/** Qwen-safe ~1 MP grid (÷32). Do not use native 2K bins on 16 GB. */
export const QWEN21_SIZE_TABLE = {
  '1:1': [1024, 1024],
  '16:9': [1536, 864],
  '9:16': [864, 1536],
  '4:3': [1152, 864],
  '3:4': [864, 1152],
  '3:2': [1248, 832],
  '2:3': [832, 1248],
  '21:9': [1536, 672],
  '9:21': [672, 1536]
}

export const QWEN21_ASPECT_IDS = new Set(['auto', ...Object.keys(QWEN21_SIZE_TABLE)])

function parseAspectRatio(aspect) {
  const m = String(aspect || '').trim().match(/^(\d+(?:\.\d+)?)\s*:\s*(\d+(?:\.\d+)?)$/)
  if (!m) return null
  const w = Number(m[1]), h = Number(m[2])
  if (!(w > 0 && h > 0)) return null
  return w / h
}

function nearestQwen21Aspect(aspect) {
  const target = parseAspectRatio(aspect)
  if (target == null) return null
  let best = '1:1', bestDiff = Infinity
  for (const [key, [w, h]] of Object.entries(QWEN21_SIZE_TABLE)) {
    const diff = Math.abs(w / h - target)
    if (diff < bestDiff) { bestDiff = diff; best = key }
  }
  return best
}

export function resolveQwen21Size(aspect, source) {
  const key = String(aspect || 'auto').trim()
  if (QWEN21_SIZE_TABLE[key]) {
    const [width, height] = QWEN21_SIZE_TABLE[key]
    return { width, height }
  }
  if (key === 'auto') {
    if (source?.width && source?.height) {
      const nearest = nearestQwen21Aspect(`${source.width}:${source.height}`)
      if (nearest) {
        const [width, height] = QWEN21_SIZE_TABLE[nearest]
        return { width, height }
      }
    }
    return { width: 1024, height: 1024 }
  }
  const nearest = nearestQwen21Aspect(key)
  if (nearest) {
    const [width, height] = QWEN21_SIZE_TABLE[nearest]
    return { width, height }
  }
  console.warn(`[qwen21] unknown aspect "${key}"; using 1024×1024`)
  return { width: 1024, height: 1024 }
}