// 配色引擎：把底图 + 二维码合成为 MARD 色号网格
// 性能要点：
//  1. 5bit 量化桶 → 候选 Top-K 查找表（懒加载），每格只精算约 10 个候选，而非整套 291 色
//  2. OKLab 感知距离 + 色间距离矩阵，全部 Typed Array，无对象分配
//  3. “颜色连贯度”参考已选中的左/上邻居色号，减少零碎杂色，拼起来更省事
//  4. 定位/时序/对齐等功能区使用更严格的深浅阈值，显著提升扫码成功率
const { rgbToOklabInto } = require('./color')
const { MATCH_MODES } = require('./palette')
const { PAPER } = require('./imaging')

const TOP_K = 10
const C_ANY = 0
const C_DARK = 1
const C_LIGHT = 2
const C_FDARK = 3
const C_FLIGHT = 4
const C_QUIET = 5
const C_EMPTY = 6

function subsetFor(pal, mode, kind) {
  const key = `${mode.id}:${kind}`
  if (pal.subsets[key]) return pal.subsets[key]
  const { n, lum } = pal
  let test
  if (kind === C_DARK) test = (i) => lum[i] <= mode.darkMax
  else if (kind === C_LIGHT) test = (i) => lum[i] >= mode.lightMin
  else if (kind === C_FDARK) test = (i) => lum[i] <= Math.min(mode.darkMax, 0.3)
  else if (kind === C_FLIGHT) test = (i) => lum[i] >= Math.max(mode.lightMin, 0.82)
  else test = () => true
  let list = []
  for (let i = 0; i < n; i += 1) if (test(i)) list.push(i)
  if (!list.length) {
    // 色库太小时退化为最深/最浅的 3 个颜色
    const order = Array.from({ length: n }, (_, i) => i).sort((a, b) => lum[a] - lum[b])
    list = kind === C_DARK || kind === C_FDARK ? order.slice(0, 3) : order.slice(-3)
  }
  const member = new Uint8Array(n)
  list.forEach((i) => { member[i] = 1 })
  const subset = { key, list: Int16Array.from(list), member, lut: new Map() }
  pal.subsets[key] = subset
  return subset
}

const tmpLab = new Float32Array(3)

function topKForBucket(pal, subset, bucket) {
  let hit = subset.lut.get(bucket)
  if (hit) return hit
  const r = ((bucket >> 10) & 31) * 8 + 4
  const g = ((bucket >> 5) & 31) * 8 + 4
  const b = (bucket & 31) * 8 + 4
  rgbToOklabInto(r, g, b, tmpLab, 0)
  const { lab } = pal
  const list = subset.list
  const k = Math.min(TOP_K, list.length)
  const bestIdx = new Int16Array(k).fill(-1)
  const bestDist = new Float32Array(k).fill(Infinity)
  for (let t = 0; t < list.length; t += 1) {
    const i = list[t]
    const dl = lab[i * 3] - tmpLab[0]
    const da = lab[i * 3 + 1] - tmpLab[1]
    const db = lab[i * 3 + 2] - tmpLab[2]
    const d = dl * dl + da * da + db * db
    if (d >= bestDist[k - 1]) continue
    let p = k - 1
    while (p > 0 && bestDist[p - 1] > d) { bestDist[p] = bestDist[p - 1]; bestIdx[p] = bestIdx[p - 1]; p -= 1 }
    bestDist[p] = d
    bestIdx[p] = i
  }
  hit = bestIdx
  subset.lut.set(bucket, hit)
  return hit
}

/**
 * @param base      { size, rgb: Uint8Array, mask?: Uint8Array } 或 null（无底图）
 * @param qr        makeQr() 结果
 * @param placement createPlacement() 结果
 * @param pal       preparePalette() 结果
 * @param options   { modeId, coherence(0-100), cleanup(bool) }
 */
function computeArtwork(base, qr, placement, pal, options = {}) {
  const mode = MATCH_MODES.find((m) => m.id === options.modeId) || MATCH_MODES[1]
  const size = placement.size
  const total = size * size
  const lab = new Float32Array(total * 3)
  const bucket = new Int32Array(total)
  const kind = new Uint8Array(total)
  const { left, top, quiet } = placement

  for (let y = 0; y < size; y += 1) {
    for (let x = 0; x < size; x += 1) {
      const i = y * size + x
      const qx = x - left
      const qy = y - top
      const inQr = qx >= 0 && qy >= 0 && qx < qr.size && qy < qr.size
      const inQuiet = !inQr && x >= left - quiet && x < left + qr.size + quiet && y >= top - quiet && y < top + qr.size + quiet
      let r; let g; let b
      if (inQr) {
        const q = qy * qr.size + qx
        const isDark = qr.dark[q]
        const isFunc = qr.func[q]
        kind[i] = isFunc ? (isDark ? C_FDARK : C_FLIGHT) : (isDark ? C_DARK : C_LIGHT)
        if (base && !(base.mask && base.mask[i])) {
          r = base.rgb[i * 3]; g = base.rgb[i * 3 + 1]; b = base.rgb[i * 3 + 2]
        } else if (base) {
          r = PAPER[0]; g = PAPER[1]; b = PAPER[2]
        } else {
          r = g = b = isDark ? 0 : 255
        }
      } else if (inQuiet || !base) {
        kind[i] = C_QUIET
        continue
      } else if (base.mask && base.mask[i]) {
        kind[i] = C_EMPTY
        continue
      } else {
        kind[i] = C_ANY
        r = base.rgb[i * 3]; g = base.rgb[i * 3 + 1]; b = base.rgb[i * 3 + 2]
      }
      rgbToOklabInto(r, g, b, lab, i * 3)
      bucket[i] = ((r >> 3) << 10) | ((g >> 3) << 5) | (b >> 3)
    }
  }

