1 files changed, 63 insertions, 0 deletions
diff --git a/src/diag/diag.c b/src/diag/diag.c
new file mode 100644
index 0000000..cc61e89
--- /dev/null
+++ b/src/diag/diag.c
@@ -0,0 +1,63 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include "diag/diag.h"
+
+static bool colored(void)
+{
+	return getenv("NO_COLOR") == NULL;
+}
+
+void report_error(struct Source source, struct Token token, const char* message)
+{
+	const char* name = source.name != NULL ? source.name : "<source>";
+	const char* text = source.text;
+
+	const char* line_start = token.start;
+	while (line_start > text && line_start[-1] != '\n')
+		line_start -= 1;
+
+	const char* line_end = token.start;
+	while (*line_end != '\0' && *line_end != '\n')
+		line_end += 1;
+
+	uint32_t column = (uint32_t)(token.start - line_start) + 1;
+
+	size_t span = token.length > 0 ? token.length : 1;
+	if ((size_t)(line_end - token.start) < span)
+		span = (size_t)(line_end - token.start);
+	if (span == 0)
+		span = 1;
+
+	const char* bold  = colored() ? "\033[1m" : "";
+	const char* red   = colored() ? "\033[31m" : "";
+	const char* blue  = colored() ? "\033[34m" : "";
+	const char* reset = colored() ? "\033[0m" : "";
+
+	int gutter = snprintf(NULL, 0, "%u", token.line);
+
+	fprintf(stderr, "%s%serror:%s %s%s%s\n", bold, red, reset, bold, message, reset);
+	fprintf(stderr, "%*s %s-->%s %s:%u:%u\n", gutter, "", blue, reset, name, token.line, column);
+	fprintf(stderr, "%*s %s|%s\n", gutter, "", blue, reset);
+	fprintf(stderr, "%s%u%s %s|%s %.*s\n", blue, token.line, reset, blue, reset,
+		(int)(line_end - line_start), line_start);
+	fprintf(stderr, "%*s %s|%s ", gutter, "", blue, reset);
+
+	for (const char* character = line_start; character < token.start; character += 1)
+		fputc(*character == '\t' ? '\t' : ' ', stderr);
+
+	fprintf(stderr, "%s", red);
+	for (size_t i = 0; i < span; i += 1)
+		fputc('^', stderr);
+	fprintf(stderr, "%s\n", reset);
+}
+
+void report_error_message(const char* message)
+{
+	const char* bold  = colored() ? "\033[1m" : "";
+	const char* red   = colored() ? "\033[31m" : "";
+	const char* reset = colored() ? "\033[0m" : "";
+
+	fprintf(stderr, "%s%serror:%s %s%s%s\n", bold, red, reset, bold, message, reset);
+}