/*
 * Copyright (C) 2009 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.caliper;

import com.google.common.annotations.VisibleForTesting;

import java.lang.reflect.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * A parameter in a {@link SimpleBenchmark}.
 *
 * @param <T> the (possibly wrapped) type of the parameter field, such as {@link
 *     String} or {@link Integer}
 */
abstract class Parameter<T> {

  private final Field field;

  private Parameter(Field field) {
    this.field = field;
  }

  /**
   * Returns all parameters for the given class.
   */
  public static Map<String, Parameter<?>> forClass(Class<? extends Benchmark> suiteClass) {
    Map<String, Parameter<?>> parameters = new TreeMap<String, Parameter<?>>();
    for (Field field : suiteClass.getDeclaredFields()) {
      if (field.isAnnotationPresent(Param.class)) {
        field.setAccessible(true);
        Parameter<?> parameter = forField(suiteClass, field);
        parameters.put(parameter.getName(), parameter);
      }
    }
    return parameters;
  }

  @VisibleForTesting
  static Parameter<?> forField(
      Class<? extends Benchmark> suiteClass, final Field field) {
    // First check for String values on the annotation itself
    final Object[] defaults = field.getAnnotation(Param.class).value();
    if (defaults.length > 0) {
      return new Parameter<Object>(field) {
        @Override public Iterable<Object> values() throws Exception {
          return Arrays.asList(defaults);
        }
      };
      // TODO: or should we continue so we can give an error/warning if params are also give in a
      // method or field?
    }

    Parameter<?> result = null;
    Type returnType = null;
    Member member = null;

    // Now check for a fooValues() method
    try {
      final Method valuesMethod = suiteClass.getDeclaredMethod(field.getName() + "Values");
      if (!Modifier.isStatic(valuesMethod.getModifiers())) {
        throw new ConfigurationException("Values method must be static " + member);
      }
      valuesMethod.setAccessible(true);
      member = valuesMethod;
      returnType = valuesMethod.getGenericReturnType();
      result = new Parameter<Object>(field) {
        @SuppressWarnings("unchecked") // guarded below
        @Override public Iterable<Object> values() throws Exception {
          return (Iterable<Object>) valuesMethod.invoke(null);
        }
      };
    } catch (NoSuchMethodException ignored) {
    }

    // Now check for a fooValues field
    try {
      final Field valuesField = suiteClass.getDeclaredField(field.getName() + "Values");
      if (!Modifier.isStatic(valuesField.getModifiers())) {
        throw new ConfigurationException("Values field must be static " + member);
      }
      valuesField.setAccessible(true);
      member = valuesField;
      if (result != null) {
        throw new ConfigurationException("Two values members defined for " + field);
      }
      returnType = valuesField.getGenericType();
      result = new Parameter<Object>(field) {
        @SuppressWarnings("unchecked") // guarded below
        @Override public Iterable<Object> values() throws Exception {
          return (Iterable<Object>) valuesField.get(null);
        }
      };
    } catch (NoSuchFieldException ignored) {
    }

    // If there isn't a values member but the parameter is an enum, we default
    // to EnumSet.allOf.
    if (member == null && field.getType().isEnum()) {
      returnType = Collection.class;
      result = new Parameter<Object>(field) {
        // TODO: figure out the simplest way to make this compile and be green in IDEA too
        @SuppressWarnings({"unchecked", "RawUseOfParameterizedType", "RedundantCast"})
        // guarded above
        @Override public Iterable<Object> values() throws Exception {
          Set<Enum> set = EnumSet.allOf((Class<Enum>) field.getType());
          return Collections.<Object>unmodifiableSet(set);
        }
      };
    }

    // If it's boolean, default to (true, false)
    if (member == null && field.getType() == boolean.class) {
      returnType = Collection.class;
      result = new Parameter<Object>(field) {
        @Override public Iterable<Object> values() throws Exception {
          return Arrays.<Object>asList(Boolean.TRUE, Boolean.FALSE);
        }
      };
    }

    if (result == null) {
      return new Parameter<Object>(field) {
        @Override public Iterable<Object> values() {
          // TODO: need tests to make sure this fails properly when no cmdline params given and
          // works properly when they are given. Also, can we restructure the code so that we
          // just throw here instead of later?
          return Collections.emptySet();
        }
      };
    } else if (!isValidReturnType(returnType)) {
      throw new ConfigurationException("Invalid return type " + returnType
          + " for values member " + member + "; must be Collection");
    }
    return result;
  }

  private static boolean isValidReturnType(Type type) {
    if (type instanceof Class) {
      return isIterableClass(type);
    }
    if (type instanceof ParameterizedType) {
      return isIterableClass(((ParameterizedType) type).getRawType());
    }
    return false;
  }

  private static boolean isIterableClass(Type returnClass) {
    return Iterable.class.isAssignableFrom((Class<?>) returnClass);
  }

  /**
   * Sets the value of this property to the specified value for the given suite.
   */
  public void set(Benchmark suite, Object value) throws Exception {
    field.set(suite, value);
  }

  /**
   * Returns the available values of the property as specified by the suite.
   */
  public abstract Iterable<T> values() throws Exception;

  /**
   * Returns the parameter's type, such as double.class.
   */
  public Type getType() {
    return field.getGenericType();
  }

  /**
   * Returns the field's name.
   */
  String getName() {
    return field.getName();
  }
}