commit 17a569c703a682021c66214dfde3dd51b0a2f361
Author: Mingwei Samuel <mingwei.samuel@gmail.com>
Date:   Sat Oct 12 00:48:15 2019 -0700

    initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6936990
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/target
+**/*.rs.bk
+Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..ac6e272
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "riven"
+version = "0.0.1"
+authors = ["Mingwei Samuel <mingwei.samuel@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..9de84d7
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,11 @@
+mod req;
+
+use req::rate_limit;
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}
diff --git a/src/req/mod.rs b/src/req/mod.rs
new file mode 100644
index 0000000..f07548e
--- /dev/null
+++ b/src/req/mod.rs
@@ -0,0 +1,2 @@
+pub mod rate_limit;
+pub mod token_bucket;
\ No newline at end of file
diff --git a/src/req/rate_limit.rs b/src/req/rate_limit.rs
new file mode 100644
index 0000000..fe91cc2
--- /dev/null
+++ b/src/req/rate_limit.rs
@@ -0,0 +1,6 @@
+use std::time::Duration;
+
+pub trait RateLimit {
+    fn get_retry_after_delay(&self) -> Duration;
+}
+
diff --git a/src/req/token_bucket.rs b/src/req/token_bucket.rs
new file mode 100644
index 0000000..8967692
--- /dev/null
+++ b/src/req/token_bucket.rs
@@ -0,0 +1,93 @@
+use std::collections::VecDeque;
+use std::time::{Duration, Instant};
+
+pub trait TokenBucket {
+    /// Get the duration til the next available token, or 0 duration if a token is available.
+    /// # Returns
+    /// Duration or 0 duration.
+    fn get_delay(&mut self) -> Duration;
+
+    /// Gets n tokens, regardless of whether they are available.
+    /// # Parameters
+    /// * `n` - Number of tokens to take.
+    /// # Returns
+    /// True if the tokens were obtained without violating limits, false otherwise.
+    fn get_tokens(&mut self, n: usize) -> bool;
+
+    /// Get the duration of this bucket.
+    /// # Returns
+    /// Duration of the bucket.
+    fn get_bucket_duration(&self) -> Duration;
+
+    /// Get the total limit of this bucket per timespan.
+    /// # Returns
+    /// Total limit per timespan.
+    fn get_total_limit(&self) -> usize;
+}
+
+struct VectorTokenBucket {
+    /// Duration of this TokenBucket.
+    duration: Duration,
+    // Total tokens available from this TokenBucket.
+    total_limit: usize,
+    // Record of timestamps.
+    timestamps: VecDeque<Instant>,
+}
+
+impl VectorTokenBucket {
+    fn create(duration: Duration, total_limit: usize) -> Self {
+        VectorTokenBucket {
+            duration: duration,
+            total_limit: total_limit,
+            timestamps: VecDeque::new(),
+        }
+    }
+
+    fn update_state(&mut self) {
+        let cutoff = Instant::now() - self.duration;
+        while self.timestamps.back().map_or(false, |ts| ts < &cutoff) {
+            self.timestamps.pop_back();
+        }
+    }
+}
+
+impl TokenBucket for VectorTokenBucket {
+
+    fn get_delay(&mut self) -> Duration {
+        self.update_state();
+        if self.timestamps.len() < self.total_limit {
+            Duration::new(0, 0)
+        }
+        else {
+            let ts = *self.timestamps.get(self.total_limit - 1).unwrap();
+            Instant::now().saturating_duration_since(ts)
+        }
+    }
+
+    fn get_tokens(&mut self, n: usize) -> bool {
+        self.update_state();
+        let now = Instant::now();
+
+        self.timestamps.reserve(n);
+        for _ in 0..n {
+            self.timestamps.push_front(now);
+        }
+        self.timestamps.len() <= self.total_limit
+    }
+
+    fn get_bucket_duration(&self) -> Duration {
+        self.duration
+    }
+
+    fn get_total_limit(&self) -> usize {
+        self.total_limit
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}