From 7af40dac48281448e000e65918d7aec6bd1aa8dc Mon Sep 17 00:00:00 2001
From: Linnnus <linnnus@users.noreply.github.com>
Date: Thu, 7 Mar 2024 21:30:29 +0100
Subject: feat(creole): Add nowiki blocks

---
 src/creole.c           | 32 +++++++++++++++++++++++++++++---
 src/creole_test_main.c | 23 +++++++++++++++++++++++
 2 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/src/creole.c b/src/creole.c
index 56edbd8..2a16205 100644
--- a/src/creole.c
+++ b/src/creole.c
@@ -21,10 +21,15 @@ long do_raw_url(const char *begin, const char *end, bool new_block, FILE *out);
 long do_emphasis(const char *begin, const char *end, bool new_block, FILE *out);
 long do_bold(const char *begin, const char *end, bool new_block, FILE *out);
 long do_nowiki_inline(const char *begin, const char *end, bool new_block, FILE *out);
+long do_nowiki_block(const char *begin, const char *end, bool new_block, FILE *out);
 
-// Prints string escaped.
+// Prints string with special HTML characters escaped.
+//
+// Unlike many other functions, this function does not assume that (end >=
+// begin). This simplifies some logic in callers since bracket-matching is prone
+// to off-by-one errors when the brackets are empty.
 void hprint(FILE *out, const char *begin, const char *end) {
-	for (const char *p = begin; p != end; p++) {
+	for (const char *p = begin; p < end; p++) {
 		if (*p == '&') {
 			fputs("&amp;", out);
 		} else if (*p == '"') {
@@ -59,6 +64,7 @@ typedef long (* parser_t)(const char *begin, const char *end, bool new_block, FI
 static parser_t parsers[] = {
 	// Block-level elements
 	do_headers,
+	do_nowiki_block,
 	do_paragraph, // <p> should be last as it eats anything
 
 	// Inline-level elements
@@ -356,7 +362,7 @@ long do_nowiki_inline(const char *begin, const char *end, bool new_block, FILE *
 		trim_start += 1;
 	}
 	const char *trim_stop = stop;
-	while (isspace(trim_stop[-1])) {
+	while (isspace(trim_stop[-1]) && trim_start <= trim_stop - 1) {
 		trim_stop -= 1;
 	}
 
@@ -367,7 +373,27 @@ long do_nowiki_inline(const char *begin, const char *end, bool new_block, FILE *
 	return 3 + (stop - start) + 3; /* {{{...}}} */
 }
 
+long do_nowiki_block(const char *begin, const char *end, bool new_block, FILE *out) {
+	if (!(new_block && starts_with(begin, end, "{{{\n"))) {
+		return 0;
+	}
+	const char *start = begin + 4;
+
+	const char *stop = strnstr(start - 1, "\n}}}", end - (start - 1));
+	if (stop == NULL) {
+		return 0;
+	}
+
+	fputs("<pre><code>", out);
+	hprint(out, start, stop);
+	fputs("</code></pre>", out);
+
+	return -(stop - start + 8);
+}
+
 void process(const char *begin, const char *end, bool new_block, FILE *out) {
+	assert(begin <= end);
+
 	const char *p = begin;
 	while (p < end) {
 		// Eat all newlines if we're starting a block.
diff --git a/src/creole_test_main.c b/src/creole_test_main.c
index 8d531c7..4f71087 100644
--- a/src/creole_test_main.c
+++ b/src/creole_test_main.c
@@ -223,6 +223,29 @@ struct {
 		.input   =  "Creole: Inline nowiki with closing braces: {{{if (a>b) { b = a; }}}}.",
 		.output  =  "<p>Creole: Inline nowiki with closing braces: <tt>if (a&gt;b) { b = a; }</tt>.</p>"
 	},
+	{
+		.name    =  "Nowiki block",
+		.input   =  "Here is some stuff:\n\n{{{\nwad\n}}}",
+		.output  =  "<p>Here is some stuff:</p>"
+		            "<pre><code>wad</code></pre>"
+	},
+	{
+		.name    =  "Non-closed nowiki block",
+		.input   =  "Here is some stuff:\n\n{{{\nwad",
+		.output  =  "<p>Here is some stuff:</p>"
+		            "<p>{{{\nwad</p>"
+	},
+	{
+		.name    =  "Empty nowiki block",
+		.input   =  "{{{\n}}}",
+		.output  =  "<pre><code></code></pre>"
+	},
+	{ // Spec: In preformatted blocks, since markers must not be preceded by leading spaces, lines with three closing braces
+	  // which belong to the preformatted block must follow at least one space. In the rendered output, one leading space is removed.
+		.name    =  "",
+		.input   =  "{{{\nif (x != NULL) {\n  for (i = 0; i < size; i++) {\n    if (x[i] > 0) {\n      x[i]--;\n  }}}\n}}}\n",
+		.output  =  "<pre><code>if (x != NULL) {\n  for (i = 0; i &lt; size; i++) {\n    if (x[i] &gt; 0) {\n      x[i]--;\n  }}}</code></pre>",
+	},
 #if 0
 	{
 		.name    =  "Simple unordered list",
-- 
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