use {
    alloc::{collections::VecDeque, rc::Rc, slice, vec::Vec},
    hbvm::validate::validate,
};

use {crate::host::TrapHandler, hbvm::Vm};
const TIMER_QUOTIENT: usize = 100;

pub struct Scheduler<'a> {
    data: VecDeque<Vm<'a, TrapHandler, TIMER_QUOTIENT>>,
}

// NOTE: This is a very simple schduler and it sucks and should be replaced with a better one
// Written By Yours Truly: Munir

impl Scheduler<'_> {
    pub fn new() -> Self {
        Self {
            data: VecDeque::new(),
        }
    }
    pub fn new_process(&mut self, program: Vec<u8>) {
        let prog = program.clone();
        let prog_arc = Rc::new(prog);

        let binding = Rc::try_unwrap(prog_arc).ok().unwrap();

        #[allow(clippy::redundant_else)]
        if let Err(e) = validate(&program.as_slice()) {
            log::error!("Program validation error: {e:?}");
        } else {
            log::info!("valid program");
            unsafe {
                let slice = slice::from_raw_parts(binding.as_ptr(), binding.len());
                let mut vm = Vm::new_unchecked(&*slice, TrapHandler);
                vm.memory.insert_test_page();
                self.data.push_front(vm);
            }
        }
    }

    pub fn run(&mut self) -> ! {
        loop {
            // If there are no programs to run then sleep.
            if self.data.is_empty() {
                use crate::arch::spin_loop;
                spin_loop();
            }

            let mut prog = self.data.pop_front().unwrap();
            let ret = prog.run();
            match ret {
                Ok(oki) => match oki {
                    hbvm::VmRunOk::End => {
                        log::info!(
                            "Program ended. {} programs remaining.",
                            // Add one here because we pop a program
                            self.data.len() + 1
                        )
                    }
                    hbvm::VmRunOk::Timer => {
                        log::info!("Timer exhausted. Scheduled program");
                        self.data.push_back(prog);
                    }
                    hbvm::VmRunOk::Ecall => {
                        // panic!();
                        log::info!("{:?}", prog.registers);
                        self.data.push_back(prog);
                    }
                },

                Err(_) => {}
            }
        }
    }
}