Catch.java

package org.basex.query.expr;

import static org.basex.query.QueryText.*;
import static org.basex.util.Token.*;

import org.basex.query.QueryContext;
import org.basex.query.QueryException;
import org.basex.query.item.Empty;
import org.basex.query.item.Int;
import org.basex.query.item.QNm;
import org.basex.query.item.SeqType;
import org.basex.query.item.Str;
import org.basex.query.item.Value;
import org.basex.query.util.Err;
import org.basex.query.util.Var;
import org.basex.util.InputInfo;

/**
 * Catch clause.
 *
 * @author BaseX Team 2005-12, BSD License
 * @author Christian Gruen
 */
public final class Catch extends Single {
  /** Error QNames. */
  private static final QNm[] QNM = {
    create(ECODE), create(EDESC), create(EVALUE), create(EMODULE),
    create(ELINENUM), create(ECOLNUM), create(EADD)
  };
  /** Error types. */
  private static final SeqType[] TYPES = {
    SeqType.QNM, SeqType.STR_ZO, SeqType.ITEM_ZM, SeqType.STR_ZO,
    SeqType.ITR_ZO, SeqType.ITR_ZO, SeqType.ITEM_ZM
  };

  /** Error variables. */
  private final Var[] vars = new Var[QNM.length];
  /** Supported codes. */
  private final QNm[] codes;

  /**
   * Constructor.
   * @param ii input info
   * @param c supported error codes
   * @param ctx query context
   */
  public Catch(final InputInfo ii, final QNm[] c, final QueryContext ctx) {
    super(ii, null);
    codes = c;
    for(int i = 0; i < QNM.length; i++) vars[i] =
      Var.create(ctx, null, QNM[i], TYPES[i]);
  }

  @Override
  public Catch comp(final QueryContext ctx) throws QueryException {
    final int s = prepare(ctx);
    super.comp(ctx);
    ctx.vars.size(s);
    return this;
  }

  /**
   * Returns the value of the caught expression.
   * @param ctx query context
   * @param ex thrown exception
   * @return resulting item
   * @throws QueryException query exception
   */
  Value value(final QueryContext ctx, final QueryException ex)
      throws QueryException {

    if(!find(ex.err(), ex.qname())) return null;

    final int s = prepare(ctx);
    try {
      int i = 0;
      final byte[] io = ex.file() == null ? EMPTY : token(ex.file().path());
      final Value val = ex.value();
      for(final Value v : new Value[] { ex.qname(),
          Str.get(ex.getLocalizedMessage()), val == null ? Empty.SEQ : val,
          Str.get(io), Int.get(ex.col()), Int.get(ex.line()), Empty.SEQ }) {
        vars[i++].bind(v, ctx);
      }
      return ctx.value(expr);
    } finally {
      ctx.vars.size(s);
    }
  }

  /**
   * Prepares the catch construction.
   * @param ctx query context
   * @return number of variables
   */
  public int prepare(final QueryContext ctx) {
    final int s = ctx.vars.size();
    for(final Var v : vars) ctx.vars.add(v);
    return s;
  }

  /**
   * Checks if one defined error matches the thrown error.
   * @param err error reference
   * @param code error code
   * @return result of check
   */
  private boolean find(final Err err, final QNm code) {
    for(final QNm c : codes) {
      if(c != null) {
        final byte[] cu = c.uri();
        if(err == null || cu.length != 0 &&
            !eq(err.qname().uri(), cu)) continue;
        final byte[] nm = c.local();
        if(nm.length != 0 && !eq(code.local(), nm)) continue;
      }
      return true;
    }
    return false;
  }

  @Override
  public boolean uses(final Use u) {
    return u == Use.VAR || super.uses(u);
  }

  @Override
  public String toString() {
    return "catch * { " + expr + " }";
  }

  /**
   * Creates an error QName with the specified name.
   * @param n name
   * @return QName
   */
  private static QNm create(final byte[] n) {
    return new QNm(concat(ERR, COLON, n), ERRORURI);
  }
}