/* eslint-disable camelcase */
// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.

import sanitize from 'sanitize-html';
import { IRenderMime } from '@jupyterlab/rendermime-interfaces';

/**
 * Helper class that contains regular expressions for inline CSS style validation.
 *
 * Which properties (and values) to allow is largely based on the Google Caja project:
 *   https://github.com/google/caja
 *
 * The regular expressions are largly based on the syntax definition found at
 * https://developer.mozilla.org/en-US/docs/Web/CSS.
 */
class CssProp {
  static reg(r: string): RegExp {
    return new RegExp('^' + r + '$', 'i');
  }

  /*
   * Numeric base expressions used to help build more complex regular expressions
   */
  private static readonly N = {
    integer: `[+-]?[0-9]+`,
    integer_pos: `[+]?[0-9]+`,
    integer_zero_ff: `([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])`,
    number: `[+-]?([0-9]*[.])?[0-9]+(e-?[0-9]*)?`,
    number_pos: `[+]?([0-9]*[.])?[0-9]+(e-?[0-9]*)?`,
    number_zero_hundred: `[+]?(([0-9]|[1-9][0-9])([.][0-9]+)?|100)`,
    number_zero_one: `[+]?(1([.][0]+)?|0?([.][0-9]+)?)`
  };

  /*
   * Base expressions of common CSS syntax elements
   */
  private static readonly B = {
    angle: `(${CssProp.N.number}(deg|rad|grad|turn)|0)`,
    frequency: `${CssProp.N.number}(Hz|kHz)`,
    ident: String.raw`-?([_a-z]|[\xA0-\xFF]|\\[0-9a-f]{1,6}(\r\n|[ \t\r\n\f])?|\\[^\r\n\f0-9a-f])([_a-z0-9-]|[\xA0-\xFF]|\\[0-9a-f]{1,6}(\r\n|[ \t\r\n\f])?|\\[^\r\n\f0-9a-f])*`,
    len_or_perc: `(0|${CssProp.N.number}(px|em|rem|ex|in|cm|mm|pt|pc|%))`,
    length: `(${CssProp.N.number}(px|em|rem|ex|in|cm|mm|pt|pc)|0)`,
    length_pos: `(${CssProp.N.number_pos}(px|em|rem|ex|in|cm|mm|pt|pc)|0)`,
    percentage: `${CssProp.N.number}%`,
    percentage_pos: `${CssProp.N.number_pos}%`,
    percentage_zero_hundred: `${CssProp.N.number_zero_hundred}%`,
    string: String.raw`(\"([^\n\r\f\\"]|\\\n|\r\n|\r|\f|\\[0-9a-f]{1,6}(\r\n|[ \t\r\n\f])?|\\[^\r\n\f0-9a-f])*\")|(\'([^\n\r\f\\']|\\\n|\r\n|\r|\f|\\[0-9a-f]{1,6}(\r\n|[ \t\r\n\f])?|\\[^\r\n\f0-9a-f])*\')`,
    time: `${CssProp.N.number}(s|ms)`,
    url: `url\\(.*?\\)`,
    z_index: `[+-]?[0-9]{1,7}`
  };

  /*
   * Atomic (i.e. not dependent on other regular expressions) sub RegEx segments
   */
  private static readonly A = {
    absolute_size: `xx-small|x-small|small|medium|large|x-large|xx-large`,
    attachment: `scroll|fixed|local`,
    bg_origin: `border-box|padding-box|content-box`,
    border_style: `none|hidden|dotted|dashed|solid|double|groove|ridge|inset|outset`,
    box: `border-box|padding-box|content-box`,
    display_inside: `auto|block|table|flex|grid`,
    display_outside: `block-level|inline-level|none|table-row-group|table-header-group|table-footer-group|table-row|table-cell|table-column-group|table-column|table-caption`,
    ending_shape: `circle|ellipse`,
    generic_family: `serif|sans-serif|cursive|fantasy|monospace`,
    generic_voice: `male|female|child`,
    relative_size: `smaller|larger`,
    repeat_style: `repeat-x|repeat-y|((?:repeat|space|round|no-repeat)(?:\\s*(?:repeat|space|round|no-repeat))?)`,
    side_or_corner: `(left|right)?\\s*(top|bottom)?`,
    single_animation_direction: `normal|reverse|alternate|alternate-reverse`,
    single_animation_fill_mode: `none|forwards|backwards|both`,
    single_animation_play_state: `running|paused`
  };

  /*
   * Color definition sub expressions
   */
  private static readonly _COLOR = {
    hex: `\\#(0x)?[0-9a-f]+`,
    name: `aliceblue|antiquewhite|aqua|aquamarine|azure|beige|bisque|black|blanchedalmond|blue|blueviolet|brown|burlywood|cadetblue|chartreuse|chocolate|coral|cornflowerblue|cornsilk|crimson|cyan|darkblue|darkcyan|darkgoldenrod|darkgray|darkgreen|darkkhaki|darkmagenta|darkolivegreen|darkorange|darkorchid|darkred|darksalmon|darkseagreen|darkslateblue|darkslategray|darkturquoise|darkviolet|deeppink|deepskyblue|dimgray|dodgerblue|firebrick|floralwhite|forestgreen|fuchsia|gainsboro|ghostwhite|gold|goldenrod|gray|green|greenyellow|honeydew|hotpink|indianred|indigo|ivory|khaki|lavender|lavenderblush|lawngreen|lemonchiffon|lightblue|lightcoral|lightcyan|lightgoldenrodyellow|lightgreen|lightgrey|lightpink|lightsalmon|lightseagreen|lightskyblue|lightslategray|lightsteelblue|lightyellow|lime|limegreen|linen|magenta|maroon|mediumaquamarine|mediumblue|mediumorchid|mediumpurple|mediumseagreen|mediumslateblue|mediumspringgreen|mediumturquoise|mediumvioletred|midnightblue|mintcream|mistyrose|moccasin|navajowhite|navy|oldlace|olive|olivedrab|orange|orangered|orchid|palegoldenrod|palegreen|paleturquoise|palevioletred|papayawhip|peachpuff|peru|pink|plum|powderblue|purple|red|rosybrown|royalblue|saddlebrown|salmon|sandybrown|seagreen|seashell|sienna|silver|skyblue|slateblue|slategray|snow|springgreen|steelblue|tan|teal|thistle|tomato|turquoise|transparent|violet|wheat|white|whitesmoke|yellow|yellowgreen`,
    rgb: String.raw`rgb\(\s*(\d{1,3})\s*,\s*(\d{1,3})\s*,\s*(\d{1,3})\s*\)`,
    rgba: String.raw`rgba\(\s*(\d{1,3})\s*,\s*(\d{1,3})\s*,\s*(\d{1,3})\s*,\s*(${CssProp.N.integer_zero_ff}|${CssProp.N.number_zero_one}|${CssProp.B.percentage_zero_hundred})\s*\)`
  };

