/*
 * Basic attempt at an MD5 encryption htpasswd utility class.
 * Why don't we get the same hash as htpasswd -m ???  Maybe MD5 algols are different?
 * hmmmm.
 * 
 */


package org.crosswire.utils;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.security.MessageDigest;
import java.util.HashMap;
import java.util.Set;
import java.util.UUID;

public class HTPassword {

	static final String AP_MD5PW_ID = "$apr1$";
	static final int APR_MD5_DIGESTSIZE = 16;

	String file = null;
	
	static class Entry {
		public Entry(String user, String pw) { this.user = user; this.pw = pw; }
		public String user;
		public String pw;
	}

	HashMap<String, Entry> entries = new HashMap<String, Entry>();
	
	
	public HTPassword(String file) {
		this.file = file;
		BufferedReader in;
		try {
			in = new BufferedReader(new FileReader(file));
			for (String line = in.readLine(); line != null; line = in.readLine()) {
				int offset = line.indexOf(":");
				if (offset > 0) {
					entries.put(line.substring(0, offset), new Entry(line.substring(0, offset), line.substring(offset+1)));
				}
			}
			in.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public Set<String> getUsers() {
		return entries.keySet();
	}

	public String getMunged(String user) {
		String pw = null;
		Entry e = entries.get(user);
		if (e != null)
			pw = e.pw;
		return pw;
	}

	public String encryptString(String input) {
		return encryptString(input, AP_MD5PW_ID + UUID.randomUUID().toString());
	}

	static String to64(int v, int n) {
		String retVal = "";
		String itoa64 = /* 0 ... 63 => ASCII - 64 */
		"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

		while (--n >= 0) {
			retVal += itoa64.charAt(v & 0x3f);
			v >>= 6;
		}
		return retVal;
	}

	private static int unsigned(byte v) {
		return ((v<0)?256+v:v);
	}
	
	
	public String encryptString(String input, String salt) {
		String encrypted = null;
		try {
			MessageDigest md = MessageDigest.getInstance("MD5");
			MessageDigest md2 = (MessageDigest)md.clone();
			md.reset();
			md2.reset();

			// if it starts with magic string, skip it
			if (salt.startsWith(AP_MD5PW_ID)) {
				salt = salt.substring(AP_MD5PW_ID.length());
			}
			int ep = salt.indexOf('$');
			if (ep < 0)	ep = salt.length();
			if (ep > 8)	ep = 8;
			salt = salt.substring(0, ep);

			md.update(input.getBytes());
			md.update(AP_MD5PW_ID.getBytes());
			md.update(salt.getBytes());

			md2.update(input.getBytes());
			md2.update(salt.getBytes());
			md2.update(input.getBytes());
			byte md2digest[] = md2.digest();

			for (int pl = input.length(); pl > 0; pl -= APR_MD5_DIGESTSIZE) {
				md.update(md2digest, 0,
						(pl > APR_MD5_DIGESTSIZE) ? APR_MD5_DIGESTSIZE : pl);
			}

			for (int i = input.length(); i != 0; i >>= 1) {
				if ((i & 1) != 0) {
					md.update(md2digest, 0, 1);
				} else {
					md.update(input.getBytes(), 0, 1);
				}
			}

			encrypted = AP_MD5PW_ID;
			encrypted += salt;
			encrypted += "$";
			byte mddigest[] = md.digest();
			
			for (int i = 0; i < 1000; i++) {
				md2.reset();
				if ((i & 1) != 0) {
					md2.update(input.getBytes());
				} else {
					md2.update(mddigest, 0, APR_MD5_DIGESTSIZE);
				}
				if ((i % 3) != 0) {
					md2.update(salt.getBytes());
				}

				if ((i % 7) != 0) {
					md2.update(input.getBytes());
				}

				if ((i & 1) != 0) {
					md2.update(mddigest, 0, APR_MD5_DIGESTSIZE);
				} else {
					md2.update(input.getBytes());
				}
				mddigest = md2.digest();
			}

			int hash[] = new int[APR_MD5_DIGESTSIZE];
			for (int i = 0; i < APR_MD5_DIGESTSIZE; i++) hash[i] = unsigned(mddigest[i]);
			int l = (hash[0] << 16) | (hash[6] << 8) | hash[12];
			encrypted += to64(l, 4);
			l = (hash[1] << 16) | (hash[7] << 8) | hash[13];
			encrypted += to64(l, 4);
			l = (hash[2] << 16) | (hash[8] << 8) | hash[14];
			encrypted += to64(l, 4);
			l = (hash[3] << 16) | (hash[9] << 8) | hash[15];
			encrypted += to64(l, 4);
			l = (hash[4] << 16) | (hash[10] << 8) | hash[5];
			encrypted += to64(l, 4);
			l = hash[11];
			encrypted += to64(l, 2);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return encrypted;
	}

	
	public boolean checkPassword(String user, String pw) {
		String munged = getMunged(user);
		return encryptString(pw, munged).equals(munged);
	}
	
	static synchronized public void setAccount(String file, String user, String pw) {
		HTPassword p = new HTPassword(file);
		p.entries.put(user, new Entry(user, p.encryptString(pw)));
		BufferedWriter out;
		try {
			out = new BufferedWriter(new FileWriter(file, false));
			for (Entry e: p.entries.values()) {
				out.write(e.user+":"+e.pw);
				out.newLine();
			}
			out.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	
	/**
	 * test code
	 */
	public static void main(String[] args) {
		HTPassword password = new HTPassword("passwd");
		for (String user : password.getUsers()) {
			System.out.println(user);
		}
		HTPassword.setAccount("passwd", "scribe", "hmmmm");
		HTPassword.setAccount("passwd", "scrsdfaibe", "hmmmm");
		password = new HTPassword("passwd");
		System.out.println("working: "+password.checkPassword("scribe", "hmmmm"));
	}

}