// based on https://github.com/jpeg-js/jpeg-js
/*
   Copyright 2011 notmasteryet

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

interface DecodedComponent {
  lines: Uint8Array[];
  scaleX: number;
  scaleY: number;
}

interface Decoded {
  width: number;
  height: number;
  comments: string[];
  exifBuffer: Uint8Array | undefined;
  jfif: any;
  adobe: any;
  components: DecodedComponent[];
}

interface Component {
  h: number;
  v: number;
  blocksPerLine: number;
  blocksPerColumn: number;
  blocks: Int32Array[][];
  pred: number; // ???
  quantizationIdx?: number;
  quantizationTable?: Int32Array;
  huffmanTableDC?: number[] | number[][];
  huffmanTableAC?: number[] | number[][];
}

interface Frame {
  extended: boolean;
  progressive: boolean;
  precision: number;
  scanLines: number;
  samplesPerLine: number;
  components: { [key: number]: Component; };
  componentsOrder: number[];
  maxH: number;
  maxV: number;
  mcusPerLine: number;
  mcusPerColumn: number;
}

const dctZigZag = new Int32Array([
  0,
  1, 8,
  16, 9, 2,
  3, 10, 17, 24,
  32, 25, 18, 11, 4,
  5, 12, 19, 26, 33, 40,
  48, 41, 34, 27, 20, 13, 6,
  7, 14, 21, 28, 35, 42, 49, 56,
  57, 50, 43, 36, 29, 22, 15,
  23, 30, 37, 44, 51, 58,
  59, 52, 45, 38, 31,
  39, 46, 53, 60,
  61, 54, 47,
  55, 62,
  63
]);
const dctCos1 = 4017; // cos(pi/16)
const dctSin1 = 799; // sin(pi/16)
const dctCos3 = 3406; // cos(3*pi/16)
const dctSin3 = 2276; // sin(3*pi/16)
const dctCos6 = 1567; // cos(6*pi/16)
const dctSin6 = 3784; // sin(6*pi/16)
const dctSqrt2 = 5793; // sqrt(2)
const dctSqrt1d2 = 2896; // sqrt(2) / 2

const maxResolutionInMP = 100; // Don't decode more than 100 megapixels
const maxMemoryUsageBytes = 64 * 1024 * 1024; // Don't decode if memory footprint is more than 64MB
let totalBytesAllocated = 0; // avoid unexpected OOMs from untrusted content.

function requestMemoryAllocation(increaseAmount: number) {
  const totalMemoryImpactBytes = totalBytesAllocated + increaseAmount;
  if (totalMemoryImpactBytes > maxMemoryUsageBytes) {
    const exceededAmount = Math.ceil((totalMemoryImpactBytes - maxMemoryUsageBytes) / 1024 / 1024);
    throw new Error(`Max memory limit exceeded by at least ${exceededAmount}MB`);
  }

  totalBytesAllocated = totalMemoryImpactBytes;
}

function buildHuffmanTable(codeLengths: Uint8Array, values: Uint8Array) {
  let length = 16;

  while (length > 0 && !codeLengths[length - 1]) length--;

  interface Code {
    children: number[] | number[][];
    index: number;
  }

  const code: Code[] = [{ children: [], index: 0 }];
  let k = 0;
  let p = code[0];

  for (let i = 0; i < length; i++) {
    for (let j = 0; j < codeLengths[i]; j++) {
      p = code.pop()!;
      p.children[p.index] = values[k];
      while (p.index > 0) {
        if (code.length === 0) throw new Error('Could not recreate Huffman Table');
        p = code.pop()!;
      }
      p.index++;
      code.push(p);
      while (code.length <= i) {
        const q: Code = { children: [], index: 0 };
        code.push(q);
        p.children[p.index] = q.children as number[];
        p = q;
      }
      k++;
    }
    if (i + 1 < length) {
      // p here points to last code
      const q: Code = { children: [], index: 0 };
      code.push(q);
      p.children[p.index] = q.children as number[];
      p = q;
    }
  }

  return code[0].children;
}

function decodeScan(
  data: Uint8Array, offset: number, frame: Frame, components: Component[], resetInterval: number,
  spectralStart: number, spectralEnd: number, successivePrev: number, successive: number
) {
  const mcusPerLine = frame.mcusPerLine;
  const progressive = frame.progressive;
  const startOffset = offset;
  let bitsData = 0;
  let bitsCount = 0;

  function readBit() {
    if (bitsCount > 0) {
      bitsCount--;
      return (bitsData >> bitsCount) & 1;
    }

    bitsData = data[offset++];

    if (bitsData == 0xFF) {
      const nextByte = data[offset++];
      if (nextByte) throw new Error(`unexpected marker: ${((bitsData << 8) | nextByte).toString(16)}`);
      // unstuff 0
    }

    bitsCount = 7;
    return bitsData >>> 7;
  }

  function decodeHuffman(tree: number[] | number[][]) {
    let node: number | number[] | number[][] = tree;

