feat(usermarks): add runtime files for usermarks

1 files changed, 65 insertions, 0 deletions

diff --git a/runtime/lua/vim/usermark.lua b/runtime/lua/vim/usermark.lua
new file mode 100644
index 0000000000..ca5b9a3a72
--- /dev/null
+++ b/runtime/lua/vim/usermark.lua
@@ -0,0 +1,65 @@
+-- Defualt implementation of the usermarkfunc. This default implementation is
+-- extensible and allows other plugins to register handlers for different
+-- registers.
+--
+-- The default handler behaves just as a normal register would.
+
+local vim = assert("vim")
+local usermark = {}
+
+-- Returns a "default handler" which behaves like normal global marks. When a
+-- call to set() is made, it stores the current line and col of the cursor and
+-- the filename of the current file.
+function usermark._default_handler()
+  local d = {}
+
+  -- Called when a mark is recalled using the "'" command. Just returns what was
+  -- stored before or nothing if it was never set before.
+  function d.get(self, mark)
+    return self.content or {}
+  end
+
+  -- Called when a mark is set using the "m" command. Stores the current cursor
+  -- position to be recalled at a later time.
+  function d.set(self, mark)
+    local r,c = unpack(vim.api.nvim_win_get_cursor(0))
+    local file = vim.fn.expand("%:p")
+
+    self.content = {
+      line: r,
+      col: c,
+      file: file
+    }
+  end
+
+  return d
+end
+
+-- The store for register default handler
+usermark._marktable = {}
+
+-- Function for the 'usermarkfunc'. Will defer to the handler associated with
+-- the provided mark.
+--
+-- If not handler is registered to a given mark, the default handler is used,
+-- which is a re-implementation of standard mark behavior.
+function usermark.fn(action, mark)
+  if not usermark._marktable[register] then
+    usermark._marktable[register] = usermark._default_handler()
+  end
+
+  if action == "get" then
+    usermark._marktable[register]:get(mark)
+    return nil
+  else 
+    return usermark._marktable[register]:set(mark)
+  end
+end
+
+-- Registers a handler with a mark. Gets and sets will then defer to this
+-- handler when determining the mark's behavior.
+function usermark.register_handler(register, handler) 
+  usermark._marktable[register] = handler
+end
+
+return usermark