use crate::arch::interrupt::{TrapFrame, Context as ArchContext};
use crate::memory::{MemoryArea, MemoryAttr, MemorySet, KernelStack, InactivePageTable0, GlobalFrameAlloc, FrameAllocator};
use xmas_elf::{ElfFile, header, program::{Flags, ProgramHeader, Type, SegmentData}};
use core::fmt::{Debug, Error, Formatter};
use alloc::{boxed::Box, collections::BTreeMap, vec::Vec, sync::Arc, string::String};
use ucore_memory::{Page};
use ucore_memory::memory_set::*;
use ucore_process::Context;
use simple_filesystem::file::File;
use spin::Mutex;
use log::*;


// TODO: avoid pub
pub struct ContextImpl {
    pub arch: ArchContext,
    pub memory_set: MemorySet,
    pub kstack: KernelStack,
    pub files: BTreeMap<usize, Arc<Mutex<File>>>,
    pub cwd: String,
}

impl Context for ContextImpl {
    unsafe fn switch_to(&mut self, target: &mut Context) {
        use core::mem::transmute;
        let (target, _): (&mut ContextImpl, *const ()) = transmute(target);
        self.arch.switch(&mut target.arch);
    }
}

impl ContextImpl {
    pub unsafe fn new_init() -> Box<Context> {
        Box::new(ContextImpl {
            arch: ArchContext::null(),
            memory_set: MemorySet::new(),
            kstack: KernelStack::new(),
            files: BTreeMap::default(),
            cwd: String::new(),
        })
    }

    pub fn new_kernel(entry: extern fn(usize) -> !, arg: usize) -> Box<Context> {
        let memory_set = MemorySet::new();
        let kstack = KernelStack::new();
        Box::new(ContextImpl {
            arch: unsafe { ArchContext::new_kernel_thread(entry, arg, kstack.top(), memory_set.token()) },
            memory_set,
            kstack,
            files: BTreeMap::default(),
            cwd: String::new(),
        })
    }

    /// Make a new user thread from ELF data
    pub fn new_user<'a, Iter>(data: &[u8], args: Iter) -> Box<ContextImpl>
        where Iter: Iterator<Item=&'a str>
    {
        // Parse elf
        let elf = ElfFile::new(data).expect("failed to read elf");
        let is32 = match elf.header.pt2 {
            header::HeaderPt2::Header32(_) => true,
            header::HeaderPt2::Header64(_) => false,
        };

        match elf.header.pt2.type_().as_type() {
            header::Type::Executable => {
//                #[cfg(feature = "no_mmu")]
//                panic!("ELF is not shared object");
            },
            header::Type::SharedObject => {},
            _ => panic!("ELF is not executable or shared object"),
        }

        // Make page table
        let (mut memory_set, entry_addr) = memory_set_from(&elf);

        // User stack
        use crate::consts::{USER_STACK_OFFSET, USER_STACK_SIZE, USER32_STACK_OFFSET};
        #[cfg(not(feature = "no_mmu"))]
        let mut ustack_top = {
            let (ustack_buttom, ustack_top) = match is32 {
                true => (USER32_STACK_OFFSET, USER32_STACK_OFFSET + USER_STACK_SIZE),
                false => (USER_STACK_OFFSET, USER_STACK_OFFSET + USER_STACK_SIZE),
            };
            memory_set.push(ustack_buttom, ustack_top,  handler::ByFrame::new(MemoryAttr::default().user(), GlobalFrameAlloc), "user_stack");
            ustack_top
        };
        #[cfg(feature = "no_mmu")]
        let mut ustack_top = memory_set.push(USER_STACK_SIZE).as_ptr() as usize + USER_STACK_SIZE;

        unsafe {
            memory_set.with(|| { ustack_top = push_args_at_stack(args, ustack_top) });
        }

        trace!("{:#x?}", memory_set);

        let kstack = KernelStack::new();

        Box::new(ContextImpl {
            arch: unsafe {
                ArchContext::new_user_thread(
                    entry_addr, ustack_top, kstack.top(), is32, memory_set.token())
            },
            memory_set,
            kstack,
            files: BTreeMap::default(),
            cwd: String::new(),
        })
    }

