1 files changed, 274 insertions, 0 deletions
diff --git a/honey/ecs/ecs.lua b/honey/ecs/ecs.lua
new file mode 100644
index 0000000..b0409e4
--- /dev/null
+++ b/honey/ecs/ecs.lua
@@ -0,0 +1,274 @@
+math.randomseed(os.time())
+
+local glm = require 'honey.glm'
+
+local module = {}
+setmetatable(module, {__index=_G})
+setfenv(1, module)
+
+
+--===== EntityDb =====--
+
+
+-- EntityDb is a database of entities and their associated components
+-- it should be quite efficient to query for all entities with a given component, and reasonably
+-- efficient to query for all components of a given entity
+
+
+EntityDb = {}
+EntityDb.__index = EntityDb
+
+
+function EntityDb.new(_)
+	local self = {
+		entities = {},
+		components = {},
+	}
+	setmetatable(self, EntityDb)
+	return self
+end
+setmetatable(EntityDb, {__call=EntityDb.new})
+
+
+local function serialize(tbl)
+	local tostr = function(x, value)
+		if type(x) == "table" then
+			if x.__tostring then
+				return tostring(x)
+			else
+				return serialize(x)
+			end
+		elseif type(x) == "string" then
+			if value then
+				return string.format("\"%s\"", x)
+			else
+				return x
+			end
+		else
+			return tostring(x)
+		end
+	end
+	local str = "{"
+	for key, value in pairs(tbl) do
+		if type(key) == "string" and string.match(key, "^_") then
+			-- ignore keys starting with an underscore
+		else
+			str = str .. string.format("%s=%s,", tostr(key), tostr(value, true))
+		end
+	end
+	str = string.sub(str, 1, -2) .. "}"
+	return str
+end
+
+
+-- save current database to file
+function EntityDb.save(self, filename)
+	local file, err = io.open(filename, "w")
+	if not file then error(err) end
+
+	for entity in pairs(self.entities) do
+		local components = self:queryEntity(entity)
+		file:write(string.format("Entity(\"%s\", %s)\n", entity, serialize(components)))
+	end
+
+	file:close()
+end
+
+
+-- load database from file
+function EntityDb.load(self, filename)
+	print(collectgarbage("count"))
+	self.entities = {}
+	self.components = {}
+	collectgarbage()
+	print(collectgarbage("count"))
+	local env = {
+		Entity = function(id, components)
+			self:createEntity(id)
+			self:addComponents(id, components)
+		end,
+		Vec3 = glm.Vec3,
+		Mat4 = glm.Mat4,
+	}
+	local f, err = loadfile(filename)
+	if not f then error(err) end
+	setfenv(f, env)
+	f()
+end
+
+
+-- check if a given entity id is legitimate
+function EntityDb.checkIsValid(self, id)
+	if not self.entities[id] then
+		error(string.format("invalid entity id: %s", tostring(id)))
+	end
+end
+
+
+local random = math.random
+local function uuid()
+	local template ='xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'
+	return string.gsub(template, '[xy]', function (c)
+		local v = (c == 'x') and random(0, 0xf) or random(8, 0xb)
+		return string.format('%x', v)
+	end)
+end
+
+
+-- create a new entity
+function EntityDb.createEntity(self, id)
+	local id = id or uuid() -- allow inserting entities at preset ids for loading
+	self.entities[id] = true
+	return id
+end
+
+
+-- add a component to an entity
+function EntityDb.addComponent(self, id, name, value)
+	self:checkIsValid(id)
+	
+	-- create the relevant component table if it doesn't exist
+	if not self.components[name] then
+		self.components[name] = { count=0, data={} }
+	end
+
+	local component = self.components[name]
+	component.data[id] = value
+	component.count = component.count + 1
+end
+
+
+-- add multiple components at once, for convenience
+function EntityDb.addComponents(self, id, components)
+	for name, value in pairs(components) do
+		self:addComponent(id, name, value)
+	end
+end
+
+
+-- create an entity with components
+function EntityDb.createEntityWithComponents(self, components)
+	local id = self:createEntity()
+	self:addComponents(id, components)
+	return id
+end
+
+
+-- get all entities with a given component
+function EntityDb.queryComponent(self, name)
+	local component = self.components[name]
+	if component then 
+		return component.data
+	else
+		return {}
+	end
+end
+
+
+-- get all components associated with an entity
+function EntityDb.queryEntity(self, id)
+	self:checkIsValid(id)
+	local query = {}
+	for name, component in pairs(self.components) do
+		query[name] = component.data[id]
+	end
+	return query
+end
+
+
+-- get a specific component from an entity
+function EntityDb.getComponent(self, id, name)
+	self:checkIsValid(id)
+	return self.components[name].data[id]
+end
+
+
+-- remove a component from an entity
+function EntityDb.removeComponent(self, id, name)
+	self:checkIsValid(id)
+	local component = self.components[name]
+	if component.data[id] ~= nil then
+		component.data[id] = nil
+		component.count = component.count - 1
+		if component.count == 0 then
+			self.components[name] = nil
+		end
+	end
+end
+
+
+-- remove an entity from the db
+function EntityDb.deleteEntity(self, id)
+	self:checkIsValid(id)
+	for name in pairs(self.components) do
+		self:removeComponent(id, name)
+	end
+	self.entities[id] = nil
+end
+
+
+--===== SystemDb =====--
+
+SystemDb = {}
+SystemDb.__index = SystemDb
+
+
+function SystemDb.new(_, entityDb)
+	local self = {
+		systems = {},
+		sorted = {},
+		entityDb = entityDb,
+	}
+	setmetatable(self, SystemDb)
+	return self
+end
+setmetatable(SystemDb, {__call=SystemDb.new})
+
+
+local function systemId()
+	local template = "xx:xx:xx"
+	return string.gsub(template, "x", function(c)
+		return string.format("%x", random(0, 0xf))
+	end)
+end
+
+
+function SystemDb.addSystem(self, systemFunc, params)
+	local system
+	if type(systemFunc) == "table" then
+		system = systemFunc
+	else
+		local params = params or {}
+		params.db = self.entityDb
+		system = systemFunc(params)
+	end
+
+	local id = systemId()
+	self.systems[id] = system
+	table.insert(self.sorted, id)
+	self:sort()
+	return id
+end
+
+
+function SystemDb.sort(self)
+	table.sort(self.sorted, function(a, b) return (self.systems[a].priority or 100) < (self.systems[b].priority or 100) end)
+end
+
+
+function SystemDb.update(self, dt)
+	for _, system in ipairs(self.sorted) do
+		self.systems[system]:update(dt)
+	end
+end
+
+
+function SystemDb.removeSystem(self, id)
+	self.systems[id] = nil
+	for i=#self.sorted,1,-1 do
+		if self.sorted[i] == id then table.remove(self.sorted, i) end
+	end
+end
+
+
+return module