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

#include "disp.h"

static void *
load_generic_symbol(struct disp *disp, char *base_name)
{
	char full_name[64] = {0};
	void *ptr;

	strcpy(full_name, disp->name);
	strcat(full_name, "_");
	strcat(full_name, base_name);

	ptr = dlsym(disp->dl_handle, full_name);

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

	return ptr;
}

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

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

	disp->dl_handle	   = handle;
	disp->init	   = load_generic_symbol(disp, "init");
	disp->display_calc = load_generic_symbol(disp, "display_calc");
	disp->read_input   = load_generic_symbol(disp, "read_input");
	disp->display_res  = load_generic_symbol(disp, "display_res");
	disp->destroy	   = load_generic_symbol(disp, "destroy");
	disp->pre_reload   = load_generic_symbol(disp, "pre_reload");
	disp->post_reload  = load_generic_symbol(disp, "post_reload");

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

struct disp *
get_disp(char *disp_name)
{
	/* displays are shared libraries */
	char so_path[128];
	strcpy(so_path, CALCULER_PREFIX);
	strcat(so_path, "/lib/calculer/lib");
	strcat(so_path, disp_name);
	strcat(so_path, ".so");
	struct disp *disp = malloc(sizeof(*disp));
	disp->so_path = strdup(so_path);
	disp->name = disp_name;

	load_symbols(disp);

	return disp;
}

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

void
disp_reload(struct disp *disp)
{
	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");
	load_symbols(disp);

	printf("INFO: loading state\n");
	disp->post_reload(state);

	printf("INFO: reloading done\n");
}