From 277b54711ccd038290dc7463874fc9fc948fe424 Mon Sep 17 00:00:00 2001
From: nathan <nathan@appflowy.io>
Date: Thu, 16 Mar 2023 09:36:49 +0800
Subject: [PATCH] feat: add snowflake

---
 Cargo.lock                  |  4 +++
 Cargo.toml                  |  1 +
 crates/snowflake/Cargo.toml |  8 +++++
 crates/snowflake/src/lib.rs | 63 +++++++++++++++++++++++++++++++++++++
 4 files changed, 76 insertions(+)
 create mode 100644 crates/snowflake/Cargo.toml
 create mode 100644 crates/snowflake/src/lib.rs

diff --git a/Cargo.lock b/Cargo.lock
index 20c7d1d7..52ec66d2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2522,6 +2522,10 @@ version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a507befe795404456341dfab10cef66ead4c041f62b8b11bbb92bffe5d0953e0"
 
+[[package]]
+name = "snowflake"
+version = "0.1.0"
+
 [[package]]
 name = "socket2"
 version = "0.4.9"
diff --git a/Cargo.toml b/Cargo.toml
index fe1fd495..43daccac 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -77,4 +77,5 @@ path = "src/lib.rs"
 members = [
     "crates/token",
     "crates/revdb",
+    "crates/snowflake",
 ]
\ No newline at end of file
diff --git a/crates/snowflake/Cargo.toml b/crates/snowflake/Cargo.toml
new file mode 100644
index 00000000..576e15ca
--- /dev/null
+++ b/crates/snowflake/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "snowflake"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/crates/snowflake/src/lib.rs b/crates/snowflake/src/lib.rs
new file mode 100644
index 00000000..8a63d8f1
--- /dev/null
+++ b/crates/snowflake/src/lib.rs
@@ -0,0 +1,63 @@
+use std::time::{Duration, SystemTime};
+
+const EPOCH: u64 = 1420070400000;
+const NODE_ID_BITS: u64 = 10;
+const SEQUENCE_BITS: u64 = 12;
+const NODE_ID_SHIFT: u64 = SEQUENCE_BITS;
+const TIMESTAMP_SHIFT: u64 = NODE_ID_BITS + SEQUENCE_BITS;
+const SEQUENCE_MASK: u64 = (1 << SEQUENCE_BITS) - 1;
+const MAX_NODE_ID: u64 = (1 << NODE_ID_BITS) - 1;
+
+struct Snowflake {
+    node_id: u64,
+    sequence: u64,
+    last_timestamp: u64,
+}
+
+impl Snowflake {
+    pub fn new(node_id: u64) -> Snowflake {
+        Snowflake {
+            node_id,
+            sequence: 0,
+            last_timestamp: 0,
+        }
+    }
+
+    pub fn next_id(&mut self) -> u64 {
+        let timestamp = self.timestamp();
+        if timestamp < self.last_timestamp {
+            panic!("Clock moved backwards!");
+        }
+
+        if timestamp == self.last_timestamp {
+            self.sequence = (self.sequence + 1) & SEQUENCE_MASK;
+            if self.sequence == 0 {
+                self.wait_next_millis();
+            }
+        } else {
+            self.sequence = 0;
+        }
+
+        self.last_timestamp = timestamp;
+        (timestamp - EPOCH) << TIMESTAMP_SHIFT | self.node_id << NODE_ID_SHIFT | self.sequence
+    }
+
+    fn wait_next_millis(&self) {
+        let mut timestamp = self.timestamp();
+        while timestamp == self.last_timestamp {
+            timestamp = self.timestamp();
+        }
+    }
+
+    fn timestamp(&self) -> u64 {
+        SystemTime::now()
+            .duration_since(SystemTime::UNIX_EPOCH)
+            .unwrap()
+            .as_millis() as u64
+    }
+}
+
+fn main() {
+    let mut snowflake = Snowflake::new(1);
+    println!("{}", snowflake.next_id());
+}