/**
 * {}
 * @author yutent<yutent.io@gmail.com>
 * @date 2024/03/07 15:17:00
 */

import eve from './eve.js'

let operators = {
    '+': function (x, y) {
      return x + y
    },
    '-': function (x, y) {
      return x - y
    },
    '/': function (x, y) {
      return x / y
    },
    '*': function (x, y) {
      return x * y
    }
  },
  reUnit = /[a-z]+$/i,
  reAddon = /^\s*([+\-\/*])\s*=\s*([\d.eE+\-]+)\s*([^\d\s]+)?\s*$/

function getUnit(unit) {
  return function (val) {
    return +val.toFixed(3) + unit
  }
}
eve.on('snap.util.attr', function (val) {
  let plus = String(val).match(reAddon)
  if (plus) {
    let evnt = eve.nt(),
      name = evnt.substring(evnt.lastIndexOf('.') + 1),
      a = this.attr(name),
      atr = {}
    eve.stop()
    let unit = plus[3] || '',
      aUnit = a.match(reUnit),
      op = operators[plus[1]]
    if (aUnit && aUnit == unit) {
      val = op(+a, +plus[2])
    } else {
      a = this.asPX(name)
      val = op(this.asPX(name), this.asPX(name, plus[2] + unit))
    }
    if (isNaN(a) || isNaN(val)) {
      return
    }
    atr[name] = val
    this.attr(atr)
  }
})(-10)

eve.on('snap.util.equal', function (name, b) {
  let a = String(this.attr(name) || '')
  let bplus = String(b).match(reAddon)

  if (bplus) {
    eve.stop()
    let unit = bplus[3] || '',
      aUnit = a.match(reUnit),
      op = operators[bplus[1]]
    if (aUnit && aUnit === unit) {
      return {
        from: +a,
        to: op(+a, +bplus[2]),
        f: getUnit(aUnit)
      }
    } else {
      a = this.asPX(name)
      return {
        from: a,
        to: op(a, this.asPX(name, bplus[2] + unit)),
        f: _ => _
      }
    }
  }
})(-10)