//! Library providing basis for low level registers access
//! This crate re-exports macros refined in [ral-macro](https://docs.rs/ral-macro),
//! so this is the only library needed to be defined in dependencies
//!
//! # Code generator
//!
//! Refer to [ral-gen](https://docs.rs/ral-gen) crate documentation for code generation guidelines
//!
//! # DSL and produced result
//!
//! Internally generates register description backed by [ral](https://docs.rs/ral)
//! ```
//! use ral::register;
//!
//! register! {
//!     use crate_name::types::CustomType; // Use expressions for custom types used in field declarations
//!
//!     #[access = "read-write"] // Optional register wide access specifier
//!     #[doc = "Register description"] // Optional register description
//!     reg0 { // Register name
//!         offset: 0x8, // Register offset in enclosing peripheral
//!         value_size: 32, // Register size, expected values are 8, 16, 32 or 64
//!         reset_mask: 0xFFFFFFFF, // Reset mask
//!         reset_value: 0x0, // Reset value
//!         fields: { // Optional fields
//!             #[doc = "Bits 16:31 - Read-only u16 field"] // Each field can have a description
//!             #[access = "read-only"] // Access specifier
//!             field5[16:16] as u16, // Field specification `<name>[<offset>:<width>] as <type>`
//!
//!             #[doc = "Bits 14:15 - Write-only field"]
//!             #[access = "write-only"] // Only setters will be generated
//!             field4[14:2] as u8, // Default supported types are `u8`, `u16`, `u32` and `u64`
//!
//!             #[doc = "Bits 11:13 - Read-only field"]
//!             #[access = "read-only"] // Only getters will be generated
//!             field3[11:3] as u8,
//!
//!             #[doc = "Bit 10 - Boolean field"]
//!             #[access = "read-write"] // `read-write` is a default access specifier
//!             field2[10:1] as bool, // `bool` fields are also supported by default
//!
//!             #[doc = "Bits 8:9 - Enum field"]
//!             #[access = "read-write"] // Both getters and setters will be generated
//!             field1[8:2] as CustomType, // Custom types are supported with limitations
//!
//!             #[doc = "Bits 0:7 - Read-write by default long field"]
//!             field0[0:8] as u8
//!         }
//!     }
//! }
//! ```
//!
//! Above register definition will be transformed into following code
//! ```
//! // Required uses section
//! use core::sync::atomic::AtomicPtr;
//! use core::convert::TryFrom;
//! use ral::{borrow_register, init_register, return_register, value_read, value_write, R, ReadableRegister, Register, VolatileCell, WritableRegister};
//! use crate_name::types::CustomType;
//! const REGISTER: AtomicPtr<VolatileCell<<Reg0 as Register>::ValueType>> = AtomicPtr::new(
//!     (super::BASE_ADDRESS /* Enclosing peripheral/cluster base address */ + 0x00 /* offset */) as *mut VolatileCell<<Reg0 as Register>::ValueType>,
//! );
//! ///Register description
//! pub fn reg0() -> Option<Reg0> {
//!     borrow_register(&REGISTER).map(Reg0)
//! }
//! pub struct Reg0(R<u32, Reg0>);
//! impl Drop for Reg0 {
//!     fn drop(&mut self) {
//!         let Reg0(register) = self;
//!         return_register(&REGISTER, register);
//!     }
//! }
//! impl Register for Reg0 {
//!     type RegisterType = Self;
//!     type ValueType = u32;
//!     const RESET_MASK: Self::ValueType = 0xFFFF_FFFF;
//!     const RESET_VALUE: Self::ValueType = 0x1234_0000;
//! }
//! impl ReadableRegister for Reg0 { // Will be added if register wide access allows read
//!     fn get_bits(&self) -> Self::ValueType {
//!         self.0.get_bits()
//!     }
//!
//!     fn read(&mut self) -> &mut Self::RegisterType {
//!         self.0.read();
//!         self
//!     }
//! }
//! impl WritableRegister for Reg0 { // Will be added if register wide access allows write
//!     fn set_bits(&mut self, bits: Self::ValueType) -> &mut Self::RegisterType {
//!         self.0.set_bits(bits);
//!         self
//!     }
//!     fn reset(&mut self) -> &mut Self::RegisterType {
//!         self.set_bits(Self::RESET_VALUE)
//!     }
//!     fn write(&mut self) -> &mut Self::RegisterType {
//!         self.0.write();
//!         self
//!     }
//! }
//! impl Reg0 { // Will be added if any fields specified
//!     ///Bits 16:31 - Read-only u16 field
//!     #[inline]
//!     pub fn get_field5(&self) -> u16 {
//!         value_read!(self, 0x0000FFFFu32, 16) as u16
//!         // Will further expand into
//!         // ((self.0.get_bits() >> 16) & 0x0000FFFFu32) as u16
//!     }
//!     ///Bits 14:15 - Write-only field
//!     #[inline]
//!     pub fn set_field4(&mut self, value: u8) -> &mut Self {
//!         value_write!(self, 0x00000003u32, 14, value as <Self as Register>::ValueType);
//!         // Will further expand into
//!         // self.0.set_bits(
//!         //     (self.0.get_bits() & !(0x00000003u32 << 14))
//!         //         | ((value as <Self as Register>::ValueType & 0x00000003u32) << 14),
//!         // );
//!         self
//!     }
//!     ///Bits 11:13 - Read-only field
//!     #[inline]
//!     pub fn get_field3(&self) -> u8 {
//!         value_read!(self, 0x00000007u32, 11) as u8
//!         // Will further expand into
//!         // ((self.0.get_bits() >> 11) & 0x00000007u32) as u8
//!     }
//!     ///Bit 10 - Boolean field
//!     #[inline]
