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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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package com.sun.tools.javac.code;

import com.sun.tools.javac.code.Lint.LintCategory;
import com.sun.tools.javac.code.Source.Feature;
import com.sun.tools.javac.jvm.Target;
import com.sun.tools.javac.resources.CompilerProperties.Errors;
import com.sun.tools.javac.resources.CompilerProperties.Warnings;
import com.sun.tools.javac.util.Assert;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.JCDiagnostic.DiagnosticPosition;
import com.sun.tools.javac.util.JCDiagnostic.Error;
import com.sun.tools.javac.util.JCDiagnostic.SimpleDiagnosticPosition;
import com.sun.tools.javac.util.JCDiagnostic.Warning;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.MandatoryWarningHandler;
import com.sun.tools.javac.util.Options;

import javax.tools.JavaFileObject;
import java.util.HashMap;
import java.util.Map;

import static com.sun.tools.javac.main.Option.PREVIEW;

Helper class to handle preview language features. This class maps certain language features (see Feature into 'preview' features; the mapping is completely ad-hoc, so as to allow for maximum flexibility, which allows to migrate preview feature into supported features with ease. This class acts as a centralized point against which usages of preview features are reported by clients (e.g. other javac classes). Internally, this class collects all such usages and generates diagnostics to inform the user of such usages. Such diagnostics can be enabled using the LintCategory.PREVIEW lint category, and are suppressible by usual means. /**
 * Helper class to handle preview language features. This class maps certain language features
 * (see {@link Feature} into 'preview' features; the mapping is completely ad-hoc, so as to allow
 * for maximum flexibility, which allows to migrate preview feature into supported features with ease.
 *
 * This class acts as a centralized point against which usages of preview features are reported by
 * clients (e.g. other javac classes). Internally, this class collects all such usages and generates
 * diagnostics to inform the user of such usages. Such diagnostics can be enabled using the
 * {@link LintCategory#PREVIEW} lint category, and are suppressible by usual means.
 */
public class Preview {

    
flag: are preview features enabled /** flag: are preview features enabled */
    private final boolean enabled;

    
the diag handler to manage preview feature usage diagnostics /** the diag handler to manage preview feature usage diagnostics */
    private final MandatoryWarningHandler previewHandler;

    
test flag: should all features be considered as preview features? /** test flag: should all features be considered as preview features? */
    private final boolean forcePreview;

    
a mapping from classfile numbers to Java SE versions /** a mapping from classfile numbers to Java SE versions */
    private final Map<Integer, Source> majorVersionToSource;


    private final Lint lint;
    private final Log log;

    private static final Context.Key<Preview> previewKey = new Context.Key<>();

    public static Preview instance(Context context) {
        Preview instance = context.get(previewKey);
        if (instance == null) {
            instance = new Preview(context);
        }
        return instance;
    }

    Preview(Context context) {
        context.put(previewKey, this);
        Options options = Options.instance(context);
        enabled = options.isSet(PREVIEW);
        log = Log.instance(context);
        lint = Lint.instance(context);
        this.previewHandler =
                new MandatoryWarningHandler(log, lint.isEnabled(LintCategory.PREVIEW), true, "preview", LintCategory.PREVIEW);
        forcePreview = options.isSet("forcePreview");
        majorVersionToSource = initMajorVersionToSourceMap();
    }

    private Map<Integer, Source> initMajorVersionToSourceMap() {
        Map<Integer, Source> majorVersionToSource = new HashMap<>();
        for (Target t : Target.values()) {
            int major = t.majorVersion;
            Source source = Source.lookup(t.name);
            if (source != null) {
                majorVersionToSource.put(major, source);
            }
        }
        return majorVersionToSource;
   }

    
Report usage of a preview feature. Usages reported through this method will affect the
set of sourcefiles with dependencies on preview features.
Params:
pos – the position at which the preview feature was used.
feature – the preview feature used./**
     * Report usage of a preview feature. Usages reported through this method will affect the
     * set of sourcefiles with dependencies on preview features.
     * @param pos the position at which the preview feature was used.
     * @param feature the preview feature used.
     */
    public void warnPreview(int pos, Feature feature) {
        warnPreview(new SimpleDiagnosticPosition(pos), feature);
    }

