counter is now a wrapper over mcaptcha

CHANGELOG.md

@@ -15,11 +15,8 @@
 - `master::Master` is moved to `master::embedded::master` in preparation
   for Redis based implementation.
 
-- `crate::mcaptcha` is moved to `master::embedded::counter` in preparation
-  for Redis based implementation.
-
 - `AddSite` message for `Master` now requires an instance of
-  `crate::master::MCaptcha`. In the case of
+  `crate::mcaptcha::MCaptcha`. In the case of
   `crate::master::embedded::master`, it automatically starts `Counter`
   actor.
 
@@ -54,7 +51,7 @@
 
 ## Changed
 
-- actix upgraded to `0.11`
+- `actix` upgraded to `0.11`
 
 ## 0.1.1
 

Cargo.lock

@@ -9,7 +9,7 @@ dependencies = [
  "actix-rt",
  "actix_derive",
  "bitflags",
- "bytes",
+ "bytes 0.5.6",
  "crossbeam-channel",
  "derive_more",
  "futures-channel",
@@ -19,8 +19,8 @@ dependencies = [
  "parking_lot",
  "pin-project",
  "smallvec",
- "tokio",
+ "tokio 0.2.25",
- "tokio-util",
+ "tokio-util 0.3.1",
  "trust-dns-proto",
  "trust-dns-resolver",
 ]
@@ -47,7 +47,7 @@ dependencies = [
  "futures-channel",
  "futures-util",
  "smallvec",
- "tokio",
+ "tokio 0.2.25",
 ]
 
 [[package]]
@@ -150,6 +150,12 @@ version = "0.5.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0e4cec68f03f32e44924783795810fa50a7035d8c8ebe78580ad7e6c703fba38"
 
+[[package]]
+name = "bytes"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b700ce4376041dcd0a327fd0097c41095743c4c8af8887265942faf1100bd040"
+
 [[package]]
 name = "cfg-if"
 version = "0.1.10"
@@ -162,6 +168,19 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "combine"
+version = "4.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc4369b5e4c0cddf64ad8981c0111e7df4f7078f4d6ba98fb31f2e17c4c57b7e"
+dependencies = [
+ "bytes 1.0.1",
+ "futures-util",
+ "memchr",
+ "pin-project-lite 0.2.6",
+ "tokio 1.6.1",
+]
+
 [[package]]
 name = "convert_case"
 version = "0.4.0"
@@ -180,6 +199,12 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8aebca1129a03dc6dc2b127edd729435bbc4a37e1d5f4d7513165089ceb02634"
 
+[[package]]
+name = "crc16"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "338089f42c427b86394a5ee60ff321da23a5c89c9d89514c829687b26359fcff"
+
 [[package]]
 name = "crossbeam-channel"
 version = "0.4.4"
@@ -349,6 +374,12 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "dtoa"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56899898ce76aaf4a0f24d914c97ea6ed976d42fec6ad33fcbb0a1103e07b2b0"
+
 [[package]]
 name = "enum-as-inner"
 version = "0.3.3"
@@ -628,6 +659,7 @@ dependencies = [
  "pow_sha256",
  "pretty_env_logger",
  "rand 0.8.3",
+ "redis",
  "serde",
  "serde_json",
 ]
@@ -702,12 +734,25 @@ dependencies = [
  "kernel32-sys",
  "libc",
  "log",
- "miow",
+ "miow 0.2.2",
  "net2",
  "slab",
  "winapi 0.2.8",
 ]
 
+[[package]]
+name = "mio"
+version = "0.7.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cf80d3e903b34e0bd7282b218398aec54e082c840d9baf8339e0080a0c542956"
+dependencies = [
+ "libc",
+ "log",
+ "miow 0.3.7",
+ "ntapi",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "mio-uds"
 version = "0.6.8"
@@ -716,7 +761,7 @@ checksum = "afcb699eb26d4332647cc848492bbc15eafb26f08d0304550d5aa1f612e066f0"
 dependencies = [
  "iovec",
  "libc",
- "mio",
+ "mio 0.6.23",
 ]
 
 [[package]]
@@ -731,6 +776,15 @@ dependencies = [
  "ws2_32-sys",
 ]
 
