/*
 * 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.juneau.cp;

import static java.util.stream.Collectors.*;
import static java.util.stream.Collectors.toList;
import static org.apache.juneau.commons.reflect.ReflectionUtils.*;
import static org.apache.juneau.commons.utils.CollectionUtils.*;
import static org.apache.juneau.commons.utils.ThrowableUtils.*;
import static org.apache.juneau.commons.utils.Utils.*;

import java.util.*;
import java.util.concurrent.*;

import java.util.function.*;
import java.util.stream.*;

import org.apache.juneau.commons.collections.*;
import org.apache.juneau.commons.concurrent.*;
import org.apache.juneau.commons.reflect.*;

/**
 * Java bean store.
 *
 * <p>
 * A simple storage database for beans keyed by type and name.
 * Used to retrieve and instantiate beans using an injection-like API.
 * It's similar in concept to the injection framework of Spring but greatly simplified in function and not intended to implement a full-fledged injection framework.
 *
 * <p>
 * Beans can be stored with or without names.  Named beans are typically resolved using
 * the <ja>@Name</ja> or <ja>@Qualified</ja> annotations on constructor or method parameters.
 *
 * <p>
 * Beans are added through the following methods:
 * <ul class='javatreec'>
 *    <li class='jm'>{@link #add(Class,Object) add(Class,Object)}
 *    <li class='jm'>{@link #add(Class,Object,String) add(Class,Object,String)}
 *    <li class='jm'>{@link #addBean(Class,Object) addBean(Class,Object)}
 *    <li class='jm'>{@link #addBean(Class,Object,String) addBean(Class,Object,String)}
 *    <li class='jm'>{@link #addSupplier(Class,Supplier) addSupplier(Class,Supplier)}
 *    <li class='jm'>{@link #addSupplier(Class,Supplier,String) addSupplier(Class,Supplier,String)}
 * </ul>
 *
 * <p>
 * Beans are retrieved through the following methods:
 * <ul class='javatreec'>
 *    <li class='jm'>{@link #getBean(Class) getBean(Class)}
 *    <li class='jm'>{@link #getBean(Class,String) getBean(Class,String)}
 *    <li class='jm'>{@link #stream(Class) stream(Class)}
 * </ul>
 *
 * <p>
 * Beans are created through the following methods:
 * <ul class='javatreec'>
 *    <li class='jm'>{@link #createBean(Class) createBean(Class)}
 *    <li class='jm'>{@link #createMethodFinder(Class) createMethodFinder(Class)}
 *    <li class='jm'>{@link #createMethodFinder(Class,Class) createMethodFinder(Class,Class)}
 *    <li class='jm'>{@link #createMethodFinder(Class,Object) createMethodFinder(Class,Object)}
 * </ul>
 *
 * <h5 class='section'>Notes:</h5><ul>
 *    <li class='note'>Bean stores can be nested using {@link Builder#parent(BeanStore)}.
 *    <li class='note'>Bean stores can be made read-only using {@link Builder#readOnly()}.
 *    <li class='note'>Bean stores can be made thread-safe using {@link Builder#threadSafe()}.
 * </ul>
 *
 */
public class BeanStore {
   /**
    * Builder class.
    */
   public static class Builder {

      BeanStore parent;
      boolean readOnly, threadSafe;
      Object outer;
      Class<? extends BeanStore> type;
      BeanStore impl;

      /**
       * Constructor.
       */
      protected Builder() {}

      /**
       * Instantiates this bean store.
       *
       * @return A new bean store.
       */
      public BeanStore build() {
         if (nn(impl))
            return impl;
         if (type == null || type == BeanStore.class)
            return new BeanStore(this);

         var c = info(type);

         // @formatter:off
         var result = c.getDeclaredMethod(
            x -> x.isPublic()
            && x.getParameterCount() == 0
            && x.isStatic()
            && x.hasName("getInstance")
         ).map(m -> m.<BeanStore>invoke(null));
         // @formatter:on
         if (result.isPresent())
            return result.get();

         result = c.getPublicConstructor(x -> x.canAccept(this)).map(ci -> ci.<BeanStore>newInstance(this));
         if (result.isPresent())
            return result.get();

         result = c.getDeclaredConstructor(x -> x.isProtected() && x.canAccept(this)).map(ci -> ci.accessible().<BeanStore>newInstance(this));
         if (result.isPresent())
            return result.get();

         throw rex("Could not find a way to instantiate class {0}", cn(type));
      }

      /**
       * Overrides the bean to return from the {@link #build()} method.
       *
       * @param value The bean to return from the {@link #build()} method.
       * @return This object.
       */
      public Builder impl(BeanStore value) {
         impl = value;
         return this;
      }

