extern crate crossbeam_channel;
extern crate ferretro;
extern crate sdl2;

use ferretro::retro;
use ferretro::retro::ffi::{GameGeometry, SystemInfo, SystemAvInfo};
use ferretro::retro::constants::{InputIndex, JoypadButton, AnalogAxis, DeviceType};
use ferretro::retro::wrapped_types::{ControllerDescription2, InputDescriptor2, InputDeviceId, SubsystemInfo2, Variable2};
use ferretro::retro::wrapper::LibretroWrapper;

use std::ffi::CStr;
use std::io::Read;
use std::path::{Path, PathBuf};
use std::pin::Pin;
use std::time::{Duration, Instant};

use structopt::StructOpt;

use sdl2::audio::{AudioCallback, AudioFormat, AudioSpec, AudioSpecDesired, AudioDevice};
use sdl2::controller::{GameController, Button, Axis};
use sdl2::event::Event;
use sdl2::keyboard::Keycode;
use sdl2::rect::Rect;
use sdl2::render::WindowCanvas;

struct MyEmulator {
    retro: retro::wrapper::LibretroWrapper,
    core_path: PathBuf,
    sys_path: Option<PathBuf>,

    preferred_pad: Option<u32>,

    sys_info: SystemInfo,
    av_info: SystemAvInfo,

    sdl_context: sdl2::Sdl,

    // video bits
    canvas: WindowCanvas,
    pixel_format: sdl2::pixels::PixelFormatEnum,

    // audio bits
    audio_buffer: Vec<i16>,
    audio_spec: AudioSpec,
    audio_device: AudioDevice<MySdlAudio>,
    audio_sender: crossbeam_channel::Sender<Vec<i16>>,

    // input bits
    gamepad_subsys: sdl2::GameControllerSubsystem,
    gamepads: Vec<GameController>,
}

impl MyEmulator {
    pub fn new(core_path: impl AsRef<Path>, sys_path: &Option<impl AsRef<Path>>) -> Pin<Box<Self>> {
        let core_path = PathBuf::from(core_path.as_ref());
        let lib = libloading::Library::new(&core_path).unwrap();
        let raw_retro = retro::loading::LibretroApi::from_library(lib).unwrap();
        let retro = retro::wrapper::LibretroWrapper::from(raw_retro);

        let sys_info = retro.get_system_info();
        let title = format!(
            "{} - rust libretro",
            unsafe { CStr::from_ptr(sys_info.library_name) }.to_string_lossy()
        );

        let mut av_info = retro.get_system_av_info();
        let pixel_format = sdl2::pixels::PixelFormatEnum::ARGB1555;

        // HACK: some cores don't report this 'til we get an environ call to set_system_av_info...
        //  which is too late for this constructor to pass along to SDL.
        if av_info.timing.sample_rate == 0.0 {
            av_info.timing.sample_rate = 32040.0;
        }

        let sdl_context = sdl2::init().unwrap();

        let window = sdl_context
            .video()
            .unwrap()
            .window(title.as_str(), av_info.geometry.base_width, av_info.geometry.base_height)
            .opengl()
            .build()
            .unwrap();

        let canvas = window.into_canvas().build().unwrap();

        let (audio_sender, audio_receiver) = crossbeam_channel::bounded(2);

        let audio = sdl_context.audio().unwrap();
        let desired_spec = AudioSpecDesired {
            freq: Some(av_info.timing.sample_rate.round() as i32),
            channels: Some(2),
            samples: None,
        };
        let mut audio_spec = None;
        let audio_device = audio
            .open_playback(None, &desired_spec, |spec| {
                if spec.format != AudioFormat::S16LSB {
                    println!("unsupported audio format {:?}", spec.format);
                }
                audio_spec = Some(spec.clone());
                MySdlAudio {
                    audio_spec: spec,
                    audio_receiver,
                }
            })
            .unwrap();

        let gamepad_subsys = sdl_context.game_controller().unwrap();
        let mut gamepads = Vec::new();
        for i in 0..gamepad_subsys.num_joysticks().unwrap() {
            gamepads.extend(gamepad_subsys.open(i).into_iter());
        }

        let emu = MyEmulator {
            retro,
            core_path,
            sys_path: sys_path.as_ref().map(|p| p.as_ref().to_path_buf()),
            preferred_pad: None,
            av_info,
            sys_info,
            sdl_context,
            canvas,
            pixel_format,
            audio_buffer: Default::default(),
            audio_spec: audio_spec.unwrap(),
            audio_device,
            audio_sender,
            gamepad_subsys,
            gamepads,
        };
        let mut pin_emu = Box::pin(emu);
        retro::wrapper::set_handler(pin_emu.as_mut());
        pin_emu.retro.init();
        pin_emu
    }

    pub fn run(&mut self) {
        self.audio_device.resume();
        let mut event_pump = self.sdl_context.event_pump().unwrap();
        'running: loop {
            let frame_begin = Instant::now();

            for event in event_pump.poll_iter() {
                match event {
                    Event::Quit { .. }
                    | Event::KeyDown {
                        keycode: Some(Keycode::Escape),
                        ..
                    } => break 'running,
                    _ => {}
                }
            }

