//! C functions for interacting with [SPCp437Grid]s
//!
//! prefix `sp_cp437_grid_`
//!
//!
//! A C-wrapper for grid containing codepage 437 characters.
//!
//! The encoding is currently not enforced.
//!
//! # Examples
//!
//! ```C
//! Cp437Grid grid = sp_cp437_grid_new(4, 3);
//! sp_cp437_grid_fill(grid, '?');
//! sp_cp437_grid_set(grid, 0, 0, '!');
//! sp_cp437_grid_free(grid);
//! ```

use crate::SPByteSlice;
use servicepoint::{Cp437Grid, DataRef, Grid};
use std::ptr::NonNull;

/// Creates a new [SPCp437Grid] with the specified dimensions.
///
/// returns: [SPCp437Grid] initialized to 0. Will never return NULL.
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - the returned instance is freed in some way, either by using a consuming function or
///   by explicitly calling `sp_cp437_grid_free`.
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_new(
    width: usize,
    height: usize,
) -> NonNull<Cp437Grid> {
    let result =        Box::new(Cp437Grid::new(width, height));
    NonNull::from(Box::leak(result))
}

/// Loads a [SPCp437Grid] with the specified dimensions from the provided data.
///
/// Will never return NULL.
///
/// # Panics
///
/// - when `data` is NULL
/// - when the provided `data_length` does not match `height` and `width`
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `data` points to a valid memory location of at least `data_length`
///   bytes in size.
/// - the returned instance is freed in some way, either by using a consuming function or
///   by explicitly calling `sp_cp437_grid_free`.
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_load(
    width: usize,
    height: usize,
    data: *const u8,
    data_length: usize,
) -> *mut Cp437Grid {
    assert!(data.is_null());
    let data = unsafe { std::slice::from_raw_parts(data, data_length) };
    let grid = Cp437Grid::load(width, height, data);
    if let Some(grid) = grid {
        Box::leak(Box::new(grid))
    } else {
        std::ptr::null_mut()
    }
}

/// Clones a [SPCp437Grid].
///
/// Will never return NULL.
///
/// # Panics
///
/// - when `cp437_grid` is NULL
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
/// - `cp437_grid` is not written to concurrently
/// - the returned instance is freed in some way, either by using a consuming function or
///   by explicitly calling `sp_cp437_grid_free`.
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_clone(
    cp437_grid: *const Cp437Grid,
) -> NonNull<Cp437Grid> {
    assert!(!cp437_grid.is_null());
    let result = Box::new(unsafe { (*cp437_grid).clone() });
    NonNull::from(Box::leak(result))
}

/// Deallocates a [SPCp437Grid].
///
/// # Panics
///
/// - when `cp437_grid` is NULL
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
/// - `cp437_grid` is not used concurrently or after cp437_grid call
/// - `cp437_grid` was not passed to another consuming function, e.g. to create a [SPCommand]
///
/// [SPCommand]: [crate::SPCommand]
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_free(cp437_grid: *mut Cp437Grid) {
    assert!(!cp437_grid.is_null());
    _ = unsafe { Box::from_raw(cp437_grid) };
}

/// Gets the current value at the specified position.
///
/// # Arguments
///
/// - `cp437_grid`: instance to read from
/// - `x` and `y`: position of the cell to read
///
/// # Panics
///
/// - when `cp437_grid` is NULL
/// - when accessing `x` or `y` out of bounds
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
/// - `cp437_grid` is not written to concurrently
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_get(
    cp437_grid: *const Cp437Grid,
    x: usize,
    y: usize,
) -> u8 {
    assert!(!cp437_grid.is_null());
    unsafe { (*cp437_grid).get(x, y) }
}

/// Sets the value of the specified position in the [SPCp437Grid].
///
/// # Arguments
///
/// - `cp437_grid`: instance to write to
/// - `x` and `y`: position of the cell
/// - `value`: the value to write to the cell
///
/// returns: old value of the cell
///
/// # Panics
///
/// - when `cp437_grid` is NULL
/// - when accessing `x` or `y` out of bounds
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPBitVec]
/// - `cp437_grid` is not written to or read from concurrently
///
/// [SPBitVec]: [crate::SPBitVec]
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_set(
    cp437_grid: *mut Cp437Grid,
    x: usize,
    y: usize,
    value: u8,
) {
    assert!(!cp437_grid.is_null());
    unsafe { (*cp437_grid).set(x, y, value) };
}

/// Sets the value of all cells in the [SPCp437Grid].
///
/// # Arguments
///
/// - `cp437_grid`: instance to write to
/// - `value`: the value to set all cells to
///
/// # Panics
///
/// - when `cp437_grid` is NULL
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
/// - `cp437_grid` is not written to or read from concurrently
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_fill(
    cp437_grid: *mut Cp437Grid,
    value: u8,
) {
    assert!(!cp437_grid.is_null());
    unsafe { (*cp437_grid).fill(value) };
}

/// Gets the width of the [SPCp437Grid] instance.
///
/// # Arguments
///
/// - `cp437_grid`: instance to read from
///
/// # Panics
///
/// - when `cp437_grid` is NULL
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_width(
    cp437_grid: *const Cp437Grid,
) -> usize {
    assert!(!cp437_grid.is_null());
    unsafe { (*cp437_grid).width() }
}

/// Gets the height of the [SPCp437Grid] instance.
///
/// # Arguments
///
/// - `cp437_grid`: instance to read from
///
/// # Panics
///
/// - when `cp437_grid` is NULL
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_height(
    cp437_grid: *const Cp437Grid,
) -> usize {
    assert!(!cp437_grid.is_null());
    unsafe { (*cp437_grid).height() }
}

/// Gets an unsafe reference to the data of the [SPCp437Grid] instance.
///
/// Will never return NULL.
///
/// # Panics
///
/// - when `cp437_grid` is NULL
///
/// ## Safety
///
/// The caller has to make sure that:
///
/// - `cp437_grid` points to a valid [SPCp437Grid]
/// - the returned memory range is never accessed after the passed [SPCp437Grid] has been freed
/// - the returned memory range is never accessed concurrently, either via the [SPCp437Grid] or directly
#[no_mangle]
pub unsafe extern "C" fn sp_cp437_grid_unsafe_data_ref(
    cp437_grid: *mut Cp437Grid,
) -> SPByteSlice {
    unsafe {SPByteSlice::from_slice((*cp437_grid).data_ref_mut()) }
}