// $Id: Parser.cs 1295 2007-05-11 16:52:51Z josd $

namespace Eulersharp {

using System;
using System.Collections;
using System.Globalization;
using System.Text;
using System.Xml;

/// <summary>N3 parser</summary>
/// <author>Jos De Roo</author>

public class Parser {
  internal String str;                      // N3 string
  internal int pos = 0;                     // tokenizer position
  internal int line = 1;                    // line counter
  internal ArrayList vt = null;             // quantified variables table
  internal Euler r = null;                  // root Euler object
  internal String u = null;                 // base URI of the RDF resource
  
  internal const String ST = "{}[]()<>\"';,.^! \t\r\n\\";
  internal const String LOGa = "a";
  internal const String LOGe = "=";
  internal const String LOGi = "=>";
  internal const String DPO = "<http://www.daml.org/2001/03/daml+oil";
  internal const String ONT = "<http://www.w3.org/2001/10/daml+oil";
  internal const String OWLequivalentTo = "<http://www.w3.org/2002/07/owl#equivalentTo>";
  internal const String OWLsameIndividualAs = "<http://www.w3.org/2002/07/owl#sameIndividualAs>";
  internal const String OWLsameClassAs = "<http://www.w3.org/2002/07/owl#sameClassAs>";
  internal const String OWLsamePropertyAs = "<http://www.w3.org/2002/07/owl#samePropertyAs>";
  internal const String OWLdifferentIndividualFrom = "<http://www.w3.org/2002/07/owl#differentIndividualFrom>";
  internal const String OWLUnambiguousProperty = "<http://www.w3.org/2002/07/owl#UnambiguousProperty>";
  internal const String OWLUniqueProperty = "<http://www.w3.org/2002/07/owl#UniqueProperty>";
  
  /// <summary>constructs an N3 parser</summary>

  public Parser() {
  }
  
  /// <summary>constructs an N3 parser</summary>
  /// <param name="s">the N3 string</param>
  /// <param name="vartab">quantified variables table</param>
  /// <param name="root">Euler object</param>
  /// <param name="uri">URI of the RDF resource</param>

  public Parser(String s, ArrayList vartab, Euler root, String uri) {
    str = s;
    vt = vartab;
    r = root;
    u = uri;
  }
  
  /// <summary>N3 triple parse method</summary>
  /// <returns>Euler object</returns>

  public virtual Euler Parse() {
    String nt = tokenize();
    if (nt == null) return null;
    return parse(true, nt);
  }
  
  /// <summary>N3 node parse method</summary>
  /// <param name="nt">next token</param>
  /// <returns>Euler object</returns>