    while (true) {
      node = node[readBit()];
      if (typeof node === 'number') return node;
      if (node === undefined) throw new Error('invalid huffman sequence');
    }
  }

  function receive(length: number) {
    let n = 0;
    while (length > 0) {
      n = (n << 1) | readBit();
      length--;
    }
    return n;
  }

  function receiveAndExtend(length: number) {
    let n = receive(length);
    if (n >= 1 << (length - 1)) return n;
    return n + (-1 << length) + 1;
  }

  type DecodeFn = (component: Component, zz: Int32Array) => void;

  function decodeBaseline(component: Component, zz: Int32Array) {
    const t = decodeHuffman(component.huffmanTableDC!);
    const diff = t === 0 ? 0 : receiveAndExtend(t);
    zz[0] = (component.pred += diff);
    let k = 1;

    while (k < 64) {
      const rs = decodeHuffman(component.huffmanTableAC!);
      const s = rs & 15;
      const r = rs >> 4;
      if (s === 0) {
        if (r < 15) break;
        k += 16;
        continue;
      }
      k += r;
      const z = dctZigZag[k];
      zz[z] = receiveAndExtend(s);
      k++;
    }
  }

  function decodeDCFirst(component: Component, zz: Int32Array) {
    const t = decodeHuffman(component.huffmanTableDC!);
    const diff = t === 0 ? 0 : (receiveAndExtend(t) << successive);
    zz[0] = (component.pred += diff);
  }

  function decodeDCSuccessive(_component: Component, zz: Int32Array) {
    zz[0] |= readBit() << successive;
  }

  let eobrun = 0;

  function decodeACFirst(component: Component, zz: Int32Array) {
    if (eobrun > 0) {
      eobrun--;
      return;
    }
    let k = spectralStart, e = spectralEnd;
    while (k <= e) {
      const rs = decodeHuffman(component.huffmanTableAC!);
      const s = rs & 15;
      const r = rs >> 4;
      if (s === 0) {
        if (r < 15) {
          eobrun = receive(r) + (1 << r) - 1;
          break;
        }
        k += 16;
        continue;
      }
      k += r;
      const z = dctZigZag[k];
      zz[z] = receiveAndExtend(s) * (1 << successive);
      k++;
    }
  }

  let successiveACState = 0;
  let successiveACNextValue = 0;

  function decodeACSuccessive(component: Component, zz: Int32Array) {
    let k = spectralStart;
    let e = spectralEnd;
    let r = 0;

    while (k <= e) {
      const z = dctZigZag[k];
      const direction = zz[z] < 0 ? -1 : 1;

      switch (successiveACState) {
        case 0: // initial state
          const rs = decodeHuffman(component.huffmanTableAC!);
          const s = rs & 15;
          r = rs >> 4; // this was new variable in old code
          if (s === 0) {
            if (r < 15) {
              eobrun = receive(r) + (1 << r);
              successiveACState = 4;
            } else {
              r = 16;
              successiveACState = 1;
            }
          } else {
            if (s !== 1) throw new Error('invalid ACn encoding');
            successiveACNextValue = receiveAndExtend(s);
            successiveACState = r ? 2 : 3;
          }
          continue;
        case 1: // skipping r zero items
        case 2:
          if (zz[z]) {
            zz[z] += (readBit() << successive) * direction;
          } else {
            r--;
            if (r === 0) successiveACState = successiveACState == 2 ? 3 : 0;
          }
          break;
        case 3: // set value for a zero item
          if (zz[z]) {
            zz[z] += (readBit() << successive) * direction;
          } else {
            zz[z] = successiveACNextValue << successive;
            successiveACState = 0;
          }
          break;
        case 4: // eob
          if (zz[z]) {
            zz[z] += (readBit() << successive) * direction;
          }
          break;
      }
      k++;
    }

    if (successiveACState === 4) {
      eobrun--;
      if (eobrun === 0) successiveACState = 0;
    }
  }

  function decodeMcu(component: Component, decode: DecodeFn, mcu: number, row: number, col: number) {
    const mcuRow = (mcu / mcusPerLine) | 0;
    const mcuCol = mcu % mcusPerLine;
    const blockRow = mcuRow * component.v + row;
    const blockCol = mcuCol * component.h + col;
    // If the block is missing, just skip it.
    if (component.blocks[blockRow] === undefined) return;
    decode(component, component.blocks[blockRow][blockCol]);
  }

  function decodeBlock(component: Component, decode: DecodeFn, mcu: number) {
    const blockRow = (mcu / component.blocksPerLine) | 0;
    const blockCol = mcu % component.blocksPerLine;
    // If the block is missing, just skip it.
    if (component.blocks[blockRow] === undefined) return;
    decode(component, component.blocks[blockRow][blockCol]);
  }

  const componentsLength = components.length;
  let component: Component;
  let decodeFn: DecodeFn;

