/**
 * Country flags for the price-sheet PDF.
 *
 * Source = the same SVGs the price-sheet matrix shows (`public/flags/{ISO2}.svg`),
 * bundled into the server build as the Nitro server asset `assets:flags`
 * (nuxt.config → nitro.serverAssets). pdfmake accepts only PNG/JPEG images and
 * its SVG support chokes on the Wikimedia-style flags (clipPath / use / coats of
 * arms), so every flag is rasterised ONCE per process with sharp (fixed height,
 * natural aspect ratio, 1 px light border so white flags stay visible on paper)
 * and cached as a PNG data URL. Missing / broken flags resolve to null and the
 * PDF simply prints the country name without a flag.
 */
const FLAG_RASTER_HEIGHT_PX = 36
const FLAG_BORDER = '#c8ced6'
/** Widest flag we allow in the PDF (pt) at FLAG_PDF_HEIGHT — Qatar/Switzerland-style ratios are clamped. */
export const FLAG_PDF_HEIGHT = 10
export const FLAG_PDF_MAX_WIDTH = 18

export interface FlagImage {
  dataUrl: string
  /** pdfmake width in pt at FLAG_PDF_HEIGHT (aspect ratio preserved, capped). */
  width: number
  height: number
}

const cache = new Map<string, Promise<FlagImage | null>>()

const render = async (code: string): Promise<FlagImage | null> => {
  try {
    const storage = useStorage('assets:flags')
    const raw: any = await storage.getItemRaw(`${code}.svg`)
    if (!raw) return null
    const svg = Buffer.isBuffer(raw) ? raw : Buffer.from(raw)
    const sharp = (await import('sharp')).default
    // No density: sharp re-renders an SVG at the resize scale anyway. Some flags declare a huge
    // intrinsic size (BB) and trip the default input-pixel guard → limitInputPixels off.
    const png = await sharp(svg, { limitInputPixels: false })
      .resize({ height: FLAG_RASTER_HEIGHT_PX })
      .flatten({ background: '#ffffff' })
      .extend({ top: 1, bottom: 1, left: 1, right: 1, background: FLAG_BORDER })
      .png({ compressionLevel: 9 })
      .toBuffer({ resolveWithObject: true })
    const ratio = png.info.width / Math.max(1, png.info.height)
    const width = Math.min(FLAG_PDF_MAX_WIDTH, Math.round(FLAG_PDF_HEIGHT * ratio * 10) / 10)
    return { dataUrl: `data:image/png;base64,${png.data.toString('base64')}`, width, height: FLAG_PDF_HEIGHT }
  } catch (err: any) {
    console.warn('[PriceSheet] flag render failed for', code, err?.message || err)
    return null
  }
}

export const getFlagImage = (countryCode: string | null | undefined): Promise<FlagImage | null> => {
  const code = String(countryCode || '').trim().toUpperCase()
  if (!/^[A-Z]{2}$/.test(code)) return Promise.resolve(null)
  if (!cache.has(code)) cache.set(code, render(code))
  return cache.get(code)!
}

/** Flags for a set of ISO2 codes — only the ones that rendered. */
export const loadFlagImages = async (codes: Iterable<string | null | undefined>): Promise<Record<string, FlagImage>> => {
  const unique = [...new Set([...codes].map(c => String(c || '').trim().toUpperCase()).filter(c => /^[A-Z]{2}$/.test(c)))]
  const out: Record<string, FlagImage> = {}
  const rendered = await Promise.all(unique.map(async code => [code, await getFlagImage(code)] as const))
  for (const [code, img] of rendered) if (img) out[code] = img
  return out
}