import { boxBlur } from '@/utils/maskOps'

export type MapU8 = { data: Uint8Array; width: number; height: number }

export function lumaFromRgba(rgba: Uint8ClampedArray, width: number, height: number): Uint8Array {
  const out = new Uint8Array(width * height)
  for (let i = 0, j = 0; i < out.length; i++, j += 4) {
    const r = rgba[j]
    const g = rgba[j + 1]
    const b = rgba[j + 2]
    out[i] = Math.max(0, Math.min(255, Math.round(0.299 * r + 0.587 * g + 0.114 * b)))
  }
  return out
}

export function normalizeU8(data: Uint8Array, mask?: Uint8Array | null): Uint8Array {
  let min = 255
  let max = 0
  for (let i = 0; i < data.length; i++) {
    if (mask && !mask[i]) continue
    const v = data[i]
    if (v < min) min = v
    if (v > max) max = v
  }
  const range = Math.max(1, max - min)
  const out = new Uint8Array(data.length)
  for (let i = 0; i < data.length; i++) {
    if (mask && !mask[i]) {
      out[i] = 0
      continue
    }
    out[i] = Math.max(0, Math.min(255, Math.round(((data[i] - min) * 255) / range)))
  }
  return out
}

/**
 * Builds a smooth light/brightness map from the original image:
 * - luma
 * - strong blur
 * - normalize to 0..255
 * Values outside `tilesMask` are set to 0.
 */
export function buildLightMap(opts: {
  rgba: Uint8ClampedArray
  width: number
  height: number
  tilesMask?: Uint8Array | null
  blurRadiusPx?: number
}): MapU8 {
  const width = Math.max(1, Math.round(opts.width))
  const height = Math.max(1, Math.round(opts.height))
  const tilesMask = opts.tilesMask ?? null
  const blurRadius = Math.max(0, Math.round(opts.blurRadiusPx ?? 40))

  const gray = lumaFromRgba(opts.rgba, width, height)
  if (!blurRadius) {
    return { data: normalizeU8(gray, tilesMask), width, height }
  }

  const blurred = boxBlur(gray, width, height, blurRadius)
  const blurredU8 = new Uint8Array(width * height)
  for (let i = 0; i < blurredU8.length; i++) {
    const v = blurred[i]
    blurredU8[i] = Math.max(0, Math.min(255, Math.round(Number.isFinite(v) ? v : gray[i])))
  }
  const norm = normalizeU8(blurredU8, tilesMask)
  return { data: norm, width, height }
}