  if (progressive) {
    if (spectralStart === 0) {
      decodeFn = successivePrev === 0 ? decodeDCFirst : decodeDCSuccessive;
    } else {
      decodeFn = successivePrev === 0 ? decodeACFirst : decodeACSuccessive;
    }
  } else {
    decodeFn = decodeBaseline;
  }

  let mcu = 0;
  let mcuExpected: number;

  if (componentsLength == 1) {
    mcuExpected = components[0].blocksPerLine * components[0].blocksPerColumn;
  } else {
    mcuExpected = mcusPerLine * frame.mcusPerColumn;
  }

  if (!resetInterval) resetInterval = mcuExpected;

  let h: number;
  let v: number;
  let marker: number;

  while (mcu < mcuExpected) {
    // reset interval stuff
    for (let i = 0; i < componentsLength; i++) components[i].pred = 0;
    eobrun = 0;

    if (componentsLength == 1) {
      component = components[0];
      for (let n = 0; n < resetInterval; n++) {
        decodeBlock(component, decodeFn, mcu);
        mcu++;
      }
    } else {
      for (let n = 0; n < resetInterval; n++) {
        for (let i = 0; i < componentsLength; i++) {
          component = components[i];
          h = component.h;
          v = component.v;
          for (let j = 0; j < v; j++) {
            for (let k = 0; k < h; k++) {
              decodeMcu(component, decodeFn, mcu, j, k);
            }
          }
        }
        mcu++;

        // If we've reached our expected MCU's, stop decoding
        if (mcu === mcuExpected) break;
      }
    }

    if (mcu === mcuExpected) {
      // Skip trailing bytes at the end of the scan - until we reach the next marker
      do {
        if (data[offset] === 0xFF) {
          if (data[offset + 1] !== 0x00) {
            break;
          }
        }
        offset += 1;
      } while (offset < data.length - 2);
    }

    // find marker
    bitsCount = 0;
    marker = (data[offset] << 8) | data[offset + 1];

    if (marker < 0xFF00) throw new Error('marker was not found');

    if (marker >= 0xFFD0 && marker <= 0xFFD7) { // RSTx
      offset += 2;
    } else {
      break;
    }
  }

  return offset - startOffset;
}

function buildComponentData(component: Component) {
  const lines = [];
  const blocksPerLine = component.blocksPerLine;
  const blocksPerColumn = component.blocksPerColumn;
  const samplesPerLine = blocksPerLine << 3;
  // Only 1 used per invocation of this function and garbage collected after invocation, so no need to account for its memory footprint.
  const R = new Int32Array(64);
  const r = new Uint8Array(64);

  // A port of poppler's IDCT method which in turn is taken from:
  //   Christoph Loeffler, Adriaan Ligtenberg, George S. Moschytz,
  //   "Practical Fast 1-D DCT Algorithms with 11 Multiplications",
  //   IEEE Intl. Conf. on Acoustics, Speech & Signal Processing, 1989,
  //   988-991.
  function quantizeAndInverse(zz: Int32Array, dataOut: Uint8Array, dataIn: Int32Array) {
    const qt = component.quantizationTable!;
    const p = dataIn;

    // dequant
    for (let i = 0; i < 64; i++) {
      p[i] = zz[i] * qt[i];
    }

    // inverse DCT on rows
    for (let i = 0; i < 8; ++i) {
      const row = 8 * i;

      // check for all-zero AC coefficients
      if (p[1 + row] == 0 && p[2 + row] == 0 && p[3 + row] == 0 &&
        p[4 + row] == 0 && p[5 + row] == 0 && p[6 + row] == 0 &&
        p[7 + row] == 0) {
        const t = (dctSqrt2 * p[0 + row] + 512) >> 10;
        p[0 + row] = t;
        p[1 + row] = t;
        p[2 + row] = t;
        p[3 + row] = t;
        p[4 + row] = t;
        p[5 + row] = t;
        p[6 + row] = t;
        p[7 + row] = t;
        continue;
      }

      // stage 4
      let v0 = (dctSqrt2 * p[0 + row] + 128) >> 8;
      let v1 = (dctSqrt2 * p[4 + row] + 128) >> 8;
      let v2 = p[2 + row];
      let v3 = p[6 + row];
      let v4 = (dctSqrt1d2 * (p[1 + row] - p[7 + row]) + 128) >> 8;
      let v7 = (dctSqrt1d2 * (p[1 + row] + p[7 + row]) + 128) >> 8;
      let v5 = p[3 + row] << 4;
      let v6 = p[5 + row] << 4;

      // stage 3
      let t = (v0 - v1 + 1) >> 1;
      v0 = (v0 + v1 + 1) >> 1;
      v1 = t;
      t = (v2 * dctSin6 + v3 * dctCos6 + 128) >> 8;
      v2 = (v2 * dctCos6 - v3 * dctSin6 + 128) >> 8;
      v3 = t;
      t = (v4 - v6 + 1) >> 1;
      v4 = (v4 + v6 + 1) >> 1;
      v6 = t;
      t = (v7 + v5 + 1) >> 1;
      v5 = (v7 - v5 + 1) >> 1;
      v7 = t;

