/*
 * 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.nio.charset.StandardCharsets;

import org.eclipse.aether.util.concurrency.ConcurrentWeakCache;
import org.eclipse.aether.version.InvalidVersionSpecificationException;

/**
 * A version scheme using a generic version syntax and common sense sorting.
 * <p>
 * This scheme accepts versions of any form, interpreting a version as a sequence of numeric and alphabetic segments.
 * The characters '-', '_', and '.' as well as the mere transitions from digit to letter and vice versa delimit the
 * version segments. Delimiters are treated as equivalent.
 * </p>
 * <p>
 * Numeric segments are compared mathematically, alphabetic segments are compared lexicographically and
 * case-insensitively. However, the following qualifier strings are recognized and treated specially: "alpha" = "a" &lt;
 * "beta" = "b" &lt; "milestone" = "m" &lt; "cr" = "rc" &lt; "snapshot" &lt; "final" = "ga" &lt; "sp". All of those
 * well-known qualifiers are considered smaller/older than other strings. An empty segment/string is equivalent to 0.
 * </p>
 * <p>
 * In addition to the above mentioned qualifiers, the tokens "min" and "max" may be used as final version segment to
 * denote the smallest/greatest version having a given prefix. For example, "1.2.min" denotes the smallest version in
 * the 1.2 line, "1.2.max" denotes the greatest version in the 1.2 line. A version range of the form "[M.N.*]" is short
 * for "[M.N.min, M.N.max]".
 * </p>
 * <p>
 * Numbers and strings are considered incomparable against each other. Where version segments of different kind would
 * collide, comparison will instead assume that the previous segments are padded with trailing 0 or "ga" segments,
 * respectively, until the kind mismatch is resolved, e.g. "1-alpha" = "1.0.0-alpha" &lt; "1.0.1-ga" = "1.0.1".
 * </p>
 */
public class GenericVersionScheme extends VersionSchemeSupport {

    // Concurrent cache with weak keys and weak values: lock-free reads (volatile read, no lock
    // acquisition via ConcurrentHashMap), lock-striped writes, zero allocation on get() via
    // ThreadLocal lookup key, weak references allow GC under memory pressure.
    private final ConcurrentWeakCache<String, GenericVersion> versionCache = new ConcurrentWeakCache<>();

    @Override
    public GenericVersion parseVersion(final String version) throws InvalidVersionSpecificationException {
        GenericVersion v = versionCache.get(version);
        if (v == null) {
            v = versionCache.putIfAbsent(version, new GenericVersion(version));
        }
        return v;
    }

    /**
     * A handy main method that behaves similarly like maven-artifact ComparableVersion is, to make possible test
     * and possibly compare differences between the two.
     * <p>
     * To check how "1.2.7" compares to "1.2-SNAPSHOT", for example, you can issue
     * <pre>jbang --main=org.eclipse.aether.util.version.GenericVersionScheme org.apache.maven.resolver:maven-resolver-util:1.9.18 "1.2.7" "1.2-SNAPSHOT"</pre>
     * command to command line, output is very similar to that of ComparableVersion on purpose.
     */
    public static void main(String... args) {
        System.out.println(
                "Display parameters as parsed by Maven Resolver 'generic' scheme (in canonical form and as a list of tokens)"
                        + " and comparison result:");
        if (args.length == 0) {
            return;
        }

        GenericVersionScheme scheme = new GenericVersionScheme();
        GenericVersion prev = null;
        int i = 1;
        for (String version : args) {
            if (!StandardCharsets.US_ASCII.newEncoder().canEncode(version)) {
                System.out.println("WW Use of non-ASCII characters for version strings is not recommended.");
            }
            try {
                GenericVersion c = scheme.parseVersion(version);

                if (prev != null) {
                    int compare = prev.compareTo(c);
                    System.out.println(
                            "   " + prev + ' ' + ((compare == 0) ? "==" : ((compare < 0) ? "<" : ">")) + ' ' + version);
                }

                System.out.println((i++) + ". " + version + " -> " + c.asString() + "; tokens: " + c.asItems());

                prev = c;
            } catch (InvalidVersionSpecificationException e) {
                System.err.println("Invalid version: " + version + " - " + e.getMessage());
            }
        }
    }
}