extern crate ferretro_components;
extern crate sdl2;

use std::ffi::CStr;
use std::path::PathBuf;
use std::pin::Pin;

use sdl2::render::{WindowCanvas, BlendMode};
use sdl2::image::ImageRWops;
use sdl2::surface::Surface;
use sdl2::pixels::{Color, PixelFormatEnum};
use sdl2::rect::Rect;

use rand::{SeedableRng, Rng};
use rand_xoshiro::Xoshiro128Plus;

use structopt::StructOpt;

use ferretro_components::base::ControlFlow;
use ferretro_components::prelude::*;
use ferretro_components::provided::{
    sdl2::{Sdl2SurfaceComponent, SimpleSdl2AudioComponent},
    stdlib::{SleepFramerateLimitComponent, PathBufComponent},
};

type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;

#[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>,
}

struct Zretro {
    emu: Pin<Box<RetroComponentBase>>,
    canvas: WindowCanvas,
    font: Surface<'static>,
    rng: Xoshiro128Plus,
    ui_bg: Option<Surface<'static>>,
    snowflakes: Vec<Rect>,
    sdl2surf_comp_id: RetroComponentId,
}

const FONT_PNG: &'static [u8] = include_bytes!("lifont.png");

impl Zretro {
    fn new(opt: Opt) -> Result<Self> {
        let mut emu = RetroComponentBase::new(&opt.core);

        let geometry = emu.libretro_core().get_system_av_info().geometry;
        let sys_info = emu.libretro_core().get_system_info();
        let title = format!(
            "zretro - {}",
            unsafe { CStr::from_ptr(sys_info.library_name) }.to_string_lossy()
        );

        let mut sdl_context = sdl2::init()?;

        let window = sdl_context
            .video()?
            .window(title.as_str(), geometry.base_width, geometry.base_height)
            .borderless()
            .build()?;
        let canvas = window.into_canvas().build()?;

        let sdl2surf_comp = Sdl2SurfaceComponent::new(emu.libretro_core())?;
        let sdl2surf_comp_id = emu.register_component(sdl2surf_comp)?;

        let sdl2_audio = SimpleSdl2AudioComponent::new(&mut sdl_context, emu.libretro_core());
        emu.register_component(sdl2_audio)?;

        let sleep_fps = SleepFramerateLimitComponent::new(emu.libretro_core());
        emu.register_component(sleep_fps)?;

        emu.register_component(PathBufComponent {
            sys_path: opt.system.clone(),
            libretro_path: Some(opt.core.to_path_buf()),
            core_assets_path: None,
            save_path: Some(std::env::temp_dir()),
        })?;

        emu.init().unwrap();
        emu.load_game(&opt.rom).unwrap();

        let rwops = sdl2::rwops::RWops::from_bytes(FONT_PNG)?;
        let font_shortlived = rwops.load_png()?;
        // there's a nonsemantic inheritance of lifetime from ImageRWops::load_png. TODO: pr
        let font = unsafe {
            let ptr = font_shortlived.raw();
            std::mem::forget(font_shortlived);
            Surface::from_ll(ptr)
        };

        let mut rng = rand_xoshiro::Xoshiro128Plus::from_entropy();
        let mut ui_bg = Surface::new(geometry.base_width, geometry.base_height, PixelFormatEnum::ABGR8888)?;
        ui_bg.fill_rect(None, Color::RGBA(0, 0, 128, 128))?;
        let snowflakes = (0..100).into_iter()
            .map(|_| Rect::new(
                rng.gen_range(0..ui_bg.width() as i32),
                rng.gen_range(0..ui_bg.height() as i32),
                2, 2))
            .collect();

        Ok(Zretro {
            emu,
            canvas,
            font,
            rng,
            ui_bg: Some(ui_bg),
            snowflakes,
            sdl2surf_comp_id,
        })
    }

    fn update_snow(&mut self) -> Result<()> {
        let mut ui_bg = self.ui_bg.take().ok_or("no ui_bg?")?;
        ui_bg.fill_rect(None, Color::RGBA(0, 0, 128, 128))?;
        let w = ui_bg.width() as i32;
        let h = ui_bg.height() as i32;
        for flake in &mut self.snowflakes {
            let x = flake.x() + self.rng.gen_range(-1..=1);
            let y = flake.y() + 1;
            flake.set_x(x % w);
            flake.set_y(y % h);
        }
        let mut ui_canvas = ui_bg.into_canvas()?;
        ui_canvas.set_draw_color(Color::RGBA(255, 255, 255, 160));
        ui_canvas.draw_rects(&self.snowflakes[..])?;
        self.ui_bg = Some(ui_canvas.into_surface());
        Ok(())
    }

    fn run(&mut self) -> Result<()> {
        let tc = self.canvas.texture_creator();
        let font_tx = tc.create_texture_from_surface(&self.font)?;
        let mut font_rect = self.font.rect();
        font_rect.set_height(64);
        while let ControlFlow::Continue = self.emu.run() {
            self.update_snow()?;
            let ref_mut = self.emu.component_mut::<Sdl2SurfaceComponent>(self.sdl2surf_comp_id)?;
            let surface = ref_mut.surface();

            let emu_tx = tc.create_texture_from_surface(surface)?;

            let ui_bg_surf_ref = self.ui_bg.as_ref().ok_or("no bg?")?;
            let mut ui_tx = tc.create_texture_from_surface(ui_bg_surf_ref)?;
            ui_tx.set_blend_mode(BlendMode::Blend);

            self.canvas.clear();
            self.canvas.copy(&emu_tx, None, None)?;
            self.canvas.copy(&ui_tx, None, None)?;
            self.canvas.copy(&font_tx, font_rect, font_rect)?;
            self.canvas.present();
        }
        Ok(())
    }
}

fn main() -> Result<()> {
    let opt: Opt = Opt::from_args();
    let mut frontend = Zretro::new(opt)?;
    frontend.run()?;
    Ok(())
}