// SPDX-License-Identifier: GPL-3.0-only

#[cfg(feature = "debug")]
use crate::state::Fps;

use crate::{
    backend::render,
    config::OutputConfig,
    state::{BackendData, Common, State},
    utils::GlobalDrop,
};

use anyhow::{Context, Result};
use smithay::{
    backend::{
        allocator::{gbm::GbmDevice, Format},
        drm::{DrmDevice, DrmEvent, DrmEventTime, DrmNode, GbmBufferedSurface, NodeType},
        egl::{EGLContext, EGLDevice, EGLDisplay},
        libinput::{LibinputInputBackend, LibinputSessionInterface},
        renderer::{
            multigpu::{egl::EglGlesBackend, GpuManager},
            Bind,
        },
        session::{auto::AutoSession, Session, Signal},
        udev::{all_gpus, primary_gpu, UdevBackend, UdevEvent},
    },
    reexports::{
        calloop::{
            timer::{Timer, TimerHandle},
            Dispatcher, EventLoop, LoopHandle, RegistrationToken,
        },
        drm::control::{connector, crtc, Device as ControlDevice, ModeTypeFlags},
        input::Libinput,
        nix::{fcntl::OFlag, sys::stat::dev_t},
        wayland_server::{protocol::wl_output, Display},
    },
    utils::signaling::{Linkable, Signaler},
    wayland::output::{Mode as OutputMode, Output, PhysicalProperties},
};

use std::{
    cell::RefCell,
    collections::{HashMap, HashSet},
    path::PathBuf,
    rc::Rc,
    time::{Duration, Instant, SystemTime},
};

mod drm_helpers;
mod session_fd;
mod socket;
use session_fd::*;
use socket::*;

pub struct KmsState {
    devices: HashMap<DrmNode, Device>,
    api: GpuManager<EglGlesBackend>,
    primary: DrmNode,
    session: AutoSession,
    signaler: Signaler<Signal>,
    tokens: Vec<RegistrationToken>,
}

pub struct Device {
    render_node: DrmNode,
    surfaces: HashMap<crtc::Handle, Surface>,
    allocator: Rc<RefCell<GbmDevice<SessionFd>>>,
    drm: Dispatcher<'static, DrmDevice<SessionFd>, State>,
    formats: HashSet<Format>,
    supports_atomic: bool,
    event_token: Option<RegistrationToken>,
    socket: Option<Socket>,
}

pub struct Surface {
    surface: GbmBufferedSurface<Rc<RefCell<GbmDevice<SessionFd>>>, SessionFd>,
    output: Output,
    _global: GlobalDrop<wl_output::WlOutput>,
    last_submit: Option<DrmEventTime>,
    refresh_rate: u32,
    vrr: bool,
    pending: bool,
    render_timer: TimerHandle<(DrmNode, crtc::Handle)>,
    render_timer_token: Option<RegistrationToken>,
    #[cfg(feature = "debug")]
    fps: Fps,
}

pub fn init_backend(event_loop: &mut EventLoop<State>, state: &mut State) -> Result<()> {
    let (session, notifier) = AutoSession::new(None).context("Failed to acquire session")?;
    let signaler = notifier.signaler();

    let udev_backend = UdevBackend::new(session.seat(), None)?;
    let mut libinput_context =
        Libinput::new_with_udev::<LibinputSessionInterface<AutoSession>>(session.clone().into());
    libinput_context
        .udev_assign_seat(&session.seat())
        .map_err(|_| anyhow::anyhow!("Failed to assign seat to libinput"))?;
    let mut libinput_backend = LibinputInputBackend::new(libinput_context, None);
    libinput_backend.link(signaler.clone());

    let libinput_event_source = event_loop
        .handle()
        .insert_source(libinput_backend, move |event, _, state| {
            state.common.process_input_event(event);
            for output in state.common.shell.outputs() {
                state.backend.kms().schedule_render(output);
            }
        })
        .map_err(|err| err.error)
        .context("Failed to initialize libinput event source")?;
    let session_event_source = event_loop
        .handle()
        .insert_source(notifier, |(), &mut (), _state| {})
        .map_err(|err| err.error)
        .context("Failed to initialize session event source")?;

    let api = GpuManager::new(EglGlesBackend, None).context("Failed to initialize renderers")?;

