var size = require('element-size')

module.exports = fit

var scratch = new Float32Array(2)

function fit(canvas, parent, scale) {
  var isSVG = canvas.nodeName.toUpperCase() === 'SVG'

  canvas.style.position = canvas.style.position || 'absolute'
  canvas.style.top = 0
  canvas.style.left = 0

  resize.scale  = parseFloat(scale || 1)
  resize.parent = parent

  return resize()

  function resize() {
    var p = resize.parent || canvas.parentNode
    if (typeof p === 'function') {
      var dims   = p(scratch) || scratch
      var width  = dims[0]
      var height = dims[1]
    } else
    if (p && p !== document.body) {
      var psize  = size(p)
      var width  = psize[0]|0
      var height = psize[1]|0
    } else {
      var width  = window.innerWidth
      var height = window.innerHeight
    }

    if (isSVG) {
      canvas.setAttribute('width', width * resize.scale + 'px')
      canvas.setAttribute('height', height * resize.scale + 'px')
    } else {
      canvas.width = width * resize.scale
      canvas.height = height * resize.scale
    }

    canvas.style.width = width + 'px'
    canvas.style.height = height + 'px'

    return resize
  }
}