extern crate image;

use std::env;

fn main() {
    // First of all, retrieve the path from the program arguments:
    let path = match env::args_os().skip(1).next() {
        Some(p) => p,
        None => {
            println!("USAGE: ./image_wiewer <PATH>");
            return;
        }
    };
    // now, try to open the image
    // the image crate will take care of auto-detecting the file format
    let image = match image::open(&path) {
        Ok(i) => i,
        Err(e) => {
            println!("Failed to open image {}.", path.to_string_lossy());
            println!("Error was: {:?}", e);
            return;
        }
    };
    // We'll need the image in RGBA for drawing it
    let image = image.to_rgba();

    // ...
}

extern crate smithay-client-toolkit as sctk;
// sctk reexports Wayland-client for convenience
use sctk::reexports::client::Display;

fn main() {
    // ...

    let (display, mut event_queue) = Display::connect_to_env()
                                        .expect("Failed to connect to the Wayland server.");

    // ...
}

use sctk::Environment;
// our display object is actually of type `Proxy<WlDisplay>`, so we need to import
// this extension trait to access methods representing its requests
use sctk::reexports::client::protocol::wl_display::RequestsTrait as DisplayRequests;

fn main() {
    // ..

    // All request method of Wayland objects return a `Result`, as Wayland-client
    // returns an error if you try to send a message on an object that has already
    // been destroyed by a previous message. We know our display has not been
    // destroyed, so we unwrap().
    let registry = display.get_registry().unwrap();

    // The Environment takes a registry and a mutable borrow of the Wayland event
    // queue. It uses the event queue internally to exchange messages with the server
    // to process the registry event.
    // Like all manipulation of the event loop, it can fail (if the connection is
    // unexpectedly lost), and thus returns a Result. This failing would prevent
    // us to continue though, so we unrap().
    let env = Environment::from_registry(registry, &mut event_queue).unwrap();

    // ..
}

// the extension trait providing the requests for the compositor object
use sctk::reexports::client::protocol::wl_compositor::RequestsTrait as CompositorRequests;

fn main() {
    // ..

    // Use the compositor global to create a new surface
    let surface = env.compositor
        .create_surface()
        .unwrap() // unwrap for the same reasons as before, we know the compositor
                  // is not yet destroyed
        .implement(|_event, _surface| {
            // Here we implement this surface with a closure processing
            // the event
            //
            // Surface events notify us when it enters or leave an output,
            // this is mostly useful to track HiDPI-scaling.
            //
            // We don't do it in this example, so this closure ignores all
            // events by doing nothing.
        });

    // ..
}

use sctk::window::{BasicFrame, Event as WEvent, State, Window};

fn main() {
    // ..

    // First of all, this Arc<Mutex<Option<WEvent>>> will store
    // any event from the window that we need to process. We
    // store them and will process them later in the event loop
    // rather that process them directly because in a batch of
    // generated events, often only the last one needs to actually
    // be processed, and some events may render other obsoletes.
    // See the closure a few lines below for details
    let next_action = Arc::new(Mutex::new(None::<WEvent>));

    // We clone the arc to pass one end to the closure
    let waction = next_action.clone();
    // Now we actually create the window. The type parameter `BasicFrame` here
    // specifies the type we want to use to draw the borders. SCTK currently
    // only provide this one, but if you don't like the (arguably ugly)
    // borders it draws, you just need to implement the appropriate trait
    // to create your own.
    let mut window = Window::<BasicFrame>::init(
        surface,           // the wl_surface that serves as the basis of this window
        image.dimensions(),// the initial internal dimensions of the window (so excluding decorations)
        &env.compositor,   // -+
        &env.subcompositor,//  | The Window constructor needs access to these globals
        &env.shm,          //  | to initialize the window
        &env.shell,        // -+
        move |evt, ()| {
            // This is the closure that processes the Window events.
            // There are 3 possible events:
            // - Close: the user requested the window to be closed, we'll then quit
            // - Configure: the server suggested a new state for the window (possibly
            //   a new size if a resize is in progress). We'll likely need to redraw
            //   our contents
            // - Refresh: the frame itself needs to be redrawn. SCTK does not do this
            //   automatically because it has a cost and should only be done in parts
            //   of the event loop where the client actually wants to draw
            // Here we actually only keep the last event received according to a priority
            // order of Close > Configure > Refresh.
            // Indeed, if we received a Close, there is not point drawing anything anymore as
            // we will exit. A new Configure overrides a previous one, and if we received
            // a Configure we will refresh the frame anyway.
            let mut next_action = waction.lock().unwrap();
            // Check if we need to replace the old event by the new one
            let replace = match (&evt, &*next_action) {
                // replace if there is no old event
                (_, &None)
                // or the old event is refresh
                | (_, &Some(WEvent::Refresh))
                // or we had a configure and received a new one
                | (&WEvent::Configure { .. }, &Some(WEvent::Configure { .. }))
                // or the new event is close
                | (&WEvent::Close, _) => true,
                // keep the old event otherwise
                _ => false,
            };
            if replace {
                *next_action = Some(evt);
            }
        },
        // creating the window may fail if the code drawing the frame
        // fails to initialize itself. For BasicFrame this should not happen
        // unless the system is utterly broken, though.
    ).expect("Failed to create a window !");