            // The rest of the game loop goes here...
            self.retro.run();
            self.canvas.present();

            // similar hack to the sample rate, make sure we don't divide by zero.
            let mut spf = 1.0 / self.av_info.timing.fps;
            if spf.is_nan() || spf.is_infinite() {
                spf = 1.0 / 60.0;
            }
            Duration::from_secs_f64(spf)
                .checked_sub(frame_begin.elapsed())
                .map(std::thread::sleep);
        }
    }

    pub fn load_game(&self, rom: impl AsRef<Path>) {
        let path = rom.as_ref();
        let mut data = None;
        let mut v = Vec::new();
        if !self.sys_info.need_fullpath {
            if let Ok(mut f) = std::fs::File::open(path) {
                if f.read_to_end(&mut v).is_ok() {
                    data = Some(v.as_ref());
                }
            }
        }
        self.retro
            .load_game(Some(path), data, None)
            .unwrap();
        if let Some(device) = self.preferred_pad {
            for port in 0..self.gamepads.len() as u32 {
                self.retro.set_controller_port_device(port, device);
            }
        }
    }

    fn send_audio_samples(&mut self) {
        let stereo_samples = self.audio_spec.samples as usize * 2;
        while self.audio_buffer.len() >= stereo_samples {
            let remainder = self.audio_buffer.split_off(stereo_samples);
            let msg = std::mem::replace(&mut self.audio_buffer, remainder);
            let _ = self.audio_sender.try_send(msg);
        }
    }
}

impl Drop for MyEmulator {
    fn drop(&mut self) {
        retro::wrapper::unset_handler();
    }
}

impl retro::wrapper::Handler for MyEmulator {
    fn libretro_core(&mut self) -> &mut LibretroWrapper {
        &mut self.retro
    }

    fn video_refresh(&mut self, data: &[u8], width: u32, height: u32, pitch: u32) {
        let rect = Rect::new(0, 0, width, height);

        if let Ok(mut tex) =
            self.canvas
                .texture_creator()
                .create_texture_static(self.pixel_format, width, height)
        {
            if tex.update(rect, data, pitch as usize).is_ok() {
                self.canvas.clear();
                self.canvas.copy(&tex, None, None).unwrap();
            }
        }
    }

    fn audio_sample(&mut self, left: i16, right: i16) {
        self.audio_buffer.push(left);
        self.audio_buffer.push(right);
        self.send_audio_samples()
    }

    fn audio_sample_batch(&mut self, stereo_pcm: &[i16]) -> usize {
        self.audio_buffer.extend(stereo_pcm);
        self.send_audio_samples();
        stereo_pcm.len()
    }

    fn input_poll(&mut self) {
        self.gamepad_subsys.update();
    }

    fn input_state(&mut self, port: u32, device: InputDeviceId, index: InputIndex) -> i16 {
        match self.gamepads.get(port as usize) {
            Some(gamepad) => {
                match device {
                    InputDeviceId::Joypad(button) => {
                        match button_map(&button) {
                            Some(x) => gamepad.button(x) as i16,
                            None => match button {
                                JoypadButton::L2 => gamepad.axis(Axis::TriggerLeft),
                                JoypadButton::R2 => gamepad.axis(Axis::TriggerRight),
                                _ => 0,
                            }
                        }
                    }
                    InputDeviceId::Analog(axis) => gamepad.axis(axis_map(index, axis)),
                    _ => 0,
                }
            }
            None => 0,
        }
    }

    fn get_can_dupe(&mut self) -> Option<bool> { Some(true) }

    fn get_system_directory(&mut self) -> Option<PathBuf> {
        self.sys_path.clone()
    }

    fn set_pixel_format(&mut self, pix_fmt: retro::ffi::PixelFormat) -> bool {
        self.pixel_format = match pix_fmt {
            retro::ffi::PixelFormat::ARGB1555 => sdl2::pixels::PixelFormatEnum::RGB555,
            retro::ffi::PixelFormat::ARGB8888 => sdl2::pixels::PixelFormatEnum::ARGB8888,
            retro::ffi::PixelFormat::RGB565 => sdl2::pixels::PixelFormatEnum::RGB565,
        };
        true
    }
    fn get_variable(&mut self, key: &str) -> Option<String> {
        match key {
            "beetle_saturn_analog_stick_deadzone" => Some("15%".to_string()),
            "parallel-n64-gfxplugin" => Some("angrylion".to_string()),
            "parallel-n64-astick-deadzone" => Some("15%".to_string()),
            _ => None,
        }
    }