    /// Fork
    pub fn fork(&self, tf: &TrapFrame) -> Box<Context> {
        info!("COME into fork!");
        // Clone memory set, make a new page table
        let mut memory_set = self.memory_set.clone();
        info!("finish mmset clone in fork!");

        // MMU:   copy data to the new space
        // NoMMU: coping data has been done in `memory_set.clone()`
        #[cfg(not(feature = "no_mmu"))]
        for area in memory_set.iter() {
            let data = Vec::<u8>::from(unsafe { area.as_slice() });
            unsafe { memory_set.with(|| {
                area.as_slice_mut().copy_from_slice(data.as_slice())
            }) }
        }

        info!("temporary copy data!");
        let kstack = KernelStack::new();

        Box::new(ContextImpl {
            arch: unsafe { ArchContext::new_fork(tf, kstack.top(), memory_set.token()) },
            memory_set,
            kstack,
            files: BTreeMap::default(),
            cwd: String::new(),
        })
    }
}

impl Debug for ContextImpl {
    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
        write!(f, "{:x?}", self.arch)
    }
}

/// Push a slice at the stack. Return the new sp.
unsafe fn push_slice<T: Copy>(mut sp: usize, vs: &[T]) -> usize {
    use core::{mem::{size_of, align_of}, slice};
    sp -= vs.len() * size_of::<T>();
    sp -= sp % align_of::<T>();
    slice::from_raw_parts_mut(sp as *mut T, vs.len())
        .copy_from_slice(vs);
    sp
}

unsafe fn push_args_at_stack<'a, Iter>(args: Iter, stack_top: usize) -> usize
    where Iter: Iterator<Item=&'a str>
{
    use core::{ptr, slice};
    let mut sp = stack_top;
    let mut argv = Vec::new();
    for arg in args {
        sp = push_slice(sp, &[0u8]);
        sp = push_slice(sp, arg.as_bytes());
        argv.push(sp);
    }
    sp = push_slice(sp, argv.as_slice());
    sp = push_slice(sp, &[argv.len()]);
    sp
}


/// Generate a MemorySet according to the ELF file.
/// Also return the real entry point address.
fn memory_set_from<'a>(elf: &'a ElfFile<'a>) -> (MemorySet, usize) {
    debug!("come in to memory_set_from");
    let mut ms = MemorySet::new();
    let mut entry = None;
    for ph in elf.program_iter() {
        if ph.get_type() != Ok(Type::Load) {
            continue;
        }
        let virt_addr = ph.virtual_addr() as usize;
        let offset = ph.offset() as usize;
        let file_size = ph.file_size() as usize;
        let mem_size = ph.mem_size() as usize;

        #[cfg(target_arch = "aarch64")]
        assert_eq!((virt_addr >> 48), 0xffff, "Segment Fault");

        // Get target slice
        #[cfg(feature = "no_mmu")]
        let target = ms.push(mem_size);
        #[cfg(not(feature = "no_mmu"))]
        let target = {
            ms.push(virt_addr, virt_addr + mem_size, handler::ByFrame::new(memory_attr_from(ph.flags()), GlobalFrameAlloc), "");
            unsafe { ::core::slice::from_raw_parts_mut(virt_addr as *mut u8, mem_size) }
        };
        // Copy data
        unsafe {
            ms.with(|| {
                if file_size != 0 {
                    target[..file_size].copy_from_slice(&elf.input[offset..offset + file_size]);
                }
                target[file_size..].iter_mut().for_each(|x| *x = 0);
            });
        }
        // Find real entry point
        if ph.flags().is_execute() {
            let origin_entry = elf.header.pt2.entry_point() as usize;
            entry = Some(origin_entry - virt_addr + target.as_ptr() as usize);
        }
    }
    (ms, entry.unwrap())
}

fn memory_attr_from(elf_flags: Flags) -> MemoryAttr {
    let mut flags = MemoryAttr::default().user();
    // TODO: handle readonly
    if elf_flags.is_execute() { flags = flags.execute(); }
    flags
}