/*
 * Copyright (c) 2018 Pantheon Technologies, s.r.o. 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.yangtools.yang.parser.rfc7950.stmt;

import static com.google.common.base.Verify.verify;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.Beta;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import java.lang.invoke.VarHandle;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Optional;
import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.yangtools.yang.common.QName;
import org.opendaylight.yangtools.yang.model.api.DataNodeContainer;
import org.opendaylight.yangtools.yang.model.api.DataSchemaNode;
import org.opendaylight.yangtools.yang.model.api.meta.DeclaredStatement;
import org.opendaylight.yangtools.yang.model.api.meta.EffectiveStatement;
import org.opendaylight.yangtools.yang.model.api.meta.IdentifierNamespace;
import org.opendaylight.yangtools.yang.model.api.stmt.CaseEffectiveStatement;
import org.opendaylight.yangtools.yang.model.api.stmt.ChoiceEffectiveStatement;
import org.opendaylight.yangtools.yang.model.api.stmt.DataTreeAwareEffectiveStatement;
import org.opendaylight.yangtools.yang.model.api.stmt.DataTreeEffectiveStatement;
import org.opendaylight.yangtools.yang.model.api.stmt.SchemaTreeAwareEffectiveStatement;
import org.opendaylight.yangtools.yang.model.api.stmt.SchemaTreeEffectiveStatement;
import org.opendaylight.yangtools.yang.parser.spi.meta.StmtContext;
import org.opendaylight.yangtools.yang.parser.spi.source.SourceException;
import org.opendaylight.yangtools.yang.parser.spi.source.StatementSourceReference;

/**
 * An {@link AbstractEffectiveDocumentedNode} which can optionally support {@link SchemaTreeAwareEffectiveStatement}.
 *
 * @param <A> Argument type ({@link Void} if statement does not have argument.)
 * @param <D> Class representing declared version of this statement.
 * @author Robert Varga
 */
@Beta
public abstract class AbstractSchemaEffectiveDocumentedNode<A, D extends DeclaredStatement<A>>
        extends AbstractEffectiveDocumentedNode<A, D> {
    private final ImmutableMap<QName, DataTreeEffectiveStatement<?>> dataTreeNamespace;
    private final ImmutableMap<QName, SchemaTreeEffectiveStatement<?>> schemaTreeNamespace;

    protected AbstractSchemaEffectiveDocumentedNode(final StmtContext<A, D, ?> ctx) {
        super(ctx);

        // This check is rather weird, but comes from our desire to lower memory footprint while providing both
        // EffectiveStatements and SchemaNode interfaces -- which do not overlap completely where child lookups are
        // concerned. This ensures that we have SchemaTree index available for use with child lookups.
        if (this instanceof SchemaTreeAwareEffectiveStatement || this instanceof DataNodeContainer) {
            schemaTreeNamespace = createSchemaTreeNamespace(ctx.getStatementSourceReference(),
                effectiveSubstatements());
        } else {
            schemaTreeNamespace = ImmutableMap.of();
        }
        if (this instanceof DataTreeAwareEffectiveStatement && !schemaTreeNamespace.isEmpty()) {
            dataTreeNamespace = createDataTreeNamespace(ctx.getStatementSourceReference(), schemaTreeNamespace);
        } else {
            dataTreeNamespace = ImmutableMap.of();
        }
    }

    @Override
    @SuppressWarnings("unchecked")
    protected <K, V, N extends IdentifierNamespace<K, V>> Optional<? extends Map<K, V>> getNamespaceContents(
            final Class<N> namespace) {
        if (this instanceof SchemaTreeAwareEffectiveStatement
                && SchemaTreeAwareEffectiveStatement.Namespace.class.equals(namespace)) {
            return Optional.of((Map<K, V>) schemaTreeNamespace);
        }
        if (this instanceof DataTreeAwareEffectiveStatement
                && DataTreeAwareEffectiveStatement.Namespace.class.equals(namespace)) {
            return Optional.of((Map<K, V>) dataTreeNamespace);
        }
        return super.getNamespaceContents(namespace);
    }

    protected final <T> @NonNull ImmutableSet<T> derivedSet(final VarHandle vh, final @NonNull Class<T> clazz) {
        final ImmutableSet<T> existing = (ImmutableSet<T>) vh.getAcquire(this);
        return existing != null ? existing : loadSet(vh, clazz);
    }