    fn set_variables(&mut self, variables: Vec<Variable2>) -> bool {
        for v in variables {
            eprintln!("{:?}", v);
        }
        true
    }

    fn get_libretro_path(&mut self) -> Option<PathBuf> {
        Some(self.core_path.clone())
    }

    fn get_input_device_capabilities(&mut self) -> Option<u64> {
        let bits = (1 << (DeviceType::Joypad as u32)) | (1 << (DeviceType::Analog as u32));
        Some(bits as u64)
    }

    fn get_save_directory(&mut self) -> Option<PathBuf> {
        Some(std::env::temp_dir())
    }

    fn set_system_av_info(&mut self, av_info: SystemAvInfo) -> bool {
        self.set_geometry(av_info.geometry.clone());
        self.av_info = av_info;
        true
    }

    fn set_subsystem_info(&mut self, subsystem_info: Vec<SubsystemInfo2>) -> bool {
        println!("subsystem info: {:?}", subsystem_info);
        true
    }

    fn set_controller_info(&mut self, controller_info: Vec<ControllerDescription2>) -> bool {
        for ci in controller_info {
            // so we can have analog support in beetle/mednafen saturn
            if ci.name.as_str() == "3D Control Pad" {
                self.preferred_pad = Some(ci.device_id());
                break;
            }
        }
        true
    }

    fn set_input_descriptors(&mut self, descriptors: Vec<InputDescriptor2>) -> bool {
        for id in descriptors {
            println!("{:?}", id);
        }
        true
    }

    fn set_geometry(&mut self, geom: GameGeometry) -> bool {
        let _ = self.canvas.window_mut().set_size(geom.base_width, geom.base_height);
        let _ = self.canvas.set_logical_size(geom.base_width, geom.base_height);
        self.av_info.geometry = geom;
        true
    }

    fn log_print(&mut self, level: retro::ffi::LogLevel, msg: &str) {
        eprint!("[{:?}] {}", level, msg);
    }
}

struct MySdlAudio {
    audio_spec: AudioSpec,
    audio_receiver: crossbeam_channel::Receiver<Vec<i16>>,
}

impl AudioCallback for MySdlAudio {
    type Channel = i16;

    fn callback(&mut self, out: &mut [Self::Channel]) {
        if self.audio_spec.format == AudioFormat::S16LSB {
            if let Ok(samples) = self.audio_receiver.recv() {
                out.copy_from_slice(&samples[..out.len()]);
            }
        }
    }
}

pub fn main() -> failure::Fallible<()> {
    let opt: Opt = Opt::from_args();
    let mut emu = MyEmulator::new(&opt.core, &opt.system);
    emu.load_game(&opt.rom);
    emu.run();

    Ok(())
}

#[derive(StructOpt)]
struct Opt {
    /// Core module to use.
    #[structopt(short, long, parse(from_os_str))]
    core: PathBuf,
    /// ROM to load using the core.
    #[structopt(short, long, parse(from_os_str))]
    rom: PathBuf,
    /// System directory, often containing BIOS files
    #[structopt(short, long, parse(from_os_str))]
    system: Option<PathBuf>,
}

fn button_map(retro_button: &JoypadButton) -> Option<Button> {
    match retro_button {
        JoypadButton::B => Some(Button::A),
        JoypadButton::Y => Some(Button::X),
        JoypadButton::Select => Some(Button::Back),
        JoypadButton::Start => Some(Button::Start),
        JoypadButton::Up => Some(Button::DPadUp),
        JoypadButton::Down => Some(Button::DPadDown),
        JoypadButton::Left => Some(Button::DPadLeft),
        JoypadButton::Right => Some(Button::DPadRight),
        JoypadButton::A => Some(Button::B),
        JoypadButton::X => Some(Button::Y),
        JoypadButton::L => Some(Button::LeftShoulder),
        JoypadButton::R => Some(Button::RightShoulder),
         // SDL2 controller API doesn't have L2/R2 as buttons, they're considered axes
        JoypadButton::L2 => None,
        JoypadButton::R2 => None,
        JoypadButton::L3 => Some(Button::LeftStick),
        JoypadButton::R3 => Some(Button::RightStick),
    }
}

fn axis_map(index: InputIndex, axis: AnalogAxis) -> Axis {
    match (index, axis) {
        (InputIndex::Left, AnalogAxis::X) => Axis::LeftX,
        (InputIndex::Left, AnalogAxis::Y) => Axis::LeftY,
        (InputIndex::Right, AnalogAxis::X) => Axis::RightX,
        (InputIndex::Right, AnalogAxis::Y) => Axis::RightY,
    }
}