import {DOMSerializer, Fragment, Mark, Node, TagParseRule} from "prosemirror-model"
import {TextSelection} from "prosemirror-state"

import {domIndex, isEquivalentPosition, DOMNode} from "./dom"
import * as browser from "./browser"
import {Decoration, DecorationSource, WidgetConstructor, WidgetType, NodeType} from "./decoration"
import {EditorView} from "./index"

declare global {
  interface Node { 
    /// @internal
    pmViewDesc?: ViewDesc 
  }
}

/// A ViewMutationRecord represents a DOM
/// [mutation](https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver)
/// or a selection change happens within the view. When the change is
/// a selection change, the record will have a `type` property of
/// `"selection"` (which doesn't occur for native mutation records).
export type ViewMutationRecord = MutationRecord | { type: "selection", target: DOMNode }

/// By default, document nodes are rendered using the result of the
/// [`toDOM`](#model.NodeSpec.toDOM) method of their spec, and managed
/// entirely by the editor. For some use cases, such as embedded
/// node-specific editing interfaces, you want more control over
/// the behavior of a node's in-editor representation, and need to
/// [define](#view.EditorProps.nodeViews) a custom node view.
///
/// Objects returned as node views must conform to this interface.
export interface NodeView {
  /// The outer DOM node that represents the document node.
  dom: DOMNode

  /// The DOM node that should hold the node's content. Only meaningful
  /// if the node view also defines a `dom` property and if its node
  /// type is not a leaf node type. When this is present, ProseMirror
  /// will take care of rendering the node's children into it. When it
  /// is not present, the node view itself is responsible for rendering
  /// (or deciding not to render) its child nodes.
  contentDOM?: HTMLElement | null

  /// When given, this will be called when the view is updating
  /// itself. It will be given a node, an array of active decorations
  /// around the node (which are automatically drawn, and the node
  /// view may ignore if it isn't interested in them), and a
  /// [decoration source](#view.DecorationSource) that represents any
  /// decorations that apply to the content of the node (which again
  /// may be ignored). It should return true if it was able to update
  /// to that node, and false otherwise. If the node view has a
  /// `contentDOM` property (or no `dom` property), updating its child
  /// nodes will be handled by ProseMirror.
  update?: (node: Node, decorations: readonly Decoration[], innerDecorations: DecorationSource) => boolean

  /// By default, `update` will only be called when a node of the same
  /// node type appears in this view's position. When you set this to
  /// true, it will be called for any node, making it possible to have
  /// a node view that representsmultiple types of nodes. You will
  /// need to check the type of the nodes you get in `update` and
  /// return `false` for types you cannot handle.
  multiType?: boolean

  /// Can be used to override the way the node's selected status (as a
  /// node selection) is displayed.
  selectNode?: () => void

  /// When defining a `selectNode` method, you should also provide a
  /// `deselectNode` method to remove the effect again.
  deselectNode?: () => void

  /// This will be called to handle setting the selection inside the
  /// node. The `anchor` and `head` positions are relative to the start
  /// of the node. By default, a DOM selection will be created between
  /// the DOM positions corresponding to those positions, but if you
  /// override it you can do something else.
  setSelection?: (anchor: number, head: number, root: Document | ShadowRoot) => void

  /// Can be used to prevent the editor view from trying to handle some
  /// or all DOM events that bubble up from the node view. Events for
  /// which this returns true are not handled by the editor.
  stopEvent?: (event: Event) => boolean

  /// Called when a [mutation](#view.ViewMutationRecord) happens within the
  /// view. Return false if the editor should re-read the selection or re-parse
  /// the range around the mutation, true if it can safely be ignored.
  ignoreMutation?: (mutation: ViewMutationRecord) => boolean

  /// Called when the node view is removed from the editor or the whole
  /// editor is destroyed.
  destroy?: () => void
}

/// By default, document marks are rendered using the result of the
/// [`toDOM`](#model.MarkSpec.toDOM) method of their spec, and managed entirely
/// by the editor. For some use cases, you want more control over the behavior
/// of a mark's in-editor representation, and need to
/// [define](#view.EditorProps.markViews) a custom mark view.
///
/// Objects returned as mark views must conform to this interface.
export interface MarkView {
  /// The outer DOM node that represents the document node.
  dom: DOMNode

  /// The DOM node that should hold the mark's content. When this is not
  /// present, the `dom` property is used as the content DOM.
  contentDOM?: HTMLElement | null

  /// Called when a [mutation](#view.ViewMutationRecord) happens within the
  /// view. Return false if the editor should re-read the selection or re-parse
  /// the range around the mutation, true if it can safely be ignored.
  ignoreMutation?: (mutation: ViewMutationRecord) => boolean

  
  /// Called when the mark view is removed from the editor or the whole
  /// editor is destroyed.
  destroy?: () => void
}

// View descriptions are data structures that describe the DOM that is
// used to represent the editor's content. They are used for:
//
// - Incremental redrawing when the document changes
//
// - Figuring out what part of the document a given DOM position
//   corresponds to
//
// - Wiring in custom implementations of the editing interface for a
//   given node
//
// They form a doubly-linked mutable tree, starting at `view.docView`.

const NOT_DIRTY = 0, CHILD_DIRTY = 1, CONTENT_DIRTY = 2, NODE_DIRTY = 3

// Superclass for the various kinds of descriptions. Defines their
// basic structure and shared methods.
export class ViewDesc {
  dirty = NOT_DIRTY
  declare node: Node | null

  constructor(
    public parent: ViewDesc | undefined,
    public children: ViewDesc[],
    public dom: DOMNode,
    // This is the node that holds the child views. It may be null for
    // descs that don't have children.
    public contentDOM: HTMLElement | null
  ) {
    // An expando property on the DOM node provides a link back to its
    // description.
    dom.pmViewDesc = this
  }

  // Used to check whether a given description corresponds to a
  // widget/mark/node.
  matchesWidget(widget: Decoration) { return false }
  matchesMark(mark: Mark) { return false }
  matchesNode(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource) { return false }
  matchesHack(nodeName: string) { return false }

  // When parsing in-editor content (in domchange.js), we allow
  // descriptions to determine the parse rules that should be used to
  // parse them.
  parseRule(): Omit<TagParseRule, "tag"> | null { return null }

  // Used by the editor's event handler to ignore events that come
  // from certain descs.
  stopEvent(event: Event) { return false }

  // The size of the content represented by this desc.
  get size() {
    let size = 0
    for (let i = 0; i < this.children.length; i++) size += this.children[i].size
    return size
  }

  // For block nodes, this represents the space taken up by their
  // start/end tokens.
  get border() { return 0 }

  destroy() {
    this.parent = undefined
    if (this.dom.pmViewDesc == this) this.dom.pmViewDesc = undefined
    for (let i = 0; i < this.children.length; i++)
      this.children[i].destroy()
  }

  posBeforeChild(child: ViewDesc): number {
    for (let i = 0, pos = this.posAtStart;; i++) {
      let cur = this.children[i]
      if (cur == child) return pos
      pos += cur.size
    }
  }

  get posBefore() {
    return this.parent!.posBeforeChild(this)
  }

  get posAtStart() {
    return this.parent ? this.parent.posBeforeChild(this) + this.border : 0
  }

