// based on the WebGL example in the `wasm-bindgen` guide
//
//   https://rustwasm.github.io/wasm-bindgen/examples/webgl.html
//
// and this StackOverflow answer by wangdq
//
//   https://stackoverflow.com/a/39684775
//

extern crate js_sys;
use core::array;
use nalgebra::DVector;
use sycamore::{prelude::*, rt::{JsCast, JsValue}};
use web_sys::{console, WebGl2RenderingContext, WebGlProgram, WebGlShader, WebGlUniformLocation};

mod engine;

fn compile_shader(
    context: &WebGl2RenderingContext,
    shader_type: u32,
    source: &str,
) -> WebGlShader {
    let shader = context.create_shader(shader_type).unwrap();
    context.shader_source(&shader, source);
    context.compile_shader(&shader);
    shader
}

fn get_uniform_array_locations<const N: usize>(
    context: &WebGl2RenderingContext,
    program: &WebGlProgram,
    var_name: &str,
    member_name_opt: Option<&str>
) -> [Option<WebGlUniformLocation>; N] {
    array::from_fn(|n| {
        let name = match member_name_opt {
            Some(member_name) => format!("{var_name}[{n}].{member_name}"),
            None => format!("{var_name}[{n}]")
        };
        context.get_uniform_location(&program, name.as_str())
    })
}

// load the given data into the vertex input of the given name
fn bind_vertex_attrib(
    context: &WebGl2RenderingContext,
    index: u32,
    size: i32,
    data: &[f32]
) {
    // create a data buffer and bind it to ARRAY_BUFFER
    let buffer = context.create_buffer().unwrap();
    context.bind_buffer(WebGl2RenderingContext::ARRAY_BUFFER, Some(&buffer));
    
    // load the given data into the buffer. the function `Float32Array::view`
    // creates a raw view into our module's `WebAssembly.Memory` buffer.
    // allocating more memory will change the buffer, invalidating the view.
    // that means we have to make sure we don't allocate any memory until the
    // view is dropped
    unsafe {
        context.buffer_data_with_array_buffer_view(
            WebGl2RenderingContext::ARRAY_BUFFER,
            &js_sys::Float32Array::view(&data),
            WebGl2RenderingContext::STATIC_DRAW,
        );
    }
    
    // allow the target attribute to be used
    context.enable_vertex_attrib_array(index);
    
    // take whatever's bound to ARRAY_BUFFER---here, the data buffer created
    // above---and bind it to the target attribute
    //
    //   https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/vertexAttribPointer
    //
    context.vertex_attrib_pointer_with_i32(
        index,
        size,
        WebGl2RenderingContext::FLOAT,
        false, // don't normalize
        0, // zero stride
        0, // zero offset
    );
}

fn main() {
    // set up a config option that forwards panic messages to `console.error`
    #[cfg(feature = "console_error_panic_hook")]
    console_error_panic_hook::set_once();
    
    sycamore::render(|| {
        // controls
        let ctrl_x = create_signal(0.0);
        let ctrl_y = create_signal(0.0);
        let radius_x = create_signal(1.0);
        let radius_y = create_signal(1.0);
        let opacity = create_signal(0.5);
        let highlight = create_signal(0.2);
        let layer_threshold = create_signal(0.0);
        let use_test_construction = create_signal(false);
        
        // display
        let display = create_node_ref();
        
        on_mount(move || {
            // list construction elements
            const SPHERE_MAX: usize = 12;
            let mut sphere_vec = Vec::<DVector<f64>>::new();
            let color_vec = vec![
                [1.00_f32, 0.25_f32, 0.00_f32],
                [0.00_f32, 0.25_f32, 1.00_f32],
                [0.25_f32, 0.00_f32, 1.00_f32]
            ];
            
            // get the display canvas
            let canvas = display
                .get::<DomNode>()
                .unchecked_into::<web_sys::HtmlCanvasElement>();
            let ctx = canvas
                .get_context("webgl2")
                .unwrap()
                .unwrap()
                .dyn_into::<WebGl2RenderingContext>()
                .unwrap();
            
