Wrote program for Day 19

README.md

@@ -65,7 +65,7 @@ We encourage you to share your progress and ask questions in the Discussions sec
 | Day #16       | [Nim Game](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-16_Nim-Game)                              | :white_check_mark:      |
 | Day #17       | [Prison Break](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-17_Prison-Break)                          | :white_check_mark:      |
 | Day #18       | [Unique Paths](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-18_Unique-Paths)                          | :white_check_mark:      |
-| Day #19       | [URL Shortener](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-19_URL-Shortener)                         | :white_large_square:      |
+| Day #19       | [URL Shortener](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-19_URL-Shortener)                         | :white_check_mark:      |
 | Day #20       | [API Challenge](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-20_API-Challenge)                         | :white_large_square:      |
 | Day #21       | [Random Maze Generator](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-03/Day-21_Random-Maze-Generator)                 | :white_large_square:      |
 | Day #22       | [Marcio Mellos Challenge](https://github.com/LiveGray/100-Days-Of-Rust/tree/main/Week-04/Day-22_Marcio-Mellos-Challenge)               | :white_large_square:      |

Week-03/Day-19_URL-Shortener/day19/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day19"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

Week-03/Day-19_URL-Shortener/day19/src/lib.rs

@@ -0,0 +1,98 @@
+use std::time::{SystemTime, UNIX_EPOCH};
+
+fn valid_url(url: &str) -> Result<(), &str> {
+    if !url.starts_with("http://") && !url.starts_with("https://") {
+        Err("URL should start with either http:// or https://")
+    } else if url.contains(' ') {
+        Err("URL should not contain spaces")
+    } else if url.len() < 12 {
+        Err("URL should be at least 12 characters long")
+    } else if url.len() > 2048 {
+        Err("URL should not be longer than 2048 characters")
+    } else if url.contains('\n') {
+        Err("URL should not contain newlines")
+    } else {
+        Ok(())
+    }
+}
+
+pub fn url_shortener(url: &str, custom: Option<String>, rng: Option<Rng>) -> Result<String, &str> {
+    valid_url(url)?;
+
+    let domain = "https://shortener.rs/";
+
+    if let Some(custom) = custom {
+        Ok(format!("{}{}", domain, custom))
+    } else if let Some(mut rng) = rng {
+        Ok(format!("{}{}", domain, rng.random_string()))
+    } else {
+        Err("Either custom or rng should be provided")
+    }
+}
+
+pub struct Rng {
+    seed: u128,
+}
+
+impl Rng {
+    pub fn new() -> Rng {
+        let time_since_epoch = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .expect("Error in getting time")
+            .as_millis();
+        Rng {
+            seed: time_since_epoch,
+        }
+    }
+
+    pub fn random_string(&mut self) -> String {
+        let random_number = self.linear_congruent_generator(1103515245, 12345, 2u128.pow(31));
+        let binding = random_number.to_string();
+        let bytes = binding.as_bytes();
+        let (bytes, padding) = Rng::split_bits(bytes);
+        let alphabet =
+            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".as_bytes();
+        let mut result = String::new();
+        for b in bytes {
+            result.push(alphabet[b as usize] as char);
+        }
+        for _ in (0..padding).step_by(2) {
+            result.push('=');
+        }
+        result
+    }
+
+    fn split_bits(bytes: &[u8]) -> (Vec<u8>, usize) {
+        let mut bits = Vec::new();
+        for &byte in bytes {
+            for i in (0..8).rev() {
+                bits.push((byte >> i) & 1);
+            }
+        }
+        let mut result = Vec::new();
+        let mut padding = 0;
+        for chunk in bits.chunks(6) {
+            let mut byte = 0;
+            for (i, &bit) in chunk.iter().enumerate() {
+                byte |= bit << (5 - i);
+            }
+            result.push(byte);
+            if chunk.len() < 6 {
+                padding = 6 - chunk.len();
+            }
+        }
+        (result, padding)
+    }
+
+    fn linear_congruent_generator(&mut self, a: u128, c: u128, m: u128) -> u128 {
+        let result = (a * self.seed + c) % m;
+        self.seed = result;
+        result
+    }
+}
+
+impl Default for Rng {
+    fn default() -> Self {
+        Self::new()
+    }
+}

Week-03/Day-19_URL-Shortener/day19/src/main.rs

@@ -0,0 +1,45 @@
+use day19::{url_shortener, Rng};
+use std::io::{self, Write};
+
+fn main() {
+    let rng = Rng::new();
+    let mut buffer = String::new();
+
+    print!("Enter the URL to shorten: ");
+    io::stdout().flush().expect("Failed to flush stdout");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read from stdin");
+
+    let url = buffer.trim().to_owned();
+    buffer = String::new();
+
+    print!("Do you want to provide a custom short URL? (y/n): ");
+    io::stdout().flush().expect("Failed to flush stdout");
+
+    io::stdin()
+        .read_line(&mut buffer)
+        .expect("Failed to read from stdin");
+
+    let short_url = if buffer.trim() == "y" {
+        buffer = String::new();
+
+        print!("Enter the custom short URL: ");
+        io::stdout().flush().expect("Failed to flush stdout");
+
+        io::stdin()
+            .read_line(&mut buffer)
+            .expect("Failed to read from stdin");
+
+        let custom = Some(buffer.trim().to_string());
+        url_shortener(&url, custom, None)
+    } else {
+        url_shortener(&url, None, Some(rng))
+    };
+
+    match short_url {
+        Ok(short_url) => println!("Shortened URL: {}", short_url),
+        Err(e) => eprintln!("Error: {}", e),
+    }
+}