#include "git-compat-util.h"
#include "line-range.h"

/*
 * Parse one item in the -L option
 */
static const char *parse_loc(const char *spec, nth_line_fn_t nth_line,
			     void *data, long lines, long begin, long *ret)
{
	char *term;
	const char *line;
	long num;
	int reg_error;
	regex_t regexp;
	regmatch_t match[1];

	/* Allow "-L <something>,+20" to mean starting at <something>
	 * for 20 lines, or "-L <something>,-5" for 5 lines ending at
	 * <something>.
	 */
	if (1 < begin && (spec[0] == '+' || spec[0] == '-')) {
		num = strtol(spec + 1, &term, 10);
		if (term != spec + 1) {
			if (!ret)
				return term;
			if (spec[0] == '-')
				num = 0 - num;
			if (0 < num)
				*ret = begin + num - 2;
			else if (!num)
				*ret = begin;
			else
				*ret = begin + num;
			return term;
		}
		return spec;
	}
	num = strtol(spec, &term, 10);
	if (term != spec) {
		if (ret)
			*ret = num;
		return term;
	}
	if (spec[0] != '/')
		return spec;

	/* it could be a regexp of form /.../ */
	for (term = (char *) spec + 1; *term && *term != '/'; term++) {
		if (*term == '\\')
			term++;
	}
	if (*term != '/')
		return spec;

	/* in the scan-only case we are not interested in the regex */
	if (!ret)
		return term+1;

	/* try [spec+1 .. term-1] as regexp */
	*term = 0;
	begin--; /* input is in human terms */
	line = nth_line(data, begin);

	if (!(reg_error = regcomp(&regexp, spec + 1, REG_NEWLINE)) &&
	    !(reg_error = regexec(&regexp, line, 1, match, 0))) {
		const char *cp = line + match[0].rm_so;
		const char *nline;

		while (begin++ < lines) {
			nline = nth_line(data, begin);
			if (line <= cp && cp < nline)
				break;
			line = nline;
		}
		*ret = begin;
		regfree(&regexp);
		*term++ = '/';
		return term;
	}
	else {
		char errbuf[1024];
		regerror(reg_error, &regexp, errbuf, 1024);
		die("-L parameter '%s': %s", spec + 1, errbuf);
	}
}

int parse_range_arg(const char *arg, nth_line_fn_t nth_line_cb,
		    void *cb_data, long lines, long *begin, long *end)
{
	arg = parse_loc(arg, nth_line_cb, cb_data, lines, 1, begin);

	if (*arg == ',')
		arg = parse_loc(arg + 1, nth_line_cb, cb_data, lines, *begin + 1, end);

	if (*arg)
		return -1;

	return 0;
}

const char *skip_range_arg(const char *arg)
{
	arg = parse_loc(arg, NULL, NULL, 0, -1, NULL);

	if (*arg == ',')
		arg = parse_loc(arg+1, NULL, NULL, 0, 0, NULL);

	return arg;
}