//! Syscalls for process

use super::*;
use crate::fs::INodeExt;

impl Syscall<'_> {
    /// Fork the current process. Return the child's PID.
    pub fn sys_fork(&mut self) -> SysResult {
        let new_thread = self.thread.fork(self.tf);
        let pid = new_thread.proc.lock().pid.get();
        let tid = processor().manager().add(new_thread);
        processor().manager().detach(tid);
        info!("fork: {} -> {}", thread::current().id(), pid);
        Ok(pid)
    }

    pub fn sys_vfork(&mut self) -> SysResult {
        self.sys_fork()
    }

    /// Create a new thread in the current process.
    /// The new thread's stack pointer will be set to `newsp`,
    /// and thread pointer will be set to `newtls`.
    /// The child tid will be stored at both `parent_tid` and `child_tid`.
    /// This is partially implemented for musl only.
    pub fn sys_clone(
        &mut self,
        flags: usize,
        newsp: usize,
        parent_tid: *mut u32,
        child_tid: *mut u32,
        newtls: usize,
    ) -> SysResult {
        let clone_flags = CloneFlags::from_bits_truncate(flags);
        info!(
            "clone: flags: {:?} == {:#x}, newsp: {:#x}, parent_tid: {:?}, child_tid: {:?}, newtls: {:#x}",
            clone_flags, flags, newsp, parent_tid, child_tid, newtls
        );
        if flags == 0x4111 || flags == 0x11 {
            warn!("sys_clone is calling sys_fork instead, ignoring other args");
            return self.sys_fork();
        }
        if (flags != 0x7d0f00) && (flags != 0x5d0f00) {
            //0x5d0f00 is the args from gcc of alpine linux
            //warn!("sys_clone only support musl pthread_create");
            panic!(
                "sys_clone only support sys_fork OR musl pthread_create without flags{:x}",
                flags
            );
            //return Err(SysError::ENOSYS);
        }
        let parent_tid_ref = unsafe { self.process().vm.check_write_ptr(parent_tid)? };
        let child_tid_ref = unsafe { self.process().vm.check_write_ptr(child_tid)? };
        let new_thread = self
            .thread
            .clone(self.tf, newsp, newtls, child_tid as usize);
        // FIXME: parent pid
        let tid = processor().manager().add(new_thread);
        processor().manager().detach(tid);
        info!("clone: {} -> {}", thread::current().id(), tid);
        *parent_tid_ref = tid as u32;
        *child_tid_ref = tid as u32;
        Ok(tid)
    }

    /// Wait for the process exit.
    /// Return the PID. Store exit code to `wstatus` if it's not null.
    pub fn sys_wait4(&mut self, pid: isize, wstatus: *mut i32) -> SysResult {
        //info!("wait4: pid: {}, code: {:?}", pid, wstatus);
        let wstatus = if !wstatus.is_null() {
            Some(unsafe { self.process().vm.check_write_ptr(wstatus)? })
        } else {
            None
        };
        #[derive(Debug)]
        enum WaitFor {
            AnyChild,
            Pid(usize),
        }
        let target = match pid {
            -1 | 0 => WaitFor::AnyChild,
            p if p > 0 => WaitFor::Pid(p as usize),
            _ => unimplemented!(),
        };
        loop {
            let mut proc = self.process();
            // check child_exit_code
            let find = match target {
                WaitFor::AnyChild => proc
                    .child_exit_code
                    .iter()
                    .next()
                    .map(|(&pid, &code)| (pid, code)),
                WaitFor::Pid(pid) => proc.child_exit_code.get(&pid).map(|&code| (pid, code)),
            };
            // if found, return
            if let Some((pid, exit_code)) = find {
                proc.child_exit_code.remove(&pid);
                if let Some(wstatus) = wstatus {
                    *wstatus = exit_code as i32;
                }
                return Ok(pid);
            }
            // if not, check pid
            let children: Vec<_> = proc
                .children
                .iter()
                .filter_map(|weak| weak.upgrade())
                .collect();
            let invalid = match target {
                WaitFor::AnyChild => children.len() == 0,
                WaitFor::Pid(pid) => children
                    .iter()
                    .find(|p| p.lock().pid.get() == pid)
                    .is_none(),
            };
            if invalid {
                return Err(SysError::ECHILD);
            }
            info!(
                "wait: thread {} -> {:?}, sleep",
                thread::current().id(),
                target
            );
            let condvar = proc.child_exit.clone();
            condvar.wait(proc);
        }
    }

