--[[
  A simple helper intercepting commands to change gears and instead replacing everything with a simple
  R/N/P/D gearbox. 

  To use, simply add to the start `local shifter = require('shared/physics/rnpd-shifting')()`, and then
  make sure to call `shifter:update()` at your update step, and `shifter:reset()` from `script.reset`
  function.

  Feel free to copy code from this library to your script if you’d want to change anything. An example
  of extended use of these functions is available at:  
  https://github.com/ac-custom-shaders-patch/acc-lua-examples/blob/main/cars_physics/gearboxes/script_at.lua
  https://github.com/ac-custom-shaders-patch/acc-lua-examples/blob/main/cars_physics/gearboxes/script_amt.lua
]]
---@diagnostic disable

---@class RnpdShifter
---@field private _carPh ac.StateCphysCar
---@field private _programs string[] 
---@field private _hShifterMap table<integer, string>
---@field private _shiftErrorCooldown number
---@field private _prevGearRequest integer
---@field private _program string
local RnpdShifter = class('RnpdShifter')

---@type fun(cfg: nil|{extraPrograms: string[], hShifterMap: table<integer, string>}): RnpdShifter
function RnpdShifter:initialize(cfg)
  self._carPh = ac.accessCarPhysics()
  self._programs = table.chain({'R', 'N', 'P', 'D'}, cfg and cfg.extraPrograms or {})
  self._hShifterMap = cfg and cfg.hShifterMap or {[0] = 'R', [2] = 'P', [3] = 'D'}
  self._shiftErrorCooldown = -1
  self._prevGearRequest = 0 -- track gear requests from user
  self:reset()
end

---Make sure to call this function from `script.reset()`.
function RnpdShifter:reset()
  -- Switching to parking on reset
  self._program = self._carPh.gear == 0 and 'R' or self._carPh.gear == 1 and (self._carPh.speedKmh > 5 and 'N' or 'P') or 'D'
  ac.setGearLabel(self._program, false)
end

---@return 'R'|'N'|'P'|'D' @Return currently active program.
function RnpdShifter:program()
  return self._program
end

---Update state of the gearbox.
---@return boolean @Returns `true` if current program has changed.
function RnpdShifter:update()
  local shifted = false
  -- Get user gear inputs and redirect them into selecting a gear: R, N, P or D
  if car.isAIControlled then
    -- AIs are just driving forward at all times
    if self._program ~= 'D' then
      self._program = 'D'
      ac.setGearLabel(self._program, false)
      shifted = true
    end
  else
    local desiredGear = self._program
    if self._carPh.requestedGearIndex ~= -1 then
      -- Not sure if this is a good map, but I feel like if all cars would have their maps
      -- set differently, it’d be in the spirit of automatic gearboxes
      desiredGear = self._hShifterMap[self._carPh.requestedGearIndex] or 'N'
    else
      local gearRequest = self._carPh.gearUp and 1 or self._carPh.gearDown and -1 or 0
      if gearRequest ~= self._prevGearRequest then
        desiredGear = self._programs[math.clamp(table.indexOf(self._programs, self._program) + gearRequest, 1, #self._programs)]
        self._prevGearRequest = gearRequest
      end
    end
    if desiredGear and desiredGear ~= self._program then
      -- Let’s say, to change gears brakes should be pressed
      if self._carPh.brake > 0.5 and self._carPh.speedKmh < 1 then
        self._program, shifted = desiredGear, true
        ac.setGearLabel(self._program, false)
      elseif self._shiftErrorCooldown > os.preciseClock() then
        ac.setMessage('Automatic gearbox', 'Stop the car and press brakes to shift gears')
      else
        self._shiftErrorCooldown = os.preciseClock() + 1
        ac.showNotification('automaticShiftBlocked')
      end
    end
  end
  self._carPh.gearUp, self._carPh.gearDown, self._carPh.requestedGearIndex = false, false, -1
  return shifted
end

return class.emmy(RnpdShifter, RnpdShifter.initialize)