core/detector.ts

/**
 * High-level watermark detector
 *
 * Takes a Y plane + key + config → returns detection result
 */

import type { WatermarkConfig, DetectionResult, Buffer2D } from './types.js';
import { createBuffer2D, yPlaneToBuffer, dwtForward, extractSubband } from './dwt.js';
import { dctForward8x8, extractBlock, ZIGZAG_ORDER } from './dct.js';
import { dmqimExtractSoft } from './dmqim.js';
import { crcVerify } from './crc.js';
import { BchCodec } from './bch.js';
import { generateDithers, generatePermutation } from './keygen.js';
import { computeTileGrid, recoverTileGrid, getTileOrigin, getTileBlocks, type TileGrid } from './tiling.js';
import { blockAcEnergy, computeMaskingFactors } from './masking.js';
import { bitsToPayload } from './embedder.js';
import { PRESETS } from './presets.js';
import type { PresetName } from './types.js';

/**
 * Detect and extract watermark from a single Y plane
 */
export function detectWatermark(
  yPlane: Uint8Array,
  width: number,
  height: number,
  key: string,
  config: WatermarkConfig
): DetectionResult {
  return detectWatermarkMultiFrame([yPlane], width, height, key, config);
}

/**
 * Extract per-tile soft decisions from a single Y plane.
 * Returns an array of soft-bit vectors, one per tile.
 */
/** Precomputed DWT subband + tile grid info for a frame */
interface FrameDWT {
  hlSubband: Buffer2D;
  subbandTilePeriod: number;
}

function computeFrameDWT(
  yPlane: Uint8Array,
  width: number,
  height: number,
  config: WatermarkConfig
): FrameDWT {
  const buf = yPlaneToBuffer(yPlane, width, height);
  const { buf: dwtBuf, dims } = dwtForward(buf, config.dwtLevels);
  const hlSubband = extractSubband(dwtBuf, dims[dims.length - 1].w, dims[dims.length - 1].h, 'HL');
  const subbandTilePeriod = Math.floor(config.tilePeriod / (1 << config.dwtLevels));
  return { hlSubband, subbandTilePeriod };
}

function extractSoftBitsFromSubband(
  hlSubband: Buffer2D,
  tileGrid: TileGrid,
  key: string,
  config: WatermarkConfig,
  ditherOffX: number = 0,
  ditherOffY: number = 0,
  blocksPerSide: number = 0,
): { tileSoftBits: Float64Array[]; totalTiles: number } | null {
  if (tileGrid.totalTiles === 0) return null;

  const codedLength = config.bch.n;
  const maxCoeffsPerTile = 1024;
  const dithers = generateDithers(key, maxCoeffsPerTile, config.delta);

  const tileSoftBits: Float64Array[] = [];
  const blockBuf = new Float64Array(64);

  // Precompute zigzag → coefficient index mapping
  const zigCoeffIdx = new Int32Array(config.zigzagPositions.length);
  for (let z = 0; z < config.zigzagPositions.length; z++) {
    const [r, c] = ZIGZAG_ORDER[config.zigzagPositions[z]];
    zigCoeffIdx[z] = r * 8 + c;
  }

  const hasDitherOffset = ditherOffX !== 0 || ditherOffY !== 0;
  const numZig = config.zigzagPositions.length;

  for (let tileIdx = 0; tileIdx < tileGrid.totalTiles; tileIdx++) {
    let ditherIdx = 0; // Reset per tile — matches embedder
    const origin = getTileOrigin(tileGrid, tileIdx);
    const blocks = getTileBlocks(origin.x, origin.y, tileGrid.tilePeriod, hlSubband.width, hlSubband.height);
    const tileOriginBlockRow = Math.floor(origin.y / 8);
    const tileOriginBlockCol = Math.floor(origin.x / 8);

    const softBits = new Float64Array(codedLength);
    const bitCounts = new Float64Array(codedLength);

    let maskingFactors: Float64Array | null = null;
    if (config.perceptualMasking && blocks.length > 0) {
      const energies = new Float64Array(blocks.length);
      for (let bi = 0; bi < blocks.length; bi++) {
        extractBlock(hlSubband.data, hlSubband.width, blocks[bi].row, blocks[bi].col, blockBuf);
        dctForward8x8(blockBuf);
        energies[bi] = blockAcEnergy(blockBuf);
      }
      maskingFactors = computeMaskingFactors(energies);
    }

    let bitIdx = 0;
    for (let bi = 0; bi < blocks.length; bi++) {
      const { row, col } = blocks[bi];
      extractBlock(hlSubband.data, hlSubband.width, row, col, blockBuf);
      dctForward8x8(blockBuf);

      const maskFactor = maskingFactors ? maskingFactors[bi] : 1.0;
      const effectiveDelta = config.delta * maskFactor;