//!     pub fn is_field2_set(&self) -> bool {
//!         value_read!(self, 0x00000001u32, 10) == 1
//!         // Will further expand into
//!         // ((self.0.get_bits() >> 10) & 0x00000001u32) == 1
//!     }
//!     ///Bit 10 - Boolean field
//!     #[inline]
//!     pub fn set_field2_value(&mut self, value: bool) -> &mut Self {
//!         value_write!(self, 0x00000001u32, 10, value as <Self as Register>::ValueType);
//!         // Will further expand into
//!         // self.0.set_bits(
//!         //     (self.0.get_bits() & !(0x00000001u32 << 10))
//!         //         | ((value as <Self as Register>::ValueType & 0x00000001u32) << 10),
//!         // );
//!         self
//!     }
//!     ///Bit 10 - Boolean field
//!     #[inline]
//!     pub fn set_field2(&mut self) -> &mut Self {
//!         self.set_field2_value(true)
//!     }
//!     ///Bit 10 - Boolean field
//!     #[inline]
//!     pub fn unset_field2(&mut self) -> &mut Self {
//!         self.set_field2_value(false)
//!     }
//!     ///Bits 8:9 - Enum field
//!     #[inline]
//!     pub fn get_field1(
//!         &self,
//!     ) -> Result<CustomType, <CustomType as TryFrom<<Self as Register>::ValueType>>::Error> {
//!         <CustomType as TryFrom<<Self as Register>::ValueType>>::try_from(value_read!(self, 0x00000003u32, 8))
//!         // Will further expand into
//!         // <CustomType as TryFrom<<Self as Register>::ValueType>>::try_from(
//!         //     (self.0.get_bits() >> 8) & 0x00000003u32,
//!         // )
//!     }
//!     ///Bits 8:9 - Enum field
//!     #[inline]
//!     pub fn set_field1(
//!         &mut self,
//!         value: CustomType,
//!     ) -> Result<&mut Self, <<Self as Register>::ValueType as TryFrom<CustomType>>::Error>
//!     {
//!         value_write!(self, 0x00000003u32, 8, <<Self as Register>::ValueType as TryFrom<#ty>>::try_from(value)?);
//!         // Will further expand into
//!         // self.0.set_bits(
//!         //     (self.0.get_bits() & !(0x00000003u32 << 8))
//!         //         | ((<<Self as Register>::ValueType as TryFrom<CustomType>>::try_from(value)?
//!         //             & 0x00000003u32) << 8),
//!         // );
//!         Ok(self)
//!     }
//!     ///Bits 0:7 - Read-write by default long field
//!     #[inline]
//!     pub fn get_field0(&self) -> u8 {
//!         value_read!(self, 0x000000FFu32, 0) as u8
//!         // Will further expand into
//!         // ((self.0.get_bits() >> 0) & 0x000000FFu32) as u8
//!     }
//!     ///Bits 0:7 - Read-write by default long field
//!     #[inline]
//!     pub fn set_field0(&mut self, value: u8) -> &mut Self {
//!         value_write!(self, 0x000000FFu32, 0, value as <Self as Register>::ValueType);
//!         // Will further expand into
//!         // self.0.set_bits(
//!         //     (self.0.get_bits() & !(0x000000FFu32 << 0))
//!         //         | ((value as <Self as Register>::ValueType & 0x000000FFu32) << 0),
//!         // );
//!         self
//!     }
//! }
//! ```
//!
//! # Proposed modules structure
//!
//! Enclosing peripheral module can look like this
//! ```ignore
//! #![doc = "Peripheral description"]
//!
//! mod reg0;
//! pub use reg0::*;
//!
//! const BASE_ADDRESS: usize = 0x0000_0000; // Should be actual peripheral base address
//! ```
//!
//! Peripherals module should look like this
//! ```ignore
//! pub mod peripheral;
//! ```
//!
//! And finally `lib.rs` should look like this
//! ```ignore
//! #![doc = "Device description"]
//!
//! pub mod peripherals;
//! ```
//!
//! So the recommended module hierarchy is
//! ```text,ignore
//! src/
//! ├── lib.rs
//! └── peripherals/
//!     ├── mod.rs
//!     └── peripheral/
//!         ├── mod.rs
//!         ├── reg0.rs
//!         ├── reg1.rs
//!         └── cluster/
//!             ├── mod.rs
//!             ├── reg2.rs
//!             ├── reg3.rs
//!             └── reg4.rs
//! ```
//!
//! The layout also includes optional cluster module, which can look like this
//! ```ignore
//! #![doc = "Cluster description"]
//!
//! mod reg2;
//! pub use reg2::*;
//! mod reg3;
//! pub use reg3::*;
//! mod reg4;
//! pub use reg4::*;
//!
//! const BASE_ADDRESS: usize = super::BASE_ADDRESS + 0x40; // Enclosing peripheral/cluster base address plus offset
//! ```
//!
//! # Requirenments to custom types
//!
//! For read access you must implement `TryFrom<u32> for CustomType` or `From<u32> for CustomType` if your register is 32-bit
//! For write access you have to implement `TryFrom<CustomType> for u32` or `From<CustomType> for u32` respectively
//!
//! # How to use resulting library
//!
//! ```
//! use device_crate::peripherals::peripheral;
//!
//! let mut reg0 = peripheral::reg0()
//!         .unwrap() // Borrow the register
//!         .read(); // Load current data stored in register
//! let field3 = reg0.get_field3(); // Read `u8` field
//!
//! let field2 = reg0.is_field2_set(); // Read `bool` field
//! let field1: CustomType = reg0.get_field1().unwrap(); // Read field represented by `CustomType`
//! reg0
//!     .set_field0(if field2 {
//!         reg0.get_field5() as u8
//!     } else {
//!         0
//!     }) // Set `u8` field
//!     .unset_field2() // Unset `bool` field
//!     .set_field4(field3 + 10) // Set 'u8' field
//!     .set_field1(if field1 == Two { One } else { Three }).unwrap() // Set `CustomType` field
//!     .write(); // Finally write result to hardware register
//! ```
#![no_std]

