lancedb/python/src/util.rs

use std::sync::Mutex;

use lancedb::DistanceType;
use pyo3::{
    exceptions::{PyRuntimeError, PyValueError},
    pyfunction, PyResult,
};

/// A wrapper around a rust builder
///
/// Rust builders are often implemented so that the builder methods
/// consume the builder and return a new one. This is not compatible
/// with the pyo3, which, being garbage collected, cannot easily obtain
/// ownership of an object.
///
/// This wrapper converts the compile-time safety of rust into runtime
/// errors if any attempt to use the builder happens after it is consumed.
pub struct BuilderWrapper<T> {
    name: String,
    inner: Mutex<Option<T>>,
}

impl<T> BuilderWrapper<T> {
    pub fn new(name: impl AsRef<str>, inner: T) -> Self {
        Self {
            name: name.as_ref().to_string(),
            inner: Mutex::new(Some(inner)),
        }
    }

    pub fn consume<O>(&self, mod_fn: impl FnOnce(T) -> O) -> PyResult<O> {
        let mut inner = self.inner.lock().unwrap();
        let inner_builder = inner.take().ok_or_else(|| {
            PyRuntimeError::new_err(format!("{} has already been consumed", self.name))
        })?;
        let result = mod_fn(inner_builder);
        Ok(result)
    }
}

pub fn parse_distance_type(distance_type: impl AsRef<str>) -> PyResult<DistanceType> {
    match distance_type.as_ref().to_lowercase().as_str() {
        "l2" => Ok(DistanceType::L2),
        "cosine" => Ok(DistanceType::Cosine),
        "dot" => Ok(DistanceType::Dot),
        _ => Err(PyValueError::new_err(format!(
            "Invalid distance type '{}'.  Must be one of l2, cosine, or dot",
            distance_type.as_ref()
        ))),
    }
}

#[pyfunction]
pub fn validate_table_name(table_name: &str) -> PyResult<()> {
    lancedb::utils::validate_table_name(table_name)
        .map_err(|e| PyValueError::new_err(e.to_string()))
}