    // TODO get this info from system76-power, if available and setup a watcher
    let primary = if let Some(path) = std::env::var("COSMIC_RENDER_DEVICE")
        .ok()
        .and_then(|x| DrmNode::from_path(x).ok())
    {
        path
    } else {
        primary_gpu(session.seat())
            .ok()
            .flatten()
            .and_then(|x| DrmNode::from_path(x).ok())
            .and_then(|x| x.node_with_type(NodeType::Render).and_then(Result::ok))
            .unwrap_or_else(|| {
                for dev in all_gpus(session.seat()).expect("No GPU found") {
                    if let Some(node) = DrmNode::from_path(dev)
                        .ok()
                        .and_then(|x| x.node_with_type(NodeType::Render).and_then(Result::ok))
                    {
                        return node;
                    }
                }
                panic!("Failed to initialize any GPU");
            })
    };
    slog_scope::info!("Using {} as primary gpu for rendering", primary);

    state.backend = BackendData::Kms(KmsState {
        api,
        tokens: vec![libinput_event_source, session_event_source],
        primary,
        session,
        signaler,
        devices: HashMap::new(),
    });

    for (dev, path) in udev_backend.device_list() {
        state
            .device_added(dev, path.into())
            .with_context(|| format!("Failed to add drm device: {}", path.display()))?;
    }

    let udev_event_source = event_loop
        .handle()
        .insert_source(udev_backend, move |event, _, state| {
            match match event {
                UdevEvent::Added { device_id, path } => state
                    .device_added(device_id, path)
                    .with_context(|| format!("Failed to add drm device: {}", device_id)),
                UdevEvent::Changed { device_id } => state
                    .device_changed(device_id)
                    .with_context(|| format!("Failed to update drm device: {}", device_id)),
                UdevEvent::Removed { device_id } => state
                    .device_removed(device_id)
                    .with_context(|| format!("Failed to remove drm device: {}", device_id)),
            } {
                Ok(()) => {
                    slog_scope::debug!("Successfully handled udev event")
                }
                Err(err) => {
                    slog_scope::error!("Error while handling udev event: {}", err)
                }
            }
        })
        .unwrap();
    state.backend.kms().tokens.push(udev_event_source);

    Ok(())
}

impl State {
    fn device_added(&mut self, dev: dev_t, path: PathBuf) -> Result<()> {
        let fd = SessionFd::new(
            self.backend
                .kms()
                .session
                .open(
                    &path,
                    OFlag::O_RDWR | OFlag::O_CLOEXEC | OFlag::O_NOCTTY | OFlag::O_NONBLOCK,
                )
                .with_context(|| {
                    format!(
                        "Failed to optain file descriptor for drm device: {}",
                        path.display()
                    )
                })?,
        );
        let mut drm = DrmDevice::new(fd.clone(), false, None)
            .with_context(|| format!("Failed to initialize drm device for: {}", path.display()))?;
        let drm_node = DrmNode::from_dev_id(dev)?;
        let supports_atomic = drm.is_atomic();

        let gbm = GbmDevice::new(fd)
            .with_context(|| format!("Failed to initialize GBM device for {}", path.display()))?;
        let egl_display = EGLDisplay::new(&gbm, None).with_context(|| {
            format!("Failed to create EGLDisplay for device: {}", path.display())
        })?;
        let egl_device = EGLDevice::device_for_display(&egl_display).with_context(|| {
            format!("Unable to find matching egl device for {}", path.display())
        })?;
        let render_node = egl_device
            .try_get_render_node()
            .ok()
            .and_then(std::convert::identity)
            .with_context(|| {
                format!(
                    "Failed to determine path of egl device for {}",
                    path.display()
                )
            })?;
        let egl_context = EGLContext::new(&egl_display, None).with_context(|| {
            format!(
                "Failed to create EGLContext for device {:?}:{}",
                egl_device,
                path.display()
            )
        })?;
        let formats = egl_context.dmabuf_render_formats().clone();

        drm.link(self.backend.kms().signaler.clone());
        let dispatcher =
            Dispatcher::new(drm, move |event, metadata, state: &mut State| match event {
                DrmEvent::VBlank(crtc) => {
                    if let Some(device) = state.backend.kms().devices.get_mut(&drm_node) {
                        if let Some(surface) = device.surfaces.get_mut(&crtc) {
                            match surface.surface.frame_submitted() {
                                Ok(_) => {
                                    surface.last_submit = metadata.take().map(|data| data.time);
                                    surface.pending = false;
                                    state
                                        .common
                                        .shell
                                        .active_space_mut(&surface.output)
                                        .space
                                        .send_frames(
                                            state.common.start_time.elapsed().as_millis() as u32
                                        );
                                }
                                Err(err) => slog_scope::warn!("Failed to submit frame: {}", err),
                            };
                        }
                    }
                }
                DrmEvent::Error(err) => {
                    slog_scope::warn!("Failed to read events of device {:?}: {}", dev, err);
                }
            });
        let token = self
            .common
            .event_loop_handle
            .register_dispatcher(dispatcher.clone())
            .with_context(|| format!("Failed to add drm device to event loop: {}", dev))?;

