/*
    * 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.maven.di.impl;
  
  import java.io.BufferedReader;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.lang.annotation.Annotation;
  import java.lang.reflect.Method;
  import java.lang.reflect.Modifier;
  import java.lang.reflect.Type;
  import java.net.URL;
  import java.util.AbstractList;
  import java.util.AbstractMap;
  import java.util.AbstractSet;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Comparator;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.function.Function;
  import java.util.function.Supplier;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.apache.maven.api.annotations.Nonnull;
  import org.apache.maven.api.di.Provides;
  import org.apache.maven.api.di.Qualifier;
  import org.apache.maven.api.di.Singleton;
  import org.apache.maven.api.di.Typed;
  import org.apache.maven.di.Injector;
  import org.apache.maven.di.Key;
  import org.apache.maven.di.Scope;
  
  public class InjectorImpl implements Injector {
  
      private final Map<Key<?>, Set<Binding<?>>> bindings = new HashMap<>();
      private final Map<Class<? extends Annotation>, Supplier<Scope>> scopes = new HashMap<>();
      private final Set<String> loadedUrls = new HashSet<>();
  
      public InjectorImpl() {
          bindScope(Singleton.class, new SingletonScope());
      }
  
      @Nonnull
      @Override
      public <T> T getInstance(@Nonnull Class<T> key) {
          return getInstance(Key.of(key));
      }
  
      @Nonnull
      @Override
      public <T> T getInstance(@Nonnull Key<T> key) {
          return getCompiledBinding(new Dependency<>(key, false)).get();
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public <T> void injectInstance(@Nonnull T instance) {
          ReflectionUtils.generateInjectingInitializer(Key.of((Class<T>) instance.getClass()))
                  .compile(this::getCompiledBinding)
                  .accept(instance);
      }
  
      @Nonnull
      @Override
      public Injector discover(@Nonnull ClassLoader classLoader) {
          try {
              Enumeration<URL> enumeration = classLoader.getResources("META-INF/maven/org.apache.maven.api.di.Inject");
              while (enumeration.hasMoreElements()) {
                  URL url = enumeration.nextElement();
                  if (loadedUrls.add(url.toExternalForm())) {
                      try (InputStream is = url.openStream();
                              BufferedReader reader =
                                      new BufferedReader(new InputStreamReader(Objects.requireNonNull(is)))) {
                         for (String line :
                                 reader.lines().filter(l -> !l.startsWith("#")).toList()) {
                             Class<?> clazz = classLoader.loadClass(line);
                             bindImplicit(clazz);
                         }
                     }
                 }
             }
         } catch (Exception e) {
             throw new DIException("Error while discovering DI classes from classLoader", e);
         }
         return this;
     }
 
     @Nonnull
     @Override
     public Injector bindScope(@Nonnull Class<? extends Annotation> scopeAnnotation, @Nonnull Scope scope) {
         return bindScope(scopeAnnotation, () -> scope);
     }
 
     @Nonnull
     @Override
     public Injector bindScope(@Nonnull Class<? extends Annotation> scopeAnnotation, @Nonnull Supplier<Scope> scope) {
         if (scopes.put(scopeAnnotation, scope) != null) {
             throw new DIException(
                     "Cannot rebind scope annotation class to a different implementation: " + scopeAnnotation);
         }
         return this;
     }
 
     @Nonnull
     @Override
     public <U> Injector bindInstance(@Nonnull Class<U> clazz, @Nonnull U instance) {
         Key<?> key = Key.of(clazz, ReflectionUtils.qualifierOf(clazz));
         Binding<U> binding = Binding.toInstance(instance);
         return doBind(key, binding);
     }
 
     @Nonnull
     @Override
     public Injector bindImplicit(@Nonnull Class<?> clazz) {
         Key<?> key = Key.of(clazz, ReflectionUtils.qualifierOf(clazz));
         if (clazz.isInterface()) {
             bindings.computeIfAbsent(key, $ -> new HashSet<>());
             if (key.getQualifier() != null) {
                 bindings.computeIfAbsent(Key.ofType(clazz), $ -> new HashSet<>());
             }
         } else if (!Modifier.isAbstract(clazz.getModifiers())) {
             Binding<?> binding = ReflectionUtils.generateImplicitBinding(key);
             doBind(key, binding);
         }
         return this;
     }
 
     private final LinkedHashSet<Key<?>> current = new LinkedHashSet<>();
 
