oil-formula-calculator/frontend/src/composables/useSaveImage.js

/**
 * Save image — on mobile use navigator.share (same as recipe card),
 * on desktop trigger download.
 */

const isMobile = () => /iPhone|iPad|iPod|Android/i.test(navigator.userAgent)

/**
 * Save from a data URL.
 * Mobile: navigator.share({files}) → system share sheet (save to photos / AirDrop etc)
 * Desktop: download link.
 */
export async function saveImageFromUrl(dataUrl, filename) {
  // Try navigator.share with files (works on iOS Safari, Chrome mobile)
  if (navigator.share && navigator.canShare) {
    try {
      const res = await fetch(dataUrl)
      const blob = await res.blob()
      const file = new File([blob], filename + '.png', { type: 'image/png' })
      if (navigator.canShare({ files: [file] })) {
        await navigator.share({ files: [file] })
        return 'shared'
      }
    } catch (e) {
      // User cancelled share or share failed, fall through to download
      if (e.name === 'AbortError') return 'cancelled'
    }
  }

  // Fallback: direct download
  const a = document.createElement('a')
  a.href = dataUrl
  a.download = filename + '.png'
  document.body.appendChild(a)
  a.click()
  setTimeout(() => a.remove(), 100)
  return 'downloaded'
}