#include <stdarg.h>
#include <string.h>

#include <posthaste/debug.h>

/**
 * Find position in file buffer where line number \p no
 * starts. Lines are assumed to be one-indexed, with
 * \p no = \c 0 and \p no = \c 1 both considered the first line.
 *
 * @param buf Buffer to look in.
 * @param no Line number whose start to look for.
 * @return Pointer to location in buffer where line number \p no
 * starts.
 */
static const char *find_lineno(const char *buf, size_t no)
{
	if (no == 0 || no == 1)
		return buf;

	char c;
	while ((c = *buf)) {
		buf++;

		if (c == '\n')
			no--;

		if (no == 1)
			break;
	}

	return buf;
}

void vsrc_issue(struct src_issue issue, const char *msg, va_list args)
{
	const char *line_start = find_lineno(issue.buf, issue.loc.first_line);
	const char *line_end = strchr(line_start, '\n');
	if (!line_end)
		line_end = strchr(line_start, 0);

	int line_len = line_end - line_start;

	fprintf(stderr, "%s:%i:%i: ", issue.fname,
	        issue.loc.first_line,
	        issue.loc.first_col);

	vfprintf(stderr, msg, args);
	fputc('\n', stderr);

	int lineno_len = snprintf(NULL, 0, "%i", issue.loc.first_line);
	fputc(' ', stderr);
	fprintf(stderr, "%i | ", issue.loc.first_line);

	fprintf(stderr, "%.*s\n", line_len, line_start);

	for (int i = 0; i < lineno_len + 2; ++i)
		fputc(' ', stderr);

	fprintf(stderr, "| ");

	for (int i = 0; i < issue.loc.first_col - 1; ++i)
		fputc(line_start[i] == '\t' ? '\t' : ' ', stderr);

	for (int i = issue.loc.first_col; i < issue.loc.last_col; ++i) {
		if (i == issue.loc.first_col)
			fputc('^', stderr);
		else
			fputc('~', stderr);
	}

	fputc('\n', stderr);
}

void src_issue(struct src_issue issue, const char *msg, ...)
{
	va_list args;
	va_start(args, msg);
	vsrc_issue(issue, msg, args);
	va_end(args);
}