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    use super::__switch;
    use super::{fetch_task, TaskStatus};
    use super::{ProcessControlBlock, TaskContext, TaskControlBlock};
    use crate::sync::UPIntrFreeCell;
    use crate::trap::TrapContext;
    use alloc::sync::Arc;
    use lazy_static::*;

    pub struct Processor {
        current: Option<Arc<TaskControlBlock>>,
        idle_task_cx: TaskContext,
    }

    impl Processor {
        pub fn new() -> Self {
            Self {
                current: None,
                idle_task_cx: TaskContext::zero_init(),
            }
        }
        fn get_idle_task_cx_ptr(&mut self) -> *mut TaskContext {
            &mut self.idle_task_cx as *mut _
        }
        pub fn take_current(&mut self) -> Option<Arc<TaskControlBlock>> {
            self.current.take()
        }
        pub fn current(&self) -> Option<Arc<TaskControlBlock>> {
            self.current.as_ref().map(Arc::clone)
        }
    }

    lazy_static! {
        pub static ref PROCESSOR: UPIntrFreeCell<Processor> = {
            kprintln!("[KERN] task::processor::lazy_static!PROCESSOR begin");
            unsafe { UPIntrFreeCell::new(Processor::new()) }
        };
    }

    pub fn run_tasks() {
        kprintln!("[KERN] task::processor::run_tasks() begin");
        loop {
            let mut processor = PROCESSOR.exclusive_access();
            if let Some(task) = fetch_task() {
                let idle_task_cx_ptr = processor.get_idle_task_cx_ptr();
                // access coming task TCB exclusively
                let next_task_cx_ptr = task.inner.exclusive_session(|task_inner| {
                    task_inner.task_status = TaskStatus::Running;
                    &task_inner.task_cx as *const TaskContext
                });
                processor.current = Some(task);
                // release processor manually
                drop(processor);
                unsafe {
                    __switch(idle_task_cx_ptr, next_task_cx_ptr);
                }
            } else {
                println!("no tasks available in run_tasks");
            }
        }
    }

    pub fn take_current_task() -> Option<Arc<TaskControlBlock>> {
        PROCESSOR.exclusive_access().take_current()
    }

    pub fn current_task() -> Option<Arc<TaskControlBlock>> {
        PROCESSOR.exclusive_access().current()
    }

    pub fn current_process() -> Arc<ProcessControlBlock> {
        current_task().unwrap().process.upgrade().unwrap()
    }

    pub fn current_user_token() -> usize {
        let task = current_task().unwrap();
        task.get_user_token()
    }

    pub fn current_trap_cx() -> &'static mut TrapContext {
        current_task()
            .unwrap()
            .inner_exclusive_access()
            .get_trap_cx()
    }

    pub fn current_trap_cx_user_va() -> usize {
        current_task()
            .unwrap()
            .inner_exclusive_access()
            .res
            .as_ref()
            .unwrap()
            .trap_cx_user_va()
    }

    pub fn current_kstack_top() -> usize {
        current_task().unwrap().kstack.get_top()
    }

    pub fn schedule(switched_task_cx_ptr: *mut TaskContext) {
        let idle_task_cx_ptr = PROCESSOR.exclusive_session(|processor| {
            processor.get_idle_task_cx_ptr()
        });
        unsafe {
            __switch(switched_task_cx_ptr, idle_task_cx_ptr);
        }
    }