/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.mdsal.binding.yang.types;

import static java.util.Objects.requireNonNull;
import static org.opendaylight.mdsal.binding.model.ri.BindingTypes.TYPE_OBJECT;

import com.google.common.base.CharMatcher;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.TreeMap;
import org.opendaylight.mdsal.binding.generator.BindingGeneratorUtil;
import org.opendaylight.mdsal.binding.generator.impl.reactor.SerialVersionHelper;
import org.opendaylight.mdsal.binding.model.api.AccessModifier;
import org.opendaylight.mdsal.binding.model.api.ConcreteType;
import org.opendaylight.mdsal.binding.model.api.Enumeration;
import org.opendaylight.mdsal.binding.model.api.GeneratedTransferObject;
import org.opendaylight.mdsal.binding.model.api.GeneratedType;
import org.opendaylight.mdsal.binding.model.api.JavaTypeName;
import org.opendaylight.mdsal.binding.model.api.Restrictions;
import org.opendaylight.mdsal.binding.model.api.Type;
import org.opendaylight.mdsal.binding.model.api.type.builder.EnumBuilder;
import org.opendaylight.mdsal.binding.model.api.type.builder.GeneratedPropertyBuilder;
import org.opendaylight.mdsal.binding.model.api.type.builder.GeneratedTOBuilder;
import org.opendaylight.mdsal.binding.model.api.type.builder.GeneratedTypeBuilder;
import org.opendaylight.mdsal.binding.model.api.type.builder.GeneratedTypeBuilderBase;
import org.opendaylight.mdsal.binding.model.api.type.builder.MethodSignatureBuilder;
import org.opendaylight.mdsal.binding.model.ri.BaseYangTypes;
import org.opendaylight.mdsal.binding.model.ri.BindingTypes;
import org.opendaylight.mdsal.binding.model.ri.TypeConstants;
import org.opendaylight.mdsal.binding.model.ri.Types;
import org.opendaylight.mdsal.binding.model.ri.generated.type.builder.AbstractEnumerationBuilder;
import org.opendaylight.mdsal.binding.model.ri.generated.type.builder.GeneratedPropertyBuilderImpl;
import org.opendaylight.mdsal.binding.spec.naming.BindingMapping;
import org.opendaylight.yangtools.yang.common.QName;
import org.opendaylight.yangtools.yang.common.Revision;
import org.opendaylight.yangtools.yang.model.api.EffectiveModelContext;
import org.opendaylight.yangtools.yang.model.api.Module;
import org.opendaylight.yangtools.yang.model.api.SchemaContext;
import org.opendaylight.yangtools.yang.model.api.SchemaNode;
import org.opendaylight.yangtools.yang.model.api.SchemaPath;
import org.opendaylight.yangtools.yang.model.api.Status;
import org.opendaylight.yangtools.yang.model.api.TypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.BitsTypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.BitsTypeDefinition.Bit;
import org.opendaylight.yangtools.yang.model.api.type.EnumTypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.IdentityrefTypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.LeafrefTypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.PatternConstraint;
import org.opendaylight.yangtools.yang.model.api.type.StringTypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.UnionTypeDefinition;
import org.opendaylight.yangtools.yang.model.spi.ModuleDependencySort;

// FIXME: remove this class
@Deprecated(forRemoval = true)
abstract class AbstractTypeProvider implements TypeProvider {
    private static final JavaTypeName DEPRECATED_ANNOTATION = JavaTypeName.create(Deprecated.class);
    private static final CharMatcher DASH_COLON_MATCHER = CharMatcher.anyOf("-:");

    /**
     * Contains the schema data red from YANG files.
     */
    private final SchemaContext schemaContext;

    private final Map<String, Map<Optional<Revision>, Map<String, GeneratedType>>> genTypeDefsContextMap =
        new HashMap<>();

    /**
     * The map which maps schema paths to JAVA <code>Type</code>.
     */
    private final Map<SchemaPath, Type> referencedTypes = new HashMap<>();
    private final Map<Module, Set<GeneratedType>> additionalTypes = new HashMap<>();

    /**
     * Creates new instance of class <code>TypeProviderImpl</code>.
     *
     * @param schemaContext contains the schema data red from YANG files
     * @param renames renaming table
     * @throws IllegalArgumentException if <code>schemaContext</code> equal null.
     */
    AbstractTypeProvider(final EffectiveModelContext schemaContext) {
        this.schemaContext = requireNonNull(schemaContext);

        resolveTypeDefsFromContext();
    }

    /**
     * Puts <code>refType</code> to map with key <code>refTypePath</code>.
     *
     * @param refTypePath schema path used as the map key
     * @param refType type which represents the map value
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>refTypePath</code> equal null</li>
     *             <li>if <code>refType</code> equal null</li>
     *             </ul>
     *
     */
    public void putReferencedType(final SchemaPath refTypePath, final Type refType) {
        Preconditions.checkArgument(refTypePath != null,
                "Path reference of Enumeration Type Definition cannot be NULL!");
        Preconditions.checkArgument(refType != null, "Reference to Enumeration Type cannot be NULL!");
        referencedTypes.put(refTypePath, refType);
    }

    public Map<Module, Set<GeneratedType>> getAdditionalTypes() {
        return additionalTypes;
    }

    @Override
    public Type javaTypeForSchemaDefinitionType(final TypeDefinition<?> typeDefinition, final SchemaNode parentNode,
            final boolean lenientRelativeLeafrefs) {
        return javaTypeForSchemaDefinitionType(typeDefinition, parentNode, null, lenientRelativeLeafrefs);
    }

    /**
     * Converts schema definition type <code>typeDefinition</code> to JAVA <code>Type</code>.
     *
     * @param typeDefinition type definition which is converted to JAVA type
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>typeDefinition</code> equal null</li>
     *             <li>if Qname of <code>typeDefinition</code> equal null</li>
     *             <li>if name of <code>typeDefinition</code> equal null</li>
     *             </ul>
     */
    @Override
    public Type javaTypeForSchemaDefinitionType(final TypeDefinition<?> typeDefinition, final SchemaNode parentNode,
            final Restrictions restrictions, final boolean lenientRelativeLeafrefs) {
        throw new UnsupportedOperationException();
    }

