io.github.linuxforhealth.api.Expression Maven / Gradle / Ivy

/*
 * (C) Copyright IBM Corp. 2020
 *
 * SPDX-License-Identifier: Apache-2.0
 */
package io.github.linuxforhealth.api;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Each expression defines how to extract the value for a field. The execute method defines the
 * extraction process.
 * 
 *
 * @author pbhallam
 */

public interface Expression {
  /**
   * Defines the return type of the object value evaluated/extracted.
   * 
   * @return Return the type of the expression
   */
  String getType();

  /**
   * Specifies the default value for the field that should be returned if the evaluated value is
   * null
   * 
   * @return {@link EvaluationResult}
   */
  EvaluationResult getDefaultValue();

  /**
   * List of Specification values that would be passed to the Evaluator to extract value.
   * 
   * @return List {@link Specification}
   */
  List getspecs();

  /**
   * Evaluates the expression and returns the GenericResult Object
   * 
   * @param primaryDataSource {@link InputDataExtractor} input data
   * @param contextValues - Map of values for variables
   * @param baseValue {@link EvaluationResult}
   * @return {@link EvaluationResult}
   */
  EvaluationResult evaluate(InputDataExtractor primaryDataSource,
      Map contextValues, EvaluationResult baseValue);

  /**
   * Evaluates an expression if the condition is satisfied
   * 
   * @param contextValues {@link Map}
   * @return true if condition satisfied otherwise returns false;
   */
  default boolean isConditionSatisfied(Map contextValues) {
    return true;
  }


  /**
   * List of Variables values that would be evaluated prior to evaluating the expression and these
   * values extracted from variables will be utilized during expression evaluation. Extracted
   * variables are added to context map.
   * 
   * @return List {@link Variable}
   */
  default List getVariables() {
    return new ArrayList<>();
  }


  /**
   * List of constant string values that would be added to context map prior to the evaluating the
   * variables.
   * 
   * @return List {@link String}
   */
  default Map getConstants() {
    return new HashMap<>();
  }

  /**
   * 
   * 
   * @return true if the expression should be evaluated at the end after all resources are
   *         generated. {@link boolean}
   */
  default boolean isEvaluateLater() {
    return false;

  }


}