  get posAfter() {
    return this.posBefore + this.size
  }

  get posAtEnd() {
    return this.posAtStart + this.size - 2 * this.border
  }

  localPosFromDOM(dom: DOMNode, offset: number, bias: number): number {
    // If the DOM position is in the content, use the child desc after
    // it to figure out a position.
    if (this.contentDOM && this.contentDOM.contains(dom.nodeType == 1 ? dom : dom.parentNode)) {
      if (bias < 0) {
        let domBefore, desc: ViewDesc | undefined
        if (dom == this.contentDOM) {
          domBefore = dom.childNodes[offset - 1]
        } else {
          while (dom.parentNode != this.contentDOM) dom = dom.parentNode!
          domBefore = dom.previousSibling
        }
        while (domBefore && !((desc = domBefore.pmViewDesc) && desc.parent == this)) domBefore = domBefore.previousSibling
        return domBefore ? this.posBeforeChild(desc!) + desc!.size : this.posAtStart
      } else {
        let domAfter, desc: ViewDesc | undefined
        if (dom == this.contentDOM) {
          domAfter = dom.childNodes[offset]
        } else {
          while (dom.parentNode != this.contentDOM) dom = dom.parentNode!
          domAfter = dom.nextSibling
        }
        while (domAfter && !((desc = domAfter.pmViewDesc) && desc.parent == this)) domAfter = domAfter.nextSibling
        return domAfter ? this.posBeforeChild(desc!) : this.posAtEnd
      }
    }
    // Otherwise, use various heuristics, falling back on the bias
    // parameter, to determine whether to return the position at the
    // start or at the end of this view desc.
    let atEnd
    if (dom == this.dom && this.contentDOM) {
      atEnd = offset > domIndex(this.contentDOM)
    } else if (this.contentDOM && this.contentDOM != this.dom && this.dom.contains(this.contentDOM)) {
      atEnd = dom.compareDocumentPosition(this.contentDOM) & 2
    } else if (this.dom.firstChild) {
      if (offset == 0) for (let search = dom;; search = search.parentNode!) {
        if (search == this.dom) { atEnd = false; break }
        if (search.previousSibling) break
      }
      if (atEnd == null && offset == dom.childNodes.length) for (let search = dom;; search = search.parentNode!) {
        if (search == this.dom) { atEnd = true; break }
        if (search.nextSibling) break
      }
    }
    return (atEnd == null ? bias > 0 : atEnd) ? this.posAtEnd : this.posAtStart
  }

  // Scan up the dom finding the first desc that is a descendant of
  // this one.
  nearestDesc(dom: DOMNode): ViewDesc | undefined
  nearestDesc(dom: DOMNode, onlyNodes: true): NodeViewDesc | undefined
  nearestDesc(dom: DOMNode, onlyNodes: boolean = false) {
    for (let first = true, cur: DOMNode | null = dom; cur; cur = cur.parentNode) {
      let desc = this.getDesc(cur), nodeDOM
      if (desc && (!onlyNodes || desc.node)) {
        // If dom is outside of this desc's nodeDOM, don't count it.
        if (first && (nodeDOM = (desc as NodeViewDesc).nodeDOM) &&
            !(nodeDOM.nodeType == 1 ? nodeDOM.contains(dom.nodeType == 1 ? dom : dom.parentNode) : nodeDOM == dom))
          first = false
        else
          return desc
      }
    }
  }

  getDesc(dom: DOMNode) {
    let desc = dom.pmViewDesc
    for (let cur: ViewDesc | undefined = desc; cur; cur = cur.parent) if (cur == this) return desc
  }

  posFromDOM(dom: DOMNode, offset: number, bias: number) {
    for (let scan: DOMNode | null = dom; scan; scan = scan.parentNode) {
      let desc = this.getDesc(scan)
      if (desc) return desc.localPosFromDOM(dom, offset, bias)
    }
    return -1
  }

  // Find the desc for the node after the given pos, if any. (When a
  // parent node overrode rendering, there might not be one.)
  descAt(pos: number): ViewDesc | undefined {
    for (let i = 0, offset = 0; i < this.children.length; i++) {
      let child = this.children[i], end = offset + child.size
      if (offset == pos && end != offset) {
        while (!child.border && child.children.length) {
          for (let i = 0; i < child.children.length; i++) {
            let inner = child.children[i]
            if (inner.size) { child = inner; break }
          }
        }
        return child
      }
      if (pos < end) return child.descAt(pos - offset - child.border)
      offset = end
    }
  }

  domFromPos(pos: number, side: number): {node: DOMNode, offset: number, atom?: number} {
    if (!this.contentDOM) return {node: this.dom, offset: 0, atom: pos + 1}
    // First find the position in the child array
    let i = 0, offset = 0
    for (let curPos = 0; i < this.children.length; i++) {
      let child = this.children[i], end = curPos + child.size
      if (end > pos || child instanceof TrailingHackViewDesc) { offset = pos - curPos; break }
      curPos = end
    }
    // If this points into the middle of a child, call through
    if (offset) return this.children[i].domFromPos(offset - this.children[i].border, side)
    // Go back if there were any zero-length widgets with side >= 0 before this point
    for (let prev; i && !(prev = this.children[i - 1]).size && prev instanceof WidgetViewDesc && prev.side >= 0; i--) {}
    // Scan towards the first useable node
    if (side <= 0) {
      let prev, enter = true
      for (;; i--, enter = false) {
        prev = i ? this.children[i - 1] : null
        if (!prev || prev.dom.parentNode == this.contentDOM) break
      }
      if (prev && side && enter && !prev.border && !prev.domAtom) return prev.domFromPos(prev.size, side)
      return {node: this.contentDOM, offset: prev ? domIndex(prev.dom) + 1 : 0}
    } else {
      let next, enter = true
      for (;; i++, enter = false) {
        next = i < this.children.length ? this.children[i] : null
        if (!next || next.dom.parentNode == this.contentDOM) break
      }
      if (next && enter && !next.border && !next.domAtom) return next.domFromPos(0, side)
      return {node: this.contentDOM, offset: next ? domIndex(next.dom) : this.contentDOM.childNodes.length}
    }
  }

  // Used to find a DOM range in a single parent for a given changed
  // range.
  parseRange(
    from: number, to: number, base = 0
  ): {node: DOMNode, from: number, to: number, fromOffset: number, toOffset: number} {
    if (this.children.length == 0)
      return {node: this.contentDOM!, from, to, fromOffset: 0, toOffset: this.contentDOM!.childNodes.length}

    let fromOffset = -1, toOffset = -1
    for (let offset = base, i = 0;; i++) {
      let child = this.children[i], end = offset + child.size
      if (fromOffset == -1 && from <= end) {
        let childBase = offset + child.border
        // FIXME maybe descend mark views to parse a narrower range?
        if (from >= childBase && to <= end - child.border && child.node &&
            child.contentDOM && this.contentDOM!.contains(child.contentDOM))
          return child.parseRange(from, to, childBase)

        from = offset
        for (let j = i; j > 0; j--) {
          let prev = this.children[j - 1]
          if (prev.size && prev.dom.parentNode == this.contentDOM && !prev.emptyChildAt(1)) {
            fromOffset = domIndex(prev.dom) + 1
            break
          }
          from -= prev.size
        }
        if (fromOffset == -1) fromOffset = 0
      }
      if (fromOffset > -1 && (end > to || i == this.children.length - 1)) {
        to = end
        for (let j = i + 1; j < this.children.length; j++) {
          let next = this.children[j]
          if (next.size && next.dom.parentNode == this.contentDOM && !next.emptyChildAt(-1)) {
            toOffset = domIndex(next.dom)
            break
          }
          to += next.size
        }
        if (toOffset == -1) toOffset = this.contentDOM!.childNodes.length
        break
      }
      offset = end
    }
    return {node: this.contentDOM!, from, to, fromOffset, toOffset}
  }

  emptyChildAt(side: number): boolean {
    if (this.border || !this.contentDOM || !this.children.length) return false
    let child = this.children[side < 0 ? 0 : this.children.length - 1]
    return child.size == 0 || child.emptyChildAt(side)
  }

  domAfterPos(pos: number): DOMNode {
    let {node, offset} = this.domFromPos(pos, 0)
    if (node.nodeType != 1 || offset == node.childNodes.length)
      throw new RangeError("No node after pos " + pos)
    return node.childNodes[offset]
  }

