/*
 * Copyright 2013 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.template.soy.exprtree;

import com.google.template.soy.types.SoyType;

/**
 * Interface for the definition of a variable, i.e. a value that can be referred
 * to by name. Variables include params, injected params, and local vars. Note
 * that a definition does not always have a corresponding declaration in user
 * code. Some definitions are implicit, e.g. in the case of injected params.
 *
 */
public interface VarDefn {
  /**
   * Enum used to distinguish subtypes.
   */
  enum Kind {
    // Explicitly declared parameter.
    PARAM,
    // Injected parameter.
    IJ_PARAM,
    // Local variable
    LOCAL_VAR,
    // Undeclared variable reference (for legacy templates).
    UNDECLARED,
  }

  /** What kind of variable this is (param, local var, etc). */
  Kind kind();

  /** The name of this variable. */
  String name();

  /** Returns the data type of this variable. */
  SoyType type();

  /** Returns true if this is an {@code $ij} variable or an {@code @inject} param. */
  boolean isInjected();

  /**
   * Returns the index of this variable in the local variable table of the template or {@code -1}
   * for {@link Kind#IJ_PARAM ij params}.
   */
  int localVariableIndex();

  /** Assigns the index of this variable in the local variable table for its containing template. */
  void setLocalVariableIndex(int i);
}