  public virtual Euler Parse(String nt) {
    return parse(false, nt);
  }
  
  internal Euler parse(bool b, String nt) {
    Euler e = new Euler();
    try {
      if (u != null && u.StartsWith("_:")) e.src = Euler.Ekb;
      else e.src = "<" + u + ">";
      e.line = line;
      if (b) {
        if (nt == null) e.subj = null;
        else if (nt.Equals("{")) {
          nt = tokenize();
          if (nt.Equals(".")) e.subj = parse(false, "{}");
          else e.subj = parse(true, nt);
          Euler el = e.subj;
          while (el.near != null) el = el.near;
          nt = tokenize();
          while (!nt.Equals("}")) {
            el.near = parse(true, nt);
            while (el.near != null) el = el.near;
            nt = tokenize();
          }
        }
        else if (nt.Equals("[")) {
          e.subj = parse(true, null);
          if (e.subj.verb == null) r.verb = ";]";
          nt = tokenize();
          if (!nt.Equals("]")) Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (p1) expecting ] at " + e + " but got " + nt);
          int cpos = pos;
          nt = tokenize();
          if (nt.Equals(".")) {
            e.obj = parse(false, "");
            e.verb = "";
            e.cverb = "";
            e.bound = true;
            return e;
          }
          else pos = cpos;
        }
        else if (nt.Equals("(")) {
          list(e);
          e.subj = e.obj;
          e.obj = null;
          int cpos = pos;
          nt = tokenize();
          if (nt.Equals(".")) {
            e.obj = parse(false, "");
            e.verb = "";
            e.cverb = "";
            e.bound = true;
            return e;
          }
          else pos = cpos;
        }
        else {
          e.subj = parse(false, nt);
          if (nt.Equals("this")) e.subj.verb = '<' + u + "#frag" + e.uid + '>';
        }
        path(e.subj);
        if (nt != null && nt.Equals("@forAll")) {
          e.subj = parse(false, "this");
          nt = "log:forAll";
        }  
        else if (nt != null && nt.Equals("@forSome")) {
          e.subj = parse(false, "this");
          nt = "log:forSome";
        }  
        else nt = tokenize();
      }
      if (nt == null || nt.Equals(";")) {
        e.bound = true;
        return e;
      }
      else if (e.subj != null && nt.StartsWith("_:")) {
        e.cverb = nt;
        if (!vt.Contains(nt)) vt.Add(nt);
      }
      else if (nt.Equals("[")) {
        String a = "_:e" + e.uid;
        if (!vt.Contains(a)) vt.Add(a);
        Euler ap = parse(true, a);
        e.cverb = a;
        if (ap.verb != null) r.verb = ";]";
        nt = tokenize();
        if (!nt.Equals("]")) Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (p2) expecting ] at " + e + " but got " + nt);
        if (ap.verb.Equals(Euler.OWLsameAs)) {
          e.cverb = ap.obj.cverb;
          e.vv = true;
        }
        else e.near = ap;
      }
      else if (nt.Equals("(")) {
        list(e);
        return e.obj;
      }
      else e.cverb = nt;
      if (e.cverb.EndsWith("_@")) {
        e.vv = true;
        e.cverb = e.cverb.Substring(0, e.cverb.Length - 2);
      }
      e.verb = e.cverb;
      if (e.verb.EndsWith("@@")) e.verb = e.verb.Substring(0, e.verb.Length - 2);
      if (r != null && e.verb.Length > 0 && e.verb[0] == '<') {
        String nsq = toURI(e.verb.Substring(1, e.verb.Length - 2));
        int nsh = nsq.LastIndexOf('#');
        int nss = nsq.LastIndexOf('/');
        String nsu = '<' + (nsh != -1 ? nsq.Substring(0, nsh + 1) : nsq.Substring(0, nss + 1)) + '>';
        String nsn = nsh != -1 ? nsq.Substring(nsh + 1) : nsq.Substring(nss + 1);
        String nsp = null;
        for (IEnumerator enr = r.ext.ns.Keys.GetEnumerator(); enr.MoveNext(); ) { 	 