  // View descs are responsible for setting any selection that falls
  // entirely inside of them, so that custom implementations can do
  // custom things with the selection. Note that this falls apart when
  // a selection starts in such a node and ends in another, in which
  // case we just use whatever domFromPos produces as a best effort.
  setSelection(anchor: number, head: number, view: EditorView, force = false): void {
    // If the selection falls entirely in a child, give it to that child
    let from = Math.min(anchor, head), to = Math.max(anchor, head)
    for (let i = 0, offset = 0; i < this.children.length; i++) {
      let child = this.children[i], end = offset + child.size
      if (from > offset && to < end)
        return child.setSelection(anchor - offset - child.border, head - offset - child.border, view, force)
      offset = end
    }

    let anchorDOM = this.domFromPos(anchor, anchor ? -1 : 1)
    let headDOM = head == anchor ? anchorDOM : this.domFromPos(head, head ? -1 : 1)
    let domSel = (view.root as Document).getSelection()!
    let selRange = view.domSelectionRange()

    let brKludge = false
    // On Firefox, using Selection.collapse to put the cursor after a
    // BR node for some reason doesn't always work (#1073). On Safari,
    // the cursor sometimes inexplicable visually lags behind its
    // reported position in such situations (#1092).
    if ((browser.gecko || browser.safari) && anchor == head) {
      let {node, offset} = anchorDOM
      if (node.nodeType == 3) {
        brKludge = !!(offset && node.nodeValue![offset - 1] == "\n")
        // Issue #1128
        if (brKludge && offset == node.nodeValue!.length) {
           for (let scan: DOMNode | null = node, after; scan; scan = scan.parentNode) {
            if (after = scan.nextSibling) {
              if (after.nodeName == "BR")
                anchorDOM = headDOM = {node: after.parentNode!, offset: domIndex(after) + 1}
              break
            }
            let desc = scan.pmViewDesc
            if (desc && desc.node && desc.node.isBlock) break
          }
        }
      } else {
        let prev = node.childNodes[offset - 1]
        brKludge = prev && (prev.nodeName == "BR" || (prev as HTMLElement).contentEditable == "false")
      }
    }
    // Firefox can act strangely when the selection is in front of an
    // uneditable node. See #1163 and https://bugzilla.mozilla.org/show_bug.cgi?id=1709536
    if (browser.gecko && selRange.focusNode && selRange.focusNode != headDOM.node && selRange.focusNode.nodeType == 1) {
      let after = selRange.focusNode.childNodes[selRange.focusOffset]
      if (after && (after as HTMLElement).contentEditable == "false") force = true
    }

    if (!(force || brKludge && browser.safari) &&
        isEquivalentPosition(anchorDOM.node, anchorDOM.offset, selRange.anchorNode!, selRange.anchorOffset) &&
        isEquivalentPosition(headDOM.node, headDOM.offset, selRange.focusNode!, selRange.focusOffset))
      return

    // Selection.extend can be used to create an 'inverted' selection
    // (one where the focus is before the anchor), but not all
    // browsers support it yet.
    let domSelExtended = false
    if ((domSel.extend || anchor == head) && !(brKludge && browser.gecko)) {
      domSel.collapse(anchorDOM.node, anchorDOM.offset)
      try {
        if (anchor != head)
          domSel.extend(headDOM.node, headDOM.offset)
        domSelExtended = true
      } catch (_) {
        // In some cases with Chrome the selection is empty after calling
        // collapse, even when it should be valid. This appears to be a bug, but
        // it is difficult to isolate. If this happens fallback to the old path
        // without using extend.
        // Similarly, this could crash on Safari if the editor is hidden, and
        // there was no selection.
      }
    }
    if (!domSelExtended) {
      if (anchor > head) { let tmp = anchorDOM; anchorDOM = headDOM; headDOM = tmp }
      let range = document.createRange()
      range.setEnd(headDOM.node, headDOM.offset)
      range.setStart(anchorDOM.node, anchorDOM.offset)
      domSel.removeAllRanges()
      domSel.addRange(range)
    }
  }

  ignoreMutation(mutation: ViewMutationRecord): boolean {
    return !this.contentDOM && mutation.type != "selection"
  }

  get contentLost() {
    return this.contentDOM && this.contentDOM != this.dom && !this.dom.contains(this.contentDOM)
  }

  // Remove a subtree of the element tree that has been touched
  // by a DOM change, so that the next update will redraw it.
  markDirty(from: number, to: number) {
    for (let offset = 0, i = 0; i < this.children.length; i++) {
      let child = this.children[i], end = offset + child.size
      if (offset == end ? from <= end && to >= offset : from < end && to > offset) {
        let startInside = offset + child.border, endInside = end - child.border
        if (from >= startInside && to <= endInside) {
          this.dirty = from == offset || to == end ? CONTENT_DIRTY : CHILD_DIRTY
          if (from == startInside && to == endInside &&
              (child.contentLost || child.dom.parentNode != this.contentDOM)) child.dirty = NODE_DIRTY
          else child.markDirty(from - startInside, to - startInside)
          return
        } else {
          child.dirty = child.dom == child.contentDOM && child.dom.parentNode == this.contentDOM && !child.children.length
            ? CONTENT_DIRTY : NODE_DIRTY
        }
      }
      offset = end
    }
    this.dirty = CONTENT_DIRTY
  }

  markParentsDirty() {
    let level = 1
    for (let node = this.parent; node; node = node.parent, level++) {
      let dirty = level == 1 ? CONTENT_DIRTY : CHILD_DIRTY
      if (node.dirty < dirty) node.dirty = dirty
    }
  }

  get domAtom() { return false }

  get ignoreForCoords() { return false }

  get ignoreForSelection() { return false }

  isText(text: string) { return false }
}

// A widget desc represents a widget decoration, which is a DOM node
// drawn between the document nodes.
class WidgetViewDesc extends ViewDesc {
  constructor(parent: ViewDesc, readonly widget: Decoration, view: EditorView, pos: number) {
    let self: WidgetViewDesc, dom = (widget.type as any).toDOM as WidgetConstructor
    if (typeof dom == "function") dom = dom(view, () => {
      if (!self) return pos
      if (self.parent) return self.parent.posBeforeChild(self)
    })
    if (!widget.type.spec.raw) {
      if (dom.nodeType != 1) {
        let wrap = document.createElement("span")
        wrap.appendChild(dom)
        dom = wrap
      }
      ;(dom as HTMLElement).contentEditable = "false"
      ;(dom as HTMLElement).classList.add("ProseMirror-widget")
    }
    super(parent, [], dom, null)
    this.widget = widget
    self = this
  }

  matchesWidget(widget: Decoration) {
    return this.dirty == NOT_DIRTY && widget.type.eq(this.widget.type)
  }

  parseRule() { return {ignore: true} }

  stopEvent(event: Event) {
    let stop = this.widget.spec.stopEvent
    return stop ? stop(event) : false
  }

  ignoreMutation(mutation: ViewMutationRecord) {
    return mutation.type != "selection" || this.widget.spec.ignoreSelection
  }

  destroy() {
    this.widget.type.destroy(this.dom)
    super.destroy()
  }

  get domAtom() { return true }

  get ignoreForSelection() { return !!this.widget.type.spec.relaxedSide }

  get side() { return (this.widget.type as any).side as number }
}

class CompositionViewDesc extends ViewDesc {
  constructor(parent: ViewDesc, dom: DOMNode, readonly textDOM: Text, readonly text: string) {
    super(parent, [], dom, null)
  }

  get size() { return this.text.length }

  localPosFromDOM(dom: DOMNode, offset: number) {
    if (dom != this.textDOM) return this.posAtStart + (offset ? this.size : 0)
    return this.posAtStart + offset
  }

  domFromPos(pos: number) {
    return {node: this.textDOM, offset: pos}
  }

  ignoreMutation(mut: ViewMutationRecord) {
    return mut.type === 'characterData' && mut.target.nodeValue == mut.oldValue
   }
}

