## lunch_queue
### Instructions
You will need to create an *API* , so that a program can organize a queue of people.
The program requires the following functions. Add them as associated functions to the `Queue` structure:
- `new` : which will initialize the `Queue` .
- `add` : which adds a person to the queue.
- `invert_queue` : which reverses the queue.
- `rm` : which removes the person who finished ordering their food. The removal should respect the FIFO method (first in first out). It should return the person's details.
- `search` : which returns the details for a given person's `name` .
You must also create a type named `Link` . This will be the connection of the structures `Queue` and `Person` . This will be a recursion type, and must point to `None` if there is no `Person` to point to.
### Expected Function and Structures
```rust
pub struct Queue {
pub node: Link,
}
pub type Link =
pub struct Person {
pub discount: i32,
pub name: String,
}
impl Queue {
pub fn new() -> Queue {
}
pub fn add(& mut self, name: String, discount: i32) {
}
pub fn invert_queue(& mut self) {
}
pub fn rm(& mut self) -> Option< (String, i32)> {
}
pub fn search(& self, name: & str) -> Option< (String, i32)> {
}
}
```
### Usage
Here is a program to test your function:
```rust
fn main() {
let mut list = Queue::new();
list.add(String::from("Marie"), 20);
list.add(String::from("Monica"), 15);
list.add(String::from("Ana"), 5);
list.add(String::from("Alice"), 35);
println!("{:?}", list);
println!("{:?}", list.search("Marie"));
println!("{:?}", list.search("Alice"));
println!("{:?}", list.search("someone"));
println!("removed {:?}", list.rm());
println!("list {:?}", list);
list.invert_queue();
println!("invert {:?}", list);
}
```
And its output:
```console
$ cargo run
Queue { node: Some(Person { name: "Alice", discount: 35, next_person: Some(Person { name: "Ana", discount: 5, next_person: Some(Person { name: "Monica", discount: 15, next_person: Some(Person { name: "Marie", discount: 20, next_person: None }) }) }) }) }
Some(("Marie", 20))
Some(("Alice", 35))
None
removed Some(("Marie", 20))
list Queue { node: Some(Person { name: "Alice", discount: 35, next_person: Some(Person { name: "Ana", discount: 5, next_person: Some(Person { name: "Monica", discount: 15, next_person: None }) }) }) }
invert Queue { node: Some(Person { name: "Monica", discount: 15, next_person: Some(Person { name: "Ana", discount: 5, next_person: Some(Person { name: "Alice", discount: 35, next_person: None }) }) }) }
$
```
### Notions
- [enum ](https://doc.rust-lang.org/rust-by-example/custom_types/enum.html )
- [Box ](https://doc.rust-lang.org/book/ch15-01-box.html )
- [std::option ](https://doc.rust-lang.org/std/option/ )
