use vulkano::buffer::{BufferUsage, CpuAccessibleBuffer};
use vulkano::command_buffer::{AutoCommandBufferBuilder, DynamicState};
use vulkano::device::{Device, DeviceExtensions};
use vulkano::framebuffer::{Framebuffer, FramebufferAbstract, Subpass, RenderPassAbstract};
use vulkano::image::{SwapchainImage, AttachmentImage};
use vulkano::instance::{Instance, PhysicalDevice, ApplicationInfo, Version, InstanceExtensions};
use vulkano::pipeline::{GraphicsPipeline};
use vulkano::pipeline::shader::{GraphicsShaderType, ShaderModule};
use vulkano::pipeline::viewport::Viewport;
use vulkano::swapchain::{AcquireError, PresentMode, SurfaceTransform, Swapchain, SwapchainCreationError};
use vulkano::swapchain;
use vulkano::sync::{GpuFuture, FlushError};
use vulkano::sync;
use vulkano::pipeline::vertex::SingleBufferDefinition;
use vulkano::descriptor::PipelineLayoutAbstract;
use vulkano::format::Format;

use vulkano_win::VkSurfaceBuild;

use winit::{EventsLoop, Window, WindowBuilder, Event, WindowEvent};

use std::sync::Arc;
use std::time::SystemTime;
use std::path::PathBuf;
use std::ffi::{CStr};

use shade_runner;
use shade_runner::{CompiledShaders, Entry};

use shaderc;
use crate::PushConstants;
use vulkano::instance::debug::{DebugCallback, MessageTypes};

const VALIDATION_LAYERS: &[&str] =  &[
    "VK_LAYER_LUNARG_standard_validation"
];

#[cfg(all(debug_assertions))]
const ENABLE_VALIDATION_LAYERS: bool = true;
#[cfg(not(debug_assertions))]
const ENABLE_VALIDATION_LAYERS: bool = false;

#[derive(Default, Debug, Clone)]
pub struct Vertex {
    pub position: [f32; 3],
}
vulkano::impl_vertex!(Vertex, position);

pub struct GameData<'a> {
    pub start_time: SystemTime,
    pub mesh_vertices: Vec<Vertex>,
    pub line_vertices: Vec<Vertex>,
    pub push_constants: &'a mut PushConstants,
    pub recreate_pipeline: bool,
    pub aspect_ratio: f32,
    pub shutdown: bool,
}

pub fn init(mut game: GameData) {
    if ENABLE_VALIDATION_LAYERS {
        println!("Enabling validation layers...");
    }

    let instance = {
        let extensions = InstanceExtensions {
            ext_debug_report: true,
            ..vulkano_win::required_extensions()
        };

        let app_info = ApplicationInfo {
            application_name: Some("Asuro Editor".into()),
            application_version: Some(Version { major: 0, minor: 1, patch: 0 }),
            engine_name: Some("Asuro Rust Engine".into()),
            engine_version: Some(Version { major: 0, minor: 1, patch: 0 })
        };

        if ENABLE_VALIDATION_LAYERS {
            let available_layers = vulkano::instance::layers_list().unwrap().map(|layer| String::from(layer.name())).collect::<Vec<String>>();

            VALIDATION_LAYERS.iter().for_each(|wanted_layer_name| {
                if !available_layers.iter().any(|available_layer_name| available_layer_name == wanted_layer_name) {
                    panic!("Validation layer not found: {:?}. Available layers: {:?}", wanted_layer_name, &available_layers.join(", "));
                }
            });

            Instance::new(Some(&app_info), &extensions, VALIDATION_LAYERS.iter().cloned()).expect("failed to create Vulkan instance")
        } else {
            Instance::new(Some(&app_info), &extensions, None).expect("failed to create Vulkan instance")
        }
    };

    // lifetime of this is important, even tho it isn't used!
    let mut _debug_callback = None;
    if ENABLE_VALIDATION_LAYERS {
        let msg_types = MessageTypes {
            error: true,
            warning: true,
            performance_warning: true,
            information: false,
            debug: true,
        };

