import { ref, nextTick } from 'vue'
import QRCode from 'qrcode'

const BASE_QR_SIZE = 256
const MAX_WIDTH_RATIO = 0.8
const MIN_SCALE = 0.5
const SCALE_STEP = 0.1

export function useQrCode() {
  const textInput = ref('')
  const error = ref('')
  const errorColor = ref('red')
  const scale = ref(1)
  const hasQr = ref(false)
  const qrCanvasRef = ref(null)
  const qrFrameRef = ref(null)

  function logMessage(message, color = 'red') {
    error.value = message
    errorColor.value = color
  }

  function getFrameWidth() {
    return qrFrameRef.value?.getBoundingClientRect().width ?? 0
  }

  function getMaxWidth() {
    return window.innerWidth * MAX_WIDTH_RATIO
  }

  function persistScale() {
    localStorage.setItem('scale', String(scale.value))
  }

  async function renderQrCanvas() {
    const canvas = qrCanvasRef.value
    const userText = textInput.value.trim()
    if (!canvas || !userText) return

    const width = Math.round(BASE_QR_SIZE * scale.value)
    await QRCode.toCanvas(canvas, userText, { width })
  }

  async function clampScaleIfNeeded() {
    await nextTick()
    if (getFrameWidth() > getMaxWidth()) {
      scale.value = 1
      persistScale()
      await renderQrCanvas()
    }
  }

  async function generateQR() {
    const userText = textInput.value.trim()
    if (!userText) {
      logMessage('Введите текст для генерации QR-кода!')
      return
    }

    localStorage.setItem('userText', userText)
    hasQr.value = true

    await nextTick()

    try {
      await renderQrCanvas()
      logMessage('')
      await clampScaleIfNeeded()
    } catch (err) {
      console.error(err)
      logMessage('Ошибка при генерации QR-кода.')
      hasQr.value = false
    }
  }

  function downloadQR() {
    const userText = textInput.value.slice(0, 20)
    const canvas = qrCanvasRef.value

    if (!canvas) {
      logMessage('QR-код не сгенерирован!')
      return
    }
    if (!userText) {
      logMessage('Отсутствует текст в поле для ввода')
      return
    }

    const link = document.createElement('a')
    link.href = canvas.toDataURL('image/png')
    link.download = `qr-code-${userText}.png`
    link.click()
    logMessage('QR-код скачан!', 'green')
  }

  function clearQR() {
    textInput.value = ''
    hasQr.value = false
    error.value = ''
    scale.value = 1
    localStorage.removeItem('userText')
    localStorage.removeItem('scale')
  }

  function closeQrModal() {
    hasQr.value = false
  }

  async function zoomIn() {
    if (!qrFrameRef.value || !textInput.value.trim()) {
      logMessage('До генерации QR кода маштаб менять нельзя')
      return
    }

    const previousScale = scale.value
    scale.value += SCALE_STEP
    await renderQrCanvas()
    await nextTick()

    if (getFrameWidth() > getMaxWidth()) {
      scale.value = previousScale
      await renderQrCanvas()
      logMessage('Достигнут максимальный размер QR кода')
      return
    }

    persistScale()
    logMessage('')
  }

  async function zoomOut() {
    if (!qrFrameRef.value || !textInput.value.trim()) {
      logMessage('До генерации QR кода маштаб менять нельзя')
      return
    }

    if (scale.value <= MIN_SCALE) {
      logMessage('Достигнут минимальный размер QR кода')
      return
    }

    scale.value -= SCALE_STEP
    await renderQrCanvas()
    persistScale()
    logMessage('')
  }

  async function restoreFromStorage() {
    const savedScale = localStorage.getItem('scale')
    if (savedScale) {
      scale.value = Number(savedScale)
    }

    const savedText = localStorage.getItem('userText')
    if (savedText) {
      textInput.value = savedText
      await generateQR()
    }
  }

  return {
    textInput,
    error,
    errorColor,
    hasQr,
    qrCanvasRef,
    qrFrameRef,
    generateQR,
    downloadQR,
    clearQR,
    closeQrModal,
    zoomIn,
    zoomOut,
    restoreFromStorage,
  }
}