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 physics MM functions.

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::physics::physics_mm::SPHSystem;
use crate::physics::physics_mm::{
    self,
};

#[derive(Deserialize)]
struct SphInput {
    system: SPHSystem,
    dt: f64,
}

/// Updates a Smoothed Particle Hydrodynamics (SPH) system by one time step via JSON serialization.
///
/// SPH is a meshfree Lagrangian method for simulating fluid dynamics by representing
/// the continuum as a set of particles with smoothed properties.
///
/// # Arguments
///
/// * `input` - A JSON string pointer containing:
///   - `system`: SPH system state (particles with positions, velocities, densities, etc.)
///   - `dt`: Time step size
///
/// # Returns
///
/// A C string pointer containing JSON-encoded `FfiResult<SPHSystem, String>` with
/// the updated SPH system state after time step.
///
/// # 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_physics_mm_sph_update_json(input: *const c_char) -> *mut c_char {
    let mut input: SphInput = match from_json_string(input) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<SPHSystem, String>::err(
                    "Invalid JSON".to_string(),
                ))
                .unwrap(),
            );
        },
    };

    input.system.update(input.dt);

    to_c_string(serde_json::to_string(&FfiResult::<SPHSystem, String>::ok(input.system)).unwrap())
}

/// Simulates a 2D dam break scenario using SPH method via JSON serialization.
///
/// Models the collapse of a water column and its subsequent flow, a classical
/// validation case for SPH fluid simulation.
///
/// # Returns
///
/// A C string pointer containing JSON-encoded `FfiResult<Vec<(f64, f64)>, String>` with
/// particle positions (x, y) after simulation.
///
/// # Safety
///
/// This function is unsafe because it returns a raw C string pointer that the
/// caller must free.
///
/// # 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_physics_mm_simulate_dam_break_json() -> *mut c_char {
    let res = physics_mm::simulate_dam_break_2d_scenario();

    to_c_string(serde_json::to_string(&FfiResult::<Vec<(f64, f64)>, String>::ok(res)).unwrap())
}