hard-coded single reservoir

/// Simulates a cascade of reservoirs

#[pyfunction]

fn simulate_cascade(inflow: Vec<f64>, release: Vec<f64>) -> PyResult<Vec<f64>> {

fn simulate_cascade(inflow: Vec<f64>, release: Vec<f64>) -> PyResult<(Vec<f64>, Vec<f64>, Vec<f64>)> {

    // Reservoir specifications

    const CAPACITY: f64 = 100.0;  // Maximum storage in MCM (Million cubic meters)

    const INITIAL_STORAGE: f64 = 50.0;  // Initial storage in MCM

    const MAX_RELEASE: f64 = 15.0;  // Maximum release per timestep in MCM

    const MIN_RELEASE: f64 = 3.0;  // Minimum release per timestep in MCM

    if inflow.len() != release.len() {

        return Err(PyValueError::new_err("Input vectors must have the same length"));

    }

    // placeholder: sums inflow and release to return single vector

    let n = inflow.len();

    let mut storage = vec![0.0; n];  // Storage at end of timestep

    let mut actual_release = vec![0.0; n];  // Actual release for timestep

    let mut spill = vec![0.0; n];  // Spill for timestep

    // Initialize first timestep storage

    storage[0] = INITIAL_STORAGE;

    for t in 0..n {

        let available_water = if t == 0 {

            INITIAL_STORAGE + inflow[t]

        } else {

            storage[t-1] + inflow[t]

        };

        // Calculate actual release (constrained by available water and max/min release)

        actual_release[t] = release[t]

            .max(MIN_RELEASE)  // Ensure we meet minimum release

            .min(MAX_RELEASE)  // Cannot exceed maximum release

            .min(available_water);  // Cannot release more than available

        // Calculate new storage

        let potential_storage = available_water - actual_release[t];

        // Calculate spill if storage would exceed capacity

        if potential_storage > CAPACITY {

            storage[t] = CAPACITY;

            spill[t] = potential_storage - CAPACITY;

        } else {

            storage[t] = potential_storage;

            spill[t] = 0.0;

        }

    }

    Ok(inflow.iter().zip(release.iter()).map(|(x, y)| x + y).collect())

    Ok((storage, actual_release, spill))

}