const reRGBA = /^rgb(a)?\((\d{1,3}),(\d{1,3}),(\d{1,3}),?([01]?\.?\d*?)?\)$/

export function rgbToHex({ r, g, b, a }) {
  const alpha = a !== void 0

  r = Math.round(r)
  g = Math.round(g)
  b = Math.round(b)

  if (r > 255 || g > 255 || b > 255 || (alpha && a > 100)) {
    throw new TypeError(
      'Expected 3 numbers below 256 (and optionally one below 100)'
    )
  }

  a = alpha
    ? (Math.round((255 * a) / 100) | (1 << 8)).toString(16).slice(1)
    : ''

  return '#' + (b | (g << 8) | (r << 16) | (1 << 24)).toString(16).slice(1) + a
}

export function rgbToString({ r, g, b, a }) {
  return `rgb${a !== void 0 ? 'a' : ''}(${r},${g},${b}${a !== void 0 ? ',' + a / 100 : ''})`
}

export function hexToRgb(hex) {
  if (typeof hex !== 'string') {
    throw new TypeError('Expected a string')
  }

  hex = hex.replace(/^#/, '')

  if (hex.length === 3) {
    hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2]
  } else if (hex.length === 4) {
    hex = hex[0] + hex[0] + hex[1] + hex[1] + hex[2] + hex[2] + hex[3] + hex[3]
  }

  const num = parseInt(hex, 16)

  return hex.length > 6
    ? {
        r: (num >> 24) & 255,
        g: (num >> 16) & 255,
        b: (num >> 8) & 255,
        a: Math.round((num & 255) / 2.55)
      }
    : { r: num >> 16, g: (num >> 8) & 255, b: num & 255 }
}

export function hsvToRgb({ h, s, v, a }) {
  let r, g, b
  s = s / 100
  v = v / 100

  h = h / 360
  const i = Math.floor(h * 6),
    f = h * 6 - i,
    p = v * (1 - s),
    q = v * (1 - f * s),
    t = v * (1 - (1 - f) * s)

  switch (i % 6) {
    case 0:
      r = v
      g = t
      b = p
      break
    case 1:
      r = q
      g = v
      b = p
      break
    case 2:
      r = p
      g = v
      b = t
      break
    case 3:
      r = p
      g = q
      b = v
      break
    case 4:
      r = t
      g = p
      b = v
      break
    case 5:
      r = v
      g = p
      b = q
      break
  }

  return {
    r: Math.round(r * 255),
    g: Math.round(g * 255),
    b: Math.round(b * 255),
    a
  }
}

export function rgbToHsv({ r, g, b, a }) {
  const max = Math.max(r, g, b),
    min = Math.min(r, g, b),
    d = max - min,
    s = max === 0 ? 0 : d / max,
    v = max / 255
  let h

  switch (max) {
    case min:
      h = 0
      break
    case r:
      h = g - b + d * (g < b ? 6 : 0)
      h /= 6 * d
      break
    case g:
      h = b - r + d * 2
      h /= 6 * d
      break
    case b:
      h = r - g + d * 4
      h /= 6 * d
      break
  }

  return {
    h: Math.round(h * 360),
    s: Math.round(s * 100),
    v: Math.round(v * 100),
    a
  }
}

export function textToRgb(str) {
  if (typeof str !== 'string') {
    throw new TypeError('Expected a string')
  }

  const color = str.replace(/ /g, '')

  const m = reRGBA.exec(color)

  if (m === null) {
    return hexToRgb(color)
  }

  const rgb = {
    r: Math.min(255, parseInt(m[2], 10)),
    g: Math.min(255, parseInt(m[3], 10)),
    b: Math.min(255, parseInt(m[4], 10))
  }

  if (m[1]) {
    const alpha = parseFloat(m[5])
    rgb.a = Math.min(1, isNaN(alpha) === true ? 1 : alpha) * 100
  }

  return rgb
}

/* works as darken if percent < 0 */
export function lighten(color, percent) {
  if (typeof color !== 'string') {
    throw new TypeError('Expected a string as color')
  }
  if (typeof percent !== 'number') {
    throw new TypeError('Expected a numeric percent')
  }

