rssn 0.2.9

//! JSON-based FFI API for numerical combinatorics.

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::combinatorics;

#[derive(Deserialize)]
struct NInput {
    n: u64,
}

#[derive(Deserialize)]
struct NKInput {
    n: u64,
    k: u64,
}

#[derive(Deserialize)]
struct RecurrenceInput {
    coeffs: Vec<f64>,
    initial_conditions: Vec<f64>,
    target_n: usize,
}

/// Computes the factorial of a number using JSON 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.
///
/// # 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_comb_factorial_json(input_json: *const c_char) -> *mut c_char {
    let input: NInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::factorial(input.n);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Computes the number of permutations using JSON 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.
///
/// # 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_comb_permutations_json(input_json: *const c_char) -> *mut c_char {
    let input: NKInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::permutations(input.n, input.k);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Computes the number of combinations using JSON 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.
///
/// # 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_comb_combinations_json(input_json: *const c_char) -> *mut c_char {
    let input: NKInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::combinations(input.n, input.k);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Solves a linear recurrence relation using JSON 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.
///
/// # 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_comb_solve_recurrence_json(
    input_json: *const c_char
) -> *mut c_char {
    let input: RecurrenceInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    match combinatorics::solve_recurrence_numerical(
        &input.coeffs,
        &input.initial_conditions,
        input.target_n,
    ) {
        | Ok(res) => {
            to_c_string(
                serde_json::to_string(&FfiResult {
                    ok: Some(res),
                    err: None::<String>,
                })
                .unwrap(),
            )
        },
        | Err(e) => {
            to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some(e),
                })
                .unwrap(),
            )
        },
    }
}

#[derive(Deserialize)]
struct XNInput {
    x: f64,
    n: u64,
}

/// Computes the Stirling number of the second kind using JSON 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.
///
/// # 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_comb_stirling_second_json(
    input_json: *const c_char
) -> *mut c_char {
    let input: NKInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::stirling_second(input.n, input.k);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Computes the Bell number using JSON 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.
///
/// # 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_comb_bell_json(input_json: *const c_char) -> *mut c_char {
    let input: NInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::bell(input.n);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Computes the Catalan number using JSON 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.
///
/// # 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_comb_catalan_json(input_json: *const c_char) -> *mut c_char {
    let input: NInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::catalan(input.n);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Computes the rising factorial using JSON 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.
///
/// # 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_comb_rising_factorial_json(
    input_json: *const c_char
) -> *mut c_char {
    let input: XNInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::rising_factorial(input.x, input.n);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}

/// Computes the falling factorial using JSON 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.
///
/// # 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_comb_falling_factorial_json(
    input_json: *const c_char
) -> *mut c_char {
    let input: XNInput = match from_json_string(input_json) {
        | Some(i) => i,
        | None => {
            return to_c_string(
                serde_json::to_string(&FfiResult::<f64, String> {
                    ok: None,
                    err: Some("Invalid JSON input".to_string()),
                })
                .unwrap(),
            );
        },
    };

    let res = combinatorics::falling_factorial(input.x, input.n);

    to_c_string(
        serde_json::to_string(&FfiResult {
            ok: Some(res),
            err: None::<String>,
        })
        .unwrap(),
    )
}