use super::*;
use memory::{self, Stack, InactivePageTable};
use xmas_elf::{ElfFile, program::{Flags, ProgramHeader}, header::HeaderPt2};
use core::slice;
use alloc::rc::Rc;
use rlibc::memcpy;

#[derive(Debug)]
pub struct Process {
    pub(in process) pid: Pid,
                    name: &'static str,
                    kstack: Stack,
    pub(in process) memory_set: Option<MemorySet>,
    pub(in process) page_table: Option<InactivePageTable>,
    pub(in process) status: Status,
    pub(in process) rsp: usize,
    pub(in process) is_user: bool,
}

pub type Pid = usize;

#[derive(Debug)]
pub enum Status {
    Ready, Running, Sleeping(usize), Exited
}

impl Process {
    /// Make a new kernel thread
    pub fn new(name: &'static str, entry: extern fn(), mc: &mut MemoryController) -> Self {
        let kstack = mc.alloc_stack(7).unwrap();
        let tf = TrapFrame::new_kernel_thread(entry, kstack.top());
        let rsp = kstack.push_at_top(tf);

        Process {
            pid: 0,
            name,
            kstack,
            memory_set: None,
            page_table: None,
            status: Status::Ready,
            rsp,
            is_user: false,
        }
    }

    /// Make the first kernel thread `initproc`
    /// Should be called only once
    pub fn new_init(mc: &mut MemoryController) -> Self {
        assert_has_not_been_called!();
        Process {
            pid: 0,
            name: "init",
            kstack: mc.kernel_stack.take().unwrap(),
            memory_set: None,
            page_table: None,
            status: Status::Running,
            rsp: 0, // will be set at first schedule
            is_user: false,
        }
    }

    /// Make a new user thread
    /// The program elf data is placed at [begin, end)
    /// uCore x86 32bit program is planned to be supported.
    pub fn new_user(begin: usize, end: usize, mc: &mut MemoryController) -> Self {
        // Parse elf
        let slice = unsafe{ slice::from_raw_parts(begin as *const u8, end - begin) };
        let elf = ElfFile::new(slice).expect("failed to read elf");
        let is32 = match elf.header.pt2 {
            HeaderPt2::Header32(_) => true,
            HeaderPt2::Header64(_) => false,
        };

        // User stack
        use consts::{USER_STACK_OFFSET, USER_STACK_SIZE, USER_TCB_OFFSET};
        let (user_stack_buttom, mut user_stack_top) = match is32 {
            true => (USER_TCB_OFFSET, USER_TCB_OFFSET + USER_STACK_SIZE),
            false => (USER_STACK_OFFSET, USER_STACK_OFFSET + USER_STACK_SIZE),
        };

        // Make page table
        let mut memory_set = MemorySet::from(&elf);
        memory_set.push(MemoryArea::new(user_stack_buttom, user_stack_top,
                                        EntryFlags::WRITABLE | EntryFlags::NO_EXECUTE | EntryFlags::USER_ACCESSIBLE, "user_stack"));
        let page_table = mc.make_page_table(&memory_set);
        debug!("{:#x?}", memory_set);

        let entry_addr = match elf.header.pt2 {
            HeaderPt2::Header32(header) => header.entry_point as usize,
            HeaderPt2::Header64(header) => header.entry_point as usize,
        };

        // Temporary switch to it, in order to copy data
        let page_table = mc.with(page_table, || {
            for ph in elf.program_iter() {
                let (virt_addr, offset, file_size) = match ph {
                    ProgramHeader::Ph32(ph) => (ph.virtual_addr as usize, ph.offset as usize, ph.file_size as usize),
                    ProgramHeader::Ph64(ph) => (ph.virtual_addr as usize, ph.offset as usize, ph.file_size as usize),
                };
                unsafe { memcpy(virt_addr as *mut u8, (begin + offset) as *mut u8, file_size) };
            }
            if is32 {
                unsafe {
                    // TODO: full argc & argv
                    *(user_stack_top as *mut u32).offset(-1) = 0; // argv
                    *(user_stack_top as *mut u32).offset(-2) = 0; // argc
                    user_stack_top -= 8;
                }
            }
        });


        // Allocate kernel stack and push trap frame
        let kstack = mc.alloc_stack(7).unwrap();
        let tf = TrapFrame::new_user_thread(entry_addr, user_stack_top, is32);
        let rsp = kstack.push_at_top(tf);
        debug!("rsp = {:#x}", rsp);

        Process {
            pid: 0,
            name: "user",
            kstack,
            memory_set: Some(memory_set),
            page_table: Some(page_table),
            status: Status::Ready,
            rsp,
            is_user: true,
        }
    }

    /// Fork
    pub fn fork(&self, tf: &TrapFrame, mc: &mut MemoryController) -> Self {
        assert!(self.is_user);

        // Clone memory set, make a new page table
        let memory_set = self.memory_set.as_ref().unwrap().clone();
        let page_table = mc.make_page_table(&memory_set);

        // Copy data to temp space
        use alloc::Vec;
        let datas: Vec<Vec<u8>> = memory_set.iter().map(|area| {
            Vec::from(unsafe { area.as_slice() })
        }).collect();

        // Temporary switch to it, in order to copy data
        let page_table = mc.with(page_table, || {
            for (area, data) in memory_set.iter().zip(datas.iter()) {
                unsafe { area.as_slice_mut() }.copy_from_slice(data.as_slice())
            }
        });

        // Allocate kernel stack and push trap frame
        let kstack = mc.alloc_stack(7).unwrap();
        let mut tf = tf.clone();
        tf.scratch.rax = 1;
        let rsp = kstack.push_at_top(tf);

        Process {
            pid: 0,
            name: "fork",
            kstack,
            memory_set: Some(memory_set),
            page_table: Some(page_table),
            status: Status::Ready,
            rsp,
            is_user: true,
        }
    }
}

use memory::{MemorySet, MemoryArea, PhysAddr, FromToVirtualAddress, EntryFlags};

impl<'a> From<&'a ElfFile<'a>> for MemorySet {
    fn from(elf: &'a ElfFile<'a>) -> Self {
        let mut set = MemorySet::new();
        for ph in elf.program_iter() {
            let (virt_addr, mem_size, flags) = match ph {
                ProgramHeader::Ph32(ph) => (ph.virtual_addr as usize, ph.mem_size as usize, ph.flags),
                ProgramHeader::Ph64(ph) => (ph.virtual_addr as usize, ph.mem_size as usize, ph.flags),
            };
            set.push(MemoryArea::new(virt_addr, virt_addr + mem_size, EntryFlags::from(flags), ""));
        }
        set
    }
}

impl From<Flags> for EntryFlags {
    fn from(elf_flags: Flags) -> Self {
        let mut flags = EntryFlags::PRESENT | EntryFlags::USER_ACCESSIBLE;
//        if elf_flags.is_write() {
        // TODO: handle readonly
        if true {
            flags = flags | EntryFlags::WRITABLE;
        }
        if !elf_flags.is_execute() {
            flags = flags | EntryFlags::NO_EXECUTE;
        }
        flags
    }
}