package org.apache.commons.lang3;

import java.util.Random;

public class RandomStringUtils {
   private static final Random RANDOM = new Random();

   public static String random(int count) {
      return random(count, false, false);
   }

   public static String randomAscii(int count) {
      return random(count, 32, 127, false, false);
   }

   public static String randomAlphabetic(int count) {
      return random(count, true, false);
   }

   public static String randomAlphanumeric(int count) {
      return random(count, true, true);
   }

   public static String randomNumeric(int count) {
      return random(count, false, true);
   }

   public static String random(int count, boolean letters, boolean numbers) {
      return random(count, 0, 0, letters, numbers);
   }

   public static String random(int count, int start, int end, boolean letters, boolean numbers) {
      return random(count, start, end, letters, numbers, (char[])null, RANDOM);
   }

   public static String random(int count, int start, int end, boolean letters, boolean numbers, char... chars) {
      return random(count, start, end, letters, numbers, chars, RANDOM);
   }

   public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars, Random random) {
      if (count == 0) {
         return "";
      } else if (count < 0) {
         throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
      } else if (chars != null && chars.length == 0) {
         throw new IllegalArgumentException("The chars array must not be empty");
      } else {
         if (start == 0 && end == 0) {
            if (chars != null) {
               end = chars.length;
            } else if (!letters && !numbers) {
               end = Integer.MAX_VALUE;
            } else {
               end = 123;
               start = 32;
            }
         } else if (end <= start) {
            throw new IllegalArgumentException("Parameter end (" + end + ") must be greater than start (" + start + ")");
         }

         char[] buffer = new char[count];
         int gap = end - start;

         while(true) {
            while(true) {
               while(count-- != 0) {
                  char ch;
                  if (chars == null) {
                     ch = (char)(random.nextInt(gap) + start);
                  } else {
                     ch = chars[random.nextInt(gap) + start];
                  }

                  if (letters && Character.isLetter(ch) || numbers && Character.isDigit(ch) || !letters && !numbers) {
                     if (ch >= '\udc00' && ch <= '\udfff') {
                        if (count == 0) {
                           ++count;
                        } else {
                           buffer[count] = ch;
                           --count;
                           buffer[count] = (char)('\ud800' + random.nextInt(128));
                        }
                     } else if (ch >= '\ud800' && ch <= '\udb7f') {
                        if (count == 0) {
                           ++count;
                        } else {
                           buffer[count] = (char)('\udc00' + random.nextInt(128));
                           --count;
                           buffer[count] = ch;
                        }
                     } else if (ch >= '\udb80' && ch <= '\udbff') {
                        ++count;
                     } else {
                        buffer[count] = ch;
                     }
                  } else {
                     ++count;
                  }
               }

               return new String(buffer);
            }
         }
      }
   }

   public static String random(int count, String chars) {
      return chars == null ? random(count, 0, 0, false, false, (char[])null, RANDOM) : random(count, chars.toCharArray());
   }

   public static String random(int count, char... chars) {
      return chars == null ? random(count, 0, 0, false, false, (char[])null, RANDOM) : random(count, 0, chars.length, false, false, chars, RANDOM);
   }
}
