# Lookups [![Build Status]][Build Action] [![Coverage Status]][Coverage Action][![Latest Version]][crates.io]  

[Build Status]: https://github.com/lima1909/lookups/actions/workflows/continuous_integration.yml/badge.svg
[Build Action]: https://github.com/lima1909/lookups/actions
[Coverage Status]: https://codecov.io/gh/lima1909/lookups/branch/main/graph/badge.svg?token=VO3VV8BFLN
[Coverage Action]: https://codecov.io/gh/lima1909/lookups
[Latest Version]: https://img.shields.io/crates/v/lookups.svg
[crates.io]: https://crates.io/crates/lookups


Improve the data retrieval operations for collections.

# Overview

__lookups__ is a crate for extending already existing collections (`std::vec::Vec`, `std::collections::HashMap`, ...)
with additional lookup functionalities, so you have a faster access to your data as with an `iterator` or a `search algorithm`.
This wrapper is just as easy to use as the given (original) collection.

The fast access can be achieved by using different methods, like;

- hash tables
- indexing
- ...

### Disadvantage

- it is more memory required. In addition to the user data, data for the _hash_, _index_ are also stored.
- the write operation are slower, because for every wirte operation is an another one (for storing the lookup data) necessary

### How can I use it?

```rust
use lookups::{LkupHashMap, IndexLookup, Lookup};

#[derive(PartialEq, Debug)]
struct Car {
    id: usize,
    name: String,
}

// create a new Lookup HashMap with a unique lookup `Key`: `Car::id` (usize)
let mut map = LkupHashMap::new(IndexLookup::with_unique_key() ,|c: &Car| c.id);

map.insert(String::from("BMW"),  Car{id: 0, name: "BMW".into()});
map.insert(String::from("Audi"), Car{id: 5, name: "Au".into()});
map.insert(String::from("VW"),   Car{id: 2, name: "VW".into()});

// conventionally HashMap access with Key (name: String)
assert!(map.contains_key("VW"));
// lookup with Key (id: usize)
assert!(map.contains_lkup_key(2));

// update one entry by lookup-key
assert_eq!(1, map.update_by_key(5, |c| c.name = "Audi".into()));

// get a Car by an given: id
assert_eq!(Some(&Car{id: 5, name: "Audi".into()}), map.get_by_lkup_key(5).next());


// create a View: a subset from the Lookups (defined by the given Keys)
let view = map.create_lkup_view([0, 2]);

assert_eq!(Some(&Car{id: 0, name: "BMW".into()}), view.get_by_key(0).next());
assert_eq!(vec![&Car{id: 0, name: "BMW".into()}, &Car{id: 2, name: "VW".into()}],
           view.items().collect::<Vec<_>>());

// get min and max key
assert_eq!(Some(0), view.min_key());
assert_eq!(Some(2), view.max_key());
```
