rssn 0.2.9

//! Bincode-based FFI API for numerical differential geometry.

use serde::Deserialize;

use crate::ffi_apis::common::BincodeBuffer;
use crate::ffi_apis::common::from_bincode_buffer;
use crate::ffi_apis::common::to_bincode_buffer;
use crate::ffi_apis::ffi_api::FfiResult;
use crate::numerical::differential_geometry;
use crate::symbolic::coordinates::CoordinateSystem;

#[derive(Deserialize)]
struct DgPointInput {
    system: CoordinateSystem,
    point: Vec<f64>,
}

/// Computes the metric tensor at a given point using bincode for serialization.
///
/// # 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.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_dg_metric_tensor_bincode(buffer: BincodeBuffer) -> BincodeBuffer {
    let input: DgPointInput = match from_bincode_buffer(&buffer) {
        | Some(i) => i,
        | None => {
            return to_bincode_buffer(&FfiResult::<Vec<Vec<f64>>, String> {
                ok: None,
                err: Some("Invalid Bincode input".to_string()),
            });
        },
    };

    match differential_geometry::metric_tensor_at_point(input.system, &input.point) {
        | Ok(res) => {
            let ffi_res = FfiResult {
                ok: Some(res),
                err: None::<String>,
            };

            to_bincode_buffer(&ffi_res)
        },
        | Err(e) => {
            let ffi_res = FfiResult {
                ok: None::<Vec<Vec<f64>>>,
                err: Some(e),
            };

            to_bincode_buffer(&ffi_res)
        },
    }
}

/// Computes the Christoffel symbols at a given point using bincode for serialization.
///
/// # 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.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_dg_christoffel_symbols_bincode(
    buffer: BincodeBuffer
) -> BincodeBuffer {
    let input: DgPointInput = match from_bincode_buffer(&buffer) {
        | Some(i) => i,
        | None => {
            return to_bincode_buffer(&FfiResult::<Vec<Vec<Vec<f64>>>, String> {
                ok: None,
                err: Some("Invalid Bincode input".to_string()),
            });
        },
    };

    match differential_geometry::christoffel_symbols(input.system, &input.point) {
        | Ok(res) => {
            let ffi_res = FfiResult {
                ok: Some(res),
                err: None::<String>,
            };

            to_bincode_buffer(&ffi_res)
        },
        | Err(e) => {
            let ffi_res = FfiResult {
                ok: None::<Vec<Vec<Vec<f64>>>>,
                err: Some(e),
            };

            to_bincode_buffer(&ffi_res)
        },
    }
}

/// Computes the Ricci tensor at a given point using bincode for serialization.
///
/// # 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.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_dg_ricci_tensor_bincode(buffer: BincodeBuffer) -> BincodeBuffer {
    let input: DgPointInput = match from_bincode_buffer(&buffer) {
        | Some(i) => i,
        | None => {
            return to_bincode_buffer(&FfiResult::<Vec<Vec<f64>>, String> {
                ok: None,
                err: Some("Invalid Bincode input".to_string()),
            });
        },
    };

    match differential_geometry::ricci_tensor(input.system, &input.point) {
        | Ok(res) => {
            let ffi_res = FfiResult {
                ok: Some(res),
                err: None::<String>,
            };

            to_bincode_buffer(&ffi_res)
        },
        | Err(e) => {
            let ffi_res = FfiResult {
                ok: None::<Vec<Vec<f64>>>,
                err: Some(e),
            };

            to_bincode_buffer(&ffi_res)
        },
    }
}

/// Computes the Ricci scalar at a given point using bincode for serialization.
///
/// # 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.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn rssn_num_dg_ricci_scalar_bincode(buffer: BincodeBuffer) -> BincodeBuffer {
    let input: DgPointInput = match from_bincode_buffer(&buffer) {
        | Some(i) => i,
        | None => {
            return to_bincode_buffer(&FfiResult::<f64, String> {
                ok: None,
                err: Some("Invalid Bincode input".to_string()),
            });
        },
    };

    match differential_geometry::ricci_scalar(input.system, &input.point) {
        | Ok(res) => {
            let ffi_res = FfiResult {
                ok: Some(res),
                err: None::<String>,
            };

            to_bincode_buffer(&ffi_res)
        },
        | Err(e) => {
            let ffi_res = FfiResult {
                ok: None::<f64>,
                err: Some(e),
            };

            to_bincode_buffer(&ffi_res)
        },
    }
}