      // Compute dither index and bit index: when dither offset is active,
      // remap block position to find the embedder's dither and bit assignment
      // for this spatial location within the periodic tile structure.
      let blockDitherBase: number;
      if (hasDitherOffset && blocksPerSide > 0) {
        const relBr = row - tileOriginBlockRow;
        const relBc = col - tileOriginBlockCol;
        const origR = (relBr + ditherOffY) % blocksPerSide;
        const origC = (relBc + ditherOffX) % blocksPerSide;
        blockDitherBase = (origR * blocksPerSide + origC) * numZig;
        // Remap bitIdx to match the embedder's bit assignment at the original position
        bitIdx = ((origR * blocksPerSide + origC) * numZig) % codedLength;
      } else {
        blockDitherBase = ditherIdx;
      }

      for (let z = 0; z < zigCoeffIdx.length; z++) {
        if (bitIdx >= codedLength) bitIdx = 0;

        const coeffIdx = zigCoeffIdx[z];
        const dither = hasDitherOffset ? dithers[blockDitherBase + z] : dithers[ditherIdx++];

        const soft = dmqimExtractSoft(blockBuf[coeffIdx], effectiveDelta, dither);
        softBits[bitIdx] += soft;
        bitCounts[bitIdx]++;

        bitIdx++;
      }

      if (!hasDitherOffset) {
        // ditherIdx already incremented in the loop above
      } else {
        ditherIdx += numZig; // keep in sync
      }
    }

    for (let i = 0; i < codedLength; i++) {
      if (bitCounts[i] > 0) softBits[i] /= bitCounts[i];
    }

    tileSoftBits.push(softBits);
  }

  return { tileSoftBits, totalTiles: tileGrid.totalTiles };
}

/** Options for crop-resilient detection */
export interface DetectOptions {
  /** Enable grid-phase search for cropped content */
  cropResilient?: boolean;
}

/**
 * Detect watermark from multiple Y planes.
 * Extracts soft decisions from each frame independently, then combines
 * across frames and tiles (never averages raw pixels).
 *
 * When cropResilient is true, searches over:
 *   - 16 DWT-pad combinations (0..3 × 0..3 for dwtLevels=2)
 *   - N×N tile-phase offsets (block-aligned, N = tilePeriod/8)
 * Signal magnitude from one frame ranks candidates cheaply, then the
 * top candidates are decoded using all frames.
 */
export function detectWatermarkMultiFrame(
  yPlanes: Uint8Array[],
  width: number,
  height: number,
  key: string,
  config: WatermarkConfig,
  options?: DetectOptions,
): DetectionResult {
  const noResult: DetectionResult = {
    detected: false,
    payload: null,
    confidence: 0,
    tilesDecoded: 0,
    tilesTotal: 0,
  };

  if (yPlanes.length === 0) return noResult;

  const codedLength = config.bch.n;
  const bch = new BchCodec(config.bch);
  const perm = generatePermutation(key, codedLength);

  // Helper: try to detect with given frames and explicit tile grid.
  // makeSubbandAndGrid can optionally transform the subband (e.g. shift it).
  interface SubbandAndGrid {
    subband: Buffer2D;
    grid: TileGrid;
    ditherOffX?: number;
    ditherOffY?: number;
    blocksPerSide?: number;
  }
  const tryDetect = (
    frames: FrameDWT[],
    makeSubbandAndGrid: (hlSubband: Buffer2D, stp: number) => SubbandAndGrid,
  ): DetectionResult | null => {
    const softBits: Float64Array[] = [];
    for (const { hlSubband, subbandTilePeriod } of frames) {
      const { subband, grid, ditherOffX, ditherOffY, blocksPerSide: bps } = makeSubbandAndGrid(hlSubband, subbandTilePeriod);
      const frameResult = extractSoftBitsFromSubband(subband, grid, key, config, ditherOffX ?? 0, ditherOffY ?? 0, bps ?? 0);
      if (frameResult) softBits.push(...frameResult.tileSoftBits);
    }
    if (softBits.length === 0) return null;
    return decodeFromSoftBits(softBits, codedLength, perm, bch, config);
  };