      // stage 2
      t = (v0 - v3 + 1) >> 1;
      v0 = (v0 + v3 + 1) >> 1;
      v3 = t;
      t = (v1 - v2 + 1) >> 1;
      v1 = (v1 + v2 + 1) >> 1;
      v2 = t;
      t = (v4 * dctSin3 + v7 * dctCos3 + 2048) >> 12;
      v4 = (v4 * dctCos3 - v7 * dctSin3 + 2048) >> 12;
      v7 = t;
      t = (v5 * dctSin1 + v6 * dctCos1 + 2048) >> 12;
      v5 = (v5 * dctCos1 - v6 * dctSin1 + 2048) >> 12;
      v6 = t;

      // stage 1
      p[0 + row] = v0 + v7;
      p[7 + row] = v0 - v7;
      p[1 + row] = v1 + v6;
      p[6 + row] = v1 - v6;
      p[2 + row] = v2 + v5;
      p[5 + row] = v2 - v5;
      p[3 + row] = v3 + v4;
      p[4 + row] = v3 - v4;
    }

    // inverse DCT on columns
    for (let i = 0; i < 8; ++i) {
      const col = i;

      // check for all-zero AC coefficients
      if (p[1 * 8 + col] == 0 && p[2 * 8 + col] == 0 && p[3 * 8 + col] == 0 &&
        p[4 * 8 + col] == 0 && p[5 * 8 + col] == 0 && p[6 * 8 + col] == 0 &&
        p[7 * 8 + col] == 0) {
        const t = (dctSqrt2 * dataIn[i + 0] + 8192) >> 14;
        p[0 * 8 + col] = t;
        p[1 * 8 + col] = t;
        p[2 * 8 + col] = t;
        p[3 * 8 + col] = t;
        p[4 * 8 + col] = t;
        p[5 * 8 + col] = t;
        p[6 * 8 + col] = t;
        p[7 * 8 + col] = t;
        continue;
      }

      // stage 4
      let v0 = (dctSqrt2 * p[0 * 8 + col] + 2048) >> 12;
      let v1 = (dctSqrt2 * p[4 * 8 + col] + 2048) >> 12;
      let v2 = p[2 * 8 + col];
      let v3 = p[6 * 8 + col];
      let v4 = (dctSqrt1d2 * (p[1 * 8 + col] - p[7 * 8 + col]) + 2048) >> 12;
      let v7 = (dctSqrt1d2 * (p[1 * 8 + col] + p[7 * 8 + col]) + 2048) >> 12;
      let v5 = p[3 * 8 + col];
      let v6 = p[5 * 8 + col];

      // stage 3
      let t = (v0 - v1 + 1) >> 1;
      v0 = (v0 + v1 + 1) >> 1;
      v1 = t;
      t = (v2 * dctSin6 + v3 * dctCos6 + 2048) >> 12;
      v2 = (v2 * dctCos6 - v3 * dctSin6 + 2048) >> 12;
      v3 = t;
      t = (v4 - v6 + 1) >> 1;
      v4 = (v4 + v6 + 1) >> 1;
      v6 = t;
      t = (v7 + v5 + 1) >> 1;
      v5 = (v7 - v5 + 1) >> 1;
      v7 = t;

      // stage 2
      t = (v0 - v3 + 1) >> 1;
      v0 = (v0 + v3 + 1) >> 1;
      v3 = t;
      t = (v1 - v2 + 1) >> 1;
      v1 = (v1 + v2 + 1) >> 1;
      v2 = t;
      t = (v4 * dctSin3 + v7 * dctCos3 + 2048) >> 12;
      v4 = (v4 * dctCos3 - v7 * dctSin3 + 2048) >> 12;
      v7 = t;
      t = (v5 * dctSin1 + v6 * dctCos1 + 2048) >> 12;
      v5 = (v5 * dctCos1 - v6 * dctSin1 + 2048) >> 12;
      v6 = t;

      // stage 1
      p[0 * 8 + col] = v0 + v7;
      p[7 * 8 + col] = v0 - v7;
      p[1 * 8 + col] = v1 + v6;
      p[6 * 8 + col] = v1 - v6;
      p[2 * 8 + col] = v2 + v5;
      p[5 * 8 + col] = v2 - v5;
      p[3 * 8 + col] = v3 + v4;
      p[4 * 8 + col] = v3 - v4;
    }