+[[package]]
+name = "miow"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9f1c5b025cda876f66ef43a113f91ebc9f4ccef34843000e0adf6ebbab84e21"
+dependencies = [
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "net2"
 version = "0.2.37"
@@ -742,6 +796,15 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "ntapi"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f6bb902e437b6d86e03cce10a7e2af662292c5dfef23b65899ea3ac9354ad44"
+dependencies = [
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "num_cpus"
 version = "1.13.0"
@@ -965,6 +1028,28 @@ dependencies = [
  "rand_core 0.6.2",
 ]
 
+[[package]]
+name = "redis"
+version = "0.20.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0a32cb439c4e89c1e6415e5b3b23d9d8cc6dc1bf5a8cade19adbd5418de803be"
+dependencies = [
+ "async-trait",
+ "bytes 1.0.1",
+ "combine",
+ "crc16",
+ "dtoa",
+ "futures-util",
+ "itoa",
+ "percent-encoding",
+ "pin-project-lite 0.2.6",
+ "rand 0.8.3",
+ "sha1",
+ "tokio 1.6.1",
+ "tokio-util 0.6.7",
+ "url",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.2.5"
@@ -1044,6 +1129,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "sha1"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2579985fda508104f7587689507983eadd6a6e84dd35d6d115361f530916fa0d"
+
 [[package]]
 name = "sha2"
 version = "0.9.3"
@@ -1171,14 +1262,14 @@ version = "0.2.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6703a273949a90131b290be1fe7b039d0fc884aa1935860dfcbe056f28cd8092"
 dependencies = [
- "bytes",
+ "bytes 0.5.6",
  "fnv",
  "futures-core",
  "iovec",
  "lazy_static",
  "libc",
  "memchr",
- "mio",
+ "mio 0.6.23",
  "mio-uds",
  "pin-project-lite 0.1.12",
  "signal-hook-registry",
@@ -1186,19 +1277,47 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "tokio"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0a38d31d7831c6ed7aad00aa4c12d9375fd225a6dd77da1d25b707346319a975"
+dependencies = [
+ "autocfg",
+ "bytes 1.0.1",
+ "libc",
+ "memchr",
+ "mio 0.7.11",
+ "pin-project-lite 0.2.6",
+]
+
 [[package]]
 name = "tokio-util"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "be8242891f2b6cbef26a2d7e8605133c2c554cd35b3e4948ea892d6d68436499"
 dependencies = [
- "bytes",
+ "bytes 0.5.6",
  "futures-core",
  "futures-io",
  "futures-sink",
  "log",
  "pin-project-lite 0.1.12",
- "tokio",
+ "tokio 0.2.25",
+]
+
+[[package]]
+name = "tokio-util"
+version = "0.6.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1caa0b0c8d94a049db56b5acf8cba99dc0623aab1b26d5b5f5e2d945846b3592"
+dependencies = [
+ "bytes 1.0.1",
+ "futures-core",
+ "futures-sink",
+ "log",
+ "pin-project-lite 0.2.6",
+ "tokio 1.6.1",
 ]
 
 [[package]]
@@ -1217,7 +1336,7 @@ dependencies = [
  "rand 0.7.3",
  "smallvec",
  "thiserror",
- "tokio",
+ "tokio 0.2.25",
  "url",
 ]
 
@@ -1236,7 +1355,7 @@ dependencies = [
  "resolv-conf",
  "smallvec",
  "thiserror",
- "tokio",
+ "tokio 0.2.25",
  "trust-dns-proto",
 ]
 

Cargo.toml

@@ -24,6 +24,7 @@ derive_more = "0.99"
 
 rand = "0.8"
 pow_sha256 = { version = "0.2.1", git = "https://github.com/mcaptcha/pow_sha256" }
+redis = { version = "0.20.1", features = ["tokio-comp","aio", "cluster"]  }
 
 [dev-dependencies]
 actix-rt = "1"

src/lib.rs

@@ -189,6 +189,7 @@ pub mod master;
 
