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/*
 * Copyright (C) 2005, The Beangle Software.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see .
 */

package org.beangle.commons.script

import javax.script.{ScriptEngine, ScriptEngineManager, SimpleBindings}

/** 表达式执行器
 *
 * @author chaostone
 * @since 2012-03-05
 */
trait ExpressionEvaluator {

  /** Parse the expression
   *
   * @param exp
   * @throws EvaluationException
   */
  def parse(exp: String): Unit

  /** Eval a expression within context
   *
   * @param exp  a java's expression
   * @param root params.
   * @return evaluate result
   */
  def eval(exp: String, root: AnyRef): AnyRef

  /** Eval a expression within context,Return the given type
   *
   * @param exp        a java's expression
   * @param root       params.
   * @param resultType What type of the result
   * @return evaluate result
   */
  def eval[T](exp: String, root: AnyRef, resultType: Class[T]): T
}

object ExpressionEvaluator {
  def jsr223(engineName: String): ExpressionEvaluator = {
    new JSR223ExpressionEvaluator(new ScriptEngineManager().getEngineByName(engineName))
  }
}

class JSR223ExpressionEvaluator(engine: ScriptEngine) extends ExpressionEvaluator {
  def parse(exp: String): Unit = {}

  def eval(exp: String, root: AnyRef): AnyRef = {
    val ctx = new SimpleBindings
    root match {
      case sm: collection.Map[_, _] => sm foreach (x => ctx.put(x._1.toString, x._2))
      case jm: java.util.Map[_, _] =>
        val jmi = jm.entrySet().iterator()
        while (jmi.hasNext) {
          val i = jmi.next()
          ctx.put(i.getKey.toString, i.getValue)
        }
      case _ => ctx.put("root", root)
    }
    engine.eval(exp, ctx)
  }

  def eval[T](exp: String, root: AnyRef, resultType: Class[T]): T = {
    eval(exp, root).asInstanceOf[T]
  }
}