core/src/main/java/org/apache/calcite/sql/validate/SqlNameMatchers.java

/*
 * 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 org.apache.calcite.sql.validate;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeField;
import org.apache.calcite.sql.SqlIdentifier;
import org.apache.calcite.util.Util;

import com.google.common.collect.ImmutableList;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;

import static java.util.Objects.requireNonNull;

/**
 * Helpers for {@link SqlNameMatcher}.
 */
public class SqlNameMatchers {

  private static final BaseMatcher CASE_SENSITIVE = new BaseMatcher(true);
  private static final BaseMatcher CASE_INSENSITIVE = new BaseMatcher(false);

  private SqlNameMatchers() {}

  /** Returns a name matcher with the given case sensitivity. */
  public static SqlNameMatcher withCaseSensitive(final boolean caseSensitive) {
    return caseSensitive ? CASE_SENSITIVE : CASE_INSENSITIVE;
  }

  /** Creates a name matcher that can suggest corrections to what the user
   * typed. It matches liberally (case-insensitively) and also records the last
   * match. */
  public static SqlNameMatcher liberal() {
    return new LiberalNameMatcher();
  }

  /** Partial implementation of {@link SqlNameMatcher}. */
  private static class BaseMatcher implements SqlNameMatcher {
    private final boolean caseSensitive;

    BaseMatcher(boolean caseSensitive) {
      this.caseSensitive = caseSensitive;
    }

    @Override public boolean isCaseSensitive() {
      return caseSensitive;
    }

    @Override public boolean matches(String string, String name) {
      return caseSensitive ? string.equals(name)
          : string.equalsIgnoreCase(name);
    }

    protected boolean listMatches(List<String> list0, List<String> list1) {
      if (list0.size() != list1.size()) {
        return false;
      }
      for (int i = 0; i < list0.size(); i++) {
        String s0 = list0.get(i);
        String s1 = list1.get(i);
        if (!matches(s0, s1)) {
          return false;
        }
      }
      return true;
    }

    @Override public <K extends List<String>, V> @Nullable V get(Map<K, V> map,
        List<String> prefixNames, List<String> names) {
      final List<String> key = concat(prefixNames, names);
      if (caseSensitive) {
        //noinspection SuspiciousMethodCalls
        return map.get(key);
      }
      for (Map.Entry<K, V> entry : map.entrySet()) {
        if (listMatches(key, entry.getKey())) {
          matched(prefixNames, entry.getKey());
          return entry.getValue();
        }
      }
      return null;
    }

    private static List<String> concat(List<String> prefixNames, List<String> names) {
      if (prefixNames.isEmpty()) {
        return names;
      } else {
        return ImmutableList.<String>builder().addAll(prefixNames).addAll(names)
            .build();
      }
    }

    protected void matched(List<String> prefixNames, List<String> names) {
    }

    protected List<String> bestMatch() {
      throw new UnsupportedOperationException();
    }

    @Override public String bestString() {
      return SqlIdentifier.getString(bestMatch());
    }

    @Override public @Nullable RelDataTypeField field(RelDataType rowType, String fieldName) {
      return rowType.getField(fieldName, caseSensitive, false);
    }

    @Override public int frequency(Iterable<String> names, String name) {
      int n = 0;
      for (String s : names) {
        if (matches(s, name)) {
          ++n;
        }
      }
      return n;
    }

    @Override public Set<String> createSet() {
      return isCaseSensitive()
          ? new LinkedHashSet<>()
          : new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
    }
  }

  /** Matcher that remembers the requests that were made of it. */
  private static class LiberalNameMatcher extends BaseMatcher {
    @Nullable List<String> matchedNames;

    LiberalNameMatcher() {
      super(false);
    }

    @Override protected boolean listMatches(List<String> list0,
        List<String> list1) {
      final boolean b = super.listMatches(list0, list1);
      if (b) {
        matchedNames = ImmutableList.copyOf(list1);
      }
      return b;
    }

    @Override protected void matched(List<String> prefixNames,
        List<String> names) {
      matchedNames =
          ImmutableList.copyOf(
              Util.startsWith(names, prefixNames)
                  ? Util.skip(names, prefixNames.size())
                  : names);
    }

    @Override public List<String> bestMatch() {
      return requireNonNull(matchedNames, "matchedNames");
    }
  }
}