Rework container helpers, use pipe syntax and cleanup implementation

use 'container | filter(func) | reverse() | transform(func)' instead
of 'transform(reverse(filter(container), func), func)' to express
container transformations.

15 files changed, 175 insertions, 146 deletions

diff --git a/src/alias_registry.cc b/src/alias_registry.cc
index 375246a3..690cde54 100644
--- a/src/alias_registry.cc
+++ b/src/alias_registry.cc
@@ -57,7 +57,7 @@ Vector<std::pair<StringView, StringView>> AliasRegistry::flatten_aliases() const
         res = m_parent->flatten_aliases();
     for (auto& alias : m_aliases)
     {
-        if (not contains(transformed(res, [](const AliasDesc& val) { return val.first; }), alias.key))
+        if (not contains(res | transform([](const AliasDesc& val) { return val.first; }), alias.key))
             res.emplace_back(alias.key, alias.value);
     }
     return res;
diff --git a/src/buffer.cc b/src/buffer.cc
index e140f333..c0e25f0a 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -304,7 +304,7 @@ bool Buffer::undo()
 
     --m_history_cursor;
 
-    for (const Modification& modification : reversed(*m_history_cursor))
+    for (const Modification& modification : *m_history_cursor | reverse())
         apply_modification(modification.inverse());
     return true;
 }
diff --git a/src/client.cc b/src/client.cc
index fcbba14c..cf8b3e71 100644
--- a/src/client.cc
+++ b/src/client.cc
@@ -235,7 +235,7 @@ void Client::redraw_ifn()
 
 void Client::force_redraw()
 {
-    m_ui_pending |= Refresh | Draw |
+    m_ui_pending |= Refresh | Draw | StatusLine |
         (m_menu.items.empty() ? MenuHide : MenuShow | MenuSelect) |
         (m_info.content.empty() ? InfoHide : InfoShow);
 }
diff --git a/src/client_manager.cc b/src/client_manager.cc
index b625fdc5..aff88d93 100644
--- a/src/client_manager.cc
+++ b/src/client_manager.cc
@@ -87,7 +87,7 @@ void ClientManager::remove_client(Client& client, bool graceful)
 
 WindowAndSelections ClientManager::get_free_window(Buffer& buffer)
 {
-    auto it = find_if(reversed(m_free_windows),
+    auto it = find_if(m_free_windows | reverse(),
                       [&](const WindowAndSelections& ws)
                       { return &ws.window->buffer() == &buffer; });
 
@@ -177,10 +177,8 @@ void ClientManager::redraw_clients() const
 CandidateList ClientManager::complete_client_name(StringView prefix,
                                                   ByteCount cursor_pos) const
 {
-    auto c = transformed(m_clients,
-                         [](const std::unique_ptr<Client>& c) -> const String&
-                         { return c->context().name(); });
-
+    auto c = m_clients | transform([](const std::unique_ptr<Client>& c) -> const String&
+                                   { return c->context().name(); });
     return complete(prefix, cursor_pos, c);
 }
 
diff --git a/src/command_manager.cc b/src/command_manager.cc
index 65de501c..4902f068 100644
--- a/src/command_manager.cc
+++ b/src/command_manager.cc
@@ -515,12 +515,15 @@ CommandInfo CommandManager::command_info(const Context& context, StringView comm
 Completions CommandManager::complete_command_name(const Context& context,
                                                   StringView query) const
 {
-    return{0, query.length(), Kakoune::complete(query, query.length(), concatenated(
-        transformed(filtered(m_commands, [](const CommandMap::value_type& cmd)
-                             { return not (cmd.second.flags & CommandFlags::Hidden); }),
-                    [](const CommandMap::value_type& cmd) { return StringView{cmd.first}; }),
-        transformed(context.aliases().flatten_aliases(),
-                    [](AliasRegistry::AliasDesc alias) { return alias.first; })))};
+    auto candidates = Kakoune::complete(
+        query, query.length(), concatenated(
+            m_commands
+            | filter([](const CommandMap::value_type& cmd) { return not (cmd.second.flags & CommandFlags::Hidden); })
+            | transform([](const CommandMap::value_type& cmd) { return StringView{cmd.first}; }),
+            context.aliases().flatten_aliases()
+            | transform([](AliasRegistry::AliasDesc alias) { return alias.first; })));
+
+    return {0, query.length(), std::move(candidates)};
 }
 