    /// Replaces the current ** process ** with a new process image
    ///
    /// `argv` is an array of argument strings passed to the new program.
    /// `envp` is an array of strings, conventionally of the form `key=value`,
    /// which are passed as environment to the new program.
    ///
    /// NOTICE: `argv` & `envp` can not be NULL (different from Linux)
    ///
    /// NOTICE: for multi-thread programs
    /// A call to any exec function from a process with more than one thread
    /// shall result in all threads being terminated and the new executable image
    /// being loaded and executed.
    pub fn sys_exec(
        &mut self,
        path: *const u8,
        argv: *const *const u8,
        envp: *const *const u8,
    ) -> SysResult {
        info!(
            "exec:BEG: path: {:?}, argv: {:?}, envp: {:?}",
            path, argv, envp
        );
        let mut proc = self.process();
        let path = unsafe { proc.vm.check_and_clone_cstr(path)? };
        let args = unsafe { proc.vm.check_and_clone_cstr_array(argv)? };
        let envs = unsafe { proc.vm.check_and_clone_cstr_array(envp)? };

        if args.is_empty() {
            error!("exec: args is null");
            return Err(SysError::EINVAL);
        }

        info!(
            "exec:STEP2: path: {:?}, args: {:?}, envs: {:?}",
            path, args, envs
        );

        // Kill other threads
        proc.threads.retain(|&tid| {
            if tid != processor().tid() {
                processor().manager().exit(tid, 1);
            }
            tid == processor().tid()
        });

        // Read program file
        let inode = proc.lookup_inode(&path)?;

        // Make new Thread
        let (mut vm, entry_addr, ustack_top) =
            Thread::new_user_vm(&inode, &path, args, envs).map_err(|_| SysError::EINVAL)?;

        // Activate new page table
        core::mem::swap(&mut proc.vm, &mut vm);
        unsafe {
            proc.vm.activate();
        }

        // Modify exec path
        proc.exec_path = path.clone();
        drop(proc);

        // Modify the TrapFrame
        *self.tf = TrapFrame::new_user_thread(entry_addr, ustack_top);

        info!("exec:END: path: {:?}", path);
        Ok(0)
    }

    pub fn sys_yield(&mut self) -> SysResult {
        thread::yield_now();
        Ok(0)
    }

    /// Kill the process
    pub fn sys_kill(&mut self, pid: usize, sig: usize) -> SysResult {
        info!(
            "kill: {} killed: {} with sig {}",
            thread::current().id(),
            pid,
            sig
        );
        let current_pid = self.process().pid.get().clone();
        if current_pid == pid {
            // killing myself
            self.sys_exit_group(sig);
        } else {
            if let Some(proc_arc) = PROCESSES.read().get(&pid).and_then(|weak| weak.upgrade()) {
                let proc = proc_arc.lock();
                // quit all threads
                for tid in proc.threads.iter() {
                    processor().manager().exit(*tid, sig);
                }
                // notify parent and fill exit code
                // avoid deadlock
                let proc_parent = proc.parent.clone();
                let pid = proc.pid.get();
                drop(proc);
                if let Some(parent) = proc_parent {
                    let mut parent = parent.lock();
                    parent.child_exit_code.insert(pid, sig);
                    parent.child_exit.notify_one();
                }
                Ok(0)
            } else {
                Err(SysError::EINVAL)
            }
        }
    }

    /// Get the current process id
    pub fn sys_getpid(&mut self) -> SysResult {
        info!("getpid");
        Ok(self.process().pid.get())
    }

    /// Get the current thread id
    pub fn sys_gettid(&mut self) -> SysResult {
        info!("gettid");
        // use pid as tid for now
        Ok(thread::current().id())
    }

    /// Get the parent process id
    pub fn sys_getppid(&mut self) -> SysResult {
        if let Some(parent) = self.process().parent.as_ref() {
            Ok(parent.lock().pid.get())
        } else {
            Ok(0)
        }
    }