        _debug_callback = DebugCallback::new(&instance, msg_types, |msg| {
            let type_str = match (msg.ty.error, msg.ty.warning, msg.ty.performance_warning, msg.ty.information, msg.ty.debug) {
                (true, _, _, _, _) => "!!",
                (_, true, _, _, _) => "!",
                (_, _, true, _, _) => "p",
                (_, _, _, true, _) => "i",
                _ => " "
            };

            let layer_str = msg.layer_prefix;

            println!("[{}][{}]: {}", type_str, layer_str, msg.description);
        }).ok();
    }

    let physical = PhysicalDevice::enumerate(&instance).next().unwrap();
    println!("Using device: {} (type: {:?})", physical.name(), physical.ty());

    let mut events_loop = EventsLoop::new();
    let surface = WindowBuilder::new().build_vk_surface(&events_loop, instance.clone()).unwrap();
    let window = surface.window();

    // The next step is to choose which GPU queue will execute our draw commands.
    //
    // Devices can provide multiple queues to run commands in parallel (for example a draw queue
    // and a compute queue), similar to CPU threads. This is something you have to have to manage
    // manually in Vulkan.
    //
    // In a real-life application, we would probably use at least a graphics queue and a transfers
    // queue to handle data transfers in parallel. In this example we only use one queue.
    //
    // We have to choose which queues to use early on, because we will need this info very soon.
    let queue_family = physical.queue_families().find(|&q| {
        q.supports_graphics() && surface.is_supported(q).unwrap_or(false)
    }).unwrap();

    let device_ext = DeviceExtensions { khr_swapchain: true, .. DeviceExtensions::none() };
    let (device, mut queues) = Device::new(physical, physical.supported_features(), &device_ext,
                                       [(queue_family, 0.5)].iter().cloned()).unwrap();
    let queue = queues.next().unwrap();

    let (mut swapchain, images) = {
        let caps = surface.capabilities(physical).unwrap();

        let usage = caps.supported_usage_flags;

        // The alpha mode indicates how the alpha value of the final image will behave. For example
        // you can choose whether the window will be opaque or transparent.
        let alpha = caps.supported_composite_alpha.iter().next().unwrap();

        // Choosing the internal format that the images will have.
        let format = caps.supported_formats[0].0;

        // The dimensions of the window, only used to initially setup the swapchain.
        // NOTE:
        // On some drivers the swapchain dimensions are specified by `caps.current_extent` and the
        // swapchain size must use these dimensions.
        // These dimensions are always the same as the window dimensions
        //
        // However other drivers dont specify a value i.e. `caps.current_extent` is `None`
        // These drivers will allow anything but the only sensible value is the window dimensions.
        //
        // Because for both of these cases, the swapchain needs to be the window dimensions, we just use that.
        let initial_dimensions = if let Some(dimensions) = window.get_inner_size() {
            // convert to physical pixels
            let dimensions: (u32, u32) = dimensions.to_physical(window.get_hidpi_factor()).into();
            [dimensions.0, dimensions.1]
        } else {
            // The window no longer exists so exit the application.
            panic!("idk");
        };

        // Please take a look at the docs for the meaning of the parameters we didn't mention.
        Swapchain::new(device.clone(), surface.clone(), caps.min_image_count, format,
                       initial_dimensions, 1, usage, &queue, SurfaceTransform::Identity, alpha,
                       PresentMode::Fifo, true, None).unwrap()
    };

    let mesh_vertex_buffer = CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), game.mesh_vertices.iter().cloned()).unwrap();
    let line_vertex_buffer = CpuAccessibleBuffer::from_iter(device.clone(), BufferUsage::all(), game.line_vertices.iter().cloned()).unwrap();

    let render_pass = Arc::new(vulkano::single_pass_renderpass!(
        device.clone(),
        attachments: {
            color: {
                load: Clear,
                store: Store,
                format: swapchain.format(),
                samples: 1,
            },
            depth: {
                load: Clear,
                store: DontCare,
                format: Format::D16Unorm,
                samples: 1,
            }
        },
        pass: {
            color: [color],
            depth_stencil: {depth}
        }
    ).unwrap());

    let sub_pass = Subpass::from(render_pass.clone(), 0).unwrap();

    let mut pipeline = create_pipeline(device.clone(), sub_pass.clone(), "shaders/triangle.vert", "shaders/triangle.frag", false).unwrap();
    let line_pipeline = create_pipeline(device.clone(), sub_pass.clone(), "shaders/line.vert", "shaders/line.frag", true).unwrap();

