#define _GNU_SOURCE	/* for asprintf() */
#include <assert.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <xf86drm.h>
#include <xf86drmMode.h>

#include "fb.h"
#include "settings.h"
#include "util.h"

/* drm fb backend, everything drm-specific in rototiller resides here. */

typedef struct drm_fb_t {
	int			drm_fd;
	drmModeCrtc		*crtc;
	drmModeConnector	*connector;
	drmModeModeInfo		*mode;
} drm_fb_t;

typedef struct drm_fb_page_t drm_fb_page_t;

struct drm_fb_page_t {
	uint32_t		*mmap;
	size_t			mmap_size;
	uint32_t		drm_dumb_handle;
	uint32_t		drm_fb_id;
};

typedef struct drm_fb_setup_t {
	const char		*dev;
	const char		*connector;
	const char		*mode;
} drm_fb_setup_t;


static const char * connector_type_name(uint32_t type) {
	static const char *connector_types[] = {
		"Unknown",
		"VGA",
		"DVII",
		"DVID",
		"DVIA",
		"Composite",
		"SVIDEO",
		"LVDS",
		"Component",
		"SPinDIN",
		"DisplayPort",
		"HDMIA",
		"HDMIB",
		"TV",
		"eDP",
		"VIRTUAL",
		"DSI"
	};

	assert(type < nelems(connector_types));

	return connector_types[type];
}


static int dev_desc_generator(void *setup_context, setting_desc_t **res_desc)
{
	return  setting_desc_clone(&(setting_desc_t){
					.name = "DRM Device Path",
					.key = "dev",
					.regex = "/dev/dri/card[0-9]",
					.preferred = "/dev/dri/card0",
					.values = NULL,
					.annotations = NULL
				}, res_desc);
}


/* returns a NULL-terminated array of drm connectors */
static int get_connectors(const char *dev, char ***res_connectors)
{
	int		counts[64] = {};	/* assuming this is big enough */
	char		**connectors;
	drmModeRes	*res;
	int		fd;

	assert(dev);

	fd = open(dev, O_RDWR);
	if (fd == -1)
		return -errno;

	res = drmModeGetResources(fd);
	if (!res) {
		close(fd);

		return -errno;
	}

	connectors = calloc(res->count_connectors + 1, sizeof(*connectors));
	if (!connectors) {
		close(fd);

		return -ENOMEM;
	}

	for (int i = 0; i < res->count_connectors; i++) {
		drmModeConnector	*con;

		con = drmModeGetConnector(fd, res->connectors[i]);
		if (!con) {
			close(fd);

			return -errno;
		}

		counts[con->connector_type]++;
		asprintf(&connectors[i], "%s-%i", connector_type_name(con->connector_type), counts[con->connector_type]); /* TODO: errors */

		drmModeFreeConnector(con);
	}

	drmModeFreeResources(res);
	close(fd);

	*res_connectors = connectors;

	return 0;
}


static void free_strv(const char **strv)
{
	int	i;

	for (i = 0; strv[i]; i++)
		free((void *)strv[i]);

	free((void *)strv);
}


static int connector_desc_generator(void *setup_context, setting_desc_t **res_desc)
{
	drm_fb_setup_t	*s = setup_context;
	const char	**connectors;
	int		r;

	assert(s);

	r = get_connectors(s->dev, (char ***)&connectors);
	if (r < 0)
		return r;

	r = setting_desc_clone(&(setting_desc_t){
					.name = "DRM Connector",
					.key = "connector",
					.regex = "[a-zA-Z0-9]+",
					.preferred = connectors[0],
					.values = connectors,
					.annotations = NULL
				}, res_desc);
	free_strv(connectors);

	return r;
}


static int lookup_connector(int fd, const char *connector, drmModeConnector **res_connector)
{
	int			r = -ENOENT, counts[64] = {};	/* assuming this is big enough */
	drmModeConnector	*con = NULL;
	drmModeRes		*res;

	res = drmModeGetResources(fd);
	if (!res)
		return -errno;

	for (int i = 0; i < res->count_connectors; i++) {
		char	*str;

		con = drmModeGetConnector(fd, res->connectors[i]);
		if (!con) {
			r = -errno;
			goto _out_res;
		}

		counts[con->connector_type]++;
		asprintf(&str, "%s-%i", connector_type_name(con->connector_type), counts[con->connector_type]); /* TODO: errors */

		if (!strcasecmp(str, connector)) {
			free(str);

			break;
		}

		free(str);
		drmModeFreeConnector(con);
		con = NULL;
	}

_out_res:
	drmModeFreeResources(res);

	if (!con)
		return r;