 /// message datatypes to interact with [MCaptcha] actor
 pub mod cache;
+pub mod mcaptcha;
 pub mod pow;
 pub mod system;
 mod utils;
@@ -197,4 +198,4 @@ pub use crate::cache::hashcache::HashCache;
 
 pub use defense::{Defense, DefenseBuilder, LevelBuilder};
 pub use master::embedded::counter::Counter;
-pub use master::MCaptchaBuilder;
+pub use mcaptcha::{MCaptcha, MCaptchaBuilder};

src/master/embedded/counter.rs

@@ -21,7 +21,7 @@
 //! ```rust
 //! use libmcaptcha::{
 //!     master::embedded::counter::{Counter, AddVisitor},
-//!     master::MCaptchaBuilder,
+//!     MCaptchaBuilder,
 //!     cache::HashCache,
 //!     LevelBuilder,
 //!     DefenseBuilder
@@ -86,56 +86,49 @@ use std::time::Duration;
 use actix::dev::*;
 use serde::{Deserialize, Serialize};
 
-use crate::master::MCaptcha;
+use crate::master::AddVisitorResult;
-use crate::{defense::Defense, master::AddVisitorResult};
+use crate::mcaptcha::MCaptcha;
 
 /// This struct represents the mCaptcha state and is used
 /// to configure leaky-bucket lifetime and manage defense
 #[derive(Clone, Serialize, Deserialize, Debug)]
-pub struct Counter {
+pub struct Counter(MCaptcha);
-    visitor_threshold: u32,
+
-    defense: Defense,
-    duration: u64,
-}
 impl From<MCaptcha> for Counter {
     fn from(m: MCaptcha) -> Counter {
-        let m = Counter {
+        Counter(m)
-            duration: m.duration,
-            defense: m.defense,
-            visitor_threshold: m.visitor_threshold,
-        };
-        m
     }
 }
 
-impl Counter {
+// impl Counter {
-    /// increments the visitor count by one
+//     /// increments the visitor count by one
-    pub fn add_visitor(&mut self) {
+//     pub fn add_visitor(&mut self) {
-        self.visitor_threshold += 1;
+//         self.visitor_threshold += 1;
-        if self.visitor_threshold > self.defense.visitor_threshold() {
+//         if self.visitor_threshold > self.defense.visitor_threshold() {
-            self.defense.tighten_up();
+//             self.defense.tighten_up();
-        } else {
+//         } else {
-            self.defense.loosen_up();
+//             self.defense.loosen_up();
-        }
+//         }
-    }
+//     }
+//
+//     /// decrements the visitor count by one
+//     pub fn decrement_visitor(&mut self) {
+//         if self.visitor_threshold > 0 {
+//             self.visitor_threshold -= 1;
+//         }
+//     }
+//
+//     /// get current difficulty factor
+//     pub fn get_difficulty(&self) -> u32 {
+//         self.defense.get_difficulty()
+//     }
+//
+//     /// get [Counter]'s lifetime
+//     pub fn get_duration(&self) -> u64 {
+//         self.duration
+//     }
+// }
 
-    /// decrements the visitor count by one
-    pub fn decrement_visitor(&mut self) {
-        if self.visitor_threshold > 0 {
-            self.visitor_threshold -= 1;
-        }
-    }
-
-    /// get current difficulty factor
-    pub fn get_difficulty(&self) -> u32 {
-        self.defense.get_difficulty()
-    }
-
-    /// get [Counter]'s lifetime
-    pub fn get_duration(&self) -> u64 {
-        self.duration
-    }
-}
 impl Actor for Counter {
     type Context = Context<Self>;
 }
@@ -148,7 +141,7 @@ struct DeleteVisitor;
 impl Handler<DeleteVisitor> for Counter {
     type Result = ();
     fn handle(&mut self, _msg: DeleteVisitor, _ctx: &mut Self::Context) -> Self::Result {
-        self.decrement_visitor();
+        self.0.decrement_visitor();
     }
 }
 
@@ -161,8 +154,8 @@ pub struct AddVisitor;
 impl AddVisitorResult {
     fn new(m: &Counter) -> Self {
         AddVisitorResult {
-            duration: m.get_duration(),
+            duration: m.0.get_duration(),
-            difficulty_factor: m.get_difficulty(),
+            difficulty_factor: m.0.get_difficulty(),
         }
     }
 }
@@ -174,7 +167,7 @@ impl Handler<AddVisitor> for Counter {
         let addr = ctx.address();
         use actix::clock::delay_for;
 
