/*
 * Copyright 2009
 * DedaSys LLC - http://www.dedasys.com
 *
 * Author: David N. Welton 
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.hecl.files;

import java.io.IOException;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.io.BufferedReader;

import java.io.DataInputStream;

import org.hecl.HeclException;
import org.hecl.Interp;
import org.hecl.Thing;

/**
 * The HeclFileUtils class provides several utility
 * functions that are used both by FileCmds, and elsewhere in Hecl.
 *
 * @author David N. Welton
 * @version 1.0
 */
public class HeclFileUtils {

    /**
     * readFile takes a filename and returns the file's
     * contents as a Thing.
     *
     * @param filename a String value
     * @return a Thing value
     * @exception HeclException if an error occurs
     * @exception IOException if an error occurs
     */
    public static Thing readFile(String filename) throws HeclException, IOException {
        //System.out.println("readFile " + filename); // debug
	File realfn = new File(filename).getAbsoluteFile();
        // Change by av. The readFileFromDis method seems not read UTF-8 encoded files properly on Windows platform.
	//return readFileFromDis(new DataInputStream(new FileInputStream(realfn)));
        InputStreamReader eingabestrom;
        eingabestrom = new InputStreamReader(new FileInputStream(realfn), "UTF-8");
        BufferedReader eingabe = new BufferedReader(eingabestrom);
        StringBuffer sb = new StringBuffer(1024);
        String zeile;
        boolean isEOF = false;
        do {
            zeile = eingabe.readLine();
            if (zeile != null) {
                sb.append(zeile);
                sb.append("\n");
            }
            else isEOF = true;
        } while (isEOF == false);
        eingabe.close();
        eingabestrom.close();
        return new Thing(sb.toString());
    }

    /**
     * readFileFromDis, given a DataInputStream, reads
     * from the stream until no more can be read, and returns the
     * results as a Thing.
     *
     * @param dis a DataInputStream value
     * @return a Thing value
     * @exception IOException if an error occurs
     */
    public static Thing readFileFromDis(DataInputStream dis) throws IOException {
        //System.out.println("readFileFromDis " + dis.toString()); // debug
	int bsize = 1024;
	byte[] buf = new byte[bsize];
	byte[] acc = null;
	byte[] oldacc = null;
	int len = 0;
	int pos = 0;
	int i = 1;
	while ((len = dis.read(buf)) > -1) {
	    oldacc = acc;
	    acc = new byte[i * bsize];
	    if (oldacc != null) {
		System.arraycopy(oldacc, 0, acc, 0, (i-1) * bsize);
	    }
	    System.arraycopy(buf, 0, acc, pos, len);
	    pos += len;
	    i ++;
	}
	return new Thing(new String(acc, 0, pos));
    }

    /**
     * The sourceFile method takes a file name.  It opens
     * that file, reads the contents, and evaluates them with the
     * provided interpreter.
     *
     * @param interp an Interp value
     * @param filename a String value
     * @exception HeclException if an error occurs
     */
    public static void sourceFile(Interp interp, String filename)
	throws HeclException {

	interp.currentFile = new Thing(filename);

	try {
	    interp.eval(readFile(filename));
	} catch (HeclException he) {
	    throw he;
	} catch (Exception e) {
	    throw new HeclException("Error while running '" + filename + "': " + e.toString());
	}
    }
}