/*
    * 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.eclipse.aether.util.version;
  
  import java.math.BigInteger;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Locale;
  
  import org.eclipse.aether.version.Version;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A generic version, that is a version that accepts any input string and tries to apply common sense sorting. See
   * {@link GenericVersionScheme} for details.
   */
  public final class GenericVersion implements Version {
  
      private final String version;
  
      private final List<Item> items;
  
      private final int hash;
  
      /**
       * Creates a generic version from the specified string.
       *
       * @param version the version string, must not be {@code null}
       */
      GenericVersion(String version) {
          this.version = requireNonNull(version, "version cannot be null");
          items = parse(version);
          hash = items.hashCode();
      }
  
      /**
       * Returns this instance backing string representation.
       *
       * @since 1.9.5
       */
      public String asString() {
          return version;
      }
  
      /**
       * Returns this instance tokenized representation as unmodifiable list.
       *
       * @since 1.9.5
       */
      public List<Item> asItems() {
          return items;
      }
  
      private static List<Item> parse(String version) {
          List<Item> items = new ArrayList<>();
  
          for (Tokenizer tokenizer = new Tokenizer(version); tokenizer.next(); ) {
              Item item = tokenizer.toItem();
              items.add(item);
          }
  
          trimPadding(items);
  
          return Collections.unmodifiableList(items);
      }
  
      /**
       * Visible for testing.
       */
      static void trimPadding(List<Item> items) {
          Boolean number = null;
          int end = items.size() - 1;
          for (int i = end; i > 0; i--) {
              Item item = items.get(i);
              if (!Boolean.valueOf(item.isNumber()).equals(number)) {
                  end = i;
                  number = item.isNumber();
              }
              if (end == i
                      && (i == items.size() - 1 || items.get(i - 1).isNumber() == item.isNumber())
                      && item.compareTo(null) == 0) {
                 items.remove(i);
                 end--;
             }
         }
     }
 
     @Override
     public int compareTo(Version obj) {
         final List<Item> these = items;
         final List<Item> those = ((GenericVersion) obj).items;
 
         boolean number = true;
 
         for (int index = 0; ; index++) {
             if (index >= these.size() && index >= those.size()) {
                 return 0;
             } else if (index >= these.size()) {
                 return -comparePadding(those, index, null);
             } else if (index >= those.size()) {
                 return comparePadding(these, index, null);
             }
 
             Item thisItem = these.get(index);
             Item thatItem = those.get(index);
 
             if (thisItem.isNumber() != thatItem.isNumber()) {
                 if (index == 0) {
                     return thisItem.compareTo(thatItem);
                 }
                 if (number == thisItem.isNumber()) {
                     return comparePadding(these, index, number);
                 } else {
                     return -comparePadding(those, index, number);
                 }
             } else {
                 int rel = thisItem.compareTo(thatItem);
                 if (rel != 0) {
                     return rel;
                 }
                 number = thisItem.isNumber();
             }
         }
     }
 
     private static int comparePadding(List<Item> items, int index, Boolean number) {
         int rel = 0;
         for (int i = index; i < items.size(); i++) {
             Item item = items.get(i);
             if (number != null && number != item.isNumber()) {
                 // do not stop here, but continue, skipping non-number members
                 continue;
             }
             rel = item.compareTo(null);
             if (rel != 0) {
                 break;
             }
         }
         return rel;
     }
 
     @Override
     public boolean equals(Object obj) {
         return (obj instanceof GenericVersion) && compareTo((GenericVersion) obj) == 0;
     }
 
     @Override
     public int hashCode() {
         return hash;
     }
 
     @Override
     public String toString() {
         return version;
     }
 
     static final class Tokenizer {
         private final String version;
 
         private final int versionLength;
 
         private int index;
 
         private String token;
 
         private boolean number;
 
         private boolean terminatedByNumber;
 
