tanzim-validate 0.1.0

use crate::Validator;
use crate::error::{Error, ErrorKind};
use tanzim_value::{Value, ValueType};

/// Accepts a human byte-size string (e.g. `"10MB"`, `"1GiB"`) and coerces it to an integer
/// number of bytes.
#[derive(Debug, Clone, Default)]
pub struct ByteSize;

impl ByteSize {
    pub fn new() -> Self {
        Self
    }
}

impl Validator for ByteSize {
    fn validate(&self, value: &mut Value) -> Result<(), Error> {
        let text = match value {
            Value::String(text) => text,
            other => {
                return Err(Error::new(ErrorKind::Type {
                    expected: ValueType::String,
                    found: other.type_name(),
                }));
            }
        };

        let parsed = match text.parse::<bytesize::ByteSize>() {
            Ok(parsed) => parsed,
            Err(_) => {
                return Err(Error::new(ErrorKind::Format {
                    expected: "byte size",
                }));
            }
        };

        let coerced = match isize::try_from(parsed.as_u64()) {
            Ok(coerced) => coerced,
            Err(_) => {
                return Err(Error::new(ErrorKind::NotConvertible {
                    target: ValueType::Int,
                    found: ValueType::String,
                }));
            }
        };

        *value = Value::Int(coerced);
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn coerces_to_bytes() {
        let mut value = Value::String("10 KB".into());
        ByteSize::new().validate(&mut value).unwrap();
        assert_eq!(value, Value::Int(10_000));
    }

    #[test]
    fn rejects_garbage() {
        let mut value = Value::String("lots".into());
        assert!(ByteSize::new().validate(&mut value).is_err());
    }
}