//! Async/await: both executors run tasks to completion, and `yield_now`
//! makes tasks take turns.
#![no_std]
#![no_main]
#![feature(custom_test_frameworks)]
#![test_runner(rust_kernel::test_runner)]
#![reexport_test_harness_main = "test_main"]

extern crate alloc;

use alloc::{rc::Rc, vec, vec::Vec};
use bootloader::{BootInfo, entry_point};
use core::cell::RefCell;
use core::panic::PanicInfo;
use rust_kernel::allocator;
use rust_kernel::memory::{self, BootInfoFrameAllocator};
use rust_kernel::task::{Task, executor::Executor, simple_executor::SimpleExecutor, yield_now};
use x86_64::VirtAddr;

entry_point!(main);

fn main(boot_info: &'static BootInfo) -> ! {
    rust_kernel::init();
    let phys_mem_offset = VirtAddr::new(boot_info.physical_memory_offset);
    let mut mapper = unsafe { memory::init(phys_mem_offset) };
    let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
    allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");

    test_main();
    rust_kernel::hlt_loop();
}

async fn add_one(x: u32) -> u32 {
    x + 1
}

#[test_case]
fn simple_executor_runs_tasks() {
    let result = Rc::new(RefCell::new(0));
    let r = result.clone();
    let mut executor = SimpleExecutor::new();
    executor.spawn(Task::new(async move {
        *r.borrow_mut() = add_one(41).await;
    }));
    executor.run();
    assert_eq!(*result.borrow(), 42);
}

/// Each task logs a step, then yields. With a FIFO task queue they alternate.
async fn logger(name: char, log: Rc<RefCell<Vec<(char, u32)>>>) {
    for step in 1..=3 {
        log.borrow_mut().push((name, step));
        yield_now().await;
    }
}

#[test_case]
fn executor_interleaves_yielding_tasks() {
    let log = Rc::new(RefCell::new(Vec::new()));
    let mut executor = Executor::new();
    executor.spawn(Task::new(logger('a', log.clone())));
    executor.spawn(Task::new(logger('b', log.clone())));
    executor.run_until_done();
    assert_eq!(
        *log.borrow(),
        vec![('a', 1), ('b', 1), ('a', 2), ('b', 2), ('a', 3), ('b', 3)]
    );
}

#[panic_handler]
fn panic(info: &PanicInfo) -> ! {
    rust_kernel::test_panic_handler(info)
}