    /**
     * Converts <code>typeDefinition</code> to concrete JAVA <code>Type</code>.
     *
     * @param typeDefinition
     *            type definition which should be converted to JAVA
     *            <code>Type</code>
     * @return JAVA <code>Type</code> which represents
     *         <code>typeDefinition</code>
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>typeDefinition</code> equal null</li>
     *             <li>if Q name of <code>typeDefinition</code></li>
     *             <li>if name of <code>typeDefinition</code></li>
     *             </ul>
     */
    public GeneratedType generatedTypeForExtendedDefinitionType(final TypeDefinition<?> typeDefinition,
            final SchemaNode parentNode) {
        Preconditions.checkArgument(typeDefinition != null, "Type Definition cannot be NULL!");
        if (typeDefinition.getQName() == null) {
            throw new IllegalArgumentException("Type Definition cannot have unspecified QName (QName cannot be NULL!)");
        }
        Preconditions.checkArgument(typeDefinition.getQName().getLocalName() != null,
                "Type Definitions Local Name cannot be NULL!");

        final TypeDefinition<?> baseTypeDef = baseTypeDefForExtendedType(typeDefinition);
        if (baseTypeDef instanceof LeafrefTypeDefinition || baseTypeDef instanceof IdentityrefTypeDefinition) {
            /*
             * This is backwards compatibility baggage from way back when. The problem at hand is inconsistency between
             * the fact that identity is mapped to a Class, which is also returned from leaves which specify it like
             * this:
             *
             *     identity iden;
             *
             *     container foo {
             *         leaf foo {
             *             type identityref {
             *                 base iden;
             *             }
             *         }
             *     }
             *
             * This results in getFoo() returning Class<? extends Iden>, which looks fine on the surface, but gets more
             * dicey when we throw in:
             *
             *     typedef bar-ref {
             *         type identityref {
             *             base iden;
             *         }
             *     }
             *
             *     container bar {
             *         leaf bar {
             *             type bar-ref;
             *         }
             *     }
             *
             * Now we have competing requirements: typedef would like us to use encapsulation to capture the defined
             * type, while getBar() wants us to retain shape with getFoo(), as it should not matter how the identityref
             * is formed.
             *
             * In this particular case getFoo() won just after the Binding Spec was frozen, hence we do not generate
             * an encapsulation for identityref typedefs.
             *
             * In case you are thinking we could get by having foo-ref map to a subclass of Iden, that is not a good
             * option, as it would look as though it is the product of a different construct:
             *
             *     identity bar-ref {
             *         base iden;
             *     }
             *
             * Leading to a rather nice namespace clash and also slight incompatibility with unknown third-party
             * sub-identities of iden.
             *
             * The story behind leafrefs is probably similar, but that needs to be ascertained.
             */
            return null;
        }

        final Module module = findParentModule(schemaContext, parentNode);
        if (module != null) {
            final Map<Optional<Revision>, Map<String, GeneratedType>> modulesByDate = genTypeDefsContextMap.get(
                module.getName());
            final Map<String, GeneratedType> genTOs = modulesByDate.get(module.getRevision());
            if (genTOs != null) {
                return genTOs.get(typeDefinition.getQName().getLocalName());
            }
        }
        return null;
    }

    /**
     * Gets base type definition for <code>extendTypeDef</code>. The method is
     * recursively called until non <code>ExtendedType</code> type is found.
     *
     * @param extendTypeDef
     *            type definition for which is the base type definition sought
     * @return type definition which is base type for <code>extendTypeDef</code>
     * @throws IllegalArgumentException
     *             if <code>extendTypeDef</code> equal null
     */
    private static TypeDefinition<?> baseTypeDefForExtendedType(final TypeDefinition<?> extendTypeDef) {
        Preconditions.checkArgument(extendTypeDef != null, "Type Definition reference cannot be NULL!");

        TypeDefinition<?> ret = extendTypeDef;
        while (ret.getBaseType() != null) {
            ret = ret.getBaseType();
        }

        return ret;
    }

    /**
     * Converts <code>enumTypeDef</code> to {@link Enumeration enumeration}.
     *
     * @param enumTypeDef enumeration type definition which is converted to enumeration
     * @param enumName string with name which is used as the enumeration name
     * @return enumeration type which is built with data (name, enum values) from <code>enumTypeDef</code>
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>enumTypeDef</code> equals null</li>
     *             <li>if enum values of <code>enumTypeDef</code> equal null</li>
     *             <li>if Q name of <code>enumTypeDef</code> equal null</li>
     *             <li>if name of <code>enumTypeDef</code> equal null</li>
     *             </ul>
     */
    private Enumeration provideTypeForEnum(final EnumTypeDefinition enumTypeDef, final String enumName,
            final SchemaNode parentNode) {
        Preconditions.checkArgument(enumTypeDef != null, "EnumTypeDefinition reference cannot be NULL!");
        Preconditions.checkArgument(enumTypeDef.getValues() != null,
                "EnumTypeDefinition MUST contain at least ONE value definition!");
        Preconditions.checkArgument(enumTypeDef.getQName() != null, "EnumTypeDefinition MUST contain NON-NULL QName!");
        Preconditions.checkArgument(enumTypeDef.getQName().getLocalName() != null,
                "Local Name in EnumTypeDefinition QName cannot be NULL!");

        final Module module = findParentModule(schemaContext, parentNode);
        final AbstractEnumerationBuilder enumBuilder = newEnumerationBuilder(JavaTypeName.create(
            BindingMapping.getRootPackageName(module.getQNameModule()), BindingMapping.getClassName(enumName)));
        addEnumDescription(enumBuilder, enumTypeDef);
        enumTypeDef.getReference().ifPresent(enumBuilder::setReference);
        enumBuilder.setModuleName(module.getName());
        enumBuilder.updateEnumPairsFromEnumTypeDef(enumTypeDef);
        return enumBuilder.toInstance();
    }

