/*
 * Copyright 2011 JBoss, by Red Hat, 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 org.jboss.errai.codegen.literal;

import static org.jboss.errai.codegen.builder.callstack.LoadClassReference.getClassReference;

import java.lang.annotation.Annotation;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.jboss.errai.codegen.AnnotationEncoder;
import org.jboss.errai.codegen.Context;
import org.jboss.errai.codegen.SnapshotMaker;
import org.jboss.errai.codegen.exception.NotLiteralizableException;
import org.jboss.errai.codegen.meta.MetaClass;
import org.jboss.errai.codegen.meta.MetaClassFactory;

/**
 * The literal factory provides a LiteralValue for the specified object (if possible).
 *
 * @author Mike Brock <cbrock@redhat.com>
 */
public class LiteralFactory {

  private static final Map<Object, LiteralValue<?>> LITERAL_CACHE = new HashMap<Object, LiteralValue<?>>();

  /**
   * Returns a literal value (specialization of Statement) representing the
   * given object in the given context.
   *
   * @param o
   *          The object to create a literal value for.
   * @return a LiteralValue for the given object. Never null.
   * @throws NotLiteralizableException if {@code o} cannot be literalized
   */
  public static LiteralValue<?> getLiteral(final Object o) {
    return getLiteral(null, o);
  }

  /**
   * Returns a literal value (specialization of Statement) representing the
   * given object in the given context.
   *
   * @param context
   *          The context the literal value will be code-generated in. Contexts
   *          can specify additional literalizable types. See {@link Context#addLiteralizableClass(Class)}.
   * @param o
   *          The object to create a literal value for.
   * @return a LiteralValue for the given object. Never null.
   * @throws NotLiteralizableException if {@code o} cannot be literalized
   */
  public static LiteralValue<?> getLiteral(final Context context, final Object o) {
    return getLiteral(context, o, true);
  }

  /**
   * Implementation for the public getLiteral() methods.
   *
   * @param context
   *          The context the literal value will be code-generated in. Contexts
   *          can specify additional literalizable types.
   * @param o
   *          The object to create a literal value for.
   * @return a LiteralValue for the given object. Never null.
   * @throws NotLiteralizableException if {@code o} cannot be literalized
   */
  private static LiteralValue<?> getLiteral(final Context context,
                                            final Object o,
                                            final boolean throwIfNotLiteralizable) {

    LiteralValue<?> result = LITERAL_CACHE.get(o);
    if (result == null) {

      if (o instanceof MetaClass) {
        result = new MetaClassLiteral((MetaClass)o);
      }
      else if (o instanceof Annotation) {
        result = new LiteralValue<Annotation>((Annotation) o) {
          @Override
          public String getCanonicalString(final Context context) {
            return AnnotationEncoder.encode((Annotation) o).generate(context);
          }
        };
      }
      else if (o instanceof Enum) {
        result = new LiteralValue<Enum>((Enum) o) {
          @Override
          public String getCanonicalString(final Context context) {
            return getClassReference(MetaClassFactory.get(o.getClass()), context) + "." + ((Enum) o).name();
          }
        };
      }
      else {
        result = _getLiteral(context, o, throwIfNotLiteralizable);
      }

      if (result != null) {
        // avoid caching the null; we don't want that returned from the cache!
        LITERAL_CACHE.put(o, result);
      }
    }

    return result;
  }

  private static LiteralValue<?> _getLiteral(final Context context,
                                             final Object o,
                                             final boolean throwIfNotLiteralizable) {

    if (o == null) {
      return NullLiteral.INSTANCE;
    }

    if (o instanceof String) {
      return new StringLiteral((String) o);
    }
    else if (o instanceof Integer) {
      return new IntValue((Integer) o);
    }
    else if (o instanceof Character) {
      return new CharValue((Character) o);
    }
    else if (o instanceof Boolean) {
      return new BooleanValue((Boolean) o);
    }
    else if (o instanceof Short) {
      return new ShortValue((Short) o);
    }
    else if (o instanceof Long) {
      return new LongValue((Long) o);
    }
    else if (o instanceof Double) {
      return new DoubleValue((Double) o);
    }
    else if (o instanceof Float) {
      return new FloatValue((Float) o);
    }
    else if (o instanceof Byte) {
      return new ByteValue((Byte) o);
    }
    else if (o instanceof Class) {
      return new ClassLiteral((Class) o);
    }
    else if (o instanceof MetaClass) {
      return new MetaClassLiteral((MetaClass) o);
    }
    else if (o instanceof Set) {
      return new SetValue((Set) o);
    }
    else if (o instanceof List) {
      return new ListValue((List) o);
    }
    else if (o instanceof Map) {
      return new MapValue((Map) o);
    }
    else if (o.getClass().isArray()) {
      return new ArrayLiteral(o);
    }
    else if (context != null && context.isLiteralizableClass(o.getClass())) {
      // the new instance of LiteralValue here provides surprising (but desirable) caching behaviour.
      // see LiteralTest.testGenerateObjectArrayThenModifyThenGenerateAgain for details.
      return new LiteralValue<Object>(o) {
        @Override
        public String getCanonicalString(final Context context) {
          final Class<?> targetType = context.getLiteralizableTargetType(o.getClass());
          return SnapshotMaker.makeSnapshotAsSubclass(o, targetType, targetType, null).generate(context);
        }
      };
    }
    else {
      if (throwIfNotLiteralizable) {
        throw new NotLiteralizableException(o);
      }
      return null;
    }
  }

  /**
   * Returns a literal value (specialization of Statement) representing the
   * given object in the given context, or null if the value is not
   * literalizable.
   *
   * @param o
   *          The object to create a literal value for.
   * @return a LiteralValue for the given object, or null if the value cannot be
   *         expressed as a literal.
   */
  public static LiteralValue<?> isLiteral(final Object o) {
    return getLiteral(null, o, false);
  }
  
  public static void emptyCache() {
    LITERAL_CACHE.clear();
  }
}