package luan.impl;

import java.io.OutputStream;
import java.io.ByteArrayOutputStream;
import java.io.StringWriter;
import java.io.IOException;
import java.net.URI;
import java.util.Collections;
import javax.tools.FileObject;
import javax.tools.JavaFileObject;
import javax.tools.SimpleJavaFileObject;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import javax.tools.JavaFileManager;
import javax.tools.StandardJavaFileManager;
import javax.tools.ForwardingJavaFileManager;


public final class LuanJavaCompiler {
	private LuanJavaCompiler() {}  // never

	public static Class compile(final String className,final String sourceName,final String code) throws ClassNotFoundException {
		final int len = sourceName.length();
		StringBuilder sb = new StringBuilder(sourceName);
		for( int i=0; i<len; i++ )
			sb.setCharAt(i,'$');
		JavaFileObject sourceFile = new SimpleJavaFileObject(URI.create(sb.toString()),JavaFileObject.Kind.SOURCE) {
			@Override public CharSequence getCharContent(boolean ignoreEncodingErrors) {
				return code;
			}
			@Override public String getName() {
				return sourceName;
			}
			@Override public boolean isNameCompatible(String simpleName,JavaFileObject.Kind kind) {
				return true;
			}
		};
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		JavaFileObject classFile = new SimpleJavaFileObject(URI.create("whatever"),JavaFileObject.Kind.CLASS) {
			@Override public OutputStream openOutputStream() {
				return baos;
			}
		};
		JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
		StandardJavaFileManager sjfm = compiler.getStandardFileManager(null,null,null);
		ForwardingJavaFileManager fjfm = new ForwardingJavaFileManager(sjfm) {
			@Override public JavaFileObject getJavaFileForOutput(JavaFileManager.Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException {
				return classFile;
			}
		};
		StringWriter out = new StringWriter();
		boolean b = compiler.getTask(out, fjfm, null, null, null, Collections.singletonList(sourceFile)).call();
		if( !b )
			throw new RuntimeException("\n"+out+"\ncode:\n"+code+"\n");
		byte[] byteCode = baos.toByteArray();
		int max = byteCode.length-len-3;
		outer:
		for( int i=0; true; i++ ) {
			if( i > max )
				throw new RuntimeException("len="+len);
			if( byteCode[i]==1 && (byteCode[i+1] << 8 | 0xFF & byteCode[i+2]) == len ) {
				for( int j=i+3; j<i+3+len; j++ ) {
					if( byteCode[j] != '$' )
						continue outer;
				}
				System.arraycopy(sourceName.getBytes(),0,byteCode,i+3,len);
				break;
			}
		}
		ClassLoader cl = new ClassLoader() {
			@Override protected Class<?> findClass(String name) throws ClassNotFoundException {
				if( name.equals(className) ) {
					return defineClass(name, byteCode, 0, byteCode.length);
				}
				return super.findClass(name);
			}
		};
		return cl.loadClass(className);
	}
}