-        let duration: Duration = Duration::new(self.duration.clone(), 0);
+        let duration: Duration = Duration::new(self.0.get_duration(), 0);
         let wait_for = async move {
             //sleep(duration).await;
             delay_for(duration).await;
@@ -183,7 +176,7 @@ impl Handler<AddVisitor> for Counter {
         .into_actor(self);
         ctx.spawn(wait_for);
 
-        self.add_visitor();
+        self.0.add_visitor();
         MessageResult(AddVisitorResult::new(&self))
     }
 }
@@ -197,7 +190,7 @@ impl Handler<GetCurrentVisitorCount> for Counter {
     type Result = MessageResult<GetCurrentVisitorCount>;
 
     fn handle(&mut self, _: GetCurrentVisitorCount, _ctx: &mut Self::Context) -> Self::Result {
-        MessageResult(self.visitor_threshold)
+        MessageResult(self.0.get_visitors())
     }
 }
 

src/master/mod.rs

@@ -23,9 +23,14 @@ use derive_builder::Builder;
 use serde::{Deserialize, Serialize};
 
 pub mod embedded;
-
+#[allow(
-use crate::defense::Defense;
+    unused_variables,
-use crate::errors::*;
+    unused_imports,
+    unused_variables,
+    dead_code,
+    unused_macros
+)]
+use crate::mcaptcha::*;
 
 /// Describes actor handler trait impls that are required by a cache implementation
 pub trait Master: actix::Actor + actix::Handler<AddVisitor> + actix::Handler<AddSite> {}
@@ -53,60 +58,3 @@ pub struct AddSite {
     pub id: String,
     pub mcaptcha: MCaptcha,
 }
-
-/// Builder for [MCaptcha]
-#[derive(Clone, Serialize, Deserialize, Debug)]
-pub struct MCaptchaBuilder {
-    visitor_threshold: u32,
-    defense: Option<Defense>,
-    duration: Option<u64>,
-}
-
-impl Default for MCaptchaBuilder {
-    fn default() -> Self {
-        MCaptchaBuilder {
-            visitor_threshold: 0,
-            defense: None,
-            duration: None,
-        }
-    }
-}
-
-impl MCaptchaBuilder {
-    /// set defense
-    pub fn defense(&mut self, d: Defense) -> &mut Self {
-        self.defense = Some(d);
-        self
-    }
-
-    /// set duration
-    pub fn duration(&mut self, d: u64) -> &mut Self {
-        self.duration = Some(d);
-        self
-    }
-
-    /// Builds new [MCaptcha]
-    pub fn build(self: &mut MCaptchaBuilder) -> CaptchaResult<MCaptcha> {
-        if self.duration.is_none() {
-            Err(CaptchaError::PleaseSetValue("duration".into()))
-        } else if self.defense.is_none() {
-            Err(CaptchaError::PleaseSetValue("defense".into()))
-        } else if self.duration <= Some(0) {
-            Err(CaptchaError::CaptchaDurationZero)
-        } else {
-            let m = MCaptcha {
-                duration: self.duration.unwrap(),
-                defense: self.defense.clone().unwrap(),
-                visitor_threshold: self.visitor_threshold,
-            };
-            Ok(m)
-        }
-    }
-}
-
-#[derive(Clone, Serialize, Deserialize, Debug)]
-pub struct MCaptcha {
-    visitor_threshold: u32,
-    defense: Defense,
-    duration: u64,
-}

