use std::{
    cell::RefCell,
    collections::HashMap,
    fs::File,
    io::Read,
    ops::Index,
    path::Path,
    rc::Rc,
    sync::{Arc, RwLock},
    time::{Duration, Instant},
};

use cairo::{Context, Rectangle};
use cyberpunk::{AsymLine, AsymLineCutout, GlowPen, Pen, Text};
use glib::{GString, Object};
use gtk::{
    glib::{self, Propagation},
    prelude::*,
    subclass::prelude::*,
    EventControllerKey,
};
use serde::{Deserialize, Serialize};

const FPS: u64 = 60;
const PURPLE: (f64, f64, f64) = (0.7, 0., 1.);

#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Hash)]
#[serde(rename_all = "lowercase")]
enum Position {
    Top,
    Middle,
    Bottom,
}

#[derive(Serialize, Deserialize, Debug, Clone)]
struct Step {
    text: String,
    position: Position,
    transition: Duration,
}

#[derive(Serialize, Deserialize, Debug, Clone)]
struct Script(Vec<Step>);

impl Script {
    fn from_file(path: &Path) -> Result<Script, serde_yml::Error> {
        let mut buf: Vec<u8> = Vec::new();
        let mut f = File::open(path).unwrap();
        f.read_to_end(&mut buf).unwrap();
        let script = serde_yml::from_slice(&buf)?;
        Ok(Self(script))
    }

    fn iter<'a>(&'a self) -> impl Iterator<Item = &'a Step> {
        self.0.iter()
    }

    fn len(&self) -> usize {
        self.0.len()
    }
}

impl Default for Script {
    fn default() -> Self {
        Self(vec![])
    }
}

impl Index<usize> for Script {
    type Output = Step;

    fn index(&self, index: usize) -> &Self::Output {
        &self.0[index]
    }
}

struct Fade {
    text: String,
    position: Position,
    duration: Duration,

    start_time: Instant,
}

trait Animation {
    fn position(&self) -> Position;

    fn tick(&self, now: Instant, context: &Context, width: f64);
}

impl Animation for Fade {
    fn position(&self) -> Position {
        self.position.clone()
    }

    fn tick(&self, now: Instant, context: &Context, width: f64) {
        let total_frames = self.duration.as_secs() * FPS;
        let alpha_rate: f64 = 1. / total_frames as f64;

        let frames = (now - self.start_time).as_secs_f64() * FPS as f64;
        let alpha = alpha_rate * frames as f64;

        let text_display = Text::new(self.text.clone(), context, 64., width);
        let _ = context.move_to(0., text_display.extents().height());
        let _ = context.set_source_rgba(PURPLE.0, PURPLE.1, PURPLE.2, alpha);
        text_display.draw();
    }
}

struct CrossFade {
    old_text: String,
    new_text: String,
    position: Position,
    duration: Duration,

    start_time: Instant,
}

impl Animation for CrossFade {
    fn position(&self) -> Position {
        self.position.clone()
    }

    fn tick(&self, now: Instant, context: &Context, width: f64) {
        let total_frames = self.duration.as_secs() * FPS;
        let alpha_rate: f64 = 1. / total_frames as f64;

        let frames = (now - self.start_time).as_secs_f64() * FPS as f64;
        let alpha = alpha_rate * frames as f64;

        let text_display = Text::new(self.old_text.clone(), context, 64., width);
        let _ = context.move_to(0., text_display.extents().height());
        let _ = context.set_source_rgba(PURPLE.0, PURPLE.1, PURPLE.2, 1. - alpha);
        text_display.draw();

        let text_display = Text::new(self.new_text.clone(), context, 64., width);
        let _ = context.move_to(0., text_display.extents().height());
        let _ = context.set_source_rgba(PURPLE.0, PURPLE.1, PURPLE.2, alpha);
        text_display.draw();
    }
}

#[derive(Debug)]
pub struct CyberScreenState {
    script: Script,
    idx: Option<usize>,
    top: Option<Step>,
    middle: Option<Step>,
    bottom: Option<Step>,
}

impl Default for CyberScreenState {
    fn default() -> Self {
        Self {
            script: Script(vec![]),
            idx: None,
            top: None,
            middle: None,
            bottom: None,
        }
    }
}

impl CyberScreenState {
    fn new(script: Script) -> CyberScreenState {
        let mut s = CyberScreenState::default();
        s.script = script;
        s
    }

    fn next_page(&mut self) -> Box<dyn Animation> {
        let idx = match self.idx {
            None => 0,
            Some(idx) => {
                if idx < self.script.len() {
                    idx + 1
                } else {
                    idx
                }
            }
        };
        self.idx = Some(idx);
        let step = self.script[idx].clone();

        let (old, new) = match step.position {
            Position::Top => {
                let old = self.top.replace(step.clone());
                (old, step)
            }
            Position::Middle => {
                let old = self.middle.replace(step.clone());
                (old, step)
            }
            Position::Bottom => {
                let old = self.bottom.replace(step.clone());
                (old, step)
            }
        };

        match old {
            Some(old) => Box::new(CrossFade {
                old_text: old.text.clone(),
                new_text: new.text.clone(),
                position: new.position,
                duration: new.transition,
                start_time: Instant::now(),
            }),
            None => Box::new(Fade {
                text: new.text.clone(),
                position: new.position,
                duration: new.transition,
                start_time: Instant::now(),
            }),
        }
    }
}

