//! Chip-Generic Interrupt Utilities
//!
//! For the most part, [crate::interrupt::free] is what you want:
//!
//! ```
//! avr_device::interrupt::free(|cs| {
//!     // Interrupts are disabled here
//! });
//! ```
//!
//! To access shared state, Mutex can be used:
//!
//! ```
//! use avr_device::interrupt::Mutex;
//! use core::cell::Cell;
//!
//! // Use Cell, if the wrapped type is Copy.
//! // Use RefCell, if the wrapped type is not Copy or if you need a reference to it for other reasons.
//! static MYGLOBAL: Mutex<Cell<u16>> = Mutex::new(Cell::new(0));
//!
//! avr_device::interrupt::free(|cs| {
//!     // Interrupts are disabled here
//!
//!     // Acquire mutex to global variable.
//!     let myglobal_ref = MYGLOBAL.borrow(&cs);
//!     // Write to the global variable.
//!     myglobal_ref.set(42);
//! });
//! ```

pub use bare_metal::{CriticalSection, Mutex, Nr};

#[cfg(all(target_arch = "avr", avr_device_asm_macro))]
use core::arch::asm;

#[inline]
/// Disables all interrupts
///
/// Returns a bool, reflecting whether interrupts were enabled prior to calling this method.
pub fn disable() -> bool {
    cfg_if::cfg_if! {
        if #[cfg(all(target_arch = "avr", avr_device_asm_macro))] {
            // Store current state
            let sreg: u8;

            unsafe {
                asm!(
                    "in {sreg}, 0x3F",
                    sreg = out(reg) sreg,
                )
            };

            // Disable interrupts
            unsafe { asm!("cli") };

            sreg & 0x80 == 0x80
        } else if #[cfg(target_arch = "avr")] {
            // Store current state
            let sreg: u8;
            unsafe { llvm_asm!("in $0,0x3F" :"=r"(sreg) ::: "volatile") };

            // Disable interrupts
            unsafe { llvm_asm!("cli" :::: "volatile") };

            sreg & 0x80 == 0x80
        } else {
            unimplemented!()
        }
    }
}

#[inline]
/// Enables all the interrupts
///
/// # Safety
///
/// - Do not call this function inside an [crate::interrupt::free] critical section
pub unsafe fn enable() {
    cfg_if::cfg_if! {
        if #[cfg(all(target_arch = "avr", avr_device_asm_macro))] {
            asm!("sei");
        } else if #[cfg(target_arch = "avr")] {
            llvm_asm!("sei" :::: "volatile");
        } else {
            unimplemented!()
        }
    }
}

/// Execute closure `f` in an interrupt-free context.
///
/// This as also known as a "critical section".
pub fn free<F, R>(f: F) -> R
where
    F: FnOnce(&CriticalSection) -> R,
{
    cfg_if::cfg_if! {
        if #[cfg(target_arch = "avr")] {
            // Disable interrupts
            let interrupts_enabled = disable();

            let r = f(unsafe { &CriticalSection::new() });

            // Restore interrupt state
            if interrupts_enabled {
                unsafe { enable(); }
            }

            r
        } else {
            let _ = f;
            unimplemented!()
        }
    }
}