    /**
     * Indexing support for {@link DataNodeContainer#findDataChildByName(QName)}.
     */
    protected final Optional<DataSchemaNode> findDataSchemaNode(final QName name) {
        // Only DataNodeContainer subclasses should be calling this method
        verify(this instanceof DataNodeContainer);
        final SchemaTreeEffectiveStatement<?> child = schemaTreeNamespace.get(requireNonNull(name));
        return child instanceof DataSchemaNode ? Optional.of((DataSchemaNode) child) : Optional.empty();
    }

    static @NonNull ImmutableMap<QName, SchemaTreeEffectiveStatement<?>> createSchemaTreeNamespace(
            final StatementSourceReference ref, final Collection<? extends EffectiveStatement<?, ?>> substatements) {
        final Map<QName, SchemaTreeEffectiveStatement<?>> schemaChildren = new LinkedHashMap<>();
        substatements.stream().filter(SchemaTreeEffectiveStatement.class::isInstance)
            .forEach(child -> putChild(schemaChildren, (SchemaTreeEffectiveStatement) child, ref, "schema"));
        return ImmutableMap.copyOf(schemaChildren);
    }

    static @NonNull ImmutableMap<QName, DataTreeEffectiveStatement<?>> createDataTreeNamespace(
            final StatementSourceReference ref,
            final ImmutableMap<QName, SchemaTreeEffectiveStatement<?>> schemaTreeNamespace) {
        final Map<QName, DataTreeEffectiveStatement<?>> dataChildren = new LinkedHashMap<>();
        boolean sameAsSchema = true;

        for (SchemaTreeEffectiveStatement<?> child : schemaTreeNamespace.values()) {
            if (child instanceof DataTreeEffectiveStatement) {
                putChild(dataChildren, (DataTreeEffectiveStatement<?>) child, ref, "data");
            } else {
                sameAsSchema = false;
                putChoiceDataChildren(dataChildren, ref, child);
            }
        }

        // This is a mighty hack to lower memory usage: if we consumed all schema tree children as data nodes,
        // the two maps are equal and hence we can share the instance.
        return sameAsSchema ? (ImmutableMap) schemaTreeNamespace : ImmutableMap.copyOf(dataChildren);
    }

    @SuppressWarnings("unchecked")
    private <T> @NonNull ImmutableSet<T> loadSet(final VarHandle vh, final @NonNull Class<T> clazz) {
        final ImmutableSet<T> computed = ImmutableSet.copyOf(allSubstatementsOfType(clazz));
        final Object witness = vh.compareAndExchangeRelease(this, null, computed);
        return witness == null ? computed : (ImmutableSet<T>) witness;
    }

    private static <T extends SchemaTreeEffectiveStatement<?>> void putChild(final Map<QName, T> map,
            final T child, final StatementSourceReference ref, final String tree) {
        final QName id = child.getIdentifier();
        final T prev = map.putIfAbsent(id, child);
        SourceException.throwIf(prev != null, ref,
                "Cannot add %s tree child with name %s, a conflicting child already exists", tree, id);
    }

    private static void putChoiceDataChildren(final Map<QName, DataTreeEffectiveStatement<?>> map,
            final StatementSourceReference ref, final SchemaTreeEffectiveStatement<?> child) {
        // For choice statements go through all their cases and fetch their data children
        if (child instanceof ChoiceEffectiveStatement) {
            child.streamEffectiveSubstatements(CaseEffectiveStatement.class).forEach(
                caseStmt -> caseStmt.streamEffectiveSubstatements(SchemaTreeEffectiveStatement.class).forEach(stmt -> {
                    if (stmt instanceof DataTreeEffectiveStatement) {
                        putChild(map, (DataTreeEffectiveStatement<?>) stmt, ref, "data");
                    } else {
                        putChoiceDataChildren(map, ref, stmt);
                    }
                }));
        }
    }
}