#![feature(exclusive_range_pattern, let_chains, slice_flatten, async_closure)]

mod processor;
mod util;

use clap::{ArgGroup, Parser};
use gilrs::Gilrs;
use minifb::{Window, WindowOptions};
use once_cell::sync::OnceCell;
use processor::{
    memory::{Memory, Rom},
    Cpu,
};
use std::{
    fs,
    io::{self, stdout, Write},
};

use crate::processor::gpu;

#[macro_export]
macro_rules! verbose_println {
    ($($tts:tt)*) => {
            if $crate::is_verbose() {
                    println!($($tts)*);
            }
    };
}

#[macro_export]
macro_rules! verbose_print {
    ($($tts:tt)*) => {
            if $crate::is_verbose() {
                    print!($($tts)*);
            }
    };
}

/// Gameboy (DMG-A/B/C) emulator
#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
#[command(group(ArgGroup::new("prints").args(["verbose","cycle_count"])))]
struct Args {
    /// ROM path
    #[arg(short, long)]
    rom: String,

    /// BootROM path
    #[arg(short, long)]
    bootrom: String,

    /// Just run BootROM
    #[arg(long)]
    run_bootrom: bool,

    /// Verbose print
    #[arg(short, long)]
    verbose: bool,

    /// Show cycle count
    #[arg(short, long)]
    cycle_count: bool,

    /// Show tile window
    #[arg(short, long)]
    tile_window: bool,

    /// Step emulation by...
    #[arg(long)]
    step_by: Option<usize>,

    /// Step emulation by...
    #[arg(short, long)]
    scale_factor: Option<usize>,
}

static mut PAUSE_ENABLED: bool = false;
static mut PAUSE_QUEUED: bool = false;

static VERBOSE: OnceCell<bool> = OnceCell::new();

const WIDTH: usize = 160;
const HEIGHT: usize = 144;
static FACTOR: OnceCell<usize> = OnceCell::new();

fn main() {
    let args = Args::parse();

    VERBOSE.set(args.verbose).unwrap();

    FACTOR
        .set(if let Some(factor) = args.scale_factor {
            factor
        } else {
            3
        })
        .unwrap();
    gpu::init_statics();

    let rom: Rom = match fs::read(args.rom) {
        Ok(data) => Rom::load(data),
        Err(e) => {
            println!("Error reading ROM: {e}");
            return;
        }
    };
    let bootrom: Vec<u8> = match fs::read(args.bootrom) {
        Ok(data) => data,
        Err(e) => {
            println!("Error reading bootROM: {e}");
            return;
        }
    };

    let mut window = Window::new(
        format!("{} on {}", rom.get_title(), rom.mbc_type()).as_str(),
        WIDTH * FACTOR.get().unwrap(),
        HEIGHT * FACTOR.get().unwrap(),
        WindowOptions::default(),
    )
    .unwrap_or_else(|e| {
        panic!("{e}");
    });

    window.set_position(500, 50);

    window.topmost(true);

    let mut cpu = Cpu::new(
        Memory::init(bootrom, args.run_bootrom, rom),
        window,
        args.tile_window,
        args.run_bootrom,
        Gilrs::new().unwrap(),
    );

    let mut cycle_num = 0;

    verbose_println!("\n\n    Begin execution...\n");
    match args.step_by {
        Some(step_size) => loop {
            for _ in 0..step_size {
                cycle_num += 1;
                if args.cycle_count {
                    print_cycles(&cycle_num);
                }
                run_cycle(&mut cpu);
            }
            print!("                       ...{cycle_num} cycles - press enter to continue\r");
            stdout().flush().unwrap();
            pause();
        },
        None => loop {
            cycle_num += 1;
            if args.cycle_count {
                print_cycles(&cycle_num);
            }
            run_cycle(&mut cpu);
        },
    }
}

fn run_cycle(cpu: &mut Cpu) {
    let will_pause = unsafe { PAUSE_QUEUED };
    let pause_enabled = unsafe { PAUSE_ENABLED };
    cpu.exec_next();
    if !pause_enabled && cpu.reg.pc >= 0x100 {
        unsafe { PAUSE_ENABLED = true };
    }
    if will_pause {
        pause_then_step();
    }
}

fn pause_then_step() {
    unsafe {
        if PAUSE_ENABLED {
            let line = pause();
            PAUSE_QUEUED = !line.contains("continue");
        }
    }
}

#[allow(dead_code)]
fn pause_once() {
    println!("paused...");
    pause();
}

fn pause() -> String {
    let mut line = String::new();
    match io::stdin().read_line(&mut line) {
        Ok(_) => line,
        Err(_) => String::from(""),
    }
}

fn print_cycles(cycles: &i32) {
    if *cycles % 45678 != 0 {
        return;
    }
    let instructions_per_second = 400000;
    print!(
        "cycle {} - approx {} seconds on real hardware\r",
        cycles,
        cycles / instructions_per_second
    );
    stdout().flush().unwrap();
}

fn is_verbose() -> bool {
    match VERBOSE.get() {
        Some(v) => *v,
        None => false,
    }
}