  /*
   * Compound (i.e. dependent on other (sub) regular expressions) sub RegEx segments
   */
  private static readonly _C = {
    alpha: `${CssProp.N.integer_zero_ff}|${CssProp.N.number_zero_one}|${CssProp.B.percentage_zero_hundred}`,
    alphavalue: CssProp.N.number_zero_one,
    bg_position: `((${CssProp.B.len_or_perc}|left|center|right|top|bottom)\\s*){1,4}`,
    bg_size: `(${CssProp.B.length_pos}|${CssProp.B.percentage}|auto){1,2}|cover|contain`,
    border_width: `thin|medium|thick|${CssProp.B.length}`,
    bottom: `${CssProp.B.length}|auto`,
    color: `${CssProp._COLOR.hex}|${CssProp._COLOR.rgb}|${CssProp._COLOR.rgba}|${CssProp._COLOR.name}`,
    color_stop_length: `(${CssProp.B.len_or_perc}\\s*){1,2}`,
    linear_color_hint: `${CssProp.B.len_or_perc}`,
    family_name: `${CssProp.B.string}|(${CssProp.B.ident}\\s*)+`,
    image_decl: CssProp.B.url,
    left: `${CssProp.B.length}|auto`,
    loose_quotable_words: `(${CssProp.B.ident})+`,
    margin_width: `${CssProp.B.len_or_perc}|auto`,
    padding_width: `${CssProp.B.length_pos}|${CssProp.B.percentage_pos}`,
    page_url: CssProp.B.url,
    position: `((${CssProp.B.len_or_perc}|left|center|right|top|bottom)\\s*){1,4}`,
    right: `${CssProp.B.length}|auto`,
    shadow: '',
    size: `closest-side|farthest-side|closest-corner|farthest-corner|${CssProp.B.length}|(${CssProp.B.len_or_perc})\\s+(${CssProp.B.len_or_perc})`,
    top: `${CssProp.B.length}|auto`
  };

  private static readonly _C1 = {
    image_list: `image\\(\\s*(${CssProp.B.url})*\\s*(${CssProp.B.url}|${CssProp._C.color})\\s*\\)`,
    linear_color_stop: `(${CssProp._C.color})(\\s*${CssProp._C.color_stop_length})?`,
    shadow: `((${CssProp._C.color})\\s+((${CssProp.B.length})\\s*){2,4}(\s+inset)?)|((inset\\s+)?((${CssProp.B.length})\\s*){2,4}\\s*(${CssProp._C.color})?)`
  };

  private static readonly _C2 = {
    color_stop_list: `((${CssProp._C1.linear_color_stop})(\\s*(${CssProp._C.linear_color_hint}))?\\s*,\\s*)+(${CssProp._C1.linear_color_stop})`,
    shape: `rect\\(\\s*(${CssProp._C.top})\\s*,\\s*(${CssProp._C.right})\\s*,\\s*(${CssProp._C.bottom})\\s*,\\s*(${CssProp._C.left})\\s*\\)`
  };

  private static readonly _C3 = {
    linear_gradient: `linear-gradient\\((((${CssProp.B.angle})|to\\s+(${CssProp.A.side_or_corner}))\\s*,\\s*)?\\s*(${CssProp._C2.color_stop_list})\\s*\\)`,
    radial_gradient: `radial-gradient\\(((((${CssProp.A.ending_shape})|(${CssProp._C.size}))\\s*)*\\s*(at\\s+${CssProp._C.position})?\\s*,\\s*)?\\s*(${CssProp._C2.color_stop_list})\\s*\\)`
  };

  private static readonly _C4 = {
    image: `${CssProp.B.url}|${CssProp._C3.linear_gradient}|${CssProp._C3.radial_gradient}|${CssProp._C1.image_list}`,
    bg_image: `(${CssProp.B.url}|${CssProp._C3.linear_gradient}|${CssProp._C3.radial_gradient}|${CssProp._C1.image_list})|none`
  };

  private static readonly C = {
    ...CssProp._C,
    ...CssProp._C1,
    ...CssProp._C2,
    ...CssProp._C3,
    ...CssProp._C4
  };

  /*
   * Property value regular expressions not dependent on other sub expressions
   */
  private static readonly AP = {
    border_collapse: `collapse|separate`,
    box: `normal|none|contents`,
    box_sizing: `content-box|padding-box|border-box`,
    caption_side: `top|bottom`,
    clear: `none|left|right|both`,
    direction: `ltr|rtl`,
    empty_cells: `show|hide`,
    float: `left|right|none`,
    font_stretch: `normal|wider|narrower|ultra-condensed|extra-condensed|condensed|semi-condensed|semi-expanded|expanded|extra-expanded|ultra-expanded`,
    font_style: `normal|italic|oblique`,
    font_variant: `normal|small-caps`,
    font_weight: `normal|bold|bolder|lighter|100|200|300|400|500|600|700|800|900`,
    list_style_position: `inside|outside`,
    list_style_type: `disc|circle|square|decimal|decimal-leading-zero|lower-roman|upper-roman|lower-greek|lower-latin|upper-latin|armenian|georgian|lower-alpha|upper-alpha|none`,
    overflow: `visible|hidden|scroll|auto`,
    overflow_wrap: `normal|break-word`,
    overflow_x: `visible|hidden|scroll|auto|no-display|no-content`,
    page_break_after: `auto|always|avoid|left|right`,
    page_break_before: `auto|always|avoid|left|right`,
    page_break_inside: `avoid|auto`,
    position: `static|relative|absolute`,
    resize: `none|both|horizontal|vertical`,
    speak: `normal|none|spell-out`,
    speak_header: `once|always`,
    speak_numeral: `digits|continuous`,
    speak_punctuation: `code|none`,
    table_layout: `auto|fixed`,
    text_align: `left|right|center|justify`,
    text_decoration: `none|((underline|overline|line-through|blink)\\s*)+`,
    text_transform: `capitalize|uppercase|lowercase|none`,
    text_wrap: `normal|unrestricted|none|suppress`,
    unicode_bidi: `normal|embed|bidi-override`,
    visibility: `visible|hidden|collapse`,
    white_space: `normal|pre|nowrap|pre-wrap|pre-line`,
    word_break: `normal|keep-all|break-all`
  };

