import { useEffect, useMemo, useState } from 'react'

function isStandaloneDisplay() {
  if (typeof window === 'undefined') return false
  return (
    window.matchMedia?.('(display-mode: standalone)').matches ||
    window.navigator.standalone === true
  )
}

function detectPlatform() {
  if (typeof navigator === 'undefined') return 'desktop'

  const userAgent = navigator.userAgent || ''
  const isIOS =
    /iPad|iPhone|iPod/.test(userAgent) ||
    (navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1)

  if (isIOS) return 'ios'
  if (/Android/i.test(userAgent)) return 'android'
  return 'desktop'
}

function getManualInstallInstructions(platform) {
  if (platform === 'ios') {
    return 'Open this app in Safari, tap Share, then choose Add to Home Screen.'
  }
  if (platform === 'android') {
    return 'Open the browser menu and choose Install app or Add to Home screen.'
  }
  return 'Open the browser menu and choose Install OwnGPT, Install app, or Create shortcut.'
}

export function useInstallPrompt() {
  const [deferredPrompt, setDeferredPrompt] = useState(null)
  const [isInstalled, setIsInstalled] = useState(() => isStandaloneDisplay())
  const [platform, setPlatform] = useState(() => detectPlatform())

  useEffect(() => {
    if (typeof window === 'undefined') return undefined

    const handleBeforeInstallPrompt = (event) => {
      event.preventDefault()
      setDeferredPrompt(event)
    }

    const handleInstalled = () => {
      setDeferredPrompt(null)
      setIsInstalled(true)
    }

    const handleModeChange = () => {
      setIsInstalled(isStandaloneDisplay())
    }

    const mediaQuery = window.matchMedia?.('(display-mode: standalone)')
    window.addEventListener('beforeinstallprompt', handleBeforeInstallPrompt)
    window.addEventListener('appinstalled', handleInstalled)
    mediaQuery?.addEventListener?.('change', handleModeChange)

    setPlatform(detectPlatform())
    setIsInstalled(isStandaloneDisplay())

    return () => {
      window.removeEventListener('beforeinstallprompt', handleBeforeInstallPrompt)
      window.removeEventListener('appinstalled', handleInstalled)
      mediaQuery?.removeEventListener?.('change', handleModeChange)
    }
  }, [])

  const manualInstructions = useMemo(() => getManualInstallInstructions(platform), [platform])
  const installState = isInstalled ? 'installed' : deferredPrompt ? 'ready' : 'manual'

  const install = async () => {
    if (isInstalled) {
      return { status: 'installed', platform, instructions: manualInstructions }
    }

    if (!deferredPrompt) {
      return { status: 'manual', platform, instructions: manualInstructions }
    }

    deferredPrompt.prompt()
    const choice = await deferredPrompt.userChoice.catch(() => null)
    setDeferredPrompt(null)

    return {
      status: choice?.outcome === 'accepted' ? 'accepted' : 'dismissed',
      platform,
      instructions: manualInstructions,
    }
  }

  return {
    install,
    installState,
    canPromptInstall: Boolean(deferredPrompt),
    isInstalled,
    platform,
    manualInstructions,
  }
}