package com.googlecode.prolog_cafe.builtin;
import com.googlecode.prolog_cafe.exceptions.IllegalTypeException;
import com.googlecode.prolog_cafe.exceptions.PInstantiationException;
import com.googlecode.prolog_cafe.lang.JavaObjectTerm;
import com.googlecode.prolog_cafe.lang.ListTerm;
import com.googlecode.prolog_cafe.lang.Operation;
import com.googlecode.prolog_cafe.lang.Predicate;
import com.googlecode.prolog_cafe.lang.Prolog;
import com.googlecode.prolog_cafe.lang.SymbolTerm;
import com.googlecode.prolog_cafe.lang.Term;
import com.googlecode.prolog_cafe.lang.VariableTerm;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * <code>regex_match/3</code><br>
 *
 * <pre>
 *   'regex_match'(+Pattern object, +Chars, -Matches)
 * </pre>
 */
public class PRED_regex_match_3 extends Predicate.P3 {

  private static final Operation regex_check = new PRED_regex_check();
  private static final Operation regex_next = new PRED_regex_next();
  private static final Operation regex_empty = new PRED_regex_empty();

  public PRED_regex_match_3(Term a1, Term a2, Term a3, Operation cont) {
        arg1 = a1;
        arg2 = a2;
        arg3 = a3;
        this.cont = cont;
  }

  @Override
  public Operation exec(Prolog engine) {
      engine.setB0();
      engine.cont = cont;
      Term a1 = arg1.dereference();
      Term a2 = arg2.dereference();

      if (a1 instanceof VariableTerm) {
        throw new PInstantiationException(this, 1);
      }
      Pattern pattern = (Pattern)((JavaObjectTerm)a1).object();

      if (a2 instanceof VariableTerm) {
        throw new PInstantiationException(this, 1);
      }
      if (!(a2 instanceof SymbolTerm)) {
        throw new IllegalTypeException(this, 1, "atom", a2);
      }
      Matcher matcher = pattern.matcher(a2.name());

      if (!matcher.find()) {
        return engine.fail();
      }

      engine.r1 = new JavaObjectTerm(matcher);
      engine.r2 = arg3;
      return engine.jtry2(regex_check, regex_next);
  }

  private static final class PRED_regex_check extends Operation {
    @Override
    public Operation exec(Prolog engine) {
      Term a1 = engine.r1;
      Term result = engine.r2;
      Matcher matcher = (Matcher)((JavaObjectTerm)a1).object();

      Term matches = getMatches(matcher);

      if (matches == Prolog.Nil || !result.unify(matches, engine.trail)) {
        return engine.fail();
      }
      return engine.cont;
    }
  }

  private static final class PRED_regex_next extends Operation {
    @Override
    public Operation exec(Prolog engine) {
      return engine.trust(regex_empty);
    }
  }

  private static final class PRED_regex_empty extends Operation {
    @Override
    public Operation exec(Prolog engine) {
      Term a1 = engine.r1;
      Matcher matcher = (Matcher)((JavaObjectTerm)a1).object();
      if (!matcher.find()) {
        return engine.fail();
      }

      return engine.jtry2(regex_check, regex_next);
    }
  }

  private static Term getMatches(Matcher matcher) {
    Term list = Prolog.Nil;
    for (int i = matcher.groupCount(); i >= 0; i--) {
      SymbolTerm match = SymbolTerm.create(matcher.group(i));
      list = new ListTerm(match, list);
    }
    return list;
  }
}