habitica/src/app/algos.coffee

XP = 15
HP = 2

priorityValue = (priority='!') ->
  switch priority
    when '!' then 1
    when '!!' then 1.5
    when '!!!' then 2
    else 1

module.exports.tnl = (level) ->
  if level >= 100
    value = 0
  else
    value = Math.round(((Math.pow(level,2)*0.25)+(10 * level) + 139.75)/10)*10 # round to nearest 10
  return value

###
  Calculates Exp modificaiton based on level and weapon strength
  {value} task.value for exp gain
  {weaponStrength) weapon strength 
  {level} current user level
  {priority} user-defined priority multiplier
###
module.exports.expModifier = (value, weaponStr, level, priority='!') ->
  str = (level-1) / 2 # ultimately get this from user
  totalStr = (str + weaponStr) / 100
  strMod = 1 + totalStr
  exp = value * XP * strMod * priorityValue(priority)
  return Math.round(exp)

###
  Calculates HP modification based on level and armor defence
  {value} task.value for hp loss
  {armorDefense} defense from armor
  {helmDefense} defense from helm 
  {level} current user level
  {priority} user-defined priority multiplier
###
module.exports.hpModifier = (value, armorDef, helmDef, shieldDef, level, priority='!') ->
  def = (level-1) / 2 # ultimately get this from user?
  totalDef = (def + armorDef + helmDef + shieldDef) / 100 #ultimate get this from user
  defMod = 1 - totalDef
  hp = value * HP * defMod * priorityValue(priority)
  return Math.round(hp * 10)/10 # round to 1dp

###
  Future use
  {priority} user-defined priority multiplier
###
module.exports.gpModifier = (value, modifier, priority='!') ->
  return value * modifier * priorityValue(priority)

###
  Calculates the next task.value based on direction
  Uses a capped inverse log y=.95^x, y>= -5
  {currentValue} the current value of the task
  {direction} up or down
###
module.exports.taskDeltaFormula = (currentValue, direction) ->
  if currentValue < -47.27 then currentValue = -47.27
  else if currentValue > 21.27 then currentValue = 21.27
  delta = Math.pow(0.9747,currentValue)
  return delta if direction is 'up'
  return -delta