const canvas = d3.select('.canvas')
const colorInput = d3.select('#colorPicker')
const marker = d3.select('.marker')
const clearButton = d3.select('[data-clear]')
const saveButton = d3.select('[data-save]')
const undoButton = d3.select('[data-undo]')
const copyButton = d3.select('[data-copy]')
const textArea = d3.select('#css')
const drawArea = d3.select('.draw-area')
const range = d3.select('#columns')

const width = drawArea.node().offsetWidth
const height = drawArea.node().offsetHeight
let columns = 30
const multiplier = height / width
let rows = columns * multiplier
let cellSize = 100 / columns
let rowSize = 100 / rows
let isPressed = false

const bisect = d3.bisector((d) => d)

const dx = (posX) => {
  const stepX = 1 / (columns - 1)
  const dataX = d3.range(0, 100, stepX)
  const indexX = bisect.center(dataX, posX / width)
  return (dataX[indexX] * 100).toFixed(2)
}

const dy = (posY) => {
  const stepY = 1 / (rows - 1)
  const dataY = d3.range(0, 1, stepY)
  const indexY = bisect.center(dataY, posY / height)
  return (dataY[indexY] * 100).toFixed(2)
}

let bg = []
let bgPosition = []

const draw = () => {
  drawArea
    .style('background-image', bg.join(','))
    .style('background-position', bgPosition.join(','))
}

const updateText = () => {
  textArea.html(`
aspect-ratio: 4 / 3;
background-image: ${bg.join(',')};
background-size: calc(100% / ${columns}) calc(100% / ${rows});
background-position: ${bgPosition.join(',')};
background-repeat: no-repeat;
  `)
}

const shouldDraw = (newBgValue, newBgPositionValue) => {
  if (!isPressed) return false
  if (!bg.length) return true
  if (bg[0] !== newBgValue) return true
  return bgPosition[0] !== newBgPositionValue
}

canvas.on('click', (e) => {
  const color = colorInput.node().value
  const [posX, posY] = d3.pointer(e)
  const x = dx(posX)
  const y = dy(posY)
  
  bg = [ `linear-gradient(${color}, ${color})`, ...bg ]
  bgPosition = [ `${x}% ${y}%`, ...bgPosition]
  
  draw()
  updateText()
})

canvas
  .on('mouseover', () => {
    marker.style('opacity', 1)
  })
  .on('mouseout', () => {
    marker.style('opacity', 0)
  })
  .on('mousedown', () => {
    isPressed = true
  })
  .on('mouseup', () => {
    isPressed = false
  })

canvas.on('mousemove', (e) => {
  const color = colorInput.node().value
  const [posX, posY] = d3.pointer(e)
  const x = dx(posX)
  const y = dy(posY)
  
  marker
    .style('background-position', `${x}% ${y}%`)
  
  const newBgValue = `linear-gradient(${color}, ${color})`
  const newBgPositionValue = `${x}% ${y}%`
  
  if (!shouldDraw(newBgValue, newBgPositionValue)) return
  
  bg = [ newBgValue, ...bg ]
  bgPosition = [ newBgPositionValue, ...bgPosition]

  draw()
  updateText()
})

colorInput.on('input', () => {
  marker.style('--bg', colorInput.node().value)
})

const clear = () => {
  bg = []
  bgPosition = []
  textArea.html('')
  drawArea
    .style('background-image', '')
    .style('background-position', '')
    .style('background-size', '')
}

clearButton.on('click', clear)

saveButton.on('click', () => {
  const art = textArea.node().value
  localStorage.setItem('art', art)
})

const restoreSavedArt = () => {
  const savedArt = localStorage.getItem('art')
  
  if (!savedArt) return
  drawArea.attr('style', savedArt)
  textArea.html(savedArt)
}

const setColumnCount = () => {
  columns = range.node().value
  rows = columns * multiplier
  cellSize = 100 / columns
  rowSize = 100 / rows
  canvas.style('--cellSizeCol', `${cellSize}%`)
  canvas.style('--cellSizeRow', `${rowSize}%`)
  canvas.style('--colCount', columns)
}

setColumnCount()
restoreSavedArt()

window.addEventListener('resize', () => {
  if (window.innerWidth > width + 100) return
  setColumnCount()
})

range.on('input', setColumnCount)

copyButton.on('click', (e) => {
  const copyText = textArea.node()

  copyText.select()
  copyText.setSelectionRange(0, 99999)
  navigator.clipboard.writeText(copyText.value)
  copyButton.text('Copied!')
  
  setTimeout(() => {
    copyButton.text('Copy to clipboard')
  }, 3000)
})

undoButton.on('click', () => {
  bg.splice(0, 1)
  bgPosition.splice(0, 1)
  
  draw()
  updateText()
})