    /**
     * Adds enumeration to <code>typeBuilder</code>. The enumeration data are taken from <code>enumTypeDef</code>.
     *
     * @param enumTypeDef enumeration type definition is source of enumeration data for <code>typeBuilder</code>
     * @param enumName string with the name of enumeration
     * @param typeBuilder generated type builder to which is enumeration added
     * @return enumeration type which contains enumeration data form <code>enumTypeDef</code>
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>enumTypeDef</code> equals null</li>
     *             <li>if enum values of <code>enumTypeDef</code> equal null</li>
     *             <li>if Q name of <code>enumTypeDef</code> equal null</li>
     *             <li>if name of <code>enumTypeDef</code> equal null</li>
     *             <li>if name of <code>typeBuilder</code> equal null</li>
     *             </ul>
     *
     */
    private Enumeration addInnerEnumerationToTypeBuilder(final EnumTypeDefinition enumTypeDef,
            final String enumName, final GeneratedTypeBuilderBase<?> typeBuilder) {
        Preconditions.checkArgument(enumTypeDef != null, "EnumTypeDefinition reference cannot be NULL!");
        Preconditions.checkArgument(enumTypeDef.getValues() != null,
                "EnumTypeDefinition MUST contain at least ONE value definition!");
        Preconditions.checkArgument(enumTypeDef.getQName() != null, "EnumTypeDefinition MUST contain NON-NULL QName!");
        Preconditions.checkArgument(enumTypeDef.getQName().getLocalName() != null,
                "Local Name in EnumTypeDefinition QName cannot be NULL!");
        Preconditions.checkArgument(typeBuilder != null, "Generated Type Builder reference cannot be NULL!");

        final EnumBuilder enumBuilder = newEnumerationBuilder(
            typeBuilder.getIdentifier().createEnclosed(BindingMapping.getClassName(enumName), "$"));
        addEnumDescription(enumBuilder, enumTypeDef);
        enumBuilder.updateEnumPairsFromEnumTypeDef(enumTypeDef);
        final Enumeration ret = enumBuilder.toInstance();
        typeBuilder.addEnumeration(ret);

        return ret;
    }

    public abstract void addEnumDescription(EnumBuilder enumBuilder, EnumTypeDefinition enumTypeDef);

    public abstract AbstractEnumerationBuilder newEnumerationBuilder(JavaTypeName identifier);

    public abstract GeneratedTOBuilder newGeneratedTOBuilder(JavaTypeName identifier);

    public abstract GeneratedTypeBuilder newGeneratedTypeBuilder(JavaTypeName identifier);

    /**
     * Converts the pattern constraints to the list of the strings which represents these constraints.
     *
     * @param patternConstraints list of pattern constraints
     * @return list of strings which represents the constraint patterns
     */
    public abstract Map<String, String> resolveRegExpressions(List<PatternConstraint> patternConstraints);

    abstract void addCodegenInformation(GeneratedTypeBuilderBase<?> genTOBuilder, TypeDefinition<?> typeDef);

    /**
     * Converts the pattern constraints from <code>typedef</code> to the list of the strings which represents these
     * constraints.
     *
     * @param typedef extended type in which are the pattern constraints sought
     * @return list of strings which represents the constraint patterns
     * @throws IllegalArgumentException if <code>typedef</code> equals null
     *
     */
    private Map<String, String> resolveRegExpressionsFromTypedef(final TypeDefinition<?> typedef) {
        if (!(typedef instanceof StringTypeDefinition)) {
            return ImmutableMap.of();
        }

        // TODO: run diff against base ?
        return resolveRegExpressions(((StringTypeDefinition) typedef).getPatternConstraints());
    }

    /**
     * Passes through all modules and through all its type definitions and convert it to generated types.
     *
     * <p>
     * The modules are first sorted by mutual dependencies. The modules are sequentially passed. All type definitions
     * of a module are at the beginning sorted so that type definition with less amount of references to other type
     * definition are processed first.<br>
     * For each module is created mapping record in the map
     * {@link AbstractTypeProvider#genTypeDefsContextMap genTypeDefsContextMap}
     * which map current module name to the map which maps type names to returned types (generated types).
     */
    private void resolveTypeDefsFromContext() {
        final List<Module> modulesSortedByDependency = ModuleDependencySort.sort(schemaContext.getModules());

        for (Module module : modulesSortedByDependency) {
            Map<Optional<Revision>, Map<String, GeneratedType>> dateTypeMap = genTypeDefsContextMap.computeIfAbsent(
                module.getName(), key -> new HashMap<>());
            dateTypeMap.put(module.getRevision(), Collections.emptyMap());
            genTypeDefsContextMap.put(module.getName(), dateTypeMap);
        }

        for (Module module : modulesSortedByDependency) {
            if (module != null) {
                final String basePackageName = BindingMapping.getRootPackageName(module.getQNameModule());
                if (basePackageName != null) {
                    final List<TypeDefinition<?>> typeDefinitions = TypedefResolver.getAllTypedefs(module);
                    for (TypeDefinition<?> typedef : sortTypeDefinitionAccordingDepth(typeDefinitions)) {
                        typedefToGeneratedType(basePackageName, module, typedef);
                    }
                }
            }
        }
    }

    /**
     * Create Type for specified type definition.
     *
     * @param basePackageName string with name of package to which the module belongs
     * @param module string with the name of the module for to which the <code>typedef</code> belongs
     * @param typedef type definition of the node for which should be created JAVA <code>Type</code>
     *                (usually generated TO)
     * @return JAVA <code>Type</code> representation of <code>typedef</code> or
     *         <code>null</code> value if <code>basePackageName</code> or
     *         <code>modulName</code> or <code>typedef</code> or Q name of
     *         <code>typedef</code> equals <code>null</code>
     */
    private Type typedefToGeneratedType(final String basePackageName, final Module module,
            final TypeDefinition<?> typedef) {
        final TypeDefinition<?> baseTypedef = typedef.getBaseType();

