/*
 *  Error handling for libcdecl.
 *  Copyright © 2011-2012, 2021, 2023-2024 Nick Bowler
 *
 *  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 <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>

#include "cdecl.h"
#include "cdecl-internal.h"
#include "errmsg.h"

/* This pre-initialized error is reserved for dire out-of-memory conditions. */
static struct cdecl_error err_no_mem;

static void set_err(unsigned code, struct cdecl_error *err)
{
	static const char _Alignas(1) errmsgs[] = STRTAB_INITIALIZER;

	switch (code) {
	case CDECL__ENOMEM:
		err->code = CDECL_ENOMEM;
		break;
	default:
		err->code = CDECL_ENOPARSE;
		break;
	}

	err->str = _(&errmsgs[code]);
}

static void init_once_cb(void)
{
#if ENABLE_NLS
	bindtextdomain(PACKAGE, LOCALEDIR);
	bindtextdomain("bison-runtime", BISON_LOCALEDIR);
#endif
	set_err(CDECL__ENOMEM, &err_no_mem);
}

#if USE_POSIX_THREADS
#  include "thread-posix.h"
#elif USE_ISOC_THREADS || USE_ISOC_AND_POSIX_THREADS
#  include "thread-stdc.h"
#elif USE_WINDOWS_THREADS
#  include "thread-w32.h"
#else
static void *tls_key;
enum { tls_key_valid = 1 };

#define tls_get() tls_key
#define tls_set(a) ((tls_key = (a)), 1)

static int init_once(void)
{
	if (!err_no_mem.code)
		init_once_cb();
	return 1;
}

#endif

struct err_state {
	struct cdecl_error err;
	size_t nstr;
	char str[FLEXIBLE_ARRAY_MEMBER];
};

static void *alloc_err_state(void *old, size_t buf_size)
{
	struct err_state *state;
	void *p;

	state = p = realloc(old, offsetof(struct err_state, str) + buf_size);
	if (state) {
		state->nstr = buf_size;
		if (!tls_set(state)) {
			/*
			 * We have to presume that pthread_setspecific etc.
			 * cannot fail after the key has been successfully
			 * assigned once, because there seems to be no
			 * reasonable recovery from such a scenario.
			 */
			free(p);
			p = NULL;
		}
	} else if (old) {
		/* Failed allocation, but existing state is still good */
		p = old;
	}

	return p;
}

static struct err_state *get_err_state(void)
{
	void *state;

	if (!init_once())
		return NULL;

	if (!(state = tls_get()))
		return alloc_err_state(state, 100);
	return state;
}


#if ENABLE_NLS
/*
 * Initialize gettext indirectly via get_err_state.
 */
void cdecl__init_i18n(void)
{
	get_err_state();
}
#endif

/*
 * Set the library error to one of the preset messages defined in errmsg.h
 * (CDECL__Exxx).
 */
void cdecl__errmsg(unsigned msg)
{
	struct err_state *state;

	state = get_err_state();
	if (!state)
		return;

	set_err(msg, &state->err);
}

/*
 * In the NLS-disabled case, all format strings are of the form
 *
 *   "blah blah %s"
 *
 * so we exploit this to implement a simple snprintf workalike using the
 * libcdecl output helpers directly.
 *
 * In the NLS-enabled case, we have to use snprintf as format strings may
 * be translated.  GNU libintl ensures a suitable version is available.
 */
static size_t
fmt_err(struct err_state *state, const char *fmt, const char *arg)
{
#if ENABLE_NLS
	snprintf(state->str, state->nstr, fmt, arg);
	return strlen(fmt) + strlen(arg);
#else
	struct output_state dst = { state->str, state->nstr };
	size_t rc;

	rc = cdecl__strlcpy(dst.dst, fmt, dst.dstlen);
	cdecl__advance(&dst, rc-2);
	cdecl__emit(&dst, arg);

	return dst.accum;
#endif
}

/*
 * Sets the library error to code; fmt is a printf-style string that may use
 * up to one %s directive, to refer to arg.
 */
void cdecl__err(const char *fmt, const char *arg)
{
	struct err_state *state;
	unsigned try = 0;
	size_t rc;

	state = get_err_state();
	if (!state)
		return;

retry:
	rc = fmt_err(state, fmt, arg);
	if (rc >= state->nstr) {
		assert(try++ == 0 && rc < (size_t)-1 / 4);

		state = alloc_err_state(state, (size_t)(rc+1u) * 3 / 2);
		if (!state)
			return;

		goto retry;
	}

	state->err.code = CDECL_ENOPARSE;
	state->err.str = state->str;
}

const struct cdecl_error *cdecl_get_error(void)
{
	struct err_state *state = get_err_state();

	return state ? &state->err : &err_no_mem;
}