// A mark desc represents a mark. May have multiple children,
// depending on how the mark is split. Note that marks are drawn using
// a fixed nesting order, for simplicity and predictability, so in
// some cases they will be split more often than would appear
// necessary.
class MarkViewDesc extends ViewDesc {
  constructor(parent: ViewDesc, readonly mark: Mark, dom: DOMNode, contentDOM: HTMLElement, readonly spec: MarkView) {
    super(parent, [], dom, contentDOM)
  }

  static create(parent: ViewDesc, mark: Mark, inline: boolean, view: EditorView) {
    let custom = view.nodeViews[mark.type.name]
    let spec: {dom: HTMLElement, contentDOM?: HTMLElement} = custom && (custom as any)(mark, view, inline)
    if (!spec || !spec.dom)
      spec = (DOMSerializer.renderSpec as any)(document, mark.type.spec.toDOM!(mark, inline), null, mark.attrs) as any
    return new MarkViewDesc(parent, mark, spec.dom, spec.contentDOM || spec.dom as HTMLElement, spec)
  }

  parseRule() {
    if ((this.dirty & NODE_DIRTY) || this.mark.type.spec.reparseInView) return null
    return {mark: this.mark.type.name, attrs: this.mark.attrs, contentElement: this.contentDOM!}
  }

  matchesMark(mark: Mark) { return this.dirty != NODE_DIRTY && this.mark.eq(mark) }

  markDirty(from: number, to: number) {
    super.markDirty(from, to)
    // Move dirty info to nearest node view
    if (this.dirty != NOT_DIRTY) {
      let parent = this.parent!
      while (!parent.node) parent = parent.parent!
      if (parent.dirty < this.dirty) parent.dirty = this.dirty
      this.dirty = NOT_DIRTY
    }
  }

  slice(from: number, to: number, view: EditorView) {
    let copy = MarkViewDesc.create(this.parent!, this.mark, true, view)
    let nodes = this.children, size = this.size
    if (to < size) nodes = replaceNodes(nodes, to, size, view)
    if (from > 0) nodes = replaceNodes(nodes, 0, from, view)
    for (let i = 0; i < nodes.length; i++) nodes[i].parent = copy
    copy.children = nodes
    return copy
  }

  ignoreMutation(mutation: ViewMutationRecord) {
    return this.spec.ignoreMutation ? this.spec.ignoreMutation(mutation) : super.ignoreMutation(mutation)
  }

  destroy() {
    if (this.spec.destroy) this.spec.destroy()
    super.destroy()
  }
}

// Node view descs are the main, most common type of view desc, and
// correspond to an actual node in the document. Unlike mark descs,
// they populate their child array themselves.
export class NodeViewDesc extends ViewDesc {
  constructor(
    parent: ViewDesc | undefined,
    public node: Node,
    public outerDeco: readonly Decoration[],
    public innerDeco: DecorationSource,
    dom: DOMNode,
    contentDOM: HTMLElement | null,
    readonly nodeDOM: DOMNode,
    view: EditorView,
    pos: number
  ) {
    super(parent, [], dom, contentDOM)
  }

  // By default, a node is rendered using the `toDOM` method from the
  // node type spec. But client code can use the `nodeViews` spec to
  // supply a custom node view, which can influence various aspects of
  // the way the node works.
  //
  // (Using subclassing for this was intentionally decided against,
  // since it'd require exposing a whole slew of finicky
  // implementation details to the user code that they probably will
  // never need.)
  static create(parent: ViewDesc | undefined, node: Node, outerDeco: readonly Decoration[],
                innerDeco: DecorationSource, view: EditorView, pos: number) {
    let custom = view.nodeViews[node.type.name], descObj: ViewDesc
    let spec: NodeView | undefined = custom && (custom as any)(node, view, () => {
      // (This is a function that allows the custom view to find its
      // own position)
      if (!descObj) return pos
      if (descObj.parent) return descObj.parent.posBeforeChild(descObj)
    }, outerDeco, innerDeco)

    let dom = spec && spec.dom, contentDOM = spec && spec.contentDOM
    if (node.isText) {
      if (!dom) dom = document.createTextNode(node.text!)
      else if (dom.nodeType != 3) throw new RangeError("Text must be rendered as a DOM text node")
    } else if (!dom) {
      let spec = (DOMSerializer.renderSpec as any)(document, node.type.spec.toDOM!(node), null, node.attrs)
      ;({dom, contentDOM} = spec as {dom: DOMNode, contentDOM?: HTMLElement})
    }
    if (!contentDOM && !node.isText && dom.nodeName != "BR") { // Chrome gets confused by <br contenteditable=false>
      if (!(dom as HTMLElement).hasAttribute("contenteditable")) (dom as HTMLElement).contentEditable = "false"
      if (node.type.spec.draggable) (dom as HTMLElement).draggable = true
    }

    let nodeDOM = dom
    dom = applyOuterDeco(dom, outerDeco, node)

    if (spec)
      return descObj = new CustomNodeViewDesc(parent, node, outerDeco, innerDeco, dom, contentDOM || null, nodeDOM,
                                              spec, view, pos + 1)
    else if (node.isText)
      return new TextViewDesc(parent, node, outerDeco, innerDeco, dom, nodeDOM, view)
    else
      return new NodeViewDesc(parent, node, outerDeco, innerDeco, dom, contentDOM || null, nodeDOM, view, pos + 1)
  }

  parseRule() {
    // Experimental kludge to allow opt-in re-parsing of nodes
    if (this.node.type.spec.reparseInView) return null
    // FIXME the assumption that this can always return the current
    // attrs means that if the user somehow manages to change the
    // attrs in the dom, that won't be picked up. Not entirely sure
    // whether this is a problem
    let rule: Omit<TagParseRule, "tag"> = {node: this.node.type.name, attrs: this.node.attrs}
    if (this.node.type.whitespace == "pre") rule.preserveWhitespace = "full"
    if (!this.contentDOM) {
      rule.getContent = () => this.node.content
    } else if (!this.contentLost) {
      rule.contentElement = this.contentDOM
    } else {
      // Chrome likes to randomly recreate parent nodes when
      // backspacing things. When that happens, this tries to find the
      // new parent.
      for (let i = this.children.length - 1; i >= 0; i--) {
        let child = this.children[i]
        if (this.dom.contains(child.dom.parentNode)) {
          rule.contentElement = child.dom.parentNode as HTMLElement
          break
        }
      }
      if (!rule.contentElement) rule.getContent = () => Fragment.empty
    }
    return rule
  }

  matchesNode(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource) {
    return this.dirty == NOT_DIRTY && node.eq(this.node) &&
      sameOuterDeco(outerDeco, this.outerDeco) && innerDeco.eq(this.innerDeco)
  }

