/*

   Derby - Class org.apache.derbyTesting.functionTests.harness.SimpleDiff

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You 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.

 */

//SimpleDiff.java
package org.apache.derbyTesting.functionTests.harness;

import java.io.IOException;
import java.io.BufferedInputStream;
import java.util.Vector;
import java.io.File;
import java.io.PrintWriter;
import java.io.BufferedReader;
import java.io.FileReader;

public class SimpleDiff
{

    PrintWriter pw;

    boolean debugOn = Boolean.getBoolean("simplediff.debug");
    int debugLevel = 1;

    boolean diffsFound = true;

    int lookAhead = 20;

    public void debug(int level, String msg)
    {
        if (debugLevel >= level)
        {
            debug(msg);
        }
    }
    public void debug(String msg)
    {
        if (debugOn)
        {
            System.out.println("DEBUG: " + msg);
        }
    }

    int lineCount(String file) throws IOException
    {
        BufferedReader input = new BufferedReader(new FileReader(file));
        int count = 0;
        String aLine = input.readLine();
        while (aLine != null)
        {
            count++;
            aLine = input.readLine();
        }
        input.close();
        return count;
    }


    public String[] readFile(BufferedReader input) throws IOException
    {

        Vector<String> vec = new Vector<String>();

        String aLine = "";
        //int count = 0;
        aLine = input.readLine();
        while (aLine != null)
        {
            vec.addElement(aLine);
            //count++;
            aLine = input.readLine();
        }
        input.close();

        String rV[] = new String[vec.size()];
        //debug(2, ""+count + " lines in " + filename);
        debug(2, ""+vec.size() + " lines in input");
        vec.copyInto(rV);

        return rV;
    }

    public void printFile(String file[])
    {
        for (int i = 0; i < file.length; i++)
        {
            pw.println(i + ": " + file[i]);
            System.out.println(i + ": " + file[i]);
        }
    }

    public static String usage = "java SimpleDiff <file1> <file2>";

    /**
        @param file1 Name of first file to be read
        @param file2 Name of file with which to compare
        @return String array of file contents
        @exception IOException thrown by underlying calls
            to the file system
    */

    public String[] diffFiles(  DiffBuffer file1,
                                DiffBuffer file2)
                                throws IOException
    {

        int currentLine1 = 0;
        int currentLine2 = 0;
        Vector<String> returnVec = new Vector<String>();

        while ( file1.isValidOffset(currentLine1) &&
                file2.isValidOffset(currentLine2))
        {
            String f1 = file1.lineAt(currentLine1);
            String f2 = file2.lineAt(currentLine2);

            if (f1.equals(f2))
            {
                debug(1, currentLine1 + ": match");
                currentLine1++;
                currentLine2++;
                file1.setLowWater(currentLine1);
                file2.setLowWater(currentLine2);
            }
            else
            {
                boolean foundMatch = false;
                int checkLine2 = currentLine2;
                int checkCount = 1;
//                while ( (currentLine2 + checkCount) < (file2Length - 1) &&
                while ( file2.isValidOffset(currentLine2 + checkCount) &&
                        checkCount < lookAhead)
                {
                    debug(1, "currentLine1 " + currentLine1 + "  currentLine2 " + (currentLine2 +checkCount));
                    debug(1, "about to reference file2[" + (currentLine2 + checkCount) + "]");
                    f2 = file2.lineAt(currentLine2 + checkCount);
                    debug(2, "did");
                    if (f1.equals(f2))
                    {
                        foundMatch = true;
                        if (checkCount > 1)
                        {
                            returnVec.addElement(currentLine1 + "a" + (currentLine2 + 1) + "," + (currentLine2 + checkCount));
                        }
                        else
                        {
                            returnVec.addElement(currentLine1 + "a" + (currentLine2 + 1));
                        }

                        for (int j = 0; j < checkCount; j++)
                        {
                            returnVec.addElement("> " +
                                  file2.lineAt(currentLine2 + j) );
                        }
                        currentLine2 = currentLine2 + checkCount;
                        checkCount = 0;

