/*
 * Copyright (C) 2024  Tristan Riehs
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "config.h"

#include <dlfcn.h>
#include <limits.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

#include "disp.h"

#define dlsym_and_check(dest, name)				\
	dest->name = dlsym(dest->dl_handle, #name);		\
	if ((!dest->name) || (dest->name == dest->dl_handle)) {	\
		char *msg = dlerror();				\
		fprintf(stderr, "calculer: %s\n", msg);		\
		dlclose(dest->dl_handle);			\
		free(dest);					\
		return -1;					\
	}

static int
load_symbols(struct disp *disp)
{
	void *handle = dlopen(disp->so_path, RTLD_LAZY);

	if (!handle)
	{
		fprintf(stderr, "calculer: %s\n", dlerror());
		exit(1);
	}

#ifndef NDEBUG
	printf("INFO: successfully loaded symbols from \"%s\"\n", disp->so_path);
#endif

	disp->dl_handle = handle;
	dlsym_and_check(disp, init);
	dlsym_and_check(disp, display_calc);
	dlsym_and_check(disp, read_input);
	dlsym_and_check(disp, display_res);
	dlsym_and_check(disp, destroy);
#ifndef NDEBUG
	dlsym_and_check(disp, pre_reload);
	dlsym_and_check(disp, post_reload);
#endif
	return 0;
}

struct disp *
get_disp(char *disp_name)
{
#ifndef NDEBUG
	/* displays are shared libraries */
	char so_path[64] = {0};
	strcpy(so_path, "./src/.libs/");
	strcat(so_path, disp_name);
	strcat(so_path, ".so.0.0.0");
	struct disp *disp = malloc(sizeof(*disp));
	disp->so_path = strdup(so_path);

	return load_symbols(disp) == 0 ? disp : NULL;
#else
#  error "not available yet"
#endif
	return NULL;
}

void
destroy_disp(struct disp *disp)
{
	disp->destroy();
	dlclose(disp->dl_handle);
	free(disp->so_path);
	free(disp);
}

#ifndef NDEBUG
void
disp_reload(struct disp *disp)
{
	int status;
	printf("INFO: saving state\n");
	void *state = disp->pre_reload();
	printf("INFO: closing shared library\n");
	dlclose(disp->dl_handle);
	printf("INFO: reloading symbols\n");
	status = load_symbols(disp);

	if (status == -1)
	{
		printf("calculer: %s\n", dlerror());
		exit(1);
	}

	printf("INFO: loading state\n");
	disp->post_reload(state);
	printf("INFO: reloading done\n");
}
#endif