Add Component Negation

Fixes #32

concord/component.lua

@@ -19,6 +19,10 @@ function Component.new(name, populate)
       error("bad argument #1 to 'Component.new' (string expected, got "..type(name)..")", 2)
    end
 
+   if (string.match(name, Components.__REJECT_MATCH) ~= "") then
+      error("bad argument #1 to 'Component.new' (Component names can't start with '"..Components.__REJECT_PREFIX.."', got "..name..")", 2)
+   end
+
    if (rawget(Components, name)) then
       error("bad argument #1 to 'Component.new' (ComponentClass with name '"..name.."' was already registerd)", 2) -- luacheck: ignore
    end

concord/components.lua

@@ -1,12 +1,11 @@
 --- Container for registered ComponentClasses
 -- @module Components
 
-local PATH = (...):gsub('%.[^%.]+$', '')
-
-local Type = require(PATH..".type")
-
 local Components = {}
 
+Components.__REJECT_PREFIX = "!"
+Components.__REJECT_MATCH = "^(%"..Components.__REJECT_PREFIX.."?)(.+)"
+
 --- Returns true if the containter has the ComponentClass with the specified name
 -- @string name Name of the ComponentClass to check
 -- @treturn boolean
@@ -14,22 +13,43 @@ function Components.has(name)
    return rawget(Components, name) and true or false
 end
 
+--- Prefix a component's name with the currently set Reject Prefix
+-- @string name Name of the ComponentClass to reject
+-- @treturn string
+function Components.reject(name)
+   local ok, err = Components.try(name)
+
+   if not ok then error(err, 2) end
+
+   return Components.__REJECT_PREFIX..name
+end
+
 --- Returns true and the ComponentClass if one was registered with the specified name
 -- or false and an error otherwise
 -- @string name Name of the ComponentClass to check
+-- @boolean acceptRejected Whether to accept names prefixed with the Reject Prefix.
 -- @treturn boolean
 -- @treturn Component or error string
-function Components.try(name)
+-- @treturn true if acceptRejected was true and the name had the Reject Prefix, false otherwise.
+function Components.try(name, acceptRejected)
    if type(name) ~= "string" then
       return false, "ComponentsClass name is expected to be a string, got "..type(name)..")"
    end
 
+   local rejected = false
+   if acceptRejected then
+      local prefix
+      prefix, name = string.match(name, Components.__REJECT_MATCH)
+
+      rejected = prefix ~= "" and name
+   end
+
    local value = rawget(Components, name)
    if not value then
       return false, "ComponentClass '"..name.."' does not exist / was not registered"
    end
 
-   return true, value
+   return true, value, rejected
 end
 
 --- Returns the ComponentClass with the specified name

concord/pool.lua

@@ -30,10 +30,14 @@ end
 -- @tparam Entity e Entity to check
 -- @treturn boolean
 function Pool:eligible(e)
-   for i=#self.__filter, 1, -1 do
-      local component = self.__filter[i].__name
+   for i=#self.__filter.require, 1, -1 do
+      local name = self.__filter.require[i]
+      if not e[name] then return false end
+   end
 
-      if not e[component] then return false end
+   for i=#self.__filter.reject, 1, -1 do
+      local name = self.__filter.reject[i]
+      if e[name] then return false end
    end
 
    return true

concord/system.lua

@@ -33,7 +33,7 @@ System.mt = {
          Utils.shallowCopy(systemClass, system)
       end
 
-      for name, filter in pairs(systemClass.__filter) do
+      for name, filter in pairs(systemClass.__filters) do
          local pool = Pool(name, filter)
 
          system[name] = pool
@@ -46,10 +46,10 @@ System.mt = {
    end,
 }
 
-local validateFilters = function (baseFilters)
+local validateFilters = function (definition)
    local filters = {}
 
-   for name, componentsList in pairs(baseFilters) do
+   for name, componentsList in pairs(definition) do
       if type(name) ~= 'string' then
          error("invalid name for filter (string key expected, got "..type(name)..")", 3)
       end
@@ -58,18 +58,19 @@ local validateFilters = function (baseFilters)
          error("invalid component list for filter '"..name.."' (table expected, got "..type(componentsList)..")", 3)
       end
 
-      local filter = {}
+      filters[name] = { require = {}, reject = {} }
+
       for n, component in ipairs(componentsList) do
-         local ok, componentClass = Components.try(component)
+         local ok, componentClass, rejected = Components.try(component, true)
 
          if not ok then
             error("invalid component for filter '"..name.."' at position #"..n.." ("..componentClass..")", 3)
+         elseif rejected then
+            table.insert(filters[name].reject, rejected)
+         else
+            table.insert(filters[name].require, component)
          end
-
-         filter[#filter + 1] = componentClass
       end
-
-      filters[name] = filter
    end
 
    return filters
@@ -78,9 +79,11 @@ end
 --- Creates a new SystemClass.
 -- @param table filters A table containing filters (name = {components...})
 -- @treturn System A new SystemClass
-function System.new(filters)
+function System.new(definition)
+   local filters = validateFilters(definition)
+
    local systemClass = setmetatable({
-      __filter = validateFilters(filters),
+      __filters = filters,
 
       __name          = nil,
       __isSystemClass = true,