use core::marker::{Copy, PhantomData};
use core::ops::{BitAnd, BitOr, Not};
use core::ptr::{null_mut, NonNull};
use core::sync::atomic::AtomicPtr;
use core::sync::atomic::Ordering::SeqCst;

pub use vcell::VolatileCell;

pub use ral_macro::*;

/// Register data holder, abstracts interaction with actual hardware
pub struct R<ValueType, RegisterType>
where
    ValueType:
        Copy + Not<Output = ValueType> + BitAnd<Output = ValueType> + BitOr<Output = ValueType>,
    RegisterType: Register<RegisterType = RegisterType, ValueType = ValueType>,
{
    register_type: PhantomData<RegisterType>,
    register: NonNull<VolatileCell<ValueType>>,
    bits: ValueType,
}

impl<ValueType, RegisterType> R<ValueType, RegisterType>
where
    ValueType:
        Copy + Not<Output = ValueType> + BitAnd<Output = ValueType> + BitOr<Output = ValueType>,
    RegisterType: Register<RegisterType = RegisterType, ValueType = ValueType>,
{
    /// Creates new instance bound to specific register
    #[inline]
    pub fn new(register: *mut VolatileCell<ValueType>) -> Option<Self> {
        NonNull::new(register).map(|ptr| Self {
            register_type: PhantomData,
            register: ptr,
            bits: RegisterType::RESET_VALUE,
        })
    }