  get size() { return this.node.nodeSize }

  get border() { return this.node.isLeaf ? 0 : 1 }

  // Syncs `this.children` to match `this.node.content` and the local
  // decorations, possibly introducing nesting for marks. Then, in a
  // separate step, syncs the DOM inside `this.contentDOM` to
  // `this.children`.
  updateChildren(view: EditorView, pos: number) {
    let inline = this.node.inlineContent, off = pos
    let composition = view.composing ? this.localCompositionInfo(view, pos) : null
    let localComposition = composition && composition.pos > -1 ? composition : null
    let compositionInChild = composition && composition.pos < 0
    let updater = new ViewTreeUpdater(this, localComposition && localComposition.node, view)
    iterDeco(this.node, this.innerDeco, (widget, i, insideNode) => {
      if (widget.spec.marks)
        updater.syncToMarks(widget.spec.marks, inline, view, i)
      else if ((widget.type as WidgetType).side >= 0 && !insideNode)
        updater.syncToMarks(i == this.node.childCount ? Mark.none : this.node.child(i).marks, inline, view, i)
      // If the next node is a desc matching this widget, reuse it,
      // otherwise insert the widget as a new view desc.
      updater.placeWidget(widget, view, off)
    }, (child, outerDeco, innerDeco, i) => {
      // Make sure the wrapping mark descs match the node's marks.
      updater.syncToMarks(child.marks, inline, view, i)
      // Try several strategies for drawing this node
      let compIndex
      if (updater.findNodeMatch(child, outerDeco, innerDeco, i)) {
        // Found precise match with existing node view
      } else if (compositionInChild && view.state.selection.from > off &&
                 view.state.selection.to < off + child.nodeSize &&
                 (compIndex = updater.findIndexWithChild(composition!.node)) > -1 &&
                 updater.updateNodeAt(child, outerDeco, innerDeco, compIndex, view)) {
        // Updated the specific node that holds the composition
      } else if (updater.updateNextNode(child, outerDeco, innerDeco, view, i, off)) {
        // Could update an existing node to reflect this node
      } else {
        // Add it as a new view
        updater.addNode(child, outerDeco, innerDeco, view, off)
      }
      off += child.nodeSize
    })
    // Drop all remaining descs after the current position.
    updater.syncToMarks([], inline, view, 0)
    if (this.node.isTextblock) updater.addTextblockHacks()
    updater.destroyRest()

    // Sync the DOM if anything changed
    if (updater.changed || this.dirty == CONTENT_DIRTY) {
      // May have to protect focused DOM from being changed if a composition is active
      if (localComposition) this.protectLocalComposition(view, localComposition)
      renderDescs(this.contentDOM!, this.children, view)
      if (browser.ios) iosHacks(this.dom as HTMLElement)
    }
  }

  localCompositionInfo(view: EditorView, pos: number): {node: Text, pos: number, text: string} | null {
    // Only do something if both the selection and a focused text node
    // are inside of this node
    let {from, to} = view.state.selection
    if (!(view.state.selection instanceof TextSelection) || from < pos || to > pos + this.node.content.size) return null
    let textNode = view.input.compositionNode
    if (!textNode || !this.dom.contains(textNode.parentNode)) return null

    if (this.node.inlineContent) {
      // Find the text in the focused node in the node, stop if it's not
      // there (may have been modified through other means, in which
      // case it should overwritten)
      let text = textNode.nodeValue!
      let textPos = findTextInFragment(this.node.content, text, from - pos, to - pos)
      return textPos < 0 ? null : {node: textNode, pos: textPos, text}
    } else {
      return {node: textNode, pos: -1, text: ""}
    }
  }

  protectLocalComposition(view: EditorView, {node, pos, text}: {node: Text, pos: number, text: string}) {
    // The node is already part of a local view desc, leave it there
    if (this.getDesc(node)) return

    // Create a composition view for the orphaned nodes
    let topNode: DOMNode = node
    for (;; topNode = topNode.parentNode!) {
      if (topNode.parentNode == this.contentDOM) break
      while (topNode.previousSibling) topNode.parentNode!.removeChild(topNode.previousSibling)
      while (topNode.nextSibling) topNode.parentNode!.removeChild(topNode.nextSibling)
      if (topNode.pmViewDesc) topNode.pmViewDesc = undefined
    }
    let desc = new CompositionViewDesc(this, topNode, node, text)
    view.input.compositionNodes.push(desc)

    // Patch up this.children to contain the composition view
    this.children = replaceNodes(this.children, pos, pos + text.length, view, desc)
  }

  // If this desc must be updated to match the given node decoration,
  // do so and return true.
  update(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, view: EditorView) {
    if (this.dirty == NODE_DIRTY ||
        !node.sameMarkup(this.node)) return false
    this.updateInner(node, outerDeco, innerDeco, view)
    return true
  }

  updateInner(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, view: EditorView) {
    this.updateOuterDeco(outerDeco)
    this.node = node
    this.innerDeco = innerDeco
    if (this.contentDOM) this.updateChildren(view, this.posAtStart)
    this.dirty = NOT_DIRTY
  }

  updateOuterDeco(outerDeco: readonly Decoration[]) {
    if (sameOuterDeco(outerDeco, this.outerDeco)) return
    let needsWrap = this.nodeDOM.nodeType != 1
    let oldDOM = this.dom
    this.dom = patchOuterDeco(this.dom, this.nodeDOM,
                              computeOuterDeco(this.outerDeco, this.node, needsWrap),
                              computeOuterDeco(outerDeco, this.node, needsWrap))
    if (this.dom != oldDOM) {
      oldDOM.pmViewDesc = undefined
      this.dom.pmViewDesc = this
    }
    this.outerDeco = outerDeco
  }

  // Mark this node as being the selected node.
  selectNode() {
    if (this.nodeDOM.nodeType == 1) {
      ;(this.nodeDOM as HTMLElement).classList.add("ProseMirror-selectednode")
      if (this.contentDOM || !this.node.type.spec.draggable) (this.nodeDOM as HTMLElement).draggable = true
    }
  }

  // Remove selected node marking from this node.
  deselectNode() {
    if (this.nodeDOM.nodeType == 1) {
      ;(this.nodeDOM as HTMLElement).classList.remove("ProseMirror-selectednode")
      if (this.contentDOM || !this.node.type.spec.draggable) (this.nodeDOM as HTMLElement).removeAttribute("draggable")
    }
  }

  get domAtom() { return this.node.isAtom }
}

// Create a view desc for the top-level document node, to be exported
// and used by the view class.
export function docViewDesc(doc: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource,
                            dom: HTMLElement, view: EditorView): NodeViewDesc {
  applyOuterDeco(dom, outerDeco, doc)
  let docView = new NodeViewDesc(undefined, doc, outerDeco, innerDeco, dom, dom, dom, view, 0)
  if (docView.contentDOM) docView.updateChildren(view, 0)
  return docView
}

class TextViewDesc extends NodeViewDesc {
  constructor(parent: ViewDesc | undefined, node: Node, outerDeco: readonly Decoration[],
              innerDeco: DecorationSource, dom: DOMNode, nodeDOM: DOMNode, view: EditorView) {
    super(parent, node, outerDeco, innerDeco, dom, null, nodeDOM, view, 0)
  }

  parseRule() {
    let skip = this.nodeDOM.parentNode
    while (skip && skip != this.dom && !(skip as any).pmIsDeco) skip = skip.parentNode
    return {skip: (skip || true) as any}
  }

  update(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, view: EditorView) {
    if (this.dirty == NODE_DIRTY || (this.dirty != NOT_DIRTY && !this.inParent()) ||
        !node.sameMarkup(this.node)) return false
    this.updateOuterDeco(outerDeco)
    if ((this.dirty != NOT_DIRTY || node.text != this.node.text) && node.text != this.nodeDOM.nodeValue) {
      this.nodeDOM.nodeValue = node.text!
      if (view.trackWrites == this.nodeDOM) view.trackWrites = null
    }
    this.node = node
    this.dirty = NOT_DIRTY
    return true
  }

  inParent() {
    let parentDOM = this.parent!.contentDOM
    for (let n: DOMNode | null = this.nodeDOM; n; n = n.parentNode) if (n == parentDOM) return true
    return false
  }

  domFromPos(pos: number) {
    return {node: this.nodeDOM, offset: pos}
  }

  localPosFromDOM(dom: DOMNode, offset: number, bias: number) {
    if (dom == this.nodeDOM) return this.posAtStart + Math.min(offset, this.node.text!.length)
    return super.localPosFromDOM(dom, offset, bias)
  }

  ignoreMutation(mutation: ViewMutationRecord) {
    return mutation.type != "characterData" && mutation.type != "selection"
  }

  slice(from: number, to: number, view: EditorView) {
    let node = this.node.cut(from, to), dom = document.createTextNode(node.text!)
    return new TextViewDesc(this.parent, node, this.outerDeco, this.innerDeco, dom, dom, view)
  }

  markDirty(from: number, to: number) {
    super.markDirty(from, to)
    if (this.dom != this.nodeDOM && (from == 0 || to == this.nodeDOM.nodeValue!.length))
      this.dirty = NODE_DIRTY
  }

  get domAtom() { return false }

  isText(text: string) { return this.node.text == text }
}

// A dummy desc used to tag trailing BR or IMG nodes created to work
// around contentEditable terribleness.
class TrailingHackViewDesc extends ViewDesc {
  parseRule() { return {ignore: true} }
  matchesHack(nodeName: string) { return this.dirty == NOT_DIRTY && this.dom.nodeName == nodeName }
  get domAtom() { return true }
  get ignoreForCoords() { return this.dom.nodeName == "IMG" }
}

