/*
 * Copyright (c) 2012-2020 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

module antlr.v4.runtime.RuntimeMetaData;

import std.algorithm : min;
import std.stdio : stderr;
import std.string : indexOf;

/**
 * This class provides access to the current version of the ANTLR 4 runtime
 * library as compile-time and runtime constants, along with methods for
 * checking for matching version numbers and notifying listeners in the case
 * where a version mismatch is detected.
 *
 * <p>
 * The runtime version information is provided by {@link #VERSION} and
 * {@link #getRuntimeVersion()}. Detailed information about these values is
 * provided in the documentation for each member.</p>
 *
 * <p>
 * The runtime version check is implemented by {@link #checkVersion}. Detailed
 * information about incorporating this call into user code, as well as its use
 * in generated code, is provided in the documentation for the method.</p>
 *
 * <p>
 * Version strings x.y and x.y.z are considered "compatible" and no error
 * would be generated. Likewise, version strings x.y-SNAPSHOT and x.y.z are
 * considered "compatible" because the major and minor components x.y
 * are the same in each.</p>
 *
 * <p>
 * To trap any error messages issued by this code, use System.setErr()
 * in your main() startup code.
 * </p>
 */
class RuntimeMetaData
{

    enum string VERSION = "4.8.0";

    /**
     * This method provides the ability to detect mismatches between the version
     * of ANTLR 4 used to generate a parser, the version of the ANTLR runtime a
     * parser was compiled against, and the version of the ANTLR runtime which
     * is currently executing.
     *
     * <p>
     * The version check is designed to detect the following two specific
     * scenarios.</p>
     *
     * <ul>
     * <li>The ANTLR Tool version used for code generation does not match the
     * currently executing runtime version.</li>
     * <li>The ANTLR Runtime version referenced at the time a parser was
     * compiled does not match the currently executing runtime version.</li>
     * </ul>
     *
     * <p>
     * Starting with ANTLR 4.3, the code generator emits a call to this method
     * using two constants in each generated lexer and parser: a hard-coded
     * constant indicating the version of the tool used to generate the parser
     * and a reference to the compile-time constant {@link #VERSION}. At
     * runtime, this method is called during the initialization of the generated
     * parser to detect mismatched versions, and notify the registered listeners
     * prior to creating instances of the parser.</p>
     *
     * <p>
     * This method does not perform any detection or filtering of semantic
     * changes between tool and runtime versions. It simply checks for a
     * version match and emits an error to stderr if a difference
     * is detected.</p>
     *
     * <p>
     * Note that some breaking changes between releases could result in other
     * types of runtime exceptions, such as a {@link LinkageError}, prior to
     * calling this method. In these cases, the underlying version mismatch will
     * not be reported here. This method is primarily intended to
     * notify users of potential semantic changes between releases that do not
     * result in binary compatibility problems which would be detected by the
     * class loader. As with semantic changes, changes that break binary
     * compatibility between releases are mentioned in the release notes
     * accompanying the affected release.</p>
     *
     * <p>
     * <strong>Additional note for target developers:</strong> The version check
     * implemented by this class is designed to address specific compatibility
     * concerns that may arise during the execution of Java applications. Other
     * targets should consider the implementation of this method in the context
     * of that target's known execution environment, which may or may not
     * resemble the design provided for the Java target.</p>
     *
     *  @param generatingToolVersion The version of the tool used to generate a parser.
     * This value may be null when called from user code that was not generated
     * by, and does not reference, the ANTLR 4 Tool itself.
     *  @param compileTimeVersion The version of the runtime the parser was
     * compiled against. This should always be passed using a direct reference
     * to {@link #VERSION}.
     */
    public static void checkVersion(string generatingToolVersion, string compileTimeVersion)
    {
        string runtimeVersion = VERSION;
        bool runtimeConflictsWithGeneratingTool = false;
        bool runtimeConflictsWithCompileTimeTool = false;

        if (generatingToolVersion) {
            runtimeConflictsWithGeneratingTool =
                (runtimeVersion != generatingToolVersion) &&
                (getMajorMinorVersion(runtimeVersion) != getMajorMinorVersion(generatingToolVersion));
        }

        runtimeConflictsWithCompileTimeTool =
            (runtimeVersion != compileTimeVersion) &&
            (getMajorMinorVersion(runtimeVersion) != getMajorMinorVersion(compileTimeVersion));

        if (runtimeConflictsWithGeneratingTool) {
            stderr.writefln("ANTLR Tool version %s used for code generation does not match the current runtime version %s",
                              generatingToolVersion, runtimeVersion);
        }
        if ( runtimeConflictsWithCompileTimeTool ) {
            stderr.writefln("ANTLR Runtime version %s used for parser compilation does not match the current runtime version %s",
                              compileTimeVersion, runtimeVersion);
        }

    }

    /**
     * Gets the major and minor version numbers from a version string. For
     * details about the syntax of the input {@code version}.
     * E.g., from x.y.z return x.y.
     *
     *  @param version The complete version string.
     *  @return A string of the form <em>major</em>.<em>minor</em> containing
     *  only the major and minor components of the version string.
     */
    public static string getMajorMinorVersion(string antlr_version)
    {
        size_t firstDot = antlr_version.indexOf('.');
        size_t secondDot = firstDot >= 0 ? antlr_version.indexOf('.', firstDot + 1) : -1;
        size_t firstDash = antlr_version.indexOf('-');
        size_t referenceLength = antlr_version.length;
        if (secondDot >= 0) {
            referenceLength = min(referenceLength, secondDot);
        }

        if (firstDash >= 0) {
            referenceLength = min(referenceLength, firstDash);
        }

        return antlr_version[0..referenceLength];
    }

}

version(unittest) {

    import dshould : be, equal, not, should;
    import std.typecons : tuple;
    import unit_threaded;

    class Test {

        @Tags("mt", "reg")
        @("compareMetaDataVersion")
        unittest {
            "4.8".should.equal(RuntimeMetaData.getMajorMinorVersion(RuntimeMetaData.VERSION));
            RuntimeMetaData.checkVersion("4.8", "4.8.0");
        }
    }
}