    /// Gets cached bits
    #[inline]
    pub fn get_bits(&self) -> ValueType {
        self.bits
    }

    /// Stores bits into cache
    #[inline]
    pub fn set_bits(&mut self, bits: ValueType) {
        self.bits = bits;
    }

    /// Loads data from register to cache
    #[inline]
    pub fn read(&mut self) {
        unsafe {
            self.bits = self.register.as_ref().get();
        }
    }

    /// Stores data from cache to register
    #[inline]
    pub fn write(&mut self) {
        unsafe {
            self.register.as_ref().set(
                (!RegisterType::RESET_MASK & RegisterType::RESET_VALUE)
                    | (RegisterType::RESET_MASK & self.bits),
            );
        }
    }
}

impl<ValueType, RegisterType> Into<*mut VolatileCell<ValueType>> for &mut R<ValueType, RegisterType>
where
    ValueType:
        Copy + Not<Output = ValueType> + BitAnd<Output = ValueType> + BitOr<Output = ValueType>,
    RegisterType: Register<RegisterType = RegisterType, ValueType = ValueType>,
{
    fn into(self) -> *mut VolatileCell<ValueType> {
        self.register.as_ptr()
    }
}

/// Trait representing register, actual registers are to implement this
pub trait Register {
    /// Actual register type for operations chaining
    type RegisterType: Register;

    /// Value type, expected to be one of `u8`, `u16`, `u32` or `u64`
    type ValueType: Copy
        + Not<Output = Self::ValueType>
        + BitAnd<Output = Self::ValueType>
        + BitOr<Output = Self::ValueType>;

    /// Reset mask
    const RESET_MASK: Self::ValueType;

    /// Reset value
    const RESET_VALUE: Self::ValueType;
}

/// Trait representing readable part of register, actual registers are to implement this
pub trait ReadableRegister: Register {
    /// Get value of the register as raw bits
    fn get_bits(&self) -> Self::ValueType;

    /// Loads value from the register
    fn read(&mut self) -> &mut Self::RegisterType;
}

/// Trait representing writable part of register, actual registers are to implement this
pub trait WritableRegister: Register {
    /// Set value of the register as raw bits
    fn set_bits(&mut self, bits: Self::ValueType) -> &mut Self::RegisterType;

    /// Reset value of the register to default
    fn reset(&mut self) -> &mut Self::RegisterType;

    /// Writes value to the register
    fn write(&mut self) -> &mut Self::RegisterType;
}

/// Extract specific bits from register value
#[macro_export]
macro_rules! value_read {
    ($r: expr, $m: expr, $o: expr) => {
        (($r.0.get_bits() >> $o) & $m)
    };
}

/// Set specific bits to register value
#[macro_export]
macro_rules! value_write {
    ($r: expr, $m: expr, $o: expr, $v: expr) => {
        $r.0.set_bits(($r.0.get_bits() & !($m << $o)) | ((($v) & $m) << $o));
    };
}

/// Init register
#[macro_export]
macro_rules! init_register {
    ($a: expr, $t: tt) => {
        AtomicPtr::new($a as *mut VolatileCell<<$t as Register>::ValueType>)
    };
}

/// Exclusively borrows register
pub fn borrow_register<ValueType, RegisterType>(
    holder: &AtomicPtr<VolatileCell<ValueType>>,
) -> Option<R<ValueType, RegisterType>>
where
    ValueType:
        Copy + Not<Output = ValueType> + BitAnd<Output = ValueType> + BitOr<Output = ValueType>,
    RegisterType: Register<RegisterType = RegisterType, ValueType = ValueType>,
{
    R::new(holder.swap(null_mut(), SeqCst))
}

/// Releases register, so it can be borrowed again
pub fn return_register<ValueType, RegisterType>(
    holder: &AtomicPtr<VolatileCell<ValueType>>,
    register: &mut R<ValueType, RegisterType>,
) where
    ValueType:
        Copy + Not<Output = ValueType> + BitAnd<Output = ValueType> + BitOr<Output = ValueType>,
    RegisterType: Register<RegisterType = RegisterType, ValueType = ValueType>,
{
    holder.swap(register.into(), SeqCst);
}

