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 java.util;

import cc.squirreljme.jvm.mle.JarPackageShelf;
import cc.squirreljme.jvm.mle.brackets.JarPackageBracket;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
 * Iterator over a fresh search pouring into the cache.
 *
 * @param <S> The class type.
 * @since 2018/12/06
 */
final class __ServiceLoaderFreshIterator__<S>
    implements Iterator<S>
{
    /** The search class. */
    private final Class<S> _search;
    
    /** The cache to put in. */
    private final __ServiceLoaderCache__<S> _cache;
    
    /** Temporary cache building. */
    private final List<Object> _cacheBuild =
        new ArrayList<>();
    
    /** JARs left to parse. */
    private final Queue<JarPackageBracket> _jarsLeft =
        new LinkedList<>();
    
    /** Classes left to create and scan. */
    private final Queue<String> _classes =
        new LinkedList<>();
    
    /** The next service to run. */
    private S _next;
    
    /** Is this finished? */
    private boolean _finished;
    
    /**
     * Initializes the iterator for fresh service lookup.
     *
     * @param __s The search class.
     * @param __c The cache class.
     * @throws NullPointerException On null arguments.
     * @since 2018/12/06
     */
    __ServiceLoaderFreshIterator__(Class<S> __s, __ServiceLoaderCache__<S> __c)
        throws NullPointerException
    {
        if (__s == null || __c == null)
            throw new NullPointerException("NARG");
        
        this._search = __s;
        this._cache = __c;
        
        // All of the suites to look within
        this._jarsLeft.addAll(
            Arrays.<JarPackageBracket>asList(JarPackageShelf.classPath()));
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/12/06
     */
    @Override
    public final boolean hasNext()
    {
        // If already finished, nothing can be done
        if (this._finished)
            return false;
        
        // Already cached?
        if (this._next != null)
            return true;
        
        // Loops until an element was found
        for (Queue<String> classes = this._classes;;)
        {
            // If there are no classes, consume the next one
            if (classes.isEmpty())
            {
                this.__consumeNextJar();
                
                // Early out when nothing is left
                if (this._finished)
                    return false;
            }
            
            // If there is an entry in the class list, try to load that
            // class
            String maybe = classes.poll();
            if (maybe != null)
            {
                // Try to load this class
                try
                {
                    // If this fails an exception is thrown
                    Class<?> cl = Class.forName(maybe);
                    
                    // Try to create a new instance since this is new,
                    // any exceptions thrown cause errors
                    Object rv = cl.newInstance();
                    
                    // Cache this instance for later
                    this._cacheBuild.add(rv);
                    
                    // Cast this class
                    this._next = this._search.cast(rv);
                    return true;
                }
                
                /* {@squirreljme.error ZZ30 Could not load the service
                class.} */
                catch (ClassCastException|IllegalAccessException|
                    InstantiationException|ClassNotFoundException e)
                {
                    throw new ServiceConfigurationError("ZZ30", e);
                }
            }
        }
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/12/06
     */
    @Override
    public final S next()
    {
        // Cache
        if (!this.hasNext())
            throw new NoSuchElementException("NSEE");
        
        // Return the cached element
        S rv = this._next;
        this._next = null;
        return rv;
    }
    
    /**
     * {@inheritDoc}
     * @since 2018/12/06
     */
    @Override
    public final void remove()
    {
        throw new UnsupportedOperationException("RORO");
    }
    
    /**
     * Consume the next JAR and loads the classes.
     *
     * @since 2020/06/18
     */
    private void __consumeNextJar()
    {
        // If there are no JARs left, then just stop processing
        JarPackageBracket nextJar = this._jarsLeft.poll();
        if (nextJar == null)
        {
            // Mark as done
            this._finished = true;
            
            // Push these services into the cache
            List<Object> cb = this._cacheBuild;
            this._cache._cache = cb.<Object>toArray(
                new Object[cb.size()]);
            
            // Clear from this fresh iterator
            cb.clear();
            
            return;
        }
        
        // Load the Jar otherwise
        this.__loadJar(nextJar);
    }
    
    /**
     * Loads the specified JAR.
     *
     * @param __jar The Jar to load.
     * @throws NullPointerException On null arguments.
     * @since 2020/06/18
     */
    @SuppressWarnings("UnnecessaryLocalVariable")
    private void __loadJar(JarPackageBracket __jar)
        throws NullPointerException
    {
        if (__jar == null)
            throw new NullPointerException("NARG");
        
        // Load the services for the given Jar
        try (InputStream in = JarPackageShelf.openResource(__jar,
            "META-INF/services/" + this._search.getName()))
        {
            // If this JAR has no services, ignore it
            if (in == null)
                return;
            
            // Read by line
            Queue<String> classes = this._classes;
            try (BufferedReader br = new BufferedReader(
                new InputStreamReader(in, "utf-8")))
            {
                // Read in every service line
                for (;;)
                {
                    // Stop on EOF
                    String ln = br.readLine();
                    if (ln == null)
                        break;
                    
                    // Trim the line to remove useless spaces
                    ln = ln.trim();
                    
                    // Ignore blank lines
                    if (ln.isEmpty())
                        continue;
                    
                    // Ignore comments
                    if (ln.charAt(0) == '#')
                        continue;
                    
                    // Add otherwise
                    classes.add(ln);
                }
            }
        }
        
        /* {@squirreljme.error ZZ31 Could not read the services
        list.} */
        catch (IOException e)
        {
            throw new ServiceConfigurationError("ZZ31", e);
        }
    }
}