src/main/resources/lang-extension/lang.txt

import org.apache.asterix.bad.lang.statement.BrokerDropStatement;
import org.apache.asterix.bad.lang.statement.ChannelDropStatement;
import org.apache.asterix.bad.lang.statement.ChannelSubscribeStatement;
import org.apache.asterix.bad.lang.statement.ChannelUnsubscribeStatement;
import org.apache.asterix.bad.lang.statement.CreateBrokerStatement;
import org.apache.asterix.bad.lang.statement.CreateChannelStatement;


@merge
Statement SingleStatement() throws ParseException:
{
  // merge area 1
  before:
  after:
}
{
  (
    // merge area 2
    before:
    after:    | stmt = ChannelSubscriptionStatement())
  {
    // merge area 3
  }
}

@merge
Statement CreateStatement() throws ParseException:
{
  // merge area 1
  before:
  after:
}
{
  (
    // merge area 2
    before:
    after:    | stmt = ChannelSpecification() | stmt = BrokerSpecification())
  {
    // merge area 3
  }
}

@merge
Statement DropStatement() throws ParseException:
{
  // merge area 1
  before:
  after:
}
{
  (
    // merge area 2
    before:
    after:    | "channel" pairId = QualifiedName() ifExists = IfExists()
      {
        stmt = new ChannelDropStatement(pairId.first, pairId.second, ifExists);
      }
      	      | <BROKER> pairId = QualifiedName() ifExists = IfExists()	
      {	
        stmt = new BrokerDropStatement(pairId.first, pairId.second, ifExists);	
      }
      )
  {
    // merge area 3
  }
}

@new
CreateChannelStatement ChannelSpecification() throws ParseException:
{
  Pair<Identifier,Identifier> nameComponents = null;
  FunctionSignature appliedFunction = null;
  CreateChannelStatement ccs = null;
  String fqFunctionName = null;
  Expression period = null;
}
{
  (
    "repetitive" "channel"  nameComponents = QualifiedName()
    <USING> appliedFunction = FunctionSignature()
    "period" period = FunctionCallExpr()
    {
      ccs = new CreateChannelStatement(nameComponents.first,
                                   nameComponents.second, appliedFunction, period);
    }
  )
    {
      return ccs;
    }
}

@new
CreateBrokerStatement BrokerSpecification() throws ParseException:
{
  CreateBrokerStatement cbs = null;
  Pair<Identifier,Identifier> name = null;
  String endPoint = null;
}
{
  (
    <BROKER>  name = QualifiedName()
    <AT>  endPoint = StringLiteral()
    {
      cbs = new CreateBrokerStatement(name.first, name.second,endPoint);
    }
  )
    {
      return cbs;
    }
}

@new
Statement ChannelSubscriptionStatement() throws ParseException:
{
  Statement stmt = null;
  Pair<Identifier,Identifier> nameComponents = null;
  List<Expression> argList = new ArrayList<Expression>();
  Expression tmp = null;
  String id = null;
  String subscriptionId = null;
  Pair<Identifier,Identifier> brokerName = null;
}
{
  (
  "subscribe" <TO> nameComponents = QualifiedName()
   <LEFTPAREN> (tmp = Expression()
   {
      argList.add(tmp);
   }
   (<COMMA> tmp = Expression()
   {
      argList.add(tmp);
   }
   )*)? <RIGHTPAREN> <ON> brokerName = QualifiedName()
   {
      stmt = new ChannelSubscribeStatement(nameComponents.first, nameComponents.second, argList, getVarCounter(), brokerName.first, brokerName.second, subscriptionId);
   }
   | "unsubscribe" id = StringLiteral() <FROM> nameComponents = QualifiedName()
      {
        setDataverses(new ArrayList<String>());
        setDatasets(new ArrayList<String>());
        VariableExpr varExp = new VariableExpr();
        VarIdentifier var = new VarIdentifier();
        varExp.setVar(var);
        var.setValue("$subscriptionPlaceholder");
        getCurrentScope().addNewVarSymbolToScope(varExp.getVar());
        List<String> dataverses = getDataverses();
        List<String> datasets = getDatasets();
        // we remove the pointer to the dataverses and datasets
        setDataverses(null);
        setDatasets(null);
        stmt = new ChannelUnsubscribeStatement(varExp, nameComponents.first, nameComponents.second, id, getVarCounter(), dataverses, datasets);
      }
     | "change" "subscription" subscriptionId = StringLiteral()  <ON> nameComponents = QualifiedName()
       <LEFTPAREN> (tmp = Expression()
       {
         argList.add(tmp);
       }
       (<COMMA> tmp = Expression()
       {
         argList.add(tmp);
       }
       )*)? <RIGHTPAREN>
        <TO> brokerName = QualifiedName()
      {
        stmt = new ChannelSubscribeStatement(nameComponents.first, nameComponents.second, argList, getVarCounter(), brokerName.first, brokerName.second, subscriptionId);
      }
    )
    {
      return stmt;
    }
}

<DEFAULT,IN_DBL_BRACE>
TOKEN [IGNORE_CASE]:
{
    <BROKER : "broker">
}