      /**
       * Specifies the outer bean context.
       *
       * <p>
       * The outer context bean to use when calling constructors on inner classes.
       *
       * @param value The outer bean context.  Can be <jk>null</jk>.
       * @return  This object.
       */
      public Builder outer(Object value) {
         outer = value;
         return this;
      }

      /**
       * Specifies the parent bean store.
       *
       * <p>
       * Bean searches are performed recursively up this parent chain.
       *
       * @param value The setting value.
       * @return  This object.
       */
      public Builder parent(BeanStore value) {
         parent = value;
         return this;
      }

      /**
       * Specifies that the bean store is read-only.
       *
       * <p>
       * This means methods such as {@link BeanStore#addBean(Class, Object)} cannot be used.
       *
       * @return  This object.
       */
      public Builder readOnly() {
         readOnly = true;
         return this;
      }

      /**
       * Specifies that the bean store being created should be thread-safe.
       *
       * @return  This object.
       */
      public Builder threadSafe() {
         threadSafe = true;
         return this;
      }

      /**
       * Overrides the bean store type.
       *
       * <p>
       * The specified type must have one of the following:
       * <ul>
       *    <li>A static <c>getInstance()</c> method.
       *    <li>A public constructor that takes in this builder.
       *    <li>A protected constructor that takes in this builder.
       * </ul>
       *
       * @param value The bean store type.
       * @return This object.
       */
      public Builder type(Class<? extends BeanStore> value) {
         type = value;
         return this;
      }
   }

   /**
    * Non-existent bean store.
    */
   public static final class Void extends BeanStore {}

   /**
    * Static read-only reusable instance.
    */
   public static final BeanStore INSTANCE = create().readOnly().build();

   /**
    * Static creator.
    *
    * @return A new {@link Builder} object.
    */
   public static Builder create() {
      return new Builder();
   }

   /**
    * Static creator.
    *
    * @param parent Parent bean store.  Can be <jk>null</jk> if this is the root resource.
    * @return A new {@link BeanStore} object.
    */
   public static BeanStore of(BeanStore parent) {
      return create().parent(parent).build();
   }

   /**
    * Static creator.
    *
    * @param parent Parent bean store.  Can be <jk>null</jk> if this is the root resource.
    * @param outer The outer bean used when instantiating inner classes.  Can be <jk>null</jk>.
    * @return A new {@link BeanStore} object.
    */
   public static BeanStore of(BeanStore parent, Object outer) {
      return create().parent(parent).outer(outer).build();
   }

   private final Deque<BeanStoreEntry<?>> entries;
   private final Map<Class<?>,BeanStoreEntry<?>> unnamedEntries;

   final Optional<BeanStore> parent;
   final Optional<Object> outer;
   final boolean readOnly, threadSafe;
   final SimpleReadWriteLock lock;

   /**
    * Constructor.
    *
    * @param builder The builder containing the settings for this bean.
    */
   protected BeanStore(Builder builder) {
      parent = opt(builder.parent);
      outer = opt(builder.outer);
      readOnly = builder.readOnly;
      threadSafe = builder.threadSafe;
      lock = threadSafe ? new SimpleReadWriteLock() : SimpleReadWriteLock.NO_OP;
      entries = threadSafe ? new ConcurrentLinkedDeque<>() : new LinkedList<>();
      unnamedEntries = threadSafe ? new ConcurrentHashMap<>() : map();
   }

   BeanStore() {
      this(create());
   }

   /**
    * Same as {@link #addBean(Class,Object)} but returns the bean instead of this object for fluent calls.
    *
    * @param <T> The class to associate this bean with.
    * @param beanType The class to associate this bean with.
    * @param bean The bean.  Can be <jk>null</jk>.
    * @return The bean.
    */
   public <T> T add(Class<T> beanType, T bean) {
      add(beanType, bean, null);
      return bean;
   }

