extern crate ferretro_components;
extern crate sdl2;

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

use sdl2::{
    EventPump,
    event::{Event, WindowEvent},
    keyboard::Keycode,
    mouse::{Cursor, MouseUtil},
    pixels::{Color, PixelFormatEnum},
    rect::{Point, Rect},
    render::{WindowCanvas, BlendMode},
    surface::Surface,
};

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

use structopt::StructOpt;
use itertools::Itertools;

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

use crate::gui::*;

pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;

mod gui;

#[derive(StructOpt)]
struct Opt {
    /// Core module to use. If not provided, falls back to statically-linked core.
    #[structopt(short, long, parse(from_os_str))]
    core: Option<PathBuf>,
    /// ROM to load using the core.
    #[structopt(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: SurfaceFont<'static>,
    mouse_util: MouseUtil,
    mouse_cursor: Cursor,
    mouse_shadow_surf: Surface<'static>,
    mouse_shadow_pos: Rect,
    rng: Xoshiro128Plus,
    ui_bg: Option<Surface<'static>>,
    snowflakes: Vec<Point>,
    mode: GuiState,
    event_pump: EventPump,
}

impl Zretro {
    fn new(opt: Opt) -> Result<Self> {
        let mut emu = match &opt.core {
            Some(core_path) => RetroComponentBase::new(core_path),
            None if cfg!(feature = "static") => RetroComponentBase::new_static(),
            _ => panic!("--core is required when frontend is not built with the 'static' feature."),
        };

        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()?;

        emu.register_component(Sdl2SurfaceComponent::new()?)?;

        emu.register_component(SimpleSdl2AudioComponent::new(&mut sdl_context)?)?;

        emu.register_component(SleepFramerateLimitComponent::default())?;

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

        emu.init().unwrap();
        emu.load_game(&opt.rom).unwrap(); // TODO: optional via CLI positional arg, menu-browsable

        let SystemAvInfo { geometry, .. } = emu.libretro_core().get_system_av_info();

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

        let event_pump = sdl_context.event_pump()?;

        let font = SurfaceFont::load_zfont()?;

        let mouse_surf = surface_asset(MOUSE_PNG)?;
        let mouse_shadow_surf = surface_asset(MOUSE_SHADOW_PNG)?;

        let mouse_util = sdl_context.mouse();
        let mouse_cursor = Cursor::from_surface(&mouse_surf, 0, 0)?;
        mouse_cursor.set();
        let mouse_shadow_pos = mouse_shadow_surf.rect();

        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(|_| Point::new(
                rng.gen_range(0..ui_bg.width() as i32),
                rng.gen_range(0..ui_bg.height() as i32),
            ))
            .collect();

        Ok(Zretro {
            emu,
            canvas,
            font,
            mouse_util,
            mouse_cursor,
            mouse_shadow_surf,
            mouse_shadow_pos,
            rng,
            ui_bg: Some(ui_bg),
            snowflakes,
            mode: GuiState::Menus,
            event_pump,
        })
    }

    fn update_snow(&mut self) -> Result<()> {
        let mut ui_bg = self.ui_bg.take().ok_or("no ui_bg?")?;
        let mut bg_color = BG_COLOR;
        bg_color.a = 128;
        ui_bg.fill_rect(None, bg_color)?;
        let w = ui_bg.width() as i32;
        let h = ui_bg.height() as i32;
        let halflen = self.snowflakes.len() / 2;
        for flake in &mut self.snowflakes[..halflen] {
            let x = flake.x() + self.rng.gen_range(0..=1);
            let y = flake.y() + 1;
            *flake = Point::new(x % w, y % h);
        }
        for flake in &mut self.snowflakes[halflen..] {
            let x = flake.x();
            let y = flake.y() + self.rng.gen_range(0..=1);
            *flake = Point::new(x, y % h);
        }
        let mut ui_canvas = ui_bg.into_canvas()?;
        ui_canvas.set_draw_color(Color::RGBA(255, 255, 255, 160));
        ui_canvas.draw_points(&self.snowflakes[..halflen])?;
        ui_canvas.set_draw_color(Color::RGBA(255, 255, 255, 128));
        ui_canvas.draw_points(&self.snowflakes[halflen..])?;
        self.ui_bg = Some(ui_canvas.into_surface());
        Ok(())
    }

    fn toggle_mode(&mut self) -> Result<()> {
        self.mode.toggle();
        match self.mode {
            GuiState::Menus => {
                self.mouse_cursor.set();
                self.mouse_util.show_cursor(true);
            }
            GuiState::Game => {
                self.mouse_util.show_cursor(false);
            }
        }
        Ok(())
    }

    fn run(&mut self) -> Result<()> {
        let tc = self.canvas.texture_creator();
        let font_tx = tc.create_texture_from_surface(&self.font.surf)?;
        let font_rect = self.font.surf.rect();
        'outer: loop {
            let events = self.event_pump.poll_iter().collect_vec();
            for event in events {
                match event {
                    Event::Quit { .. } => break 'outer,
                    Event::KeyDown { keycode: Some(keycode), .. } => {
                        match keycode {
                            Keycode::Escape => self.toggle_mode()?,
                            _ => {}
                        }
                    }
                    Event::KeyUp { .. } => {}
                    Event::DropFile { filename, .. } => {
                        self.emu.libretro_core().unload_game();
                        self.emu.load_game(filename)?;
                    }
                    Event::MouseMotion { x, y, xrel, yrel, .. } => {
                        self.mouse_shadow_pos.set_x(x + xrel + 5);
                        self.mouse_shadow_pos.set_y(y + yrel + 7);
                    },
                    Event::Window { win_event: WindowEvent::Leave, .. } => {
                        self.mouse_shadow_pos.set_x(-(self.mouse_shadow_surf.width() as i32));
                    }
                    _ => {}
                }
            }

            if let GuiState::Game = self.mode {
                if let ControlFlow::Break = self.emu.run() {
                    break;
                }
            } else {
                let delay: &mut SleepFramerateLimitComponent = self.emu.component_mut()?;
                delay.do_sleep();
            }

            let surfcomp: &Sdl2SurfaceComponent = self.emu.component_ref()?;
            let emu_surf_ref = surfcomp.surface();
            let emu_tx = tc.create_texture_from_surface(emu_surf_ref)?;
            self.canvas.clear();
            self.canvas.copy(&emu_tx, None, None)?;

            if let GuiState::Menus = self.mode {
                self.update_snow()?;
                let ui_bg_mut = self.ui_bg.as_mut().ok_or("no bg?")?;

                let _ = self.mouse_shadow_surf.blit(None, ui_bg_mut, self.mouse_shadow_pos);

                self.font.blit_text(
                    ui_bg_mut,
                    "Hello world\nfrom zfon't!! ^_^;",
                    Rect::new(144, 32, 100, 20)
                )?;
                let mut ui_tx = tc.create_texture_from_surface(ui_bg_mut)?;
                ui_tx.set_blend_mode(BlendMode::Blend);
                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(())
}