            // compile and attach the vertex and fragment shaders
            let vertex_shader = compile_shader(
                &ctx,
                WebGl2RenderingContext::VERTEX_SHADER,
                include_str!("identity.vert"),
            );
            let fragment_shader = compile_shader(
                &ctx,
                WebGl2RenderingContext::FRAGMENT_SHADER,
                include_str!("inversive.frag"),
            );
            let program = ctx.create_program().unwrap();
            ctx.attach_shader(&program, &vertex_shader);
            ctx.attach_shader(&program, &fragment_shader);
            ctx.link_program(&program);
            let link_status = ctx
                .get_program_parameter(&program, WebGl2RenderingContext::LINK_STATUS)
                .as_bool()
                .unwrap();
            let link_msg = if link_status {
                "Linked successfully"
            } else {
                "Linking failed"
            };
            console::log_1(&JsValue::from(link_msg));
            ctx.use_program(Some(&program));
            
            /* DEBUG */
            // print the maximum number of vectors that can be passed as
            // uniforms to a fragment shader. the OpenGL ES 3.0 standard
            // requires this maximum to be at least 224, as discussed in the
            // documentation of the GL_MAX_FRAGMENT_UNIFORM_VECTORS parameter
            // here:
            //
            //   https://registry.khronos.org/OpenGL-Refpages/es3.0/html/glGet.xhtml
            //
            // there are also other size limits. for example, on Aaron's
            // machine, the the length of a float or genType array seems to be
            // capped at 1024 elements
            console::log_2(
                &ctx.get_parameter(WebGl2RenderingContext::MAX_FRAGMENT_UNIFORM_VECTORS).unwrap(),
                &JsValue::from("uniform vectors available")
            );
            
            // find indices of vertex attributes and uniforms
            let position_index = ctx.get_attrib_location(&program, "position") as u32;
            let sphere_cnt_loc = ctx.get_uniform_location(&program, "sphere_cnt");
            let sphere_sp_locs = get_uniform_array_locations::<SPHERE_MAX>(
                &ctx, &program, "sphere_list", Some("sp")
            );
            let sphere_lt_locs = get_uniform_array_locations::<SPHERE_MAX>(
                &ctx, &program, "sphere_list", Some("lt")
            );
            let color_locs = get_uniform_array_locations::<SPHERE_MAX>(
                &ctx, &program, "color_list", None
            );
            let resolution_loc = ctx.get_uniform_location(&program, "resolution");
            let shortdim_loc = ctx.get_uniform_location(&program, "shortdim");
            let ctrl_loc = ctx.get_uniform_location(&program, "ctrl"); /* DEBUG */
            let radius_loc = ctx.get_uniform_location(&program, "radius"); /* DEBUG */
            let opacity_loc = ctx.get_uniform_location(&program, "opacity");
            let highlight_loc = ctx.get_uniform_location(&program, "highlight");
            let layer_threshold_loc = ctx.get_uniform_location(&program, "layer_threshold");
            let use_test_construction_loc = ctx.get_uniform_location(&program, "use_test_construction");
            
            // create a vertex array and bind it to the graphics context
            let vertex_array = ctx.create_vertex_array().unwrap();
            ctx.bind_vertex_array(Some(&vertex_array));
            
            // set the vertex positions
            const VERTEX_CNT: usize = 6;
            let positions: [f32; 3*VERTEX_CNT] = [
                // northwest triangle
                -1.0, -1.0, 0.0,
                -1.0,  1.0, 0.0,
                 1.0,  1.0, 0.0,
                // southeast triangle
                -1.0, -1.0, 0.0,
                 1.0,  1.0, 0.0,
                 1.0, -1.0, 0.0
            ];
            bind_vertex_attrib(&ctx, position_index, 3, &positions);
            
            // set up a repainting routine
            create_effect(move || {
                // update the construction
                sphere_vec.clear();
                sphere_vec.push(engine::sphere(0.5, 0.5, -5.0 + ctrl_x.get(), radius_x.get()));
                sphere_vec.push(engine::sphere(-0.5, -0.5, -5.0 + ctrl_y.get(), radius_y.get()));
                sphere_vec.push(engine::sphere(-0.5, 0.5, -5.0, 0.75));
                
