Copy euph-api-related parts from cove

Also includes the required dependencies and some minor changes to the
module structure, as well as all the clippy and rustc warnings.

src/huehash.rs

@@ -0,0 +1,32 @@
+fn normalize(text: &str) -> String {
+    // TODO Remove emoji names?
+    text.chars()
+        .filter(|&c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
+        .map(|c| c.to_ascii_lowercase())
+        .collect()
+}
+
+/// A re-implementation of [euphoria's nick hue hashing algorithm][0].
+///
+/// [0]: https://github.com/euphoria-io/heim/blob/master/client/lib/hueHash.js
+fn hue_hash(text: &str, offset: i64) -> u8 {
+    let mut val = 0_i32;
+    for bibyte in text.encode_utf16() {
+        let char_val = (bibyte as i32).wrapping_mul(439) % 256;
+        val = val.wrapping_mul(33).wrapping_add(char_val);
+    }
+
+    let val: i64 = val as i64 + 2_i64.pow(31);
+    ((val + offset) % 255) as u8
+}
+
+const GREENIE_OFFSET: i64 = 148 - 192; // 148 - hue_hash("greenie", 0)
+
+pub fn nick_hue(nick: &str) -> u8 {
+    let normalized = normalize(nick);
+    if normalized.is_empty() {
+        hue_hash(nick, GREENIE_OFFSET)
+    } else {
+        hue_hash(&normalized, GREENIE_OFFSET)
+    }
+}