/*
 * Copyright (c) 2020, 2022, 2024 Omar Polo <op@omarpolo.com>
 * Copyright (c) 2015 Theo de Raadt <deraadt@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, 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.
 */

#include "gmid.h"

#include <ctype.h>
#include <string.h>

static inline int
unreserved(int p)
{
	return isalnum((unsigned char)p)
		|| p == '-'
		|| p == '.'
		|| p == '_'
		|| p == '~';
}

static inline int
sub_delimiters(int p)
{
	return p == '!'
		|| p == '$'
		|| p == '&'
		|| p == '\''
		|| p == '('
		|| p == ')'
		|| p == '*'
		|| p == '+'
		|| p == ','
		|| p == ';'
		|| p == '=';
}

static int
valid_pct_enc_string(char *s)
{
	if (*s != '%')
		return 1;

	if (!isxdigit((unsigned char)s[1]) ||
	    !isxdigit((unsigned char)s[2]))
		return 0;

	if (s[1] == '0' && s[2] == '0')
		return 0;

	return 1;
}

static int
valid_pct_encoded(struct parser *p)
{
	if (p->iri[0] != '%')
		return 0;

	if (!valid_pct_enc_string(p->iri)) {
		p->err = "illegal percent-encoding";
		return 0;
	}

	p->iri += 2;
	return 1;
}

static void
pct_decode(char *s)
{
	sscanf(s+1, "%2hhx", s);
	memmove(s+1, s+3, strlen(s+3)+1);
}

static int
parse_pct_encoded(struct parser *p)
{
	if (p->iri[0] != '%')
		return 0;

	if (!valid_pct_enc_string(p->iri)) {
		p->err = "illegal percent-encoding";
		return 0;
	}

	pct_decode(p->iri);
	if (*p->iri == '\0') {
		p->err = "illegal percent-encoding";
		return 0;
	}

	return 1;
}

/* ALPHA *( ALPHA / DIGIT / "+" / "-" / "." ) "://" */
static int
parse_scheme(struct parser *p)
{
	p->parsed->schema = p->iri;

	if (!isalpha((unsigned char)*p->iri)) {
		p->err = "illegal character in scheme";
		return 0;
	}

	do {
		/*
		 * normalize the scheme (i.e. lowercase it)
		 *
		 * XXX: since we cannot have good things, tolower
		 * behaviour depends on the LC_CTYPE locale.  The good
		 * news is that we're sure p->iri points to something
		 * that's in the ASCII range, so tolower can't
		 * mis-behave on some systems due to the locale.
		 */
		*p->iri = tolower(*p->iri);
		p->iri++;
	} while (isalnum((unsigned char)*p->iri)
	    || *p->iri == '+'
	    || *p->iri == '-'
	    || *p->iri == '.');

	if (*p->iri != ':') {
		p->err = "illegal character in scheme";
		return 0;
	}

	*p->iri = '\0';
	if (p->iri[1] != '/' || p->iri[2] != '/') {
		p->err = "invalid marker after scheme";
		return 0;
	}

	p->iri += 3;
	return 1;
}

/* *DIGIT */
static int
parse_port(struct parser *p)
{
	uint32_t i = 0;

	p->parsed->port = p->iri;

	for (; isdigit((unsigned char)*p->iri); p->iri++) {
		i = i * 10 + *p->iri - '0';
		if (i > UINT16_MAX) {
			p->err = "port number too large";
			return 0;
		}
	}

	if (*p->iri != '/' && *p->iri != '\0') {
		p->err = "illegal character in port number";
		return 0;
	}

	p->parsed->port_no = i;

	if (*p->iri != '\0') {
		*p->iri = '\0';
		p->iri++;
	}

	return 1;
}

/* *( unreserved / sub-delims / pct-encoded ) */
static int
parse_authority(struct parser *p)
{
	struct addrinfo	 hints, *ai;
	char		*end;
	int		 err;

	if (*p->iri == '[') {
		p->iri++;
		p->parsed->host = p->iri;
		if ((end = strchr(p->iri, ']')) == NULL) {
			p->err = "invalid IPv6 address";
			return 0;
		}
		*end++ = '\0';
		p->iri = end;

		memset(&hints, 0, sizeof(hints));
		hints.ai_flags = AI_NUMERICHOST;
		err = getaddrinfo(p->parsed->host, NULL, &hints, &ai);
		if (err != 0) {
			p->err = "invalid IPv6 address";
			return 0;
		}
		freeaddrinfo(ai);
	} else {
		p->parsed->host = p->iri;
		while (unreserved(*p->iri)
		    || sub_delimiters(*p->iri)
		    || parse_pct_encoded(p)
		    || valid_multibyte_utf8(p)) {
			/* normalize the host name. */
			if (*p->iri < 0x7F)
				*p->iri = tolower(*p->iri);
			p->iri++;
		}

		if (p->err != NULL)
			return 0;
	}

	if (*p->iri == ':') {
		*p->iri = '\0';
		p->iri++;
		return parse_port(p);
	} else
		p->parsed->port_no = 1965;

	if (*p->iri == '/') {
		*p->iri = '\0';
		p->iri++;
		return 1;
	}

	if (*p->iri == '\0')
		return 1;

	p->err = "illegal character in authority section";
	return 0;
}

/*
 * Use an algorithm based on canonpath() from kern_pledge.c.
 *
 * It's slightly more complicated since even if your paths are
 * absolutely, they don't start with '/'.  q == path asserts
 * that we're at the start of the path.
 */
static int
path_clean(char *path)
{
	char *p, *q;