          String nsx = (String)enr.Current; 	 
          String nsy = (String)r.ext.ns[nsx]; 	 
          if (nsu.Equals(nsy)) nsp = nsx; 	 
        } 	 
        if (nsp == null) { 	 
	  int i = 0;
	  while (true) {
	    nsp = "nsp" + i + ':';
	    if (r.ext.ns[nsp] == null) break;
	    i++;
	  }
          r.ext.ns[nsp] = nsu;
        }
        e.verb = e.cverb = nsp + nsn;
      }
      String s1 = e.verb;
      String s2 = "";
      if (e.verb.IndexOf('"') != -1) {
        s1 = e.verb.Substring(0, e.verb.IndexOf('"'));
        s2 = e.verb.Substring(e.verb.IndexOf('"'));
      }
      if (r != null && s1.Length > 0 && s1.IndexOf(':') == -1 &&
          s1[0] != '(' && s1[0] != '<' && s1[0] != '[' &&
          s1[0] != '_' && s1[0] != '"' && s1[0] != '?' &&
          !r.isNumeral(s1) && r.ext.kw[s1] == null) s1 = ":" + s1;
      if (r != null && s1.Length > 0 && !s1.Equals(LOGa) && !s1.Equals(LOGe) &&
          s1[0] != '(' && s1[0] != '<' && s1[0] != '[' &&
          s1[0] != '_' && s1[0] != '"' && s1.IndexOf(':') != - 1) {
        String pf = s1.Substring(0, s1.IndexOf(':') + 1);
        String pg = (String) r.ext.nsp[pf];
        if (pg != null) pf = pg;
        String qf = (String) r.ext.ns[pf];
        if (qf == null) {
          Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": no @prefix " + pf + " found for " + s1 + ", taking <" + u + "#>");
          qf = "<" + u + "#>";
          r.ext.ns[pf] = qf;
        }
        StringBuilder sb = new StringBuilder(pf);
        sb.Append(e.cverb.Substring(e.cverb.IndexOf(':') + 1));
        e.cverb = sb.ToString();
        sb = new StringBuilder(qf);
        sb.Insert(sb.Length - 1, s1.Substring(s1.IndexOf(':') + 1));
        e.verb = sb.ToString() + s2;
      }
      else if (u != null && s1.Length > 0 && s1[0] == '<' && s1.IndexOf(':') == - 1)
        e.verb = e.cverb = '<' + toURI(s1.Substring(1, s1.Length - 2)) + '>' + s2;
      if (e.verb.Length > 0 && e.verb[0] == '?' && e.verb.IndexOf('@') != -1 ||
	  e.verb.IndexOf("\"@") != -1 && str[pos] != '^' && str[pos + 1] != '^') {
        r.ext.kw[e.verb.Substring(e.verb.LastIndexOf('@') + 1)] = r;
        e.subj = parse(false, e.verb.Substring(0, e.verb.LastIndexOf('@')));
        e.obj = parse(false, e.verb.Substring(e.verb.LastIndexOf('@') + 1));
        e.verb = e.cverb = "@";
      }
      if (e.verb.Equals(LOGa)) e.verb = Euler.RDFtype;
      if (e.verb.Equals(LOGe)) e.verb = Euler.OWLsameAs;
      if (e.verb.Equals(LOGi)) e.verb = Euler.LOGimplies;
      if (e.verb.StartsWith(DPO)) e.verb = Euler.OWL + e.verb.Substring(DPO.Length);
      if (e.verb.StartsWith(ONT)) e.verb = Euler.OWL + e.verb.Substring(ONT.Length);
      if (e.verb.Equals(OWLequivalentTo)) e.verb = Euler.OWLsameAs;
      if (e.verb.Equals(OWLsameIndividualAs)) e.verb = Euler.OWLsameAs;
      if (e.verb.Equals(OWLsameClassAs)) e.verb = Euler.OWLequivalentClass;
      if (e.verb.Equals(OWLsamePropertyAs)) e.verb = Euler.OWLequivalentProperty;
      if (e.verb.Equals(OWLdifferentIndividualFrom)) e.verb = Euler.OWLdifferentFrom;
      if (e.verb.Equals(OWLUnambiguousProperty)) e.verb = Euler.OWLInverseFunctionalProperty;
      if (e.verb.Equals(OWLUniqueProperty)) e.verb = Euler.OWLFunctionalProperty;
      if (e.verb.Equals(Euler.RDFfirst)) e.cverb = "rdf:first";
      if (e.verb.Equals(Euler.RDFrest)) e.cverb = "rdf:rest";
      if (e.verb.Equals(Euler.RDFnil)) e.cverb = "()";
      if (e.verb.StartsWith("?") && vt != null && !vt.Contains(e.verb)) vt.Add(e.verb);
      if (vt != null && vt.Count > 0) e.varid = vt.IndexOf(e.verb);
      if (e.varid == - 1) e.bound = true;
      if (nt.Equals(".") && (str[pos] == ' ' || str[pos] == '\t' || str[pos] == '\r' || str[pos] == '\n')) {