// A separate subclass is used for customized node views, so that the
// extra checks only have to be made for nodes that are actually
// customized.
class CustomNodeViewDesc extends NodeViewDesc {
  constructor(parent: ViewDesc | undefined, node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource,
              dom: DOMNode, contentDOM: HTMLElement | null, nodeDOM: DOMNode, readonly spec: NodeView,
              view: EditorView, pos: number) {
    super(parent, node, outerDeco, innerDeco, dom, contentDOM, nodeDOM, view, pos)
  }

  // A custom `update` method gets to decide whether the update goes
  // through. If it does, and there's a `contentDOM` node, our logic
  // updates the children.
  update(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, view: EditorView) {
    if (this.dirty == NODE_DIRTY) return false
    if (this.spec.update && (this.node.type == node.type || this.spec.multiType)) {
      let result = this.spec.update(node, outerDeco, innerDeco)
      if (result) this.updateInner(node, outerDeco, innerDeco, view)
      return result
    } else if (!this.contentDOM && !node.isLeaf) {
      return false
    } else {
      return super.update(node, outerDeco, innerDeco, view)
    }
  }

  selectNode() {
    this.spec.selectNode ? this.spec.selectNode() : super.selectNode()
  }

  deselectNode() {
    this.spec.deselectNode ? this.spec.deselectNode() : super.deselectNode()
  }

  setSelection(anchor: number, head: number, view: EditorView, force: boolean) {
    this.spec.setSelection ? this.spec.setSelection(anchor, head, view.root)
      : super.setSelection(anchor, head, view, force)
  }

  destroy() {
    if (this.spec.destroy) this.spec.destroy()
    super.destroy()
  }

  stopEvent(event: Event) {
    return this.spec.stopEvent ? this.spec.stopEvent(event) : false
  }

  ignoreMutation(mutation: ViewMutationRecord) {
    return this.spec.ignoreMutation ? this.spec.ignoreMutation(mutation) : super.ignoreMutation(mutation)
  }
}

// Sync the content of the given DOM node with the nodes associated
// with the given array of view descs, recursing into mark descs
// because this should sync the subtree for a whole node at a time.
function renderDescs(parentDOM: HTMLElement, descs: readonly ViewDesc[], view: EditorView) {
  let dom = parentDOM.firstChild, written = false
  for (let i = 0; i < descs.length; i++) {
    let desc = descs[i], childDOM = desc.dom
    if (childDOM.parentNode == parentDOM) {
      while (childDOM != dom) { dom = rm(dom!); written = true }
      dom = dom.nextSibling
    } else {
      written = true
      parentDOM.insertBefore(childDOM, dom)
    }
    if (desc instanceof MarkViewDesc) {
      let pos = dom ? dom.previousSibling : parentDOM.lastChild
      renderDescs(desc.contentDOM!, desc.children, view)
      dom = pos ? pos.nextSibling : parentDOM.firstChild
    }
  }
  while (dom) { dom = rm(dom); written = true }
  if (written && view.trackWrites == parentDOM) view.trackWrites = null
}

type OuterDecoLevel = {[attr: string]: string}

const OuterDecoLevel: {new (nodeName?: string): OuterDecoLevel} = function(this: any, nodeName?: string) {
  if (nodeName) this.nodeName = nodeName
} as any
OuterDecoLevel.prototype = Object.create(null)

const noDeco = [new OuterDecoLevel]

function computeOuterDeco(outerDeco: readonly Decoration[], node: Node, needsWrap: boolean) {
  if (outerDeco.length == 0) return noDeco

  let top = needsWrap ? noDeco[0] : new OuterDecoLevel, result = [top]

  for (let i = 0; i < outerDeco.length; i++) {
    let attrs = (outerDeco[i].type as NodeType).attrs
    if (!attrs) continue
    if (attrs.nodeName)
      result.push(top = new OuterDecoLevel(attrs.nodeName))

    for (let name in attrs) {
      let val = attrs[name]
      if (val == null) continue
      if (needsWrap && result.length == 1)
        result.push(top = new OuterDecoLevel(node.isInline ? "span" : "div"))
      if (name == "class") top.class = (top.class ? top.class + " " : "") + val
      else if (name == "style") top.style = (top.style ? top.style + ";" : "") + val
      else if (name != "nodeName") top[name] = val
    }
  }

  return result
}

function patchOuterDeco(outerDOM: DOMNode, nodeDOM: DOMNode,
                        prevComputed: readonly OuterDecoLevel[], curComputed: readonly OuterDecoLevel[]) {
  // Shortcut for trivial case
  if (prevComputed == noDeco && curComputed == noDeco) return nodeDOM

  let curDOM = nodeDOM
  for (let i = 0; i < curComputed.length; i++) {
    let deco = curComputed[i], prev = prevComputed[i]
    if (i) {
      let parent: DOMNode | null
      if (prev && prev.nodeName == deco.nodeName && curDOM != outerDOM &&
          (parent = curDOM.parentNode) && parent.nodeName!.toLowerCase() == deco.nodeName) {
        curDOM = parent
      } else {
        parent = document.createElement(deco.nodeName)
        ;(parent as any).pmIsDeco = true
        parent.appendChild(curDOM)
        prev = noDeco[0]
        curDOM = parent
      }
    }
    patchAttributes(curDOM as HTMLElement, prev || noDeco[0], deco)
  }
  return curDOM
}

function patchAttributes(dom: HTMLElement, prev: {[name: string]: string}, cur: {[name: string]: string}) {
  for (let name in prev)
    if (name != "class" && name != "style" && name != "nodeName" && !(name in cur))
      dom.removeAttribute(name)
  for (let name in cur)
    if (name != "class" && name != "style" && name != "nodeName" && cur[name] != prev[name])
      dom.setAttribute(name, cur[name])
  if (prev.class != cur.class) {
    let prevList = prev.class ? prev.class.split(" ").filter(Boolean) : []
    let curList = cur.class ? cur.class.split(" ").filter(Boolean) : []
    for (let i = 0; i < prevList.length; i++) if (curList.indexOf(prevList[i]) == -1)
      dom.classList.remove(prevList[i])
    for (let i = 0; i < curList.length; i++) if (prevList.indexOf(curList[i]) == -1)
      dom.classList.add(curList[i])
    if (dom.classList.length == 0)
      dom.removeAttribute("class")
  }
  if (prev.style != cur.style) {
    if (prev.style) {
      let prop = /\s*([\w\-\xa1-\uffff]+)\s*:(?:"(?:\\.|[^"])*"|'(?:\\.|[^'])*'|\(.*?\)|[^;])*/g, m
      while (m = prop.exec(prev.style))
        dom.style.removeProperty(m[1])
    }
    if (cur.style)
      dom.style.cssText += cur.style
  }
}

function applyOuterDeco(dom: DOMNode, deco: readonly Decoration[], node: Node) {
  return patchOuterDeco(dom, dom, noDeco, computeOuterDeco(deco, node, dom.nodeType != 1))
}

function sameOuterDeco(a: readonly Decoration[], b: readonly Decoration[]) {
  if (a.length != b.length) return false
  for (let i = 0; i < a.length; i++) if (!a[i].type.eq(b[i].type)) return false
  return true
}