        // See generatedTypeForExtendedDefinitionType() above for rationale behind this special case.
        if (baseTypedef instanceof LeafrefTypeDefinition || baseTypedef instanceof IdentityrefTypeDefinition) {
            return null;
        }

        final String typedefName = typedef.getQName().getLocalName();

        final GeneratedType returnType;
        if (baseTypedef.getBaseType() != null) {
            returnType = provideGeneratedTOFromExtendedType(typedef, baseTypedef, basePackageName,
                module.getName());
        } else if (baseTypedef instanceof UnionTypeDefinition) {
            final GeneratedTOBuilder genTOBuilder = provideGeneratedTOBuilderForUnionTypeDef(
                JavaTypeName.create(basePackageName, BindingMapping.getClassName(typedef.getQName())),
                (UnionTypeDefinition) baseTypedef, typedef);
            genTOBuilder.setTypedef(true);
            genTOBuilder.setIsUnion(true);
            addUnitsToGenTO(genTOBuilder, typedef.getUnits().orElse(null));
            makeSerializable(genTOBuilder);
            returnType = genTOBuilder.build();

            // Define a corresponding union builder. Typedefs are always anchored at a Java package root,
            // so we are placing the builder alongside the union.
            final GeneratedTOBuilder unionBuilder = newGeneratedTOBuilder(
                JavaTypeName.create(genTOBuilder.getPackageName(), genTOBuilder.getName() + "Builder"));
            unionBuilder.setIsUnionBuilder(true);
            final MethodSignatureBuilder method = unionBuilder.addMethod("getDefaultInstance");
            method.setReturnType(returnType);
            method.addParameter(Types.STRING, "defaultValue");
            method.setAccessModifier(AccessModifier.PUBLIC);
            method.setStatic(true);
            additionalTypes.computeIfAbsent(module, key -> new HashSet<>()).add(unionBuilder.build());
        } else if (baseTypedef instanceof EnumTypeDefinition) {
            // enums are automatically Serializable
            final EnumTypeDefinition enumTypeDef = (EnumTypeDefinition) baseTypedef;
            // TODO units for typedef enum
            returnType = provideTypeForEnum(enumTypeDef, typedefName, typedef);
        } else if (baseTypedef instanceof BitsTypeDefinition) {
            final GeneratedTOBuilder genTOBuilder = provideGeneratedTOBuilderForBitsTypeDefinition(
                JavaTypeName.create(basePackageName, BindingMapping.getClassName(typedef.getQName())),
                (BitsTypeDefinition) baseTypedef, module.getName());
            genTOBuilder.setTypedef(true);
            addUnitsToGenTO(genTOBuilder, typedef.getUnits().orElse(null));
            makeSerializable(genTOBuilder);
            returnType = genTOBuilder.build();
        } else {
            final Type javaType = javaTypeForSchemaDefinitionType(baseTypedef, typedef);
            returnType = wrapJavaTypeIntoTO(basePackageName, typedef, javaType, module.getName());
        }
        if (returnType != null) {
            final Map<Optional<Revision>, Map<String, GeneratedType>> modulesByDate =
                    genTypeDefsContextMap.get(module.getName());
            final Optional<Revision> moduleRevision = module.getRevision();
            Map<String, GeneratedType> typeMap = modulesByDate.get(moduleRevision);
            if (typeMap != null) {
                if (typeMap.isEmpty()) {
                    typeMap = new HashMap<>(4);
                    modulesByDate.put(moduleRevision, typeMap);
                }
                typeMap.put(typedefName, returnType);
            }
            return returnType;
        }
        return null;
    }

    /**
     * Wraps base YANG type to generated TO.
     *
     * @param basePackageName string with name of package to which the module belongs
     * @param typedef type definition which is converted to the TO
     * @param javaType JAVA <code>Type</code> to which is <code>typedef</code> mapped
     * @return generated transfer object which represent<code>javaType</code>
     */
    private GeneratedTransferObject wrapJavaTypeIntoTO(final String basePackageName, final TypeDefinition<?> typedef,
            final Type javaType, final String moduleName) {
        requireNonNull(javaType, "javaType cannot be null");

        final GeneratedTOBuilder genTOBuilder = typedefToTransferObject(basePackageName, typedef, moduleName);
        genTOBuilder.setRestrictions(BindingGeneratorUtil.getRestrictions(typedef));
        final GeneratedPropertyBuilder genPropBuilder = genTOBuilder.addProperty(TypeConstants.VALUE_PROP);
        genPropBuilder.setReturnType(javaType);

        genTOBuilder.addEqualsIdentity(genPropBuilder);
        genTOBuilder.addHashIdentity(genPropBuilder);
        genTOBuilder.addToStringProperty(genPropBuilder);
        genTOBuilder.addImplementsType(BindingTypes.scalarTypeObject(javaType));
        if (typedef.getStatus() == Status.DEPRECATED) {
            genTOBuilder.addAnnotation(DEPRECATED_ANNOTATION);
        }
        if (javaType instanceof ConcreteType && "String".equals(javaType.getName()) && typedef.getBaseType() != null) {
            addStringRegExAsConstant(genTOBuilder, resolveRegExpressionsFromTypedef(typedef));
        }
        addUnitsToGenTO(genTOBuilder, typedef.getUnits().orElse(null));
        genTOBuilder.setTypedef(true);
        makeSerializable(genTOBuilder);
        return genTOBuilder.build();
    }

    /**
     * Converts output list of generated TO builders to one TO builder (first
     * from list) which contains the remaining builders as its enclosing TO.
     *
     * @param typeName new type identifier
     * @param typedef type definition which should be of type {@link UnionTypeDefinition}
     * @return generated TO builder with the list of enclosed generated TO builders
     */
    public GeneratedTOBuilder provideGeneratedTOBuilderForUnionTypeDef(final JavaTypeName typeName,
            final UnionTypeDefinition typedef, final TypeDefinition<?> parentNode) {
        final List<GeneratedTOBuilder> builders = provideGeneratedTOBuildersForUnionTypeDef(typeName, typedef,
            parentNode);
        Preconditions.checkState(!builders.isEmpty(), "No GeneratedTOBuilder objects generated from union %s", typedef);

        final GeneratedTOBuilder resultTOBuilder = builders.remove(0);
        builders.forEach(builder -> resultTOBuilder.addEnclosingTransferObject(builder.build()));
        return resultTOBuilder;
    }

