///! Process syscalls

use core::mem;
use core::str;

use arch;
use arch::paging::{VirtualAddress, entry};
use context;
use elf;
use syscall::{self, Error, Result};

pub fn brk(address: usize) -> Result<usize> {
    let contexts = context::contexts();
    let context_lock = contexts.current().ok_or(Error::NoProcess)?;
    let mut context = context_lock.write();

    let mut current = arch::USER_HEAP_OFFSET;
    if let Some(ref heap) = context.heap {
        current = heap.start_address().get() + heap.size();
    }
    if address == 0 {
        //println!("Brk query {:X}", current);
        Ok(current)
    } else if address >= arch::USER_HEAP_OFFSET {
        //TODO: out of memory errors
        if let Some(ref mut heap) = context.heap {
            heap.resize(address - arch::USER_HEAP_OFFSET, true, true);
            return Ok(address);
        }

        context.heap = Some(context::memory::Memory::new(
            VirtualAddress::new(arch::USER_HEAP_OFFSET),
            address - arch::USER_HEAP_OFFSET,
            entry::WRITABLE | entry::NO_EXECUTE | entry::USER_ACCESSIBLE,
            true,
            true
        ));

        Ok(address)
    } else {
        //TODO: Return correct error
        Err(Error::NotPermitted)
    }
}

pub fn clone(flags: usize, stack_base: usize) -> Result<usize> {
    println!("Clone {:X}: {:X}", flags, stack_base);

    let arch;
    let mut kstack_option = None;
    let mut offset = 0;
    let mut stack_option = None;

    // Copy from old process
    {
        let contexts = context::contexts();
        let context_lock = contexts.current().ok_or(Error::NoProcess)?;
        let context = context_lock.read();
        arch = context.arch.clone();
        if let Some(ref stack) = context.kstack {
            offset = stack_base - stack.as_ptr() as usize - mem::size_of::<usize>(); // Add clone ret
            let mut new_stack = stack.clone();
            unsafe {
                let func_ptr = new_stack.as_mut_ptr().offset(offset as isize);
                *(func_ptr as *mut usize) = arch::interrupt::syscall::clone_ret as usize;
            }
            kstack_option = Some(new_stack);
        }
        if let Some(ref stack) = context.stack {
            let mut new_stack = context::memory::Memory::new(
                VirtualAddress::new(arch::USER_TMP_STACK_OFFSET),
                stack.size(),
                entry::NO_EXECUTE | entry::WRITABLE | entry::USER_ACCESSIBLE,
                true,
                true //TODO: Don't clear stack?
            );
            unsafe {
                arch::externs::memcpy(new_stack.start_address().get() as *mut u8,
                                      stack.start_address().get() as *const u8,
                                      stack.size());
            }
            new_stack.unmap(true);
            stack_option = Some(new_stack);
        }
    }

    // Set up new process
    let pid;
    {
        let mut contexts = context::contexts_mut();
        let context_lock = contexts.new_context()?;
        let mut context = context_lock.write();
        context.arch = arch;
        if let Some(stack) = kstack_option.take() {
            context.arch.set_stack(stack.as_ptr() as usize + offset);
            context.kstack = Some(stack);
        }
        if let Some(mut stack) = stack_option.take() {
            //stack.replace(VirtualAddress::new(arch::USER_STACK_OFFSET), true);
            context.stack = Some(stack);
        }
        context.blocked = false;
        pid = context.id;
    }

    //unsafe { context::switch(); }

    Ok(pid)
}

pub fn exit(status: usize) -> ! {
    println!("Exit {}", status);

    {
        let contexts = context::contexts();
        let context_lock = contexts.current().expect("tried to exit without context");
        let mut context = context_lock.write();
        context.image.clear();
        drop(context.heap.take());
        drop(context.stack.take());
        context.exited = true;
    }

    unsafe { context::switch(); }

    unreachable!();
}

pub fn exec(path: &[u8], _args: &[[usize; 2]]) -> Result<usize> {
    //TODO: Use args
    //TODO: Unmap previous mappings
    //TODO: Drop data vec
    println!("Exec {}", unsafe { str::from_utf8_unchecked(path) });

    let file = syscall::open(path, 0)?;
    let mut data = vec![];
    loop {
        let mut buf = [0; 4096];
        let count = syscall::read(file, &mut buf)?;
        if count > 0 {
            data.extend_from_slice(&buf[..count]);
        } else {
            break;
        }
    }
    let _ = syscall::close(file);

    match elf::Elf::from(&data) {
        Ok(elf) => elf.run().and(Ok(0)),
        Err(err) => {
            println!("failed to execute {}: {}", unsafe { str::from_utf8_unchecked(path) }, err);
            Err(Error::NoExec)
        }
    }
}

pub fn getpid() -> Result<usize> {
    let contexts = context::contexts();
    let context_lock = contexts.current().ok_or(Error::NoProcess)?;
    let context = context_lock.read();
    Ok(context.id)
}

pub fn iopl(_level: usize) -> Result<usize> {
    //TODO
    Ok(0)
}

pub fn sched_yield() -> Result<usize> {
    unsafe { context::switch(); }
    Ok(0)
}