    /// Exit the current thread
    pub fn sys_exit(&mut self, exit_code: usize) -> ! {
        let tid = thread::current().id();
        info!("exit: {}, code: {}", tid, exit_code);
        let mut proc = self.process();
        proc.threads.retain(|&id| id != tid);

        // for last thread,
        // notify parent and fill exit code
        // avoid deadlock
        let exit = proc.threads.len() == 0;
        let proc_parent = proc.parent.clone();
        let pid = proc.pid.get();
        drop(proc);
        if exit {
            if let Some(parent) = proc_parent {
                let mut parent = parent.lock();
                parent.child_exit_code.insert(pid, exit_code);
                parent.child_exit.notify_one();
            }
        }

        // perform futex wake 1
        // ref: http://man7.org/linux/man-pages/man2/set_tid_address.2.html
        // FIXME: do it in all possible ways a thread can exit
        //        it has memory access so we can't move it to Thread::drop?
        let mut proc = self.process();
        let clear_child_tid = self.thread.clear_child_tid as *mut u32;
        if !clear_child_tid.is_null() {
            info!("exit: futex {:#?} wake 1", clear_child_tid);
            if let Ok(clear_child_tid_ref) = unsafe { proc.vm.check_write_ptr(clear_child_tid) } {
                *clear_child_tid_ref = 0;
                let queue = proc.get_futex(clear_child_tid as usize);
                queue.notify_one();
            }
        }
        drop(proc);

        processor().manager().exit(tid, exit_code as usize);
        processor().yield_now();
        unreachable!();
    }

    /// Exit the current thread group (i.e. process)
    pub fn sys_exit_group(&mut self, exit_code: usize) -> ! {
        let proc = self.process();
        info!("exit_group: {}, code: {}", proc.pid, exit_code);

        // quit all threads
        for tid in proc.threads.iter() {
            processor().manager().exit(*tid, exit_code);
        }

        // notify parent and fill exit code
        // avoid deadlock
        let proc_parent = proc.parent.clone();
        let pid = proc.pid.get();
        drop(proc);
        if let Some(parent) = proc_parent {
            let mut parent = parent.lock();
            parent.child_exit_code.insert(pid, exit_code);
            parent.child_exit.notify_one();
        }

        processor().yield_now();
        unreachable!();
    }

    pub fn sys_nanosleep(&mut self, req: *const TimeSpec) -> SysResult {
        let time = unsafe { *self.process().vm.check_read_ptr(req)? };
        info!("nanosleep: time: {:#?}", time);
        // TODO: handle spurious wakeup
        thread::sleep(time.to_duration());
        Ok(0)
    }

    pub fn sys_set_priority(&mut self, priority: usize) -> SysResult {
        let pid = thread::current().id();
        processor().manager().set_priority(pid, priority as u8);
        Ok(0)
    }

    pub fn sys_set_tid_address(&mut self, tidptr: *mut u32) -> SysResult {
        info!("set_tid_address: {:?}", tidptr);
        self.thread.clear_child_tid = tidptr as usize;
        Ok(thread::current().id())
    }
}

bitflags! {
    pub struct CloneFlags: usize {
        const CSIGNAL = 0x000000ff;
        const VM = 0x0000100;
        const FS = 0x0000200;
        const FILES = 0x0000400;
        const SIGHAND = 0x0000800;
        const PTRACE = 0x0002000;
        const VFORK = 0x0004000;
        const PARENT = 0x0008000;
        const SYSVSEM = 0x0008000;
        const SETTLS = 0x0008000;
        const PARENT_SETTID = 0x0010000;
        const CHILD_CLEARTID = 0x0020000;
        const DETACHED = 0x0040000;
        const UNTRACED = 0x0080000;
        const CHILD_SETTID = 0x0100000;
        const NEWCGROUP = 0x0200000;
        const NEWUTS = 0x0400000;
        const NEWIPC = 0x0800000;
        const NEWUSER = 0x1000000;
        const NEWPID = 0x2000000;
        const NEWNET = 0x4000000;
        const IO = 0x8000000;
    }
}