  // Fast path: zero-phase grid (uncropped frames)
  const frameDWTs = yPlanes.map((yp) => computeFrameDWT(yp, width, height, config));
  const fast = tryDetect(frameDWTs, (hl, stp) => ({
    subband: hl,
    grid: computeTileGrid(hl.width, hl.height, stp),
  }));
  if (fast) return fast;

  if (!options?.cropResilient) return noResult;

  // ── Crop-resilient: joint search over DWT-pad × pixel-shift × dither-offset ──
  //
  // A crop of C pixels causes three alignment problems:
  //   1. DWT pixel pairing: pad by C%4 → search 0..3 per axis (16 combos)
  //   2. DCT block alignment: subband shift % 8 → search 0..7 per axis (64)
  //   3. Tile dither offset: which block within the tile period does the
  //      detector's block 0 correspond to? Search 0..blocksPerTileSide-1
  //      per axis.
  //
  // All three must be correct simultaneously for signal to emerge, so we
  // search them jointly. For each (pad, shift), we compute DCT blocks once
  // per scoring frame, then sweep dither offsets cheaply (DMQIM re-indexing
  // only, no DCT recomputation).
  //
  // Scoring uses min(4, nFrames) frames for reliable ranking.
  // Top candidates are decoded with ALL frames.

  const subbandTilePeriod = Math.floor(config.tilePeriod / (1 << config.dwtLevels));
  const effectiveTP = Math.max(8, Math.floor(subbandTilePeriod / 8) * 8);
  const blocksPerSide = effectiveTP / 8;
  const dwtPads = 1 << config.dwtLevels; // 4 for dwtLevels=2

  // Scoring: use frame 0 only for fast candidate ranking (36K candidates)
  const nScoringFrames = 1;

  interface Candidate {
    padTop: number;
    padLeft: number;
    shiftX: number;
    shiftY: number;
    ditherOffX: number;
    ditherOffY: number;
    signalMag: number;
  }

  const candidates: Candidate[] = [];

  // Precompute DWTs for scoring frames, cached by pad
  const scoringDWTCache = new Map<string, FrameDWT[]>();
  const getScoringDWTs = (padTop: number, padLeft: number): FrameDWT[] => {
    const cacheKey = `${padTop},${padLeft}`;
    let cached = scoringDWTCache.get(cacheKey);
    if (!cached) {
      cached = [];
      for (let fi = 0; fi < nScoringFrames; fi++) {
        if (padTop === 0 && padLeft === 0) {
          cached.push(frameDWTs[fi]);
        } else {
          const { padded, paddedW, paddedH } = padYPlane(yPlanes[fi], width, height, padLeft, padTop);
          cached.push(computeFrameDWT(padded, paddedW, paddedH, config));
        }
      }
      scoringDWTCache.set(cacheKey, cached);
    }
    return cached;
  };

  // Precompute zigzag → coefficient index mapping for scoring
  const numZig = config.zigzagPositions.length;
  const zigCoeffIdx = new Int32Array(numZig);
  for (let z = 0; z < numZig; z++) {
    const [r, c] = ZIGZAG_ORDER[config.zigzagPositions[z]];
    zigCoeffIdx[z] = r * 8 + c;
  }
  const scoreDithers = generateDithers(key, 1024, config.delta);
  const blockBuf = new Float64Array(64);

  // Phase 1: score all candidates with DCT caching.
  // For each (pad, shift), compute DCT once per scoring frame, then sweep
  // all dither offsets using only DMQIM re-indexing (no DCT recomputation).
  for (let padTop = 0; padTop < dwtPads; padTop++) {
    for (let padLeft = 0; padLeft < dwtPads; padLeft++) {
      const scoreDWTs = getScoringDWTs(padTop, padLeft);

      for (let shiftY = 0; shiftY < 8; shiftY++) {
        for (let shiftX = 0; shiftX < 8; shiftX++) {
          const hl0 = scoreDWTs[0].hlSubband;
          const newW = hl0.width - shiftX;
          const newH = hl0.height - shiftY;
          if (newW < effectiveTP || newH < effectiveTP) continue;

          const grid = computeTileGrid(newW, newH, subbandTilePeriod);
          if (grid.totalTiles === 0) continue;