    // convert to 8-bit integers
    for (let i = 0; i < 64; ++i) {
      const sample = 128 + ((p[i] + 8) >> 4);
      dataOut[i] = sample < 0 ? 0 : sample > 0xFF ? 0xFF : sample;
    }
  }

  requestMemoryAllocation(samplesPerLine * blocksPerColumn * 8);

  for (let blockRow = 0; blockRow < blocksPerColumn; blockRow++) {
    const scanLine = blockRow << 3;

    for (let i = 0; i < 8; i++)
      lines.push(new Uint8Array(samplesPerLine));

    for (let blockCol = 0; blockCol < blocksPerLine; blockCol++) {
      quantizeAndInverse(component.blocks[blockRow][blockCol], r, R);

      let offset = 0;
      const sample = blockCol << 3;
      for (let j = 0; j < 8; j++) {
        const line = lines[scanLine + j];
        for (let i = 0; i < 8; i++)
          line[sample + i] = r[offset++];
      }
    }
  }
  return lines;
}

function clampTo8bit(a: number) {
  return a < 0 ? 0 : a > 255 ? 255 : a;
}

function parse(data: Uint8Array) {
  const self: Decoded = {
    width: 0,
    height: 0,
    comments: [],
    adobe: undefined,
    components: [],
    exifBuffer: undefined,
    jfif: undefined,
  };

  const maxResolutionInPixels = maxResolutionInMP * 1000 * 1000;
  let offset = 0;

  function readUint16() {
    const value = (data[offset] << 8) | data[offset + 1];
    offset += 2;
    return value;
  }

  function readDataBlock() {
    const length = readUint16();
    const array = data.subarray(offset, offset + length - 2);
    offset += array.length;
    return array;
  }

  function prepareComponents(frame: Frame) {
    let maxH = 0, maxV = 0;

    for (let componentId in frame.components) {
      if (frame.components.hasOwnProperty(componentId)) {
        const component = frame.components[componentId];
        if (maxH < component.h) maxH = component.h;
        if (maxV < component.v) maxV = component.v;
      }
    }

    const mcusPerLine = Math.ceil(frame.samplesPerLine / 8 / maxH);
    const mcusPerColumn = Math.ceil(frame.scanLines / 8 / maxV);

    for (let componentId in frame.components) {
      if (frame.components.hasOwnProperty(componentId)) {
        const component = frame.components[componentId];
        const blocksPerLine = Math.ceil(Math.ceil(frame.samplesPerLine / 8) * component.h / maxH);
        const blocksPerColumn = Math.ceil(Math.ceil(frame.scanLines / 8) * component.v / maxV);
        const blocksPerLineForMcu = mcusPerLine * component.h;
        const blocksPerColumnForMcu = mcusPerColumn * component.v;
        const blocksToAllocate = blocksPerColumnForMcu * blocksPerLineForMcu;
        const blocks: Int32Array[][] = [];

        // Each block is a Int32Array of length 64 (4 x 64 = 256 bytes)
        requestMemoryAllocation(blocksToAllocate * 256);

        for (let i = 0; i < blocksPerColumnForMcu; i++) {
          const row: Int32Array[] = [];
          for (let j = 0; j < blocksPerLineForMcu; j++) {
            row.push(new Int32Array(64));
          }
          blocks.push(row);
        }
        component.blocksPerLine = blocksPerLine;
        component.blocksPerColumn = blocksPerColumn;
        component.blocks = blocks;
      }
    }

    frame.maxH = maxH;
    frame.maxV = maxV;
    frame.mcusPerLine = mcusPerLine;
    frame.mcusPerColumn = mcusPerColumn;
  }

  let jfif = null;
  let adobe = null;
  let frame: Frame | undefined = undefined;
  let resetInterval = 0;
  let quantizationTables = [];
  let frames: Frame[] = [];
  let huffmanTablesAC: (number[] | number[][])[] = [];
  let huffmanTablesDC: (number[] | number[][])[] = [];
  let fileMarker = readUint16();
  let malformedDataOffset = -1;

  if (fileMarker != 0xFFD8) { // SOI (Start of Image)
    throw new Error('SOI not found');
  }

  fileMarker = readUint16();
  while (fileMarker != 0xFFD9) { // EOI (End of image)
    switch (fileMarker) {
      case 0xFF00: break;
      case 0xFFE0: // APP0 (Application Specific)
      case 0xFFE1: // APP1
      case 0xFFE2: // APP2
      case 0xFFE3: // APP3
      case 0xFFE4: // APP4
      case 0xFFE5: // APP5
      case 0xFFE6: // APP6
      case 0xFFE7: // APP7
      case 0xFFE8: // APP8
      case 0xFFE9: // APP9
      case 0xFFEA: // APP10
      case 0xFFEB: // APP11
      case 0xFFEC: // APP12
      case 0xFFED: // APP13
      case 0xFFEE: // APP14
      case 0xFFEF: // APP15
      case 0xFFFE: { // COM (Comment)
        const appData = readDataBlock();

        if (fileMarker === 0xFFFE) {
          let comment = '';
          for (let ii = 0; ii < appData.byteLength; ii++) {
            comment += String.fromCharCode(appData[ii]);
          }
          self.comments.push(comment);
        }

