package gnu.inet.encoding;
public class Punycode
{
final static int TMIN = 1;
final static int TMAX = 26;
final static int BASE = 36;
final static int INITIAL_N = 128;
final static int INITIAL_BIAS = 72;
final static int DAMP = 700;
final static int SKEW = 38;
final static char DELIMITER = '-';
public static String encode(String input)
throws PunycodeException
{
int n = INITIAL_N;
int delta = 0;
int bias = INITIAL_BIAS;
StringBuffer output = new StringBuffer();
int b = 0;
for (int i = 0; i < input.length(); i++) {
char c = input.charAt(i);
if (isBasic(c)) {
output.append(c);
b++;
}
}
if (b > 0) {
output.append(DELIMITER);
}
int h = b;
while (h < input.length()) {
int m = Integer.MAX_VALUE;
for (int i = 0; i < input.length(); i++) {
int c = input.charAt(i);
if (c >= n && c < m) {
m = c;
}
}
if (m - n > (Integer.MAX_VALUE - delta) / (h + 1)) {
throw new PunycodeException(PunycodeException.OVERFLOW);
}
delta = delta + (m - n) * (h + 1);
n = m;
for (int j = 0; j < input.length(); j++) {
int c = input.charAt(j);
if (c < n) {
delta++;
if (0 == delta) {
throw new PunycodeException(PunycodeException.OVERFLOW);
}
}
if (c == n) {
int q = delta;
for (int k = BASE;; k += BASE) {
int t;
if (k <= bias) {
t = TMIN;
} else if (k >= bias + TMAX) {
t = TMAX;
} else {
t = k - bias;
}
if (q < t) {
break;
}
output.append((char) digit2codepoint(t + (q - t) % (BASE - t)));
q = (q - t) / (BASE - t);
}
output.append((char) digit2codepoint(q));
bias = adapt(delta, h + 1, h == b);
delta = 0;
h++;
}
}
delta++;
n++;
}
return output.toString();
}
public static String decode(String input)
throws PunycodeException
{
int n = INITIAL_N;
int i = 0;
int bias = INITIAL_BIAS;
StringBuffer output = new StringBuffer();
int d = input.lastIndexOf(DELIMITER);
if (d > 0) {
for (int j = 0; j < d; j++) {
char c = input.charAt(j);
if (!isBasic(c)) {
throw new PunycodeException(PunycodeException.BAD_INPUT);
}
output.append(c);
}
d++;
} else {
d = 0;
}
while (d < input.length()) {
int oldi = i;
int w = 1;
for (int k = BASE; ; k += BASE) {
if (d == input.length()) {
throw new PunycodeException(PunycodeException.BAD_INPUT);
}
int c = input.charAt(d++);
int digit = codepoint2digit(c);
if (digit > (Integer.MAX_VALUE - i) / w) {
throw new PunycodeException(PunycodeException.OVERFLOW);
}
i = i + digit * w;
int t;
if (k <= bias) {
t = TMIN;
} else if (k >= bias + TMAX) {
t = TMAX;
} else {
t = k - bias;
}
if (digit < t) {
break;
}
w = w * (BASE - t);
}
bias = adapt(i - oldi, output.length()+1, oldi == 0);
if (i / (output.length() + 1) > Integer.MAX_VALUE - n) {
throw new PunycodeException(PunycodeException.OVERFLOW);
}
n = n + i / (output.length() + 1);
i = i % (output.length() + 1);
output.insert(i, (char) n);
i++;
}
return output.toString();
}
public final static int adapt(int delta, int numpoints, boolean first)
{
if (first) {
delta = delta / DAMP;
} else {
delta = delta / 2;
}
delta = delta + (delta / numpoints);
int k = 0;
while (delta > ((BASE - TMIN) * TMAX) / 2) {
delta = delta / (BASE - TMIN);
k = k + BASE;
}
return k + ((BASE - TMIN + 1) * delta) / (delta + SKEW);
}
public final static boolean isBasic(char c)
{
return c < 0x80;
}
public final static int digit2codepoint(int d)
throws PunycodeException
{
if (d < 26) {
return d + 'a';
} else if (d < 36) {
return d - 26 + '0';
} else {
throw new PunycodeException(PunycodeException.BAD_INPUT);
}
}
public final static int codepoint2digit(int c)
throws PunycodeException
{
if (c - '0' < 10) {
return c - '0' + 26;
} else if (c - 'a' < 26) {
return c - 'a';
} else {
throw new PunycodeException(PunycodeException.BAD_INPUT);
}
}
}