// Copyright 2016 Philipp Oppermann. See the README.md
// file at the top-level directory of this distribution.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

pub use self::area_frame_allocator::AreaFrameAllocator;
pub use self::paging::remap_the_kernel;
use self::paging::PhysicalAddress;
use multiboot2::BootInformation;

mod area_frame_allocator;
mod paging;

pub const PAGE_SIZE: usize = 4096;

pub fn init(boot_info: &BootInformation) {
    assert_has_not_been_called!("memory::init must be called only once");

    let memory_map_tag = boot_info.memory_map_tag().expect("Memory map tag required");
    let elf_sections_tag = boot_info.elf_sections_tag().expect("Elf sections tag required");

    let kernel_start = elf_sections_tag.sections()
                                       .filter(|s| s.is_allocated())
                                       .map(|s| s.addr)
                                       .min()
                                       .unwrap();
    let kernel_end = elf_sections_tag.sections()
                                     .filter(|s| s.is_allocated())
                                     .map(|s| s.addr + s.size)
                                     .max()
                                     .unwrap();

    println!("kernel start: {:#x}, kernel end: {:#x}",
             kernel_start,
             kernel_end);
    println!("multiboot start: {:#x}, multiboot end: {:#x}",
             boot_info.start_address(),
             boot_info.end_address());

    let mut frame_allocator = AreaFrameAllocator::new(kernel_start as usize,
                                                      kernel_end as usize,
                                                      boot_info.start_address(),
                                                      boot_info.end_address(),
                                                      memory_map_tag.memory_areas());

    let mut active_table = paging::remap_the_kernel(&mut frame_allocator, boot_info);

    use self::paging::Page;
    use hole_list_allocator::{HEAP_START, HEAP_SIZE};

    let heap_start_page = Page::containing_address(HEAP_START);
    let heap_end_page = Page::containing_address(HEAP_START + HEAP_SIZE - 1);

    for page in Page::range_inclusive(heap_start_page, heap_end_page) {
        active_table.map(page, paging::WRITABLE, &mut frame_allocator);
    }
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Frame {
    number: usize,
}

impl Frame {
    fn containing_address(address: usize) -> Frame {
        Frame { number: address / PAGE_SIZE }
    }

    fn start_address(&self) -> PhysicalAddress {
        self.number * PAGE_SIZE
    }

    fn clone(&self) -> Frame {
        Frame { number: self.number }
    }

    fn range_inclusive(start: Frame, end: Frame) -> FrameIter {
        FrameIter {
            start: start,
            end: end,
        }
    }
}

struct FrameIter {
    start: Frame,
    end: Frame,
}

impl Iterator for FrameIter {
    type Item = Frame;

    fn next(&mut self) -> Option<Frame> {
        if self.start <= self.end {
            let frame = self.start.clone();
            self.start.number += 1;
            Some(frame)
        } else {
            None
        }
    }
}

pub trait FrameAllocator {
    fn allocate_frame(&mut self) -> Option<Frame>;
    fn deallocate_frame(&mut self, frame: Frame);
}