// Copyright 2018 Adam Greig
// Copyright 2025 Ian McIntyre
// See LICENSE-APACHE and LICENSE-MIT for license details.

//! This crate contains an MMIO abstraction that uses macros to read,
//! modify, and write fields in registers.
//!
//! See the [README](https://github.com/adamgreig/ral-registers/blob/master/README.md)
//! for further details.

#![no_std]

use core::ptr::NonNull;

/// Describes a type that acts as a peripheral instance.
///
/// If you're not sure how to implement this, try using [`Instance`].
///
/// # Safety
///
/// This can only be implemented atop "smart pointer" objects that
/// produce the same raw pointer to a static register block.
pub unsafe trait Inst {}

/// Safety: any shared reference to an instance can similarly provide
/// access to the underlying static object.
unsafe impl<I> Inst for &'_ I where I: Inst {}

/// Safety: see shared reference documentation. If a shared
/// reference can provide this access, then so can an exclusive
/// reference.
unsafe impl<I> Inst for &'_ mut I where I: Inst {}

/// A pointer to a peripheral instance.
///
/// This is transparently a `NonNull<T>`. Like a `NonNull<T>`,
/// the type is `Copy` and `Clone`, so it may be shared throughout
/// a single execution context.
#[derive(PartialEq, Eq)]
#[repr(transparent)]
pub struct Instance<T: ?Sized>(NonNull<T>);

/// Safety: the constructor's safety contract enforces the
/// trait's safety requirements.
unsafe impl<T: ?Sized> Inst for Instance<T> {}

impl<T: ?Sized> Instance<T> {
    /// Create an instance that points to a peripheral register block.
    ///
    /// # Safety
    ///
    /// The pointer must not be NULL. The pointer is expected to point
    /// to static memory that represents a block of MMIO registers.
    /// The layout of `T` must be correct for the base address.
    #[inline(always)]
    #[must_use]
    pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
        // Safety: caller claims the pointer isn't NULL.
        Self(unsafe { NonNull::new_unchecked(ptr) })
    }

    /// Access the inner pointer.
    #[inline(always)]
    #[must_use]
    pub const fn as_ptr(self) -> *mut T {
        self.0.as_ptr()
    }
}

impl<T: ?Sized> Clone for Instance<T> {
    #[inline(always)]
    fn clone(&self) -> Self {
        *self
    }
}

impl<T: ?Sized> Copy for Instance<T> {}

impl<T> core::fmt::Debug for Instance<T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        let ptr = self.0.as_ptr() as usize;
        f.debug_tuple("Instance")
            .field(&format_args!("{ptr:#X}"))
            .finish()
    }
}

/// Check expressions that may be unsafe.
///
/// Users are not expected to pass non-Copy expressions into
/// this expansion.
#[macro_export]
#[doc(hidden)]
macro_rules! __expand_unsafe {
    ( $( $expr:expr, )+ ) => { if false { $( let _ = $expr; )* } };
}

#[doc(hidden)]
#[allow(non_snake_case)]
pub const fn must_be_ral_registers_Inst<I: Inst>(_: &I) {}

/// Write to a register.
#[macro_export]
macro_rules! write_reg {
    (  $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+, $( $field:ident : $value:expr ),+ $(,)? ) => {{
        use $($periph)::+ $( :: $reg )* as __register;

        $crate::write_reg!($($periph)::+, $instance, $(. $reg $([$offset])* )*,
            $({
                #[allow(unused_imports)]
                use __register::{$field::vals::{*}};
                const { assert!(__register::$field::access.is_write()); }
                ($value << __register::$field::offset)
                    & __register::$field::mask
            }) | *
        );
    }};
    ( $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+, $value:expr ) => {{
        #[allow(unused_imports)]
        use $($periph)::+ $( :: $reg )* as __register;
        const { assert!(__register::access.is_write()); }

        $crate::must_be_ral_registers_Inst(&$instance);
        $crate::__expand_unsafe!($instance, $( $( $offset ,)* )*);
        #[allow(unused_unsafe)]
        unsafe { (&raw mut (*$instance.as_ptr())$(. $reg $([$offset])* )*).write_volatile($value) }
    }};
}

/// Modify a register.
#[macro_export]
macro_rules! modify_reg {
    ( $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+, $( $field:ident : $value:expr ),+ $(,)? ) => {{
        $crate::__expand_unsafe!($instance, $( $( $offset ,)* )*);
        $crate::must_be_ral_registers_Inst(&$instance);
        use $($periph)::+ $( :: $reg )* as __register;
        const { assert!(__register::access.is_read_write()); }

        #[allow(unused_unsafe)]
        unsafe {
            (&raw mut (*$instance.as_ptr())$(. $reg $([$offset])* )*).write_volatile(
                (&raw const (*$instance.as_ptr())$(. $reg $([$offset])* )*).read_volatile() & const { !( $(__register::$field::mask) | * ) }
                | $({
                    #[allow(unused_imports)]
                    use __register::{$field::vals::{*}};
                    const { assert!(__register::$field::access.is_read_write()); }
                    ($value << __register::$field::offset )
                        & __register::$field::mask
                }) | *
            )
        }
    }};
    ( $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+, $fn:expr ) => {{
        #[allow(unused_imports)]
        use $($periph)::+ $( :: $reg )* as __register;
        const { assert!(__register::access.is_read_write()); }