#[derive(Default)]
pub struct CyberScreenPrivate {
    state: Rc<RefCell<CyberScreenState>>,
    // For crossfading to work, I have to detect that there is an old animation in a position, and
    // replace it with the new one.
    animations: Rc<RefCell<HashMap<Position, Box<dyn Animation>>>>,
}

#[glib::object_subclass]
impl ObjectSubclass for CyberScreenPrivate {
    const NAME: &'static str = "CyberScreen";
    type Type = CyberScreen;
    type ParentType = gtk::DrawingArea;
}

impl ObjectImpl for CyberScreenPrivate {}
impl WidgetImpl for CyberScreenPrivate {}
impl DrawingAreaImpl for CyberScreenPrivate {}

impl CyberScreenPrivate {
    fn set_script(&self, script: Script) {
        *self.state.borrow_mut() = CyberScreenState::new(script);
    }

    fn next_page(&self) {
        let transition = self.state.borrow_mut().next_page();
        self.animations
            .borrow_mut()
            .insert(transition.position(), transition);
    }
}

glib::wrapper! {
    pub struct CyberScreen(ObjectSubclass<CyberScreenPrivate>) @extends gtk::DrawingArea, gtk::Widget;
}

impl CyberScreen {
    fn new(script: Script) -> Self {
        let s: Self = Object::builder().build();
        s.imp().set_script(script);

        s.set_draw_func({
            let s = s.clone();
            move |_, context, width, height| {
                let now = Instant::now();
                let _ = context.set_source_rgb(0., 0., 0.);
                let _ = context.paint();

                let pen = GlowPen::new(width, height, 2., 8., (0.7, 0., 1.));
                AsymLineCutout {
                    orientation: gtk::Orientation::Horizontal,
                    start_x: 25.,
                    start_y: height as f64 / 7.,
                    start_length: width as f64 / 3.,
                    cutout_length: width as f64 / 3. - 100.,
                    height: 50.,
                    end_length: width as f64 / 3. - 50.,
                    invert: false,
                }
                .draw(&pen);
                pen.stroke();

                AsymLine {
                    orientation: gtk::Orientation::Horizontal,
                    start_x: width as f64 / 4.,
                    start_y: height as f64 * 6. / 7.,
                    start_length: width as f64 * 2. / 3. - 25.,
                    height: 50.,
                    end_length: 0.,
                    invert: false,
                }
                .draw(&pen);
                pen.stroke();

                let tracery = pen.finish();
                let _ = context.set_source(tracery);
                let _ = context.paint();

                let mut animations = s.imp().animations.borrow_mut();

                let lr_margin = 50.;
                let max_width = width as f64 - lr_margin * 2.;
                let region_height = height as f64 / 5.;

                if let Some(animation) = animations.get(&Position::Top) {
                    let y = height as f64 * 1. / 5.;
                    let surface = context
                        .target()
                        .create_for_rectangle(Rectangle::new(20., y, max_width, region_height))
                        .unwrap();
                    let ctx = Context::new(&surface).unwrap();
                    animation.tick(now, &ctx, max_width);
                }
                if let Some(animation) = animations.get(&Position::Middle) {
                    let y = height as f64 * 2. / 5.;
                    let surface = context
                        .target()
                        .create_for_rectangle(Rectangle::new(20., y, max_width, region_height))
                        .unwrap();
                    let ctx = Context::new(&surface).unwrap();
                    animation.tick(now, &ctx, max_width);
                }
                if let Some(animation) = animations.get(&Position::Bottom) {
                    let y = height as f64 * 3. / 5.;
                    let surface = context
                        .target()
                        .create_for_rectangle(Rectangle::new(20., y, max_width, region_height))
                        .unwrap();
                    let ctx = Context::new(&surface).unwrap();
                    animation.tick(now, &ctx, max_width);
                }
            }
        });

        s
    }

    fn next_page(&self) {
        self.imp().next_page();
        self.queue_draw();
    }
}

fn main() {
    let script = Arc::new(RwLock::new(Script::default()));
    let app = gtk::Application::builder()
        .application_id("com.luminescent-dreams.cyberpunk-slideshow")
        .build();

    app.add_main_option(
        "script",
        glib::char::Char::from(b's'),
        glib::OptionFlags::IN_MAIN,
        glib::OptionArg::String,
        "",
        None,
    );

    app.connect_handle_local_options({
        let script = script.clone();
        move |_, options| {
            if let Some(script_path) = options.lookup::<String>("script").unwrap() {
                let mut script = script.write().unwrap();
                *script = Script::from_file(Path::new(&script_path)).unwrap();
                -1
            } else {
                1
            }
        }
    });

    app.connect_activate(move |app| {
        let screen = CyberScreen::new(script.read().unwrap().clone());

        let events = EventControllerKey::new();

        events.connect_key_released({
            let screen = screen.clone();
            move |_, key, _, _| {
                if key.name() == Some(GString::from("Right")) {
                    screen.next_page();
                }
            }
        });

        let window = gtk::ApplicationWindow::new(app);
        window.add_controller(events);

        window.set_child(Some(&screen));
        window.set_width_request(800);
        window.set_height_request(600);
        window.present();

        let _ = glib::spawn_future_local({
            let screen = screen.clone();
            async move {
                loop {
                    screen.queue_draw();
                    async_std::task::sleep(Duration::from_millis(1000 / FPS)).await;
                }
            }
        });
    });

    app.run();
}