     private Injector doBind(Key<?> key, Binding<?> binding) {
         if (!current.add(key)) {
             current.add(key);
             throw new DIException("Circular references: " + current);
         }
         try {
             doBindImplicit(key, binding);
             Class<?> cls = key.getRawType().getSuperclass();
             while (cls != Object.class && cls != null) {
                 doBindImplicit(Key.of(cls, key.getQualifier()), binding);
                 if (key.getQualifier() != null) {
                     bind(Key.ofType(cls), binding);
                 }
                 cls = cls.getSuperclass();
             }
             return this;
         } finally {
             current.remove(key);
         }
     }
 
     protected <U> Injector bind(Key<U> key, Binding<U> b) {
         Set<Binding<?>> bindingSet = bindings.computeIfAbsent(key, $ -> new HashSet<>());
         bindingSet.add(b);
         return this;
     }
 
     @SuppressWarnings({"unchecked", "rawtypes"})
     protected <T> Set<Binding<T>> getBindings(Key<T> key) {
         return (Set) bindings.get(key);
     }
 
     protected Set<Key<?>> getBoundKeys() {
         return bindings.keySet();
     }
 
     public Map<Key<?>, Set<Binding<?>>> getBindings() {
         return bindings;
     }
 
     public <Q> Supplier<Q> getCompiledBinding(Dependency<Q> dep) {
         Key<Q> key = dep.key();
         Set<Binding<Q>> res = getBindings(key);
         if (res != null && !res.isEmpty()) {
             List<Binding<Q>> bindingList = new ArrayList<>(res);
             Comparator<Binding<Q>> comparing = Comparator.comparing(Binding::getPriority);
             bindingList.sort(comparing.reversed());
             Binding<Q> binding = bindingList.get(0);
             return compile(binding);
         }
         if (key.getRawType() == List.class) {
             Set<Binding<Object>> res2 = getBindings(key.getTypeParameter(0));
             if (res2 != null) {
                 List<Supplier<Object>> list = res2.stream().map(this::compile).collect(Collectors.toList());
                 //noinspection unchecked
                 return () -> (Q) list(list, Supplier::get);
             }
         }
         if (key.getRawType() == Map.class) {
             Key<?> k = key.getTypeParameter(0);
             Key<Object> v = key.getTypeParameter(1);
             Set<Binding<Object>> res2 = getBindings(v);
             if (k.getRawType() == String.class && res2 != null) {
                 Map<String, Supplier<Object>> map = res2.stream()
                         .filter(b -> b.getOriginalKey() == null
                                 || b.getOriginalKey().getQualifier() == null
                                 || b.getOriginalKey().getQualifier() instanceof String)
                         .collect(Collectors.toMap(
                                 b -> (String)
                                         (b.getOriginalKey() != null
                                                 ? b.getOriginalKey().getQualifier()
                                                 : null),
                                 this::compile));
                 //noinspection unchecked
                 return () -> (Q) map(map, Supplier::get);
             }
         }
         if (dep.optional()) {
             return () -> null;
         }
         throw new DIException("No binding to construct an instance for key "
                 + key.getDisplayString() + ".  Existing bindings:\n"
                 + getBoundKeys().stream()
                         .map(Key::toString)
                         .map(String::trim)
                         .sorted()
                         .distinct()
                         .collect(Collectors.joining("\n - ", " - ", "")));
     }
 
     @SuppressWarnings("unchecked")
     protected <Q> Supplier<Q> compile(Binding<Q> binding) {
         Supplier<Q> compiled = binding.compile(this::getCompiledBinding);
         if (binding.getScope() != null) {
             Scope scope = scopes.entrySet().stream()
                     .filter(e -> e.getKey().isInstance(binding.getScope()))
                     .map(Map.Entry::getValue)
                     .findFirst()
                     .orElseThrow(() -> new DIException("Scope not bound for annotation "
                             + binding.getScope().annotationType()))
                     .get();
             compiled = scope.scope((Key<Q>) binding.getOriginalKey(), compiled);
         }
         return compiled;
     }
 