src/master/redis_master/mod.rs

@@ -0,0 +1,206 @@
+/*
+ * mCaptcha - A proof of work based DoS protection system
+ * Copyright © 2021 Aravinth Manivannan <realravinth@batsense.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+use actix::dev::*;
+use redis::cluster::ClusterClient;
+//use redis::cluster::ClusterConnection;
+use redis::Client;
+//use redis::Connection;
+use redis::RedisResult;
+use redis::{aio::Connection, cluster::ClusterConnection};
+
+//use crate::errors::*;
+use crate::master::{AddSite, AddVisitor, Master as MasterTrait};
+
+#[derive(Clone)]
+pub enum Redis {
+    Single(Client),
+    Cluster(ClusterClient),
+}
+
+pub enum RedisConnection {
+    Single(Connection),
+    Cluster(ClusterConnection),
+}
+
+const INCR: &str = "MCAPTCHA_CACHE.COUNT";
+const GET: &str = "MCAPTCHA_CACHE.GET";
+
+#[derive(Clone)]
+pub struct Master {
+    pub redis: Redis,
+}
+
+macro_rules! exec {
+    ($cmd:expr, $con:expr) => {
+        match $con {
+            RedisConnection::Single(mut con) => $cmd.query_async(&mut con).await,
+            RedisConnection::Cluster(mut con) => $cmd.query(&mut con),
+        }
+    };
+}
+
+impl Master {
+    async fn add_visitor(&mut self, key: &str) {
+        let mut cmd = redis::cmd(INCR);
+        cmd.arg(&[key]);
+        let a: RedisResult<usize> = exec!(cmd, self.get_connection().await);
+
+        unimplemented!("Have to check return types of INCR command")
+    }
+
+    async fn get_visitors(&mut self, key: &str) {
+        let mut cmd = redis::cmd(GET);
+        cmd.arg(&[key]);
+        let a: RedisResult<usize> = exec!(cmd, self.get_connection().await);
+
+        unimplemented!("Have to check return types of GET command")
+    }
+
+    async fn get_connection(&mut self) -> RedisConnection {
+        match &self.redis {
+            Redis::Single(c) => {
+                let con = c.get_async_connection().await.unwrap();
+                RedisConnection::Single(con)
+            }
+            Redis::Cluster(c) => {
+                let con = c.get_connection().unwrap();
+                RedisConnection::Cluster(con)
+            }
+        }
+    }
+
+    async fn module_is_loaded(&mut self) -> () {
+        let mut cmd = redis::cmd("COMMAND");
+        cmd.arg(&["INFO", INCR]);
+        let a: RedisResult<usize> = exec!(cmd, self.get_connection().await);
+
+        let mut cmd = redis::cmd("COMMAND");
+        cmd.arg(&["INFO", GET]);
+        let a: RedisResult<usize> = exec!(cmd, self.get_connection().await);
+
+        unimplemented!("Have to check return types of INFO command")
+    }
+}
+
+impl MasterTrait for Master {}
+
+impl Actor for Master {
+    type Context = Context<Self>;
+}
+
+impl Handler<AddVisitor> for Master {
+    type Result = MessageResult<AddVisitor>;
+
+    fn handle(&mut self, m: AddVisitor, ctx: &mut Self::Context) -> Self::Result {
+        let fut = async {
+            self.add_visitor(&m.0).await;
+        };
+        unimplemented!();
+    }
+}
+
+impl Handler<AddSite> for Master {
+    type Result = ();
+
+    fn handle(&mut self, m: AddSite, _ctx: &mut Self::Context) -> Self::Result {
+        unimplemented!();
+    }
+}
+
+//#[derive(Clone)]
+//pub struct Cluster(pub ClusterClient);
+//#[derive(Clone)]
+//pub struct Single(pub Client);
+//
+//pub trait Redis: 'static + Unpin + Clone {
+//    type Result;
+//    fn get_connection(&'static self) -> Self::Result;
+//}
+//impl Redis for Cluster {
+//    type Result = RedisResult<ClusterConnection>;
+//    fn get_connection(&self) -> Self::Result {
+//        self.0.get_connection()
+//    }
+//}
+//
+//impl Redis for Single {
+//    type Result = impl Future;
+//    fn get_connection(&'static self) -> Self::Result {
+//        self.0.get_async_connection()
+//    }
+//}
+
+//#[derive(Clone)]
+//pub struct Master {
+//    pub redis: usize,
+//}
+
+//impl MasterTrait for Master {}
+//
+//impl Actor for Master {
+//    type Context = Context<Self>;
+//}
+//
+//impl Handler<AddVisitor> for Master {
+//    type Result = MessageResult<AddVisitor>;
+//
+//    fn handle(&mut self, m: AddVisitor, ctx: &mut Self::Context) -> Self::Result {
+//        let fut = async {
+//            let test = "1";
+//        };
+//        unimplemented!();
+//    }
+//}
+//
+//impl Handler<AddSite> for Master {
+//    type Result = ();
+//
+//    fn handle(&mut self, m: AddSite, _ctx: &mut Self::Context) -> Self::Result {
+//        unimplemented!();
+//    }
+//}
+
+//pub struct Master<T: Redis> {
+//    pub redis: T,
+//}
+//
+//impl<T: Redis> MasterTrait for Master<T> {}
+//
+//impl<T: Redis> Actor for Master<T> {
+//    type Context = Context<Self>;
+//}
+//
+//impl<T: Redis> Handler<AddVisitor> for Master<T> {
+//    type Result = MessageResult<AddVisitor>;
+//
+//    fn handle(&mut self, m: AddVisitor, ctx: &mut Self::Context) -> Self::Result {
+//        let fut = async {
+//            self.redis.get_connection();
+//            let test = "1";
+//        };
+//        unimplemented!();
+//    }
+//}
+//
+//impl<T: Redis> Handler<AddSite> for Master<T> {
+//    type Result = ();
+//
+//    fn handle(&mut self, m: AddSite, _ctx: &mut Self::Context) -> Self::Result {
+//        unimplemented!();
+//    }
+//}

