// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0

use drm::control::Device;
use gbm::AsRaw;
use i_slint_core::platform::PlatformError;

use crate::drmoutput::{DrmOutput, SharedFd};

struct OwnedFramebufferHandle {
    handle: drm::control::framebuffer::Handle,
    device: SharedFd,
}

impl Drop for OwnedFramebufferHandle {
    fn drop(&mut self) {
        self.device.destroy_framebuffer(self.handle).ok();
    }
}

pub struct GbmDisplay {
    pub drm_output: DrmOutput,
    gbm_surface: gbm::Surface<OwnedFramebufferHandle>,
    gbm_device: gbm::Device<SharedFd>,
    surface_format: drm::buffer::DrmFourcc,
}

impl GbmDisplay {
    pub fn new(drm_output: DrmOutput) -> Result<GbmDisplay, PlatformError> {
        //eprintln!("mode {}/{}", width, height);

        let gbm_device = gbm::Device::new(drm_output.drm_device.clone())
            .map_err(|e| format!("Error creating gbm device: {e}"))?;

        let surface_format = gbm::Format::Xrgb8888;

        let (width, height) = drm_output.size();
        let gbm_surface = gbm_device
            .create_surface::<OwnedFramebufferHandle>(
                width,
                height,
                surface_format,
                gbm::BufferObjectFlags::SCANOUT | gbm::BufferObjectFlags::RENDERING,
            )
            .map_err(|e| format!("Error creating gbm surface: {e}"))?;

        Ok(GbmDisplay { drm_output, gbm_surface, gbm_device, surface_format })
    }

    pub fn config_template_builder(&self) -> glutin::config::ConfigTemplateBuilder {
        let mut config_template_builder = glutin::config::ConfigTemplateBuilder::new();

        // Some drivers (like mali) report BAD_MATCH when trying to create a window surface for an xrgb backed
        // gbm surface with an EGL config that has an alpha size of 8. Disable alpha explicitly to accommodate.
        if matches!(self.surface_format, drm::buffer::DrmFourcc::Xrgb8888) {
            config_template_builder =
                config_template_builder.with_transparency(false).with_alpha_size(0);
        }

        config_template_builder
    }

    pub fn filter_gl_config(&self, config: &glutin::config::Config) -> bool {
        match &config {
            glutin::config::Config::Egl(egl_config) => {
                drm::buffer::DrmFourcc::try_from(egl_config.native_visual())
                    .map_or(false, |egl_config_fourcc| egl_config_fourcc == self.surface_format)
            }
            _ => false,
        }
    }
}

impl super::Presenter for GbmDisplay {
    fn present(&self) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        let mut front_buffer = unsafe {
            self.gbm_surface
                .lock_front_buffer()
                .map_err(|err| format!("Could not lock gbm front buffer: {err}"))?
        };

        // Same logic as in drm-rs' `add_planar_framebuffer` function.
        let flags = if drm::buffer::PlanarBuffer::modifier(&front_buffer)
            .filter(|modifier| !matches!(modifier, drm::buffer::DrmModifier::Invalid))
            .is_some()
        {
            drm::control::FbCmd2Flags::MODIFIERS
        } else {
            drm::control::FbCmd2Flags::empty()
        };

        let fb = self
            .drm_output
            .drm_device
            .add_planar_framebuffer(&front_buffer, flags)
            .map_err(|e| format!("Error adding gbm buffer as framebuffer: {e}"))?;

        front_buffer.set_userdata(OwnedFramebufferHandle {
            handle: fb,
            device: self.drm_output.drm_device.clone(),
        });

        self.drm_output.present(front_buffer, fb)
    }
}

impl raw_window_handle::HasWindowHandle for GbmDisplay {
    fn window_handle(
        &self,
    ) -> Result<raw_window_handle::WindowHandle<'_>, raw_window_handle::HandleError> {
        Ok(unsafe {
            let gbm_surface_handle = raw_window_handle::GbmWindowHandle::new(
                std::ptr::NonNull::from(&*self.gbm_surface.as_raw()).cast(),
            );

            raw_window_handle::WindowHandle::borrow_raw(raw_window_handle::RawWindowHandle::Gbm(
                gbm_surface_handle,
            ))
        })
    }
}

impl raw_window_handle::HasDisplayHandle for GbmDisplay {
    fn display_handle(
        &self,
    ) -> Result<raw_window_handle::DisplayHandle<'_>, raw_window_handle::HandleError> {
        Ok(unsafe {
            let gbm_display_handle = raw_window_handle::GbmDisplayHandle::new(
                std::ptr::NonNull::from(&*self.gbm_device.as_raw()).cast(),
            );

            raw_window_handle::DisplayHandle::borrow_raw(raw_window_handle::RawDisplayHandle::Gbm(
                gbm_display_handle,
            ))
        })
    }
}