#[cfg(test)]
mod tests {
    use super::*;

    struct TestR(R<u32, TestR>);

    impl Register for TestR {
        type RegisterType = Self;

        type ValueType = u32;

        const RESET_MASK: Self::ValueType = 0xF3FF_FFFF;

        const RESET_VALUE: Self::ValueType = 0x2800_0000;
    }

    impl ReadableRegister for TestR {
        fn get_bits(&self) -> Self::ValueType {
            self.0.get_bits()
        }

        fn read(&mut self) -> &mut Self::RegisterType {
            self.0.read();
            self
        }
    }

    impl WritableRegister for TestR {
        fn set_bits(&mut self, bits: Self::ValueType) -> &mut Self::RegisterType {
            self.0.set_bits(bits);
            self
        }

        fn reset(&mut self) -> &mut Self::RegisterType {
            self.set_bits(Self::RESET_VALUE)
        }

        fn write(&mut self) -> &mut Self::RegisterType {
            self.0.write();
            self
        }
    }

    impl TestR {
        #[inline]
        pub fn get_test_30_31(&self) -> u8 {
            value_read!(self, 0x3u32, 30) as u8
        }

        pub fn set_test_30_31(&mut self, value: u8) -> &mut Self {
            value_write!(self, 0x3u32, 30, value as <Self as Register>::ValueType);
            self
        }

        #[inline]
        pub fn get_test_0_3(&self) -> u8 {
            value_read!(self, 0xFu32, 0) as u8
        }

        pub fn set_test_0_3(&mut self, value: u8) -> &mut Self {
            value_write!(self, 0xFu32, 0, value as <Self as Register>::ValueType);
            self
        }
    }

    #[test]
    fn test_register_access() {
        let mut registry_data: u32 = 0x89AB_CDEF;

        let register_holder: AtomicPtr<VolatileCell<<TestR as Register>::ValueType>> =
            init_register!(&mut registry_data as *mut u32, TestR);
        let mut register_some: Option<R<u32, TestR>> = borrow_register(&register_holder);
        let register_none: Option<R<u32, TestR>> = borrow_register(&register_holder);
        assert!(register_some.is_some());
        assert!(register_none.is_none());
        return_register(&register_holder, register_some.as_mut().unwrap());
        let mut register: Option<R<u32, TestR>> = borrow_register(&register_holder);
        assert!(register.is_some());
        return_register(&register_holder, register.as_mut().unwrap());
    }

    #[test]
    fn test_get() {
        let mut registry_data: u32 = 0x8765_4321;

        let register_holder: AtomicPtr<VolatileCell<<TestR as Register>::ValueType>> =
            init_register!(&mut registry_data as *mut u32, TestR);
        let mut register = borrow_register(&register_holder).map(TestR).unwrap();
        register.read();
        assert_eq!(register.get_test_0_3(), 0x01);
        assert_eq!(register.get_test_30_31(), 0x02);
    }

    #[test]
    fn test_set() {
        let mut registry_data: u32 = 0x8765_4321;

        let register_holder: AtomicPtr<VolatileCell<<TestR as Register>::ValueType>> =
            init_register!(&mut registry_data as *mut u32, TestR);
        let mut register = borrow_register(&register_holder).map(TestR).unwrap();
        register.set_test_0_3(0xDAu8).set_test_30_31(0x0Au8).write();
        let TestR(r) = &mut register;
        return_register(&register_holder, r);
        assert_eq!(registry_data, 0x8000_000A | TestR::RESET_VALUE);
    }

    #[test]
    fn test_update() {
        let mut registry_data: u32 = 0x8765_4321;

        let register_holder: AtomicPtr<VolatileCell<<TestR as Register>::ValueType>> =
            init_register!(&mut registry_data as *mut u32, TestR);
        let mut register = borrow_register(&register_holder).map(TestR).unwrap();
        register
            .read()
            .set_test_0_3(0xDAu8)
            .set_test_30_31(0x01u8)
            .write();
        let TestR(r) = &mut register;
        return_register(&register_holder, r);
        assert_eq!(registry_data, 0x4B65_432A);
    }

    #[test]
    fn test_reset() {
        let mut registry_data: u32 = 0x8765_4321;

        let register_holder: AtomicPtr<VolatileCell<<TestR as Register>::ValueType>> =
            init_register!(&mut registry_data as *mut u32, TestR);
        let mut register = borrow_register(&register_holder).map(TestR).unwrap();
        register.read();
        register.reset();
        register.write();
        let TestR(r) = &mut register;
        return_register(&register_holder, r);
        assert_eq!(registry_data, TestR::RESET_VALUE);
    }
}