/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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 org.apache.commons.jexl3;
  
  import java.util.concurrent.Callable;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * Manages variables which can be referenced in a JEXL expression.
   *
   * <p>JEXL variable names in their simplest form are 'java-like' identifiers.
   * JEXL also considers 'ant' inspired variables expressions as valid.
   * For instance, the expression 'x.y.z' is an 'antish' variable and will be resolved as a whole by the context,
   * i.e. using the key "x.y.z". This proves to be useful to solve "fully qualified class names".</p>
   *
   * <p>The interpreter variable resolution algorithm will try the different sequences of identifiers till it finds
   * one that exists in the context; if "x" is an object known in the context (JexlContext.has("x") returns true),
   * "x.y" will <em>not</em> be looked up in the context but will most likely refer to "x.getY()".</p>
   *
   * <p>Note that JEXL may use '$jexl' and '$ujexl' variables for internal purpose; setting or getting those
   * variables may lead to unexpected results unless specified otherwise.</p>
   *
   * @since 1.0
   */
  public interface JexlContext {
  
      /**
       * A marker interface of the JexlContext that processes annotations.
       * It is used by the interpreter during evaluation to execute annotation evaluations.
       * <p>If the JexlContext is not an instance of an AnnotationProcessor, encountering an annotation will generate
       * an error or a warning depending on the engine strictness.
       * @since 3.1
       */
      interface AnnotationProcessor {
          /**
           * Processes an annotation.
           * <p>All annotations are processed through this method; the statement 'call' is to be performed within
           * the processAnnotation method. The implementation <em>must</em> perform the call explicitly.
           * <p>The arguments and the statement <em>must not</em> be referenced or cached for longer than the duration
           * of the processAnnotation call.
           *
           * @param name the annotation name
           * @param args the arguments of the annotation, evaluated as arguments of this call
           * @param statement the statement that was annotated; the processor should invoke this statement 'call' method
           * @return the result of statement.call()
           * @throws Exception if annotation processing fails
           */
          Object processAnnotation(String name, Object[] args, Callable<Object> statement) throws Exception;
      }
  
      /**
       * A marker interface of the JexlContext sharing a cancelling flag.
       * <p>A script running in a thread can thus be notified through this reference
       * of its cancellation through the context. It uses the same interpreter logic
       * that reacts to cancellation and is an alternative to using callable() and/or
       * interrupting script interpreter threads.
       * @since 3.2
       */
      interface CancellationHandle {
          /**
           * Gets a cancelable boolean used by the interpreter
           * @return a cancelable boolean used by the interpreter
           */
          AtomicBoolean getCancellation();
      }
  
      /**
       * A marker interface that solves a simple class name into a fully-qualified one.
       * @since 3.3
       */
      interface ClassNameResolver {
          /**
           * Resolves a class name.
           * @param name the simple class name
           * @return the fully qualified class name
           */
          String resolveClassName(String name);
      }
  
      /**
       * A marker interface of the JexlContext that processes module definitions.
       * It is used by the interpreter during evaluation of the pragma module definitions.
       * @since 3.3
       */
     interface ModuleProcessor {
         /**
          * Defines a module.
          * The module name will be the namespace mapped to the object returned by the evaluation
          * of its body.
          * @param engine the engine evaluating this module pragma
          * @param info the info at the pragma location
          * @param name the module name
          * @param body the module definition which can be its location or source
          * @return the module object
          */
         Object processModule(JexlEngine engine, JexlInfo info, String name, String body);
     }
 
     /**
      * A marker interface of the JexlContext, NamespaceFunctor allows creating an instance
      * to delegate namespace methods calls to.
      *
      * <p>The functor is created once during the lifetime of a script evaluation.</p>
      */
     interface NamespaceFunctor {
         /**
          * Creates the functor object that will be used instead of the namespace.
          * @param context the context
          * @return the namespace functor instance
          */
         Object createFunctor(JexlContext context);
     }
 
     /**
      * A marker interface of the JexlContext that declares how to resolve a namespace from its name;
      * it is used by the interpreter during evaluation.
      *
      * <p>In JEXL, a namespace is an object that serves the purpose of encapsulating functions; for instance,
      * the "math" namespace would be the proper object to expose functions like "log(...)", "sinus(...)", etc.</p>
      *
      * In expressions like "ns:function(...)", the resolver is called with resolveNamespace("ns").
      *
      * <p>JEXL itself reserves 'jexl' and 'ujexl' as namespaces for internal purpose; resolving those may lead to
      * unexpected results.</p>
      *
      * @since 3.0
      */
     interface NamespaceResolver {
 
         /**
          * Resolves a namespace by its name.
          * @param name the name
          * @return the namespace object
          */
         Object resolveNamespace(String name);
     }
 
     /**
      * A marker interface of the JexlContext that exposes runtime evaluation options.
      * @since 3.2
      */
     interface OptionsHandle {
         /**
          * Retrieves the current set of options though the context.
          * <p>
          * This method will be called once at beginning of evaluation and an interpreter private copy
          * of the context handled JexlOptions instance used for the duration of the execution;
          * the context handled JexlOptions instance being only used as the source of that copy,
          * it can safely alter its boolean flags during execution with no effect, avoiding any behavior ambiguity.
          * @return the engine options
          */
         JexlOptions getEngineOptions();
     }
 
     /**
      * A marker interface of the JexlContext that processes pragmas.
      * It is called by the engine before interpreter creation; as a marker of
      * JexlContext, it is expected to have access and interact with the context
      * instance.
      * @since 3.2
      */
     interface PragmaProcessor {
         /**
          * Process one pragma.
          * @param opts the current evaluator options
          * @param key the key
          * @param value the value
          * @since 3.3
          */
         default void processPragma(final JexlOptions opts, final String key, final Object value) {
             processPragma(key, value);
         }
 
         /**
          * Process one pragma.
          * <p>Never called in 3.3, must be implemented for 3.2 binary compatibility reasons.</p>
          * <p>Typical implementation in 3.3:</p>
          * <code>
          *         &#64;Override
          *         public void processPragma(String key, Object value) {
          *             processPragma(null, key, value);
          *         }
          * </code>
          * @param key the key
          * @param value the value
          * @deprecated 3.3
          */
         @Deprecated
         void processPragma(String key, Object value);
     }
 
     /**
      * A marker interface  of the JexlContext that indicates the interpreter to put this context
      * in the JexlEngine thread local context instance during evaluation.
      * This allows user functions or methods to access the context during a call.
      * Note that the usual caveats wrt using thread local apply (caching/leaking references, etc.); in particular,
      * keeping a reference to such a context is to be considered with great care and caution.
      * It should also be noted that sharing such a context between threads should implicate synchronizing variable
      * accessing the implementation class.
      *
      * @see JexlEngine#setThreadContext(JexlContext.ThreadLocal)
      * @see JexlEngine#getThreadContext()
      */
     interface ThreadLocal extends JexlContext {
         // no specific method
     }
 
     /**
      * Gets the value of a variable.
      *
      * @param name the variable's name
      * @return the value
      */
     Object get(String name);
 
     /**
      * Checks whether a variable is defined in this context.
      *
      * <p>A variable may be defined with a null value; this method checks whether the
      * value is null or if the variable is undefined.</p>
      *
      * @param name the variable's name
      * @return true if it exists, false otherwise
      */
     boolean has(String name);
 
     /**
      * Sets the value of a variable.
      *
      * @param name the variable's name
      * @param value the variable's value
      */
     void set(String name, Object value);
 }