initial commit

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)
+    }
+}