 Completions CommandManager::complete(const Context& context,
diff --git a/src/commands.cc b/src/commands.cc
index 3a8d6132..b376f081 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -543,7 +543,7 @@ Completions add_highlighter_completer(
     if (token_to_complete == 1 and params[0] == "-group")
         return complete_highlighter(context, params[1], pos_in_token, true);
     else if (token_to_complete == 0 or (token_to_complete == 2 and params[0] == "-group"))
-        return { 0_byte, arg.length(), complete(arg, pos_in_token, transformed(HighlighterRegistry::instance(), HighlighterRegistry::get_id)) };
+        return { 0_byte, arg.length(), complete(arg, pos_in_token, HighlighterRegistry::instance() | transform(HighlighterRegistry::get_id)) };
     return Completions{};
 }
 
@@ -626,7 +626,7 @@ const CommandDesc rm_highlighter_cmd = {
     [](const ParametersParser& parser, Context& context, const ShellContext&)
     {
         StringView path = parser[0];
-        auto sep_it = find(reversed(path), '/');
+        auto sep_it = find(path | reverse(), '/');
         auto& group = sep_it != path.rend() ?
             get_highlighter(context, {path.begin(), sep_it.base()})
           : context.window().highlighters();
diff --git a/src/containers.hh b/src/containers.hh
index 871714ef..e37208dc 100644
--- a/src/containers.hh
+++ b/src/containers.hh
@@ -8,11 +8,21 @@
 namespace Kakoune
 {
 
+template<typename Factory>
+struct ContainerView { Factory factory; };
+
+template<typename Container, typename Factory>
+auto operator| (Container&& container, ContainerView<Factory> view) ->
+    decltype(view.factory(std::forward<Container>(container)))
+{
+    return view.factory(std::forward<Container>(container));
+}
+
 template<typename Container>
-struct ReversedContainer
+struct ReverseView
 {
     using iterator = decltype(std::declval<Container>().rbegin());
-    ReversedContainer(Container& container) : m_container(container) {}
+    ReverseView(Container& container) : m_container(container) {}
 
     iterator begin() { return m_container.rbegin(); }
     iterator end()   { return m_container.rend(); }
@@ -21,166 +31,186 @@ private:
     Container& m_container;
 };
 
-template<typename Container>
-ReversedContainer<Container> reversed(Container&& container)
-{
-    return ReversedContainer<Container>(container);
-}
-
-template<typename Iterator, typename Filter>
-struct FilteredIterator : std::iterator<std::forward_iterator_tag,
-                                        typename Iterator::value_type>
+struct ReverseFactory
 {
-    FilteredIterator(Filter filter, Iterator it, Iterator end)
-        : m_it{std::move(it)}, m_end{std::move(end)}, m_filter{std::move(filter)}
+    template<typename Container>
+    ReverseView<Container> operator()(Container&& container) const
     {
-        do_filter();
+        return {container};
     }
+};
 
-    auto operator*() -> decltype(*std::declval<Iterator>()) { return *m_it; }
-    FilteredIterator& operator++() { ++m_it; do_filter(); return *this; }
-    FilteredIterator operator++(int) { auto copy = *this; ++(*this); return copy; }
+inline ContainerView<ReverseFactory> reverse() { return {}; }
 
-    friend bool operator==(const FilteredIterator& lhs, const FilteredIterator& rhs)
-    {
-        return lhs.m_it == rhs.m_it;
-    }
+template<typename Container, typename Filter>
+struct FilterView
+{
+    using ContainerIt = decltype(begin(std::declval<Container>()));
 
