Add jump list support to context

jump forward is bound to ctrl-i
jump backward is bound to ctrl-o

switch buffers or jumping somewhere in the buffer push the current
position to the jump list.

when a buffer is deleted, all entries referencing it in jump lists
are erased.

4 files changed, 98 insertions, 0 deletions

diff --git a/src/client_manager.cc b/src/client_manager.cc
index 07322fed..c2a7dcce 100644
--- a/src/client_manager.cc
+++ b/src/client_manager.cc
@@ -67,6 +67,8 @@ void ClientManager::ensure_no_client_uses_buffer(Buffer& buffer)
 {
     for (auto& client : m_clients)
     {
+        client.context->forget_jumps_to_buffer(buffer);
+
         if (&client.context->buffer() != &buffer)
             continue;
 
diff --git a/src/commands.cc b/src/commands.cc
index 55fcf2ff..899b4fd4 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -283,6 +283,9 @@ void edit(const CommandParameters& params, Context& context)
 
     BufferManager::instance().set_last_used_buffer(*buffer);
 
+    if (buffer != &context.buffer() or param_count > 1)
+        context.push_jump();
+
     if (buffer != &context.buffer())
     {
         auto& manager = ClientManager::instance();
@@ -385,6 +388,7 @@ void show_buffer(const CommandParameters& params, Context& context)
 
     if (buffer != &context.buffer())
     {
+        context.push_jump();
         auto& manager = ClientManager::instance();
         context.change_editor(manager.get_unused_window_for_buffer(*buffer));
     }
diff --git a/src/context.hh b/src/context.hh
index 0568c6c4..844b4d04 100644
--- a/src/context.hh
+++ b/src/context.hh
@@ -100,6 +100,62 @@ struct Context
     using Insertion = std::pair<InsertMode, std::vector<Key>>;
     Insertion& last_insert() { return m_last_insert; }
 
+    using Jump = std::pair<safe_ptr<Buffer>, BufferCoord>;
+    void push_jump()
+    {
+        Jump jump{safe_ptr<Buffer>{&buffer()},
+                  editor().selections().back().last().coord()};
+        if (m_current_jump != m_jump_list.end())
+        {
+            m_jump_list.erase(m_current_jump+1, m_jump_list.end());
+            if (*m_current_jump == jump)
+                return;
+        }
+
+        m_jump_list.push_back(jump);
+        m_current_jump = m_jump_list.end();
+    }
+
+    Jump jump_forward()
+    {
+        if (m_current_jump != m_jump_list.end() and
+            m_current_jump + 1 != m_jump_list.end())
+            return *++m_current_jump;
+        throw runtime_error("no next jump");
+    }
+
+    Jump jump_backward()
+    {
+        if (m_current_jump != m_jump_list.begin())
+        {
+            if (m_current_jump == m_jump_list.end())
+            {
+                push_jump();
+                --m_current_jump;
+            }
+            return *--m_current_jump;
+        }
+        throw runtime_error("no previous jump");
+    }
+
+    void forget_jumps_to_buffer(Buffer& buffer)
+    {
+        for (auto it = m_jump_list.begin(); it != m_jump_list.end();)
+        {
+            if (it->first == &buffer)
+            {
+                if (it < m_current_jump)
+                    --m_current_jump;
+                else if (it == m_current_jump)
+                    m_current_jump = m_jump_list.end();
+
+                it = m_jump_list.erase(it);
+            }
+            else
+                ++it;
+        }
+    }
+
     int& numeric_param() { return m_numeric_param; }
 private:
     safe_ptr<Editor>        m_editor;
@@ -108,6 +164,10 @@ private:
 
     Insertion m_last_insert = {InsertMode::Insert, {}};
     int m_numeric_param = 0;
+
+    using JumpList = std::vector<Jump>;
+    JumpList           m_jump_list;
+    JumpList::iterator m_current_jump = m_jump_list.begin();
 };
 
 }
diff --git a/src/main.cc b/src/main.cc
index 95ef2f63..9f2136dc 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -59,6 +59,7 @@ void do_go(Context& context)
         BufferIterator target =
             context.editor().buffer().iterator_at_line_begin(count-1);
 
+        context.push_jump();
         context.editor().select(target);
         if (context.has_window())
             context.window().center_selection();
@@ -73,6 +74,7 @@ void do_go(Context& context)
             {
             case 'g':
             case 't':
+                context.push_jump();
                 editor.select(editor.buffer().begin());
                 break;
             case 'l':
@@ -85,6 +87,7 @@ void do_go(Context& context)
                 break;
             case 'b':
             {
+                context.push_jump();
                 const Buffer& buf = editor.buffer();
                 editor.select(buf.iterator_at_line_begin(buf.line_count() - 1));
                 break;
@@ -329,6 +332,32 @@ void select_to_next_char(Context& context)
    });
 }
 
+void jump_forward(Context& context)
+{
+    auto jump = context.jump_forward();
+
+    BufferManager::instance().set_last_used_buffer(*jump.first);
+    if (jump.first != &context.buffer())
+    {
+        auto& manager = ClientManager::instance();
+        context.change_editor(manager.get_unused_window_for_buffer(*jump.first));
+    }
+    context.editor().select(jump.first->iterator_at(jump.second));
+}
+
+void jump_backward(Context& context)
+{
+    auto jump = context.jump_backward();
+
+    BufferManager::instance().set_last_used_buffer(*jump.first);
+    if (jump.first != &context.buffer())
+    {
+        auto& manager = ClientManager::instance();
+        context.change_editor(manager.get_unused_window_for_buffer(*jump.first));
+    }
+    context.editor().select(jump.first->iterator_at(jump.second));
+}
+
 String runtime_directory()
 {
     char buffer[2048];
@@ -448,6 +477,9 @@ std::unordered_map<Key, std::function<void (Context& context)>> keymap =
 
     { { Key::Modifiers::None, Key::PageUp }, do_scroll<Key::PageUp> },
     { { Key::Modifiers::None, Key::PageDown }, do_scroll<Key::PageDown> },
+
+    { { Key::Modifiers::Control, 'i' }, jump_forward },
+    { { Key::Modifiers::Control, 'o' }, jump_backward },
 };
 
 }