	p = q = path;
	while (*p) {
		if (q == path && p[0] == '/') {
			/* special case, if path is just "/" trim it */
			p++;
		} else if (q == path && p[0] == '.' && p[1] == '.' &&
		    (p[2] == '/' || p[2] == '\0')) {
			/* ../ at the start of path */
			p += 2;
			if (*p == '/')
				p++;
		} else if (q == path && p[0] == '.' &&
		    (p[1] == '/' || p[1] == '\0')) {
			/* ./ at the start of path */
			p++;
			if (*p == '/')
				p++;
		} else if (p[0] == '/' && p[1] == '/') {
			/* trim double slashes */
			p++;
		} else if (p[0] == '/' && p[1] == '.' && p[2] == '.' &&
		    (p[3] == '/' || p[3] == '\0')) {
			/* /../ component */
			while (q > path && *--q != '/')
				continue;
			p += 3;
			if (q == path && *p == '/')
				p++;
		} else if (p[0] == '/' && p[1] == '.' &&
		    (p[2] == '/' || p[2] == '\0')) {
			/* /./ component */
			p += 2;
		} else {
			*q++ = *p++;
		}
	}
	if (*p != '\0')
		return 0;
	*q = '\0';
	return 1;
}

static int
parse_query(struct parser *p)
{
	p->parsed->query = p->iri;
	if (*p->iri == '\0')
		return 1;

	while (unreserved(*p->iri)
	    || sub_delimiters(*p->iri)
	    || *p->iri == '/'
	    || *p->iri == '?'
	    || *p->iri == ':'
	    || *p->iri == '@'
	    || valid_pct_encoded(p)
	    || valid_multibyte_utf8(p))
		p->iri++;

	if (p->err != NULL)
		return 0;

	if (*p->iri != '\0' && *p->iri != '#') {
		p->err = "illegal character in query";
		return 0;
	}

	if (*p->iri != '\0') {
		*p->iri = '\0';
		p->iri++;
	}

	return 1;
}

/* don't even bother */
static int
parse_fragment(struct parser *p)
{
	p->parsed->fragment = p->iri;
	return 1;
}

/* XXX: is it too broad? */
/* *(pchar / "/") */
static int
parse_path(struct parser *p)
{
	char c;

	/* trim initial slashes */
	while (*p->iri == '/')
		p->iri++;

	p->parsed->path = p->iri;
	if (*p->iri == '\0') {
		p->parsed->query = p->parsed->fragment = p->iri;
		return 1;
	}

	while (unreserved(*p->iri)
	    || sub_delimiters(*p->iri)
	    || *p->iri == '@'
	    || *p->iri == ':'
	    || *p->iri == '/'
	    || parse_pct_encoded(p)
	    || valid_multibyte_utf8(p))
		p->iri++;

	if (p->err != NULL)
		return 0;

	if (*p->iri != '\0' && *p->iri != '?' && *p->iri != '#') {
		p->err = "illegal character in path";
		return 0;
	}

	if (*p->iri != '\0') {
		c = *p->iri;
		*p->iri = '\0';
		p->iri++;

		if (c == '#') {
			if (!parse_fragment(p))
				return 0;
		} else
			if (!parse_query(p) || !parse_fragment(p))
				return 0;
	}

	if (!path_clean(p->parsed->path)) {
		p->err = "illegal path";
		return 0;
	}

	return 1;
}

int
parse_iri(char *iri, struct iri *ret, const char **err_ret)
{
	char *end;
	struct parser p = {
		.iri = iri,
		.parsed = ret,
		.err = NULL,
	};

	memset(ret, 0, sizeof(*ret));

	/* initialize optional stuff to the empty string */
	end = iri + strlen(iri);
	p.parsed->host = end;
	p.parsed->port = end;
	p.parsed->path = end;
	p.parsed->query = end;
	p.parsed->fragment = end;

	if (!parse_scheme(&p) || !parse_authority(&p) || !parse_path(&p)) {
		*err_ret = p.err;
		return 0;
	}

	*err_ret = NULL;
	return 1;
}

int
serialize_iri(struct iri *i, char *buf, size_t len)
{
	size_t l = 0;

	/* in ex.c we receive empty "" strings as NULL */
	if (i->schema == NULL || i->host == NULL) {
		memset(buf, 0, len);
		return 0;
	}

	strlcpy(buf, i->schema, len);
	strlcat(buf, "://", len);
	strlcat(buf, i->host, len);
	strlcat(buf, "/", len);

	if (i->path != NULL)
		l = strlcat(buf, i->path, len);

	if (i->query != NULL && *i->query != '\0') {
		strlcat(buf, "?", len);
		l = strlcat(buf, i->query, len);
	}

	return l < len;
}

int
encode_path(char *buf, size_t len, const char *path)
{
	char *p = buf;
	int a, b;

	memset(buf, 0, len);
	while (*path != '\0') {
		if (len == 1)	/* NUL */
			return -1;

		if (unreserved(*path) ||
		    sub_delimiters(*path) ||
		    *path == '@' ||
		    *path == ':' ||
		    *path == '/') {
			*p++ = *path++;
			len--;
		} else if (len < 4)
			return -1;
		else {
			a = (*path & 0xF0) >> 4;
			b = (*path & 0x0F);

			p[0] = '%';
			p[1] = a <= 9 ? ('0' + a) : ('7' + a);
			p[2] = b <= 9 ? ('0' + b) : ('7' + b);

			path++;
			p += 3;
			len -= 3;
		}
	}

	return 0;
}

char *
pct_decode_str(char *s)
{
	char *t;

	for (t = s; *t; ++t) {
		if (*t == '+')
			*t = ' ';
		else if (*t == '%' && valid_pct_enc_string(t))
			pct_decode(t);
	}

	return s;
}