						// This break statement was commented out, which
						// caused problems in the diff output.  I don't
						// know why it was commented out, and uncommenting
						// it fixed the problem.
						//
						//			-	Jeff Lichtman
						//				March 24, 1999
                        break;
                    }
                    checkCount ++;
                }
                if (!foundMatch && file2.isValidOffset(currentLine2))
                {
                    int checkLine1 = currentLine1;
                    checkCount = 1;
                    f2 = file2.lineAt(currentLine2);
                    while ( file1.isValidOffset(currentLine1 + checkCount) &&
                            checkCount < lookAhead)
                    {
                        debug(1, "currentLine2 " + currentLine2 + "  currentLine1 " + (currentLine1 + checkCount));
                        f1 = file1.lineAt(currentLine1 + checkCount);
                        if ( f2.equals(f1))
                        {
                            foundMatch = true;
                            if (checkCount > 1)
                            {
                                returnVec.addElement((currentLine1 + 1) + "," + (currentLine1 + checkCount) + "d" + currentLine2);
                            }
                            else
                            {
                                returnVec.addElement((currentLine1 + 1) + "d" + currentLine2);
                            }

                            for (int j = 0; j < checkCount; j++)
                            {
                                returnVec.addElement("< " +
                                      file1.lineAt(currentLine1 + j) );

                            }
                            currentLine1 = currentLine1 + checkCount;
                            checkCount = 0;
                            debug(1, "continuing");
                            break;
                        }
                        checkCount ++;
                    }

                }
                if (!foundMatch)
                {
                    debug(1, currentLine1 + ": NOMATCH");
                    returnVec.addElement((currentLine1 + 1) +" del");// + (currentLine2 + 1));
                    returnVec.addElement("< " + file1.lineAt(currentLine1));
                    currentLine1++;
                }
                else
                {
                    currentLine1++;
                    currentLine2++;
                    file1.setLowWater(currentLine1);
                    file2.setLowWater(currentLine2);
                }
            }
        }

        if (file1.isValidOffset(currentLine1))
        {
            returnVec.addElement((currentLine2) + " del");
            for (int i = currentLine1; file1.isValidOffset(i); i++)
            {
                returnVec.addElement("< " + file1.lineAt(i));
            }
        }
        if (file2.isValidOffset(currentLine2))
        {
            returnVec.addElement((currentLine1) + " add");
            for (int i = currentLine2; file2.isValidOffset(i); i++)
            {
                returnVec.addElement("> " + file2.lineAt(i));
            }
        }

        file1.close();
        file2.close();

        if (returnVec.isEmpty())
        {
            return null;
        }


        String [] returnArray = new String[returnVec.size()];
        returnVec.copyInto(returnArray);
        return returnArray;


    }

    private void reportMemory()
    {
        reportMemory(null);
    }

    private void reportMemory(String header)
    {
        if (header != null)
        {
            System.out.println(header);
        }
        long free = Runtime.getRuntime().freeMemory();
        long total = Runtime.getRuntime().totalMemory();

        System.out.println("total:         " + total );
        System.out.println("free:          " + free );
        System.out.println("used:          " + (total - free));
        System.gc();
        System.out.println("used: <postgc> " + (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()));
        System.out.println("  ");
    }

    public boolean doWork(BufferedReader in1, BufferedReader in2, PrintWriter localPW) throws IOException
    {
        this.pw=(localPW==null?new PrintWriter(System.out):localPW);
        try
        {
            DiffBuffer db1 = new DiffBuffer(in1, "1");
            DiffBuffer db2 = new DiffBuffer(in2, "2");

            String diffs[] = diffFiles(db1, db2);

            if (diffs == null)
            {
                debug(1, "no diff");
                return false;
            }
            else
            {
                for (int i = 0; i < diffs.length; i++)
                {
                    this.pw.println(diffs[i]);
                    System.out.println(diffs[i]);
                }
            }

