#include <assert.h>
#include <errno.h>
#include <drm_fourcc.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <wayland-server-core.h>
#include <wlr/backend/interface.h>
#include <wlr/backend/session.h>
#include <wlr/interfaces/wlr_output.h>
#include <wlr/util/log.h>
#include <xf86drm.h>
#include "backend/drm/drm.h"
#include "backend/drm/fb.h"

struct wlr_drm_backend *get_drm_backend_from_backend(
		struct wlr_backend *wlr_backend) {
	assert(wlr_backend_is_drm(wlr_backend));
	struct wlr_drm_backend *backend = wl_container_of(wlr_backend, backend, backend);
	return backend;
}

static bool backend_start(struct wlr_backend *backend) {
	struct wlr_drm_backend *drm = get_drm_backend_from_backend(backend);
	scan_drm_connectors(drm, NULL);
	return true;
}

static void backend_destroy(struct wlr_backend *backend) {
	if (!backend) {
		return;
	}

	struct wlr_drm_backend *drm = get_drm_backend_from_backend(backend);

	struct wlr_drm_connector *conn, *next;
	wl_list_for_each_safe(conn, next, &drm->connectors, link) {
		conn->crtc = NULL; // leave CRTCs on when shutting down
		destroy_drm_connector(conn);
	}

	struct wlr_drm_page_flip *page_flip, *page_flip_tmp;
	wl_list_for_each_safe(page_flip, page_flip_tmp, &drm->page_flips, link) {
		drm_page_flip_destroy(page_flip);
	}

	wlr_backend_finish(backend);

	wl_list_remove(&drm->session_destroy.link);
	wl_list_remove(&drm->session_active.link);
	wl_list_remove(&drm->parent_destroy.link);
	wl_list_remove(&drm->dev_change.link);
	wl_list_remove(&drm->dev_remove.link);

	if (drm->parent) {
		finish_drm_renderer(&drm->mgpu_renderer);
	}

	finish_drm_resources(drm);

	struct wlr_drm_fb *fb, *fb_tmp;
	wl_list_for_each_safe(fb, fb_tmp, &drm->fbs, link) {
		drm_fb_destroy(fb);
	}

	free(drm->name);
	wlr_session_close_file(drm->session, drm->dev);
	wl_event_source_remove(drm->drm_event);
	free(drm);
}

static int backend_get_drm_fd(struct wlr_backend *backend) {
	struct wlr_drm_backend *drm = get_drm_backend_from_backend(backend);
	return drm->fd;
}

static uint32_t drm_backend_get_buffer_caps(struct wlr_backend *backend) {
	return WLR_BUFFER_CAP_DMABUF;
}

static const struct wlr_backend_impl backend_impl = {
	.start = backend_start,
	.destroy = backend_destroy,
	.get_drm_fd = backend_get_drm_fd,
	.get_buffer_caps = drm_backend_get_buffer_caps,
};

bool wlr_backend_is_drm(struct wlr_backend *b) {
	return b->impl == &backend_impl;
}

struct wlr_backend *wlr_drm_backend_get_parent(struct wlr_backend *backend) {
	struct wlr_drm_backend *drm = get_drm_backend_from_backend(backend);
	return drm->parent ? &drm->parent->backend : NULL;
}

static void build_current_connector_state(struct wlr_output_state *state,
		struct wlr_drm_connector *conn) {
	bool enabled = conn->status != DRM_MODE_DISCONNECTED && conn->output.enabled;

	wlr_output_state_init(state);
	wlr_output_state_set_enabled(state, enabled);
	if (!enabled) {
		return;
	}

	if (conn->output.current_mode != NULL) {
		wlr_output_state_set_mode(state, conn->output.current_mode);
	} else {
		wlr_output_state_set_custom_mode(state,
			conn->output.width, conn->output.height, conn->output.refresh);
	}
}

static void handle_session_active(struct wl_listener *listener, void *data) {
	struct wlr_drm_backend *drm =
		wl_container_of(listener, drm, session_active);
	struct wlr_session *session = drm->session;

	wlr_log(WLR_INFO, "DRM FD %s", session->active ? "resumed" : "paused");

	if (!session->active) {
		return;
	}

	scan_drm_connectors(drm, NULL);

	// The previous DRM master leaves KMS in an undefined state. We need
	// to restore out own state, but be careful to avoid invalid
	// configurations. The connector/CRTC mapping may have changed, so
	// first disable all CRTCs, then light up the ones we were using
	// before the VT switch.
	// TODO: use the atomic API to improve restoration after a VT switch
	for (size_t i = 0; i < drm->num_crtcs; i++) {
		struct wlr_drm_crtc *crtc = &drm->crtcs[i];

		if (drmModeSetCrtc(drm->fd, crtc->id, 0, 0, 0, NULL, 0, NULL) != 0) {
			wlr_log_errno(WLR_ERROR, "Failed to disable CRTC %"PRIu32" after VT switch",
				crtc->id);
		}
	}

	struct wlr_drm_connector *conn;
	wl_list_for_each(conn, &drm->connectors, link) {
		struct wlr_output_state state;
		build_current_connector_state(&state, conn);
		if (!drm_connector_commit_state(conn, &state)) {
			wlr_drm_conn_log(conn, WLR_ERROR, "Failed to restore state after VT switch");
		}
		wlr_output_state_finish(&state);
	}
}

