package luan.modules;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.Set;
import java.util.HashSet;
import luan.Luan;
import luan.LuanState;
import luan.LuanTable;
import luan.LuanFunction;
import luan.LuanJavaFunction;
import luan.LuanElement;
import luan.LuanException;


public final class PackageLuan {

	public static final LuanFunction requireFn;
	static {
		try {
			requireFn = new LuanJavaFunction(PackageLuan.class.getMethod("require",LuanState.class,String.class),null);
		} catch(NoSuchMethodException e) {
			throw new RuntimeException(e);
		}
	}

	public static LuanTable loaded(LuanState luan) {
		LuanTable tbl = (LuanTable)luan.registry().get("Package.loaded");
		if( tbl == null ) {
			tbl = Luan.newTable();
			luan.registry().put("Package.loaded",tbl);
		}
		return tbl;
	}

	public static Object require(LuanState luan,String modName) throws LuanException {
		Object mod = load(luan,modName);
		if( mod==null )
			throw luan.exception( "module '"+modName+"' not found" );
		return mod;
	}

	public static Object load(LuanState luan,String modName) throws LuanException {
		LuanTable loaded = loaded(luan);
		Object mod = loaded.get(modName);
		if( mod == null ) {
			if( modName.startsWith("java:") ) {
				mod = JavaLuan.load(luan,modName.substring(5));
				if( mod != null )
					loaded.put(modName,mod);
			} else {
				String src = read(luan,modName+".luan");
				if( src == null )
					return null;
				LuanTable env = Luan.newTable();
				LuanFunction loader = BasicLuan.load(luan,src,modName,env,false);
				loaded.put(modName,env);
				@SuppressWarnings("unchecked")
				Set<String> loading = (Set<String>)luan.registry().get("Package.loading");
				boolean top = loading==null;
				if(top) {
					loading = new HashSet<String>();
					luan.registry().put("Package.loading",loading);
				}
				loading.add(modName);
				boolean ok = false;
				try {
					mod = Luan.first(
						luan.call(loader,"<require \""+modName+"\">",new Object[]{modName})
					);
					ok = true;
				} finally {
					if( !ok ) {
						if(top) {
							for( String mn : loading ) {
								loaded.put(mn,null);
							}
						} else {
							loaded.put(modName,null);
						}
					}
					if(top)
						luan.registry().put("Package.loading",null);
				}
				if( mod != null )
					loaded.put(modName,mod);
				else
					mod = env;
			}
		}
		return mod;
	}

	static String read(LuanState luan,String uri) throws LuanException {
		LuanTable t = IoLuan.Uri(luan,uri);
		if( t == null )
			return null;
		LuanFunction existsFn = (LuanFunction)t.get("exists");
		boolean exists = (Boolean)Luan.first(luan.call(existsFn));
		if( !exists )
			return null;
		LuanFunction reader = (LuanFunction)t.get("read_text");
		return (String)Luan.first(luan.call(reader));
	}

}