        let socket = match self.create_socket(render_node, formats.clone().into_iter()) {
            Ok(socket) => Some(socket),
            Err(err) => {
                slog_scope::warn!(
                    "Failed to initialize hardware-acceleration for clients on {}: {}",
                    render_node,
                    err
                );
                None
            }
        };

        let mut device = Device {
            render_node,
            surfaces: HashMap::new(),
            allocator: Rc::new(RefCell::new(gbm)),
            drm: dispatcher,
            formats,
            supports_atomic,
            event_token: Some(token),
            socket,
        };

        let outputs = device.enumerate_surfaces()?.added; // There are no removed outputs on newly added devices
        for (crtc, conn) in outputs {
            match device.setup_surface(
                &drm_node,
                crtc,
                conn,
                self.backend.kms().signaler.clone(),
                &mut self.common.display.borrow_mut(),
                &mut self.common.event_loop_handle,
            ) {
                Ok(output) => self.common.shell.map_output(
                    &output,
                    &mut self.backend,
                    &mut self.common.config,
                ),
                Err(err) => slog_scope::warn!("Failed to initialize output: {}", err),
            };
        }

        self.backend.kms().devices.insert(drm_node, device);
        Ok(())
    }

    fn device_changed(&mut self, dev: dev_t) -> Result<()> {
        let drm_node = DrmNode::from_dev_id(dev)?;
        let signaler = self.backend.kms().signaler.clone();
        let mut outputs_removed = Vec::new();
        let mut outputs_added = Vec::new();
        if let Some(device) = self.backend.kms().devices.get_mut(&drm_node) {
            let changes = device.enumerate_surfaces()?;
            for crtc in changes.removed {
                if let Some(surface) = device.surfaces.get_mut(&crtc) {
                    if let Some(token) = surface.render_timer_token.take() {
                        self.common.event_loop_handle.remove(token);
                    }
                    outputs_removed.push(surface.output.clone());
                }
            }
            for (crtc, conn) in changes.added {
                match device.setup_surface(
                    &drm_node,
                    crtc,
                    conn,
                    signaler.clone(),
                    &mut self.common.display.borrow_mut(),
                    &mut self.common.event_loop_handle,
                ) {
                    Ok(output) => {
                        outputs_added.push(output);
                    }
                    Err(err) => slog_scope::warn!("Failed to initialize output: {}", err),
                };
            }
        }

        for output in outputs_removed.into_iter() {
            self.common
                .shell
                .unmap_output(&output, &mut self.backend, &self.common.config);
        }
        for output in outputs_added.into_iter() {
            self.common
                .shell
                .map_output(&output, &mut self.backend, &mut self.common.config)
        }
        Ok(())
    }

    fn device_removed(&mut self, dev: dev_t) -> Result<()> {
        let drm_node = DrmNode::from_dev_id(dev)?;
        let mut outputs_removed = Vec::new();
        if let Some(mut device) = self.backend.kms().devices.remove(&drm_node) {
            for surface in device.surfaces.values_mut() {
                if let Some(token) = surface.render_timer_token.take() {
                    self.common.event_loop_handle.remove(token);
                }
                outputs_removed.push(surface.output.clone());
            }
            if let Some(token) = device.event_token.take() {
                self.common.event_loop_handle.remove(token);
            }
            if let Some(socket) = device.socket.take() {
                self.common.event_loop_handle.remove(socket.token);
            }
        }
        for output in outputs_removed.into_iter() {
            self.common
                .shell
                .unmap_output(&output, &mut self.backend, &self.common.config);
        }

        Ok(())
    }
}

pub struct OutputChanges {
    pub added: Vec<(crtc::Handle, connector::Handle)>,
    pub removed: Vec<crtc::Handle>,
}

impl Device {
    pub fn enumerate_surfaces(&mut self) -> Result<OutputChanges> {
        let drm = &mut *self.drm.as_source_mut();