    // Dynamic viewports allow us to recreate just the viewport when the window is resized
    // Otherwise we would have to recreate the whole pipeline.
    let mut dynamic_state = DynamicState { line_width: None, viewports: None, scissors: None };

    // The render pass we created above only describes the layout of our framebuffers. Before we
    // can draw we also need to create the actual framebuffers.
    //
    // Since we need to draw to multiple images, we are going to create a different framebuffer for
    // each image.
    let mut framebuffers = window_size_dependent_setup(device.clone(), &images, render_pass.clone(), &mut dynamic_state, &mut game.aspect_ratio);

    // In some situations, the swapchain will become invalid by it This includes for example
    // when the window is resized (as the images of the swapchain will no longer match the
    // window's) or, on Android, when the application went to the background and goes back to the
    // foreground.
    //
    // In this situation, acquiring a swapchain image or presenting it will return an error.
    // Rendering to an image of that swapchain will not produce any error, but may or may not work.
    // To continue rendering, we need to recreate the swapchain by creating a new swapchain.
    // Here, we remember that we need to do this for the next loop iteration.
    let mut recreate_swapchain = false;

    // In the loop below we are going to submit commands to the GPU. Submitting a command produces
    // an object that implements the `GpuFuture` trait, which holds the resources for as long as
    // they are in use by the GPU.
    //
    // Destroying the `GpuFuture` blocks until the GPU is finished executing it. In order to avoid
    // that, we store the submission of the previous frame here.
    let mut previous_frame_end = Box::new(sync::now(device.clone())) as Box<dyn GpuFuture>;

    loop {
        // It is important to call this function from time to time, otherwise resources will keep
        // accumulating and you will eventually reach an out of memory error.
        // Calling this function polls various fences in order to determine what the GPU has
        // already processed, and frees the resources that are no longer needed.
        previous_frame_end.cleanup_finished();

        // Whenever the window resizes we need to recreate everything dependent on the window size.
        // In this example that includes the swapchain, the framebuffers and the dynamic state viewport.
        if recreate_swapchain {
            // Get the new dimensions of the window.
            let dimensions = if let Some(dimensions) = window.get_inner_size() {
                let dimensions: (u32, u32) = dimensions.to_physical(window.get_hidpi_factor()).into();
                [dimensions.0, dimensions.1]
            } else {
                return;
            };

            let (new_swapchain, new_images) = match swapchain.recreate_with_dimension(dimensions) {
                Ok(r) => r,
                // This error tends to happen when the user is manually resizing the window.
                // Simply restarting the loop is the easiest way to fix this issue.
                Err(SwapchainCreationError::UnsupportedDimensions) => continue,
                Err(err) => panic!("{:?}", err)
            };

            swapchain = new_swapchain;
            // Because framebuffers contains an Arc on the old swapchain, we need to
            // recreate framebuffers as well.
            framebuffers = window_size_dependent_setup(device.clone(), &new_images, render_pass.clone(), &mut dynamic_state, &mut game.aspect_ratio);

            recreate_swapchain = false;
        }

        if game.recreate_pipeline {
            if let Some(pipeline_ok) = create_pipeline(device.clone(), sub_pass.clone(), "shaders/triangle.vert", "shaders/triangle.frag", false) {
                pipeline = pipeline_ok;
                println!("Updated pipeline.");
            } else {
                println!("Failed to update pipeline.");
            }
            game.recreate_pipeline = false;
        }

        // Before we can draw on the output, we have to *acquire* an image from the swapchain. If
        // no image is available (which happens if you submit draw commands too quickly), then the
        // function will block.
        // This operation returns the index of the image that we are allowed to draw upon.
        //
        // This function can block if no image is available. The parameter is an optional timeout
        // after which the function call will return an error.
        let (image_num, acquire_future) = match swapchain::acquire_next_image(swapchain.clone(), None) {
            Ok(r) => r,
            Err(AcquireError::OutOfDate) => {
                recreate_swapchain = true;
                continue;
            },
            Err(err) => panic!("{:?}", err)
        };

        // Specify the color to clear the framebuffer with i.e. blue
        let clear_values = vec!([0.0, 0.0, 1.0, 1.0].into(), 1f32.into());

        game.update_push_constants();

