
}

/*
** TH Syntax:
**
**   break    ?value...?
**   continue ?value...?
**   ok       ?value...?
**   error    ?value...?
*/
static int simple_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  if( argc!=1 && argc!=2 ){
    return Th_WrongNumArgs(interp, "return ?value?");
  }
  if( argc==2 ){
    Th_SetResult(interp, argv[1], argl[1]);
  }
  return FOSSIL_PTR_TO_INT(ctx);
}

/*
** TH Syntax:
**
**   return ?-code code? ?value?
*/
static int return_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int iCode = TH_RETURN;
  if( argc<1 || argc>4 ){
    return Th_WrongNumArgs(interp, "return ?-code code? ?value?");
  }
  if( argc>2 ){

  }
  if( iRes==0 ){
    iRes = nLeft-nRight;
  }

  if( iRes<0 ) iRes = -1;
  if( iRes>0 ) iRes = 1;

  return Th_SetResultInt(interp, iRes);
}

/*
** TH Syntax:
**
**   string first NEEDLE HAYSTACK

  for(i=0; i<(nHaystack-nNeedle); i++){
    if( 0==memcmp(zNeedle, &zHaystack[i], nNeedle) ){
      iRes = i;
      break;
    }
  }

  return Th_SetResultInt(interp, iRes);
}

/*
** TH Syntax:
**
**   string is CLASS STRING

  for(i=nHaystack-nNeedle-1; i>=0; i--){
    if( 0==memcmp(zNeedle, &zHaystack[i], nNeedle) ){
      iRes = i;
      break;
    }
  }

  return Th_SetResultInt(interp, iRes);
}

/*
** TH Syntax:
**
**   string length STRING

/*
** TH Syntax:
**
**   unset VAR
*/
static int unset_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  if( argc!=2 ){
    return Th_WrongNumArgs(interp, "unset var");
  }
  return Th_UnsetVar(interp, argv[1], argl[1]);
}

int Th_CallSubCommand(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl,
  Th_SubCommand *aSub
){
  if( argc>1 ){

**   string is      CLASS STRING
**   string last    NEEDLE HAYSTACK ?STARTINDEX?
**   string length  STRING
**   string range   STRING FIRST LAST
**   string repeat  STRING COUNT
*/
static int string_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  Th_SubCommand aSub[] = {
    { "compare", string_compare_command },

/*
** TH Syntax:
**
**   info exists VARNAME
*/
static int info_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  Th_SubCommand aSub[] = {
    { "exists",  info_exists_command },
    { 0, 0 }
  };
  return Th_CallSubCommand(interp, ctx, argc, argv, argl, aSub);
}

/*
** Convert the script level frame specification (used by the commands
** [uplevel] and [upvar]) in (zFrame, nFrame) to an integer frame as
** used by Th_LinkVar() and Th_Eval(). If successful, write the integer
** frame level to *piFrame and return TH_OK. Otherwise, return TH_ERROR
** and leave an error message in the interpreter result.
*/
static int thToFrame(
  Th_Interp *interp,
  const char *zFrame,
  int nFrame,
  int *piFrame
){
  int iFrame;
  if( th_isdigit(zFrame[0]) ){
    int rc = Th_ToInt(interp, zFrame, nFrame, &iFrame);
    if( rc!=TH_OK ) return rc;
    iFrame = iFrame * -1;

/*
** TH Syntax:
**
**   uplevel ?LEVEL? SCRIPT
*/
static int uplevel_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int iFrame = -1;

  if( argc!=2 && argc!=3 ){
    return Th_WrongNumArgs(interp, "uplevel ?level? script...");
  }
  if( argc==3 && TH_OK!=thToFrame(interp, argv[1], argl[1], &iFrame) ){
    return TH_ERROR;
  }
  return Th_Eval(interp, iFrame, argv[argc-1], -1);
}

/*
** TH Syntax:
**
**   upvar ?FRAME? OTHERVAR MYVAR ?OTHERVAR MYVAR ...?
*/
static int upvar_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int iVar = 1;
  int iFrame = -1;
  int rc = TH_OK;
  int i;

  if( TH_OK==thToFrame(0, argv[1], argl[1], &iFrame) ){
    iVar++;
  }
  if( argc==iVar || (argc-iVar)%2 ){
    return Th_WrongNumArgs(interp,
        "upvar frame othervar myvar ?othervar myvar...?");
  }
  for(i=iVar; rc==TH_OK && i<argc; i=i+2){
    rc = Th_LinkVar(interp, argv[i+1], argl[i+1], iFrame, argv[i], argl[i]);
  }
  return rc;
}

/*
** TH Syntax:
**
**   breakpoint ARGS
**
** This command does nothing at all. Its purpose in life is to serve
** as a point for setting breakpoints in a debugger.
*/
static int breakpoint_command(
  Th_Interp *interp,
  void *ctx,
  int argc,
  const char **argv,
  int *argl
){
  int cnt = 0;
  cnt++;
  return TH_OK;
}

    {"expr",     expr_command,    0},
    {"for",      for_command,     0},
    {"if",       if_command,      0},
    {"info",     info_command,    0},
    {"lindex",   lindex_command,  0},
    {"list",     list_command,    0},
    {"llength",  llength_command, 0},
    {"proc",     proc_command,    0},
    {"rename",   rename_command,  0},
    {"set",      set_command,     0},
    {"string",   string_command,  0},
    {"unset",    unset_command,   0},
    {"uplevel",  uplevel_command, 0},
    {"upvar",    upvar_command,   0},

    {"breakpoint", breakpoint_command, 0},

    {"return",   return_command, 0},
    {"break",    simple_command, (void *)TH_BREAK},
    {"continue", simple_command, (void *)TH_CONTINUE},
    {"error",    simple_command, (void *)TH_ERROR},

    {0, 0, 0}
  };
  int i;

  /* Add the language commands. */
  for(i=0; i<(sizeof(aCommand)/sizeof(aCommand[0])); i++){

fossil test-th-eval "set var 1; unset var"
test th1-unset-1 {$RESULT eq {var}}

###############################################################################

fossil test-th-eval "unset var"
test th1-unset-2 {$RESULT eq {TH_ERROR: no such variable: var}}

###############################################################################

fossil test-th-eval "set var 1; unset var; unset var"
test th1-unset-3 {$RESULT eq {TH_ERROR: no such variable: var}}