        if (fileMarker === 0xFFE0) {
          if (appData[0] === 0x4A && appData[1] === 0x46 && appData[2] === 0x49 &&
            appData[3] === 0x46 && appData[4] === 0) { // 'JFIF\x00'
            jfif = {
              version: { major: appData[5], minor: appData[6] },
              densityUnits: appData[7],
              xDensity: (appData[8] << 8) | appData[9],
              yDensity: (appData[10] << 8) | appData[11],
              thumbWidth: appData[12],
              thumbHeight: appData[13],
              thumbData: appData.subarray(14, 14 + 3 * appData[12] * appData[13])
            };
          }
        }
        // TODO APP1 - Exif
        if (fileMarker === 0xFFE1) {
          if (appData[0] === 0x45 &&
            appData[1] === 0x78 &&
            appData[2] === 0x69 &&
            appData[3] === 0x66 &&
            appData[4] === 0) { // 'EXIF\x00'
            self.exifBuffer = appData.subarray(5, appData.length);
          }
        }

        if (fileMarker === 0xFFEE) {
          if (appData[0] === 0x41 && appData[1] === 0x64 && appData[2] === 0x6F &&
            appData[3] === 0x62 && appData[4] === 0x65 && appData[5] === 0) { // 'Adobe\x00'
            adobe = {
              version: appData[6],
              flags0: (appData[7] << 8) | appData[8],
              flags1: (appData[9] << 8) | appData[10],
              transformCode: appData[11]
            };
          }
        }
        break;
      }
      case 0xFFDB: { // DQT (Define Quantization Tables)
        const quantizationTablesLength = readUint16();
        const quantizationTablesEnd = quantizationTablesLength + offset - 2;
        while (offset < quantizationTablesEnd) {
          const quantizationTableSpec = data[offset++];
          requestMemoryAllocation(64 * 4);
          const tableData = new Int32Array(64);
          if ((quantizationTableSpec >> 4) === 0) { // 8 bit values
            for (let j = 0; j < 64; j++) {
              const z = dctZigZag[j];
              tableData[z] = data[offset++];
            }
          } else if ((quantizationTableSpec >> 4) === 1) { //16 bit
            for (let j = 0; j < 64; j++) {
              const z = dctZigZag[j];
              tableData[z] = readUint16();
            }
          } else
            throw new Error('DQT: invalid table spec');
          quantizationTables[quantizationTableSpec & 15] = tableData;
        }
        break;
      }
      case 0xFFC0: // SOF0 (Start of Frame, Baseline DCT)
      case 0xFFC1: // SOF1 (Start of Frame, Extended DCT)
      case 0xFFC2: { // SOF2 (Start of Frame, Progressive DCT)
        readUint16(); // skip data length
        frame = {
          extended: (fileMarker === 0xFFC1),
          progressive: (fileMarker === 0xFFC2),
          precision: data[offset++],
          scanLines: readUint16(),
          samplesPerLine: readUint16(),
          components: {},
          componentsOrder: [],
          maxH: 0,
          maxV: 0,
          mcusPerLine: 0,
          mcusPerColumn: 0,
        };

        const pixelsInFrame = frame!.scanLines * frame!.samplesPerLine;
        if (pixelsInFrame > maxResolutionInPixels) {
          const exceededAmount = Math.ceil((pixelsInFrame - maxResolutionInPixels) / 1e6);
          throw new Error(`maxResolutionInMP limit exceeded by ${exceededAmount}MP`);
        }

        const componentsCount = data[offset++];

        for (let i = 0; i < componentsCount; i++) {
          const componentId = data[offset];
          const h = data[offset + 1] >> 4;
          const v = data[offset + 1] & 15;
          const qId = data[offset + 2];
          frame!.componentsOrder.push(componentId);
          frame!.components[componentId] = {
            h: h,
            v: v,
            quantizationIdx: qId,
            blocksPerColumn: 0,
            blocksPerLine: 0,
            blocks: [],
            pred: 0,
          };
          offset += 3;
        }
        prepareComponents(frame!);
        frames.push(frame);
        break;
      }
      case 0xFFC4: {// DHT (Define Huffman Tables)
        const huffmanLength = readUint16();

        for (let i = 2; i < huffmanLength;) {
          const huffmanTableSpec = data[offset++];
          const codeLengths = new Uint8Array(16);
          let codeLengthSum = 0;

          for (let j = 0; j < 16; j++, offset++) {
            codeLengthSum += (codeLengths[j] = data[offset]);
          }

          requestMemoryAllocation(16 + codeLengthSum);
          const huffmanValues = new Uint8Array(codeLengthSum);

          for (let j = 0; j < codeLengthSum; j++, offset++) {
            huffmanValues[j] = data[offset];
          }

          i += 17 + codeLengthSum;