        // In order to draw, we have to build a *command buffer*. The command buffer object holds
        // the list of commands that are going to be executed.
        //
        // Building a command buffer is an expensive operation (usually a few hundred
        // microseconds), but it is known to be a hot path in the driver and is expected to be
        // optimized.
        //
        // Note that we have to pass a queue family when we create the command buffer. The command
        // buffer will only be executable on that given queue family.
        let command_buffer = AutoCommandBufferBuilder::primary_one_time_submit(device.clone(), queue.family()).unwrap()
            // Before we can draw, we have to *enter a render pass*. There are two methods to do
            // this: `draw_inline` and `draw_secondary`. The latter is a bit more advanced and is
            // not covered here.
            //
            // The third parameter builds the list of values to clear the attachments with. The API
            // is similar to the list of attachments when building the framebuffers, except that
            // only the attachments that use `load: Clear` appear in the list.
            .begin_render_pass(framebuffers[image_num].clone(), false, clear_values).unwrap()

            // We are now inside the first subpass of the render pass. We add a draw command.
            //
            // The last two parameters contain the list of resources to pass to the shaders.
            // Since we used an `EmptyPipeline` object, the objects have to be `()`.
            .draw(pipeline.clone(), &dynamic_state, mesh_vertex_buffer.clone(), (), game.push_constants.clone()).unwrap()
            .draw(line_pipeline.clone(), &dynamic_state, line_vertex_buffer.clone(), (), ()).unwrap()

            // We leave the render pass by calling `draw_end`. Note that if we had multiple
            // subpasses we could have called `next_inline` (or `next_secondary`) to jump to the
            // next subpass.
            .end_render_pass().unwrap()

            // Finish building the command buffer by calling `build`.
            .build().unwrap();

        let future = previous_frame_end.join(acquire_future)
            .then_execute(queue.clone(), command_buffer).unwrap()

            // The color output is now expected to contain our triangle. But in order to show it on
            // the screen, we have to *present* the image by calling `present`.
            //
            // This function does not actually present the image immediately. Instead it submits a
            // present command at the end of the queue. This means that it will only be presented once
            // the GPU has finished executing the command buffer that draws the triangle.
            .then_swapchain_present(queue.clone(), swapchain.clone(), image_num)
            .then_signal_fence_and_flush();

        match future {
            Ok(future) => {
                previous_frame_end = Box::new(future) as Box<_>;
            }
            Err(FlushError::OutOfDate) => {
                recreate_swapchain = true;
                previous_frame_end = Box::new(sync::now(device.clone())) as Box<_>;
            }
            Err(e) => {
                println!("{:?}", e);
                previous_frame_end = Box::new(sync::now(device.clone())) as Box<_>;
            }
        }

        // Note that in more complex programs it is likely that one of `acquire_next_image`,
        // `command_buffer::submit`, or `present` will block for some time. This happens when the
        // GPU's queue is full and the driver has to wait until the GPU finished some work.
        //
        // Unfortunately the Vulkan API doesn't provide any way to not wait or to detect when a
        // wait would happen. Blocking may be the desired behavior, but if you don't want to
        // block you should spawn a separate thread dedicated to submissions.

        // Handling the window events in order to close the program when the user wants to close
        // it.
        events_loop.poll_events(|ev| {
            if !game.on_window_event(&ev) {
                match ev {
                    Event::WindowEvent { event: WindowEvent::CloseRequested, .. } => game.shutdown = true,
                    Event::WindowEvent { event: WindowEvent::Resized(_), .. } => recreate_swapchain = true,
                    _ => {}
                }
            }
        });
        if game.shutdown { return; }
    }
}

/// This method is called once during initialization, then again whenever the window is resized
fn window_size_dependent_setup(device: Arc<Device>, images: &[Arc<SwapchainImage<Window>>], render_pass: Arc<dyn RenderPassAbstract + Send + Sync>, dynamic_state: &mut DynamicState, aspect_ratio: &mut f32) -> Vec<Arc<dyn FramebufferAbstract + Send + Sync>> {
    let dimensions = images[0].dimensions();
    *aspect_ratio = dimensions[0] as f32 / dimensions[1] as f32;

    let viewport = Viewport {
        origin: [0.0, 0.0],
        dimensions: [dimensions[0] as f32, dimensions[1] as f32],
        depth_range: 0.0 .. 1.0,
    };
    dynamic_state.viewports = Some(vec!(viewport));