static void handle_dev_change(struct wl_listener *listener, void *data) {
	struct wlr_drm_backend *drm = wl_container_of(listener, drm, dev_change);
	struct wlr_device_change_event *change = data;

	if (!drm->session->active) {
		return;
	}

	switch (change->type) {
	case WLR_DEVICE_HOTPLUG:
		wlr_log(WLR_DEBUG, "Received hotplug event for %s", drm->name);
		scan_drm_connectors(drm, &change->hotplug);
		break;
	case WLR_DEVICE_LEASE:
		wlr_log(WLR_DEBUG, "Received lease event for %s", drm->name);
		scan_drm_leases(drm);
		break;
	default:
		wlr_log(WLR_DEBUG, "Received unknown change event for %s", drm->name);
	}
}

static void handle_dev_remove(struct wl_listener *listener, void *data) {
	struct wlr_drm_backend *drm = wl_container_of(listener, drm, dev_remove);

	wlr_log(WLR_INFO, "Destroying DRM backend for %s", drm->name);
	backend_destroy(&drm->backend);
}

static void handle_session_destroy(struct wl_listener *listener, void *data) {
	struct wlr_drm_backend *drm =
		wl_container_of(listener, drm, session_destroy);
	backend_destroy(&drm->backend);
}

static void handle_parent_destroy(struct wl_listener *listener, void *data) {
	struct wlr_drm_backend *drm =
		wl_container_of(listener, drm, parent_destroy);
	backend_destroy(&drm->backend);
}

struct wlr_backend *wlr_drm_backend_create(struct wlr_session *session,
		struct wlr_device *dev, struct wlr_backend *parent) {
	assert(session && dev);
	assert(!parent || wlr_backend_is_drm(parent));

	char *name = drmGetDeviceNameFromFd2(dev->fd);
	drmVersion *version = drmGetVersion(dev->fd);
	wlr_log(WLR_INFO, "Initializing DRM backend for %s (%s)", name, version->name);
	drmFreeVersion(version);

	struct wlr_drm_backend *drm = calloc(1, sizeof(*drm));
	if (!drm) {
		wlr_log_errno(WLR_ERROR, "Allocation failed");
		return NULL;
	}
	wlr_backend_init(&drm->backend, &backend_impl);

	drm->session = session;
	wl_list_init(&drm->fbs);
	wl_list_init(&drm->connectors);
	wl_list_init(&drm->page_flips);

	drm->dev = dev;
	drm->fd = dev->fd;
	drm->name = name;

	if (parent != NULL) {
		drm->parent = get_drm_backend_from_backend(parent);

		drm->parent_destroy.notify = handle_parent_destroy;
		wl_signal_add(&parent->events.destroy, &drm->parent_destroy);
	} else {
		wl_list_init(&drm->parent_destroy.link);
	}

	drm->dev_change.notify = handle_dev_change;
	wl_signal_add(&dev->events.change, &drm->dev_change);

	drm->dev_remove.notify = handle_dev_remove;
	wl_signal_add(&dev->events.remove, &drm->dev_remove);

	drm->drm_event = wl_event_loop_add_fd(session->event_loop, drm->fd,
		WL_EVENT_READABLE, handle_drm_event, drm);
	if (!drm->drm_event) {
		wlr_log(WLR_ERROR, "Failed to create DRM event source");
		goto error_fd;
	}

	drm->session_active.notify = handle_session_active;
	wl_signal_add(&session->events.active, &drm->session_active);

	if (!check_drm_features(drm)) {
		goto error_event;
	}

	if (!init_drm_resources(drm)) {
		goto error_event;
	}

	if (drm->parent) {
		if (!init_drm_renderer(drm, &drm->mgpu_renderer)) {
			wlr_log(WLR_ERROR, "Failed to initialize renderer");
			goto error_resources;
		}

		// We'll perform a multi-GPU copy for all submitted buffers, we need
		// to be able to texture from them
		struct wlr_renderer *renderer = drm->mgpu_renderer.wlr_rend;
		const struct wlr_drm_format_set *texture_formats =
			wlr_renderer_get_dmabuf_texture_formats(renderer);
		if (texture_formats == NULL) {
			wlr_log(WLR_ERROR, "Failed to query renderer texture formats");
			goto error_mgpu_renderer;
		}

		// Forbid implicit modifiers, because their meaning changes from one
		// GPU to another.
		for (size_t i = 0; i < texture_formats->len; i++) {
			const struct wlr_drm_format *fmt = &texture_formats->formats[i];
			for (size_t j = 0; j < fmt->len; j++) {
				uint64_t mod = fmt->modifiers[j];
				if (mod == DRM_FORMAT_MOD_INVALID) {
					continue;
				}
				wlr_drm_format_set_add(&drm->mgpu_formats, fmt->format, mod);
			}
		}
	}

	drm->session_destroy.notify = handle_session_destroy;
	wl_signal_add(&session->events.destroy, &drm->session_destroy);

	return &drm->backend;

error_mgpu_renderer:
	finish_drm_renderer(&drm->mgpu_renderer);
error_resources:
	finish_drm_resources(drm);
error_event:
	wl_list_remove(&drm->session_active.link);
	wl_event_source_remove(drm->drm_event);
error_fd:
	wl_list_remove(&drm->dev_remove.link);
	wl_list_remove(&drm->dev_change.link);
	wl_list_remove(&drm->parent_destroy.link);
	wlr_session_close_file(drm->session, dev);
	free(drm);
	return NULL;
}