    /**
     * Converts <code>typedef</code> to generated TO with <code>typeDefName</code>. Every union type from
     * <code>typedef</code> is added to generated TO builder as property.
     *
     * @param typeName new type identifier
     * @param typedef type definition which should be of type <code>UnionTypeDefinition</code>
     * @return generated TO builder which represents <code>typedef</code>
     * @throws NullPointerException
     *             <ul>
     *             <li>if <code>basePackageName</code> is null</li>
     *             <li>if <code>typedef</code> is null</li>
     *             <li>if Qname of <code>typedef</code> is null</li>
     *             </ul>
     */
    public List<GeneratedTOBuilder> provideGeneratedTOBuildersForUnionTypeDef(final JavaTypeName typeName,
            final UnionTypeDefinition typedef, final SchemaNode parentNode) {
        requireNonNull(typedef, "Type Definition cannot be NULL!");
        requireNonNull(typedef.getQName(), "Type definition QName cannot be NULL!");

        final List<GeneratedTOBuilder> generatedTOBuilders = new ArrayList<>();
        final List<TypeDefinition<?>> unionTypes = typedef.getTypes();
        final Module module = findParentModule(schemaContext, parentNode);

        final GeneratedTOBuilder unionGenTOBuilder = newGeneratedTOBuilder(typeName);
        unionGenTOBuilder.setIsUnion(true);
        unionGenTOBuilder.setSchemaPath(typedef.getPath());
        unionGenTOBuilder.setModuleName(module.getName());
        unionGenTOBuilder.addImplementsType(TYPE_OBJECT);
        addCodegenInformation(unionGenTOBuilder, typedef);
        generatedTOBuilders.add(unionGenTOBuilder);

        // Pattern string is the key, XSD regex is the value. The reason for this choice is that the pattern carries
        // also negation information and hence guarantees uniqueness.
        final Map<String, String> expressions = new HashMap<>();
        for (TypeDefinition<?> unionType : unionTypes) {
            final String unionTypeName = unionType.getQName().getLocalName();

            // If we have a base type we should follow the type definition backwards, except for identityrefs, as those
            // do not follow type encapsulation -- we use the general case for that.
            if (unionType.getBaseType() != null  && !(unionType instanceof IdentityrefTypeDefinition)) {
                resolveExtendedSubtypeAsUnion(unionGenTOBuilder, unionType, expressions, parentNode);
            } else if (unionType instanceof UnionTypeDefinition) {
                generatedTOBuilders.addAll(resolveUnionSubtypeAsUnion(unionGenTOBuilder,
                    (UnionTypeDefinition) unionType, parentNode));
            } else if (unionType instanceof EnumTypeDefinition) {
                final Enumeration enumeration = addInnerEnumerationToTypeBuilder((EnumTypeDefinition) unionType,
                        unionTypeName, unionGenTOBuilder);
                updateUnionTypeAsProperty(unionGenTOBuilder, enumeration, unionTypeName);
            } else {
                final Type javaType = javaTypeForSchemaDefinitionType(unionType, parentNode);
                updateUnionTypeAsProperty(unionGenTOBuilder, javaType, unionTypeName);
            }
        }
        addStringRegExAsConstant(unionGenTOBuilder, expressions);

        storeGenTO(typedef, unionGenTOBuilder, parentNode);

        return generatedTOBuilders;
    }

    /**
     * Wraps code which handles the case when union subtype is also of the type <code>UnionType</code>.
     *
     * <p>
     * In this case the new generated TO is created for union subtype (recursive call of method
     * {@link #provideGeneratedTOBuildersForUnionTypeDef(String, UnionTypeDefinition, String, SchemaNode)}
     * provideGeneratedTOBuilderForUnionTypeDef} and in parent TO builder <code>parentUnionGenTOBuilder</code> is
     * created property which type is equal to new generated TO.
     *
     * @param parentUnionGenTOBuilder generated TO builder to which is the property with the child union subtype added
     * @param basePackageName string with the name of the module package
     * @param unionSubtype type definition which represents union subtype
     * @return list of generated TO builders. The number of the builders can be bigger one due to recursive call of
     *         <code>provideGeneratedTOBuildersForUnionTypeDef</code> method.
     */
    private List<GeneratedTOBuilder> resolveUnionSubtypeAsUnion(final GeneratedTOBuilder parentUnionGenTOBuilder,
            final UnionTypeDefinition unionSubtype, final SchemaNode parentNode) {
        final JavaTypeName newTOBuilderName = parentUnionGenTOBuilder.getIdentifier().createSibling(
            provideAvailableNameForGenTOBuilder(parentUnionGenTOBuilder.getName()));
        final List<GeneratedTOBuilder> subUnionGenTOBUilders = provideGeneratedTOBuildersForUnionTypeDef(
            newTOBuilderName, unionSubtype, parentNode);

        final GeneratedPropertyBuilder propertyBuilder;
        propertyBuilder = parentUnionGenTOBuilder.addProperty(BindingMapping.getPropertyName(
            newTOBuilderName.simpleName()));
        propertyBuilder.setReturnType(subUnionGenTOBUilders.get(0).build());
        parentUnionGenTOBuilder.addEqualsIdentity(propertyBuilder);
        parentUnionGenTOBuilder.addToStringProperty(propertyBuilder);

        return subUnionGenTOBUilders;
    }

    /**
     * Wraps code which handle case when union subtype is of the type <code>ExtendedType</code>. If TO for this type
     * already exists it is used for the creation of the property in <code>parentUnionGenTOBuilder</code>. Otherwise
     * the base type is used for the property creation.
     *
     * @param parentUnionGenTOBuilder generated TO builder in which new property is created
     * @param unionSubtype type definition of the <code>ExtendedType</code> type which represents union subtype
     * @param expressions list of strings with the regular expressions
     * @param parentNode parent Schema Node for Extended Subtype
     */
    private void resolveExtendedSubtypeAsUnion(final GeneratedTOBuilder parentUnionGenTOBuilder,
            final TypeDefinition<?> unionSubtype, final Map<String, String> expressions, final SchemaNode parentNode) {
        final String unionTypeName = unionSubtype.getQName().getLocalName();
        final Type genTO = findGenTO(unionTypeName, unionSubtype);
        if (genTO != null) {
            updateUnionTypeAsProperty(parentUnionGenTOBuilder, genTO, genTO.getName());
            return;
        }