  /*
   * Compound propertiy value regular expressions (i.e. dependent on other sub expressions)
   */
  private static readonly _CP = {
    background_attachment: `${CssProp.A.attachment}(,\\s*${CssProp.A.attachment})*`,
    background_color: CssProp.C.color,
    background_origin: `${CssProp.A.box}(,\\s*${CssProp.A.box})*`,
    background_repeat: `${CssProp.A.repeat_style}(,\\s*${CssProp.A.repeat_style})*`,
    border: `((${CssProp.C.border_width}|${CssProp.A.border_style}|${CssProp.C.color})\\s*){1,3}`,
    border_radius: `((${CssProp.B.len_or_perc})\\s*){1,4}(\\/\\s*((${CssProp.B.len_or_perc})\\s*){1,4})?`,
    border_spacing: `${CssProp.B.length}\\s*(${CssProp.B.length})?`,
    border_top_color: CssProp.C.color,
    border_top_style: CssProp.A.border_style,
    border_width: `((${CssProp.C.border_width})\\s*){1,4}`,
    color: CssProp.C.color,
    cursor: `(${CssProp.B.url}(\\s*,\\s*)?)*(auto|crosshair|default|pointer|move|e-resize|ne-resize|nw-resize|n-resize|se-resize|sw-resize|s-resize|w-resize|text|wait|help|progress|all-scroll|col-resize|hand|no-drop|not-allowed|row-resize|vertical-text)`,
    display: `inline|block|list-item|run-in|inline-list-item|inline-block|table|inline-table|table-cell|table-caption|flex|inline-flex|grid|inline-grid|${CssProp.A.display_inside}|${CssProp.A.display_outside}|inherit|inline-box|inline-stack`,
    display_outside: CssProp.A.display_outside,
    elevation: `${CssProp.B.angle}|below|level|above|higher|lower`,
    font_family: `(${CssProp.C.family_name}|${CssProp.A.generic_family})(,\\s*(${CssProp.C.family_name}|${CssProp.A.generic_family}))*`,
    height: `${CssProp.B.length}|${CssProp.B.percentage}|auto`,
    letter_spacing: `normal|${CssProp.B.length}`,
    list_style_image: `${CssProp.C.image}|none`,
    margin_right: CssProp.C.margin_width,
    max_height: `${CssProp.B.length_pos}|${CssProp.B.percentage_pos}|none|auto`,
    min_height: `${CssProp.B.length_pos}|${CssProp.B.percentage_pos}|auto`,
    opacity: CssProp.C.alphavalue,
    outline_color: `${CssProp.C.color}|invert`,
    outline_width: CssProp.C.border_width,
    padding: `((${CssProp.C.padding_width})\\s*){1,4}`,
    padding_top: CssProp.C.padding_width,
    pitch_range: CssProp.N.number,
    right: `${CssProp.B.length}|${CssProp.B.percentage}|auto`,
    stress: CssProp.N.number,
    text_indent: `${CssProp.B.length}|${CssProp.B.percentage}`,
    text_shadow: `none|${CssProp.C.shadow}(,\\s*(${CssProp.C.shadow}))*`,
    volume: `${CssProp.N.number_pos}|${CssProp.B.percentage_pos}|silent|x-soft|soft|medium|loud|x-loud`,
    word_wrap: CssProp.AP.overflow_wrap,
    zoom: `normal|${CssProp.N.number_pos}|${CssProp.B.percentage_pos}`,
    backface_visibility: CssProp.AP.visibility,
    background_clip: `${CssProp.A.box}(,\\s*(${CssProp.A.box}))*`,
    background_position: `${CssProp.C.bg_position}(,\\s*(${CssProp.C.bg_position}))*`,
    border_bottom_color: CssProp.C.color,
    border_bottom_style: CssProp.A.border_style,
    border_color: `((${CssProp.C.color})\\s*){1,4}`,
    border_left_color: CssProp.C.color,
    border_right_color: CssProp.C.color,
    border_style: `((${CssProp.A.border_style})\\s*){1,4}`,
    border_top_left_radius: `(${CssProp.B.length}|${CssProp.B.percentage})(\\s*(${CssProp.B.length}|${CssProp.B.percentage}))?`,
    border_top_width: CssProp.C.border_width,
    box_shadow: `none|${CssProp.C.shadow}(,\\s*(${CssProp.C.shadow}))*`,
    clip: `${CssProp.C.shape}|auto`,
    display_inside: CssProp.A.display_inside,
    font_size: `${CssProp.A.absolute_size}|${CssProp.A.relative_size}|${CssProp.B.length_pos}|${CssProp.B.percentage_pos}`,
    line_height: `normal|${CssProp.N.number_pos}|${CssProp.B.length_pos}|${CssProp.B.percentage_pos}`,
    margin_left: CssProp.C.margin_width,
    max_width: `${CssProp.B.length_pos}|${CssProp.B.percentage_pos}|none|auto`,
    outline_style: CssProp.A.border_style,
    padding_bottom: CssProp.C.padding_width,
    padding_right: CssProp.C.padding_width,
    perspective: `none|${CssProp.B.length}`,
    richness: CssProp.N.number,
    text_overflow: `((clip|ellipsis|${CssProp.B.string})\\s*){1,2}`,
    top: `${CssProp.B.length}|${CssProp.B.percentage}|auto`,
    width: `${CssProp.B.length_pos}|${CssProp.B.percentage_pos}|auto`,
    z_index: `auto|${CssProp.B.z_index}`,
    // Simplified background
    background: `(((${CssProp.C.bg_position}\\s*(\\/\\s*${CssProp.C.bg_size})?)|(${CssProp.A.repeat_style})|(${CssProp.A.attachment})|(${CssProp.A.bg_origin})|(${CssProp.C.bg_image})|(${CssProp.C.color}))\\s*)+`,
    background_size: `${CssProp.C.bg_size}(,\\s*${CssProp.C.bg_size})*`,
    border_bottom_left_radius: `(${CssProp.B.length}|${CssProp.B.percentage})(\\s*(${CssProp.B.length}|${CssProp.B.percentage}))?`,
    border_bottom_width: CssProp.C.border_width,
    border_left_style: CssProp.A.border_style,
    border_right_style: CssProp.A.border_style,
    border_top: `((${CssProp.C.border_width}|${CssProp.A.border_style}|${CssProp.C.color})\\s*){1,3}`,
    bottom: `${CssProp.B.len_or_perc}|auto`,
    list_style: `((${CssProp.AP.list_style_type}|${CssProp.AP.list_style_position}|${CssProp.C.image}|none})\\s*){1,3}`,
    margin_top: CssProp.C.margin_width,
    outline: `((${CssProp.C.color}|invert|${CssProp.A.border_style}|${CssProp.C.border_width})\\s*){1,3}`,
    overflow_y: CssProp.AP.overflow_x,
    pitch: `${CssProp.B.frequency}|x-low|low|medium|high|x-high`,
    vertical_align: `baseline|sub|super|top|text-top|middle|bottom|text-bottom|${CssProp.B.len_or_perc}`,
    word_spacing: `normal|${CssProp.B.length}`,
    background_image: `${CssProp.C.bg_image}(,\\s*${CssProp.C.bg_image})*`,
    border_bottom_right_radius: `(${CssProp.B.length}|${CssProp.B.percentage})(\\s*(${CssProp.B.length}|${CssProp.B.percentage}))?`,
    border_left_width: CssProp.C.border_width,
    border_right_width: CssProp.C.border_width,
    left: `${CssProp.B.len_or_perc}|auto`,
    margin_bottom: CssProp.C.margin_width,
    pause_after: `${CssProp.B.time}|${CssProp.B.percentage}`,
    speech_rate: `${CssProp.N.number}|x-slow|slow|medium|fast|x-fast|faster|slower`,
    transition_duration: `${CssProp.B.time}(,\\s*${CssProp.B.time})*`,
    border_bottom: `((${CssProp.C.border_width}|${CssProp.A.border_style}|${CssProp.C.color})\\s*){1,3}`,
    border_right: `((${CssProp.C.border_width}|${CssProp.A.border_style}|${CssProp.C.color})\\s*){1,3}`,
    margin: `((${CssProp.C.margin_width})\\s*){1,4}`,
    padding_left: CssProp.C.padding_width,
    border_left: `((${CssProp.C.border_width}|${CssProp.A.border_style}|${CssProp.C.color})\\s*){1,3}`,
    quotes: `(${CssProp.B.string}\\s*${CssProp.B.string})+|none`,
    border_top_right_radius: `(${CssProp.B.length}|${CssProp.B.percentage})(\\s*(${CssProp.B.length}|${CssProp.B.percentage}))?`,
    min_width: `${CssProp.B.length_pos}|${CssProp.B.percentage_pos}|auto`
  };