        $crate::__expand_unsafe!($instance, $( $( $offset ,)* )*);
        $crate::must_be_ral_registers_Inst(&$instance);
        #[allow(unused_unsafe)]
        unsafe {
            (&raw mut (*$instance.as_ptr())$(. $reg $([$offset])* )*).write_volatile(
                $fn((&raw const (*$instance.as_ptr())$(. $reg $([$offset])* )*).read_volatile())
            )
        }
    }};
}

/// Read the value from a register.
#[macro_export]
macro_rules! read_reg {
    ( $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+, $( $field:ident ),+ $(,)? ) => {{
        let __value = $crate::read_reg!($($periph)::+, $instance, $(. $reg $([$offset])* )*);
        use $($periph)::+ $( :: $reg )* as __register;

        ( $({
            #[allow(unused_imports)]
            use __register::$field::vals::{*};
            const { assert!(__register::$field::access.is_read()); }
            (__value & __register::$field::mask) >> __register::$field::offset
        }) , *)
    }};
    ( $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+, $field:ident $($cmp:tt)* ) => {{
        use $($periph)::+ $( :: $reg )* as __register;

        #[allow(unused_imports)]
        use __register::$field::vals::{*};
        const { assert!(__register::$field::access.is_read()); }

        (($crate::read_reg!($($periph)::+, $instance, $(. $reg $([$offset])* )* ) & __register::$field::mask) >> __register::$field::offset) $($cmp)*
    }};
    ( $(::)? $($periph:ident)::+, $instance:expr, $( $(.)? $reg:ident $([$offset:expr])* )+ ) => {{
        #[allow(unused_imports)]
        use $($periph)::+ $( :: $reg )* as __register;
        const { assert!(__register::access.is_read()); }

        $crate::__expand_unsafe!($instance, $( $( $offset ,)* )*);
        $crate::must_be_ral_registers_Inst(&$instance);
        #[allow(unused_unsafe)]
        unsafe {
            (&raw const (*$instance.as_ptr())$(. $reg $([$offset])* )*).read_volatile()
        }
    }};
}

/// Access for registers and fields.
pub enum Access {
    /// Read-only access.
    RO,
    /// Write-only access.
    WO,
    /// Read-write access.
    RW,
}

impl Access {
    /// Returns `true` if the access is read.
    #[inline(always)]
    #[must_use]
    pub const fn is_read(self) -> bool {
        matches!(self, Self::RO | Self::RW)
    }
    /// Returns `true` if the access is write.
    #[inline(always)]
    #[must_use]
    pub const fn is_write(self) -> bool {
        matches!(self, Self::WO | Self::RW)
    }
    /// Returns `true` if the access is read and write.
    #[inline(always)]
    #[must_use]
    pub const fn is_read_write(self) -> bool {
        matches!(self, Self::RW)
    }
}

#[macro_export]
macro_rules! register {
    (
        $(#[$register_meta:meta])*
        $vis:vis $register_name:ident <$ty:ty> $register_access:ident [$(
            $(#[$field_meta:meta])*
            $field_name:ident start($start_bit:expr) width($width:expr) $field_access:ident {$(
                $(#[$enum_meta:meta])*
                $enum_name:ident = $enum_val:expr $(,)?
            )*}
        )*]
    ) => {
        $(#[$register_meta])*
        #[allow(non_snake_case, non_upper_case_globals)]
        $vis mod $register_name {
            #[doc(hidden)]
            pub const access: $crate::Access = $crate::Access::$register_access;
        $(
            $(#[$field_meta])*
            #[allow(non_snake_case)]
            pub mod $field_name {
                #[doc(hidden)]
                pub const offset: $ty = $start_bit;
                #[doc(hidden)]
                pub const mask: $ty = ((1 << $width) - 1) << $start_bit;
                #[doc(hidden)]
                pub const access: $crate::Access = $crate::Access::$field_access;

                #[doc(hidden)]
                pub mod vals {
                $(
                    $(#[$enum_meta])*
                    pub const $enum_name: $ty = $enum_val;
                )*
                }

                #[doc(inline)]
                pub use self::vals::*;
            }
        )*
        }
    };
}

#[macro_export]
macro_rules! instances {
    (unsafe { $(
        $(#[$doc:meta])*
        $vis:vis $name:ident<$block:ty> = $base_address:expr;
    )* }) => {$(
        $(#[$doc])*
        #[allow(non_snake_case)]
        #[inline(always)]
        $vis const unsafe fn $name() -> $crate::Instance<$block> {
            // Safety: Macro caller swears that the $base_address points
            // to the given kind of register block.
            unsafe { $crate::Instance::new_unchecked($base_address as _) }
        }
    )*};
}