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package io.baltoro.ep;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;
import java.nio.CharBuffer;
import java.util.HashMap;
import java.util.Map;

import javax.tools.FileObject;
import javax.tools.ForwardingJavaFileManager;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;
import javax.tools.JavaFileObject.Kind;
import javax.tools.SimpleJavaFileObject;

/**
 * JavaFileManager that keeps compiled .class bytes in memory.
 */
@SuppressWarnings("unchecked")
final class EPFileManager extends ForwardingJavaFileManager
{

	/** Java source file extension. */
	private final static String EXT = ".java";

	private Map classBytes;

	public EPFileManager(JavaFileManager fileManager)
	{
		super(fileManager);
		classBytes = new HashMap<>();
	}

	public Map getClassBytes()
	{
		return classBytes;
	}

	public void close() throws IOException
	{
		classBytes = null;
	}

	public void flush() throws IOException
	{
	}

	/**
	 * A file object used to represent Java source coming from a string.
	 */
	private static class StringInputBuffer extends SimpleJavaFileObject
	{
		final String code;

		StringInputBuffer(String fileName, String code)
		{
			super(toURI(fileName), Kind.SOURCE);
			this.code = code;
		}

		public CharBuffer getCharContent(boolean ignoreEncodingErrors)
		{
			return CharBuffer.wrap(code);
		}
	}

	/**
	 * A file object that stores Java bytecode into the classBytes map.
	 */
	private class ClassOutputBuffer extends SimpleJavaFileObject
	{
		private String name;

		ClassOutputBuffer(String name)
		{
			super(toURI(name), Kind.CLASS);
			this.name = name;
		}

		public OutputStream openOutputStream()
		{
			return new FilterOutputStream(new ByteArrayOutputStream())
			{
				public void close() throws IOException
				{
					out.close();
					ByteArrayOutputStream bos = (ByteArrayOutputStream) out;
					classBytes.put(name, bos.toByteArray());
				}
			};
		}
	}

	public JavaFileObject getJavaFileForOutput(JavaFileManager.Location location, String className, Kind kind,
			FileObject sibling) throws IOException
	{
		if (kind == Kind.CLASS)
		{
			return new ClassOutputBuffer(className);
		} else
		{
			return super.getJavaFileForOutput(location, className, kind, sibling);
		}
	}

	static JavaFileObject makeStringSource(String fileName, String code)
	{
		return new StringInputBuffer(fileName, code);
	}

	static URI toURI(String name)
	{
		File file = new File(name);
		if (file.exists())
		{
			return file.toURI();
		} else
		{
			try
			{
				final StringBuilder newUri = new StringBuilder();
				newUri.append("mfm:///");
				newUri.append(name.replace('.', '/'));
				if (name.endsWith(EXT))
					newUri.replace(newUri.length() - EXT.length(), newUri.length(), EXT);
				return URI.create(newUri.toString());
			} catch (Exception exp)
			{
				return URI.create("mfm:///com/sun/script/java/java_source");
			}
		}
	}
}