  private static readonly _CP1 = {
    font: `(((((${CssProp.AP.font_style}|${CssProp.AP.font_variant}|${CssProp.AP.font_weight})\\s*){1,3})?\\s*(${CssProp._CP.font_size})\\s*(\\/\\s*(${CssProp._CP.line_height}))?\\s+(${CssProp._CP.font_family}))|caption|icon|menu|message-box|small-caption|status-bar)`
  };

  private static readonly CP = { ...CssProp._CP, ...CssProp._CP1 };

  // CSS Property value validation regular expressions for use with sanitize-html

  static BORDER_COLLAPSE = CssProp.reg(CssProp.AP.border_collapse);
  static BOX = CssProp.reg(CssProp.AP.box);
  static BOX_SIZING = CssProp.reg(CssProp.AP.box_sizing);
  static CAPTION_SIDE = CssProp.reg(CssProp.AP.caption_side);
  static CLEAR = CssProp.reg(CssProp.AP.clear);
  static DIRECTION = CssProp.reg(CssProp.AP.direction);
  static EMPTY_CELLS = CssProp.reg(CssProp.AP.empty_cells);
  static FLOAT = CssProp.reg(CssProp.AP.float);
  static FONT_STRETCH = CssProp.reg(CssProp.AP.font_stretch);
  static FONT_STYLE = CssProp.reg(CssProp.AP.font_style);
  static FONT_VARIANT = CssProp.reg(CssProp.AP.font_variant);
  static FONT_WEIGHT = CssProp.reg(CssProp.AP.font_weight);
  static LIST_STYLE_POSITION = CssProp.reg(CssProp.AP.list_style_position);
  static LIST_STYLE_TYPE = CssProp.reg(CssProp.AP.list_style_type);
  static OVERFLOW = CssProp.reg(CssProp.AP.overflow);
  static OVERFLOW_WRAP = CssProp.reg(CssProp.AP.overflow_wrap);
  static OVERFLOW_X = CssProp.reg(CssProp.AP.overflow_x);
  static PAGE_BREAK_AFTER = CssProp.reg(CssProp.AP.page_break_after);
  static PAGE_BREAK_BEFORE = CssProp.reg(CssProp.AP.page_break_before);
  static PAGE_BREAK_INSIDE = CssProp.reg(CssProp.AP.page_break_inside);
  static POSITION = CssProp.reg(CssProp.AP.position);
  static RESIZE = CssProp.reg(CssProp.AP.resize);
  static SPEAK = CssProp.reg(CssProp.AP.speak);
  static SPEAK_HEADER = CssProp.reg(CssProp.AP.speak_header);
  static SPEAK_NUMERAL = CssProp.reg(CssProp.AP.speak_numeral);
  static SPEAK_PUNCTUATION = CssProp.reg(CssProp.AP.speak_punctuation);
  static TABLE_LAYOUT = CssProp.reg(CssProp.AP.table_layout);
  static TEXT_ALIGN = CssProp.reg(CssProp.AP.text_align);
  static TEXT_DECORATION = CssProp.reg(CssProp.AP.text_decoration);
  static TEXT_TRANSFORM = CssProp.reg(CssProp.AP.text_transform);
  static TEXT_WRAP = CssProp.reg(CssProp.AP.text_wrap);
  static UNICODE_BIDI = CssProp.reg(CssProp.AP.unicode_bidi);
  static VISIBILITY = CssProp.reg(CssProp.AP.visibility);
  static WHITE_SPACE = CssProp.reg(CssProp.AP.white_space);
  static WORD_BREAK = CssProp.reg(CssProp.AP.word_break);