         Tokenizer(String version) {
             this.version = (!version.isEmpty()) ? version : "0";
             this.versionLength = this.version.length();
         }
 
         public boolean next() {
             if (index >= versionLength) {
                 return false;
             }
 
             int state = -2;
 
             int start = index;
             int end = versionLength;
             terminatedByNumber = false;
 
             for (; index < versionLength; index++) {
                 char c = version.charAt(index);
 
                 if (c == '.' || c == '-' || c == '_') {
                     end = index;
                     index++;
                     break;
                 } else {
                     if (c >= '0' && c <= '9') { // only ASCII digits
                         int digit = c - '0';
                         if (state == -1) {
                             end = index;
                             terminatedByNumber = true;
                             break;
                         }
                         if (state == 0) {
                             // normalize numbers and strip leading zeros (prereq for Integer/BigInteger handling)
                             start++;
                         }
                         state = (state > 0 || digit > 0) ? 1 : 0;
                     } else {
                         if (state >= 0) {
                             end = index;
                             break;
                         }
                         state = -1;
                     }
                 }
             }
 
             if (end - start > 0) {
                 token = version.substring(start, end);
                 number = state >= 0;
             } else {
                 token = "0";
                 number = true;
             }
 
             return true;
         }
 
         @Override
         public String toString() {
             return String.valueOf(token);
         }
 
         public Item toItem() {
             if (number) {
                 try {
                     if (token.length() < 10) {
                         return new Item(Item.KIND_INT, Integer.parseInt(token));
                     } else {
                         return new Item(Item.KIND_BIGINT, new BigInteger(token));
                     }
                 } catch (NumberFormatException e) {
                     throw new IllegalStateException(e);
                 }
             } else {
                 if (index >= version.length()) {
                     if ("min".equalsIgnoreCase(token)) {
                         return Item.MIN;
                     } else if ("max".equalsIgnoreCase(token)) {
                         return Item.MAX;
                     }
                 }
                 if (terminatedByNumber && token.length() == 1) {
                     switch (token.charAt(0)) {
                         case 'a':
                         case 'A':
                             token = GenericQualifiers.LABEL_ALPHA;
                             break;
                         case 'b':
                         case 'B':
                             token = GenericQualifiers.LABEL_BETA;
                             break;
                         case 'm':
                         case 'M':
                             token = GenericQualifiers.LABEL_MILESTONE;
                             break;
                         default:
                     }
                 }
                 token = token.toLowerCase(Locale.ENGLISH);
                 return GenericQualifiers.tokenQualifier(token)
                         .map(integer -> new Item(Item.KIND_QUALIFIER, integer))
                         .orElseGet(() -> new Item(Item.KIND_STRING, token));
             }
         }
     }
 
     static final class Item {
 
         static final int KIND_MAX = 8;
 
         static final int KIND_BIGINT = 5;
 
         static final int KIND_INT = 4;
 
         static final int KIND_STRING = 3;
 
         static final int KIND_QUALIFIER = 2;
 
         static final int KIND_MIN = 0;
 
         static final Item MAX = new Item(KIND_MAX, "max");
 
         static final Item MIN = new Item(KIND_MIN, "min");
 
         private final int kind;
 
         private final Object value;
 
         Item(int kind, Object value) {
             this.kind = kind;
             this.value = value;
         }
 
         public boolean isNumber() {
             return (kind & KIND_QUALIFIER) == 0; // i.e. kind != string/qualifier
         }
 
         public int compareTo(Item that) {
             int rel;
             if (that == null) {
                 // null in this context denotes the pad item (0 or "ga")
                 switch (kind) {
                     case KIND_MIN:
                         rel = -1;
                         break;
                     case KIND_MAX:
                     case KIND_BIGINT:
                     case KIND_STRING:
                         rel = 1;
                         break;
                     case KIND_INT:
                     case KIND_QUALIFIER:
                         rel = (Integer) value;
                         break;
                     default:
                         throw new IllegalStateException("unknown version item kind " + kind);
                 }
             } else {
                 rel = kind - that.kind;
                 if (rel == 0) {
                     switch (kind) {
                         case KIND_MAX:
                         case KIND_MIN:
                             break;
                         case KIND_BIGINT:
                             rel = ((BigInteger) value).compareTo((BigInteger) that.value);
                             break;
                         case KIND_INT:
                         case KIND_QUALIFIER:
                             rel = ((Integer) value).compareTo((Integer) that.value);
                             break;
                         case KIND_STRING:
                             rel = ((String) value).compareToIgnoreCase((String) that.value);
                             break;
                         default:
                             throw new IllegalStateException("unknown version item kind " + kind);
                     }
                 }
             }
             return rel;
         }
 
         @Override
         public boolean equals(Object obj) {
             return (obj instanceof Item) && compareTo((Item) obj) == 0;
         }
 
         @Override
         public int hashCode() {
             return value.hashCode() + kind * 31;
         }
 
         @Override
         public String toString() {
             return String.valueOf(value);
         }
     }
 }