    // The window needs access to pointer inputs to handle the user interaction
    // with it: resizing/moving the window, or clicking its button.
    // user interaction in Wayland is done via the wl_seat object, which represents
    // a set of pointer/keyboard/touchscreen (some may be absent) that logically
    // represent a single user. Most systems have only one seat, multi-seat configurations
    // are quite exotic.
    // Thus, we just automatically bind the first seat we find.
    let seat = env.manager
        .instantiate_auto::<wl_seat::WlSeat>()
        .unwrap()
        .implement(move |_, _| {});
    // And advertize it to the Window so it knows of it and can process the
    // required pointer events.
    window.new_seat(&seat);

    // ..
}

use sctk::utils::DoubleMemPool;

fn main() {
    // ...

    // DoubleMemPool::new() requires access to the wl_shm global, which represents
    // the capability of the server to use shared memory (SHM). All Wayland servers
    // are required to support it.
    let mut pools = DoubleMemPool::new(&env.shm).expect("Failed to create the memory pools.");

    // ...
}

extern crate byteorder;
// IO types to write the memory pool
use std::io::{BufWriter, Seek, SeekFrom, Write};
use byteorder::{NativeEndian, WriteBytesExt};

use sctk::reexports::client::NewProxy;
use sctk::reexports::client::protocol::wl_buffer;
use sctk::utils::MemPool;

// The draw function, which draws `base_image` in the provided `MemPool`,
// at given dimensions, and returns a wl_buffer to it.
//
// It simply returns the `NewProxy`, as we'll take care of implementing the
// wl_buffer outside of this function.
//
// If `base_image` is `None`, it'll just draw black contents. This is to
// improve performance during resizing: we need to redraw the window frequently
// so that its dimensions follow the pointer during the resizing, but resizing the
// image is costly and long. So during an interactive resize of the window we'll
// just draw black contents to not feel laggy.
fn draw(
    pool: &mut MemPool,
    base_image: Option<&image::ImageBuffer<image::Rgba<u8>, Vec<u8>>>,
    (buf_x, buf_y): (u32, u32),
) -> NewProxy<wl_buffer::WlBuffer> {
    // First of all, we make sure the pool is big enough to hold our
    // image. We'll write in ARGB8888 format, meaning 4 bytes per pixel.
    // This resize method will only resize the pool if the requested size is bigger
    // than the current size, as Wayland SHM pools are not allowed to shrink.
    //
    // While writing on the file would automatically grow it, we need to advertize the
    // server of its new size, so the call to this method is necessary.
    pool.resize((4 * buf_x * buf_y) as usize)
        .expect("Failed to resize the memory pool.");

    // Now, we can write the contents. MemPool implements the `Seek` and `Write` traits,
    // so we use it directly as a file to write on.