  static BACKGROUND_ATTACHMENT = CssProp.reg(CssProp.CP.background_attachment);
  static BACKGROUND_COLOR = CssProp.reg(CssProp.CP.background_color);
  static BACKGROUND_ORIGIN = CssProp.reg(CssProp.CP.background_origin);
  static BACKGROUND_REPEAT = CssProp.reg(CssProp.CP.background_repeat);
  static BORDER = CssProp.reg(CssProp.CP.border);
  static BORDER_RADIUS = CssProp.reg(CssProp.CP.border_radius);
  static BORDER_SPACING = CssProp.reg(CssProp.CP.border_spacing);
  static BORDER_TOP_COLOR = CssProp.reg(CssProp.CP.border_top_color);
  static BORDER_TOP_STYLE = CssProp.reg(CssProp.CP.border_top_style);
  static BORDER_WIDTH = CssProp.reg(CssProp.CP.border_width);
  static COLOR = CssProp.reg(CssProp.CP.color);
  static CURSOR = CssProp.reg(CssProp.CP.cursor);
  static DISPLAY = CssProp.reg(CssProp.CP.display);
  static DISPLAY_OUTSIDE = CssProp.reg(CssProp.CP.display_outside);
  static ELEVATION = CssProp.reg(CssProp.CP.elevation);
  static FONT_FAMILY = CssProp.reg(CssProp.CP.font_family);
  static HEIGHT = CssProp.reg(CssProp.CP.height);
  static LETTER_SPACING = CssProp.reg(CssProp.CP.letter_spacing);
  static LIST_STYLE_IMAGE = CssProp.reg(CssProp.CP.list_style_image);
  static MARGIN_RIGHT = CssProp.reg(CssProp.CP.margin_right);
  static MAX_HEIGHT = CssProp.reg(CssProp.CP.max_height);
  static MIN_HEIGHT = CssProp.reg(CssProp.CP.min_height);
  static OPACITY = CssProp.reg(CssProp.CP.opacity);
  static OUTLINE_COLOR = CssProp.reg(CssProp.CP.outline_color);
  static OUTLINE_WIDTH = CssProp.reg(CssProp.CP.outline_width);
  static PADDING = CssProp.reg(CssProp.CP.padding);
  static PADDING_TOP = CssProp.reg(CssProp.CP.padding_top);
  static PITCH_RANGE = CssProp.reg(CssProp.CP.pitch_range);
  static RIGHT = CssProp.reg(CssProp.CP.right);
  static STRESS = CssProp.reg(CssProp.CP.stress);
  static TEXT_INDENT = CssProp.reg(CssProp.CP.text_indent);
  static TEXT_SHADOW = CssProp.reg(CssProp.CP.text_shadow);
  static VOLUME = CssProp.reg(CssProp.CP.volume);
  static WORD_WRAP = CssProp.reg(CssProp.CP.word_wrap);
  static ZOOM = CssProp.reg(CssProp.CP.zoom);
  static BACKFACE_VISIBILITY = CssProp.reg(CssProp.CP.backface_visibility);
  static BACKGROUND_CLIP = CssProp.reg(CssProp.CP.background_clip);
  static BACKGROUND_POSITION = CssProp.reg(CssProp.CP.background_position);
  static BORDER_BOTTOM_COLOR = CssProp.reg(CssProp.CP.border_bottom_color);
  static BORDER_BOTTOM_STYLE = CssProp.reg(CssProp.CP.border_bottom_style);
  static BORDER_COLOR = CssProp.reg(CssProp.CP.border_color);
  static BORDER_LEFT_COLOR = CssProp.reg(CssProp.CP.border_left_color);
  static BORDER_RIGHT_COLOR = CssProp.reg(CssProp.CP.border_right_color);
  static BORDER_STYLE = CssProp.reg(CssProp.CP.border_style);
  static BORDER_TOP_LEFT_RADIUS = CssProp.reg(
    CssProp.CP.border_top_left_radius
  );
  static BORDER_TOP_WIDTH = CssProp.reg(CssProp.CP.border_top_width);
  static BOX_SHADOW = CssProp.reg(CssProp.CP.box_shadow);
  static CLIP = CssProp.reg(CssProp.CP.clip);
  static DISPLAY_INSIDE = CssProp.reg(CssProp.CP.display_inside);
  static FONT_SIZE = CssProp.reg(CssProp.CP.font_size);
  static LINE_HEIGHT = CssProp.reg(CssProp.CP.line_height);
  static MARGIN_LEFT = CssProp.reg(CssProp.CP.margin_left);
  static MAX_WIDTH = CssProp.reg(CssProp.CP.max_width);
  static OUTLINE_STYLE = CssProp.reg(CssProp.CP.outline_style);
  static PADDING_BOTTOM = CssProp.reg(CssProp.CP.padding_bottom);
  static PADDING_RIGHT = CssProp.reg(CssProp.CP.padding_right);
  static PERSPECTIVE = CssProp.reg(CssProp.CP.perspective);
  static RICHNESS = CssProp.reg(CssProp.CP.richness);
  static TEXT_OVERFLOW = CssProp.reg(CssProp.CP.text_overflow);
  static TOP = CssProp.reg(CssProp.CP.top);
  static WIDTH = CssProp.reg(CssProp.CP.width);
  static Z_INDEX = CssProp.reg(CssProp.CP.z_index);
  static BACKGROUND = CssProp.reg(CssProp.CP.background);
  static BACKGROUND_SIZE = CssProp.reg(CssProp.CP.background_size);
  static BORDER_BOTTOM_LEFT_RADIUS = CssProp.reg(
    CssProp.CP.border_bottom_left_radius
  );
  static BORDER_BOTTOM_WIDTH = CssProp.reg(CssProp.CP.border_bottom_width);
  static BORDER_LEFT_STYLE = CssProp.reg(CssProp.CP.border_left_style);
  static BORDER_RIGHT_STYLE = CssProp.reg(CssProp.CP.border_right_style);
  static BORDER_TOP = CssProp.reg(CssProp.CP.border_top);
  static BOTTOM = CssProp.reg(CssProp.CP.bottom);
  static LIST_STYLE = CssProp.reg(CssProp.CP.list_style);
  static MARGIN_TOP = CssProp.reg(CssProp.CP.margin_top);
  static OUTLINE = CssProp.reg(CssProp.CP.outline);
  static OVERFLOW_Y = CssProp.reg(CssProp.CP.overflow_y);
  static PITCH = CssProp.reg(CssProp.CP.pitch);
  static VERTICAL_ALIGN = CssProp.reg(CssProp.CP.vertical_align);
  static WORD_SPACING = CssProp.reg(CssProp.CP.word_spacing);
  static BACKGROUND_IMAGE = CssProp.reg(CssProp.CP.background_image);
  static BORDER_BOTTOM_RIGHT_RADIUS = CssProp.reg(
    CssProp.CP.border_bottom_right_radius
  );
  static BORDER_LEFT_WIDTH = CssProp.reg(CssProp.CP.border_left_width);
  static BORDER_RIGHT_WIDTH = CssProp.reg(CssProp.CP.border_right_width);
  static LEFT = CssProp.reg(CssProp.CP.left);
  static MARGIN_BOTTOM = CssProp.reg(CssProp.CP.margin_bottom);
  static PAUSE_AFTER = CssProp.reg(CssProp.CP.pause_after);
  static SPEECH_RATE = CssProp.reg(CssProp.CP.speech_rate);
  static TRANSITION_DURATION = CssProp.reg(CssProp.CP.transition_duration);
  static BORDER_BOTTOM = CssProp.reg(CssProp.CP.border_bottom);
  static BORDER_RIGHT = CssProp.reg(CssProp.CP.border_right);
  static MARGIN = CssProp.reg(CssProp.CP.margin);
  static PADDING_LEFT = CssProp.reg(CssProp.CP.padding_left);
  static BORDER_LEFT = CssProp.reg(CssProp.CP.border_left);
  static FONT = CssProp.reg(CssProp.CP.font);
  static QUOTES = CssProp.reg(CssProp.CP.quotes);
  static BORDER_TOP_RIGHT_RADIUS = CssProp.reg(
    CssProp.CP.border_top_right_radius
  );
  static MIN_WIDTH = CssProp.reg(CssProp.CP.min_width);
}

