/*
 * Copyright © 2018 Keith Packard
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#define _GNU_SOURCE
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <limits.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <getopt.h>
#include <xcb/randr.h>

const char *default_x_server[] = {
	"X",
	"-seat",
	"seat1",
	":1",
	NULL
};

#define DEFAULT_FD_ARG		"-masterfd"

/* Lease an output from X and start an X server running on it */

/* Information about one lease */
typedef struct {
	int fd;

	/* X resources */
	xcb_randr_output_t randr_output;
	xcb_randr_crtc_t randr_crtc;
	xcb_randr_lease_t randr_lease;
	xcb_randr_mode_info_t randr_mode;

} lease_t;

/* Global information */
typedef struct {
	char *display;
	char *output_name;
	char **xserver;
	char *fd_arg;
	char *shell;
	int verbose;
	xcb_connection_t *conn;
	xcb_window_t root;
	xcb_timestamp_t config_timestamp;
	uint8_t event_base;
	uint8_t error_base;
	xcb_randr_get_screen_resources_reply_t *gsr_r;
} app_t;

/*
 * Create a lease for the desired output, select a crtc if none was
 * provided.
 */
static int
make_randr_lease(app_t *app, lease_t *lease, xcb_randr_output_t output, xcb_randr_crtc_t crtc, bool whinge, xcb_generic_error_t **error)
{
	/* Pick a crtc if none was provided */
	if (crtc == XCB_NONE) {
		xcb_randr_crtc_t    *rc = xcb_randr_get_screen_resources_crtcs(app->gsr_r);

		xcb_randr_crtc_t    idle_crtc = XCB_NONE;
		xcb_randr_crtc_t    active_crtc = XCB_NONE;

		/* Find either a crtc already connected to the desired output or idle */
		for (int c = 0; active_crtc == XCB_NONE && c < app->gsr_r->num_crtcs; c++) {
			xcb_randr_get_crtc_info_cookie_t gci_c = xcb_randr_get_crtc_info(app->conn, rc[c], app->gsr_r->config_timestamp);

			xcb_randr_get_crtc_info_reply_t *gci_r = xcb_randr_get_crtc_info_reply(app->conn, gci_c, NULL);

			if (gci_r->mode) {
				int num_outputs = xcb_randr_get_crtc_info_outputs_length(gci_r);
				xcb_randr_output_t *outputs = xcb_randr_get_crtc_info_outputs(gci_r);
				for (int o = 0; o < num_outputs; o++)
					if (outputs[o] == output && num_outputs == 1) {
						active_crtc = rc[c];
						break;
					}

			} else if (idle_crtc == 0) {
				int num_possible = xcb_randr_get_crtc_info_possible_length(gci_r);
				xcb_randr_output_t *possible = xcb_randr_get_crtc_info_possible(gci_r);
				for (int p = 0; p < num_possible; p++)
					if (possible[p] == output) {
						idle_crtc = rc[c];
						break;
					}
			}

			free(gci_r);
		}
		if (active_crtc)
			crtc = active_crtc;
		else
			crtc = idle_crtc;

	}

	if (crtc == XCB_NONE) {
		if (whinge)
			printf("\t\tcannot find usable CRTC\n");
		return 0;
	}

	/*
	 * Create a RandR lease
	 */

	xcb_randr_lease_t                   randr_lease = xcb_generate_id(app->conn);

	xcb_randr_create_lease_cookie_t     cl_c = xcb_randr_create_lease(app->conn,
									  app->root,
									  randr_lease,
									  1,
									  1,
									  &crtc,
									  &output);
	xcb_randr_create_lease_reply_t      *cl_r = xcb_randr_create_lease_reply(app->conn, cl_c, error);
	if (!cl_r) {
		if (whinge)
			printf ("create lease failed\n");
		return 0;
	}

	int fd = -1;
	if (cl_r->nfd > 0) {
		int *rcl_f = xcb_randr_create_lease_reply_fds(app->conn, cl_r);