	*res_connector = con;

	return 0;
}


/* returns a NULL-terminated array of drm modes for the supplied device and connector */
static int get_modes(const char *dev, const char *connector, const char ***res_modes)
{
	char			**modes = NULL;
	int			fd, r = 0;
	drmModeConnector	*con;

	assert(dev);
	assert(connector);

	fd = open(dev, O_RDWR);
	if (fd == -1)
		return -errno;

	r = lookup_connector(fd, connector, &con);
	if (r < 0)
		goto _out_fd;

	modes = calloc(con->count_modes + 1, sizeof(*modes));
	if (!modes) {
		r = -ENOMEM;
		goto _out_con;
	}

	for (int i = 0; i < con->count_modes; i++)
		asprintf(&modes[i], "%s@%"PRIu32, con->modes[i].name, con->modes[i].vrefresh);

	*res_modes = (const char **)modes;

_out_con:
	drmModeFreeConnector(con);
_out_fd:
	close(fd);
_out:
	return r;
}


static int mode_desc_generator(void *setup_context, setting_desc_t **res_desc)
{
	drm_fb_setup_t	*s = setup_context;
	const char	**modes;
	int		r;

	assert(s);

	r = get_modes(s->dev, s->connector, &modes);
	if (r < 0)
		return r;

	r = setting_desc_clone(&(setting_desc_t){
					.name = "DRM Video Mode",
					.key = "mode",
					.regex = "[0-9]+[xX][0-9]+@[0-9]+",
					.preferred = modes[0],
					.values = modes,
					.annotations = NULL
				}, res_desc);
	free_strv(modes);

	return r;
}


/* setup is called repeatedly as settings is constructed, until 0 is returned. */
/* a negative value is returned on error */
/* positive value indicates another setting is needed, described in next_setting */
static int drm_fb_setup(const settings_t *settings, setting_desc_t **next_setting)
{
	drm_fb_setup_t			context = {};
	setting_desc_generator_t	generators[] = {
						{
							.key = "dev",
							.value_ptr = &context.dev,
							.func = dev_desc_generator
						}, {
							.key = "connector",
							.value_ptr = &context.connector,
							.func = connector_desc_generator
						}, {
							.key = "mode",
							.value_ptr = &context.mode,
							.func = mode_desc_generator
						},
					};

	if (!drmAvailable())
		return -ENOSYS;

	return settings_apply_desc_generators(settings, generators, nelems(generators), &context, next_setting);
}


/* lookup a mode string in the given connector returning its respective modeinfo */
static drmModeModeInfo * lookup_mode(drmModeConnector *connector, const char *mode)
{
	int	i;

	assert(connector);
	assert(mode);

	for (i = 0; i < connector->count_modes; i++) {
		char	*str;

		asprintf(&str, "%s@%"PRIu32, connector->modes[i].name, connector->modes[i].vrefresh);
		if (!strcasecmp(str, mode)) {
			free(str);

			return &connector->modes[i];
		}

		free(str);
	}

	return NULL;
}


/* prepare the drm context for use with the supplied settings */
static int drm_fb_init(const settings_t *settings, void **res_context)
{
	drm_fb_t	*c;
	const char	*dev;
	const char	*connector;
	const char	*mode;
	drmModeEncoder	*enc;
	int		r;

	assert(settings);

	if (!drmAvailable()) {
		r = -errno;
		goto _err;
	}

	dev = settings_get_value(settings, "dev");
	if (!dev) {
		r = -EINVAL;
		goto _err;
	}

	connector = settings_get_value(settings, "connector");
	if (!connector) {
		r = -EINVAL;
		goto _err;
	}

	mode = settings_get_value(settings, "mode");
	if (!mode) {
		r = -EINVAL;
		goto _err;
	}

	c = calloc(1, sizeof(drm_fb_t));
	if (!c) {
		r = -ENOMEM;
		goto _err;
	}

	c->drm_fd = open(dev, O_RDWR);
	if (c->drm_fd < 0) {
		r = -errno;
		goto _err_ctxt;
	}

	r = lookup_connector(c->drm_fd, connector, &c->connector);
	if (r < 0)
		goto _err_fd;

	c->mode = lookup_mode(c->connector, mode);
	if (!c->mode) {
		r = -EINVAL;
		goto _err_con;
	}

	enc = drmModeGetEncoder(c->drm_fd, c->connector->encoder_id);
	if (!enc) {
		r = -errno;
		goto _err_con;
	}

	c->crtc = drmModeGetCrtc(c->drm_fd, enc->crtc_id);
	if (!c->crtc) {
		r = -errno;
		goto _err_enc;
	}

	drmModeFreeEncoder(enc);

