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local module = {}
setmetatable(module, {__index=_G})
setfenv(1, module)
--===== filters =====--
Filter = {}
-- base filter creation
function Filter.new(_, operation, tbl)
local self = {}
self.keys = {}
self.filters = {}
self.op = operation
for _, v in ipairs(tbl) do
if type(v) == "function" then
table.insert(self.filters, v)
elseif type(v) == "string" then
table.insert(self.keys, v)
end
end
return function(entity, _self)
local entity = _self or entity -- able to call as . or :
return Filter.check(self, entity)
end
end
setmetatable(Filter, {__call=Filter.new})
-- base filter checking
function Filter.check(self, entity)
local funcname = "check" .. self.op
return Filter[funcname](self, entity)
end
-- AND filter (all keys and subfilters must match)
function Filter.AND(tbl)
return Filter("AND", tbl)
end
function Filter.checkAND(self, entity)
for _, subfilter in ipairs(self.filters) do
if not subfilter(entity) then return false end
end
for _, key in ipairs(self.keys) do
if entity[key] == nil then return false end
end
return true
end
-- OR filter (at least one key or subfilter must match)
function Filter.OR(tbl)
return Filter("OR", tbl)
end
function Filter.checkOR(self, entity)
for _, subfilter in ipairs(self.filters) do
if subfilter(entity) then return true end
end
for _, key in ipairs(self.keys) do
if entity[key] ~= nil then return true end
end
return false
end
-- NAND filter (at least one key or subfilter must NOT match)
function Filter.NAND(tbl)
return Filter("NAND", tbl)
end
function Filter.checkNAND(self, entity)
for _, subfilter in ipairs(self.filters) do
if not subfilter(entity) then return true end
end
for _, key in ipairs(self.keys) do
if entity[key] == nil then return true end
end
return false
end
-- NOR filter (no keys or subfilters may match)
function Filter.NOR(tbl)
return Filter("NOR", tbl)
end
function Filter.checkNOR(self, entity)
for _, subfilter in ipairs(self.filters) do
if subfilter(entity) then return false end
end
for _, key in ipairs(self.keys) do
if entity[key] ~= nil then return false end
end
return true
end
--===== levels =====--
Level = {}
Level.__index = Level
function Level.new(_)
local self = {}
self.systems = {}
self.entities = {}
self.nextId = 1
setmetatable(self, Level)
return self
end
setmetatable(Level, {__call=Level.new})
local function systemLt(a, b)
return (a.priority or 50) < (b.priority or 50)
end
function Level.addSystem(self, system)
assert(system.update, "systems must have an 'update' key")
assert(system.filter, "systems must have a 'filter' key")
system.entities = {}
table.insert(self.systems, system)
table.sort(self.systems, systemLt)
end
local function addEntityToSystem(system, id, entity)
-- check if entity is already present
if system.entities[id] then return end
if system.onAddEntity then
system.onAddEntity(id, entity)
end
system.entities[id] = true
end
local function removeEntityFromSystem(system, id, entity)
-- check if entity is already absent
if not system.entities[id] then return end
if system.onRemoveEntity then
system.onRemoveEntity(id, entity)
end
system.entities[id] = nil
end
function Level.addEntity(self, entity)
table.insert(self.entities, entity)
local id = self.nextId
self.nextId = id + 1
for _, system in ipairs(self.systems) do
if system.filter(entity) then
addEntityToSystem(system, id, entity)
end
end
return id
end
function Level.reconfigureEntity(self, id)
local entity = self.entities[id]
for _, system in ipairs(self.systems) do
if system.filter(entity) then
addEntityToSystem(system, id, entity)
else
removeEntityFromSystem(system, id, entity)
end
end
end
function Level.removeEntity(self, id)
local entity = self.entities[id]
for _, system in ipairs(self.systems) do
removeEntityFromSystem(system, id, entity)
end
self.entities[id] = nil
end
function Level.reconfigureAllEntities(self)
for id in ipairs(self.entities) do
self:reconfigureEntity(id)
end
end
function Level.update(self, dt)
for _, system in ipairs(self.systems) do
for id in pairs(system.entities) do
local entity = self.entities[id]
system.update(entity, dt)
end
end
end
return module
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