use params::{Map, Value};
pub fn validate_alpha(values: &Map, field: &str) -> Result<Option<Value>, String> {
match values.find(&[field]) {
Some(&Value::String(ref value)) => {
if value.is_empty() {
return Ok(None);
}
if value.chars().filter(|c| !c.is_alphabetic()).count() == 0 {
return Ok(None);
}
Err(format!("The {} field may only contain alphabetic characters.",
field.to_lowercase().replace("_", " ")))
}
None => {
Ok(None)
}
_ => {
Err(format!("The {} field may only contain alphabetic characters.",
field.to_lowercase().replace("_", " ")))
}
}
}