use crate::{heap_drop, heap_move, heap_move_nonnull, heap_remove, ByteSlice};
use servicepoint::{CommandCode, Header, Packet, TypedCommand};
use std::ptr::NonNull;

/// Turns a [TypedCommand] into a [Packet].
/// The [TypedCommand] gets consumed.
///
/// Returns NULL in case of an error.
#[no_mangle]
pub unsafe extern "C" fn sp_packet_from_command(
    command: NonNull<TypedCommand>,
) -> *mut Packet {
    let command = unsafe { heap_remove(command) };
    if let Ok(packet) = command.try_into() {
        heap_move(packet)
    } else {
        std::ptr::null_mut()
    }
}

/// Tries to load a [Packet] from the passed array with the specified length.
///
/// returns: NULL in case of an error, pointer to the allocated packet otherwise
#[no_mangle]
pub unsafe extern "C" fn sp_packet_try_load(data: ByteSlice) -> *mut Packet {
    let data = unsafe { data.as_slice() };
    match servicepoint::Packet::try_from(data) {
        Err(_) => std::ptr::null_mut(),
        Ok(packet) => heap_move(packet),
    }
}

/// Creates a raw [Packet] from parts.
///
/// returns: new instance. Will never return null.
#[no_mangle]
pub unsafe extern "C" fn sp_packet_from_parts(
    header: Header,
    payload: *const ByteSlice,
) -> NonNull<Packet> {
    let payload = if payload.is_null() {
        vec![]
    } else {
        let payload = unsafe { (*payload).as_slice() };
        Vec::from(payload)
    };

    heap_move_nonnull(Packet { header, payload })
}

/// Returns a pointer to the header field of the provided packet.
///
/// The returned header can be changed and will be valid for the lifetime of the packet.
#[no_mangle]
pub unsafe extern "C" fn sp_packet_get_header(
    packet: NonNull<Packet>,
) -> NonNull<Header> {
    NonNull::from(&mut unsafe { (*packet.as_ptr()).header })
}

/// Returns a pointer to the current payload of the provided packet.
///
/// The returned memory can be changed and will be valid until a new payload is set.
#[no_mangle]
pub unsafe extern "C" fn sp_packet_get_payload(
    packet: NonNull<Packet>,
) -> ByteSlice {
    unsafe { ByteSlice::from_slice(&mut (*packet.as_ptr()).payload) }
}

/// Sets the payload of the provided packet to the provided data.
///
/// This makes previous payload pointers invalid.
#[no_mangle]
pub unsafe extern "C" fn sp_packet_set_payload(
    packet: NonNull<Packet>,
    data: ByteSlice,
) {
    unsafe { (*packet.as_ptr()).payload = data.as_slice().to_vec() }
}

/// Serialize the packet into the provided buffer.
///
/// # Panics
///
/// - if the buffer is not big enough to hold header+payload.
#[no_mangle]
pub unsafe extern "C" fn sp_packet_serialize_to(
    packet: NonNull<Packet>,
    mut buffer: ByteSlice,
) {
    unsafe {
        packet.as_ref().serialize_to(buffer.as_slice_mut());
    }
}

/// Clones a [Packet].
#[no_mangle]
pub unsafe extern "C" fn sp_packet_clone(
    packet: NonNull<Packet>,
) -> NonNull<Packet> {
    heap_move_nonnull(unsafe { packet.as_ref().clone() })
}

/// Deallocates a [Packet].
#[no_mangle]
pub unsafe extern "C" fn sp_packet_free(packet: NonNull<Packet>) {
    unsafe { heap_drop(packet) }
}

/// Converts u16 into [CommandCode].
///
/// If the provided value is not valid, false is returned and result is not changed.
#[no_mangle]
pub unsafe extern "C" fn sp_u16_to_command_code(
    code: u16,
    result: *mut CommandCode,
) -> bool {
    match CommandCode::try_from(code) {
        Ok(code) => {
            unsafe {
                *result = code;
            }
            true
        }
        Err(_) => false,
    }
}