docs(unwrap_or_expect): rewrite the subject

Rewrite the subject completely to give more meaninful learning experience to students.

subjects/unwrap_or_expect/README.md

@@ -2,45 +2,31 @@
 
 ### Instructions
 
-A **function** named **odd_to_even** will be given, which returns a `Result`. If there is an even value in the vector, the function will return a tuple with a string, stating the error, and a vector with the elements that caused the error.
+Create a **function** named **fetch_data** which has two arguments:
+- `server`: Which is a `Result` having the server url or an error message inside.
+- `security_level`: Which is an `enum` defining the behavior of the function in case of errors.
 
-The objective is to execute the `odd_to_even` function and handle the errors returned by it.
+The `security_level` will work as follow:
+- `Unknown`: The function panics without printing any custom message.
+- `High`: The function panics and prints the error message `ERROR: program stops`.
+- `Medium`: The function returns the string `WARNING: check the server`.
+- `Low`: The function returns the string `Not found: [SERVER_URL]`.
+- `BlockServer`: The function will panic only if the `Result` value is `Ok` and the error message will be the string contained in `Ok`.
 
-Create the following functions which receive a vector:
+To return from **fetch_data** you must use `expect`, `unwrap_or`, `unwrap_err`, `unwrap` and `unwrap_or_else`.
-
-- `expect`: which returns the error adding the string "ERROR " to the beginning.
-- `unwrap_or`: which in case of error, returns an empty vector.
-- `unwrap_err`: which panics if the value is `Ok`, or returns the string containing the error in case of `Err`.
-- `unwrap`: which unwraps the `Result`.
-- `unwrap_or_else`: which in case of error returns the vector of elements that caused the error.
 
 ### Expected Functions
 
 ```rust
-pub fn odd_to_even(data: Vec<u32>) -> Result<Vec<u32>, (String, Vec<u32>)> {
+pub enum Security {
-    let mut a = Vec::new();
+	Unknown,
-    a.extend(data.iter().filter(|&value| value % 2 == 0));
+	High,
-    if a.len() != 0 {
+	Medium,
-        return Err(("There is a even value in the vector!".to_string(), a));
+	Low,
-    }
+	BlockServer,
-    a.extend(data.iter().map(|&value| {
-        value + 1
-    }));
-    Ok(a)
-}
-pub fn expect(v: Vec<u32>) -> Vec<u32> {
-
 }
-pub fn unwrap_or(v: Vec<u32>) -> Vec<u32> {
 
-}
+pub fn fetch_data(server: Result<String, String>, security_level: Security) -> String {
-pub fn unwrap_err(v: Vec<u32>) -> (String, Vec<u32>) {
-
-}
-pub fn unwrap(v: Vec<u32>) -> Vec<u32> {
-
-}
-pub fn unwrap_or_else(v: Vec<u32>) -> Vec<u32> {
 
 }
 ```
@@ -53,38 +39,27 @@ Here is a program to test your function:
 use unwrap_or_expect::*;
 
 fn main() {
-    // // if uncommented, the below line will give an expect "ERROR "
+    println!("{}", fetch_data(Ok("server1.com".to_string()), Security::Medium));
-    // println!("{:?}", expect(vec![1, 3, 2, 5]));
+    println!("{}", fetch_data(Err(String::new()), Security::Medium));
-
+    println!("{}", fetch_data(Err("server2.com".to_string()), Security::Low));
-    println!("{:?}", unwrap_or(vec![1, 3, 2, 5]));
-    println!("{:?}", unwrap_or(vec![1, 3, 5]));
-
-    println!("{:?}", unwrap_err(vec![1, 3, 2, 5]));
-
-    // // if uncommented, the below line will give an unwraped error
-    // println!("{:?}", unwrap_err(vec![1, 3, 5]));
 
-    println!("{:?}", unwrap(vec![1, 3, 5]));
+    // Panics with no custom message
+    // fetch_data(Err("ERROR CRITICAL".to_string()), Security::Unknown);
 
-    //// if uncommented, the below line will give an error
+    // Panics with the message "ERROR: program stops"
-    // println!("{:?}", unwrap(vec![1, 3, 2, 5]));
+    // fetch_data(Err(String::new()), Security::High);
 
-    println!("{:?}", unwrap_or_else(vec![1, 3, 5]));
+    // Panics with the message "malicious_server.com"
-    println!("{:?}", unwrap_or_else(vec![3, 2, 6, 5]));
+    // fetch_data(Ok("malicious_server.com".to_string()), Security::BlockServer);
 }
 ```
 
 And its output:
 
 ```console
-[]
+server1.com
-[2, 4, 6]
+WARNING: check the server
-("There is a even value in the vector!", [2])
+Not found: server2.com
-[2, 4, 6]
-Ok([2, 4, 6])
-[2, 4, 6]
-Err(("There is a even value in the vector!", [2, 6]))
-[2, 6]
 $
 ```