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

use crate::{processor::memory::Memory, util::pause};
use connect::{AudioOutput, EmulatorMessage, Renderer, RomFile};
use once_cell::sync::OnceCell;
use processor::{memory::Rom, Cpu};
use std::{
    fs::{self},
    io::{stdout, Write},
    path::PathBuf,
    process::exit,
    str::FromStr,
    sync::mpsc::Receiver,
};
use util::pause_then_step;

pub mod connect;
mod constants;
mod processor;
pub mod util;

pub struct Options {
    pub rom: RomFile,
    pub save_path: Option<String>,
    pub no_save: bool,
    pub bootrom_path: Option<String>,
    pub connect_serial: bool,
    pub verbose: bool,
    pub cycle_count: bool,
}

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

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

pub const WIDTH: usize = 160;
pub const HEIGHT: usize = 144;

pub struct EmulatorCore {
    receiver: Receiver<EmulatorMessage>,
    cpu: Cpu,
    cycle_num: usize,
    cycle_count: bool,
}

impl EmulatorCore {
    pub fn init(
        receiver: Receiver<EmulatorMessage>,
        options: Options,
        mut window: Box<dyn Renderer>,
        output: AudioOutput,
        tile_window: Option<Box<dyn Renderer>>,
    ) -> Self {
        VERBOSE.set(options.verbose).unwrap();

        let rom = match options.rom {
            RomFile::Path(path) => {
                let maybe_save = if options.no_save {
                    None
                } else {
                    Some(if let Some(path) = options.save_path {
                        PathBuf::from_str(&path).unwrap()
                    } else {
                        PathBuf::from_str(&path).unwrap().with_extension("sav")
                    })
                };

                match fs::read(path) {
                    Ok(data) => Rom::load(data, maybe_save),
                    Err(e) => {
                        println!("Error reading ROM: {e}");
                        exit(1);
                    }
                }
            }
            RomFile::Raw(data) => Rom::load(data, None),
        };

        window.prepare(WIDTH, HEIGHT);
        window.set_title(format!("{} on {}", rom.get_title(), rom.mbc_type()));

        let bootrom_enabled = options.bootrom_path.is_some();
        let bootrom: Option<Vec<u8>> = if let Some(path) = options.bootrom_path {
            match fs::read(path) {
                Ok(data) => Some(data),
                Err(e) => {
                    println!("Error reading bootROM: {e}");
                    exit(1);
                }
            }
        } else {
            None
        };

        Self::new(
            receiver,
            Cpu::new(
                Memory::init(
                    bootrom,
                    rom,
                    window,
                    output,
                    options.connect_serial,
                    tile_window,
                ),
                bootrom_enabled,
            ),
            options.cycle_count,
        )
    }

    fn new(receiver: Receiver<EmulatorMessage>, cpu: Cpu, cycle_count: bool) -> Self {
        Self {
            receiver,
            cpu,
            cycle_num: 0,
            cycle_count,
        }
    }

    pub fn run(&mut self) {
        self.process_messages();
        self.cycle_num += 1;
        if self.cycle_count {
            self.print_cycles();
        }
        self.run_cycle();
    }

    pub fn run_stepped(&mut self, step_size: usize) {
        loop {
            self.process_messages();
            for _ in 0..step_size {
                self.cycle_num += 1;
                if self.cycle_count {
                    self.print_cycles();
                }
                self.run_cycle();
            }
            print!(
                "                       ...{} cycles - press enter to continue\r",
                self.cycle_num
            );
            stdout().flush().unwrap();
            pause();
        }
    }

    pub fn run_until_buffer_full(&mut self) {
        while !self.cpu.memory.is_audio_buffer_full() {
            self.run();
        }
    }

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

    fn process_messages(&mut self) {
        while let Ok(msg) = self.receiver.try_recv() {
            match msg {
                EmulatorMessage::Stop => {
                    self.cpu.memory.flush_rom();
                    exit(0);
                }
            }
        }
    }

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