          // Use tile 0 for scoring (fast; sufficient for ranking)
          const tile0Origin = getTileOrigin(grid, 0);
          const tile0Blocks = getTileBlocks(
            tile0Origin.x, tile0Origin.y, grid.tilePeriod, newW, newH
          );
          const nBlocks = tile0Blocks.length;
          if (nBlocks === 0) continue;

          const tile0OriginBR = Math.floor(tile0Origin.y / 8);
          const tile0OriginBC = Math.floor(tile0Origin.x / 8);
          const relBR = new Int32Array(nBlocks);
          const relBC = new Int32Array(nBlocks);
          for (let bi = 0; bi < nBlocks; bi++) {
            relBR[bi] = tile0Blocks[bi].row - tile0OriginBR;
            relBC[bi] = tile0Blocks[bi].col - tile0OriginBC;
          }

          // Precompute DCT coefficients + effective deltas per scoring frame
          const frameCoeffs: Float64Array[] = [];
          const frameDeltas: Float64Array[] = [];

          for (let fi = 0; fi < scoreDWTs.length; fi++) {
            const shifted = createShiftedSubband(scoreDWTs[fi].hlSubband, shiftX, shiftY);
            const coeffs = new Float64Array(nBlocks * numZig);
            const deltas = new Float64Array(nBlocks);

            if (config.perceptualMasking) {
              const energies = new Float64Array(nBlocks);
              for (let bi = 0; bi < nBlocks; bi++) {
                extractBlock(shifted.data, newW, tile0Blocks[bi].row, tile0Blocks[bi].col, blockBuf);
                dctForward8x8(blockBuf);
                energies[bi] = blockAcEnergy(blockBuf);
                for (let z = 0; z < numZig; z++) {
                  coeffs[bi * numZig + z] = blockBuf[zigCoeffIdx[z]];
                }
              }
              const factors = computeMaskingFactors(energies);
              for (let bi = 0; bi < nBlocks; bi++) {
                deltas[bi] = config.delta * factors[bi];
              }
            } else {
              for (let bi = 0; bi < nBlocks; bi++) {
                extractBlock(shifted.data, newW, tile0Blocks[bi].row, tile0Blocks[bi].col, blockBuf);
                dctForward8x8(blockBuf);
                for (let z = 0; z < numZig; z++) {
                  coeffs[bi * numZig + z] = blockBuf[zigCoeffIdx[z]];
                }
                deltas[bi] = config.delta;
              }
            }

            frameCoeffs.push(coeffs);
            frameDeltas.push(deltas);
          }

          // Sweep all dither offsets using cached coefficients (DMQIM only)
          for (let ditherOffY = 0; ditherOffY < blocksPerSide; ditherOffY++) {
            for (let ditherOffX = 0; ditherOffX < blocksPerSide; ditherOffX++) {
              if (padTop === 0 && padLeft === 0 && shiftX === 0 && shiftY === 0
                  && ditherOffX === 0 && ditherOffY === 0) {
                continue; // Already tried in fast path
              }

              const avg = new Float64Array(codedLength);
              let nSamples = 0;

              for (let fi = 0; fi < frameCoeffs.length; fi++) {
                const coeffs = frameCoeffs[fi];
                const deltas = frameDeltas[fi];
                const softBits = new Float64Array(codedLength);
                const bitCounts = new Float64Array(codedLength);

                for (let bi = 0; bi < nBlocks; bi++) {
                  const origR = ((relBR[bi] + ditherOffY) % blocksPerSide + blocksPerSide) % blocksPerSide;
                  const origC = ((relBC[bi] + ditherOffX) % blocksPerSide + blocksPerSide) % blocksPerSide;
                  const blockDitherBase = (origR * blocksPerSide + origC) * numZig;
                  const ed = deltas[bi];
                  // Remap bitIdx to match embedder's bit assignment at original position
                  let bitIdx = ((origR * blocksPerSide + origC) * numZig) % codedLength;

                  for (let z = 0; z < numZig; z++) {
                    if (bitIdx >= codedLength) bitIdx = 0;
                    const soft = dmqimExtractSoft(coeffs[bi * numZig + z], ed, scoreDithers[blockDitherBase + z]);
                    softBits[bitIdx] += soft;
                    bitCounts[bitIdx]++;
                    bitIdx++;
                  }
                }

                for (let i = 0; i < codedLength; i++) {
                  if (bitCounts[i] > 0) softBits[i] /= bitCounts[i];
                  avg[i] += softBits[i];
                }
                nSamples++;
              }

              let mag = 0;
              for (let i = 0; i < codedLength; i++) {
                avg[i] /= nSamples;
                mag += avg[i] * avg[i];
              }

              candidates.push({ padTop, padLeft, shiftX, shiftY, ditherOffX, ditherOffY, signalMag: mag });
            }
          }
        }
      }
    }
  }