/**
 * A class to sanitize HTML strings.
 */
export class Sanitizer implements IRenderMime.ISanitizer {
  constructor() {
    this._options = this._generateOptions();
  }
  /**
   * Sanitize an HTML string.
   *
   * @param dirty - The dirty text.
   *
   * @param options - The optional sanitization options.
   *
   * @returns The sanitized string.
   */
  sanitize(dirty: string, options?: IRenderMime.ISanitizerOptions): string {
    return sanitize(dirty, { ...this._options, ...(options || {}) });
  }

  /**
   * @returns Whether to replace URLs by HTML anchors.
   */
  getAutolink(): boolean {
    return this._autolink;
  }

  /**
   * Set the allowed schemes
   *
   * @param scheme Allowed schemes
   */
  setAllowedSchemes(scheme: Array<string>): void {
    // Force copy of `scheme`
    this._options.allowedSchemes = [...scheme];
  }

  /**
   * Set the URL replacement boolean.
   *
   * @param autolink URL replacement boolean.
   */
  setAutolink(autolink: boolean): void {
    this._autolink = autolink;
  }

  /**
   * Set the whether to allow `name` and `id` attributes.
   */
  setAllowNamedProperties(allowNamedProperties: boolean): void {
    this._allowNamedProperties = allowNamedProperties;
    this._options = this._generateOptions();
  }

