burritos/src/kernel/thread.rs

use std::{sync::Arc};

use super::{process::Process, mgerror::ErrorCode, system::{ObjectType, G_ALIVE, G_SCHEDULER}, ucontext::UContextT};
use crate::{simulator::machine::{NUM_INT_REGS, NUM_FP_REGS, STACK_REG}, kernel::system::{G_MACHINE, G_THREAD_TO_BE_DESTROYED}};

const SIMULATORSTACKSIZE: usize = 32 * 1024;
const STACK_FENCEPOST: u32 = 0xdeadbeef;

#[derive(PartialEq)]
struct ThreadContext {
    pub int_registers: [i64; NUM_INT_REGS],
    pub float_registers: [i64; NUM_FP_REGS],
    pc: i64,
}

#[derive(PartialEq)]
pub struct Thread {
    name: String,
    process: Option<Process>,
    // simulation_context: UContextT,
    thread_context: ThreadContext,
    stack_pointer: i32,
    object_type: ObjectType
}

impl Thread {

    pub fn new(name: String) -> Self {
        Self {
            name,
            process: None,
            // simulation_context: UContextT::new(),
            thread_context: ThreadContext { 
                int_registers: [0; NUM_INT_REGS], 
                float_registers: [0; NUM_FP_REGS], 
                pc: 0 
            },
            stack_pointer: 0,
            object_type: ObjectType::ThreadType
        }
    }

    /// Start a thread, attaching it to a process
    pub fn start(mut self, owner: Process, func: i64, arg: i64) -> Result<(), ErrorCode> {
        self.process = Option::Some(owner);
        let ptr = 0; // todo addrspace
        self.init_thread_context(func, ptr, arg);
        let base_stack_addr: [i8; SIMULATORSTACKSIZE] = [0; SIMULATORSTACKSIZE]; // todo AllocBoundedArray
        self.init_simulator_context(base_stack_addr);
        self.process.as_mut().unwrap().num_thread += 1;
        match G_ALIVE.write() {
            Ok(mut alive) => {
                let this = Arc::new(self);
                alive.push(Arc::clone(&this));
                match G_SCHEDULER.write() {
                    Ok(mut scheduler) => {
                        scheduler.ready_to_run(Arc::clone(&this));
                    },
                    Err(err) => {
                        panic!("RwLock poisonned, {}", err);
                    }
                }
            },
            Err(err) => {
                panic!("RwLock poisonned, {}", err);
            }
        }
        Result::Ok(())
    }

    fn init_thread_context(&mut self, initial_pc_reg: i64, initial_sp: i64, arg: i64) {
        self.thread_context.pc = initial_pc_reg;
        self.thread_context.int_registers[10] = arg;
        self.thread_context.int_registers[STACK_REG] = initial_sp;
    }

    fn init_simulator_context(&self, base_stack_addr: [i8; SIMULATORSTACKSIZE]) {
        // let res = self.simulation_context.get_context();
        // if res != 0 {
        //     panic!("getcontext returns non-zero value {}", res);
        // }
        // self.simulation_context.buf.uc_stack.ss_sp = base_stack_addr;
        // self.simulation_context.buf.uc_stack.ss_size = base_stack_addr.len();
        // self.simulation_context.buf.uc_stack.ss_flags = 0;
        // self.simulation_context.buf.uc_link = UContextT::new().buf;
        // self.simulation_context.make_context(start_thread_execution, 0);

        // self.simulation_context.stackBottom = base_stack_addr.to_vec();
        // self.simulation_context.stackBottom[0] = STACK_FENCEPOST;
    }

    /// Wait for another thread to finish its execution
    pub fn join(&self, id_thread: Arc<Thread>) {
        match G_ALIVE.write() {
            Ok(alive) => {
                while alive.contains(&Arc::clone(&id_thread)) {
                    self.t_yield();
                }
            },
            Err(err) => {
                panic!("RwLock poisonned, {}", err)
            }
        }
    }

    /// Relinquish the CPU if any other thread is runnable.
    /// 
    /// Cannot use yield as a function name -> reserved name in rust
    pub fn t_yield(&self) {
        todo!();
    }

    /// Put the thread to sleep and relinquish the processor
    pub fn sleep(&self) {
        todo!();
    }

    /// Finish the execution of the thread and prepare its deallocation
    pub fn finish(mut self) {
        match G_MACHINE.write() {
            Ok(mut machine) => {
                let old_status = machine.interrupt.set_status(crate::simulator::interrupt::InterruptStatus::InterruptOff);
                match G_ALIVE.write() {
                    Ok(alive) => {
                        // todo alive.remove(T) à implémenter dans List
                    },
                    Err(err) => {
                        panic!("RwLock is poisoned: {}", err);
                    }
                }
                match G_THREAD_TO_BE_DESTROYED.write() {
                    Ok(mut thread_to_be_destroyed) => {
                        thread_to_be_destroyed.replace(self);
                    },
                    Err(err) => {
                        panic!("RwLock is poisoned: {}", err);
                    }
                }
                // self.sleep();
                machine.interrupt.set_status(old_status);
            },
            Err(err) => {
                panic!("RwLock is poisoned: {}", err);
            }
        }
        
        todo!();
    }
    
    /// Check if a thread has overflowed its stack
    pub fn check_overflow(&self) {
        todo!();
    }

    pub fn save_processor_state(&self) {
        todo!();
    }

    pub fn restore_processor_state(&self) {
        todo!();
    }

    pub fn save_simulator_state(&self) {
        todo!();
    }

    pub fn restore_simulator_state(&self) {
        todo!();
    }

    pub fn get_name(&self) -> String {
        self.name.clone()
    }

}

impl Drop for Thread {

    fn drop(&mut self) {
        self.object_type = ObjectType::InvalidType;
        todo!();
    }

}

fn start_thread_execution() {
    
}