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#![cfg_attr(feature = "std", allow(unreachable_code, unused_mut))]

use crate::{map::reg::scb, reg::prelude::*, thr::ThrTokens};
use drone_core::token::Token;

/// Threads initialization token.
///
/// # Safety
///
/// Must be defined only once for a particular set of threads.
pub unsafe trait ThrsInitToken: Token {
    /// The set of thread tokens.
    type ThrTokens: ThrTokens;
}

/// A set of register tokens returned by [`init_extended`].
#[allow(missing_docs)]
pub struct ThrInitExtended {
    pub scb_ccr_bfhfnmign: scb::ccr::Bfhfnmign<Srt>,
    pub scb_ccr_div_0_trp: scb::ccr::Div0Trp<Srt>,
    pub scb_ccr_unalign_trp: scb::ccr::UnalignTrp<Srt>,
    pub scb_ccr_usersetmpend: scb::ccr::Usersetmpend<Srt>,
}

/// Initializes the thread system and returns a set of thread tokens.
///
/// # Examples
///
/// ```no_run
/// # #![feature(const_fn)]
/// # #![feature(proc_macro_hygiene)]
/// # use drone_core::token::Token;
/// # thr::vtable! {
/// #     use Thr;
/// #     struct Vtable;
/// #     struct Handlers;
/// #     struct Thrs;
/// #     struct ThrsInit;
/// #     static THREADS;
/// # }
/// # thr! {
/// #     use THREADS;
/// #     struct Thr {}
/// #     struct ThrLocal {}
/// # }
/// use drone_cortexm::{cortexm_reg_tokens, reg::prelude::*, thr};
///
/// cortexm_reg_tokens! {
///     struct Regs;
///     !scb_ccr;
///     !mpu_type; !mpu_ctrl; !mpu_rnr; !mpu_rbar; !mpu_rasr;
/// }
///
/// fn handler(reg: Regs, thr_init: ThrsInit) {
///     let (thr, extended) = thr::init_extended(thr_init);
///     extended.scb_ccr_div_0_trp.set_bit();
/// }
///
/// # fn main() {
/// #     handler(unsafe { Regs::take() }, unsafe { ThrsInit::take() })
/// # }
/// ```
#[allow(clippy::needless_pass_by_value)]
#[inline]
pub fn init_extended<T: ThrsInitToken>(_token: T) -> (T::ThrTokens, ThrInitExtended) {
    let scb_ccr = unsafe { scb::Ccr::<Srt>::take() };
    scb_ccr.store(|r| r.set_stkalign().set_nonbasethrdena());
    let scb::Ccr {
        stkalign,
        bfhfnmign: scb_ccr_bfhfnmign,
        div_0_trp: scb_ccr_div_0_trp,
        unalign_trp: scb_ccr_unalign_trp,
        usersetmpend: scb_ccr_usersetmpend,
        nonbasethrdena,
    } = scb_ccr;
    #[cfg(feature = "memory-protection-unit")]
    unsafe {
        mpu::reset();
    }
    drop(stkalign);
    drop(nonbasethrdena);
    (unsafe { T::ThrTokens::take() }, ThrInitExtended {
        scb_ccr_bfhfnmign,
        scb_ccr_div_0_trp,
        scb_ccr_unalign_trp,
        scb_ccr_usersetmpend,
    })
}

/// Initializes the thread system and returns a set of thread tokens.
///
/// # Examples
///
/// ```no_run
/// # #![feature(const_fn)]
/// # #![feature(proc_macro_hygiene)]
/// # use drone_core::token::Token;
/// # thr::vtable! {
/// #     use Thr;
/// #     struct Vtable;
/// #     struct Handlers;
/// #     struct Thrs;
/// #     struct ThrsInit;
/// #     static THREADS;
/// # }
/// # thr! {
/// #     use THREADS;
/// #     struct Thr {}
/// #     struct ThrLocal {}
/// # }
/// use drone_cortexm::{cortexm_reg_tokens, thr};
///
/// cortexm_reg_tokens! {
///     struct Regs;
///     !scb_ccr;
///     !mpu_type; !mpu_ctrl; !mpu_rnr; !mpu_rbar; !mpu_rasr;
/// }
///
/// fn handler(reg: Regs, thr_init: ThrsInit) {
///     let thr = thr::init(thr_init);
/// }
///
/// # fn main() {
/// #     handler(unsafe { Regs::take() }, unsafe { ThrsInit::take() })
/// # }
/// ```
#[allow(clippy::needless_pass_by_value)]
#[inline]
pub fn init<T: ThrsInitToken>(token: T) -> T::ThrTokens {
    let (thr, _) = init_extended(token);
    thr
}

#[cfg(feature = "memory-protection-unit")]
mod mpu {
    use crate::{map::reg::mpu, reg::prelude::*};
    use drone_core::token::Token;

    static MPU_RESET_TABLE: [u32; 16] = [
        rbar_reset(0),
        0,
        rbar_reset(1),
        0,
        rbar_reset(2),
        0,
        rbar_reset(3),
        0,
        rbar_reset(4),
        0,
        rbar_reset(5),
        0,
        rbar_reset(6),
        0,
        rbar_reset(7),
        0,
    ];

    #[allow(unused_assignments, unused_variables)]
    pub(super) unsafe fn reset() {
        #[cfg(feature = "std")]
        return unimplemented!();
        let mpu_type = mpu::Type::<Srt>::take();
        let mpu_ctrl = mpu::Ctrl::<Srt>::take();
        let mut table_ptr = &MPU_RESET_TABLE;
        if mpu_type.load().dregion() == 0 {
            return;
        }
        mpu_ctrl.reset();
        llvm_asm!("
            ldmia $0!, {r5, r6, r8, r9, r10, r11, r12, r14}
            stmia $1, {r5, r6, r8, r9, r10, r11, r12, r14}
            ldmia $0!, {r5, r6, r8, r9, r10, r11, r12, r14}
            stmia $1, {r5, r6, r8, r9, r10, r11, r12, r14}
        "   : "+&rm"(table_ptr)
            : "r"(mpu::Rbar::<Srt>::ADDRESS)
            : "r5", "r6", "r8", "r9", "r10", "r11", "r12", "r14"
            : "volatile"
        );
    }

    #[allow(clippy::cast_lossless)]
    const fn rbar_reset(region: u8) -> u32 {
        1 << 4 | region as u32 & 0b1111
    }
}