xiaoxia-saas/apps/web/src/pages/generate/utils/calculateResolution.ts

/**
 * 根据视频比例计算输出分辨率
 *
 * 规则：
 * - 长边固定 1920
 * - 短边按 1920 × (短/长) 计算，对齐到偶数
 * - 9:16 → 1080×1920（竖屏）
 * - 16:9 → 1920×1080（横屏）
 * - 1:1   → 1920×1920
 * - 无法解析时 fallback 到 1080×1920
 */
export interface Resolution {
  width: number
  height: number
}

export function calculateResolution(ratio: string): Resolution {
  if (!ratio) return { width: 1080, height: 1920 }

  if (ratio.includes(":")) {
    const [rw, rh] = ratio.split(":").map(Number)
    if (rw > 0 && rh > 0) {
      const [longSide, shortSide] = rw < rh ? [rh, rw] : [rw, rh]
      const baseLong = 1920
      const baseShort = Math.round((baseLong * shortSide) / longSide)
      const evenShort = baseShort - (baseShort % 2)
      if (rw < rh) {
        // 竖屏：短边是宽，长边是高
        return { width: evenShort, height: baseLong }
      } else {
        // 横屏：长边是宽，短边是高
        return { width: baseLong, height: evenShort }
      }
    }
    return { width: 1080, height: 1920 }
  }

  if (ratio.includes("x")) {
    const [wStr, hStr] = ratio.split("x")
    const w = parseInt(wStr, 10) || 1080
    const h = parseInt(hStr, 10) || 1920
    return { width: w, height: h }
  }

  return { width: 1080, height: 1920 }
}