-    friend bool operator!=(const FilteredIterator& lhs, const FilteredIterator& rhs)
+    struct Iterator : std::iterator<std::forward_iterator_tag,
+                                    typename ContainerIt::value_type>
     {
-        return not (lhs == rhs);
-    }
+        Iterator(const FilterView& view, ContainerIt it, ContainerIt end)
+            : m_it{std::move(it)}, m_end{std::move(end)}, m_view{view}
+        {
+            do_filter();
+        }
+
+        auto operator*() -> decltype(*std::declval<ContainerIt>()) { return *m_it; }
+        Iterator& operator++() { ++m_it; do_filter(); return *this; }
+        Iterator operator++(int) { auto copy = *this; ++(*this); return copy; }
+
+        friend bool operator==(const Iterator& lhs, const Iterator& rhs)
+        {
+            return lhs.m_it == rhs.m_it;
+        }
+
+        friend bool operator!=(const Iterator& lhs, const Iterator& rhs)
+        {
+            return not (lhs == rhs);
+        }
+
+        const ContainerIt& base() const { return m_it; }
+
+    private:
+        void do_filter()
+        {
+            while (m_it != m_end and not m_view.m_filter(*m_it))
+                ++m_it;
+        }
+
+        ContainerIt m_it;
+        ContainerIt m_end;
+        const FilterView& m_view;
+    };
+
+    FilterView(Container& container, Filter filter)
+        : m_container{container}, m_filter{std::move(filter)} {}
 
-    Iterator base() const { return m_it; }
+    Iterator begin() const { return {*this, m_container.begin(), m_container.end()}; }
+    Iterator end()   const { return {*this, m_container.end(), m_container.end()}; }
 
 private:
-    void do_filter()
-    {
-        while (m_it != m_end and not m_filter(*m_it))
-            ++m_it;
-    }
-
-    Iterator m_it;
-    Iterator m_end;
-    Filter   m_filter;
+    Container& m_container;
+    Filter m_filter;
 };
 
-template<typename Container, typename Filter>
-struct FilteredContainer
+template<typename Filter>
+struct FilterFactory
 {
-    using iterator = FilteredIterator<decltype(begin(std::declval<Container>())), Filter>;
-    FilteredContainer(Container& container, Filter filter)
-        : m_container{container}, m_filter{std::move(filter)} {}
+    template<typename Container>
+    FilterView<Container, Filter> operator()(Container&& container) const { return {container, std::move(m_filter)}; }
 
-    iterator begin() const { return {m_filter, m_container.begin(), m_container.end()}; }
-    iterator end()   const { return {m_filter, m_container.end(), m_container.end()}; }
-
-private:
-    Container& m_container;
     Filter m_filter;
 };
 
-template<typename Container, typename Filter>
-FilteredContainer<Container, Filter> filtered(Container&& container, Filter filter)
-{
-    return {container, std::move(filter)};
-}
+template<typename Filter>
+inline ContainerView<FilterFactory<Filter>> filter(Filter f) { return {std::move(f)}; }
 
 template<typename I, typename T>
 using TransformedResult = decltype(std::declval<T>()(*std::declval<I>()));
 
-template<typename Iterator, typename Transform>
-struct TransformedIterator : std::iterator<std::forward_iterator_tag,
-                                           typename std::remove_reference<TransformedResult<Iterator, Transform>>::type>
+template<typename Container, typename Transform>
+struct TransformView
 {
-    TransformedIterator(Transform transform, Iterator it)
-        : m_it{std::move(it)}, m_transform{std::move(transform)} {}
+    using ContainerIt = decltype(begin(std::declval<Container>()));
 
-    auto operator*() -> TransformedResult<Iterator, Transform> { return m_transform(*m_it); }
-    TransformedIterator& operator++() { ++m_it; return *this; }
-    TransformedIterator operator++(int) { auto copy = *this; ++m_it; return copy; }
-
-    friend bool operator==(const TransformedIterator& lhs, const TransformedIterator& rhs)
+    struct Iterator : std::iterator<std::forward_iterator_tag,
+                                    typename std::remove_reference<TransformedResult<ContainerIt, Transform>>::type>
     {
-        return lhs.m_it == rhs.m_it;
-    }
+        Iterator(const TransformView& view, ContainerIt it)
+            : m_it{std::move(it)}, m_view{view} {}
 