    // First, seek to the beginning, to overwrite our previous content.
    let _ = pool.seek(SeekFrom::Start(0));
    {
        // A sub-scope to limit our borrow of the pool by this BufWriter.
        // This BufWriter will significantly improve our drawing performance,
        // by reducing the number of syscals we do. =)
        let mut writer = BufWriter::new(&mut *pool);
        if let Some(base_image) = base_image {
            // We have an image to draw

            // first, resize it to the requested size. We just use the function provided
            // by the image crate here.
            let image =
                image::imageops::resize(base_image, buf_x, buf_y, image::FilterType::Nearest);

            // Now, we'll write the pixels of the image to the MemPool.
            //
            // We do this in an horribly inneficient maneer, for the sake of simplicity.
            // We'll send pixels to the server in ARGB8888 format (this is one of the only
            // formats that are guaranteed to be supported), but image provides it in
            // RGBA8888, so we need to do the conversion.
            //
            // Additionnaly, if the image has some transparent parts, we'll blend them into
            // a white background, otherwise the server will draw our window with a
            // transparent background!
            for pixel in image.pixels() {
                // retrieve the pixel values
                let r = pixel.data[0] as u32;
                let g = pixel.data[1] as u32;
                let b = pixel.data[2] as u32;
                let a = pixel.data[3] as u32;
                // blend them
                let r = ::std::cmp::min(0xFF, (0xFF*(0xFF-a) + a*r)/0xFF);
                let g = ::std::cmp::min(0xFF, (0xFF*(0xFF-a) + a*g)/0xFF);
                let b = ::std::cmp::min(0xFF, (0xFF*(0xFF-a) + a*b)/0xFF);
                // write the pixel
                // We use byteorder, as the Wayland protocol explicitly specifies
                // that the pixels must be written in native endianness
                let _ = writer.write_u32::<NativeEndian>(
                    (0xFF << 24) + (r << 16) + (g << 8) + b
                );
            }
        } else {
            // We do not have any image to draw, so we draw black contents
            for _ in 0..(buf_x * buf_y) {
                let _ = writer.write_u32::<NativeEndian>(0xFF000000);
            }
        }
        // Don't forget to flush the writer, to make sure all the contents are
        // indeed written to the file.
        let _ = writer.flush();
    }
    // Now, we create a buffer to the memory pool pointing to the contents
    // we just wrote
    return pool.buffer(
        0,                       // initial offset of the buffer in the pool
        buf_x as i32,            // width of the buffer, in pixels
        buf_y as i32,            // height of the buffer, in pixels
        4 * buf_x as i32,        // stride: number of bytes between the start of two
                                 //   consecutive rows of pixels
        wl_shm::Format::Argb8888,// the pixel format we wrote in
    )
}

fn main() {
    // ...

    // First, we initialize a few boolean flags that we'll use to track our state:
    // - the window needs to be redrawn
    let mut need_redraw = false;
    // - the frame needs to be refreshed
    let mut need_refresh = false;
    // - have we done the original bootstrap? Depending on the underlying shell
    //   protocol, we may need to wait until we receive a first configure event
    //   before drawing our window. This flag checks if this is done.
    let mut bootstrapped = false;
    // - number of currently free memory pool, which will be shared by the buffer
    //   implementations
    let free_pools = Rc::new(Cell::new(2u32));
    // - are we currently in the process of being resized? (to draw the image or
    //   black content)
    let mut resizing = false;
    // - a QueueToken, we'll need it to implement the buffers
    let token = event_queue.get_token();
    // - the size of our contents
    let mut dimensions = image.dimensions();

    // if our shell does not need to wait for a configure event, we draw right away.
    //
    // Note that this is only the case for the old wl_shell protocol, which is now
    // deprecated. This code is only for compatibility with old servers that do not
    // support the new standard xdg_shell protocol.
    //
    // But if we have made a fallback to wl_shell, we need to draw right away because we'll
    // never receive a configure event if we don't draw something...
    if !env.shell.needs_configure() {
        need_redraw = true;
        bootstrapped = true;
    }

    // We can now actually enter the event loop!
    loop {
        // First, check if any pending action was received by the
        // Window implementation:
        match next_action.lock().unwrap().take() {
            // We received a Close event, just break from the loop
            // and let the app quit
            Some(WEvent::Close) => break,
            // We received a Refresh event, store that we need to refresh the
            // frame
            Some(WEvent::Refresh) => {
                need_refresh = true;
            }
            // We received a configure event, our action depends on its
            // contents
            Some(WEvent::Configure { new_size, states }) => {
                // the configure event contains a suggested size,
                // if it is different from our current size, we need to
                // update it and redraw
                if let Some((w, h)) = new_size {
                    if dimensions != (w, h) {
                        dimensions = (w, h);
                        need_redraw = true;
                    }
                }
                // Are we currently resizing ?
                // We check if a resize operation just started or stopped,
                // because in this case we'll swap between drawing black
                // and drawing the window (or the reverse), and thus we need to
                // redraw
                let new_resizing = states.contains(&State::Resizing);
                if new_resizing != resizing {
                    need_redraw = true;
                }
                resizing = new_resizing;

