From fcf882991c2de0b456e58f20259d88f1c71ec048 Mon Sep 17 00:00:00 2001
From: Felix Martin <mail@felixm.de>
Date: Thu, 24 Mar 2022 23:16:17 -0400
Subject: [PATCH] Complete set 1 challenge 1.

---
 src/main.rs | 18 ++++++++++++---
 src/set1.rs | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 79 insertions(+), 5 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index a70d659..2017116 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,8 +1,20 @@
 mod set1;
 
-use crate::set1::convert_hex_to_base64;
+use crate::set1::{base64_to_string, bytes_to_base64, to_bytes};
+
+fn test_set1() {
+    let input = to_bytes("49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d");
+    let expected = String::from("SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t");
+    match input {
+        Ok(bytes) => {
+            let output = base64_to_string(bytes_to_base64(bytes));
+            assert_eq!(output, expected);
+            println!("{:?}", output);
+        }
+        Err(e) => println!("Error: {:?}", e),
+    };
+}
 
 fn main() {
-    println!("Hello, world! Does it work?");
-    convert_hex_to_base64();
+    test_set1();
 }
diff --git a/src/set1.rs b/src/set1.rs
index 9e63ab5..1112a96 100644
--- a/src/set1.rs
+++ b/src/set1.rs
@@ -1,3 +1,65 @@
-pub fn convert_hex_to_base64() {
-    println!("We are here too.");
+use std::num::ParseIntError;
+use std::str;
+
+pub fn to_bytes(s: &str) -> Result<Vec<u8>, String> {
+    if s.len() % 2 != 0 {
+        return Err(String::from("Input string has uneven number of characters"));
+    }
+
+    let bytes_result: Result<Vec<u8>, ParseIntError> = (0..s.len())
+        .step_by(2)
+        .map(|i| u8::from_str_radix(&s[i..i + 2], 16))
+        .collect();
+
+    match bytes_result {
+        Ok(b) => Ok(b),
+        Err(_) => Err(String::from("Could not convert all digit pairs to hex.")),
+    }
+}
+
+fn chunk_to_base64(c: &[u8]) -> Vec<u8> {
+    let (value, iterations) = match c.len() {
+        0 => return vec![],
+        1 => ((c[0] as u32) << 16, 2),
+        2 => ((c[0] as u32) << 16 | (c[1] as u32) << 8, 3),
+        3 => ((c[0] as u32) << 16 | (c[1] as u32) << 8 | (c[2] as u32), 4),
+        _ => panic!("Unexpected number of chunks {}.", c.len()),
+    };
+    (0..iterations)
+        .map(|i| (value.rotate_right((3 - i) * 6) & 0b111111) as u8)
+        .collect()
+}
+
+pub fn bytes_to_base64(bytes: Vec<u8>) -> Vec<u8> {
+    bytes
+        .chunks(3)
+        .map(|c| chunk_to_base64(c))
+        .flatten()
+        .collect()
+}
+
+pub fn base64_to_string(digits: Vec<u8>) -> String {
+    let mut r: Vec<u8> = digits
+        .iter()
+        .map(|d| match d {
+            0..=25 => *d + ('A' as u8),
+            26..=51 => *d - 26 + ('a' as u8),
+            52..=61 => *d - 52 + ('0' as u8),
+            62 => '+' as u8,
+            63 => '/' as u8,
+            _ => panic!("Unexpected base64 digit '{}'", d),
+        })
+        .collect();
+    // Handle padding
+    let pad = '=' as u8;
+    match r.len() % 4 {
+        0 => (),
+        2 => {
+            r.push(pad);
+            r.push(pad);
+        }
+        3 => r.push(pad),
+        _ => (),
+    }
+    str::from_utf8(r.as_slice()).unwrap().to_string()
 }