import {joinPoint, canJoin, findWrapping, liftTarget, canSplit,
        ReplaceStep, ReplaceAroundStep, replaceStep} from "prosemirror-transform"
import {Slice, Fragment, Node, NodeType, Attrs, MarkType, ResolvedPos, ContentMatch} from "prosemirror-model"
import {Selection, EditorState, Transaction, TextSelection, NodeSelection,
        SelectionRange, AllSelection, Command} from "prosemirror-state"
import {EditorView} from "prosemirror-view"

/// Delete the selection, if there is one.
export const deleteSelection: Command = (state, dispatch) => {
  if (state.selection.empty) return false
  if (dispatch) dispatch(state.tr.deleteSelection().scrollIntoView())
  return true
}

function atBlockStart(state: EditorState, view?: EditorView): ResolvedPos | null {
  let {$cursor} = state.selection as TextSelection
  if (!$cursor || (view ? !view.endOfTextblock("backward", state)
                        : $cursor.parentOffset > 0))
    return null
  return $cursor
}

/// If the selection is empty and at the start of a textblock, try to
/// reduce the distance between that block and the one before it—if
/// there's a block directly before it that can be joined, join them.
/// If not, try to move the selected block closer to the next one in
/// the document structure by lifting it out of its parent or moving it
/// into a parent of the previous block. Will use the view for accurate
/// (bidi-aware) start-of-textblock detection if given.
export const joinBackward: Command = (state, dispatch, view) => {
  let $cursor = atBlockStart(state, view)
  if (!$cursor) return false

  let $cut = findCutBefore($cursor)

  // If there is no node before this, try to lift
  if (!$cut) {
    let range = $cursor.blockRange(), target = range && liftTarget(range)
    if (target == null) return false
    if (dispatch) dispatch(state.tr.lift(range!, target).scrollIntoView())
    return true
  }

  let before = $cut.nodeBefore!
  // Apply the joining algorithm
  if (deleteBarrier(state, $cut, dispatch, -1)) return true

  // If the node below has no content and the node above is
  // selectable, delete the node below and select the one above.
  if ($cursor.parent.content.size == 0 &&
      (textblockAt(before, "end") || NodeSelection.isSelectable(before))) {
    for (let depth = $cursor.depth;; depth--) {
      let delStep = replaceStep(state.doc, $cursor.before(depth), $cursor.after(depth), Slice.empty)
      if (delStep && (delStep as ReplaceStep).slice.size < (delStep as ReplaceStep).to - (delStep as ReplaceStep).from) {
        if (dispatch) {
          let tr = state.tr.step(delStep)
          tr.setSelection(textblockAt(before, "end")
            ? Selection.findFrom(tr.doc.resolve(tr.mapping.map($cut.pos, -1)), -1)!
            : NodeSelection.create(tr.doc, $cut.pos - before.nodeSize))
          dispatch(tr.scrollIntoView())
        }
        return true
      }
      if (depth == 1 || $cursor.node(depth - 1).childCount > 1) break
    }
  }

  // If the node before is an atom, delete it
  if (before.isAtom && $cut.depth == $cursor.depth - 1) {
    if (dispatch) dispatch(state.tr.delete($cut.pos - before.nodeSize, $cut.pos).scrollIntoView())
    return true
  }

  return false
}

/// A more limited form of [`joinBackward`](#commands.joinBackward)
/// that only tries to join the current textblock to the one before
/// it, if the cursor is at the start of a textblock.
export const joinTextblockBackward: Command = (state, dispatch, view) => {
  let $cursor = atBlockStart(state, view)
  if (!$cursor) return false
  let $cut = findCutBefore($cursor)
  return $cut ? joinTextblocksAround(state, $cut, dispatch) : false
}