  // Sort by signal magnitude and decode top candidates with all frames
  candidates.sort((a, b) => b.signalMag - a.signalMag);
  const MAX_DECODE = 50;
  let bestResult: DetectionResult | null = null;

  for (let i = 0; i < Math.min(MAX_DECODE, candidates.length); i++) {
    const { padTop, padLeft, shiftX, shiftY, ditherOffX, ditherOffY } = candidates[i];

    const dwts = (padTop === 0 && padLeft === 0)
      ? frameDWTs
      : yPlanes.map((yp) => {
          const { padded, paddedW, paddedH } = padYPlane(yp, width, height, padLeft, padTop);
          return computeFrameDWT(padded, paddedW, paddedH, config);
        });

    const result = tryDetect(dwts, (hl) => {
      const shifted = createShiftedSubband(hl, shiftX, shiftY);
      const grid = computeTileGrid(shifted.width, shifted.height, subbandTilePeriod);
      return { subband: shifted, grid, ditherOffX, ditherOffY, blocksPerSide };
    });

    if (result && (!bestResult || result.confidence > bestResult.confidence)) {
      bestResult = result;
    }

    if (bestResult && bestResult.confidence >= 0.95) break;
  }

  return bestResult ?? noResult;
}

/**
 * Pad a Y plane with edge-replicated border pixels to realign DWT pixel pairing.
 */
function padYPlane(
  yPlane: Uint8Array,
  width: number,
  height: number,
  padLeft: number,
  padTop: number,
): { padded: Uint8Array; paddedW: number; paddedH: number } {
  const paddedW = width + padLeft;
  const paddedH = height + padTop;
  const padded = new Uint8Array(paddedW * paddedH);

  for (let y = 0; y < paddedH; y++) {
    const srcY = Math.max(0, y - padTop);
    for (let x = 0; x < paddedW; x++) {
      const srcX = Math.max(0, x - padLeft);
      padded[y * paddedW + x] = yPlane[srcY * width + srcX];
    }
  }

  return { padded, paddedW, paddedH };
}

/**
 * Create a shifted view of a subband (cheap array copy).
 */
function createShiftedSubband(hl: Buffer2D, shiftX: number, shiftY: number): Buffer2D {
  const newW = hl.width - shiftX;
  const newH = hl.height - shiftY;
  const shifted = createBuffer2D(newW, newH);
  for (let y = 0; y < newH; y++) {
    const srcOff = (y + shiftY) * hl.width + shiftX;
    const dstOff = y * newW;
    for (let x = 0; x < newW; x++) {
      shifted.data[dstOff + x] = hl.data[srcOff + x];
    }
  }
  return shifted;
}

/**
 * Combine soft bits from all tiles, decode, and compute confidence.
 * Returns null if decoding fails or confidence is too low.
 */
function decodeFromSoftBits(
  allTileSoftBits: Float64Array[],
  codedLength: number,
  perm: Uint32Array,
  bch: BchCodec,
  config: WatermarkConfig
): DetectionResult | null {
  const combined = new Float64Array(codedLength);
  for (const tileSoft of allTileSoftBits) {
    for (let i = 0; i < codedLength; i++) {
      combined[i] += tileSoft[i];
    }
  }
  for (let i = 0; i < codedLength; i++) {
    combined[i] /= allTileSoftBits.length;
  }

  const decoded = tryDecode(combined, perm, bch, config);
  if (!decoded) return null;

