import { cropRgba, decodePng } from '@/lib/services/imager/png-decode'
import { encodePng, parseNitroBundle } from '@/lib/services/swf/nitro-builder'

interface FurniAsset {
  x?: number
  y?: number
  source?: string
}
interface FurniFrame {
  frame: { x: number; y: number; w: number; h: number }
  rotated?: boolean
}
interface FurniNitroJson {
  name?: string
  assets?: Record<string, FurniAsset>
  spritesheet?: { frames?: Record<string, FurniFrame> }
}

/**
 * Extract the furni catalog icon — the `{name}_icon_a` sprite — from a Nitro
 * bundle and return it as a standalone PNG, or null if the bundle has no icon
 * asset / usable frame. Used for sources that embed furni icons inside the
 * `.nitro` instead of serving a separate `{classname}_icon.png`.
 */
export function extractFurniIconPng(nitro: Buffer): Buffer | null {
  let json: FurniNitroJson
  let png: Buffer
  try {
    const parsed = parseNitroBundle(nitro)
    json = parsed.json as FurniNitroJson
    png = parsed.png
  } catch {
    return null
  }
  const name = json.name
  if (!name || !json.assets) return null

  // The icon asset is conventionally `${name}_icon_a`; fall back to any
  // `${name}_icon*` the bundle exposes.
  const iconKey = json.assets[`${name}_icon_a`]
    ? `${name}_icon_a`
    : Object.keys(json.assets).find((k) => k.startsWith(`${name}_icon`))
  if (!iconKey) return null

  const asset = json.assets[iconKey]
  // An asset may alias another's pixels via `source`; the frame key is the
  // bundle name prefixed onto the asset name. Different converters pack the
  // key with or without a trailing `.png`, so try both.
  const pixelAsset = asset.source ?? iconKey
  const frames = json.spritesheet?.frames ?? {}
  const frame = frames[`${name}_${pixelAsset}`] ?? frames[`${name}_${pixelAsset}.png`]
  if (!frame || frame.rotated) return null
  const { x, y, w, h } = frame.frame
  if (w <= 0 || h <= 0) return null

  try {
    const sheet = decodePng(png)
    const px = cropRgba(sheet.rgba, sheet.width, x, y, w, h)
    return encodePng(w, h, px)
  } catch {
    return null
  }
}