origin1tech · January 28, 2023 13:13 · Mar 17, 2017 · Mar 17, 2017
diff --git a/uid.ts b/uid.ts
@@ -20,7 +20,7 @@ export interface IUID {
 // ASCII ordered base64 web safe chars.
 const ASCII_CHARS = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
 
-const uid: IUID = {
+export const uid: IUID = {
 
   /**
    * Generate

diff --git a/uid.ts b/uid.ts
@@ -0,0 +1,134 @@
+
+
+export interface IUID {
+  generate(): string;
+  timestamp(uid: string, asDate?: boolean): number | Date;
+}
+
+/**
+ * SEE --> https://gist.github.com/mikelehen/3596a30bd69384624c11
+ * 
+ * Generator that creates 20-character string identifiers with the following properties:
+ *
+ * 1. They're based on timestamp so that they sort *after* any existing ids.
+ * 2. They contain 72-bits of random data after the timestamp so that IDs won't collide.
+ * 3. They sort *lexicographically* (timestamp converted to chars which will sort)
+ * 4. They're monotonically increasing. This is done by storing previous random bits
+ *    increasing them only by one.
+ */
+
+// ASCII ordered base64 web safe chars.
+const ASCII_CHARS = '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
+
+const uid: IUID = {
+
+  /**
+   * Generate
+   * Generates uid push identifier.
+   */
+  generate: (function () {
+
+    // Timestamp of last push, used to prevent local
+    // collisions if you push twice in one ms.
+    let lastPushTime = 0;
+
+    // We generate 72-bits of randomness which get
+    // turned into 12 characters and appended to the
+    // timestamp to prevent collisions with other clients.
+    // We store the last characters we generated because
+    // in the event of a collision, we'll use those same
+    // characters except "incremented" by one.
+    const lastRandChars = [];
+
+    return function () {
+
+      let now = new Date().getTime();
+      let duplicateTime = (now === lastPushTime);
+
+      lastPushTime = now;
+
+      let timeStampChars: string[] = new Array(8);
+
+      let i: number;
+
+      for (i = 7; i >= 0; i--) {
+
+        timeStampChars[i] = PUSH_CHARS.charAt(now % 64);
+
+        // NOTE: Can't use << here because javascript
+        // will convert to int and lose the upper bits.
+        now = Math.floor(now / 64);
+
+      }
+
+      if (now !== 0) throw new Error('We should have converted the entire timestamp.');
+
+      let id = timeStampChars.join('');
+
+      if (!duplicateTime) {
+
+        for (i = 0; i < 12; i++) {
+
+          lastRandChars[i] = Math.floor(Math.random() * 64);
+
+        }
+
+      }
+
+      // If the timestamp hasn't changed since
+      // last push, use the same random number,
+      // except incremented by 1.
+      else {
+
+        for (i = 11; i >= 0 && lastRandChars[i] === 63; i--) {
+
+          lastRandChars[i] = 0;
+
+        }
+
+        lastRandChars[i]++;
+
+      }
+
+      for (i = 0; i < 12; i++) {
+
+        id += ASCII_CHARS.charAt(lastRandChars[i]);
+
+      }
+
+      if (id.length !== 20)
+        throw new Error('Length should be 20.');
+
+      return id;
+
+    };
+
+  })(),
+
+  /**
+   * Timestamp
+   * Gets timestamp from provided uid.
+   */
+  timestamp: (function () {
+
+    return function (id: string, asDate?: boolean): number | Date {
+
+      let time = 0;
+      const data = id.substr(0, 8);
+
+      for (let i = 0; i < 8; i++) {
+
+        time = time * 64 + ASCII_CHARS.indexOf(data[i]);
+
+      }
+
+      if (asDate)
+        return new Date(time);
+
+      return time;
+
+    };
+
+  })()
+
+};