   /**
    * Same as {@link #addBean(Class,Object,String)} but returns the bean instead of this object for fluent calls.
    *
    * @param <T> The class to associate this bean with.
    * @param beanType The class to associate this bean with.
    * @param bean The bean.  Can be <jk>null</jk>.
    * @param name The bean name if this is a named bean.  Can be <jk>null</jk>.
    * @return The bean.
    */
   public <T> T add(Class<T> beanType, T bean, String name) {
      addBean(beanType, bean, name);
      return bean;
   }

   /**
    * Adds an unnamed bean of the specified type to this factory.
    *
    * @param <T> The class to associate this bean with.
    * @param beanType The class to associate this bean with.
    * @param bean The bean.  Can be <jk>null</jk>.
    * @return This object.
    */
   public <T> BeanStore addBean(Class<T> beanType, T bean) {
      return addBean(beanType, bean, null);
   }

   /**
    * Adds a named bean of the specified type to this factory.
    *
    * @param <T> The class to associate this bean with.
    * @param beanType The class to associate this bean with.
    * @param bean The bean.  Can be <jk>null</jk>.
    * @param name The bean name if this is a named bean.  Can be <jk>null</jk>.
    * @return This object.
    */
   public <T> BeanStore addBean(Class<T> beanType, T bean, String name) {
      return addSupplier(beanType, () -> bean, name);
   }

   /**
    * Adds a supplier for an unnamed bean of the specified type to this factory.
    *
    * @param <T> The class to associate this bean with.
    * @param beanType The class to associate this bean with.
    * @param bean The bean supplier.
    * @return This object.
    */
   public <T> BeanStore addSupplier(Class<T> beanType, Supplier<T> bean) {
      return addSupplier(beanType, bean, null);
   }

   /**
    * Adds a supplier for a named bean of the specified type to this factory.
    *
    * @param <T> The class to associate this bean with.
    * @param beanType The class to associate this bean with.
    * @param bean The bean supplier.
    * @param name The bean name if this is a named bean.  Can be <jk>null</jk>.
    * @return This object.
    */
   public <T> BeanStore addSupplier(Class<T> beanType, Supplier<T> bean, String name) {
      assertCanWrite();
      var e = createEntry(beanType, bean, name);
      try (var x = lock.write()) {
         entries.addFirst(e);
         if (e(name))
            unnamedEntries.put(beanType, e);
      }
      return this;
   }

   /**
    * Clears out all bean in this bean store.
    *
    * <p>
    * Does not affect the parent bean store.
    *
    * @return This object.
    */
   public BeanStore clear() {
      assertCanWrite();
      try (var x = lock.write()) {
         unnamedEntries.clear();
         entries.clear();
      }
      return this;
   }

   /**
    * Instantiates a bean creator.
    *
    * <h5 class='section'>See Also:</h5><ul>
    *    <li class='jc'>{@link BeanCreator} for usage.
    * </ul>
    *
    * @param <T> The bean type to create.
    * @param beanType The bean type to create.
    * @return A new bean creator.
    */
   public <T> BeanCreator<T> createBean(Class<T> beanType) {
      return new BeanCreator<>(beanType, this);
   }

   /**
    * Create a method finder for finding bean creation methods.
    *
    * <p>
    * Same as {@link #createMethodFinder(Class,Object)} but uses {@link Builder#outer(Object)} as the resource bean.
    *
    * <h5 class='section'>See Also:</h5><ul>
    *    <li class='jc'>{@link BeanCreateMethodFinder} for usage.
    * </ul>
    *
    * @param <T> The bean type to create.
    * @param beanType The bean type to create.
    * @return The method finder.  Never <jk>null</jk>.
    */
   public <T> BeanCreateMethodFinder<T> createMethodFinder(Class<T> beanType) {
      return new BeanCreateMethodFinder<>(beanType, outer.orElseThrow(() -> new IllegalArgumentException("Method cannot be used without outer bean definition.")), this);
   }

   /**
    * Create a method finder for finding bean creation methods.
    *
    * <p>
    * Same as {@link #createMethodFinder(Class,Class)} but looks for only static methods on the specified resource class
    * and not also instance methods within the context of a bean.
    *
    * <h5 class='section'>See Also:</h5><ul>
    *    <li class='jc'>{@link BeanCreateMethodFinder} for usage.
    * </ul>
    *
    * @param <T> The bean type to create.
    * @param beanType The bean type to create.
    * @param resourceClass The class containing the bean creator method.
    * @return The method finder.  Never <jk>null</jk>.
    */
   public <T> BeanCreateMethodFinder<T> createMethodFinder(Class<T> beanType, Class<?> resourceClass) {
      return new BeanCreateMethodFinder<>(beanType, resourceClass, this);
   }