  private _autolink: boolean = true;
  private _allowNamedProperties: boolean = false;
  private _options: sanitize.IOptions;
  private _generateOptions = (): sanitize.IOptions => ({
    // HTML tags that are allowed to be used. Tags were extracted from Google Caja
    allowedTags: [
      'a',
      'abbr',
      'acronym',
      'address',
      'area',
      'article',
      'aside',
      'audio',
      'b',
      'bdi',
      'bdo',
      'big',
      'blockquote',
      'br',
      'button',
      'canvas',
      'caption',
      'center',
      'cite',
      'code',
      'col',
      'colgroup',
      'colspan',
      'command',
      'data',
      'datalist',
      'dd',
      'del',
      'details',
      'dfn',
      'dir',
      'div',
      'dl',
      'dt',
      'em',
      'fieldset',
      'figcaption',
      'figure',
      'font',
      'footer',
      'form',
      'h1',
      'h2',
      'h3',
      'h4',
      'h5',
      'h6',
      'header',
      'hgroup',
      'hr',
      'i',
      // 'iframe' is allowed by Google Caja, but disallowed by default by sanitize-html
      // , 'iframe'
      'img',
      'input',
      'ins',
      'kbd',
      'label',
      'legend',
      'li',
      'map',
      'mark',
      'menu',
      'meter',
      'nav',
      'nobr',
      'ol',
      'optgroup',
      'option',
      'output',
      'p',
      'pre',
      'progress',
      'q',
      'rowspan',
      's',
      'samp',
      'section',
      'select',
      'small',
      'source',
      'span',
      'strike',
      'strong',
      'sub',
      'summary',
      'sup',
      'table',
      'tbody',
      'td',
      'textarea',
      'tfoot',
      'th',
      'thead',
      'time',
      'tr',
      'track',
      'tt',
      'u',
      'ul',
      'var',
      'video',
      'wbr'
    ],
    // Attributes that HTML tags are allowed to have, extracted from Google Caja.
    // See https://github.com/jupyterlab/jupyterlab/issues/1812#issuecomment-285848435
    allowedAttributes: {
      '*': [
        'class',
        'dir',
        'draggable',
        'hidden',
        ...(this._allowNamedProperties ? ['id'] : []),
        'inert',
        'itemprop',
        'itemref',
        'itemscope',
        'lang',
        'spellcheck',
        'style',
        'title',
        'translate'
      ],
      // 'rel' and 'target' were *not* allowed by Google Caja
      a: [
        'accesskey',
        'coords',
        'href',
        'hreflang',
        ...(this._allowNamedProperties ? ['name'] : []),
        'rel',
        'shape',
        'tabindex',
        'target',
        'type'
      ],
      area: [
        'accesskey',
        'alt',
        'coords',
        'href',
        'nohref',
        'shape',
        'tabindex'
      ],
      // 'autoplay' was *not* allowed by Google Caja
      audio: [
        'autoplay',
        'controls',
        'loop',
        'mediagroup',
        'muted',
        'preload',
        'src'
      ],
      bdo: ['dir'],
      blockquote: ['cite'],
      br: ['clear'],
      button: [
        'accesskey',
        'data-commandlinker-args',
        'data-commandlinker-command',
        'disabled',
        ...(this._allowNamedProperties ? ['name'] : []),
        'tabindex',
        'type',
        'value'
      ],
      canvas: ['height', 'width'],
      caption: ['align'],
      col: ['align', 'char', 'charoff', 'span', 'valign', 'width'],
      colgroup: ['align', 'char', 'charoff', 'span', 'valign', 'width'],
      command: [
        'checked',
        'command',
        'disabled',
        'icon',
        'label',
        'radiogroup',
        'type'
      ],
      data: ['value'],
      del: ['cite', 'datetime'],
      details: ['open'],
      dir: ['compact'],
      div: ['align'],
      dl: ['compact'],
      fieldset: ['disabled'],
      font: ['color', 'face', 'size'],
      form: [
        'accept',
        'autocomplete',
        'enctype',
        'method',
        ...(this._allowNamedProperties ? ['name'] : []),
        'novalidate'
      ],
      h1: ['align'],
      h2: ['align'],
      h3: ['align'],
      h4: ['align'],
      h5: ['align'],
      h6: ['align'],
      hr: ['align', 'noshade', 'size', 'width'],
      iframe: [
        'align',
        'frameborder',
        'height',
        'marginheight',
        'marginwidth',
        'width'
      ],
      img: [
        'align',
        'alt',
        'border',
        'height',
        'hspace',
        'ismap',
        ...(this._allowNamedProperties ? ['name'] : []),
        'src',
        'usemap',
        'vspace',
        'width'
      ],
      input: [
        'accept',
        'accesskey',
        'align',
        'alt',
        'autocomplete',
        'checked',
        'disabled',
        'inputmode',
        'ismap',
        'list',
        'max',
        'maxlength',
        'min',
        'multiple',
        ...(this._allowNamedProperties ? ['name'] : []),
        'placeholder',
        'readonly',
        'required',
        'size',
        'src',
        'step',
        'tabindex',
        'type',
        'usemap',
        'value'
      ],
      ins: ['cite', 'datetime'],
      label: ['accesskey', 'for'],
      legend: ['accesskey', 'align'],
      li: ['type', 'value'],
      map: this._allowNamedProperties ? ['name'] : [],
      menu: ['compact', 'label', 'type'],
      meter: ['high', 'low', 'max', 'min', 'value'],
      ol: ['compact', 'reversed', 'start', 'type'],
      optgroup: ['disabled', 'label'],
      option: ['disabled', 'label', 'selected', 'value'],
      output: ['for', ...(this._allowNamedProperties ? ['name'] : [])],
      p: ['align'],
      pre: ['width'],
      progress: ['max', 'min', 'value'],
      q: ['cite'],
      select: [
        'autocomplete',
        'disabled',
        'multiple',
        ...(this._allowNamedProperties ? ['name'] : []),
        'required',
        'size',
        'tabindex'
      ],
      source: ['type'],
      table: [
        'align',
        'bgcolor',
        'border',
        'cellpadding',
        'cellspacing',
        'frame',
        'rules',
        'summary',
        'width'
      ],
      tbody: ['align', 'char', 'charoff', 'valign'],
      td: [
        'abbr',
        'align',
        'axis',
        'bgcolor',
        'char',
        'charoff',
        'colspan',
        'headers',
        'height',
        'nowrap',
        'rowspan',
        'scope',
        'valign',
        'width'
      ],
      textarea: [
        'accesskey',
        'autocomplete',
        'cols',
        'disabled',
        'inputmode',
        ...(this._allowNamedProperties ? ['name'] : []),
        'placeholder',
        'readonly',
        'required',
        'rows',
        'tabindex',
        'wrap'
      ],
      tfoot: ['align', 'char', 'charoff', 'valign'],
      th: [
        'abbr',
        'align',
        'axis',
        'bgcolor',
        'char',
        'charoff',
        'colspan',
        'headers',
        'height',
        'nowrap',
        'rowspan',
        'scope',
        'valign',
        'width'
      ],
      thead: ['align', 'char', 'charoff', 'valign'],
      tr: ['align', 'bgcolor', 'char', 'charoff', 'valign'],
      track: ['default', 'kind', 'label', 'srclang'],
      ul: ['compact', 'type'],
      video: [
        'autoplay',
