/** @license 2022 Neil Edelman, distributed under the terms of the
 [MIT License](https://opensource.org/licenses/MIT).

 Lexer for journal entries.

 @std C89/90 */

#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <limits.h>
#include <errno.h>

static int parse_uint(const char *s, const char *e, unsigned *u) {
    uint32_t n = 0;
    for ( ; s < e; ++s) {
		unsigned digit = (unsigned)(*s - '0');
		assert(digit < 10);
		if(n > (UINT_MAX - digit) / 10) return errno = ERANGE, 0; /* check */
		n = n * 10 + digit;
	}
	*u = n;
    return 1;
}

static int parse_double(const char *s0, const char *s1, double *d) {
	char *finish;
	assert(d && s0 && s0 < s1);
	*d = strtod(s0, &finish);
	return !errno && ((finish == s1) || (errno = EDOM, 0));
}

static int lex_line(const char *YYCURSOR, unsigned *const u) {
	const char *YYMARKER, *o1, *o2, *o3, *o4;
	double d;
	/*!stags:re2c format = 'const char *@@;\n'; */
	/*!re2c
	re2c:yyfill:enable = 0;
	re2c:flags:tags = 1;
	re2c:define:YYCTYPE = char;

	keyword = [a-z][a-z0-9_-]{0,64}; // uppercase is lame
	octet = [0-9] | [1-9][0-9] | [1][0-9][0-9] | [2][0-4][0-9] | [2][5][0-5];
	dot = [.];
	end = [\x00];

	eol = [\n];
	w = [ \t]*;
	double = [0-9]* "." [0-9]+ | [0-9]+;
	*/
	errno = 0; /* For accuracy detecting errors. */
text:
	/*!re2c
	"\\[" | "\\![" { goto text; }
	"[" { goto custom; }
	"![" { goto image; }
	@o1 octet dot @o2 octet dot @o3 octet dot @o4 octet end {
		unsigned u1, u2, u3, u4;
		if(!parse_uint(o1, o2 - 1, &u1)
			|| !parse_uint(o2, o3 - 1, &u2)
			|| !parse_uint(o3, o4 - 1, &u3)
			|| !parse_uint(o4, YYCURSOR - 1, &u4)) return 0;
		*u = u4 + (u3 << 8) + (u2 << 16) + (u1 << 24);
		return 1;
	}
	* { return errno = EILSEQ, 0; }
	*/
image:
	/*!re2c
	"osm" "](" @o1 double @o2 "," @o3 double @o4 ")" {
		printf("Got a map.\n");
		if(!parse_double(o1, o2, &d)) return 0;
		printf("Latitude %f.\n", d);
		if(!parse_double(o3, o4, &d)) return 0;
		printf("Longitude %f.\n", d);
		goto text;
	}
	* { return errno = EILSEQ, 0; }
	*/
custom:
	/*!re2c
	glider = "glider" ":" ;
	flight = "flight" ":" ;
	* { return errno = EILSEQ, 0; }
	*/
}


int main(int argc, char **argv) {
	unsigned u;
	if(!lex_line("1.2.3.4", &u)) goto catch;
	printf("0x%x\n", u);
	if(!lex_line("1.2.3.49999999999999999", &u)) goto catch;
	return EXIT_SUCCESS;
catch:
	perror("interpret");
	return EXIT_FAILURE;
}