content: /*
   * MIT License
   *
   * Copyright (c) 2020 Alen Turkovic
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   */
  
  package com.github.alturkovic.lock.key;
  
  import com.github.alturkovic.lock.exception.EvaluationConvertException;
  import java.lang.reflect.Method;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.stream.Collectors;
  import lombok.Data;
  import lombok.EqualsAndHashCode;
  import org.springframework.context.expression.AnnotatedElementKey;
  import org.springframework.context.expression.CachedExpressionEvaluator;
  import org.springframework.context.expression.MethodBasedEvaluationContext;
  import org.springframework.core.convert.ConversionService;
  import org.springframework.core.convert.TypeDescriptor;
  import org.springframework.expression.EvaluationContext;
  import org.springframework.expression.Expression;
  import org.springframework.util.CollectionUtils;
  import org.springframework.util.StringUtils;
  
  @Data
  @EqualsAndHashCode(callSuper = false)
  public class SpelKeyGenerator extends CachedExpressionEvaluator implements KeyGenerator {
    private final Map<ExpressionKey, Expression> conditionCache = new ConcurrentHashMap<>();
    private final ConversionService conversionService;
  
    @Override
    public List<String> resolveKeys(final String lockKeyPrefix, final String expression, final Object object, final Method method, final Object[] args) {
      final Object expressionValue = evaluateExpression(expression, object, method, args);
      final List<String> keys = convertResultToList(expressionValue);
  
      if (keys.stream().anyMatch(Objects::isNull)) {
        throw new EvaluationConvertException("null keys are not supported: " + keys);
      }
  
      if (StringUtils.isEmpty(lockKeyPrefix)) {
        return keys;
      }
  
      return keys.stream().map(key -> lockKeyPrefix + key).collect(Collectors.toList());
    }
  
    protected List<String> convertResultToList(final Object expressionValue) {
      final List<String> list;
      if (expressionValue instanceof Iterable) {
        list = iterableToList(expressionValue);
      } else if (expressionValue.getClass().isArray()) {
        list = arrayToList(expressionValue);
      } else {
        list = Collections.singletonList(expressionValue.toString());
      }
  
      if (CollectionUtils.isEmpty(list)) {
        throw new EvaluationConvertException("Expression evaluated in an empty list");
      }
  
      return list;
    }
  
    private Object evaluateExpression(final String expression, final Object object, final Method method, final Object[] args) {
      final EvaluationContext context = new MethodBasedEvaluationContext(object, method, args, super.getParameterNameDiscoverer());
      context.setVariable("executionPath", object.getClass().getCanonicalName() + "." + method.getName());
  
      final Expression evaluatedExpression = getExpression(this.conditionCache, new AnnotatedElementKey(method, object.getClass()), expression);
      final Object expressionValue = evaluatedExpression.getValue(context);
      if (expressionValue == null) {
        throw new EvaluationConvertException("Expression evaluated in a null");
      }
  
      return expressionValue;
    }
  
    private List<String> iterableToList(final Object expressionValue) {
      final TypeDescriptor genericCollection = TypeDescriptor.collection(Collection.class, TypeDescriptor.valueOf(Object.class));
      return toList(expressionValue, genericCollection);
    }
  
    private List<String> arrayToList(final Object expressionValue) {
      final TypeDescriptor genericArray = TypeDescriptor.array(TypeDescriptor.valueOf(Object.class));
      return toList(expressionValue, genericArray);
    }
  
    private List<String> toList(final Object expressionValue, final TypeDescriptor from) {
      final TypeDescriptor listTypeDescriptor = TypeDescriptor.collection(List.class, TypeDescriptor.valueOf(String.class));
      //noinspection unchecked
      return (List<String>) conversionService.convert(expressionValue, from, listTypeDescriptor);
    }
  }
  