    let depth_buffer = AttachmentImage::transient(device.clone(), dimensions, Format::D16Unorm).unwrap();

    images.iter().map(|image| {
        Arc::new(Framebuffer::start(render_pass.clone())
            .add(image.clone()).unwrap()
            .add(depth_buffer.clone()).unwrap()
            .build().unwrap()
        ) as Arc<dyn FramebufferAbstract + Send + Sync>
    }).collect::<Vec<_>>()
}

fn create_pipeline<T: RenderPassAbstract>(device: Arc<Device>, sub_pass: Subpass<Arc<T>>, vertex_shader_path: &str, fragment_shader_path: &str, is_line: bool) -> Option<Arc<GraphicsPipeline<SingleBufferDefinition<Vertex>, Box<dyn PipelineLayoutAbstract + Send + Sync>, Arc<T>>>> {
    if let Some((shader, shader_data)) = read_shader(vertex_shader_path, fragment_shader_path) {
        let vertex_shader_entry;
        let fragment_shader_entry;
        let vertex_shader_module;
        let fragment_shader_module;

        unsafe {
            vertex_shader_module = ShaderModule::from_words(device.clone(), &shader.vertex).expect("Failed to load vertex shader.");
            vertex_shader_entry = vertex_shader_module.graphics_entry_point(
                CStr::from_bytes_with_nul_unchecked(b"main\0"),
                shader_data.vert_input,
                shader_data.vert_output,
                shader_data.vert_layout,
                GraphicsShaderType::Vertex);
            fragment_shader_module = ShaderModule::from_words(device.clone(), &shader.fragment).expect("Failed to load fragment shader.");
            fragment_shader_entry = fragment_shader_module.graphics_entry_point(
                CStr::from_bytes_with_nul_unchecked(b"main\0"),
                shader_data.frag_input,
                shader_data.frag_output,
                shader_data.frag_layout,
                GraphicsShaderType::Fragment);
        };

        let pipeline;
        if is_line {
            pipeline = Arc::new(GraphicsPipeline::start()
                .vertex_input_single_buffer::<Vertex>()
                .vertex_shader(vertex_shader_entry.clone(), ())
                .line_list()
                .viewports_dynamic_scissors_irrelevant(1)
                .fragment_shader(fragment_shader_entry.clone(), ())
                .render_pass(sub_pass.clone())
                .build(device.clone())
                .unwrap());
        } else {
            // Before we draw we have to create what is called a pipeline. This is similar to an OpenGL
            // program, but much more specific.
            pipeline = Arc::new(GraphicsPipeline::start()
                .vertex_input_single_buffer::<Vertex>()
                // A Vulkan shader can in theory contain multiple entry points, so we have to specify
                // which one. The `main` word of `main_entry_point` actually corresponds to the name of
                // the entry point.
                .vertex_shader(vertex_shader_entry.clone(), ())
                .triangle_list()
                // Use a resizable viewport set to draw over the entire window
                .viewports_dynamic_scissors_irrelevant(1)
                .fragment_shader(fragment_shader_entry.clone(), ())
                // We have to indicate which subpass of which render pass this pipeline is going to be used
                // in. The pipeline will only be usable from this particular subpass.
                .render_pass(sub_pass.clone())
                .build(device.clone())
                .unwrap());
        }

        return Some(pipeline);
    } else {
        return None;
    }
}

fn read_shader(vert_path_relative: &str, frag_path_relative: &str) -> Option<(CompiledShaders, Entry)> {
    let project_root = std::env::current_dir().expect("failed to get root directory");

    let mut vert_path = project_root.clone();
    vert_path.push(PathBuf::from(vert_path_relative));

    let mut frag_path = project_root.clone();
    frag_path.push(PathBuf::from(frag_path_relative));

    let shader_result = shade_runner::load(vert_path, frag_path);
    match shader_result {
        Ok(shader) => {
            let shader_data = shade_runner::parse(&shader).expect("Failed to parse");
            return Some((shader, shader_data));
        }
        Err(shade_runner::error::Error::Compile(shade_runner::error::CompileError::Compile(shaderc::Error::CompilationError(line, error)))) => {
            println!("Shader line {}: {:?}", line, error);
            return None;
        }
        Err(error) => {
            println!("Shader compilation error: {:?}", error);
            return None;
        }
    }
}