          const index = huffmanTableSpec & 15;
          const table = (huffmanTableSpec >> 4) === 0 ? huffmanTablesDC : huffmanTablesAC;
          table[index] = buildHuffmanTable(codeLengths, huffmanValues);
        }
        break;
      }
      case 0xFFDD: // DRI (Define Restart Interval)
        readUint16(); // skip data length
        resetInterval = readUint16();
        break;
      case 0xFFDC: // Number of Lines marker
        readUint16() // skip data length
        readUint16() // Ignore this data since it represents the image height
        break;
      case 0xFFDA: { // SOS (Start of Scan)
        readUint16(); // skip data length
        const selectorsCount = data[offset++];
        const components: Component[] = [];
        for (let i = 0; i < selectorsCount; i++) {
          const component = frame!.components[data[offset++]];
          const tableSpec = data[offset++];
          component.huffmanTableDC = huffmanTablesDC[tableSpec >> 4];
          component.huffmanTableAC = huffmanTablesAC[tableSpec & 15];
          components.push(component);
        }
        const spectralStart = data[offset++];
        const spectralEnd = data[offset++];
        const successiveApproximation = data[offset++];
        const processed = decodeScan(
          data, offset, frame!, components, resetInterval, spectralStart, spectralEnd,
          successiveApproximation >> 4, successiveApproximation & 15);
        offset += processed;
        break;
      }
      case 0xFFFF: // Fill bytes
        if (data[offset] !== 0xFF) { // Avoid skipping a valid marker.
          offset--;
        }
        break;
      default: {
        if (data[offset - 3] == 0xFF && data[offset - 2] >= 0xC0 && data[offset - 2] <= 0xFE) {
          // could be incorrect encoding -- last 0xFF byte of the previous
          // block was eaten by the encoder
          offset -= 3;
          break;
        } else if (fileMarker === 0xE0 || fileMarker == 0xE1) {
          // Recover from malformed APP1 markers popular in some phone models.
          // See https://github.com/eugeneware/jpeg-js/issues/82
          if (malformedDataOffset !== -1) {
            throw new Error(`first unknown JPEG marker at offset ${malformedDataOffset.toString(16)}, second unknown JPEG marker ${fileMarker.toString(16)} at offset ${(offset - 1).toString(16)}`);
          }
          malformedDataOffset = offset - 1;
          const nextOffset = readUint16();
          if (data[offset + nextOffset - 2] === 0xFF) {
            offset += nextOffset - 2;
            break;
          }
        }

        throw new Error('unknown JPEG marker ' + fileMarker.toString(16));
      }
    }

    fileMarker = readUint16();
  }

  if (frames.length != 1) throw new Error('only single frame JPEGs supported');

  // set each frame's components quantization table
  for (let i = 0; i < frames.length; i++) {
    const cp = frames[i].components;
    for (let j in cp) { // TODO: don't use `in`
      cp[j].quantizationTable = quantizationTables[cp[j].quantizationIdx!];
      delete cp[j].quantizationIdx; // TODO: why ???
    }
  }

  self.width = frame!.samplesPerLine;
  self.height = frame!.scanLines;
  self.jfif = jfif;
  self.adobe = adobe;
  self.components = [];

  for (let i = 0; i < frame!.componentsOrder.length; i++) {
    const component = frame!.components[frame!.componentsOrder[i]];
    self.components.push({
      lines: buildComponentData(component),
      scaleX: component.h / frame!.maxH,
      scaleY: component.v / frame!.maxV
    });
  }

  return self;
}

function getData(decoded: Decoded) {
  let offset = 0;
  let colorTransform = false;

  const width = decoded.width;
  const height = decoded.height;
  const dataLength = width * height * decoded.components.length;
  requestMemoryAllocation(dataLength);
  const data = new Uint8Array(dataLength);

  switch (decoded.components.length) {
    case 1: {
      const component1 = decoded.components[0];

      for (let y = 0; y < height; y++) {
        const component1Line = component1.lines[0 | (y * component1.scaleY)];

        for (let x = 0; x < width; x++) {
          const Y = component1Line[0 | (x * component1.scaleX)];
          data[offset++] = Y;
        }
      }
      break;
    }
    case 2: {
      // PDF might compress two component data in custom colorspace
      const component1 = decoded.components[0];
      const component2 = decoded.components[1];

      for (let y = 0; y < height; y++) {
        const component1Line = component1.lines[0 | (y * component1.scaleY)];
        const component2Line = component2.lines[0 | (y * component2.scaleY)];

        for (let x = 0; x < width; x++) {
          const Y1 = component1Line[0 | (x * component1.scaleX)];
          data[offset++] = Y1;
          const Y2 = component2Line[0 | (x * component2.scaleX)];
          data[offset++] = Y2;
        }
      }
      break;
    }
    case 3: {
      // The default transform for three components is true
      colorTransform = true;
      // The adobe transform marker overrides any previous setting
      if (decoded.adobe && decoded.adobe.transformCode) colorTransform = true;

      const component1 = decoded.components[0];
      const component2 = decoded.components[1];
      const component3 = decoded.components[2];

      for (let y = 0; y < height; y++) {
        const component1Line = component1.lines[0 | (y * component1.scaleY)];
        const component2Line = component2.lines[0 | (y * component2.scaleY)];
        const component3Line = component3.lines[0 | (y * component3.scaleY)];

        for (let x = 0; x < width; x++) {
          let Y, Cb, Cr, R, G, B;

          if (!colorTransform) {
            R = component1Line[0 | (x * component1.scaleX)];
            G = component2Line[0 | (x * component2.scaleX)];
            B = component3Line[0 | (x * component3.scaleX)];
          } else {
            Y = component1Line[0 | (x * component1.scaleX)];
            Cb = component2Line[0 | (x * component2.scaleX)];
            Cr = component3Line[0 | (x * component3.scaleX)];