        final TypeDefinition<?> baseType = baseTypeDefForExtendedType(unionSubtype);
        if (unionTypeName.equals(baseType.getQName().getLocalName())) {
            final Type javaType = BaseYangTypesProvider.INSTANCE.javaTypeForSchemaDefinitionType(baseType, parentNode,
                BindingGeneratorUtil.getRestrictions(unionSubtype));
            if (javaType != null) {
                updateUnionTypeAsProperty(parentUnionGenTOBuilder, javaType, unionTypeName);
            }
        } else if (baseType instanceof LeafrefTypeDefinition) {
            final Type javaType = javaTypeForSchemaDefinitionType(baseType, parentNode);
            boolean typeExist = false;
            for (GeneratedPropertyBuilder generatedPropertyBuilder : parentUnionGenTOBuilder.getProperties()) {
                final Type origType = ((GeneratedPropertyBuilderImpl) generatedPropertyBuilder).getReturnType();
                if (origType != null && javaType != null && javaType == origType) {
                    typeExist = true;
                    break;
                }
            }
            if (!typeExist && javaType != null) {
                updateUnionTypeAsProperty(parentUnionGenTOBuilder, javaType,
                    BindingMapping.getUnionLeafrefMemberName(parentUnionGenTOBuilder.getName(), javaType.getName()));
            }
        }
        if (baseType instanceof StringTypeDefinition) {
            expressions.putAll(resolveRegExpressionsFromTypedef(unionSubtype));
        }
    }

    /**
     * Searches for generated TO for <code>searchedTypeDef</code> type  definition
     * in {@link #genTypeDefsContextMap genTypeDefsContextMap}.
     *
     * @param searchedTypeName string with name of <code>searchedTypeDef</code>
     * @return generated TO for <code>searchedTypeDef</code> or <code>null</code> it it doesn't exist
     */
    private Type findGenTO(final String searchedTypeName, final SchemaNode parentNode) {
        final Module typeModule = findParentModule(schemaContext, parentNode);
        if (typeModule != null && typeModule.getName() != null) {
            final Map<Optional<Revision>, Map<String, GeneratedType>> modulesByDate = genTypeDefsContextMap.get(
                typeModule.getName());
            final Map<String, GeneratedType> genTOs = modulesByDate.get(typeModule.getRevision());
            if (genTOs != null) {
                return genTOs.get(searchedTypeName);
            }
        }
        return null;
    }

    /**
     * Stores generated TO created from <code>genTOBuilder</code> for <code>newTypeDef</code>
     * to {@link #genTypeDefsContextMap genTypeDefsContextMap} if the module for <code>newTypeDef</code> exists.
     *
     * @param newTypeDef type definition for which is <code>genTOBuilder</code> created
     * @param genTOBuilder generated TO builder which is converted to generated TO and stored
     */
    private void storeGenTO(final TypeDefinition<?> newTypeDef, final GeneratedTOBuilder genTOBuilder,
            final SchemaNode parentNode) {
        if (!(newTypeDef instanceof UnionTypeDefinition)) {
            final Module parentModule = findParentModule(schemaContext, parentNode);
            if (parentModule != null && parentModule.getName() != null) {
                final Map<Optional<Revision>, Map<String, GeneratedType>> modulesByDate = genTypeDefsContextMap.get(
                    parentModule.getName());
                final Map<String, GeneratedType> genTOsMap = modulesByDate.get(parentModule.getRevision());
                genTOsMap.put(newTypeDef.getQName().getLocalName(), genTOBuilder.build());
            }
        }
    }

    /**
     * Adds a new property with the name <code>propertyName</code> and with type <code>type</code>
     * to <code>unonGenTransObject</code>.
     *
     * @param unionGenTransObject generated TO to which should be property added
     * @param type JAVA <code>type</code> of the property which should be added to <code>unionGentransObject</code>
     * @param propertyName string with name of property which should be added to <code>unionGentransObject</code>
     */
    private static void updateUnionTypeAsProperty(final GeneratedTOBuilder unionGenTransObject, final Type type,
            final String propertyName) {
        if (unionGenTransObject != null && type != null && !unionGenTransObject.containsProperty(propertyName)) {
            final GeneratedPropertyBuilder propBuilder = unionGenTransObject
                    .addProperty(BindingMapping.getPropertyName(propertyName));
            propBuilder.setReturnType(type);

            unionGenTransObject.addEqualsIdentity(propBuilder);
            unionGenTransObject.addHashIdentity(propBuilder);
            unionGenTransObject.addToStringProperty(propBuilder);
        }
    }

    /**
     * Converts <code>typedef</code> to the generated TO builder.
     *
     * @param basePackageName string with name of package to which the module belongs
     * @param typedef type definition from which is the generated TO builder created
     * @return generated TO builder which contains data from <code>typedef</code> and <code>basePackageName</code>
     */
    private GeneratedTOBuilder typedefToTransferObject(final String basePackageName,
            final TypeDefinition<?> typedef, final String moduleName) {
        final JavaTypeName name = JavaTypeName.create(
                packageNameForGeneratedType(basePackageName, typedef.getPath()),
                BindingMapping.getClassName(typedef.getQName().getLocalName()));

        final GeneratedTOBuilder newType = newGeneratedTOBuilder(name);
        newType.setSchemaPath(typedef.getPath());
        newType.setModuleName(moduleName);
        addCodegenInformation(newType, typedef);
        return newType;
    }

