/*
 * 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 gudusoft.gsqlparser.sqlenv;

import gudusoft.gsqlparser.EDbVendor;

import java.util.*;

/**
 * Vendor-aware and type-aware name comparison utilities over the CANONICAL
 * identifier-equality engine (unification plan P0d follow-up).
 *
 * <p>Equality delegates to {@link IdentifierService#areEqual} on THIS service's configured
 * profile and the set/dedup utilities key by {@link CanonKey} from the same service, so every
 * operation here observes exactly one relation. Built from a bare vendor that relation is the
 * vendor default ({@code SQLUtil.sameName} / {@code TSQLEnv.compareIdentifier}); built from an
 * analysis's {@link IdentifierService} it is that analysis's effective configuration. The previous
 * implementation routed through the SqlNameMatcher framework configured from the legacy
 * per-type case booleans, which collapsed quoted-case distinctions the canonical rules
 * preserve (e.g. BigQuery tables, Couchbase).</p>
 *
 * @since 3.2.0.3 (Phase 1); canonical since P0d
 */
public class NameService {

    private final EDbVendor vendor;
    private final IdentifierProfile profile;
    private final IdentifierService service;

    /**
     * Creates a new NameService under the vendor's DEFAULT identifier configuration.
     *
     * @param vendor the database vendor
     */
    public NameService(EDbVendor vendor) {
        if (vendor == null) {
            throw new IllegalArgumentException("vendor cannot be null");
        }
        this.vendor = vendor;
        this.profile = IdentifierProfile.forVendor(vendor, IdentifierProfile.VendorFlags.defaults());
        this.service = IdentifierService.defaultServiceFor(vendor);
    }

    /**
     * A NameService over ONE analysis's identifier service, so the comparisons and sets built here
     * observe that analysis's per-category configuration instead of the vendor default.
     *
     * <p>A factory rather than a constructor overload on purpose: {@code new NameService(null)}
     * would otherwise become ambiguous against {@link #NameService(EDbVendor)} and break callers
     * that already compile.
     *
     * @param service the frozen service of the current analysis
     * @return a name service delegating to that service
     */
    public static NameService forIdentifierService(IdentifierService service) {
        return new NameService(service);
    }

    private NameService(IdentifierService service) {
        if (service == null) {
            throw new IllegalArgumentException("service cannot be null");
        }
        this.service = service;
        this.profile = service.getProfile();
        this.vendor = this.profile.getVendor();
    }

    /**
     * The identifier service every comparison here delegates to — the single engine, configured
     * for this environment.
     *
     * @return the identifier service
     */
    public IdentifierService getIdentifierService() {
        return service;
    }

    /**
     * The effective identifier configuration behind {@link #getIdentifierService()}.
     *
     * @return the identifier profile
     */
    public IdentifierProfile getIdentifierProfile() {
        return profile;
    }

    /**
     * Returns the database vendor associated with this service.
     *
     * @return the database vendor
     */
    public EDbVendor getVendor() {
        return vendor;
    }

    /**
     * Checks if two names are equal under the canonical identifier-equality relation
     * ({@link IdentifierService#areEqual}) for this service’s configuration and object type.
     *
     * @param type the SQL object type (table, column, function, etc.)
     * @param name1 the first name to compare
     * @param name2 the second name to compare
     * @return true if the names refer to the same object
     */
    public boolean equals(ESQLDataObjectType type, String name1, String name2) {
        return service.areEqual(name1, name2, type);
    }

    /**
     * Finds the index of a name in a collection under canonical equality.
     *
     * <p>This is a case-aware version of {@code List.indexOf()}.</p>
     *
     * @param type the SQL object type
     * @param names the collection of names to search
     * @param target the name to find
     * @return the index of the first matching name, or -1 if not found
     */
    public int indexOf(ESQLDataObjectType type, Iterable<String> names, String target) {
        if (names == null || target == null) {
            return -1;
        }

        int index = 0;
        for (String name : names) {
            if (equals(type, name, target)) {
                return index;
            }
            index++;
        }
        return -1;
    }

    /**
     * Creates a distinct copy of a collection, removing canonical duplicates.
     *
     * <p>Preserves insertion order and the first spelling seen. For example, for a
     * case-insensitive domain:</p>
     * <pre>
     * ["foo", "FOO", "bar", "Bar"] → ["foo", "bar"]
     * </pre>
     *
     * @param type the SQL object type
     * @param names the collection of names (may contain duplicates)
     * @return a new list with duplicates removed, preserving order
     */
    public List<String> distinctCopy(ESQLDataObjectType type, Iterable<String> names) {
        if (names == null) {
            return new ArrayList<>();
        }

        Set<String> seen = createSet(type);
        List<String> result = new ArrayList<>();

        for (String name : names) {
            if (name != null && seen.add(name)) {
                result.add(name);
            }
        }

        return result;
    }

    /**
     * Creates a Set whose membership follows canonical name equality: names are the
     * same element iff their {@link CanonKey}s are equal.
     *
     * @param type the SQL object type
     * @return a new Set with canonical name equality
     */
    public Set<String> createSet(ESQLDataObjectType type) {
        return new NameSet(type);
    }

    /**
     * Whether the UNQUOTED comparison policy for this object type is case-sensitive.
     *
     * <p>Quoted operands may follow a different rule (quoted-case-preserving vendors);
     * this describes only the unquoted policy from the vendor's identifier rules. A
     * collation-based cell answers from its collation ({@code _CS_AI}, {@code _BIN2}: yes;
     * {@code _CI_AS}: no) — see {@link IdentifierService#isCaseSensitive}.</p>
     *
     * @param type the object type
     * @return true if unquoted names compare case-sensitively
     */
    public boolean isCaseSensitive(ESQLDataObjectType type) {
        return service.isCaseSensitive(type);
    }

    /**
     * Internal Set keyed by {@link CanonKey}: membership mirrors canonical equality
     * exactly, preserving insertion order and the first spelling of each name.
     */
    private class NameSet extends AbstractSet<String> {
        private final ESQLDataObjectType type;
        private final Map<CanonKey, String> backingMap; // canonical key -> first spelling

        NameSet(ESQLDataObjectType type) {
            this.type = type;
            this.backingMap = new LinkedHashMap<>();
        }

        @Override
        public boolean add(String name) {
            if (name == null) {
                throw new NullPointerException("NameSet does not permit null elements");
            }
            return backingMap.putIfAbsent(service.canonKey(name, type), name) == null;
        }

        @Override
        public boolean contains(Object o) {
            if (!(o instanceof String)) {
                return false;
            }
            return backingMap.containsKey(service.canonKey((String) o, type));
        }

        @Override
        public boolean remove(Object o) {
            if (!(o instanceof String)) {
                return false;
            }
            return backingMap.remove(service.canonKey((String) o, type)) != null;
        }

        @Override
        public Iterator<String> iterator() {
            return backingMap.values().iterator();
        }

        @Override
        public int size() {
            return backingMap.size();
        }

        @Override
        public void clear() {
            backingMap.clear();
        }
    }
}