fixed and optimized the autocompletion

src/common/UsernameSet.cpp

@@ -0,0 +1,110 @@
+#include "UsernameSet.hpp"
+
+#include <tuple>
+
+namespace chatterino {
+
+//
+// UsernameSet
+//
+
+UsernameSet::ConstIterator UsernameSet::begin() const
+{
+    return this->items.begin();
+}
+
+UsernameSet::ConstIterator UsernameSet::end() const
+{
+    return this->items.end();
+}
+
+UsernameSet::Range UsernameSet::subrange(const Prefix &prefix) const
+{
+    auto it = this->firstKeyForPrefix.find(prefix);
+    if (it != this->firstKeyForPrefix.end()) {
+        auto start = this->items.find(it->second);
+        auto end = start;
+
+        while (end != this->items.end() && prefix.isStartOf(*end)) {
+            end++;
+        }
+        return {start, end};
+    }
+
+    return {this->items.end(), this->items.end()};
+}
+
+std::set<QString>::size_type UsernameSet::size() const
+{
+    return this->items.size();
+}
+
+std::pair<UsernameSet::Iterator, bool> UsernameSet::insert(const QString &value)
+{
+    this->insertPrefix(value);
+
+    return this->items.insert(value);
+}
+
+std::pair<UsernameSet::Iterator, bool> UsernameSet::insert(QString &&value)
+{
+    this->insertPrefix(value);
+
+    return this->items.insert(std::move(value));
+}
+
+void UsernameSet::insertPrefix(const QString &value)
+{
+    auto &string = this->firstKeyForPrefix[Prefix(value)];
+
+    if (string.isNull() || value < string) string = value;
+}
+
+//
+// Range
+//
+
+UsernameSet::Range::Range(ConstIterator start, ConstIterator end)
+    : start_(start)
+    , end_(end)
+{
+}
+
+UsernameSet::ConstIterator UsernameSet::Range::begin()
+{
+    return this->start_;
+}
+
+UsernameSet::ConstIterator UsernameSet::Range::end()
+{
+    return this->end_;
+}
+
+//
+// Prefix
+//
+
+Prefix::Prefix(const QString &string)
+    : first(string.size() >= 1 ? string[0] : '\0')
+    , second(string.size() >= 2 ? string[1] : '\0')
+{
+}
+
+bool Prefix::operator==(const Prefix &other) const
+{
+    return std::tie(this->first, this->second) ==
+           std::tie(other.first, other.second);
+}
+
+bool Prefix::isStartOf(const QString &string) const
+{
+    if (string.size() == 0) {
+        return this->first == QChar('\0') && this->second == QChar('\0');
+    } else if (string.size() == 1) {
+        return this->first == string[0] && this->second == QChar('\0');
+    } else {
+        return this->first == string[0] && this->second == string[1];
+    }
+}
+
+}  // namespace chatterino