                // set the resolution
                let width = canvas.width() as f32;
                let height = canvas.height() as f32;
                ctx.uniform2f(resolution_loc.as_ref(), width, height);
                ctx.uniform1f(shortdim_loc.as_ref(), width.min(height));
                
                // pass the construction
                ctx.uniform1i(sphere_cnt_loc.as_ref(), sphere_vec.len() as i32);
                for n in 0..sphere_vec.len() {
                    let v = &sphere_vec[n];
                    ctx.uniform3f(
                        sphere_sp_locs[n].as_ref(),
                        v[0] as f32, v[1] as f32, v[2] as f32
                    );
                    ctx.uniform2f(
                        sphere_lt_locs[n].as_ref(),
                        v[3] as f32, v[4] as f32
                    );
                    ctx.uniform3fv_with_f32_array(
                        color_locs[n].as_ref(),
                        &color_vec[n]
                    );
                }
                
                // pass the control parameters
                ctx.uniform2f(ctrl_loc.as_ref(), ctrl_x.get() as f32, ctrl_y.get() as f32); /* DEBUG */
                ctx.uniform2f(radius_loc.as_ref(), radius_x.get() as f32, radius_y.get() as f32); /* DEBUG */
                ctx.uniform1f(opacity_loc.as_ref(), opacity.get() as f32);
                ctx.uniform1f(highlight_loc.as_ref(), highlight.get() as f32);
                ctx.uniform1i(layer_threshold_loc.as_ref(), layer_threshold.get() as i32);
                ctx.uniform1i(use_test_construction_loc.as_ref(), use_test_construction.get() as i32);
                
                // draw the scene
                ctx.draw_arrays(WebGl2RenderingContext::TRIANGLES, 0, VERTEX_CNT as i32);
            });
        });
        
        view! {
            div(id="app") {
                canvas(ref=display, width="600", height="600")
                div(class="control") {
                    label(for="ctrl-x") { "Sphere 0 depth" }
                    input(
                        type="range",
                        id="ctrl-x",
                        min=-1.0,
                        max=1.0,
                        step=0.001,
                        bind:valueAsNumber=ctrl_x
                    )
                }
                div(class="control") {
                    label(for="ctrl-y") { "Sphere 1 depth" }
                    input(
                        type="range",
                        id="ctrl-y",
                        min=-1.0,
                        max=1.0,
                        step=0.001,
                        bind:valueAsNumber=ctrl_y
                    )
                }
                div(class="control") {
                    label(for="radius-x") { "Sphere 0 radius" }
                    input(
                        type="range",
                        id="radius-x",
                        min=0.5,
                        max=1.5,
                        step=0.001,
                        bind:valueAsNumber=radius_x
                    )
                }
                div(class="control") {
                    label(for="radius-y") { "Sphere 1 radius" }
                    input(
                        type="range",
                        id="radius-y",
                        min=0.5,
                        max=1.5,
                        step=0.001,
                        bind:valueAsNumber=radius_y
                    )
                }
                div(class="control") {
                    label(for="opacity") { "Opacity" }
                    input(
                        type="range",
                        id="opacity",
                        max=1.0,
                        step=0.001,
                        bind:valueAsNumber=opacity
                    )
                }
                div(class="control") {
                    label(for="highlight") { "Highlight" }
                    input(
                        type="range",
                        id="highlight",
                        max=1.0,
                        step=0.001,
                        bind:valueAsNumber=highlight
                    )
                }
                div(class="control") {
                    label(for="layer-threshold") { "Layer threshold" }
                    input(
                        type="range",
                        id="layer-threshold",
                        max=5.0,
                        step=1.0,
                        bind:valueAsNumber=layer_threshold
                    )
                }
                div(class="control") {
                    label(for="use-test-construction") { "Use test values" }
                    input(
                        type="checkbox",
                        id="use-test-construction",
                        bind:checked=use_test_construction
                    )
                }
            }
        }
    });
}