-    friend bool operator!=(const TransformedIterator& lhs, const TransformedIterator& rhs)
-    {
-        return not (lhs == rhs);
-    }
+        auto operator*() -> TransformedResult<ContainerIt, Transform> { return m_view.m_transform(*m_it); }
+        Iterator& operator++() { ++m_it; return *this; }
+        Iterator operator++(int) { auto copy = *this; ++m_it; return copy; }
 
-    Iterator base() const { return m_it; }
+        friend bool operator==(const Iterator& lhs, const Iterator& rhs)
+        {
+            return lhs.m_it == rhs.m_it;
+        }
 
-private:
-    Iterator m_it;
-    Transform m_transform;
-};
+        friend bool operator!=(const Iterator& lhs, const Iterator& rhs)
+        {
+            return not (lhs == rhs);
+        }
 
-template<typename Container, typename Transform>
-struct TransformedContainer
-{
-    using iterator = TransformedIterator<decltype(begin(std::declval<Container>())), Transform>;
-    TransformedContainer(Container& container, Transform transform)
+        ContainerIt base() const { return m_it; }
+
+    private:
+        ContainerIt m_it;
+        const TransformView& m_view;
+    };
+
+    TransformView(Container& container, Transform transform)
         : m_container{container}, m_transform{std::move(transform)} {}
 
-    iterator begin() const { return {m_transform, m_container.begin()}; }
-    iterator end()   const { return {m_transform, m_container.end()}; }
+    Iterator begin() const { return {*this, m_container.begin()}; }
+    Iterator end()   const { return {*this, m_container.end()}; }
 
 private:
     Container& m_container;
     Transform m_transform;
 };
 
-template<typename Container, typename Transform>
-TransformedContainer<Container, Transform> transformed(Container&& container, Transform transform)
+template<typename Transform>
+struct TransformFactory
 {
-    return {container, std::move(transform)};
-}
+    template<typename Container>
+    TransformView<Container, Transform> operator()(Container&& container) const { return {container, std::move(m_transform)}; }
 
-template<typename Iterator1, typename Iterator2, typename ValueType = typename Iterator1::value_type>
-struct ConcatenatedIterator : std::iterator<std::forward_iterator_tag, ValueType>
-{
-    static_assert(std::is_convertible<typename Iterator1::value_type, ValueType>::value, "");
-    static_assert(std::is_convertible<typename Iterator2::value_type, ValueType>::value, "");
+    Transform m_transform;
+};
 
-    ConcatenatedIterator(Iterator1 it1, Iterator1 end1, Iterator2 it2)
-        : m_it1(std::move(it1)), m_end1(std::move(end1)), m_it2(std::move(it2)) {}
+template<typename Transform>
+inline ContainerView<TransformFactory<Transform>> transform(Transform t) { return {std::move(t)}; }
 
-    decltype(*std::declval<Iterator1>()) operator*() { return is2() ? *m_it2 : *m_it1; }
-    ConcatenatedIterator& operator++() { if (is2()) ++m_it2; else ++m_it1; return *this; }
-    ConcatenatedIterator operator++(int) { auto copy = *this; ++*this; return copy; }
 
-    friend bool operator==(const ConcatenatedIterator& lhs, const ConcatenatedIterator& rhs)
-    {
-        return lhs.m_it1 == rhs.m_it1 and lhs.m_end1 == rhs.m_end1 and lhs.m_it2 == rhs.m_it2;
-    }
 
-    friend bool operator!=(const ConcatenatedIterator& lhs, const ConcatenatedIterator& rhs)
+template<typename Container1, typename Container2>
+struct ConcatView
+{
+    using ContainerIt1 = decltype(begin(std::declval<Container1>()));
+    using ContainerIt2 = decltype(begin(std::declval<Container2>()));
+    using ValueType = typename ContainerIt1::value_type;
+
+    struct Iterator : std::iterator<std::forward_iterator_tag, ValueType>
     {
-        return not (lhs == rhs);
-    }
+        static_assert(std::is_convertible<typename ContainerIt1::value_type, ValueType>::value, "");
+        static_assert(std::is_convertible<typename ContainerIt2::value_type, ValueType>::value, "");
 
