SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package cc.squirreljme.vm;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.file.Path;
import java.util.LinkedList;
import java.util.List;

/**
 * This is a class library resource which is based on class resources.
 *
 * Resource lookup is done on the {@link #actingclass}, all resource
 * accesses are done by having a prefix that is before all accesses of
 * entires. The prefix is so that multiple virtual JARs may exist within a
 * single JAR.
 *
 * The list of resources in the JAR exists in:
 * {@code ${prefix}/META-INF/squirreljme/resources.list}.
 *
 * @since 2018/11/14
 */
public final class ResourceBasedClassLibrary
    implements VMClassLibrary
{
    /** The class to get resources from. */
    protected final Class<?> actingclass;
    
    /** The prefix for entries. */
    protected final String prefix;
    
    /** The name of this library. */
    protected final String name;
    
    /** Resources in this class. */
    private String[] _resources;
    
    /**
     * Initializes the resource based class library.
     *
     * @param __act The class to act on.
     * @param __pre The prefix for lookup.
     * @param __name The name of the library.
     * @throws NullPointerException On null arguments.
     * @since 2018/11/15
     */
    public ResourceBasedClassLibrary(Class<?> __act, String __pre,
        String __name)
        throws NullPointerException
    {
        if (__act == null || __pre == null || __name == null)
            throw new NullPointerException("NARG");
        
        this.actingclass = __act;
        this.prefix = __pre;
        this.name = __name;
    }
    
    /**
     * {@inheritDoc}
     * @since 2019/04/21
     */
    @Override
    public final String[] listResources()
    {
        // Pre-cached?
        String[] rv = this._resources;
        if (rv != null)
            return rv.clone();
        
        // Load in the resource list
        List<String> list = new LinkedList<>();
        try (BufferedReader br = new BufferedReader(new InputStreamReader(
            this.resourceAsStream("META-INF/squirreljme/resources.list"),
            "utf-8")))
        {
            String ln;
            while ((ln = br.readLine()) != null)
            {
                // Blank lines are not resources
                if (ln.isEmpty())
                    continue;
                
                // Add otherwise
                list.add(ln);
            }
        }
        
        /* {@squirreljme.error AK09 Could not load resource list.} */
        catch (IOException e)
        {
            throw new RuntimeException("AK09");
        }
        
        // Cache it and return
        this._resources = (rv = list.<String>toArray(new String[list.size()]));
        return rv.clone();
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/11/14
     */
    @Override
    public final String name()
    {
        return this.name;
    }
    
    /**
     * {@inheritDoc}
     * @since 2021/06/13
     */
    @Override
    public Path path()
    {
        return null;
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/11/14
     */
    @Override
    public final InputStream resourceAsStream(String __rc)
        throws IOException, NullPointerException
    {
        if (__rc == null)
            throw new NullPointerException("NARG");
        
        return this.actingclass.getResourceAsStream(
            this.prefix + __rc);
    }
}