implement condition objects

Author: atticus-sullivan

lua/luasnip/extras/expand_conditions.lua

@@ -1,13 +1,62 @@
 local M = {}
 
-function M.line_begin(line_to_cursor, matched_trigger)
+-----------------------
+-- CONDITION OBJECTS --
+-----------------------
+local condition_mt = {
+	-- logic operators
+	-- not '~'
+	__unm = function(o1)
+		return function(...)
+			return not o1(...)
+		end
+	end,
+	-- or '+'
+	__add = function(o1, o2)
+		return function(...)
+			return o1(...) or o2(...)
+		end
+	end,
+	-- and '*'
+	__mul = function(o1, o2)
+		return function(...)
+			return o1(...) and o2(...)
+		end
+	end,
+	-- xor '^'
+	__pow = function(o1, o2)
+		return function(...)
+			return o1(...) ~= o2(...)
+		end
+	end,
+	-- xnor '=='
+	__eq = function(o1, o2)
+		return function(...)
+			return o1(...) == o2(...)
+		end
+	end,
+	-- use table like a function by overloading __call
+	__call = function(tab, line_to_cursor, matched_trigger, captures)
+		return tab.func(line_to_cursor, matched_trigger, captures)
+	end,
+}
+function M.condition_factory(func)
+	return setmetatable({func=func}, condition_mt)
+end
+
+-----------------------
+-- PRESET CONDITIONS --
+-----------------------
+local function line_begin(line_to_cursor, matched_trigger)
 	-- +1 because `string.sub("abcd", 1, -2)` -> abc
 	return line_to_cursor:sub(1, -(#matched_trigger + 1)):match("^%s*$")
 end
+M.line_begin = M.condition_factory(line_begin)
 
-function M.line_end(line_to_cursor)
+local function line_end(line_to_cursor)
 	local line = vim.api.nvim_get_current_line()
 	return #line_to_cursor == #line
 end
+M.line_end   = M.condition_factory(line_end)
 
 return M