	*res_context = c;

	return 0;

_err_enc:
	drmModeFreeEncoder(enc);
_err_con:
	drmModeFreeConnector(c->connector);
_err_fd:
	close(c->drm_fd);
_err_ctxt:
	free(c);
_err:
	return r;
}


static void drm_fb_shutdown(fb_t *fb, void *context)
{
	drm_fb_t	*c = context;

	assert(c);

	close(c->drm_fd);
	drmModeFreeConnector(c->connector);
	drmModeFreeCrtc(c->crtc);
	free(c);
}


static int drm_fb_acquire(fb_t *fb, void *context, void *page)
{
	drm_fb_t	*c = context;
	drm_fb_page_t	*p = page;

	return drmModeSetCrtc(c->drm_fd, c->crtc->crtc_id, p->drm_fb_id, 0, 0, &c->connector->connector_id, 1, c->mode);
}


static void drm_fb_release(fb_t *fb, void *context)
{
	/* TODO restore the existing mode @ last acquire? */
}


static void * drm_fb_page_alloc(fb_t *fb, void *context, fb_page_t *res_page)
{
	struct drm_mode_create_dumb	create_dumb = { .bpp = 32 };
	struct drm_mode_map_dumb	map_dumb = {};
	uint32_t			*map, fb_id;
	drm_fb_t			*c = context;
	drm_fb_page_t			*p;

	p = calloc(1, sizeof(drm_fb_page_t));
	if (!p)
		return NULL;

	create_dumb.width = c->mode->hdisplay;
	create_dumb.height = c->mode->vdisplay;

	pexit_if(ioctl(c->drm_fd, DRM_IOCTL_MODE_CREATE_DUMB, &create_dumb) < 0,
		"unable to create dumb buffer");

	map_dumb.handle = create_dumb.handle;
	pexit_if(ioctl(c->drm_fd, DRM_IOCTL_MODE_MAP_DUMB, &map_dumb) < 0,
		"unable to prepare dumb buffer for mmap");
	pexit_if(!(map = mmap(NULL, create_dumb.size, PROT_READ|PROT_WRITE, MAP_SHARED, c->drm_fd, map_dumb.offset)),
		"unable to mmap dumb buffer");
	pexit_if(drmModeAddFB(c->drm_fd, c->mode->hdisplay, c->mode->vdisplay, 24, 32, create_dumb.pitch, create_dumb.handle, &fb_id) < 0,
		"unable to add dumb buffer");

	p->mmap = map;
	p->mmap_size = create_dumb.size;
	p->drm_dumb_handle = map_dumb.handle;
	p->drm_fb_id = fb_id;

	res_page->fragment.buf = map;
	res_page->fragment.width = c->mode->hdisplay;
	res_page->fragment.frame_width = c->mode->hdisplay;
	res_page->fragment.height = c->mode->vdisplay;
	res_page->fragment.frame_height = c->mode->vdisplay;
	res_page->fragment.stride = create_dumb.pitch - (c->mode->hdisplay * 4);
	res_page->fragment.pitch = create_dumb.pitch;

	return p;
}


static int drm_fb_page_free(fb_t *fb, void *context, void *page)
{
	struct drm_mode_destroy_dumb	destroy_dumb = {};
	drm_fb_t			*c = context;
	drm_fb_page_t			*p = page;

	drmModeRmFB(c->drm_fd, p->drm_fb_id);
	munmap(p->mmap, p->mmap_size);

	destroy_dumb.handle = p->drm_dumb_handle;
	ioctl(c->drm_fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroy_dumb); // XXX: errors?

	free(p);

	return 0;
}


static int drm_fb_page_flip(fb_t *fb, void *context, void *page)
{
	drmEventContext	drm_ev_ctx = {
				.version = DRM_EVENT_CONTEXT_VERSION,
				.vblank_handler = NULL,
				.page_flip_handler = NULL
			};
	drm_fb_t	*c = context;
	drm_fb_page_t	*p = page;

	if (drmModePageFlip(c->drm_fd, c->crtc->crtc_id, p->drm_fb_id, DRM_MODE_PAGE_FLIP_EVENT, NULL) < 0)
		return -1;

	return drmHandleEvent(c->drm_fd, &drm_ev_ctx);
}


fb_ops_t drm_fb_ops = {
	.setup = drm_fb_setup,
	.init = drm_fb_init,
	.shutdown = drm_fb_shutdown,
	.acquire = drm_fb_acquire,
	.release = drm_fb_release,
	.page_alloc = drm_fb_page_alloc,
	.page_free = drm_fb_page_free,
	.page_flip = drm_fb_page_flip
};