-private:
-    bool is2() const { return m_it1 == m_end1; }
+        Iterator(ContainerIt1 it1, ContainerIt1 end1, ContainerIt2 it2)
+            : m_it1(std::move(it1)), m_end1(std::move(end1)),
+              m_it2(std::move(it2)) {}
 
-    Iterator1 m_it1;
-    Iterator1 m_end1;
-    Iterator2 m_it2;
-};
+        decltype(*std::declval<ContainerIt1>()) operator*() { return is2() ? *m_it2 : *m_it1; }
+        Iterator& operator++() { if (is2()) ++m_it2; else ++m_it1; return *this; }
+        Iterator operator++(int) { auto copy = *this; ++*this; return copy; }
 
+        friend bool operator==(const Iterator& lhs, const Iterator& rhs)
+        {
+            return lhs.m_it1 == rhs.m_it1 and lhs.m_end1 == rhs.m_end1 and
+                   lhs.m_it2 == rhs.m_it2;
+        }
 
-template<typename Container1, typename Container2>
-struct ConcatenatedContainer
-{
-    using iterator = ConcatenatedIterator<decltype(begin(std::declval<Container1>())),
-                                          decltype(begin(std::declval<Container2>()))>;
+        friend bool operator!=(const Iterator& lhs, const Iterator& rhs)
+        {
+            return not (lhs == rhs);
+        }
+
+    private:
+        bool is2() const { return m_it1 == m_end1; }
+
+        ContainerIt1 m_it1;
+        ContainerIt1 m_end1;
+        ContainerIt2 m_it2;
+    };
 
-    ConcatenatedContainer(Container1& container1, Container2& container2)
+    ConcatView(Container1& container1, Container2& container2)
         : m_container1{container1}, m_container2{container2} {}
 
-    iterator begin() const { return {m_container1.begin(), m_container1.end(), m_container2.begin()}; }
-    iterator end()   const { return {m_container1.end(), m_container1.end(), m_container2.end()}; }
+    Iterator begin() const { return {m_container1.begin(), m_container1.end(), m_container2.begin()}; }
+    Iterator end()   const { return {m_container1.end(), m_container1.end(), m_container2.end()}; }
 
 private:
     Container1& m_container1;
@@ -188,7 +218,7 @@ private:
 };
 
 template<typename Container1, typename Container2>
-ConcatenatedContainer<Container1, Container2> concatenated(Container1&& container1, Container2&& container2)
+ConcatView<Container1, Container2> concatenated(Container1&& container1, Container2&& container2)
 {
     return {container1, container2};
 }
diff --git a/src/face_registry.cc b/src/face_registry.cc
index 3a5ac6e1..7da57e9c 100644
--- a/src/face_registry.cc
+++ b/src/face_registry.cc
@@ -95,9 +95,8 @@ CandidateList FaceRegistry::complete_alias_name(StringView prefix,
                                                 ByteCount cursor_pos) const
 {
     return complete(prefix, cursor_pos,
-                    transformed(m_aliases,
-                                [](const AliasMap::value_type& v) -> const String&
-                                { return v.first; }));
+                    m_aliases | transform([](const AliasMap::value_type& v) -> const String&
+                                          { return v.first; }));
 }
 