        // enumerate our outputs
        let config = drm_helpers::display_configuration(drm, self.supports_atomic)?;

        let surfaces = self
            .surfaces
            .iter()
            .map(|(c, s)| (*c, s.surface.current_connectors().into_iter().next()))
            .collect::<HashMap<crtc::Handle, Option<connector::Handle>>>();

        let added = config
            .iter()
            .filter(|(conn, crtc)| {
                surfaces
                    .get(&crtc)
                    .map(|c| c.as_ref() != Some(*conn))
                    .unwrap_or(true)
            })
            .map(|(conn, crtc)| (crtc, conn))
            .map(|(crtc, conn)| (*crtc, *conn))
            .collect::<Vec<_>>();
        let removed = surfaces
            .iter()
            .filter(|(crtc, conn)| {
                if let Some(conn) = conn {
                    config.get(conn).map(|c| c != *crtc).unwrap_or(true)
                } else {
                    true
                }
            })
            .map(|(crtc, _)| *crtc)
            .collect::<Vec<_>>();

        Ok(OutputChanges { added, removed })
    }

    fn setup_surface(
        &mut self,
        drm_node: &DrmNode,
        crtc: crtc::Handle,
        conn: connector::Handle,
        signaler: Signaler<Signal>,
        display: &mut Display,
        loop_handle: &mut LoopHandle<'static, State>,
    ) -> Result<Output> {
        let drm = &mut *self.drm.as_source_mut();
        let crtc_info = drm.get_crtc(crtc)?;
        let conn_info = drm.get_connector(conn)?;
        let vrr = drm_helpers::set_vrr(drm, crtc, conn, true).unwrap_or(false);
        let interface = drm_helpers::interface_name(drm, conn)?;
        let edid_info = drm_helpers::edid_info(drm, conn)?;
        let mode = crtc_info.mode().unwrap_or_else(||
            conn_info.modes().iter().find(|mode| mode.mode_type().contains(ModeTypeFlags::PREFERRED))
                .copied().unwrap_or(conn_info.modes()[0])
        );
        let refresh_rate = drm_helpers::calculate_refresh_rate(mode);
        let mut surface = drm.create_surface(crtc, mode, &[conn])?;
        surface.link(signaler);

        let target =
            GbmBufferedSurface::new(surface, self.allocator.clone(), self.formats.clone(), None)
                .with_context(|| format!("Failed to initialize Gbm surface for {}", interface))?;

        //let is_nvidia = driver(drm.device_id()).ok().flatten().map(|x| x == "nvidia").unwrap_or(false);
        let output_mode = OutputMode {
            size: (mode.size().0 as i32, mode.size().1 as i32).into(),
            refresh: refresh_rate as i32,
        };
        let (phys_w, phys_h) = conn_info.size().unwrap_or((0, 0));
        let (output, output_global) = Output::new(
            display,
            interface,
            PhysicalProperties {
                size: (phys_w as i32, phys_h as i32).into(),
                // TODO: We need to read that from the connector properties
                subpixel: wl_output::Subpixel::Unknown,
                make: edid_info.manufacturer,
                model: edid_info.model,
            },
            None,
        );
        output.set_preferred(output_mode.clone());
        output.change_current_state(
            Some(output_mode),
            // TODO: Readout property for monitor rotation
            Some(wl_output::Transform::Normal),
            None,
            None,
        );
        output.user_data().insert_if_missing(|| {
            RefCell::new(OutputConfig {
                mode: (
                    (output_mode.size.w, output_mode.size.h),
                    Some(format!("{}x{}@{}", mode.size().0, mode.size().1, refresh_rate)),
                ),
                vrr,
                ..Default::default()
            })
        });

        let timer = Timer::new()?;
        let timer_handle = timer.handle();
        // render timer
        let timer_token = loop_handle
            .insert_source(timer, |(dev_id, crtc), _, state| {
                let backend = state.backend.kms();
                if let Some(device) = backend.devices.get_mut(&dev_id) {
                    if let Some(surface) = device.surfaces.get_mut(&crtc) {
                        if let Err(err) = surface.render_output(
                            &mut backend.api,
                            &device.render_node,
                            &mut state.common,
                        ) {
                            slog_scope::error!("Error rendering: {}", err);
                            // TODO re-schedule?
                        }
                    }
                }
            })
            .unwrap();
        timer_handle.add_timeout(Duration::ZERO, (*drm_node, crtc));

        let data = Surface {
            output: output.clone(),
            _global: output_global.into(),
            surface: target,
            vrr,
            refresh_rate,
            last_submit: None,
            pending: true,
            render_timer: timer_handle,
            render_timer_token: Some(timer_token),
            #[cfg(feature = "debug")]
            fps: Fps::default(),
        };
        self.surfaces.insert(crtc, data);

