package luan.lib;

import java.io.File;
import java.util.List;
import java.util.ArrayList;
import luan.Luan;
import luan.LuanState;
import luan.LuanTable;
import luan.LuanFunction;
import luan.LuanJavaFunction;
import luan.LuanElement;
import luan.LuanException;


public final class PackageLib {

	public static final String NAME = "package";

	public static final LuanFunction LOADER = new LuanFunction() {
		public Object[] call(LuanState luan,Object[] args) throws LuanException {
			LuanTable global = luan.global;
			LuanTable module = new LuanTable();
			List<Object> searchers = new ArrayList<Object>();
			global.put(NAME,module);
			module.put("loaded",luan.loaded);
			module.put("preload",luan.preload);
			module.put("path","?.lua");
			try {
				add( global, "require", LuanState.class, String.class );
				add( module, "search_path", String.class, String.class );
				searchers.add( new LuanJavaFunction(PackageLib.class.getMethod("preloadSearcher",LuanState.class,String.class),null) );
				searchers.add( new LuanJavaFunction(PackageLib.class.getMethod("fileSearcher",LuanState.class,String.class),null) );
			} catch(NoSuchMethodException e) {
				throw new RuntimeException(e);
			}
			module.put("searchers",new LuanTable(searchers));
			return LuanFunction.EMPTY_RTN;
		}
	};

	private static void add(LuanTable t,String method,Class<?>... parameterTypes) throws NoSuchMethodException {
		t.put( method, new LuanJavaFunction(PackageLib.class.getMethod(method,parameterTypes),null) );
	}

	public static Object require(LuanState luan,String modName) throws LuanException {
		LuanTable module = (LuanTable)luan.global.get(NAME);
		Object mod = luan.loaded.get(modName);
		if( mod == null ) {
			LuanTable searchers = (LuanTable)module.get("searchers");
			for( Object s : searchers.asList() ) {
				LuanFunction searcher = (LuanFunction)s;
				Object[] a = luan.call(searcher,LuanElement.JAVA,"searcher",modName);
				if( a.length >= 1 && a[0] instanceof LuanFunction ) {
					LuanFunction loader = (LuanFunction)a[0];
					Object extra = a.length >= 2 ? a[1] : null;
					mod = luan.load(loader,modName,extra);
				}
			}
			if( mod == null )
				throw new LuanException( luan, LuanElement.JAVA, "module '"+modName+"' not found" );
		}
		return mod;
	}

	public static String search_path(String NAME,String path) {
		for( String s : path.split(";") ) {
			String file = s.replaceAll("\\?",NAME);
			if( new File(file).exists() )
				return file;
		}
		return null;
	}

	private static final LuanFunction fileLoader = new LuanFunction() {
		public Object[] call(LuanState luan,Object[] args) throws LuanException {
			return BasicLib.do_file(luan,(String)args[1]);
		}
	};

	public static Object[] fileSearcher(LuanState luan,String modName) {
		LuanTable module = (LuanTable)luan.global.get(NAME);
		String path = (String)module.get("path");
		String file = search_path(modName,path);
		return file==null ? LuanFunction.EMPTY_RTN : new Object[]{fileLoader,file};
	}

	public static Object preloadSearcher(LuanState luan,String modName) {
		return luan.preload.get(modName);
	}
		
}