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

#include <posthaste/debug.h>

/* find the start of line number no in buffer buf */
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;
}

static void print_bar(int lineno_len)
{
	fprintf(stderr, "%*s", lineno_len + 4, "| ");
}

static void vsrc_multi_line(struct src_issue issue, const char *line_start,
                            int lineno_len)
{
	/* just dump lines as they are, adding bars to the left */
	size_t line = issue.loc.first_line;
	for (size_t i = 0;; ++i) {
		char c = line_start[i];
		if (c == 0) {
			fputc('\n', stderr);
			break;
		}

		fputc(c, stderr);


		if (c == '\n') {
			if (++line > issue.loc.last_line)
				break;

			print_bar(lineno_len);
		}
	}
}

void vsrc_issue(struct src_issue issue, const char *msg, va_list args)
{
	/* with color support we could start coloring the actual error region at
	 * issue.loc.first_column on issue.loc.first_line, but messing with
	 * xterm color codes is a bit cumbersome so for now just stick to
	 * monochrome */

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

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

	/* figure out how many spaces line number takes up */
	int lineno_len = snprintf(NULL, 0, "%i", issue.loc.first_line);
	fprintf(stderr, " %i | ", issue.loc.first_line);

	const char *line_start = find_lineno(issue.buf, issue.loc.first_line);
	if (issue.loc.first_line != issue.loc.last_line) {
		/* multiline location requires slightly different handling */
		return vsrc_multi_line(issue, line_start, lineno_len);
	}

	/* print the offending line */
	for (size_t i = 0;; ++i) {
		char c = line_start[i];
		if (c == 0 || c == '\n')
			break;

		fputc(c, stderr);
	}
	fputc('\n', stderr);

	/* the rest is just to print a little squiggly line to highlight exact location */
	print_bar(lineno_len);

	/* print tabs on tabs, otherwise spaces to make start of squiggle line
	 * up with start of offending location */
	for (size_t i = 0; i < issue.loc.first_col - 1; ++i)
		fputc(line_start[i] == '\t' ? '\t' : ' ', stderr);

	/* highlight the offending location */
	for (size_t 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);
}