        e.obj = parse(false, "");
        e.verb = "";
        e.cverb = "";
        e.bound = true;
        return e;
      }
      if (!nt.Equals(Euler.RDFfirst) && str != null && pos < str.Length && str[pos] == '^' && str[pos + 1] == '^') {
        pos = pos + 2;
        Euler et = parse(false, tokenize());
        if (!et.verb.Equals(Euler.XSDstring)) {
          e.subj = e.copy();
          e.verb = e.cverb = "^^";
          e.bound = true;
          e.obj = et;
        }
      }
      if (b) {
        nt = tokenize();
        if (nt.Equals("{")) {
          nt = tokenize();
          if (nt.Equals(".")) e.obj = parse(false, "{}");
          else e.obj = parse(true, nt);
          Euler el = e.obj;
          while (el.near != null) el = el.near;
          nt = tokenize();
          while (nt != null && !nt.Equals("}")) {
            el.near = parse(true, nt);
            while (el.near != null) el = el.near;
            nt = tokenize();
          }
        }
        else if (nt.Equals("[")) {
          e.obj = parse(true, null);
          if (e.obj.verb != null) r.verb = ";]";
          nt = tokenize();
          if (!nt.Equals("]")) Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (p3) expecting ] at " + e + " but got " + nt);
        }
        else if (nt.Equals("(")) list(e);
        else e.obj = parse(false, nt);
        path(e.obj);
        nt = tokenize();
        if (nt == null) return e;
        if (nt.EndsWith("\"\"\"")) {
          e.obj.cverb = e.obj.cverb + nt;
          e.obj.verb = e.obj.cverb;
          nt = tokenize();
        }
        Euler el2 = e;
        while (nt.Equals(";") || nt.Equals(",")) {
          while (el2.near != null) el2 = el2.near;
          if (nt.Equals(";")) {
            nt = tokenize();
            if (nt.Equals("]")) {
              r.verb = ";]";
              nt = ";";
              break;
            }
            else if (nt.Equals(".")) break;
          }
          else nt = el2.cverb;
          el2.near = parse(false, nt);
          el2.near.subj = e.subj;
          nt = tokenize();
          if (nt.Equals("{")) {
            nt = tokenize();
            if (nt.Equals(".")) el2.near.obj = parse(false, "{}");
            else el2.near.obj = parse(true, nt);
            Euler ef = el2.near.obj;
            while (ef.near != null) ef = ef.near;
            nt = tokenize();
            while (nt != null && !nt.Equals("}")) {
              ef.near = parse(true, nt);
              while (ef.near != null) ef = ef.near;
              nt = tokenize();
            }
          }
          else if (nt.Equals("[")) {
            el2.near.obj = parse(true, null);
            if (el2.near.obj.verb != null) r.verb = ";]";
            nt = tokenize();
            if (!nt.Equals("]")) Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (p4) expecting ] at " + e + " but got " + nt);
          }
          else if (nt.Equals("(")) list(el2.near);
          else el2.near.obj = parse(false, nt);
          nt = tokenize();
          if (nt == null) return e;
          if (nt.EndsWith("\"\"\"")) {
            el2.near.obj.cverb = el2.near.obj.cverb + nt;
            el2.near.obj.verb = el2.near.obj.cverb;
            nt = tokenize();
          }
          swap(el2.near);
        }
        if (!nt.Equals(".") && !nt.Equals(";"))
          Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (p5) expecting . or ; at " + e + " but got " + nt);
      }
      swap(e);
      if (e.verb.Equals(Euler.LOGimplies) && e.subj != null && e.subj.verb.Equals("{}")) {
        e.obj.vv = true;
        e = e.obj;
      }
      e.far = r;
      return e;
    }
    catch (NullReferenceException exc) {
      Console.Error.WriteLine(exc);
      return e;
    }
  }
  