     protected void doBindImplicit(Key<?> key, Binding<?> binding) {
         if (binding != null) {
             // For non-explicit bindings, also bind all their base classes and interfaces according to the @Type
             Object qualifier = key.getQualifier();
             Class<?> type = key.getRawType();
             Set<Class<?>> types = getBoundTypes(type.getAnnotation(Typed.class), type);
             for (Type t : Types.getAllSuperTypes(type)) {
                 if (types == null || types.contains(Types.getRawType(t))) {
                     bind(Key.ofType(t, qualifier), binding);
                     if (qualifier != null) {
                         bind(Key.ofType(t), binding);
                     }
                 }
             }
         }
         // Bind inner classes
         for (Class<?> inner : key.getRawType().getDeclaredClasses()) {
             boolean hasQualifier = Stream.of(inner.getAnnotations())
                     .anyMatch(ann -> ann.annotationType().isAnnotationPresent(Qualifier.class));
             if (hasQualifier) {
                 bindImplicit(inner);
             }
         }
         // Bind inner providers
         for (Method method : key.getRawType().getDeclaredMethods()) {
             if (method.isAnnotationPresent(Provides.class)) {
                 if (method.getTypeParameters().length != 0) {
                     throw new DIException("Parameterized method are not supported " + method);
                 }
                 Object qualifier = ReflectionUtils.qualifierOf(method);
                 Annotation scope = ReflectionUtils.scopeOf(method);
                 Type returnType = method.getGenericReturnType();
                 Set<Class<?>> types = getBoundTypes(method.getAnnotation(Typed.class), Types.getRawType(returnType));
                 Binding<Object> bind = ReflectionUtils.bindingFromMethod(method).scope(scope);
                 for (Type t : Types.getAllSuperTypes(returnType)) {
                     if (types == null || types.contains(Types.getRawType(t))) {
                         bind(Key.ofType(t, qualifier), bind);
                         if (qualifier != null) {
                             bind(Key.ofType(t), bind);
                         }
                     }
                 }
             }
         }
     }
 
     private static Set<Class<?>> getBoundTypes(Typed typed, Class<?> clazz) {
         if (typed != null) {
             Class<?>[] typesArray = typed.value();
             if (typesArray == null || typesArray.length == 0) {
                 Set<Class<?>> types = new HashSet<>(Arrays.asList(clazz.getInterfaces()));
                 types.add(Object.class);
                 return types;
             } else {
                 return new HashSet<>(Arrays.asList(typesArray));
             }
         } else {
             return null;
         }
     }
 
     protected <K, V, T> Map<K, V> map(Map<K, T> map, Function<T, V> mapper) {
         return new WrappingMap<>(map, mapper);
     }
 
     private static class WrappingMap<K, V, T> extends AbstractMap<K, V> {
 
         private final Map<K, T> delegate;
         private final Function<T, V> mapper;
 
         WrappingMap(Map<K, T> delegate, Function<T, V> mapper) {
             this.delegate = delegate;
             this.mapper = mapper;
         }
 
         @Override
         public Set<Entry<K, V>> entrySet() {
             return new AbstractSet<>() {
                 @Override
                 public Iterator<Entry<K, V>> iterator() {
                     Iterator<Entry<K, T>> it = delegate.entrySet().iterator();
                     return new Iterator<>() {
                         @Override
                         public boolean hasNext() {
                             return it.hasNext();
                         }
 
                         @Override
                         public Entry<K, V> next() {
                             Entry<K, T> n = it.next();
                             return new SimpleImmutableEntry<>(n.getKey(), mapper.apply(n.getValue()));
                         }
                     };
                 }
 
                 @Override
                 public int size() {
                     return delegate.size();
                 }
             };
         }
     }
 
     protected <Q, T> List<Q> list(List<T> bindingList, Function<T, Q> mapper) {
         return new WrappingList<>(bindingList, mapper);
     }
 
     private static class WrappingList<Q, T> extends AbstractList<Q> {
 
         private final List<T> delegate;
         private final Function<T, Q> mapper;
 
         WrappingList(List<T> delegate, Function<T, Q> mapper) {
             this.delegate = delegate;
             this.mapper = mapper;
         }
 
         @Override
         public Q get(int index) {
             return mapper.apply(delegate.get(index));
         }
 
         @Override
         public int size() {
             return delegate.size();
         }
     }
 
     private static class SingletonScope implements Scope {
         Map<Key<?>, java.util.function.Supplier<?>> cache = new ConcurrentHashMap<>();
 
         @Nonnull
         @SuppressWarnings("unchecked")
         @Override
         public <T> java.util.function.Supplier<T> scope(
                 @Nonnull Key<T> key, @Nonnull java.util.function.Supplier<T> unscoped) {
             return (java.util.function.Supplier<T>)
                     cache.computeIfAbsent(key, k -> new java.util.function.Supplier<T>() {
                         volatile T instance;
 
                         @Override
                         public T get() {
                             if (instance == null) {
                                 synchronized (this) {
                                     if (instance == null) {
                                         instance = unscoped.get();
                                     }
                                 }
                             }
                             return instance;
                         }
                     });
         }
     }
 }