        Ok(output)
    }
}

const MAX_CPU_COPIES: usize = 3;

impl Surface {
    pub fn render_output(
        &mut self,
        api: &mut GpuManager<EglGlesBackend>,
        target_node: &DrmNode,
        state: &mut Common,
    ) -> Result<()> {
        let nodes = state
            .shell
            .active_space(&self.output)
            .space
            .windows()
            .flat_map(|w| {
                w.toplevel()
                    .get_surface()?
                    .as_ref()
                    .client()?
                    .data_map()
                    .get::<DrmNode>()
                    .cloned()
            })
            .collect::<Vec<_>>();
        let render_node = if nodes.contains(&target_node) || nodes.len() < MAX_CPU_COPIES {
            &target_node
        } else {
            nodes
                .iter()
                .fold(HashMap::new(), |mut count_map, node| {
                    let count = count_map.entry(node).or_insert(0);
                    *count += 1;
                    count_map
                })
                .into_iter()
                .reduce(|a, b| if a.1 > b.1 { a } else { b })
                .map(|(node, _)| node)
                .unwrap_or(&target_node)
        };

        let mut renderer = api.renderer(render_node, &target_node).unwrap();

        let (buffer, age) = self
            .surface
            .next_buffer()
            .with_context(|| "Failed to allocate buffer")?;

        renderer
            .bind(buffer)
            .with_context(|| "Failed to bind buffer")?;

        match render::render_output(
            Some(&render_node),
            &mut renderer,
            age,
            state,
            &self.output,
            false,
            #[cfg(feature = "debug")]
            &mut self.fps,
        ) {
            Ok(_) => {
                self.surface
                    .queue_buffer()
                    .with_context(|| "Failed to submit buffer for display")?;
            }
            Err(err) => {
                self.surface.reset_buffers();
                anyhow::bail!("Rendering failed: {}", err);
            }
        };
        Ok(())
    }
}

impl KmsState {
    pub fn apply_config_for_output(
        &mut self,
        output: &Output,
    ) -> Result<(), Box<dyn std::error::Error>> {
        if let Some(device) = self
            .devices
            .values_mut()
            .find(|dev| dev.surfaces.values().any(|s| s.output == *output))
        {
            let mut surface = device
                .surfaces
                .values_mut()
                .find(|s| s.output == *output)
                .unwrap();
            let config = output
                .user_data()
                .get::<RefCell<OutputConfig>>()
                .unwrap()
                .borrow();

            let conn_info = device.drm.as_source_ref().get_connector(
                surface
                    .surface
                    .current_connectors()
                    .into_iter()
                    .next()
                    .unwrap_or_else(
                        || surface.surface
                        .pending_connectors()
                        .into_iter()
                        .next()
                        .unwrap()
                    ),
            )?;
            let mode = conn_info
                .modes()
                .iter()
                .find(|mode| {            
                    let refresh_rate = drm_helpers::calculate_refresh_rate(**mode);
                    format!("{}x{}@{}", mode.size().0, mode.size().1, refresh_rate)
                        == *config.mode.1.as_ref().unwrap()
                })
                .ok_or(anyhow::anyhow!("Unknown mode"))?;
            surface.surface.use_mode(*mode).unwrap();

            if config.vrr != surface.vrr {
                surface.vrr = drm_helpers::set_vrr(
                    &*device.drm.as_source_ref(),
                    surface.surface.crtc(),
                    conn_info.handle(),
                    config.vrr,
                )?;
            }
        }
        Ok(())
    }

    pub fn schedule_render(&mut self, output: &Output) {
        if let Some((device, surface)) = self
            .devices
            .iter_mut()
            .flat_map(|(node, d)| d.surfaces.values_mut().map(move |s| (node, s)))
            .find(|(_, s)| s.output == *output)
        {
            if !surface.pending {
                surface.pending = true;
                let duration = surface
                    .last_submit
                    .as_ref()
                    .and_then(|x| match x {
                        DrmEventTime::Monotonic(instant) => {
                            instant.checked_duration_since(Instant::now())
                        }
                        DrmEventTime::Realtime(time) => time.duration_since(SystemTime::now()).ok(),
                    })
                    .unwrap_or(Duration::ZERO); // + Duration::from_secs_f64((1.0 / surface.refresh_rate as f64) - 20.0);
                let data = (*device, surface.surface.crtc());
                if surface.vrr {
                    surface.render_timer.add_timeout(Duration::ZERO, data);
                } else {
                    surface.render_timer.add_timeout(duration, data);
                }
            }
        }
    }
}