            R = clampTo8bit(Y + 1.402 * (Cr - 128));
            G = clampTo8bit(Y - 0.3441363 * (Cb - 128) - 0.71413636 * (Cr - 128));
            B = clampTo8bit(Y + 1.772 * (Cb - 128));
          }

          data[offset++] = R;
          data[offset++] = G;
          data[offset++] = B;
        }
      }
      break;
    }
    case 4: {
      if (!decoded.adobe) throw new Error('Unsupported color mode (4 components)');
      // The default transform for four components is false
      colorTransform = false;
      // The adobe transform marker overrides any previous setting
      if (decoded.adobe && decoded.adobe.transformCode) colorTransform = true;

      const component1 = decoded.components[0];
      const component2 = decoded.components[1];
      const component3 = decoded.components[2];
      const component4 = decoded.components[3];

      for (let y = 0; y < height; y++) {
        const component1Line = component1.lines[0 | (y * component1.scaleY)];
        const component2Line = component2.lines[0 | (y * component2.scaleY)];
        const component3Line = component3.lines[0 | (y * component3.scaleY)];
        const component4Line = component4.lines[0 | (y * component4.scaleY)];

        for (let x = 0; x < width; x++) {
          let Y, Cb, Cr, K, C, M, Ye;

          if (!colorTransform) {
            C = component1Line[0 | (x * component1.scaleX)];
            M = component2Line[0 | (x * component2.scaleX)];
            Ye = component3Line[0 | (x * component3.scaleX)];
            K = component4Line[0 | (x * component4.scaleX)];
          } else {
            Y = component1Line[0 | (x * component1.scaleX)];
            Cb = component2Line[0 | (x * component2.scaleX)];
            Cr = component3Line[0 | (x * component3.scaleX)];
            K = component4Line[0 | (x * component4.scaleX)];

            C = 255 - clampTo8bit(Y + 1.402 * (Cr - 128));
            M = 255 - clampTo8bit(Y - 0.3441363 * (Cb - 128) - 0.71413636 * (Cr - 128));
            Ye = 255 - clampTo8bit(Y + 1.772 * (Cb - 128));
          }
          data[offset++] = 255 - C;
          data[offset++] = 255 - M;
          data[offset++] = 255 - Ye;
          data[offset++] = 255 - K;
        }
      }
      break;
    }
    default:
      throw new Error('Unsupported color mode');
  }

  return data;
}

export function decodeJpeg(encoded: Uint8Array, createImageData: (width: number, height: number) => ImageData) {
  totalBytesAllocated = 0;

  if (encoded.length === 0) throw new Error('Empty jpeg buffer');

  const decoded = parse(encoded);
  requestMemoryAllocation(decoded.width * decoded.height * 4);

  const data = getData(decoded);

  const imageData = createImageData(decoded.width, decoded.height);
  const width = imageData.width;
  const height = imageData.height;
  const imageDataArray = imageData.data;

  let i = 0;
  let j = 0;

  switch (decoded.components.length) {
    case 1:
      for (let y = 0; y < height; y++) {
        for (let x = 0; x < width; x++) {
          const Y = data[i++];

          imageDataArray[j++] = Y;
          imageDataArray[j++] = Y;
          imageDataArray[j++] = Y;
          imageDataArray[j++] = 255;
        }
      }
      break;
    case 3:
      for (let y = 0; y < height; y++) {
        for (let x = 0; x < width; x++) {
          const R = data[i++];
          const G = data[i++];
          const B = data[i++];

          imageDataArray[j++] = R;
          imageDataArray[j++] = G;
          imageDataArray[j++] = B;
          imageDataArray[j++] = 255;
        }
      }
      break;
    case 4:
      for (let y = 0; y < height; y++) {
        for (let x = 0; x < width; x++) {
          const C = data[i++];
          const M = data[i++];
          const Y = data[i++];
          const K = data[i++];

          const R = 255 - clampTo8bit(C * (1 - K / 255) + K);
          const G = 255 - clampTo8bit(M * (1 - K / 255) + K);
          const B = 255 - clampTo8bit(Y * (1 - K / 255) + K);

          imageDataArray[j++] = R;
          imageDataArray[j++] = G;
          imageDataArray[j++] = B;
          imageDataArray[j++] = 255;
        }
      }
      break;
    default:
      throw new Error('Unsupported color mode');
  }

  return imageData;
}