/// A more limited form of [`joinForward`](#commands.joinForward)
/// that only tries to join the current textblock to the one after
/// it, if the cursor is at the end of a textblock.
export const joinTextblockForward: Command = (state, dispatch, view) => {
  let $cursor = atBlockEnd(state, view)
  if (!$cursor) return false
  let $cut = findCutAfter($cursor)
  return $cut ? joinTextblocksAround(state, $cut, dispatch) : false
}

function joinTextblocksAround(state: EditorState, $cut: ResolvedPos, dispatch?: (tr: Transaction) => void) {
  let before = $cut.nodeBefore!, beforeText = before, beforePos = $cut.pos - 1
  for (; !beforeText.isTextblock; beforePos--) {
    if (beforeText.type.spec.isolating) return false
    let child = beforeText.lastChild
    if (!child) return false
    beforeText = child
  }
  let after = $cut.nodeAfter!, afterText = after, afterPos = $cut.pos + 1
  for (; !afterText.isTextblock; afterPos++) {
    if (afterText.type.spec.isolating) return false
    let child = afterText.firstChild
    if (!child) return false
    afterText = child
  }
  let step = replaceStep(state.doc, beforePos, afterPos, Slice.empty) as ReplaceStep | null
  if (!step || step.from != beforePos ||
      step instanceof ReplaceStep && step.slice.size >= afterPos - beforePos) return false
  if (dispatch) {
    let tr = state.tr.step(step)
    tr.setSelection(TextSelection.create(tr.doc, beforePos))
    dispatch(tr.scrollIntoView())
  }
  return true

}

function textblockAt(node: Node, side: "start" | "end", only = false) {
  for (let scan: Node | null = node; scan; scan = (side == "start" ? scan.firstChild : scan.lastChild)) {
    if (scan.isTextblock) return true
    if (only && scan.childCount != 1) return false
  }
  return false
}

/// When the selection is empty and at the start of a textblock, select
/// the node before that textblock, if possible. This is intended to be
/// bound to keys like backspace, after
/// [`joinBackward`](#commands.joinBackward) or other deleting
/// commands, as a fall-back behavior when the schema doesn't allow
/// deletion at the selected point.
export const selectNodeBackward: Command = (state, dispatch, view) => {
  let {$head, empty} = state.selection, $cut: ResolvedPos | null = $head
  if (!empty) return false

  if ($head.parent.isTextblock) {
    if (view ? !view.endOfTextblock("backward", state) : $head.parentOffset > 0) return false
    $cut = findCutBefore($head)
  }
  let node = $cut && $cut.nodeBefore
  if (!node || !NodeSelection.isSelectable(node)) return false
  if (dispatch)
    dispatch(state.tr.setSelection(NodeSelection.create(state.doc, $cut!.pos - node.nodeSize)).scrollIntoView())
  return true
}

function findCutBefore($pos: ResolvedPos): ResolvedPos | null {
  if (!$pos.parent.type.spec.isolating) for (let i = $pos.depth - 1; i >= 0; i--) {
    if ($pos.index(i) > 0) return $pos.doc.resolve($pos.before(i + 1))
    if ($pos.node(i).type.spec.isolating) break
  }
  return null
}

function atBlockEnd(state: EditorState, view?: EditorView): ResolvedPos | null {
  let {$cursor} = state.selection as TextSelection
  if (!$cursor || (view ? !view.endOfTextblock("forward", state)
                        : $cursor.parentOffset < $cursor.parent.content.size))
    return null
  return $cursor
}

/// If the selection is empty and the cursor is at the end of a
/// textblock, try to reduce or remove the boundary between that block
/// and the one after it, either by joining them or by moving the other
/// block closer to this one in the tree structure. Will use the view
/// for accurate start-of-textblock detection if given.
export const joinForward: Command = (state, dispatch, view) => {
  let $cursor = atBlockEnd(state, view)
  if (!$cursor) return false

  let $cut = findCutAfter($cursor)
  // If there is no node after this, there's nothing to do
  if (!$cut) return false

  let after = $cut.nodeAfter!
  // Try the joining algorithm
  if (deleteBarrier(state, $cut, dispatch, 1)) return true

