/**************************************************************************
 *
 * QueryLex.cpp -- Lexical analyser for a simple query language
 * Copyright (C) 2000  Rodger McNab
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id: QueryLex.cpp 855 2000-01-14 02:17:52Z sjboddie $
 *
 **************************************************************************/

#include "QueryLex.h"
#include "unitool.h"
#include "words.h"

inline void AddNChar (UCArray::const_iterator &here,
		      UCArray &text,
		      int len) {
  while (len > 0) {
    text.push_back (*here++);
    len--;
  }
}

static bool ParseInteger (UCArray::const_iterator &here,
			  UCArray::const_iterator end,
			  LexEl &el) {
  el.Clear();

  // this version of end is used in unitool
  UCArray::const_iterator endMinus1 = end-1;

  int charLen;
  unsigned short c; // one character lookahead
  charLen = parse_utf8_char (here, endMinus1, &c);

  // check for positive or negative
  bool neg = false;
  if (c == '+') {
    AddNChar (here, el.text, charLen);
    charLen = parse_utf8_char (here, endMinus1, &c);
  } else if (c == '-') {
    neg = true;
    AddNChar (here, el.text, charLen);
    charLen = parse_utf8_char (here, endMinus1, &c);
  }

  // read in number part
  el.num = 0;
  el.lexType = IntegerE;
  while (c >= '0' && c <= '9') {
    el.num = el.num*10 + c - '0';
    AddNChar (here, el.text, charLen);
    charLen = parse_utf8_char (here, endMinus1, &c);
  }

  if (neg) el.num *= -1;

  return (!el.text.empty());
}

static bool ParseTerm (UCArray::const_iterator &here,
		       UCArray::const_iterator end,
		       UCArray &text) {
  UCArray::const_iterator endMinus1 = end-1;
  here = ParseIndexWord (here, endMinus1, text);
  return !text.empty();
}


bool ParseLexEl (UCArray::const_iterator &here,
		 UCArray::const_iterator end,
		 LexEl &el) {
  el.Clear();

  // strange things can happen if here == end == 0
  if (here == end) return false;
  
  // this version of end is used in unitool
  UCArray::const_iterator endMinus1 = end-1;
  
  // ignore all white space
  int charLen;
  unsigned short c; // one character lookahead
  charLen = parse_utf8_char (here, endMinus1, &c);
  while (here != end && is_unicode_space (c)) {
    here += charLen;
    charLen = parse_utf8_char (here, endMinus1, &c);
  }
  if (here == end) return false;

  if (c == '(') {
    el.lexType = OpenBracketE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == ')') {
    el.lexType = CloseBracketE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == '\"') {
    el.lexType = QuoteE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == '#') {
    el.lexType = TermWeightE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == '$') {
    el.lexType = StemMethodE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == '^') {
    el.lexType = RangeE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == '@') {
    el.lexType = AtE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == ':') {
    el.lexType = TagE;
    AddNChar (here, el.text, charLen);
    return true;
    
  } else if (c == '+' || c == '-' ||
	     (c >= '0' && c <= '9')) {
    return ParseInteger (here, end, el);
  }

  // assume it is a term of some sort
  if (!ParseTerm (here, end, el.text)) return false;

  UCArray AND; SetCStr (AND, "AND");
  if (el.text == AND) {
    el.lexType = AndOpE;
    return true;
  }
  UCArray OR; SetCStr (OR, "OR");
  if (el.text == OR) {
    el.lexType = OrOpE;
    return true;
  }
  UCArray NOT; SetCStr (NOT, "NOT");
  if (el.text == NOT) {
    el.lexType = NotOpE;
    return true;
  }

  el.lexType = TermE;
  return true;
}