		fd = rcl_f[0];
	}
	free (cl_r);
	if (fd < 0) {
		if (whinge)
			printf("\t\tLease returned invalid fd\n");
		return 0;
	}

	lease->fd = fd;
	lease->randr_output = output;
	lease->randr_crtc = crtc;
	lease->randr_lease = randr_lease;

	return 1;
}

static void
init_lease(lease_t *lease)
{
	memset(lease, 0, sizeof (*lease));
	lease->fd = -1;
}

static void
init_app(app_t *app)
{
	memset(app, 0, sizeof (*app));
}

static int
make_lease(app_t *app, lease_t *lease, xcb_randr_output_t output)
{
	init_lease(lease);

	if (!make_randr_lease(app, lease, output, XCB_NONE, true, NULL))
		return 0;

	return 1;
}

#if 0
static void
free_randr_lease(app_t *app, lease_t *lease)
{
	if (lease->randr_lease) {
		xcb_randr_free_lease(app->conn, lease->randr_lease, 0);
		free(xcb_get_input_focus_reply(app->conn, xcb_get_input_focus(app->conn), NULL));
		lease->randr_lease = 0;
	}
}

static void
close_kernel_lease(app_t *app, lease_t *lease)
{
	if (lease->fd >= 0) {
		close(lease->fd);
		lease->fd = -1;
	}
}

static void
close_lease(app_t *app, lease_t *lease)
{
	close_kernel_lease(app, lease);
	free_randr_lease(app, lease);
}
#endif

static void
describe_error(app_t *app, xcb_generic_error_t *error)
{
	if (error->error_code <= XCB_IMPLEMENTATION) {
		fprintf(stderr, "Core error %d\n", error->error_code);
	} else {
		switch (error->error_code - app->error_base) {
		case XCB_RANDR_BAD_OUTPUT:
			fprintf(stderr, "bad output\n"); break;
		case XCB_RANDR_BAD_CRTC:
			fprintf(stderr, "bad crtc\n"); break;
		case XCB_RANDR_BAD_MODE:
			fprintf(stderr, "bad mode\n"); break;
		case XCB_RANDR_BAD_PROVIDER:
			fprintf(stderr, "bad provider\n"); break;
		default:
			fprintf(stderr, "error code %d\n", error->error_code);
		}
	}
}

static int
app_setup(app_t *app)
{
	int screen;

	app->conn = xcb_connect(app->display, &screen);

	if (!app->conn) {
		fprintf(stderr, "Cannot connect to X server\n");
		return 0;
	}

	const xcb_setup_t                    *setup = xcb_get_setup(app->conn);

	/*
	 * Find our root window
	 */
	xcb_screen_iterator_t iter;
	for (iter = xcb_setup_roots_iterator(setup); iter.rem; xcb_screen_next(&iter)) {
		if (screen == 0) {
			app->root = iter.data->root;
			break;
		}
		--screen;
	}

	const xcb_query_extension_reply_t     *qer = xcb_get_extension_data(app->conn, &xcb_randr_id);

	if (!qer) {
		fprintf(stderr, "Cannot get randr extension data\n");
		xcb_disconnect(app->conn);
		return 0;
	}

	app->error_base = qer->first_error;
	app->event_base = qer->first_event;

	return 1;
}

static int
app_get_randr_resources(app_t *app)
{
    if (app->gsr_r) {
        free(app->gsr_r);
        app->gsr_r = NULL;
    }

    xcb_randr_get_screen_resources_cookie_t gsr_c = xcb_randr_get_screen_resources(app->conn, app->root);

    xcb_generic_error_t *error;

    app->gsr_r = xcb_randr_get_screen_resources_reply(app->conn, gsr_c, &error);

    if (!app->gsr_r) {
        printf("\t\tget_screen_resources failed\n");
        if (error)
            describe_error(app, error);
        return 0;
    }

    app->config_timestamp = app->gsr_r->config_timestamp;

