implement yeast

src/main/java/io/socket/yeast/Yeast.java

@@ -0,0 +1,58 @@
+package io.socket.yeast;
+
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A Java implementation of yeast. https://github.com/unshiftio/yeast
+ */
+public class Yeast {
+    private static char[] alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_".toCharArray();
+
+    private static int length = alphabet.length;
+
+    private static Map<Character, Integer> map = new HashMap<Character, Integer>(length);
+    static {
+        for (int i = 0; i < length; i++) {
+            map.put(alphabet[i], i);
+        }
+    }
+
+    private static int seed = 0;
+
+    private static String prev;
+
+    public static String encode(long num) {
+        final StringBuilder encoded = new StringBuilder();
+
+        do {
+            encoded.insert(0, alphabet[(int)(num % length)]);
+            num = (long)Math.floor(num / length);
+        } while (num > 0);
+
+        return encoded.toString();
+    }
+
+    public static long decode(String str) {
+        long decoded = 0;
+
+        for (char c : str.toCharArray()) {
+            decoded = decoded * length + map.get(c);
+        }
+
+        return decoded;
+    }
+
+    public static String yeast() {
+        String now = encode(new Date().getTime());
+
+        if (!now.equals(prev)) {
+            seed = 0;
+            prev = now;
+            return now;
+        }
+
+        return now + "." + encode(seed++);
+    }
+}

src/test/java/io/socket/yeast/YeastTest.java

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+package io.socket.yeast;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.util.Arrays;
+import java.util.Date;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.not;
+import static org.junit.Assert.assertThat;
+
+;
+
+@RunWith(JUnit4.class)
+public class YeastTest {
+
+    private void waitUntilNextMillisecond() {
+        long now = new Date().getTime();
+        while (new Date().getTime() == now) { /* do nothing */ }
+    }
+
+    @Test
+    public void prependsIteratedSeedWhenSamePreviousId() {
+        waitUntilNextMillisecond();
+
+        String[] ids = new String[] { Yeast.yeast(), Yeast.yeast(), Yeast.yeast() };
+        assertThat(ids[0], not(containsString(".")));
+        assertThat(ids[1], containsString(".0"));
+        assertThat(ids[2], containsString(".1"));
+    }
+
+    @Test
+    public void resetsTheSeed() {
+        waitUntilNextMillisecond();
+
+        String[] ids = new String[] { Yeast.yeast(), Yeast.yeast(), Yeast.yeast() };
+        assertThat(ids[0], not(containsString(".")));
+        assertThat(ids[1], containsString(".0"));
+        assertThat(ids[2], containsString(".1"));
+
+        waitUntilNextMillisecond();
+
+        ids = new String[] { Yeast.yeast(), Yeast.yeast(), Yeast.yeast() };
+        assertThat(ids[0], not(containsString(".")));
+        assertThat(ids[1], containsString(".0"));
+        assertThat(ids[2], containsString(".1"));
+    }
+
+    @Test
+    public void doesNotCollide() {
+        int length = 30000;
+        String[] ids = new String[length];
+
+        for (int i = 0; i < length; i++) ids[i] = Yeast.yeast();
+
+        Arrays.sort(ids);
+
+        for (int i = 0; i < length - 1; i++) {
+            assertThat(ids[i], not(equalTo(ids[i + 1])));
+        }
+    }
+
+    @Test
+    public void canConvertIdToTimestamp() {
+        waitUntilNextMillisecond();
+
+        long now = new Date().getTime();
+        String id = Yeast.yeast();
+
+        assertThat(Yeast.encode(now), equalTo(id));
+        assertThat(Yeast.decode(id), equalTo(now));
+    }
+}