test: enhance hashtag span tests for better coverage and edge cases

test/test_utf8_text.cpp

@@ -5,8 +5,43 @@
 #include <string>
 
 #include "ui-touch/Utf8Text.h"
+#include "ui-touch/ChatHashtag.h"
+
+int main()
+{
+  int start, end;
+  const char tags[] = "Try #caf\xC3\xA8 and #cr\xC3\xA8me-br\xC3\xBBl\xC3\xA9"
+                      "e!";
+  assert(ChatHashtag::span(tags, 0, &start, &end));
+  assert(std::string(tags + start, end - start) == "#caf\xC3\xA8");
+  assert(ChatHashtag::span(tags, end, &start, &end));
+  assert(std::string(tags + start, end - start) == "#cr\xC3\xA8me-br\xC3\xBBl\xC3\xA9"
+                                                   "e");
+  assert(!ChatHashtag::span(tags, end, &start, &end));
+  const char decomposed[] = "#cafe\xCC\x80";
+  assert(ChatHashtag::span(decomposed, 0, &start, &end));
+  assert(end == (int)strlen(decomposed));
+  assert(!ChatHashtag::span("@[#caf\xC3\xA8]", 0, &start, &end));
+  assert(!ChatHashtag::span("https://example.org/#caf\xC3\xA8", 0, &start, &end));
+  assert(!ChatHashtag::span("caf\xC3\xA8#tag", 0, &start, &end));
+  assert(!ChatHashtag::span("#caf\xC3", 0, &start, &end));
+  assert(!ChatHashtag::span("#1", 0, &start, &end));
+  assert(!ChatHashtag::span("#1channel", 0, &start, &end));
+  assert(ChatHashtag::span("#channel1", 0, &start, &end));
+  assert(!ChatHashtag::span("#FFF", 0, &start, &end));
+  assert(!ChatHashtag::span("#FFFF", 0, &start, &end));
+  assert(!ChatHashtag::span("#FFFFFF", 0, &start, &end));
+  assert(!ChatHashtag::span("#FF0000", 0, &start, &end));
+  assert(!ChatHashtag::span("#FFFFFFFF", 0, &start, &end));
+  assert(ChatHashtag::span("#cable", 0, &start, &end));
+  std::string long_tag = "#";
+  for (int count = 0; count < 15; ++count)
+    long_tag += "\xC3\xA8";
+  assert(ChatHashtag::span(long_tag.c_str(), 0, &start, &end));
+  assert(end == 31);
+  long_tag += "\xC3\xA8";
+  assert(!ChatHashtag::span(long_tag.c_str(), 0, &start, &end));
 
-int main() {
   const char full[] = "Ouderkerk\xE2\x98\x80\xEF\xB8\x8F";
   assert(strlen(full) == 15);
   assert(Utf8Text::valid(full, strlen(full)));