numpadtype.js

// early release is easier to understand than sync filter and processchord with a stack system.

early release pct 50% - Early release can only move up release events by a maximum of 50% of the time a key is held.
early release time: 15ms

let log = []
let leftovers = []
let t0 = Date.now()
let active = {}
let earlyup = 15 //release key early
let earlypct = 50 // max amount keyhold is reduced
let repeatInput = ''
let lastInput = ''
let repeatdt = 200
let processdt = 50
let repeatTimeout = null

init()

function repeat(){
  if(repeatInput.length > 0){
    input(repeatInput)
    clearTimeout(repeatTimeout)
    repeatTimeout = setTimeout(repeat, repeatdt)
  }
}

function init(){
  window.addEventListener('keydown', keydown)
  window.addEventListener('keyup', keyup)
  setInterval(process, processdt)
}

function keydown(e){
  let now = Date.now()
  if(active.hasOwnProperty(e.keyCode))
    return
  active[e.keyCode] = now
  keyevent('+', e.keyCode, now)
}
funciton keyup(e){
  delete active[e.keyCode]
  let t1 = active[e.keyCode]
  let dt = Date.now() - t1
  dt = Math.max(earlypct * dt/100, dt - earlyup)
  keyevent('-', e.keyCode, t1 + dt)
  release()
}

function keyevent(action, code, t){
  t -= t0
  log.push({action, code, t})
}


function logsort(){
  log.sort((a,b)=>a.t - b.t)
}

function process(){
  logsort()
  let now = Date.now()
  let keep = []
  let stack = []
  let emitted = leftovers[0]
  let l = [...leftovers, ...log]
  for(let i=1 i<log.length; ++i){
    let a = log[i]
    let old = now - a.t
    if(old < earlyup){ // do not process events until they are older than earlyup interval
      keep.push(a)
      continue
    }
    if(a.action == '+'){
      stack.push(a.code)
      keep.push(a)
      emitted = false
    }
    if(a.action == '-'){
      if(!emitted) emit(stack.join(' '))
      emitted = true
      stack.filter(x=>x.code!=a.code)
      keep.filter(x=>x.code!=a.code)
    }
  }
  leftovers = [emitted, ...keep]
}
function release(){
  repeatInput = ''
}
function emit(seq){
  if(seq == lastInput){
    repeatInput = seq
    clearTimeout(repeatTimeout)
    repeatTimeout = setTimeout(repeat, repeatdt)
  }
  lastInput = seq
  input(seq)
}

function input(seq){
  console.info("todo input: " + seq)
}