    
Report usage of a preview feature. Usages reported through this method will affect the
set of sourcefiles with dependencies on preview features.
Params:
pos – the position at which the preview feature was used.
feature – the preview feature used./**
     * Report usage of a preview feature. Usages reported through this method will affect the
     * set of sourcefiles with dependencies on preview features.
     * @param pos the position at which the preview feature was used.
     * @param feature the preview feature used.
     */
    public void warnPreview(DiagnosticPosition pos, Feature feature) {
        Assert.check(isEnabled());
        Assert.check(isPreview(feature));
        if (!lint.isSuppressed(LintCategory.PREVIEW)) {
            previewHandler.report(pos, feature.isPlural() ?
                    Warnings.PreviewFeatureUsePlural(feature.nameFragment()) :
                    Warnings.PreviewFeatureUse(feature.nameFragment()));
        }
    }

    
Report usage of a preview feature in classfile.
Params:
classfile – the name of the classfile with preview features enabled
majorVersion – the major version found in the classfile./**
     * Report usage of a preview feature in classfile.
     * @param classfile the name of the classfile with preview features enabled
     * @param majorVersion the major version found in the classfile.
     */
    public void warnPreview(JavaFileObject classfile, int majorVersion) {
        Assert.check(isEnabled());
        if (!lint.isSuppressed(LintCategory.PREVIEW)) {
            previewHandler.report(null,
                    Warnings.PreviewFeatureUseClassfile(classfile, majorVersionToSource.get(majorVersion).name));
        }
    }

    public void reportPreviewWarning(DiagnosticPosition pos, Warning warnKey) {
        previewHandler.report(pos, warnKey);
    }

    
Are preview features enabled?
Returns:
true, if preview features are enabled./**
     * Are preview features enabled?
     * @return true, if preview features are enabled.
     */
    public boolean isEnabled() {
        return enabled;
    }

    
Is given feature a preview feature?
Params:
feature – the feature to be tested.
Returns:
true, if given feature is a preview feature./**
     * Is given feature a preview feature?
     * @param feature the feature to be tested.
     * @return true, if given feature is a preview feature.
     */
    public boolean isPreview(Feature feature) {
        if (feature == Feature.SEALED_CLASSES)
            return true;
        //Note: this is a backdoor which allows to optionally treat all features as 'preview' (for testing).
        //When real preview features will be added, this method can be implemented to return 'true'
        //for those selected features, and 'false' for all the others.
        return forcePreview;
    }

    
Generate an error key which captures the fact that a given preview feature could not be used
due to the preview feature support being disabled.
Params:
feature – the feature for which the diagnostic has to be generated.
Returns:
the diagnostic./**
     * Generate an error key which captures the fact that a given preview feature could not be used
     * due to the preview feature support being disabled.
     * @param feature the feature for which the diagnostic has to be generated.
     * @return the diagnostic.
     */
    public Error disabledError(Feature feature) {
        Assert.check(!isEnabled());
        return feature.isPlural() ?
                Errors.PreviewFeatureDisabledPlural(feature.nameFragment()) :
                Errors.PreviewFeatureDisabled(feature.nameFragment());
    }

    
Generate an error key which captures the fact that a preview classfile cannot be loaded
due to the preview feature support being disabled.
Params:
classfile – the name of the classfile with preview features enabled
majorVersion – the major version found in the classfile./**
     * Generate an error key which captures the fact that a preview classfile cannot be loaded
     * due to the preview feature support being disabled.
     * @param classfile the name of the classfile with preview features enabled
     * @param majorVersion the major version found in the classfile.
     */
    public Error disabledError(JavaFileObject classfile, int majorVersion) {
        Assert.check(!isEnabled());
        return Errors.PreviewFeatureDisabledClassfile(classfile, majorVersionToSource.get(majorVersion).name);
    }

    
Report any deferred diagnostics.
/**
     * Report any deferred diagnostics.
     */
    public void reportDeferredDiagnostics() {
        previewHandler.reportDeferredDiagnostic();
    }

    public void clear() {
        previewHandler.clear();
    }

}