#![feature(panic_implementation)] // required for defining the panic handler
#![feature(abi_x86_interrupt)]
#![no_std] // don't link the Rust standard library
#![cfg_attr(not(test), no_main)] // disable all Rust-level entry points
#![cfg_attr(test, allow(dead_code, unused_macros, unused_imports))]

#[macro_use]
extern crate blog_os;
extern crate x86_64;
#[macro_use]
extern crate lazy_static;

use blog_os::interrupts::{self, PICS};
use core::panic::PanicInfo;

/// This function is the entry point, since the linker looks for a function
/// named `_start` by default.
#[cfg(not(test))]
#[no_mangle] // don't mangle the name of this function
pub extern "C" fn _start() -> ! {
    println!("Hello World{}", "!");

    blog_os::gdt::init();
    init_idt();
    unsafe { PICS.lock().initialize() };
    x86_64::instructions::interrupts::enable();

    println!("It did not crash!");
    blog_os::hlt_loop();
}

/// This function is called on panic.
#[cfg(not(test))]
#[panic_implementation]
#[no_mangle]
pub fn panic(info: &PanicInfo) -> ! {
    println!("{}", info);
    blog_os::hlt_loop();
}

use x86_64::structures::idt::{ExceptionStackFrame, InterruptDescriptorTable};

lazy_static! {
    static ref IDT: InterruptDescriptorTable = {
        let mut idt = InterruptDescriptorTable::new();
        idt.breakpoint.set_handler_fn(breakpoint_handler);
        unsafe {
            idt.double_fault
                .set_handler_fn(double_fault_handler)
                .set_stack_index(blog_os::gdt::DOUBLE_FAULT_IST_INDEX);
        }

        let timer_interrupt_id = usize::from(interrupts::TIMER_INTERRUPT_ID);
        idt[timer_interrupt_id].set_handler_fn(timer_interrupt_handler);
        let keyboard_interrupt_id = usize::from(interrupts::KEYBOARD_INTERRUPT_ID);
        idt[keyboard_interrupt_id].set_handler_fn(keyboard_interrupt_handler);

        idt
    };
}

pub fn init_idt() {
    IDT.load();
}

extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut ExceptionStackFrame) {
    println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
}

extern "x86-interrupt" fn double_fault_handler(
    stack_frame: &mut ExceptionStackFrame,
    _error_code: u64,
) {
    println!("EXCEPTION: DOUBLE FAULT\n{:#?}", stack_frame);
    loop {}
}

extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut ExceptionStackFrame) {
    print!(".");
    unsafe {
        PICS.lock()
            .notify_end_of_interrupt(interrupts::TIMER_INTERRUPT_ID)
    }
}

extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut ExceptionStackFrame) {
    use x86_64::instructions::port::Port;

    let port = Port::new(0x60);
    let scancode: u8 = unsafe { port.read() };

    let key = match scancode {
        0x02 => Some('1'),
        0x03 => Some('2'),
        0x04 => Some('3'),
        0x05 => Some('4'),
        0x06 => Some('5'),
        0x07 => Some('6'),
        0x08 => Some('7'),
        0x09 => Some('8'),
        0x0a => Some('9'),
        0x0b => Some('0'),
        _ => None,
    };
    if let Some(key) = key {
        print!("{}", key);
    }
    unsafe {
        PICS.lock()
            .notify_end_of_interrupt(interrupts::KEYBOARD_INTERRUPT_ID)
    }
}