    return 1;
}

#if 0
static void
app_fini(app_t *app)
{
    free(app->gsr_r);
    app->gsr_r = NULL;

    xcb_disconnect(app->conn);
    app->conn = NULL;
}
#endif

static const struct option options[] = {
	{ .name = "display", .has_arg = 1, .val = 'd' },
	{ .name = "output", .has_arg = 1, .val = 'o' },
	{ .name = "fd-arg", .has_arg = 1, .val = 'f' },
	{ .name = "help", .has_arg = 0, .val = '?' },
	{ .name = "verbose", .has_arg = 0, .val = 'v' },
	{ 0 },
};

static void usage(char *program, int code)
{
	fprintf(stderr, "usage: %s [--display=<display>] [--output=<output>] [--fd-arg=<--name>] [--verbose] [--help] {command args ...}\n", program);
	exit(code);
}

int main (int argc, char **argv)
{
	app_t app;
	int c;

	init_app(&app);

	app.xserver = (char **) default_x_server;
	app.fd_arg = (char *) DEFAULT_FD_ARG;

	while ((c = getopt_long(argc, argv, "?vo:d:f:", options, NULL)) != -1) {
		switch (c) {
		case 'v':
			app.verbose++;
			break;
		case 'd':
			app.display = optarg;
			break;
		case 'o':
			app.output_name = optarg;
			break;
		case 'f':
			app.fd_arg = optarg;
			break;
		case '?':
			usage(argv[0], 0);
			break;
		default:
			usage(argv[0], 1);
			break;
		}
	}

	if (optind < argc)
		app.xserver = &argv[optind];

	if (!app.output_name) {
		fprintf(stderr, "No output specified\n");
		exit(1);
	}

        if (!app_setup(&app))
		exit(1);

	if (!app_get_randr_resources(&app))
                exit(1);

	xcb_randr_output_t	*ro = xcb_randr_get_screen_resources_outputs(app.gsr_r);
	int			num_outputs = app.gsr_r->num_outputs;

	int			o;

	xcb_randr_output_t	output = XCB_NONE;

	for (o = 0; o < num_outputs; o++) {

		xcb_randr_get_output_info_cookie_t  goi_c = xcb_randr_get_output_info(app.conn, ro[o], app.config_timestamp);

		xcb_randr_get_output_info_reply_t   *goi_r = xcb_randr_get_output_info_reply(app.conn, goi_c, NULL);

		uint8_t                             *output_name = xcb_randr_get_output_info_name(goi_r);
		int                                 output_name_length = xcb_randr_get_output_info_name_length(goi_r);

		if (output_name_length == strlen(app.output_name) &&
		    memcmp(output_name, app.output_name, output_name_length) == 0)
		{
			output = ro[o];
			break;
		}
	}

	if (!output) {
		fprintf(stderr, "%s: no such output\n", app.output_name);
		exit(1);
	}

	lease_t	lease;

	init_lease(&lease);

	if (!make_lease(&app, &lease, output)) {
		fprintf(stderr, "%s: lease create failed\n", app.output_name);
		exit(1);
	}

	xcb_disconnect(app.conn);

	char *fd_string;

	if (asprintf(&fd_string, "%d", lease.fd) <= 0) {
		perror("asprintf");
		exit(1);
	}

	int xserver_argc = 0;
	for (xserver_argc = 0; app.xserver[xserver_argc]; xserver_argc++);

	char **xserver = calloc((xserver_argc + 5), sizeof (char *));
	if (!xserver) {
		perror("calloc");
		exit(1);
	}

	memcpy(xserver, app.xserver, xserver_argc * sizeof (char *));
	xserver[xserver_argc++] = app.fd_arg;
	xserver[xserver_argc++] = fd_string;
	xserver[xserver_argc++] = NULL;

	if (execvp(xserver[0], xserver)) {
		perror(xserver[0]);
		exit(1);
	}

	exit(0);
}