game/game/lib/reoof/pool.lua

local insert = table.insert
local remove = table.remove

local classic = require("lib.classic.classic")


---@class Pool : lib.classic.class
---@field private fn function
---@field private rfn function
---@field private efn function
---@field active any[]
---@field hidden any[]
---@field max number | nil
---@field name string
local pool = classic:extend()
pool._VERSION = "0.0.0-alpha"
pool._DESCRIPTION = "A simple and straightforward pool made for LÖVE."
pool._URL = "https://github.com/FNicon/reoof"
pool._LICENSE = [[
  MIT License

  Copyright (c) 2025 FNicon

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
]]

--- default equal function
---@param v1 any
---@param v2 any
local function defaultEqual(v1, v2)
  return v1 == v2
end

--- Return the first index with the given value (or nil if not found).
---@param array any[]
---@param value any
---@param efn fun(...):boolean
---@return number?
local function indexOf(array, value, efn)
  for i, v in pairs(array) do
    if efn(v, value) then
      return i
    end
  end
  return nil
end

--- initialize pool
---@param fn fun(...):any generate Function
---@param rfn fun(...):any reset Function
---@param name? string for debug purposes
---@param max? number pool max size
---@param efn? fun(...):boolean equal Function
---@return Pool self
function pool:new(fn, rfn, name, max, efn)
  -- local self = setmetatable({}, pool)
  self.active = {}
  self.hidden = {}
  self.fn = fn
  self.rfn = rfn
  self.efn = efn or defaultEqual
  self.max = max > 0 and max or nil
  self.name = name or "pool"
  return self
end

--- put entity to pool
---@param self Pool
---@param entity any
---@return Pool
---@return number hidden_idx index from hidden pool
function pool:put(entity)
  local idx = indexOf(self.active, entity, self.efn)
  if (idx) then
    self:put_to(entity, idx)
    return self, #self.hidden
  else
    print("WARNING : trying to insert entity not from generate function")
    return self, -1
  end
end

--- put entity to pool
---@param self Pool
---@param entity any
---@param idx number
---@return Pool
---@return number hidden_idx index from hidden pool
function pool:put_to(entity, idx)
  if (self.max) then
    if (#self.hidden < self.max) then
      insert(self.hidden, entity)
    else
      self:release(entity)
    end
  else
    insert(self.hidden, entity)
  end
  remove(self.active, idx)
  return self, #self.hidden
end

--- get entity from pool
---@param self Pool
---@param ... any
---@return any entity from pool
---@return number active_idx
function pool:get(...)
  local entity = self.hidden[#self.hidden]
  if (entity) then
    insert(self.active, entity)
    remove(self.hidden, #self.hidden)
    self.rfn(entity, ...)
    return entity, #self.active
  else
    entity = self.fn(...)
    insert(self.active, entity)
    return entity, #self.active
  end
end

--- release function
---@param self Pool
---@param entity? any
function pool:release(entity)
  if (entity == nil) then
    for _, v in pairs(self.active) do
      self:release(v)
    end
    for _, v in pairs(self.hidden) do
      self:release(v)
    end
    self.active = nil
    self.hidden = nil
    self.fn = nil
    self.rfn = nil
    self.efn = nil
    self.name = nil
    setmetatable(self, nil)
    self = nil
  else
    local idx = indexOf(self.active, entity, self.efn)
    if (idx) then
      self:release_from("active", idx)
    else
      idx = indexOf(self.hidden, entity, self.efn)
      if (idx) then
        self:release_from("hidden", idx)
      else
        print("WARNING : trying to release object not from generate function")
      end
    end
  end
end

--- release function
---@param self Pool
---@param from_pool "hidden" | "active"
---@param idx number
function pool:release_from(from_pool, idx)
  if (from_pool == "hidden") then
    if (self.hidden[idx].release) then
      self.hidden[idx]:release()
      remove(self.hidden, idx)
    else
      print("WARNING : during release hidden, %d don't have release function", idx)
    end
  else
    if (self.active[idx].release) then
      self.active[idx]:release()
      remove(self.active, idx)
    else
      print("WARNING : during release active, %d don't have release function", idx)
    end
  end
end

return pool