use axum::{extract::Query, response::Html, routing::get, Router};
use cairo::{Context, Format, ImageSurface};
use rand::{rngs::ThreadRng, Rng};
use serde::Deserialize;
use std::net::SocketAddr;

#[tokio::main]
async fn main() {
    // build our application with a route
    let app = Router::new().route("/", get(handler));

    // run it
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    println!("listening on {}", addr);
    axum::Server::bind(&addr)
        .serve(app.into_make_service())
        .await
        .unwrap();
}

fn calculate_polygon_corners(
    center: (f64, f64),
    num_sides: i32,
    side_length: f64,
    rotation_angle_degrees: f64,
) -> Vec<(f64, f64)> {
    // no idea how this code works, it was written by ChatGPT
    let mut corners = Vec::new();
    let rotation_angle = rotation_angle_degrees.to_radians();
    let angle = std::f64::consts::PI / (num_sides as f64);
    let radius = side_length / (2.0 * angle.cos());

    for i in 0..num_sides {
        let vertex_angle = angle * (2.0 * i as f64 + 1.0 - num_sides as f64) + rotation_angle;
        let x = center.0 + radius * vertex_angle.sin();
        let y = center.1 + radius * vertex_angle.cos();
        corners.push((x, y));
    }

    corners
}

fn set_color_i8((r, g, b): (u8, u8, u8), context: &Context) {
    context.set_source_rgb(r as f64 / 255.0, g as f64 / 255.0, b as f64 / 255.0);
}

fn generate_color(
    rng: &mut ThreadRng,
    dark_mode: bool,
    unlike: Option<(u8, u8, u8)>,
) -> (u8, u8, u8) {
    let criteria = |(r, g, b): (u8, u8, u8)| {
        let r = r as u16;
        let g = g as u16;
        let b = b as u16;
        if dark_mode && (r + g + b) < 100 {
            return false;
        } else if !dark_mode && (r + g + b) > 600 {
            return false;
        }

        if let Some((r1, g1, b1)) = unlike {
            if (r.abs_diff(r1 as u16) + g.abs_diff(g1 as u16) + b.abs_diff(b1 as u16)) < 200 {
                return false;
            }
        }

        return true;
    };

    let mut color = rng.gen();

    while !criteria(color) {
        color = rng.gen();
    }

    color
}

fn draw_segmented_polygon(
    center: (f64, f64),
    side_length: f64,
    context: &Context,
    dark_mode: bool,
) {
    let mut rng = rand::thread_rng();
    let c1 = generate_color(&mut rng, dark_mode, None);
    set_color_i8(c1, context);
    context.new_path();

    let corners = calculate_polygon_corners(center, 6, side_length, 30.0);
    let corner1: u8 = rng.gen_range(0..6);
    let corner2: u8 = (corner1 + rng.gen_range(2..5)) % 6;

    let from_corner = std::cmp::min(corner1, corner2);
    let to_corner = std::cmp::max(corner1, corner2);

    // draw one side
    for i in from_corner..(to_corner + 1) {
        let (x, y) = corners[i as usize];
        context.line_to(x, y);
    }

    context.close_path();
    context.fill().unwrap();

    let c2 = generate_color(&mut rng, dark_mode, Some(c1));
    set_color_i8(c2, context);
    context.new_path();
    // draw other side
    for i in to_corner..(from_corner + 1 + 6) {
        let (x, y) = corners[(i % 6) as usize];
        context.line_to(x, y);
    }

    context.close_path();
    context.fill().unwrap();
}

fn default_as_false() -> bool {
    false
}

#[derive(Deserialize)]
struct ImageProperties {
    #[serde(default = "default_as_false")]
    dark_mode: bool,
}

async fn handler(Query(properties): Query<ImageProperties>) -> impl axum::response::IntoResponse {
    let surface = ImageSurface::create(Format::ARgb32, 400, 400).unwrap();
    let context = Context::new(&surface).unwrap();

    if properties.dark_mode {
        context.set_source_rgb(0.0, 0.0, 0.0);
    } else {
        context.set_source_rgb(1.0, 1.0, 1.0);
    }

    context.paint().unwrap();

    let corners = calculate_polygon_corners((200.0, 200.0), 6, 200.0, 0.0);
    for corner in corners {
        draw_segmented_polygon(corner, 80.0, &context, properties.dark_mode);
    }

    let mut data: Vec<u8> = Vec::new();
    surface.write_to_png(&mut data).unwrap();

    (
        axum::response::AppendHeaders([(axum::http::header::CONTENT_TYPE, "image/png")]),
        data,
    )
}