  internal String tokenize() {
    String nt = token();
    while (pos < str.Length && nt == null) nt = token();
    return nt;
  }
  
  internal String next() {
    int start = pos;
    while (pos < str.Length && ST.IndexOf(str[pos]) < 0) pos++;
    if (pos < str.Length && start == pos && ST.IndexOf(str[pos]) >= 0) pos++;
    if (pos < str.Length && str[pos] == '\n') line++;
    return str.Substring(start, (pos) - (start));
  }
  
  internal String token() {
    if (r.verb != null && r.verb.Equals(".}")) return r.verb = "}";
    if (r.verb != null && r.verb.Equals(";]")) return r.verb = "]";
    if (pos >= str.Length) return null;
    int start = pos;
    String t = null;
    String nt = next();
    if (nt.IndexOf('#') != - 1) {
      t = nt.Substring(0, nt.IndexOf('#'));
      String v = r.verb;
      while (nt != null && !nt.Equals("\n") && pos < str.Length) nt = next();
      r.verb = v;
      if (t.Equals("")) return null;
    }
    else if (nt.Equals("SELECT")) {
      StringBuilder sb = new StringBuilder("(");
      nt = tokenize();
      while (!nt.Equals("\r") && !nt.Equals("\n") && pos < str.Length) {
	sb.Append(nt);
	nt = next();
      }
      t = sb.Append(')').ToString();
    }
    else if (nt.Equals("CONSTRUCT")) {
      t = tokenize();
    }
    else if (nt.Equals("FROM")) {
      // TODO
      nt = tokenize();
      if (nt.Equals("NAMED")) tokenize();
      t = tokenize();
    }
    else if (nt.Equals("UNION")) {
      t = ".";
    }
    else if (nt.Equals("OPTIONAL")) {
      // TODO
      t = tokenize();
    }
    else if (nt.Equals("FILTER")) {
      // TODO
      t = tokenize();
    }
    else if (nt.Equals("@prefix") || nt.Equals("PREFIX")) {
      String nsc = tokenize();
      if (nsc.Equals("default")) nsc = ":";
      String nsd = null;
      String nsu = tokenize();
      if (u != null && nsu.Length > 0 && nsu[0] == '<' && nsu.IndexOf(':') == - 1)
        nsu = '<' + toURI(nsu.Substring(1, nsu.Length - 2)) + '>';
      for (IEnumerator enr = r.ext.ns.Keys.GetEnumerator(); enr.MoveNext(); ) { 	 
	String nsx = (String)enr.Current; 	 
	String nsy = (String)r.ext.ns[nsx]; 	 
	if (nsu.Equals(nsy)) nsd = nsx; 	 
      } 	 
      if (nsd == null) { 	 
	nsd = nsc;
	String nsv = (String)r.ext.ns[nsd];
	int i = 0;
	while (nsv != null && !nsu.Equals(nsv)) {
	  nsd = "p" + i + nsc;
	  nsv = (String)r.ext.ns[nsd];
	  i++;
	}
      }
      r.ext.nsp[nsc] = nsd;
      r.ext.ns[nsd] = nsu;
      if (nt.Equals("@prefix")) tokenize();
      return null;
    }
    else if (nt.Equals("@keywords")) {
      while (nt != null && !nt.Equals(".") && pos < str.Length) {
        nt = next();
        if (!nt.Equals(" ") && !nt.Equals("\t") && !nt.Equals("\r") && !nt.Equals("\n") && !nt.Equals(",") && !nt.Equals(".")) r.ext.kw[nt] = r;
      }
      t = tokenize();
    }
    else if (nt.Equals("\"")) {
      StringBuilder sb = new StringBuilder("\"");
      if (str[pos] == '"' && str[pos + 1] == '"') {
        sb.Append(next()).Append(next());
        while (pos < str.Length && (str[pos] != '"' || str[pos + 1] != '"' || str[pos + 2] != '"')) sb.Append(next());
        sb.Append(next()).Append(next()).Append(next());
      }
      else {
        nt = next();
        while (!nt.Equals("\"")) {
          if (nt.Equals("\\")) {
            sb.Append(nt);
            nt = next();
          }
          sb.Append(nt);
          if (pos >= str.Length) {
            Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (t1) expecting \" at " + sb);
            break;
          }
          nt = next();
        }
        sb.Append("\"");
      }
      if (pos < str.Length && str[pos] == '@') {
        String lang = token();
        int i = lang.IndexOf('-');
        if (i != -1) sb.Append(lang.Substring(0, i) + lang.Substring(i).ToUpper());
        else sb.Append(lang);
      }
      t = sb.ToString();
    }
    else if (nt.Equals("'")) {
      StringBuilder sb = new StringBuilder("'");
      nt = next();
      while (!nt.Equals("'")) {
        sb.Append(nt);
        if (pos >= str.Length) {
          Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (t2) expecting ' at " + sb);
          break;
        }
        nt = next();
      }
      t = sb.Append("'").ToString();
    }
    else if (nt.Equals("<")) {
      StringBuilder sb = new StringBuilder("<");
      nt = next();
      while (!nt.Equals(">")) {
        sb.Append(nt);
        if (pos >= str.Length) {
          Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (t2) expecting > at " + sb);
          break;
        }
        nt = next();
      }
      t = sb.Append(">").ToString();
    }
    else if (nt.Equals("=")) {
      if (str[pos] == '>') t = nt + next();
      else t = nt;
    }
    else if (nt.Equals("is") || nt.Equals("@is")) {
      t = tokenize();
      nt = tokenize();
      if (!(nt.Equals("of") || nt.Equals("@of"))) Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (t4) expecting \"of\" but got " + nt);
      t = t + "@@";
    }
    else if (nt.Equals("has") || nt.Equals("@has")) {
      t = tokenize() + "_@";
      int cpos = pos;
      nt = tokenize();
      if (!(nt.Equals("of") || nt.Equals("@of"))) pos = cpos;
    }
    else if (nt.Equals(" ") || nt.Equals("\t") || nt.Equals("\r") || nt.Equals("\n") ||
             nt.Equals("-") || nt.Equals(">"))
      return null;
    else if (nt.StartsWith("_:") && !nt.EndsWith("_")) t = nt + "_" + Euler.doc + "_";
    else t = nt;
    if (pos < str.Length && ST.IndexOf(t) == -1 && t[0] != '"' && str[pos] == '"') t = t + token();
    while (pos < str.Length - 1 && str[pos] == '.' &&
        str[pos + 1] != ' ' && str[pos + 1] != '\t' && str[pos + 1] != '\r' && str[pos + 1] != '\n' &&
        str[pos + 1] != ']' && str[pos + 1] != '}' && str[pos + 1] != '#') {
      t = t + next() + next();
    }
    if (r.verb != null && t != null && !r.verb.Equals(".") && t.Equals("}")) {
      r.verb = ".}";
      return ".";
    }
    if (r.verb != null && t != null && !r.verb.Equals(";") && t.Equals("]")) {
      r.verb = ";]";
      return ";";
    }
    return r.verb = t;
  }
  
