//! Process management syscalls

use crate::config::PAGE_SIZE;
use crate::mm::{MapPermission, VPNRange, VirtAddr};
use crate::task::{change_program_brk, create_new_map_area, exit_current_and_run_next, get_current_task_page_table_entry, suspend_current_and_run_next, unmap_virtual_page};
use crate::timer::get_time_ms;

/// task exits and submit an exit code
pub fn sys_exit(exit_code: i32) -> ! {
    println!("[kernel] Application exited with code {}", exit_code);
    exit_current_and_run_next();
    panic!("Unreachable in sys_exit!");
}

/// current task gives up resources for other tasks
pub fn sys_yield() -> isize {
    suspend_current_and_run_next();
    0
}

/// get current time
pub fn sys_get_time() -> isize {
    get_time_ms() as isize
}

/// change data segment size
pub fn sys_sbrk(size: i32) -> isize {
    if let Some(old_brk) = change_program_brk(size) {
        old_brk as isize
    } else {
        -1
    }
}

/// map files or devices into memory
pub fn sys_mmap(start: usize, len: usize, prot: usize) -> isize {
    if start % PAGE_SIZE != 0 || prot & !0x7 != 0 || prot & 0x7 == 0 {
        return -1;
    }
    let vpn_start = VirtAddr::from(start).floor();
    let vpn_end = VirtAddr::from(start + len).ceil();
    let vpn_range = VPNRange::new(vpn_start, vpn_end);
    for vpn in vpn_range {
        if let Some(pte) = get_current_task_page_table_entry(vpn) {
            if pte.is_valid() {
                return -1;
            }
        }
    }
    create_new_map_area(
        vpn_start.into(),
        vpn_end.into(),
        MapPermission::from_bits_truncate((prot << 1) as u8) | MapPermission::U
    );
    0
}

/// unmap files or devices into memory
pub fn sys_munmap(start: usize, len: usize) -> isize {
    if start % PAGE_SIZE != 0 {
        return -1;
    }
    let vpn_start = VirtAddr::from(start).floor();
    let vpn_end = VirtAddr::from(start + len).ceil();
    let vpn_range = VPNRange::new(vpn_start, vpn_end);
    for vpn in vpn_range {
        if let Some(pte) = get_current_task_page_table_entry(vpn) {
            if !pte.is_valid() {
                return -1;
            }
            unmap_virtual_page(vpn)
        } else {
            return -1;
        }
    }
    0
}