src/mcaptcha.rs

@@ -0,0 +1,118 @@
+/*
+ * mCaptcha - A proof of work based DoS protection system
+ * Copyright © 2021 Aravinth Manivannan <realravinth@batsense.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+use serde::{Deserialize, Serialize};
+
+use crate::defense::Defense;
+use crate::errors::*;
+
+/// Builder for [MCaptcha]
+#[derive(Clone, Serialize, Deserialize, Debug)]
+pub struct MCaptchaBuilder {
+    visitor_threshold: u32,
+    defense: Option<Defense>,
+    duration: Option<u64>,
+}
+
+impl Default for MCaptchaBuilder {
+    fn default() -> Self {
+        MCaptchaBuilder {
+            visitor_threshold: 0,
+            defense: None,
+            duration: None,
+        }
+    }
+}
+
+impl MCaptchaBuilder {
+    /// set defense
+    pub fn defense(&mut self, d: Defense) -> &mut Self {
+        self.defense = Some(d);
+        self
+    }
+
+    /// set duration
+    pub fn duration(&mut self, d: u64) -> &mut Self {
+        self.duration = Some(d);
+        self
+    }
+
+    /// Builds new [MCaptcha]
+    pub fn build(self: &mut MCaptchaBuilder) -> CaptchaResult<MCaptcha> {
+        if self.duration.is_none() {
+            Err(CaptchaError::PleaseSetValue("duration".into()))
+        } else if self.defense.is_none() {
+            Err(CaptchaError::PleaseSetValue("defense".into()))
+        } else if self.duration <= Some(0) {
+            Err(CaptchaError::CaptchaDurationZero)
+        } else {
+            let m = MCaptcha {
+                duration: self.duration.unwrap(),
+                defense: self.defense.clone().unwrap(),
+                visitor_threshold: self.visitor_threshold,
+            };
+            Ok(m)
+        }
+    }
+}
+
+#[derive(Clone, Serialize, Deserialize, Debug)]
+pub struct MCaptcha {
+    visitor_threshold: u32,
+    defense: Defense,
+    duration: u64,
+}
+
+impl MCaptcha {
+    /// increments the visitor count by one
+    #[inline]
+    pub fn add_visitor(&mut self) {
+        self.visitor_threshold += 1;
+        if self.visitor_threshold > self.defense.visitor_threshold() {
+            self.defense.tighten_up();
+        } else {
+            self.defense.loosen_up();
+        }
+    }
+
+    /// decrements the visitor count by one
+    #[inline]
+    pub fn decrement_visitor(&mut self) {
+        if self.visitor_threshold > 0 {
+            self.visitor_threshold -= 1;
+        }
+    }
+
+    /// get current difficulty factor
+    #[inline]
+    pub fn get_difficulty(&self) -> u32 {
+        self.defense.get_difficulty()
+    }
+
+    /// get [Counter]'s lifetime
+    #[inline]
+    pub fn get_duration(&self) -> u64 {
+        self.duration
+    }
+
+    /// get [Counter]'s current visitor_threshold
+    #[inline]
+    pub fn get_visitors(&self) -> u32 {
+        self.visitor_threshold
+    }
+}