rssn 0.2.9

A comprehensive scientific computing library for Rust, aiming for feature parity with NumPy and SymPy.
Documentation 
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//! JSON-based FFI API for numerical topology.

use std::os::raw::c_char;

use serde::Deserialize;

use crate::ffi_apis::common::from_json_string;
use crate::ffi_apis::common::to_c_string;
use crate::ffi_apis::ffi_api::FfiResult;
use crate::numerical::topology::PersistenceDiagram;
use crate::numerical::topology::{
    self,
};

#[derive(Deserialize)]
struct BettiInput {
    points: Vec<Vec<f64>>,
    epsilon: f64,
    max_dim: usize,
}

/// Computes Betti numbers at a fixed radius for topological data analysis via JSON serialization.
///
/// Betti numbers characterize topological features: β₀ (connected components),
/// β₁ (holes/loops), β₂ (voids), etc., in the Vietoris-Rips complex.
///
/// # Arguments
///
/// * `input_json` - A JSON string pointer containing:
///   - `points`: Point cloud data as arrays of coordinates
///   - `epsilon`: Radius parameter for Vietoris-Rips complex
///   - `max_dim`: Maximum homology dimension to compute
///
/// # Returns
///
/// A C string pointer containing JSON-encoded `FfiResult<Vec<usize>, String>` with
/// a vector of Betti numbers [β₀, β₁, β₂, ...] up to `max_dim`.
///
/// # Safety
///
/// This function is unsafe because it receives a raw C string pointer that must be
/// valid, null-terminated UTF-8. The caller must free the returned pointer.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
///
/// # Panics
///
/// This function may panic if the FFI input is malformed, null where not expected,
/// or if internal state synchronization fails (e.g., poisoned locks).
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_topology_betti_numbers_json(
    input_json: *const c_char
) -> *mut c_char {
    let input: BettiInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<Vec<usize>, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let pt_slices: Vec<&[f64]> = input.points.iter().map(std::vec::Vec::as_slice).collect();

    let res = topology::betti_numbers_at_radius(&pt_slices, input.epsilon, input.max_dim);

    let ffi_res = FfiResult {
        ok: Some(res),
        err: None::<String>,
    };

    to_c_string(serde_json::to_string(&ffi_res).unwrap())
}

#[derive(Deserialize)]
struct PersistenceInput {
    points: Vec<Vec<f64>>,
    max_epsilon: f64,
    steps: usize,
    max_dim: usize,
}

/// Computes persistent homology for topological data analysis via JSON serialization.
///
/// Tracks the birth and death of topological features (components, holes, voids)
/// across multiple scales, producing persistence diagrams.
///
/// # Arguments
///
/// * `input_json` - A JSON string pointer containing:
///   - `points`: Point cloud data as arrays of coordinates
///   - `max_epsilon`: Maximum radius to analyze
///   - `steps`: Number of radius values to sample
///   - `max_dim`: Maximum homology dimension to compute
///
/// # Returns
///
/// A C string pointer containing JSON-encoded `FfiResult<Vec<PersistenceDiagram>, String>` with
/// persistence diagrams for each dimension.
///
/// # Safety
///
/// This function is unsafe because it receives a raw C string pointer that must be
/// valid, null-terminated UTF-8. The caller must free the returned pointer.
///
/// # Safety
///
/// This function is unsafe because it dereferences raw pointers as part of the FFI boundary.
/// The caller must ensure:
/// 1. All pointer arguments are valid and point to initialized memory.
/// 2. The memory layout of passed structures matches the expected C-ABI layout.
/// 3. Any pointers returned by this function are managed according to the API's ownership rules.
///
/// # Panics
///
/// This function may panic if the FFI input is malformed, null where not expected,
/// or if internal state synchronization fails (e.g., poisoned locks).
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_topology_persistence_json(
    input_json: *const c_char
) -> *mut c_char {
    let input: PersistenceInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<Vec<PersistenceDiagram>, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res =
        topology::compute_persistence(&input.points, input.max_epsilon, input.steps, input.max_dim);

    let ffi_res = FfiResult {
        ok: Some(res),
        err: None::<String>,
    };

    to_c_string(serde_json::to_string(&ffi_res).unwrap())
}