/*
 * 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.http;

import static org.apache.juneau.commons.utils.Shorts.*;

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

import org.apache.juneau.commons.httppart.*;
import org.apache.juneau.commons.lang.*;
import org.apache.juneau.commons.reflect.*;
import org.apache.juneau.http.part.*;
import org.apache.juneau.marshall.*;

/**
 * Static factory methods for creating HTTP parts (query parameters, form fields, path variables).
 *
 * <p>
 * Import statically for clean DSL-style usage:
 * <p class='bjava'>
 *    import static HttpParts.*;
 *
 *    PartList <jv>form</jv> = PartList.<jsm>of</jsm>(
 *       part(<js>"username"</js>, <js>"alice"</js>),
 *       part(<js>"password"</js>, <jv>passwordSupplier</jv>)
 *    );
 * </p>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/NextGenRestClient">Next-Generation REST Client</a>
 * </ul>
 *
 * @since 9.2.1
 */
public final class HttpParts {

   private HttpParts() {}

   /**
    * Creates an {@link HttpPart} with an eager string value.
    *
    * @param name The part name. Must not be <jk>null</jk>.
    * @param value The part value. May be <jk>null</jk>.
    * @return A new part. Never <jk>null</jk>.
    */
   public static HttpPart part(String name, String value) {
      return HttpPartBean.of(name, value);
   }

   /**
    * Creates an {@link HttpPart} with a lazy value supplier.
    *
    * @param name The part name. Must not be <jk>null</jk>.
    * @param valueSupplier Supplier for the value. Must not be <jk>null</jk>.
    * @return A new part. Never <jk>null</jk>.
    */
   public static HttpPart part(String name, Supplier<String> valueSupplier) {
      return HttpPartBean.of(name, valueSupplier);
   }

   /**
    * Creates a {@link PartList} from the given parts.
    *
    * @param parts The parts. Must not be <jk>null</jk>.
    * @return A new list. Never <jk>null</jk>.
    */
   public static PartList partList(HttpPart... parts) {
      return PartList.of(parts);
   }

   /**
    * Creates a {@link PartList} from alternating name/value string pairs.
    *
    * @param pairs Alternating name/value strings. Must not be <jk>null</jk>. Length must be even.
    * @return A new list. Never <jk>null</jk>.
    */
   public static PartList partListOfPairs(String... pairs) {
      return PartList.ofPairs(pairs);
   }

   private static final Function<ClassMeta<?>,ConstructorInfo> CONSTRUCTOR_FUNCTION =
      x -> x.getPublicConstructor(y -> y.hasParameterTypes(String.class))
         .orElseGet(() -> x.getPublicConstructor(y -> y.hasParameterTypes(String.class, String.class)).orElse(null));

   /**
    * Returns the {@code (String)} or {@code (String,String)} public constructor for the specified type.
    *
    * <p>
    * Used by part-parsing logic to instantiate typed parts from a wire string.
    *
    * @param type The type to find the constructor on. Must not be <jk>null</jk>.
    * @return The constructor wrapped in an {@link Optional}; empty if none is found.
    */
   public static Optional<ConstructorInfo> getConstructor(ClassMeta<?> type) {
      return type.getProperty("HttpPart.Constructor", CONSTRUCTOR_FUNCTION);
   }

   /**
    * Returns <jk>true</jk> if the specified type is a transport-neutral part type for the given
    * {@link HttpPartType}.
    *
    * <p>
    * The check is whether the type is assignable to {@link HttpHeader} (for {@code HEADER}) or
    * {@link HttpPart} (for {@code PATH}, {@code QUERY}, {@code FORMDATA}).
    *
    * @param partType The part type. Must not be <jk>null</jk>.
    * @param type The type to check. Must not be <jk>null</jk>.
    * @return <jk>true</jk> if the type is a part type for the given category.
    */
   public static boolean isHttpPart(HttpPartType partType, ClassMeta<?> type) {
      return switch (partType) {
         case PATH, QUERY, FORMDATA -> type.getProperty("HttpPart.isHttpPart", x -> x.isAssignableTo(HttpPart.class)).orElse(false);
         case HEADER -> type.getProperty("HttpPart.isHttpHeader", x -> x.isAssignableTo(HttpHeader.class)).orElse(false);
         default -> false;
      };
   }

   private static final Function<ClassMeta<?>,String> HEADER_NAME_FUNCTION = x -> {
      var n = Holder.<String>empty();
      x.forEachAnnotation(Header.class, y -> ine(y.value()), y -> n.set(y.value()));
      x.forEachAnnotation(Header.class, y -> ine(y.name()), y -> n.set(y.name()));
      if (n.isEmpty())
         n.set(readPublicStaticStringField(x.inner(), "NAME"));
      return n.orElse(null);
   };

   private static final Function<ClassMeta<?>,String> QUERY_NAME_FUNCTION = x -> {
      var n = Holder.<String>empty();
      x.forEachAnnotation(Query.class, y -> ine(y.value()), y -> n.set(y.value()));
      x.forEachAnnotation(Query.class, y -> ine(y.name()), y -> n.set(y.name()));
      if (n.isEmpty())
         n.set(readPublicStaticStringField(x.inner(), "NAME"));
      return n.orElse(null);
   };

   private static final Function<ClassMeta<?>,String> FORMDATA_NAME_FUNCTION = x -> {
      var n = Holder.<String>empty();
      x.forEachAnnotation(FormData.class, y -> ine(y.value()), y -> n.set(y.value()));
      x.forEachAnnotation(FormData.class, y -> ine(y.name()), y -> n.set(y.name()));
      if (n.isEmpty())
         n.set(readPublicStaticStringField(x.inner(), "NAME"));
      return n.orElse(null);
   };

   private static final Function<ClassMeta<?>,String> PATH_NAME_FUNCTION = x -> {
      var n = Holder.<String>empty();
      x.forEachAnnotation(Path.class, y -> ine(y.value()), y -> n.set(y.value()));
      x.forEachAnnotation(Path.class, y -> ine(y.name()), y -> n.set(y.name()));
      if (n.isEmpty())
         n.set(readPublicStaticStringField(x.inner(), "NAME"));
      return n.orElse(null);
   };

   private static String readPublicStaticStringField(Class<?> c, String fieldName) {
      try {
         var f = c.getField(fieldName);
         if (java.lang.reflect.Modifier.isStatic(f.getModifiers()) && f.getType() == String.class) {
            var v = f.get(null);
            return v == null ? null : v.toString();
         }
      } catch (@SuppressWarnings("unused") ReflectiveOperationException ignored) {
         // Field does not exist or is not accessible.
      }
      return null;
   }

   /**
    * Returns the name of the specified part type by reading the {@code @Header}, {@code @Query},
    * {@code @FormData}, or {@code @Path} annotation on the class.
    *
    * @param partType The part type. Must not be <jk>null</jk>.
    * @param type The type to check. Must not be <jk>null</jk>.
    * @return The part name, wrapped in an {@link Optional}.
    */
   public static Optional<String> getName(HttpPartType partType, ClassMeta<?> type) {
      return switch (partType) {
         case FORMDATA -> type.getProperty("HttpPart.formData.name", FORMDATA_NAME_FUNCTION);
         case HEADER -> type.getProperty("HttpPart.header.name", HEADER_NAME_FUNCTION);
         case PATH -> type.getProperty("HttpPart.path.name", PATH_NAME_FUNCTION);
         case QUERY -> type.getProperty("HttpPart.query.name", QUERY_NAME_FUNCTION);
         default -> oe();
      };
   }
}