  const rgb = textToRgb(color),
    t = percent < 0 ? 0 : 255,
    p = Math.abs(percent) / 100,
    R = rgb.r,
    G = rgb.g,
    B = rgb.b

  return (
    '#' +
    (
      0x1000000 +
      (Math.round((t - R) * p) + R) * 0x10000 +
      (Math.round((t - G) * p) + G) * 0x100 +
      (Math.round((t - B) * p) + B)
    )
      .toString(16)
      .slice(1)
  )
}

export function luminosity(color) {
  if (typeof color !== 'string' && (!color || color.r === void 0)) {
    throw new TypeError('Expected a string or a {r, g, b} object as color')
  }

  const rgb = typeof color === 'string' ? textToRgb(color) : color,
    r = rgb.r / 255,
    g = rgb.g / 255,
    b = rgb.b / 255,
    R = r <= 0.03928 ? r / 12.92 : ((r + 0.055) / 1.055) ** 2.4,
    G = g <= 0.03928 ? g / 12.92 : ((g + 0.055) / 1.055) ** 2.4,
    B = b <= 0.03928 ? b / 12.92 : ((b + 0.055) / 1.055) ** 2.4
  return 0.2126 * R + 0.7152 * G + 0.0722 * B
}

export function brightness(color) {
  if (typeof color !== 'string' && (!color || color.r === void 0)) {
    throw new TypeError('Expected a string or a {r, g, b} object as color')
  }

  const rgb = typeof color === 'string' ? textToRgb(color) : color

  return (rgb.r * 299 + rgb.g * 587 + rgb.b * 114) / 1000
}

export function blend(fgColor, bgColor) {
  if (typeof fgColor !== 'string' && (!fgColor || fgColor.r === void 0)) {
    throw new TypeError(
      'Expected a string or a {r, g, b[, a]} object as fgColor'
    )
  }

  if (typeof bgColor !== 'string' && (!bgColor || bgColor.r === void 0)) {
    throw new TypeError(
      'Expected a string or a {r, g, b[, a]} object as bgColor'
    )
  }

  const rgb1 = typeof fgColor === 'string' ? textToRgb(fgColor) : fgColor,
    r1 = rgb1.r / 255,
    g1 = rgb1.g / 255,
    b1 = rgb1.b / 255,
    a1 = rgb1.a !== void 0 ? rgb1.a / 100 : 1,
    rgb2 = typeof bgColor === 'string' ? textToRgb(bgColor) : bgColor,
    r2 = rgb2.r / 255,
    g2 = rgb2.g / 255,
    b2 = rgb2.b / 255,
    a2 = rgb2.a !== void 0 ? rgb2.a / 100 : 1,
    a = a1 + a2 * (1 - a1),
    r = Math.round(((r1 * a1 + r2 * a2 * (1 - a1)) / a) * 255),
    g = Math.round(((g1 * a1 + g2 * a2 * (1 - a1)) / a) * 255),
    b = Math.round(((b1 * a1 + b2 * a2 * (1 - a1)) / a) * 255)

  const ret = { r, g, b, a: Math.round(a * 100) }
  return typeof fgColor === 'string' ? rgbToHex(ret) : ret
}

export function changeAlpha(color, offset) {
  if (typeof color !== 'string') {
    throw new TypeError('Expected a string as color')
  }

  if (offset === void 0 || offset < -1 || offset > 1) {
    throw new TypeError('Expected offset to be between -1 and 1')
  }

  const { r, g, b, a } = textToRgb(color)
  const alpha = a !== void 0 ? a / 100 : 0

  return rgbToHex({
    r,
    g,
    b,
    a: Math.round(Math.min(1, Math.max(0, alpha + offset)) * 100)
  })
}

export function getPaletteColor(colorName) {
  if (typeof colorName !== 'string') {
    throw new TypeError('Expected a string as color')
  }

  const el = document.createElement('div')

  el.className = `text-${colorName} invisible fixed no-pointer-events`
  document.body.appendChild(el)

  const result = getComputedStyle(el).getPropertyValue('color')

  el.remove()

  return rgbToHex(textToRgb(result))
}

export default {
  rgbToHex,
  hexToRgb,
  hsvToRgb,
  rgbToHsv,
  textToRgb,
  lighten,
  luminosity,
  brightness,
  blend,
  changeAlpha,
  getPaletteColor
}
