commit 5c87600c56d6fcd08a0c2295fc856c246a2bb7f6
Author: lionarius <main@lionarius.ru>
Date:   Tue Sep 3 14:30:19 2024 +0300

    initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..c264c38
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,16 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "anyhow"
+version = "1.0.86"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3d1d046238990b9cf5bcde22a3fb3584ee5cf65fb2765f454ed428c7a0063da"
+
+[[package]]
+name = "information-security"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+]
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..0ef143e
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "information-security"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1.0.86"
diff --git a/src/atbash.rs b/src/atbash.rs
new file mode 100644
index 0000000..865fe36
--- /dev/null
+++ b/src/atbash.rs
@@ -0,0 +1,34 @@
+use crate::util;
+
+pub struct AtabashChipher {
+    alphabet: Vec<char>,
+}
+
+impl AtabashChipher {
+    pub fn new(alphabet: impl Into<Vec<char>>) -> anyhow::Result<Self> {
+        let alphabet = alphabet.into();
+
+        util::verify_alphabet(&alphabet)?;
+
+        Ok(Self { alphabet })
+    }
+
+    pub fn encode(&self, input: &str) -> anyhow::Result<String> {
+        let mut output = String::with_capacity(input.len());
+
+        for c in input.chars() {
+            let index = self
+                .alphabet
+                .iter()
+                .position(|&x| x == c)
+                .ok_or(anyhow::anyhow!("cannot encode character {:?}", c))?;
+            output.push(self.alphabet[self.alphabet.len() - index - 1]);
+        }
+
+        Ok(output)
+    }
+
+    pub fn decode(&self, input: &str) -> anyhow::Result<String> {
+        self.encode(input)
+    }
+}
diff --git a/src/caesar.rs b/src/caesar.rs
new file mode 100644
index 0000000..ce17476
--- /dev/null
+++ b/src/caesar.rs
@@ -0,0 +1,56 @@
+use crate::util;
+
+pub struct CaesarCipher {
+    alphabet: Vec<char>,
+    offset: i64,
+}
+
+impl CaesarCipher {
+    pub fn new(alphabet: impl Into<Vec<char>>, offset: i64) -> anyhow::Result<Self> {
+        let alphabet = alphabet.into();
+        let offset = offset % alphabet.len() as i64;
+
+        util::verify_alphabet(&alphabet)?;
+
+        Ok(Self { alphabet, offset })
+    }
+
+    pub fn encode(&self, input: &str) -> anyhow::Result<String> {
+        let mut output = String::with_capacity(input.len());
+
+        for c in input.chars() {
+            let index = self.get_index(c, self.offset)?;
+            output.push(self.alphabet[index])
+        }
+
+        Ok(output)
+    }
+
+    pub fn decode(&self, input: &str) -> anyhow::Result<String> {
+        let mut output = String::with_capacity(input.len());
+
+        for c in input.chars() {
+            let index = self.get_index(c, -self.offset)?;
+            output.push(self.alphabet[index])
+        }
+
+        Ok(output)
+    }
+
+    fn get_index(&self, c: char, offset: i64) -> anyhow::Result<usize> {
+        let mut index =
+            self.alphabet
+                .iter()
+                .position(|&x| x == c)
+                .ok_or(anyhow::anyhow!("cannot encode character {:?}", c))? as i64
+                + offset;
+
+        while index < 0 {
+            index += self.alphabet.len() as i64;
+        }
+
+        index %= self.alphabet.len() as i64;
+
+        Ok(index as usize)
+    }
+}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..8dd1d3e
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,14 @@
+mod atbash;
+mod caesar;
+mod util;
+
+fn main() -> anyhow::Result<()> {
+    let alphabet = "абвгдежзиклмнопрстуфхцчшщъыьэюя"
+        .chars()
+        .collect::<Vec<_>>();
+    let encoder = caesar::CaesarCipher::new(alphabet, 1)?;
+    println!("{}", encoder.encode("абвгд")?);
+    println!("{}", encoder.decode("бвгде")?);
+
+    Ok(())
+}
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..00c33b2
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,17 @@
+pub fn verify_alphabet(alphabet: &[char]) -> anyhow::Result<()> {
+    if alphabet.len() < 2 {
+        return Err(anyhow::anyhow!(
+            "Alphabet must contain at least 2 characters"
+        ));
+    }
+
+    let mut alphabet_set = std::collections::HashSet::new();
+    for c in alphabet {
+        if alphabet_set.contains(c) {
+            return Err(anyhow::anyhow!("Alphabet contains duplicate characters"));
+        }
+        alphabet_set.insert(*c);
+    }
+
+    Ok(())
+}