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```//! A libray for weighted balancing algorithm.
//! It provides three weighted balancing (elect) algorithm.
//! One is random algorithm.
//! Another is weighted balancing algorithm used by LVS.
//! The third is smooth weighted balancing algorithm used by Nginx.
//!
//! The LVS weighted round-robin scheduling is introduced at http://kb.linuxvirtualserver.org/wiki/Weighted_Round-Robin_Scheduling.
//! The Nginx smooth weighted round-robin balancing algorithm is introduced at https://github.com/phusion/nginx/commit/27e94984486058d73157038f7950a0a36ecc6e35.
//! The random algorithm is not smooth although it follows weight configuration.
//! Using it is simple:
//! ```rust
//!     use weighted_rs::{SmoothWeight, Weight};
//!     use std::collections::HashMap;
//!
//!     let mut sw: SmoothWeight<&str> = SmoothWeight::new();
//!
//!     let mut results: HashMap<&str, usize> = HashMap::new();
//!
//!     for _ in 0..100 {
//!         let s = sw.next().unwrap();
//!         println!("{}", s);
//!     }
//! ```

use std::collections::HashMap;

pub mod roundrobin_weight;
pub mod smooth_weight;

pub use roundrobin_weight::*;
pub use smooth_weight::*;

// A common trait for weight algorithm.
pub trait Weight {
type Item;

// next gets next selected item.
fn next(&mut self) -> Option<Self::Item>;
// add adds a weighted item for selection.
fn add(&mut self, item: Self::Item, weight: isize);

// all returns all items.
fn all(&self) -> HashMap<Self::Item, isize>;

// remove_all removes all weighted items.
fn remove_all(&mut self);

// reset resets the balancing algorithm.
fn reset(&mut self);
}
```