  // Cross-validate — count how many individual tiles agree with the combined decode
  const reEncoded = bch.encode(decoded.rawMessage);
  let agreeTiles = 0;

  for (const tileSoft of allTileSoftBits) {
    const deinterleaved = new Float64Array(codedLength);
    for (let i = 0; i < codedLength; i++) {
      deinterleaved[i] = tileSoft[perm[i]];
    }
    let matching = 0;
    for (let i = 0; i < codedLength; i++) {
      const hardBit = deinterleaved[i] > 0 ? 1 : 0;
      if (hardBit === reEncoded[i]) matching++;
    }
    if (matching / codedLength > 0.65) agreeTiles++;
  }

  const totalTileCount = allTileSoftBits.length;
  const zSingle = 0.3 * Math.sqrt(codedLength);
  const pChance = Math.max(1e-10, 0.5 * Math.exp(-0.5 * zSingle * zSingle));

  const expected = totalTileCount * pChance;
  const stddev = Math.sqrt(totalTileCount * pChance * (1 - pChance));
  const z = stddev > 0 ? (agreeTiles - expected) / stddev : agreeTiles > expected ? 100 : 0;
  const statsConfidence = Math.max(0, Math.min(1.0, 1 - Math.exp(-z * 0.5)));

  const confidence = Math.max(statsConfidence, decoded.softConfidence);

  if (confidence < MIN_CONFIDENCE) return null;

  return {
    detected: true,
    payload: decoded.payload,
    confidence,
    tilesDecoded: agreeTiles,
    tilesTotal: allTileSoftBits.length,
  };
}

/** Minimum confidence to report a detection (low threshold is fine —
 *  the statistical model already ensures noise scores near 0%) */
const MIN_CONFIDENCE = 0.75;

/**
 * Try to decode soft bits into a payload
 */
function tryDecode(
  softBits: Float64Array,
  perm: Uint32Array,
  bch: BchCodec,
  config: WatermarkConfig
): { payload: Uint8Array; rawMessage: Uint8Array; softConfidence: number } | null {
  const codedLength = config.bch.n;

  // De-interleave
  const deinterleaved = new Float64Array(codedLength);
  for (let i = 0; i < codedLength; i++) {
    deinterleaved[i] = softBits[perm[i]];
  }

  // BCH soft decode
  const { message, reliable } = bch.decodeSoft(deinterleaved);
  if (!message) return null;

  // Extract the CRC-protected portion (first 32 + crc_bits of the BCH message)
  const PAYLOAD_BITS = 32;
  const crcProtectedLen = PAYLOAD_BITS + config.crc.bits;
  const crcProtected = message.subarray(0, crcProtectedLen);

  // CRC verify the 32-bit payload
  const verified = crcVerify(crcProtected, config.crc.bits);
  if (!verified) return null;

  // Convert 32 payload bits to bytes
  const payload = bitsToPayload(verified);

  // Soft confidence = correlation between soft decisions and decoded codeword.
  // Real signal: soft values are large AND agree with the codeword → high correlation.
  // Noise that BCH happened to decode: soft values are small/random → low correlation.
  const reEncoded = bch.encode(message);
  let correlation = 0;
  for (let i = 0; i < codedLength; i++) {
    const sign = reEncoded[i] === 1 ? 1 : -1;
    correlation += sign * deinterleaved[i];
  }
  correlation /= codedLength;
  const softConfidence = Math.max(0, Math.min(1.0, correlation * 2));

  return { payload, rawMessage: message, softConfidence };
}

/** Extended detection result that includes which preset matched */
export interface AutoDetectResult extends DetectionResult {
  /** The preset that produced the detection (null if not detected) */
  presetUsed: PresetName | null;
}

/**
 * Auto-detect: try all presets and return the best result.
 * No need for the user to know which preset was used during embedding.
 */
export function autoDetect(
  yPlane: Uint8Array,
  width: number,
  height: number,
  key: string,
  options?: DetectOptions,
): AutoDetectResult {
  return autoDetectMultiFrame([yPlane], width, height, key, options);
}

/**
 * Auto-detect with multiple frames: try all presets, return the best result.
 */
export function autoDetectMultiFrame(
  yPlanes: Uint8Array[],
  width: number,
  height: number,
  key: string,
  options?: DetectOptions,
): AutoDetectResult {
  let best: AutoDetectResult = {
    detected: false,
    payload: null,
    confidence: 0,
    tilesDecoded: 0,
    tilesTotal: 0,
    presetUsed: null,
  };

  for (const [name, config] of Object.entries(PRESETS)) {
    const result = detectWatermarkMultiFrame(yPlanes, width, height, key, config, options);
    if (result.detected && result.confidence > best.confidence) {
      best = { ...result, presetUsed: name as PresetName };
    }
  }

  return best;
}