import java.io.*;
import java.util.*;

/**
 * read compressed boggle file, store words in ArrayList
 * can also write an ArrayList in compressed format
 * to be read again
 *
 *
 * @author Owen Astrachan
 * @version 0.9
 */

public class BogReader
{
    /**
     * construct a reader to read from compressed bogdict file
     */
    
    public BogReader()
    {
        // nothing to create
    }

    /**
     * read words from a compressed file (non-standard compression)
     * currently the filename is hardwired, but it's an easy
     * change to make the filename a parameter
     *
     * @param trie is the Trie to read words into
     */
    
    public String[] readWords( )
    {
        FileInputStream f = null;
        try {
            String filename = "bogdict";
            
            f = new FileInputStream(filename);      
            File file = new File(filename);
            byte buffer[] = new byte[(int) file.length()];

            // read entire file, report reading, process file
            
            int bytesRead = f.read(buffer,0,buffer.length);
            System.out.println("read = " + bytesRead); 
            String[] list = processBuffer(buffer,bytesRead);
            try {
                f.close();
            }
            catch (IOException e) {
                // nothing here
            }
            return list;
        }
        catch (IOException e) {
            e.printStackTrace();
            System.err.println("error reading dictionary " + e);
        }
        return null;
    }

    /**
     * read words, store in and return array of words
     *
     * @param buffer is the compressed characters to be uncompressed
     */
    String[] processBuffer(byte buffer[], int size)
    {
        ArrayList list = new ArrayList();
        char sb[] = new char[20];
        int k;
        int count = 0;
        int numWords = 0;
        char ch;
        int index;
        for(index = 0; index < size; index++) {
            ch = (char) buffer[index];
            if (Character.isLowerCase(ch)) {
                sb[count++] = ch;
            }
            else {                          // word ended, process
                if (count > 0) {
                    list.add(new String(sb,0,count));
                    numWords++;
                    if (numWords % 1000 == 0) {
                        System.out.println("processed " + numWords
                                           + " words ");
                    }
                }
                // decrease effective size of sb by ch characters
                // this treats ch (a control char) as a number
                // e.g., ^D (control-D) is 4

                while (count >= 0 && count != (int) ch) {
                    sb[count--] = '\0';
                }
            }
        }
        return (String []) list.toArray(new String[0]);
    }   

    // find length of common prefix of a and b
    
    private int prefixLength(String a, String b)
    {
        int k;
        int size = a.length() < b.length() ? a.length() : b.length();
        int commonCount = 0;
        for(k=0; k < size; k++) {
            if (a.charAt(k) == b.charAt(k)) commonCount++;
            else return commonCount;
        }
        return commonCount;     
    }
    /**
     * write words to a compressed file (e.g., for subsequent reading)
     *
     * @param list is strings to be written in compressed format
     * @param filename the name of the file storing compressed words
     */
    public void writeWords(List list, String filename)
    {
        
        FileOutputStream st = null;
        DataOutputStream f = null;

        try
        {
            st = new FileOutputStream(filename);
            f = new DataOutputStream(st);
            int k;
            String last = "";
            int prefix;
            byte buffer[] = null;
            for(k=0; k < list.size(); k++) {
                String s = (String) list.get(k);
                prefix = prefixLength(last,s);
                last = s;
                f.writeByte(prefix);
                buffer = s.getBytes();
                f.write(buffer,prefix,s.length()-prefix);
                
                if (k % 1000 == 0) {
                    System.out.println("wrote " + k + " words ");
                }
            }
            f.writeByte(10);   // write a linefeed
            
        }
        catch (IOException e) {
            System.out.println("error opening " + filename);
        }
        finally {
            try {
                f.close(); st.close();
            }
            catch (IOException e){
                
            }
        }
    }

    public static void main(String args[])
    {
        BogReader r = new BogReader();
        String[] list = r.readWords();
        for(int k=0; k < list.length; k++) {
            System.out.println(list[k]);
        }
        r.writeWords(Arrays.asList(list),"out");
    }
}