                // If we have not bootstrapped yet, this is the first configure
                // event, time to draw for the first time.
                if !bootstrapped {
                    bootstrapped = true;
                    need_redraw = true;
                }
            }
            // No event, nothing new to do.
            None => {}
        }

        if need_redraw {
            // We need to redraw, but can only do it if at least one of the
            // memory pools is not currently used by the server. If both are
            // used, we'll keep the `need_redraw` flag to `true` and try again
            // at next iteration of the loop.
            if free_pools.get() > 0 {
                // Draw the contents in the pool and retrieve the buffer
                let new_buffer = draw(
                    pools.pool(),
                    if resizing { None } else { Some(&image) },
                    dimensions
                );
                // We implement this buffer to check when the server sends us the Release
                // event.
                // This method is unsafe for thread-safety reasons, as the callback we provide
                // is not Send/Synd (it uses an Rc<Cell<>>). But our app is not multi-threaded
                // here, so this is fine. =)
                let buffer = unsafe { new_buffer.implement_nonsend(
                    {
                        // get a handle to the free pools counter, for the closure
                        let notify = free_pools.clone();
                        // The closure that will be called when the Release event is
                        // received
                        // - wl_buffer::Event is an enum with a single variant
                        // - we need to annotate the buffer argument because rust's type
                        //   inference is unfortunately not good enough to find it alone
                        move |wl_buffer::Event::Release, buffer: Proxy<wl_buffer::WlBuffer>| {
                            // This buffer has been released by the server. Increment the
                            // count of free pools...
                            notify.set(notify.get()+1);
                            // ... and destroy the buffer
                            buffer.destroy();
                        }
                    },
                    &token
                ) };
                // Now, swap the MemPools, so next time we'll draw on the other.
                // This is double-buffering.
                pools.swap();
                // Register that one more pool is in use.
                free_pools.set(free_pools.get()-1);
                // Attach this new buffer to our surface.
                window.surface().attach(Some(&buffer), 0, 0);
                // We need to tell the server which parts of the surface have changed,
                // it uses it to only reload/redraw relevant parts for performance.
                // In our case everything has likely changed so we damage everything.
                //
                // Two ways are possible for notifying this damage:
                if window.surface().version() >= 4 {
                    // If our server is recent enough and supports at least version 4 of the
                    // wl_surface interface, we can specify the damage in buffer coordinates.
                    // This is obviously the best, so we do that if possible.
                    window.surface().damage_buffer(0, 0, dimensions.0 as i32, dimensions.1 as i32);
                } else {
                    // Otherwise, we fallback to compatilibity mode. Here we specify damage
                    // in surface coordinates, which would have been different if we had drawn
                    // our buffer at HiDPI resolution. We didn't though, so it is ok.
                    window.surface().damage(0, 0, dimensions.0 as i32, dimensions.1 as i32);
                }
                // We resize our frame, so that it is drawn at the right size by SCTK
                window.resize(dimensions.0, dimensions.1);
                // We also refresh it, so that SCTK actually draws it with the new size
                window.refresh();
                // We commit our drawing surface, so that the server atomically applies
                // all the changes we previously did.
                window.surface().commit();
                // We don't need to redraw or refresh anymore =)
                need_redraw = false;
                need_refresh = false;
            }
        } else if need_refresh {
            // If we don't need to redraw but only to refresh, do it
            window.refresh();
            // We still need to commit our surface, as the decorations are drawn as
            // subsurfaces of it.
            window.surface().commit();
            need_refresh = false;
        }

        // These last two calls are necessary for the processing of Wayland messages:
        // - first, flush all our requests to the server on the unix socket
        display.flush().unwrap();
        // - then, retrieve all the incoming messages
        //   this method blocks until a message arrives from the server, and will process
        //   all events by calling the implementation of the target object or each,
        //   and only return once all pending messages have been processed.
        event_queue.dispatch().unwrap();
    }
}