LibGUI: Abstract token pair matching

Libraries/LibGUI/SyntaxHighlighter.cpp

@@ -7,6 +7,98 @@ SyntaxHighlighter::~SyntaxHighlighter()
 {
 }
 
+void SyntaxHighlighter::highlight_matching_token_pair()
+{
+    ASSERT(m_editor);
+    auto& document = m_editor->document();
+
+    enum class Direction {
+        Forward,
+        Backward,
+    };
+
+    auto find_span_of_type = [&](auto i, void* type, void* not_type, Direction direction) -> Optional<size_t> {
+        size_t nesting_level = 0;
+        bool forward = direction == Direction::Forward;
+
+        if (forward) {
+            ++i;
+            if (i >= document.spans().size())
+                return {};
+        } else {
+            if (i == 0)
+                return {};
+            --i;
+        }
+
+        for (;;) {
+            auto& span = document.spans().at(i);
+            auto span_token_type = span.data;
+            if (token_types_equal(span_token_type, not_type)) {
+                ++nesting_level;
+            } else if (token_types_equal(span_token_type, type)) {
+                if (nesting_level-- <= 0)
+                    return i;
+            }
+
+            if (forward) {
+                ++i;
+                if (i >= document.spans().size())
+                    return {};
+            } else {
+                if (i == 0)
+                    return {};
+                --i;
+            }
+        }
+
+        return {};
+    };
+
+    auto make_buddies = [&](int index0, int index1) {
+        auto& buddy0 = document.spans()[index0];
+        auto& buddy1 = document.spans()[index1];
+        m_has_brace_buddies = true;
+        m_brace_buddies[0].index = index0;
+        m_brace_buddies[1].index = index1;
+        m_brace_buddies[0].span_backup = buddy0;
+        m_brace_buddies[1].span_backup = buddy1;
+        buddy0.background_color = Color::DarkCyan;
+        buddy1.background_color = Color::DarkCyan;
+        buddy0.color = Color::White;
+        buddy1.color = Color::White;
+        m_editor->update();
+    };
+
+    auto pairs = matching_token_pairs();
+
+    for (size_t i = 0; i < document.spans().size(); ++i) {
+        auto& span = const_cast<GUI::TextDocumentSpan&>(document.spans().at(i));
+        auto token_type = span.data;
+
+        for (auto& pair : pairs) {
+            if (token_types_equal(token_type, pair.open) && span.range.start() == m_editor->cursor()) {
+                auto buddy = find_span_of_type(i, pair.close, pair.open, Direction::Forward);
+                if (buddy.has_value())
+                    make_buddies(i, buddy.value());
+                return;
+            }
+        }
+
+        auto right_of_end = span.range.end();
+        right_of_end.set_column(right_of_end.column() + 1);
+
+        for (auto& pair : pairs) {
+            if (token_types_equal(token_type, pair.close) && right_of_end == m_editor->cursor()) {
+                auto buddy = find_span_of_type(i, pair.open, pair.close, Direction::Backward);
+                if (buddy.has_value())
+                    make_buddies(i, buddy.value());
+                return;
+            }
+        }
+    }
+}
+
 void SyntaxHighlighter::attach(TextEditor& editor)
 {
     ASSERT(!m_editor);