  internal void swap(Euler e) {
    if (e != null && e.subj == null && e.cverb.EndsWith("@@")) {
      e.subj = e.obj;
      e.obj = parse(false, e.cverb.Substring(0, e.cverb.Length - 2));
      e.verb = e.cverb = "!";
    }
    else if (e.subj != null && e.obj != null && e.cverb.EndsWith("@@")) {
      Euler el = e.subj;
      e.subj = e.obj;
      e.obj = el;
      e.cverb = e.cverb.Substring(0, e.cverb.Length - 2);
    }
  }
  
  internal void list(Euler e) {
    Euler el = e;
    while (true) {
      String nt = tokenize();
      if (nt.StartsWith("@")) {
        el.obj = parse(false, '?' + nt.Substring(1));
        nt = tokenize();
        if (!nt.Equals(")")) Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": (p6) expecting ) at " + el + " but got " + nt);
        break;
      }
      else if (nt.Equals(")")) {
        el.obj = parse(false, Euler.RDFnil);
        break;
      }
      else el.obj = parse(false, Euler.RDFfirst);
      if (nt.Equals("{")) {
        nt = tokenize();
        if (nt.Equals(".")) el.obj.obj = parse(false, "{}");
        else el.obj.obj = parse(true, nt);
        Euler er = el.obj.obj;
        while (er.near != null) er = er.near;
        nt = tokenize();
        while (!nt.Equals("}")) {
          er.near = parse(true, nt);
          while (er.near != null) er = er.near;
          nt = tokenize();
        }
      }
      else if (nt.Equals("[")) {
        el.obj.obj = parse(true, null);
        tokenize();
      }
      else el.obj.obj = parse(false, nt);
      path(el.obj.obj);
      el.obj.near = parse(false, Euler.RDFrest);
      el = el.obj.near;
    }
    path(e.obj);
  }

  internal void path(Euler e) {
    if (str != null && pos < str.Length - 1 && str[pos] == '!' &&
        str[pos + 1] != ' ' && str[pos + 1] != '\t' && str[pos + 1] != '\r' && str[pos + 1] != '\n' &&
        str[pos + 1] != ']' && str[pos + 1] != '}' && str[pos + 1] != '#') {
      pos = pos + 1;
      e.subj = e.copy();
      e.verb = e.cverb = "!";
      e.bound = true;
      e.obj = parse(false, tokenize());
      e.near = null;
      path(e);
    }
    if (str != null && pos < str.Length - 1 && str[pos] == '^' &&
        str[pos + 1] != '^' && str[pos + 1] != ' ' && str[pos + 1] != '\t' && str[pos + 1] != '\r' && str[pos + 1] != '\n' &&
        str[pos + 1] != ']' && str[pos + 1] != '}' && str[pos + 1] != '#') {
      pos = pos + 1;
      e.subj = e.copy();
      e.verb = e.cverb = "^";
      e.bound = true;
      e.obj = parse(false, tokenize());
      e.near = null;
      path(e);
    }
  }

  internal String toURI(String s) {
    if (s.Equals("") || s.StartsWith("#")) s = u + s;
    if (!u.Equals("") && s.IndexOf('?') == -1) {
      try {
        if (s.EndsWith("#")) s = new Uri(new Uri(u.Substring(0, u.LastIndexOf('/') + 1)), s.Substring(0, s.Length -1)).ToString() + '#';
        else if (!u.StartsWith("_:")) s = new Uri(new Uri(u.Substring(0, u.LastIndexOf('/') + 1)), s).ToString();
      }
      catch (Exception e) {
        Console.Error.WriteLine("** Parser error ** " + u + " line " + line + ": found " + s + "\n" + e);
      }
    }
    if (s.EndsWith(".n3#")) s = s.Substring(0, s.Length - 4) + "#";
    return s;
  }
}
}