/*
 * Copyright (c) 2020 PANTHEON.tech, 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.spi.meta;

import static com.google.common.base.Verify.verifyNotNull;

import com.google.common.annotations.Beta;
import com.google.common.base.VerifyException;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.Nullable;
import org.opendaylight.yangtools.concepts.Immutable;
import org.opendaylight.yangtools.yang.common.QName;
import org.opendaylight.yangtools.yang.common.QNameModule;
import org.opendaylight.yangtools.yang.model.api.DataSchemaNode;
import org.opendaylight.yangtools.yang.model.api.SchemaNode;
import org.opendaylight.yangtools.yang.model.api.SchemaNodeDefaults;
import org.opendaylight.yangtools.yang.model.api.SchemaPath;
import org.opendaylight.yangtools.yang.model.api.meta.DeclaredStatement;
import org.opendaylight.yangtools.yang.model.api.meta.EffectiveStatement;

/**
 * Effective view of a {@link StmtContext} for the purposes of creating an {@link EffectiveStatement}.
 */
@Beta
public interface EffectiveStmtCtx extends CommonStmtCtx, StmtContextCompat, Immutable {
    /**
     * Return parent of this context, if there is one. All statements except for top-level source statements, such as
     * {@code module} and {@code submodule}.
     *
     * @return Parent context, or null if this statement is the root
     */
    @Nullable Parent effectiveParent();

    /**
     * Return parent of this context.
     *
     * @return Parent context
     * @throws VerifyException if this context is already the root
     */
    default @NonNull Parent getEffectiveParent() {
        return verifyNotNull(effectiveParent(), "Attempted to access beyond root context");
    }

    /**
     * Minimum amount of parent state required to build an accurate effective view of a particular child. Child state
     * is expressed as {@link Current}.
     */
    @Beta
    interface Parent extends EffectiveStmtCtx {
        /**
         * Effective {@code config} statement value.
         */
        @Beta
        enum EffectiveConfig {
            /**
             * We have an effective {@code config true} statement.
             */
            TRUE(Boolean.TRUE),
            /**
             * We have an effective {@code config false} statement.
             */
            FALSE(Boolean.FALSE),
            /**
             * We are in a context where {@code config} statements are ignored.
             */
            IGNORED(null),
            /**
             * We are in a context where {@code config} is not determined, such as within a {@code grouping}.
             */
            UNDETERMINED(null);

            private final Boolean config;

            EffectiveConfig(final @Nullable Boolean config) {
                this.config = config;
            }

            /**
             * Return this value as a {@link Boolean} for use with {@link DataSchemaNode#effectiveConfig()}.
             *
             * @return A boolean or null
             */
            public @Nullable Boolean asNullable() {
                return config;
            }
        }

        /**
         * Return the effective {@code config} statement value.
         *
         * @return This statement's effective config
         */
        @NonNull EffectiveConfig effectiveConfig();

        // FIXME: 7.0.0: this is currently only used by AbstractTypeStatement
        @NonNull QNameModule effectiveNamespace();

        /**
         * Return the effective path of this statement. This method is intended for use with statements which naturally
         * have a {@link QName} identifier and this identifier forms the ultimate step in their
         * {@link SchemaNode#getPath()}.
         *
         * <p>
         * Returned object conforms to {@link SchemaPathSupport}'s view of how these are to be handled. Users of this
         * method are expected to consult {@link SchemaNodeDefaults#extractQName(Immutable)} and
         * {@link SchemaNodeDefaults#extractPath(Object, Immutable)} to ensure correct implementation behaviour with
         * respect to {@link SchemaNode#getQName()} and {@link SchemaNode#getPath()} respectively.
         *
         * @return An {@link Immutable} effective path object
         */
        // FIXME: Remove this when SchemaNode.getPath() is removed. QName users will store getArgument() instead.
        default @NonNull Immutable effectivePath() {
            return SchemaPathSupport.toEffectivePath(getSchemaPath());
        }

        /**
         * Return an optional-to-provide path for {@link SchemaNode#getPath()}. The result of this method is expected
         * to be consulted with {@link SchemaNodeDefaults#throwUnsupportedIfNull(Object, SchemaPath)} to get consistent
         * API behaviour.
         *
         * @return Potentially-null {@link SchemaPath}.
         */
        // FIXME: Remove this when SchemaNode.getPath() is removed
        default @Nullable SchemaPath optionalPath() {
            return SchemaPathSupport.toOptionalPath(getSchemaPath());
        }

        /**
         * Return the {@link SchemaNode#getPath()} of this statement. Not all statements have a SchemaPath, in which
         * case null is returned.
         *
         * @return SchemaPath or null
         */
        // FIXME: Remove this when SchemaNode.getPath() is removed
        @Nullable SchemaPath schemaPath();

        /**
         * Return the {@link SchemaNode#getPath()} of this statement, failing if it is not present.
         *
         * @return A SchemaPath.
         * @throws VerifyException if {@link #schemaPath()} returns null
         */
        // FIXME: Remove this when SchemaNode.getPath() is removed
        default @NonNull SchemaPath getSchemaPath() {
            return verifyNotNull(schemaPath(), "Missing path for %s", this);
        }
    }

    /**
     * Minimum amount of state required to build an accurate effective view of a statement. This is a strict superset
     * of information available in {@link Parent}.
     *
     * @param <A> Argument type
     * @param <D> Class representing declared version of this statement
     */
    @Beta
    interface Current<A, D extends DeclaredStatement<A>> extends Parent, NamespaceStmtCtx, BoundStmtCtxCompat<A, D> {

        @NonNull QName moduleName();

        @Nullable EffectiveStatement<?, ?> original();

        default <T> @Nullable T original(final @NonNull Class<T> type) {
            return type.cast(original());
        }

        // FIXME: 7.0.0: this method should be moved to stmt.type in some shape or form
        @NonNull QName argumentAsTypeQName();

        /**
         * Summon the <a href="https://en.wikipedia.org/wiki/Rabbit_of_Caerbannog">Rabbit of Caerbannog</a>.
         *
         * @param <E> Effective Statement representation
         * @return The {@code Legendary Black Beast of Arrrghhh}.
         */
        // FIXME: YANGTOOLS-1186: lob the Holy Hand Grenade of Antioch
        @Deprecated
        <E extends EffectiveStatement<A, D>> @NonNull StmtContext<A, D, E> caerbannog();

        /**
         * Compare another context for equality of {@code getEffectiveParent().getSchemaPath()}, just in a safer manner.
         *
         * @param other Other {@link Current}
         * @return True if {@code other} has parent path equal to this context's parent path.
         */
        // FIXME: Remove this when SchemaNode.getPath() is removed
        default boolean equalParentPath(final Current<A, D> other) {
            final Parent ours = effectiveParent();
            final Parent theirs = other.effectiveParent();
            return ours == theirs
                || ours != null && theirs != null && SchemaPathSupport.effectivelyEqual(
                    ours.schemaPath(), theirs.schemaPath());
        }
    }
}