  const n = pal.n
  const plab = pal.lab
  const pair = pal.pair
  const weight = (Math.max(0, Math.min(100, options.coherence == null ? 40 : options.coherence)) / 100) * 0.6
  const subsets = [C_ANY, C_DARK, C_LIGHT, C_FDARK, C_FLIGHT].map((k) => subsetFor(pal, mode, k))
  const cells = new Int16Array(total).fill(-1)

  const distTo = (c, i) => {
    const dl = plab[c * 3] - lab[i * 3]
    const da = plab[c * 3 + 1] - lab[i * 3 + 1]
    const db = plab[c * 3 + 2] - lab[i * 3 + 2]
    return Math.sqrt(dl * dl + da * da + db * db)
  }

  for (let y = 0; y < size; y += 1) {
    for (let x = 0; x < size; x += 1) {
      const i = y * size + x
      const k = kind[i]
      if (k >= C_QUIET) continue
      const subset = subsets[k]
      const cands = topKForBucket(pal, subset, bucket[i])
      const nl = x > 0 ? cells[i - 1] : -1
      const nu = y > 0 ? cells[i - size] : -1
      const nbCount = (nl >= 0 ? 1 : 0) + (nu >= 0 ? 1 : 0)
      let best = -1
      let bestScore = Infinity
      const consider = (c) => {
        let score = distTo(c, i)
        if (weight > 0 && nbCount) {
          let s = 0
          if (nl >= 0) s += pair[c * n + nl]
          if (nu >= 0) s += pair[c * n + nu]
          score += weight * (s / nbCount)
        }
        if (score < bestScore) { bestScore = score; best = c }
      }
      for (let t = 0; t < cands.length; t += 1) if (cands[t] >= 0) consider(cands[t])
      if (weight > 0) {
        if (nl >= 0 && subset.member[nl]) consider(nl)
        if (nu >= 0 && nu !== nl && subset.member[nu]) consider(nu)
      }
      cells[i] = best
    }
  }

  // 合并零散色：只用了 1~2 颗的色号并入最接近的常用色，减少需要购买的色号
  const counts = new Int32Array(n)
  for (let i = 0; i < total; i += 1) if (cells[i] >= 0) counts[cells[i]] += 1
  if (options.cleanup !== false) {
    const kept = []
    for (let c = 0; c < n; c += 1) if (counts[c] >= 3) kept.push(c)
    if (kept.length) {
      for (let i = 0; i < total; i += 1) {
        const c = cells[i]
        if (c < 0 || counts[c] >= 3) continue
        const member = subsets[kind[i]].member
        let best = -1
        let bestD = Infinity
        for (let t = 0; t < kept.length; t += 1) {
          const kc = kept[t]
          if (!member[kc]) continue
          const d = distTo(kc, i)
          if (d < bestD) { bestD = d; best = kc }
        }
        // 与原色差别过大时保留原色，避免破坏画面
        if (best >= 0 && bestD <= distTo(c, i) + 12) cells[i] = best
      }
      counts.fill(0)
      for (let i = 0; i < total; i += 1) if (cells[i] >= 0) counts[cells[i]] += 1
    }
  }

  // 二维码留白区：使用画面中最常用的浅色；没有则用色库里最浅的颜色
  let quietColor = -1
  let quietCount = -1
  for (let c = 0; c < n; c += 1) {
    if (pal.lum[c] >= Math.max(0.8, mode.lightMin) && counts[c] > quietCount) { quietColor = c; quietCount = counts[c] }
  }
  if (quietCount <= 0) {
    quietColor = 0
    for (let c = 1; c < n; c += 1) if (pal.lum[c] > pal.lum[quietColor]) quietColor = c
  }
  for (let i = 0; i < total; i += 1) {
    if (kind[i] === C_QUIET) { cells[i] = quietColor; counts[quietColor] += 1 }
  }

  const usage = []
  let beads = 0
  for (let c = 0; c < n; c += 1) {
    if (counts[c] > 0) {
      usage.push({ index: c, id: pal.ids[c], hex: pal.hexes[c], count: counts[c] })
      beads += counts[c]
    }
  }
  usage.sort((a, b) => b.count - a.count)

  return { size, cells, usage, beads, pal, qr, placement }
}

module.exports = { computeArtwork }