//! C functions for interacting with `BrightnessGrid`s
//!
//! prefix `sp_brightness_grid_`

use std::intrinsics::transmute;
use servicepoint::{BrightnessGrid, DataRef, Grid, PrimitiveGrid, Brightness};

use crate::c_slice::CByteSlice;

/// C-wrapper for grid containing brightness values.
#[derive(Clone)]
pub struct CBrightnessGrid(pub(crate) BrightnessGrid);

/// Creates a new `BrightnessGrid` with the specified dimensions.
///
/// returns: `BrightnessGrid` initialized to 0.
///
/// # 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_brightness_grid_dealloc`.
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_new(
    width: usize,
    height: usize,
) -> *mut CBrightnessGrid {
    Box::into_raw(Box::new(CBrightnessGrid(BrightnessGrid::new(width, height))))
}

/// Loads a `BrightnessGrid` with the specified dimensions from the provided data.
///
/// # Panics
///
/// When the provided `data_length` is not sufficient for the `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_brightness_grid_dealloc`.
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_load(
    width: usize,
    height: usize,
    data: *const u8,
    data_length: usize,
) -> *mut CBrightnessGrid {
    let data = std::slice::from_raw_parts(data, data_length);
    let grid = PrimitiveGrid::load(width, height, data);
    let grid = BrightnessGrid::try_from(grid)
        .expect("invalid brightness value");
    Box::into_raw(Box::new(CBrightnessGrid(grid)))
}

/// Clones a `BrightnessGrid`.
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
/// - `this` is not written to concurrently
/// - the returned instance is freed in some way, either by using a consuming function or
///   by explicitly calling `sp_brightness_grid_dealloc`.
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_clone(
    this: *const CBrightnessGrid,
) -> *mut CBrightnessGrid {
    Box::into_raw(Box::new((*this).clone()))
}

/// Deallocates a `BrightnessGrid`.
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
/// - `this` is not used concurrently or after this call
/// - `this` was not passed to another consuming function, e.g. to create a `Command`
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_dealloc(this: *mut CBrightnessGrid) {
    _ = Box::from_raw(this);
}

/// Gets the current value at the specified position.
///
/// # Arguments
///
/// * `this`: instance to read from
/// * `x` and `y`: position of the cell to read
///
/// # Panics
///
/// When accessing `x` or `y` out of bounds.
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
/// - `this` is not written to concurrently
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_get(
    this: *const CBrightnessGrid,
    x: usize,
    y: usize,
) -> u8 {
    (*this).0.get(x, y).into()
}

/// Sets the value of the specified position in the `BrightnessGrid`.
///
/// # Arguments
///
/// * `this`: 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 accessing `x` or `y` out of bounds.
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BitVec`
/// - `this` is not written to or read from concurrently
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_set(
    this: *mut CBrightnessGrid,
    x: usize,
    y: usize,
    value: u8,
) {
    let brightness = Brightness::try_from(value)
        .expect("invalid brightness value");
    (*this).0.set(x, y, brightness);
}

/// Sets the value of all cells in the `BrightnessGrid`.
///
/// # Arguments
///
/// * `this`: instance to write to
/// * `value`: the value to set all cells to
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
/// - `this` is not written to or read from concurrently
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_fill(this: *mut CBrightnessGrid, value: u8) {
    let brightness = Brightness::try_from(value)
        .expect("invalid brightness value");
    (*this).0.fill(brightness);
}

/// Gets the width of the `BrightnessGrid` instance.
///
/// # Arguments
///
/// * `this`: instance to read from
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_width(this: *const CBrightnessGrid) -> usize {
    (*this).0.width()
}

/// Gets the height of the `BrightnessGrid` instance.
///
/// # Arguments
///
/// * `this`: instance to read from
///
/// # Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_height(this: *const CBrightnessGrid) -> usize {
    (*this).0.height()
}

/// Gets an unsafe reference to the data of the `BrightnessGrid` instance.
///
/// ## Safety
///
/// The caller has to make sure that:
///
/// - `this` points to a valid `BrightnessGrid`
/// - the returned memory range is never accessed after the passed `BrightnessGrid` has been freed
/// - the returned memory range is never accessed concurrently, either via the `BrightnessGrid` or directly
#[no_mangle]
pub unsafe extern "C" fn sp_brightness_grid_unsafe_data_ref(
    this: *mut CBrightnessGrid,
) -> CByteSlice {
    assert_eq!(std::mem::size_of::<Brightness>(), 1);

    let data = (*this).0.data_ref_mut();
    let data: &mut [u8] = transmute(data);
    CByteSlice {
        start: data.as_mut_ptr_range().start,
        length: data.len(),
    }
}