   /**
    * Create a method finder for finding bean creation methods.
    *
    * <h5 class='section'>See Also:</h5><ul>
    *    <li class='jc'>{@link BeanCreateMethodFinder} for usage.
    * </ul>
    *
    * @param <T> The bean type to create.
    * @param beanType The bean type to create.
    * @param resource The class containing the bean creator method.
    * @return The method finder.  Never <jk>null</jk>.
    */
   public <T> BeanCreateMethodFinder<T> createMethodFinder(Class<T> beanType, Object resource) {
      return new BeanCreateMethodFinder<>(beanType, resource, this);
   }

   /**
    * Returns the unnamed bean of the specified type.
    *
    * @param <T> The type of bean to return.
    * @param beanType The type of bean to return.
    * @return The bean.
    */
   @SuppressWarnings("unchecked")
   public <T> Optional<T> getBean(Class<T> beanType) {
      try (var x = lock.read()) {
         var e = (BeanStoreEntry<T>)unnamedEntries.get(beanType);
         if (nn(e))
            return opt(e.get());
         if (parent.isPresent())
            return parent.get().getBean(beanType);
         return opte();
      }
   }

   /**
    * Returns the named bean of the specified type.
    *
    * @param <T> The type of bean to return.
    * @param beanType The type of bean to return.
    * @param name The bean name.  Can be <jk>null</jk>.
    * @return The bean.
    */
   @SuppressWarnings("unchecked")
   public <T> Optional<T> getBean(Class<T> beanType, String name) {
      try (var x = lock.read()) {
         var e = (BeanStoreEntry<T>)entries.stream().filter(x2 -> x2.matches(beanType, name)).findFirst().orElse(null);
         if (nn(e))
            return opt(e.get());
         if (parent.isPresent())
            return parent.get().getBean(beanType, name);
         return opte();
      }
   }

   /**
    * Given an executable, returns a list of types that are missing from this factory.
    *
    * @param executable The constructor or method to get the params for.
    * @return A comma-delimited list of types that are missing from this factory, or <jk>null</jk> if none are missing.
    */
   public String getMissingParams(ExecutableInfo executable) {
      var params = executable.getParameters();
      List<String> l = list();
      loop: for (int i = 0; i < params.size(); i++) {
         var pi = params.get(i);
         var pt = pi.getParameterType();
         if (i == 0 && outer.isPresent() && pt.isInstance(outer.get()))
            continue loop;
         if (pt.is(Optional.class) || pt.is(BeanStore.class))
            continue loop;
         var beanName = pi.getResolvedQualifier();  // Use @Named for bean injection
         var ptc = pt.inner();
         if (beanName == null && ! hasBean(ptc))
            l.add(pt.getNameSimple());
         if (nn(beanName) && ! hasBean(ptc, beanName))
            l.add(pt.getNameSimple() + '@' + beanName);
      }
      return l.isEmpty() ? null : l.stream().sorted().collect(joining(","));
   }

   /**
    * Returns the corresponding beans in this factory for the specified param types.
    *
    * @param executable The constructor or method to get the params for.
    * @return The corresponding beans in this factory for the specified param types.
    */
   public Object[] getParams(ExecutableInfo executable) {
      var o = new Object[executable.getParameterCount()];
      for (var i = 0; i < executable.getParameterCount(); i++) {
         var pi = executable.getParameter(i);
         var pt = pi.getParameterType();
         if (i == 0 && outer.isPresent() && pt.isInstance(outer.get())) {
            o[i] = outer.get();
         } else if (pt.is(BeanStore.class)) {
            o[i] = this;
         } else {
            var beanQualifier = pi.getResolvedQualifier();
            var ptc = pt.unwrap(Optional.class).inner();
            var o2 = beanQualifier == null ? getBean(ptc) : getBean(ptc, beanQualifier);
            o[i] = pt.is(Optional.class) ? o2 : o2.orElse(null);
         }
      }
      return o;
   }