// Remove a DOM node and return its next sibling.
function rm(dom: DOMNode) {
  let next = dom.nextSibling
  dom.parentNode!.removeChild(dom)
  return next
}

// Helper class for incrementally updating a tree of mark descs and
// the widget and node descs inside of them.
class ViewTreeUpdater {
  // Index into `this.top`'s child array, represents the current
  // update position.
  index = 0
  // When entering a mark, the current top and index are pushed
  // onto this.
  stack: (ViewDesc | number)[] = []
  // Tracks whether anything was changed
  changed = false
  preMatch: {index: number, matched: Map<ViewDesc, number>, matches: readonly ViewDesc[]}
  top: ViewDesc

  constructor(top: NodeViewDesc, readonly lock: DOMNode | null, private readonly view: EditorView) {
    this.top = top
    this.preMatch = preMatch(top.node.content, top)
  }

  // Destroy and remove the children between the given indices in
  // `this.top`.
  destroyBetween(start: number, end: number) {
    if (start == end) return
    for (let i = start; i < end; i++) this.top.children[i].destroy()
    this.top.children.splice(start, end - start)
    this.changed = true
  }

  // Destroy all remaining children in `this.top`.
  destroyRest() {
    this.destroyBetween(this.index, this.top.children.length)
  }

  // Sync the current stack of mark descs with the given array of
  // marks, reusing existing mark descs when possible.
  syncToMarks(marks: readonly Mark[], inline: boolean, view: EditorView, parentIndex: number) {
    let keep = 0, depth = this.stack.length >> 1
    let maxKeep = Math.min(depth, marks.length)
    while (keep < maxKeep &&
           (keep == depth - 1 ? this.top : this.stack[(keep + 1) << 1] as ViewDesc)
             .matchesMark(marks[keep]) && marks[keep].type.spec.spanning !== false)
      keep++

    while (keep < depth) {
      this.destroyRest()
      this.top.dirty = NOT_DIRTY
      this.index = this.stack.pop() as number
      this.top = this.stack.pop() as ViewDesc
      depth--
    }
    while (depth < marks.length) {
      this.stack.push(this.top, this.index + 1)
      let found = -1, scanTo = this.top.children.length
      if (parentIndex < this.preMatch.index) scanTo = Math.min(this.index + 3, scanTo)
      for (let i = this.index; i < scanTo; i++) {
        let next = this.top.children[i]
        if (next.matchesMark(marks[depth]) && !this.isLocked(next.dom)) { found = i; break }
      }
      if (found > -1) {
        if (found > this.index) {
          this.changed = true
          this.destroyBetween(this.index, found)
        }
        this.top = this.top.children[this.index]
      } else {
        let markDesc = MarkViewDesc.create(this.top, marks[depth], inline, view)
        this.top.children.splice(this.index, 0, markDesc)
        this.top = markDesc
        this.changed = true
      }
      this.index = 0
      depth++
    }
  }

  // Try to find a node desc matching the given data. Skip over it and
  // return true when successful.
  findNodeMatch(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, index: number): boolean {
    let found = -1, targetDesc
    if (index >= this.preMatch.index &&
        (targetDesc = this.preMatch.matches[index - this.preMatch.index]).parent == this.top &&
        targetDesc.matchesNode(node, outerDeco, innerDeco)) {
      found = this.top.children.indexOf(targetDesc, this.index)
    } else {
      for (let i = this.index, e = Math.min(this.top.children.length, i + 5); i < e; i++) {
        let child = this.top.children[i]
        if (child.matchesNode(node, outerDeco, innerDeco) && !this.preMatch.matched.has(child)) {
          found = i
          break
        }
      }
    }
    if (found < 0) return false
    this.destroyBetween(this.index, found)
    this.index++
    return true
  }

  updateNodeAt(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, index: number, view: EditorView) {
    let child = this.top.children[index] as NodeViewDesc
    if (child.dirty == NODE_DIRTY && child.dom == child.contentDOM) child.dirty = CONTENT_DIRTY
    if (!child.update(node, outerDeco, innerDeco, view)) return false
    this.destroyBetween(this.index, index)
    this.index++
    return true
  }

  findIndexWithChild(domNode: DOMNode) {
    for (;;) {
      let parent = domNode.parentNode
      if (!parent) return -1
      if (parent == this.top.contentDOM) {
        let desc = domNode.pmViewDesc
        if (desc) for (let i = this.index; i < this.top.children.length; i++) {
          if (this.top.children[i] == desc) return i
        }
        return -1
      }
      domNode = parent
    }
  }

  // Try to update the next node, if any, to the given data. Checks
  // pre-matches to avoid overwriting nodes that could still be used.
  updateNextNode(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource,
                 view: EditorView, index: number, pos: number): boolean {
    for (let i = this.index; i < this.top.children.length; i++) {
      let next = this.top.children[i]
      if (next instanceof NodeViewDesc) {
        let preMatch = this.preMatch.matched.get(next)
        if (preMatch != null && preMatch != index) return false
        let nextDOM = next.dom, updated

        // Can't update if nextDOM is or contains this.lock, except if
        // it's a text node whose content already matches the new text
        // and whose decorations match the new ones.
        let locked = this.isLocked(nextDOM) &&
            !(node.isText && next.node && next.node.isText && next.nodeDOM.nodeValue == node.text &&
              next.dirty != NODE_DIRTY && sameOuterDeco(outerDeco, next.outerDeco))
        if (!locked && next.update(node, outerDeco, innerDeco, view)) {
          this.destroyBetween(this.index, i)
          if (next.dom != nextDOM) this.changed = true
          this.index++
          return true
        } else if (!locked && (updated = this.recreateWrapper(next, node, outerDeco, innerDeco, view, pos))) {
          this.destroyBetween(this.index, i)
          this.top.children[this.index] = updated
          if (updated.contentDOM) {
            updated.dirty = CONTENT_DIRTY
            updated.updateChildren(view, pos + 1)
            updated.dirty = NOT_DIRTY
          }
          this.changed = true
          this.index++
          return true
        }
        break
      }
    }
    return false
  }

  // When a node with content is replaced by a different node with
  // identical content, move over its children.
  recreateWrapper(next: NodeViewDesc, node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource,
                  view: EditorView, pos: number) {
    if (next.dirty || node.isAtom || !next.children.length ||
        !next.node.content.eq(node.content) ||
        !sameOuterDeco(outerDeco, next.outerDeco) || !innerDeco.eq(next.innerDeco)) return null
    let wrapper = NodeViewDesc.create(this.top, node, outerDeco, innerDeco, view, pos)
    if (wrapper.contentDOM) {
      wrapper.children = next.children
      next.children = []
      for (let ch of wrapper.children) ch.parent = wrapper
    }
    next.destroy()
    return wrapper
  }

  // Insert the node as a newly created node desc.
  addNode(node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, view: EditorView, pos: number) {
    let desc = NodeViewDesc.create(this.top, node, outerDeco, innerDeco, view, pos)
    if (desc.contentDOM) desc.updateChildren(view, pos + 1)
    this.top.children.splice(this.index++, 0, desc)
    this.changed = true
  }

  placeWidget(widget: Decoration, view: EditorView, pos: number) {
    let next = this.index < this.top.children.length ? this.top.children[this.index] : null
    if (next && next.matchesWidget(widget) &&
        (widget == (next as WidgetViewDesc).widget || !(next as any).widget.type.toDOM.parentNode)) {
      this.index++
    } else {
      let desc = new WidgetViewDesc(this.top, widget, view, pos)
      this.top.children.splice(this.index++, 0, desc)
      this.changed = true
    }
  }