    /**
     * Creates package name from specified <code>basePackageName</code> (package name for module)
     * and <code>schemaPath</code>. Resulting package name is concatenation of <code>basePackageName</code>
     * and all local names of YANG nodes which are parents of some node for which <code>schemaPath</code> is specified.
     *
     * @param basePackageName string with package name of the module, MUST be normalized, otherwise this method may
     *                        return an invalid string.
     * @param schemaPath list of names of YANG nodes which are parents of some node + name of this node
     * @return string with valid JAVA package name
     * @throws NullPointerException if any of the arguments are null
     */
    private static String packageNameForGeneratedType(final String basePackageName, final SchemaPath schemaPath) {
        final int size = Iterables.size(schemaPath.getPathTowardsRoot()) - 1;
        if (size <= 0) {
            return basePackageName;
        }

        return generateNormalizedPackageName(basePackageName, schemaPath.getPathFromRoot(), size);
    }

    private static String generateNormalizedPackageName(final String base, final Iterable<QName> path, final int size) {
        final StringBuilder builder = new StringBuilder(base);
        final Iterator<QName> iterator = path.iterator();
        for (int i = 0; i < size; ++i) {
            builder.append('.');
            final String nodeLocalName = iterator.next().getLocalName();
            // FIXME: Collon ":" is invalid in node local name as per RFC6020, identifier statement.
            builder.append(DASH_COLON_MATCHER.replaceFrom(nodeLocalName, '.'));
        }
        return BindingMapping.normalizePackageName(builder.toString());
    }


    /**
     * Converts <code>typeDef</code> which should be of the type <code>BitsTypeDefinition</code>
     * to <code>GeneratedTOBuilder</code>. All the bits of the typeDef are added to returning generated TO as
     * properties.
     *
     * @param typeName new type identifier
     * @param typeDef type definition from which is the generated TO builder created
     * @return generated TO builder which represents <code>typeDef</code>
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>typeDef</code> equals null</li>
     *             <li>if <code>basePackageName</code> equals null</li>
     *             </ul>
     */
    public GeneratedTOBuilder provideGeneratedTOBuilderForBitsTypeDefinition(final JavaTypeName typeName,
            final BitsTypeDefinition typeDef, final String moduleName) {
        final GeneratedTOBuilder genTOBuilder = newGeneratedTOBuilder(typeName);
        genTOBuilder.setSchemaPath(typeDef.getPath());
        genTOBuilder.setModuleName(moduleName);
        genTOBuilder.setBaseType(typeDef);
        genTOBuilder.addImplementsType(TYPE_OBJECT);
        addCodegenInformation(genTOBuilder, typeDef);

        for (Bit bit : typeDef.getBits()) {
            final String name = bit.getName();
            GeneratedPropertyBuilder genPropertyBuilder = genTOBuilder.addProperty(
                BindingMapping.getPropertyName(name));
            genPropertyBuilder.setReadOnly(true);
            genPropertyBuilder.setReturnType(BaseYangTypes.BOOLEAN_TYPE);

            genTOBuilder.addEqualsIdentity(genPropertyBuilder);
            genTOBuilder.addHashIdentity(genPropertyBuilder);
            genTOBuilder.addToStringProperty(genPropertyBuilder);
        }

        return genTOBuilder;
    }

    /**
     * Adds to the <code>genTOBuilder</code> the constant which contains regular expressions from
     * the <code>regularExpressions</code>.
     *
     * @param genTOBuilder generated TO builder to which are <code>regular expressions</code> added
     * @param expressions list of string which represent regular expressions
     */
    private static void addStringRegExAsConstant(final GeneratedTOBuilder genTOBuilder,
            final Map<String, String> expressions) {
        if (!expressions.isEmpty()) {
            genTOBuilder.addConstant(Types.listTypeFor(BaseYangTypes.STRING_TYPE), TypeConstants.PATTERN_CONSTANT_NAME,
                ImmutableMap.copyOf(expressions));
        }
    }

    /**
     * Creates generated TO with data about inner extended type <code>innerExtendedType</code>, about the package name
     * <code>typedefName</code> and about the generated TO name <code>typedefName</code>.
     *
     * <p>
     * It is assumed that <code>innerExtendedType</code> is already present in
     * {@link AbstractTypeProvider#genTypeDefsContextMap genTypeDefsContextMap} to be possible set it as extended type
     * for the returning generated TO.
     *
     * @param typedef Type Definition
     * @param innerExtendedType extended type which is part of some other extended type
     * @param basePackageName string with the package name of the module
     * @param moduleName Module Name
     * @return generated TO which extends generated TO for <code>innerExtendedType</code>
     * @throws IllegalArgumentException
     *             <ul>
     *             <li>if <code>extendedType</code> equals null</li>
     *             <li>if <code>basePackageName</code> equals null</li>
     *             <li>if <code>typedefName</code> equals null</li>
     *             </ul>
     */
    private GeneratedTransferObject provideGeneratedTOFromExtendedType(final TypeDefinition<?> typedef,
            final TypeDefinition<?> innerExtendedType, final String basePackageName, final String moduleName) {
        Preconditions.checkArgument(innerExtendedType != null, "Extended type cannot be NULL!");
        Preconditions.checkArgument(basePackageName != null, "String with base package name cannot be NULL!");

        final GeneratedTOBuilder genTOBuilder = newGeneratedTOBuilder(JavaTypeName.create(basePackageName,
            BindingMapping.getClassName(typedef.getQName())));
        genTOBuilder.setSchemaPath(typedef.getPath());
        genTOBuilder.setModuleName(moduleName);
        genTOBuilder.setTypedef(true);
        addCodegenInformation(genTOBuilder, typedef);

        final Restrictions r = BindingGeneratorUtil.getRestrictions(typedef);
        genTOBuilder.setRestrictions(r);
        addStringRegExAsConstant(genTOBuilder, resolveRegExpressionsFromTypedef(typedef));

        if (typedef.getStatus() == Status.DEPRECATED) {
            genTOBuilder.addAnnotation(DEPRECATED_ANNOTATION);
        }

        if (baseTypeDefForExtendedType(innerExtendedType) instanceof UnionTypeDefinition) {
            genTOBuilder.setIsUnion(true);
        }