   /**
    * Given the list of param types, returns <jk>true</jk> if this factory has all the parameters for the specified executable.
    *
    * @param executable The constructor or method to get the params for.
    * @return A comma-delimited list of types that are missing from this factory.
    */
   public boolean hasAllParams(ExecutableInfo executable) {
      loop: for (int i = 0; i < executable.getParameterCount(); i++) {
         var pi = executable.getParameter(i);
         var pt = pi.getParameterType();
         if (i == 0 && outer.isPresent() && pt.isInstance(outer.get()))
            continue loop;
         if (pt.is(Optional.class) || pt.is(BeanStore.class))
            continue loop;
         var beanQualifier = pi.getResolvedQualifier();
         var ptc = pt.inner();
         if ((beanQualifier == null && ! hasBean(ptc)) || (nn(beanQualifier) && ! hasBean(ptc, beanQualifier)))
            return false;
      }
      return true;
   }

   /**
    * Returns <jk>true</jk> if this store contains the specified unnamed bean type.
    *
    * @param beanType The bean type to check.
    * @return <jk>true</jk> if this store contains the specified unnamed bean type.
    */
   public boolean hasBean(Class<?> beanType) {
      return unnamedEntries.containsKey(beanType) || parent.map(x -> x.hasBean(beanType)).orElse(false);
   }

   /**
    * Returns <jk>true</jk> if this store contains the specified named bean type.
    *
    * @param beanType The bean type to check.
    * @param name The bean name.
    * @return <jk>true</jk> if this store contains the specified named bean type.
    */
   public boolean hasBean(Class<?> beanType, String name) {
      return entries.stream().anyMatch(x -> x.matches(beanType, name)) || parent.map(x -> x.hasBean(beanType, name)).orElse(false);
   }

   /**
    * Removes an unnamed bean from this store.
    *
    * @param beanType The bean type being removed.
    * @return This object.
    */
   public BeanStore removeBean(Class<?> beanType) {
      return removeBean(beanType, null);
   }

   /**
    * Removes a named bean from this store.
    *
    * @param beanType The bean type being removed.
    * @param name The bean name to remove.
    * @return This object.
    */
   public BeanStore removeBean(Class<?> beanType, String name) {
      assertCanWrite();
      try (var x = lock.write()) {
         if (name == null)
            unnamedEntries.remove(beanType);
         entries.removeIf(y -> y.matches(beanType, name));
      }
      return this;
   }

   /**
    * Returns all the beans in this store of the specified type.
    *
    * <p>
    * Returns both named and unnamed beans.
    *
    * <p>
    * The results from the parent bean store are appended to the list of beans from this beans store.
    *
    * @param <T> The bean type to return.
    * @param beanType The bean type to return.
    * @return The bean entries.  Never <jk>null</jk>.
    */
   public <T> Stream<BeanStoreEntry<T>> stream(Class<T> beanType) {
      @SuppressWarnings("unchecked")
      var s = entries.stream().filter(x -> x.matches(beanType)).map(x -> (BeanStoreEntry<T>)x);
      if (parent.isPresent())
         s = Stream.concat(s, parent.get().stream(beanType));
      return s;
   }

   protected FluentMap<String,Object> properties() {
      // @formatter:off
      return filteredBeanPropertyMap()
         .a("entries", entries.stream().map(BeanStoreEntry::properties).collect(toList()))
         .a("identity", id(this))
         .a("outer", id(outer.orElse(null)))
         .a("parent", parent.map(BeanStore::properties).orElse(null))
         .ai(readOnly, "readOnly", readOnly)
         .ai(threadSafe, "threadSafe", threadSafe);
      // @formatter:on
   }

   @Override /* Overridden from Object */
   public String toString() {
      return r(properties());
   }

   private void assertCanWrite() {
      if (readOnly)
         throw new IllegalStateException("Method cannot be used because BeanStore is read-only.");
   }

   /**
    * Creates an entry in this store for the specified bean.
    *
    * <p>
    * Subclasses can override this method to create their own entry subtypes.
    *
    * @param <T> The class type to associate with the bean.
    * @param type The class type to associate with the bean.
    * @param bean The bean supplier.
    * @param name Optional name to associate with the bean.  Can be <jk>null</jk>.
    * @return A new bean store entry.
    */
   protected <T> BeanStoreEntry<T> createEntry(Class<T> type, Supplier<T> bean, String name) {
      return BeanStoreEntry.create(type, bean, name);
   }
}