Make wrap_lines a lazy range view

Avoid the need to allocate a vector by using the ranges
framework.

src/string_utils.cc

@@ -235,58 +235,61 @@ String expand_tabs(StringView line, ColumnCount tabstop, ColumnCount col)
     return res;
 }
 
-Vector<StringView> wrap_lines(StringView text, ColumnCount max_width)
+WrapView::Iterator::Iterator(StringView text, ColumnCount max_width)
+  : m_remaining{text}, m_max_width{max_width}
 {
     if (max_width <= 0)
         throw runtime_error("Invalid max width");
+    ++*this;
+}
 
+WrapView::Iterator& WrapView::Iterator::operator++()
+{
     using Utf8It = utf8::iterator<const char*>;
-    Utf8It it{text.begin(), text};
-    Utf8It end{text.end(), text};
-    Utf8It line_begin = it;
+    Utf8It it{m_remaining.begin(), m_remaining};
     Utf8It last_word_end = it;
 
-    Vector<StringView> lines;
-    while (it != end)
+    while (it != m_remaining.end())
     {
         const CharCategories cat = categorize(*it, {'_'});
         if (cat == CharCategories::EndOfLine)
         {
-            lines.emplace_back(line_begin.base(), it.base());
-            line_begin = it = it+1;
-            continue;
+            m_current = StringView{m_remaining.begin(), it.base()};
+            m_remaining = StringView{(it+1).base(), m_remaining.end()};
+            return *this;
         }
 
         Utf8It word_end = it+1;
-        while (word_end != end and categorize(*word_end, {'_'}) == cat)
+        while (word_end != m_remaining.end() and categorize(*word_end, {'_'}) == cat)
             ++word_end;
 
-        while (word_end > line_begin and
-               utf8::column_distance(line_begin.base(), word_end.base()) >= max_width)
+        if (word_end > m_remaining.begin() and
+            utf8::column_distance(m_remaining.begin(), word_end.base()) >= m_max_width)
         {
-            auto line_end = last_word_end <= line_begin ?
-                Utf8It{utf8::advance(line_begin.base(), text.end(), max_width), text}
+            auto line_end = last_word_end <= m_remaining.begin() ?
+                Utf8It{utf8::advance(m_remaining.begin(), m_remaining.end(), m_max_width), m_remaining}
               : last_word_end;
 
-            lines.emplace_back(line_begin.base(), line_end.base());
+            m_current = StringView{m_remaining.begin(), line_end.base()};
 
-            while (line_end != end and is_horizontal_blank(*line_end))
+            while (line_end != m_remaining.end() and is_horizontal_blank(*line_end))
                 ++line_end;
 
-            if (line_end != end and *line_end == '\n')
+            if (line_end != m_remaining.end() and *line_end == '\n')
                 ++line_end;
 
-            it = line_begin = line_end;
+            m_remaining = StringView{line_end.base(), m_remaining.end()};
+            return *this;
         }
         if (cat == CharCategories::Word or cat == CharCategories::Punctuation)
             last_word_end = word_end;
 
-        if (word_end > line_begin)
+        if (word_end > m_remaining.begin())
             it = word_end;
     }
-    if (line_begin != end)
-        lines.emplace_back(line_begin.base(), text.end());
-    return lines;
+    m_current = m_remaining;
+    m_remaining = StringView{};
+    return *this;
 }
 
 template<typename AppendFunc>
@@ -378,7 +381,7 @@ UnitTest test_string{[]()
 {
     kak_assert(String("youpi ") + "matin" == "youpi matin");
 
-    Vector<StringView> wrapped = wrap_lines("wrap this paragraph\n respecting whitespaces and much_too_long_words", 16);
+    auto wrapped = "wrap this paragraph\n respecting whitespaces and much_too_long_words" | wrap_at(16) | gather<Vector>();
     kak_assert(wrapped.size() == 6);
     kak_assert(wrapped[0] == "wrap this");
     kak_assert(wrapped[1] == "paragraph");
@@ -387,7 +390,7 @@ UnitTest test_string{[]()
     kak_assert(wrapped[4] == "much_too_long_wo");
     kak_assert(wrapped[5] == "rds");
 
-    Vector<StringView> wrapped2 = wrap_lines("error: unknown type", 7);
+    auto wrapped2 = "error: unknown type" | wrap_at(7) | gather<Vector>();
     kak_assert(wrapped2.size() == 3);
     kak_assert(wrapped2[0] == "error:");
     kak_assert(wrapped2[1] == "unknown");

src/string_utils.hh

@@ -4,6 +4,7 @@
 #include "string.hh"
 #include "enum.hh"
 #include "vector.hh"
+#include "ranges.hh"
 #include "optional.hh"
 
 namespace Kakoune
@@ -61,7 +62,39 @@ bool subsequence_match(StringView str, StringView subseq);
 
 String expand_tabs(StringView line, ColumnCount tabstop, ColumnCount col = 0);
 
-Vector<StringView> wrap_lines(StringView text, ColumnCount max_width);
+struct WrapView
+{
+    struct Iterator : std::iterator<std::forward_iterator_tag, StringView>
+    {
+        Iterator(StringView text, ColumnCount max_width);
+
+        Iterator& operator++();
+        Iterator operator++(int) { auto copy = *this; ++(*this); return copy; }
+
+        bool operator==(Iterator other) const { return m_remaining == other.m_remaining and m_current == other.m_current; }
+        bool operator!=(Iterator other) const { return not (*this == other); }
+
+        StringView operator*() { return m_current; }
+
+    private:
+        StringView m_current;
+        StringView m_remaining;
+        ColumnCount m_max_width;
+    };
+
+    Iterator begin() const { return {text, max_width}; }
+    Iterator end()   const { return {{}, 1}; }
+
+    StringView text;
+    ColumnCount max_width;
+};
+
+inline auto wrap_at(ColumnCount max_width)
+{
+    return make_view_factory([=](StringView text) {
+        return WrapView{text, max_width};
+    });
+}
 
 int str_to_int(StringView str); // throws on error
 Optional<int> str_to_int_ifp(StringView str);