  // Make sure a textblock looks and behaves correctly in
  // contentEditable.
  addTextblockHacks() {
    let lastChild = this.top.children[this.index - 1], parent = this.top
    while (lastChild instanceof MarkViewDesc) {
      parent = lastChild
      lastChild = parent.children[parent.children.length - 1]
    }

    if (!lastChild || // Empty textblock
        !(lastChild instanceof TextViewDesc) ||
        /\n$/.test(lastChild.node.text!) ||
        (this.view.requiresGeckoHackNode && /\s$/.test(lastChild.node.text!))) {
      // Avoid bugs in Safari's cursor drawing (#1165) and Chrome's mouse selection (#1152)
      if ((browser.safari || browser.chrome) && lastChild && (lastChild.dom as HTMLElement).contentEditable == "false")
        this.addHackNode("IMG", parent)
      this.addHackNode("BR", this.top)
    }
  }

  addHackNode(nodeName: string, parent: ViewDesc) {
    if (parent == this.top && this.index < parent.children.length && parent.children[this.index].matchesHack(nodeName)) {
      this.index++
    } else {
      let dom = document.createElement(nodeName)
      if (nodeName == "IMG") {
        dom.className = "ProseMirror-separator"
        ;(dom as HTMLImageElement).alt = ""
      }
      if (nodeName == "BR") dom.className = "ProseMirror-trailingBreak"
      let hack = new TrailingHackViewDesc(this.top, [], dom, null)
      if (parent != this.top) parent.children.push(hack)
      else parent.children.splice(this.index++, 0, hack)
      this.changed = true
    }
  }

  isLocked(node: DOMNode) {
    return this.lock && (node == this.lock || node.nodeType == 1 && node.contains(this.lock.parentNode))
  }
}

// Iterate from the end of the fragment and array of descs to find
// directly matching ones, in order to avoid overeagerly reusing those
// for other nodes.
function preMatch(frag: Fragment, parentDesc: ViewDesc): {
  // The fragment index of the first node that is part of the sequence
  // of matched nodes at the end of the fragment.
  index: number,
  // A map from matched descs to fragment indices.
  matched: Map<ViewDesc, number>,
  // The matched descs.
  matches: readonly ViewDesc[]
} {
  let curDesc = parentDesc, descI = curDesc.children.length
  let fI = frag.childCount, matched = new Map, matches = []
  outer: while (fI > 0) {
    let desc
    for (;;) {
      if (descI) {
        let next = curDesc.children[descI - 1]
        if (next instanceof MarkViewDesc) {
          curDesc = next
          descI = next.children.length
        } else {
          desc = next
          descI--
          break
        }
      } else if (curDesc == parentDesc) {
        break outer
      } else {
        descI = curDesc.parent!.children.indexOf(curDesc)
        curDesc = curDesc.parent!
      }
    }
    let node = desc.node
    if (!node) continue
    if (node != frag.child(fI - 1)) break
    --fI
    matched.set(desc, fI)
    matches.push(desc)
  }
  return {index: fI, matched, matches: matches.reverse()}
}

function compareSide(a: Decoration, b: Decoration) {
  return (a.type as WidgetType).side - (b.type as WidgetType).side
}

// This function abstracts iterating over the nodes and decorations in
// a fragment. Calls `onNode` for each node, with its local and child
// decorations. Splits text nodes when there is a decoration starting
// or ending inside of them. Calls `onWidget` for each widget.
function iterDeco(
  parent: Node,
  deco: DecorationSource,
  onWidget: (widget: Decoration, index: number, insideNode: boolean) => void,
  onNode: (node: Node, outerDeco: readonly Decoration[], innerDeco: DecorationSource, index: number) => void
) {
  let locals = deco.locals(parent), offset = 0
  // Simple, cheap variant for when there are no local decorations
  if (locals.length == 0) {
    for (let i = 0; i < parent.childCount; i++) {
      let child = parent.child(i)
      onNode(child, locals, deco.forChild(offset, child), i)
      offset += child.nodeSize
    }
    return
  }

  let decoIndex = 0, active = [], restNode = null
  for (let parentIndex = 0;;) {
    let widget, widgets
    while (decoIndex < locals.length && locals[decoIndex].to == offset) {
      let next = locals[decoIndex++]
      if (next.widget) {
        if (!widget) widget = next
        else (widgets || (widgets = [widget])).push(next)
      }
    }
    if (widget) {
      if (widgets) {
        widgets.sort(compareSide)
        for (let i = 0; i < widgets.length; i++) onWidget(widgets[i], parentIndex, !!restNode)
      } else {
        onWidget(widget, parentIndex, !!restNode)
      }
    }

    let child, index
    if (restNode) {
      index = -1
      child = restNode
      restNode = null
    } else if (parentIndex < parent.childCount) {
      index = parentIndex
      child = parent.child(parentIndex++)
    } else {
      break
    }

    for (let i = 0; i < active.length; i++) if (active[i].to <= offset) active.splice(i--, 1)
    while (decoIndex < locals.length && locals[decoIndex].from <= offset && locals[decoIndex].to > offset)
      active.push(locals[decoIndex++])

    let end = offset + child.nodeSize
    if (child.isText) {
      let cutAt = end
      if (decoIndex < locals.length && locals[decoIndex].from < cutAt) cutAt = locals[decoIndex].from
      for (let i = 0; i < active.length; i++) if (active[i].to < cutAt) cutAt = active[i].to
      if (cutAt < end) {
        restNode = child.cut(cutAt - offset)
        child = child.cut(0, cutAt - offset)
        end = cutAt
        index = -1
      }
    } else {
      while (decoIndex < locals.length && locals[decoIndex].to < end) decoIndex++
    }

    let outerDeco = child.isInline && !child.isLeaf ? active.filter(d => !d.inline) : active.slice()
    onNode(child, outerDeco, deco.forChild(offset, child), index)
    offset = end
  }
}

// List markers in Mobile Safari will mysteriously disappear
// sometimes. This works around that.
function iosHacks(dom: HTMLElement) {
  if (dom.nodeName == "UL" || dom.nodeName == "OL") {
    let oldCSS = dom.style.cssText
    dom.style.cssText = oldCSS + "; list-style: square !important"
    window.getComputedStyle(dom).listStyle
    dom.style.cssText = oldCSS
  }
}

// Find a piece of text in an inline fragment, overlapping from-to
function findTextInFragment(frag: Fragment, text: string, from: number, to: number) {
  for (let i = 0, pos = 0; i < frag.childCount && pos <= to;) {
    let child = frag.child(i++), childStart = pos
    pos += child.nodeSize
    if (!child.isText) continue
    let str = child.text!
    while (i < frag.childCount) {
      let next = frag.child(i++)
      pos += next.nodeSize
      if (!next.isText) break
      str += next.text
    }
    if (pos >= from) {
      if (pos >= to && str.slice(to - text.length - childStart, to - childStart) == text)
        return to - text.length
      let found = childStart < to ? str.lastIndexOf(text, to - childStart - 1) : -1
      if (found >= 0 && found + text.length + childStart >= from)
        return childStart + found
      if (from == to && str.length >= (to + text.length) - childStart &&
          str.slice(to - childStart, to - childStart + text.length) == text)
        return to
    }
  }
  return -1
}

// Replace range from-to in an array of view descs with replacement
// (may be null to just delete). This goes very much against the grain
// of the rest of this code, which tends to create nodes with the
// right shape in one go, rather than messing with them after
// creation, but is necessary in the composition hack.
function replaceNodes(nodes: readonly ViewDesc[], from: number, to: number, view: EditorView, replacement?: ViewDesc) {
  let result = []
  for (let i = 0, off = 0; i < nodes.length; i++) {
    let child = nodes[i], start = off, end = off += child.size
    if (start >= to || end <= from) {
      result.push(child)
    } else {
      if (start < from) result.push((child as MarkViewDesc | TextViewDesc).slice(0, from - start, view))
      if (replacement) {
        result.push(replacement)
        replacement = undefined
      }
      if (end > to) result.push((child as MarkViewDesc | TextViewDesc).slice(to - start, child.size, view))
    }
  }
  return result
}