        'controls',
        'height',
        'loop',
        'mediagroup',
        'muted',
        'poster',
        'preload',
        'src',
        'width'
      ]
    },
    // Inline CSS styles that HTML tags may have (and their allowed values)
    allowedStyles: {
      // To simplify the data, all styles are allowed on all tags that allow the style attribute
      '*': {
        'backface-visibility': [CssProp.BACKFACE_VISIBILITY],
        background: [CssProp.BACKGROUND],
        'background-attachment': [CssProp.BACKGROUND_ATTACHMENT],
        'background-clip': [CssProp.BACKGROUND_CLIP],
        'background-color': [CssProp.BACKGROUND_COLOR],
        'background-image': [CssProp.BACKGROUND_IMAGE],
        'background-origin': [CssProp.BACKGROUND_ORIGIN],
        'background-position': [CssProp.BACKGROUND_POSITION],
        'background-repeat': [CssProp.BACKGROUND_REPEAT],
        'background-size': [CssProp.BACKGROUND_SIZE],
        border: [CssProp.BORDER],
        'border-bottom': [CssProp.BORDER_BOTTOM],
        'border-bottom-color': [CssProp.BORDER_BOTTOM_COLOR],
        'border-bottom-left-radius': [CssProp.BORDER_BOTTOM_LEFT_RADIUS],
        'border-bottom-right-radius': [CssProp.BORDER_BOTTOM_RIGHT_RADIUS],
        'border-bottom-style': [CssProp.BORDER_BOTTOM_STYLE],
        'border-bottom-width': [CssProp.BORDER_BOTTOM_WIDTH],
        'border-collapse': [CssProp.BORDER_COLLAPSE],
        'border-color': [CssProp.BORDER_COLOR],
        'border-left': [CssProp.BORDER_LEFT],
        'border-left-color': [CssProp.BORDER_LEFT_COLOR],
        'border-left-style': [CssProp.BORDER_LEFT_STYLE],
        'border-left-width': [CssProp.BORDER_LEFT_WIDTH],
        'border-radius': [CssProp.BORDER_RADIUS],
        'border-right': [CssProp.BORDER_RIGHT],
        'border-right-color': [CssProp.BORDER_RIGHT_COLOR],
        'border-right-style': [CssProp.BORDER_RIGHT_STYLE],
        'border-right-width': [CssProp.BORDER_RIGHT_WIDTH],
        'border-spacing': [CssProp.BORDER_SPACING],
        'border-style': [CssProp.BORDER_STYLE],
        'border-top': [CssProp.BORDER_TOP],
        'border-top-color': [CssProp.BORDER_TOP_COLOR],
        'border-top-left-radius': [CssProp.BORDER_TOP_LEFT_RADIUS],
        'border-top-right-radius': [CssProp.BORDER_TOP_RIGHT_RADIUS],
        'border-top-style': [CssProp.BORDER_TOP_STYLE],
        'border-top-width': [CssProp.BORDER_TOP_WIDTH],
        'border-width': [CssProp.BORDER_WIDTH],
        bottom: [CssProp.BOTTOM],
        box: [CssProp.BOX],
        'box-shadow': [CssProp.BOX_SHADOW],
        'box-sizing': [CssProp.BOX_SIZING],
        'caption-side': [CssProp.CAPTION_SIDE],
        clear: [CssProp.CLEAR],
        clip: [CssProp.CLIP],
        color: [CssProp.COLOR],
        cursor: [CssProp.CURSOR],
        direction: [CssProp.DIRECTION],
        display: [CssProp.DISPLAY],
        'display-inside': [CssProp.DISPLAY_INSIDE],
        'display-outside': [CssProp.DISPLAY_OUTSIDE],
        elevation: [CssProp.ELEVATION],
        'empty-cells': [CssProp.EMPTY_CELLS],
        float: [CssProp.FLOAT],
        font: [CssProp.FONT],
        'font-family': [CssProp.FONT_FAMILY],
        'font-size': [CssProp.FONT_SIZE],
        'font-stretch': [CssProp.FONT_STRETCH],
        'font-style': [CssProp.FONT_STYLE],
        'font-variant': [CssProp.FONT_VARIANT],
        'font-weight': [CssProp.FONT_WEIGHT],
        height: [CssProp.HEIGHT],
        left: [CssProp.LEFT],
        'letter-spacing': [CssProp.LETTER_SPACING],
        'line-height': [CssProp.LINE_HEIGHT],
        'list-style': [CssProp.LIST_STYLE],
        'list-style-image': [CssProp.LIST_STYLE_IMAGE],
        'list-style-position': [CssProp.LIST_STYLE_POSITION],
        'list-style-type': [CssProp.LIST_STYLE_TYPE],
        margin: [CssProp.MARGIN],
        'margin-bottom': [CssProp.MARGIN_BOTTOM],
        'margin-left': [CssProp.MARGIN_LEFT],
        'margin-right': [CssProp.MARGIN_RIGHT],
        'margin-top': [CssProp.MARGIN_TOP],
        'max-height': [CssProp.MAX_HEIGHT],
        'max-width': [CssProp.MAX_WIDTH],
        'min-height': [CssProp.MIN_HEIGHT],
        'min-width': [CssProp.MIN_WIDTH],
        opacity: [CssProp.OPACITY],
        outline: [CssProp.OUTLINE],
        'outline-color': [CssProp.OUTLINE_COLOR],
        'outline-style': [CssProp.OUTLINE_STYLE],
        'outline-width': [CssProp.OUTLINE_WIDTH],
        overflow: [CssProp.OVERFLOW],
        'overflow-wrap': [CssProp.OVERFLOW_WRAP],
        'overflow-x': [CssProp.OVERFLOW_X],
        'overflow-y': [CssProp.OVERFLOW_Y],
        padding: [CssProp.PADDING],
        'padding-bottom': [CssProp.PADDING_BOTTOM],
        'padding-left': [CssProp.PADDING_LEFT],
        'padding-right': [CssProp.PADDING_RIGHT],
        'padding-top': [CssProp.PADDING_TOP],
        'page-break-after': [CssProp.PAGE_BREAK_AFTER],
        'page-break-before': [CssProp.PAGE_BREAK_BEFORE],
        'page-break-inside': [CssProp.PAGE_BREAK_INSIDE],
        'pause-after': [CssProp.PAUSE_AFTER],
        perspective: [CssProp.PERSPECTIVE],
        pitch: [CssProp.PITCH],
        'pitch-range': [CssProp.PITCH_RANGE],
        position: [CssProp.POSITION],
        quotes: [CssProp.QUOTES],
        resize: [CssProp.RESIZE],
        richness: [CssProp.RICHNESS],
        right: [CssProp.RIGHT],
        speak: [CssProp.SPEAK],
        'speak-header': [CssProp.SPEAK_HEADER],
        'speak-numeral': [CssProp.SPEAK_NUMERAL],
        'speak-punctuation': [CssProp.SPEAK_PUNCTUATION],
        'speech-rate': [CssProp.SPEECH_RATE],
        stress: [CssProp.STRESS],
        'table-layout': [CssProp.TABLE_LAYOUT],
        'text-align': [CssProp.TEXT_ALIGN],
        'text-decoration': [CssProp.TEXT_DECORATION],
        'text-indent': [CssProp.TEXT_INDENT],
        'text-overflow': [CssProp.TEXT_OVERFLOW],
        'text-shadow': [CssProp.TEXT_SHADOW],
        'text-transform': [CssProp.TEXT_TRANSFORM],
        'text-wrap': [CssProp.TEXT_WRAP],
        top: [CssProp.TOP],
        'unicode-bidi': [CssProp.UNICODE_BIDI],
        'vertical-align': [CssProp.VERTICAL_ALIGN],
        visibility: [CssProp.VISIBILITY],
        volume: [CssProp.VOLUME],
        'white-space': [CssProp.WHITE_SPACE],
        width: [CssProp.WIDTH],
        'word-break': [CssProp.WORD_BREAK],
        'word-spacing': [CssProp.WORD_SPACING],
        'word-wrap': [CssProp.WORD_WRAP],
        'z-index': [CssProp.Z_INDEX],
        zoom: [CssProp.ZOOM]
      }
    },
    transformTags: {
      // Set the "rel" attribute for <a> tags to "nofollow".
      a: sanitize.simpleTransform('a', { rel: 'nofollow' }),
      // Set the "disabled" attribute for <input> tags.
      input: sanitize.simpleTransform('input', { disabled: 'disabled' })
    },
    allowedSchemes: [...sanitize.defaults.allowedSchemes],
    allowedSchemesByTag: {
      // Allow 'attachment:' img src (used for markdown cell attachments).
      img: sanitize.defaults.allowedSchemes.concat(['attachment'])
    },
    // Override of the default option, so we can skip 'src' attribute validation.
    // 'src' Attributes are validated to be URIs, which does not allow for embedded (image) data.
    // Since embedded data is no longer deemed to be a threat, validation can be skipped.
    // See https://github.com/jupyterlab/jupyterlab/issues/5183
    allowedSchemesAppliedToAttributes: ['href', 'cite']
  });
}