entityPool.lua

-- Services
local replicatedStorage = game:GetService("ReplicatedStorage")

local shared = replicatedStorage.shared

local sharedLib = shared.lib
local signalLib = require(sharedLib.signalLib)

local entityPool = {}
entityPool.entities = {}
entityPool.componentEntityMap = {}
entityPool.serialEntityCount = 0

-- Accepts a tuple of components that are registered to on construction.
function entityPool.createEntity(componentName, componentDataCollection)
    entityPool.serialEntityCount = entityPool.serialEntityCount + 1

    local entityId = entityPool.serialEntityCount

    entityPool.entities[entityId] = {} -- Associative array containing all components associated with entity.

    for _, componentData in pairs(componentDataCollection) do
        entityPool.addComponentToEntity(entityId, componentName, componentData)
    end

    return entityId
end

function entityPool.getEntityById(entityId)
    return entityPool.entities[entityId]
end

function entityPool.removeEntity(entityId)
    if not entityPool.entities[entityId] then return end

    entityPool.serialEntityCount = entityPool.serialEntityCount - 1

    -- Reference is found in various places in component entity map, remove to ensure gc.
    for componentName in pairs(entityPool.entities[entityId]) do
        entityPool.componentEntityMap[componentName][entityId] = nil
    end

    entityPool.entities[entityId] = nil
end

function entityPool.addComponentToEntity(entityId, componentName, componentData)
    local entityComponentCollection = entityPool.entities[entityId]
    if not entityComponentCollection then return end

    entityComponentCollection[componentName] = componentData

    if not entityPool.componentEntityMap[componentName] then
        entityPool.componentEntityMap[componentName] = {}
        warn("System for " .. componentName .. " has not yet been constructed")
        print("Adding field to componentEntityMap for above component")
    end

    entityPool.componentEntityMap[componentName][entityId] = componentData
    print(entityComponentCollection[componentName], entityPool.componentEntityMap[componentName][entityId])

    signalLib.dispatchAsync("componentAttached", componentName, entityId)
end

function entityPool.removeComponentFromEntity(entityId, componentName)
    local entityComponentCollection = entityPool.entities[entityId]
    if not entityComponentCollection then return end

    entityComponentCollection[componentName] = nil
    entityPool.componentEntityMap[componentName][entityId] = nil

    signalLib.dispatchAsync("componentDetached", componentName, entityId)
end

return entityPool