        Map<Optional<Revision>, Map<String, GeneratedType>> modulesByDate = null;
        Map<String, GeneratedType> typeMap = null;
        final Module parentModule = findParentModule(schemaContext, innerExtendedType);
        if (parentModule != null) {
            modulesByDate = genTypeDefsContextMap.get(parentModule.getName());
            typeMap = modulesByDate.get(parentModule.getRevision());
        }

        if (typeMap != null) {
            final String innerTypeDef = innerExtendedType.getQName().getLocalName();
            final GeneratedType type = typeMap.get(innerTypeDef);
            if (type instanceof GeneratedTransferObject) {
                genTOBuilder.setExtendsType((GeneratedTransferObject) type);
            }
        }
        addUnitsToGenTO(genTOBuilder, typedef.getUnits().orElse(null));
        makeSerializable(genTOBuilder);

        return genTOBuilder.build();
    }

    /**
     * Add {@link java.io.Serializable} to implemented interfaces of this TO. Also compute and add serialVersionUID
     * property.
     *
     * @param gto transfer object which needs to be made serializable
     */
    private static void makeSerializable(final GeneratedTOBuilder gto) {
        gto.addImplementsType(Types.serializableType());
        final GeneratedPropertyBuilder prop = new GeneratedPropertyBuilderImpl("serialVersionUID");
        prop.setValue(Long.toString(SerialVersionHelper.computeDefaultSUID(gto)));
        gto.setSUID(prop);
    }

    /**
     * Finds out for each type definition how many immersion (depth) is necessary to get to the base type. Every type
     * definition is inserted to the map which key is depth and value is list of type definitions with equal depth.
     * In next step are lists from this map concatenated to one list in ascending order according to their depth. All
     * type definitions are in the list behind all type definitions on which depends.
     *
     * @param unsortedTypeDefinitions list of type definitions which should be sorted by depth
     * @return list of type definitions sorted according their each other dependencies (type definitions which are
     *              dependent on other type definitions are in list behind them).
     */
    private static List<TypeDefinition<?>> sortTypeDefinitionAccordingDepth(
            final Collection<TypeDefinition<?>> unsortedTypeDefinitions) {
        final List<TypeDefinition<?>> sortedTypeDefinition = new ArrayList<>();

        final Map<Integer, List<TypeDefinition<?>>> typeDefinitionsDepths = new TreeMap<>();
        for (TypeDefinition<?> unsortedTypeDefinition : unsortedTypeDefinitions) {
            final Integer depth = getTypeDefinitionDepth(unsortedTypeDefinition);
            List<TypeDefinition<?>> typeDefinitionsConcreteDepth =
                typeDefinitionsDepths.computeIfAbsent(depth, k -> new ArrayList<>());
            typeDefinitionsConcreteDepth.add(unsortedTypeDefinition);
        }

        // SortedMap guarantees order corresponding to keys in ascending order
        for (List<TypeDefinition<?>> v : typeDefinitionsDepths.values()) {
            sortedTypeDefinition.addAll(v);
        }

        return sortedTypeDefinition;
    }

    /**
     * Returns how many immersion is necessary to get from the type definition to the base type.
     *
     * @param typeDefinition type definition for which is depth sought.
     * @return number of immersions which are necessary to get from the type definition to the base type
     */
    private static int getTypeDefinitionDepth(final TypeDefinition<?> typeDefinition) {
        // FIXME: rewrite this in a non-recursive manner
        if (typeDefinition == null) {
            return 1;
        }
        final TypeDefinition<?> baseType = typeDefinition.getBaseType();
        if (baseType == null) {
            return 1;
        }

        int depth = 1;
        if (baseType.getBaseType() != null) {
            depth = depth + getTypeDefinitionDepth(baseType);
        } else if (baseType instanceof UnionTypeDefinition) {
            final List<TypeDefinition<?>> childTypeDefinitions = ((UnionTypeDefinition) baseType).getTypes();
            int maxChildDepth = 0;
            int childDepth = 1;
            for (TypeDefinition<?> childTypeDefinition : childTypeDefinitions) {
                childDepth = childDepth + getTypeDefinitionDepth(childTypeDefinition);
                if (childDepth > maxChildDepth) {
                    maxChildDepth = childDepth;
                }
            }
            return maxChildDepth;
        }
        return depth;
    }

    /**
     * Returns string which contains the same value as <code>name</code> but integer suffix is incremented by one. If
     * <code>name</code> contains no number suffix, a new suffix initialized at 1 is added. A suffix is actually
     * composed of a '$' marker, which is safe, as no YANG identifier can contain '$', and a unsigned decimal integer.
     *
     * @param name string with name of augmented node
     * @return string with the number suffix incremented by one (or 1 is added)
     */
    private static String provideAvailableNameForGenTOBuilder(final String name) {
        final int dollar = name.indexOf('$');
        if (dollar == -1) {
            return name + "$1";
        }

        final int newSuffix = Integer.parseUnsignedInt(name.substring(dollar + 1)) + 1;
        Preconditions.checkState(newSuffix > 0, "Suffix counter overflow");
        return name.substring(0, dollar + 1) + newSuffix;
    }

    public static void addUnitsToGenTO(final GeneratedTOBuilder to, final String units) {
        if (!Strings.isNullOrEmpty(units)) {
            to.addConstant(Types.STRING, "_UNITS", "\"" + units + "\"");
            final GeneratedPropertyBuilder prop = new GeneratedPropertyBuilderImpl("UNITS");
            prop.setReturnType(Types.STRING);
            to.addToStringProperty(prop);
        }
    }

    /**
     * Returns parent Yang Module for specified Schema Context in which Schema
     * Node is declared. If the Schema Node is not present in Schema Context the
     * operation will return <code>null</code>.
     *
     * @param context Schema Context
     * @param schemaNode Schema Node
     * @return Yang Module for specified Schema Context and Schema Node, if Schema Node is NOT present, the method will
     *         return <code>null</code>
     * @throws NullPointerException if any of the arguments is null
     */
    private static Module findParentModule(final SchemaContext context, final SchemaNode schemaNode) {
        return context.findModule(schemaNode.getQName().getModule()).orElse(null);
    }
}