 FaceRegistry::FaceRegistry()
diff --git a/src/file.cc b/src/file.cc
index 2d3e6a82..6cf9a735 100644
--- a/src/file.cc
+++ b/src/file.cc
@@ -63,7 +63,7 @@ String parse_filename(StringView filename)
 
 std::pair<StringView, StringView> split_path(StringView path)
 {
-    auto it = find(reversed(path), '/');
+    auto it = find(path | reverse(), '/');
     if (it == path.rend())
         return { {}, path };
     const char* slash = it.base()-1;
diff --git a/src/highlighter_group.cc b/src/highlighter_group.cc
index d3755734..2d0a7a74 100644
--- a/src/highlighter_group.cc
+++ b/src/highlighter_group.cc
@@ -52,10 +52,9 @@ Completions HighlighterGroup::complete_child(StringView path, ByteCount cursor_p
 
     auto candidates = complete(
         path, cursor_pos,
-        transformed(filtered(m_highlighters,
-                             [=](const HighlighterMap::Element& hl)
-                             { return not group or hl.value->has_children(); }),
-                    HighlighterMap::get_id));
+        m_highlighters | filter([=](const HighlighterMap::Element& hl)
+                                { return not group or hl.value->has_children(); })
+                       | transform(HighlighterMap::get_id));
 
     return { 0, 0, std::move(candidates) };
 }
diff --git a/src/highlighters.cc b/src/highlighters.cc
index 740320ac..871d549c 100644
--- a/src/highlighters.cc
+++ b/src/highlighters.cc
@@ -1303,7 +1303,7 @@ public:
             return offset_pos(hl.complete_child(path.substr(offset), cursor_pos - offset, group), offset);
         }
 
-        auto container = transformed(m_groups, decltype(m_groups)::get_id);
+        auto container = m_groups | transform(decltype(m_groups)::get_id);
         return { 0, 0, complete(path, cursor_pos, container) };
     }
 
diff --git a/src/hook_manager.cc b/src/hook_manager.cc
index 81a00730..389c8504 100644
--- a/src/hook_manager.cc
+++ b/src/hook_manager.cc
@@ -31,7 +31,7 @@ CandidateList HookManager::complete_hook_group(StringView prefix, ByteCount pos_
     CandidateList res;
     for (auto& list : m_hook)
     {
-        auto container = transformed(list.value, decltype(list.value)::get_id);
+        auto container = list.value | transform(decltype(list.value)::get_id);
         for (auto& c : complete(prefix, pos_in_token, container))
         {
             if (!contains(res, c))
diff --git a/src/main.cc b/src/main.cc
index 622543f1..0a9e713e 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -61,9 +61,9 @@ void register_env_vars()
         }, {
             "buflist", false,
             [](StringView name, const Context& context)
-            { return join(transformed(BufferManager::instance(),
-                                      [](const SafePtr<Buffer>& b)
-                                      { return b->display_name(); }), ':'); }
+            { return join(BufferManager::instance() |
+                          transform([](const SafePtr<Buffer>& b)
+                                    { return b->display_name(); }), ':'); }
         }, {
             "timestamp", false,
             [](StringView name, const Context& context) -> String
@@ -520,7 +520,7 @@ int run_server(StringView session, StringView init_command,
     {
         // create buffers in reverse order so that the first given buffer
         // is the most recently created one.
-        for (auto& file : reversed(files))
+        for (auto& file : files | reverse())
         {
             try
             {
diff --git a/src/selection.cc b/src/selection.cc
index f24b0939..90580bdd 100644
--- a/src/selection.cc
+++ b/src/selection.cc
@@ -555,8 +555,8 @@ String selection_to_string(const Selection& selection)
 
 String selection_list_to_string(const SelectionList& selections)
 {
-    return join(transformed(selections, [](const Selection& s)
-                            { return selection_to_string(s); }),
+    return join(selections | transform([](const Selection& s)
+                                       { return selection_to_string(s); }),
                 ':', false);
 }
 
diff --git a/src/selectors.cc b/src/selectors.cc
index 662cd6b0..1ca42a28 100644
--- a/src/selectors.cc
+++ b/src/selectors.cc
@@ -128,7 +128,7 @@ find_surrounding(Iterator begin, Iterator end,
     {
         using RevIt = std::reverse_iterator<Iterator>;
         auto res = find_closing(RevIt{pos+1}, RevIt{begin},
-                                reversed(closing), reversed(opening),
+                                closing | reverse(), opening | reverse(),
                                 init_level, nestable);
         if (not res)
             return {};