/*
 * 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.ext.calcite.sqlnamematcher;

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

import java.util.ArrayList;
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}.
 *
 * <p>This is a standalone version that can be used independently of Apache Calcite.
 */
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 {
        List<String> result = new ArrayList<>(prefixNames.size() + names.size());
        result.addAll(prefixNames);
        result.addAll(names);
        return result;
      }
    }

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

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

    @Override public String bestString() {
      return listToString(bestMatch());
    }

    @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 = new ArrayList<>(list1);
      }
      return b;
    }

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

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

  // Utility methods

  /** Returns whether one list is a prefix of another. */
  private static <E> boolean startsWith(List<E> list0, List<E> list1) {
    if (list0 == list1) {
      return true;
    }
    final int size = list1.size();
    if (list0.size() < size) {
      return false;
    }
    for (int i = 0; i < size; i++) {
      if (!java.util.Objects.equals(list0.get(i), list1.get(i))) {
        return false;
      }
    }
    return true;
  }

  /** Returns all but the first {@code n} elements of a list. */
  private static <E> List<E> skip(List<E> list, int fromIndex) {
    return fromIndex == 0 ? list : list.subList(fromIndex, list.size());
  }

  /** Converts a list to a dotted identifier string. */
  private static String listToString(List<String> names) {
    final int max = names.size() - 1;
    switch (max) {
    case -1:
      return "";
    case 0:
      return String.valueOf(names.get(0));
    default:
      final StringBuilder buf = new StringBuilder();
      for (int i = 0;; i++) {
        buf.append(names.get(i));
        if (i == max) {
          return buf.toString();
        }
        buf.append(".");
      }
    }
  }
}