        }
        catch (IOException ioe)
        {
            System.err.println("IOException comparing <" + in1 +
                "> and <" + in2 + ">");
            System.err.println(ioe);

            this.pw.println("IOException comparing <" + in1 +
                "> and <" + in2 + ">");
            this.pw.println(ioe);
        }
        return true;
    }
    public static void main(String args[]) throws IOException
    {

        if (args.length < 2)
        {
            System.err.println("Invalid number of arguments");
            System.err.println("Usage: " + usage);
            System.exit(1);
        }

        SimpleDiff me = new SimpleDiff();

        try
        {
            BufferedReader br1 = new BufferedReader(new FileReader(args[0]));
            BufferedReader br2 = new BufferedReader(new FileReader(args[1]));
            me.doWork(br1, br2, null);
        }
        catch (IOException ioe)
        {
            System.out.println("IOExeption: " + ioe);
        }
    }

    public void pause()
    {
        BufferedInputStream bis = new BufferedInputStream(System.in);
        try
        {
            bis.read();
        }
        catch (IOException ioe)
        {
            pw.println("Error trying to pause...");
            System.out.println("Error trying to pause...");
        }
    }

    class DiffBuffer extends Vector<String>
    {


        public boolean atEOF()
        {
            return atEnd;
        }

        public DiffBuffer(BufferedReader rb)
        {
            this(rb, "");
        }

        public DiffBuffer(BufferedReader rb, String name)
        {
            this (rb, name, 1024);
        }

        public DiffBuffer(BufferedReader rb, String name, int size)
        {
            super(size);
            readBuffer = rb;
            currentLowWater = 0;
            currentHighWater = -1;
            oldLow = 0;
            myName = name;
            atEnd = false;
        }

        public boolean isValidOffset(int lineNumber) throws IOException
        {
            if (atEnd)
            {
                return lineNumber <= actualEndOfFile;
            }

            if (lineAt(lineNumber) == null)
            {
                return false;
            }
            return true;
        }

        public String lineAt(int offset) throws IOException
        {
/*
System.out.println("offset: " + offset);
System.out.println("currentHighWater: " + currentHighWater);
System.out.println("");
*/
            if (offset > currentHighWater)
            {
                for (int i = 0; i < offset - currentHighWater; i++)
                {
                    String aLine = readBuffer.readLine();
                    addElement(aLine);
/*
System.out.println("aLine: " + aLine);
*/
                    if (aLine == null)
                    {
                        if (!atEnd)
                        {
                            //first time we've tried to read past the EOF
                            actualEndOfFile = currentHighWater + i;
//System.out.println(myName + ": length " + actualEndOfFile);
                            atEnd = true;
                        }
                    }
                }
                currentHighWater = offset;
            }
            return (String) elementAt(offset);
        }


        public final String EMPTY = null;
        protected BufferedReader readBuffer;
        protected int currentLowWater;
        protected int currentHighWater;
        private int oldLow;
        protected String myName;
        protected boolean atEnd;
        protected int actualEndOfFile;
        /**
            Useful to keep memory requirements low
         */
        public void setLowWater(int newLow)
        {

            for (int i = oldLow; i < newLow; i++)
            {
                setElementAt(EMPTY, i);
            }
            currentLowWater = newLow;
            oldLow = newLow -1;
        }


    public void iterate(boolean verbose)
    {
        int nulls = 0;
        int nonnulls = 0;


        for (int i = 0; i < this.size(); i++)
        {
            if (elementAt(i) == null)
            {
                if (verbose)
                {
                    System.out.print("[" + i + "] ");
                    System.out.println("null");
                }
                nulls++;

            }
            else
            {
                if (verbose)
                {
                    System.out.print("[" + i + "] ");
                    System.out.println("NotNULL");
                }
                nonnulls++;
            }
        }
        System.out.println("nulls: " + nulls + "  nonNull: " + nonnulls);
    }

    public void close() throws IOException
    {
//		System.out.println("Closing BufferedReader");
        readBuffer.close();
        readBuffer = null;
    }
    }

}