  // If the node above has no content and the node below is
  // selectable, delete the node above and select the one below.
  if ($cursor.parent.content.size == 0 &&
      (textblockAt(after, "start") || NodeSelection.isSelectable(after))) {
    let delStep = replaceStep(state.doc, $cursor.before(), $cursor.after(), Slice.empty)
    if (delStep && (delStep as ReplaceStep).slice.size < (delStep as ReplaceStep).to - (delStep as ReplaceStep).from) {
      if (dispatch) {
        let tr = state.tr.step(delStep)
        tr.setSelection(textblockAt(after, "start") ? Selection.findFrom(tr.doc.resolve(tr.mapping.map($cut.pos)), 1)!
                        : NodeSelection.create(tr.doc, tr.mapping.map($cut.pos)))
        dispatch(tr.scrollIntoView())
      }
      return true
    }
  }

  // If the next node is an atom, delete it
  if (after.isAtom && $cut.depth == $cursor.depth - 1) {
    if (dispatch) dispatch(state.tr.delete($cut.pos, $cut.pos + after.nodeSize).scrollIntoView())
    return true
  }

  return false
}

/// When the selection is empty and at the end of a textblock, select
/// the node coming after that textblock, if possible. This is intended
/// to be bound to keys like delete, after
/// [`joinForward`](#commands.joinForward) and similar deleting
/// commands, to provide a fall-back behavior when the schema doesn't
/// allow deletion at the selected point.
export const selectNodeForward: Command = (state, dispatch, view) => {
  let {$head, empty} = state.selection, $cut: ResolvedPos | null = $head
  if (!empty) return false
  if ($head.parent.isTextblock) {
    if (view ? !view.endOfTextblock("forward", state) : $head.parentOffset < $head.parent.content.size)
      return false
    $cut = findCutAfter($head)
  }
  let node = $cut && $cut.nodeAfter
  if (!node || !NodeSelection.isSelectable(node)) return false
  if (dispatch)
    dispatch(state.tr.setSelection(NodeSelection.create(state.doc, $cut!.pos)).scrollIntoView())
  return true
}

function findCutAfter($pos: ResolvedPos) {
  if (!$pos.parent.type.spec.isolating) for (let i = $pos.depth - 1; i >= 0; i--) {
    let parent = $pos.node(i)
    if ($pos.index(i) + 1 < parent.childCount) return $pos.doc.resolve($pos.after(i + 1))
    if (parent.type.spec.isolating) break
  }
  return null
}

/// Join the selected block or, if there is a text selection, the
/// closest ancestor block of the selection that can be joined, with
/// the sibling above it.
export const joinUp: Command = (state, dispatch) => {
  let sel = state.selection, nodeSel = sel instanceof NodeSelection, point
  if (nodeSel) {
    if ((sel as NodeSelection).node.isTextblock || !canJoin(state.doc, sel.from)) return false
    point = sel.from
  } else {
    point = joinPoint(state.doc, sel.from, -1)
    if (point == null) return false
  }
  if (dispatch) {
    let tr = state.tr.join(point)
    if (nodeSel) tr.setSelection(NodeSelection.create(tr.doc, point - state.doc.resolve(point).nodeBefore!.nodeSize))
    dispatch(tr.scrollIntoView())
  }
  return true
}

/// Join the selected block, or the closest ancestor of the selection
/// that can be joined, with the sibling after it.
export const joinDown: Command = (state, dispatch) => {
  let sel = state.selection, point
  if (sel instanceof NodeSelection) {
    if (sel.node.isTextblock || !canJoin(state.doc, sel.to)) return false
    point = sel.to
  } else {
    point = joinPoint(state.doc, sel.to, 1)
    if (point == null) return false
  }
  if (dispatch)
    dispatch(state.tr.join(point).scrollIntoView())
  return true
}

/// Lift the selected block, or the closest ancestor block of the
/// selection that can be lifted, out of its parent node.
export const lift: Command = (state, dispatch) => {
  let {$from, $to} = state.selection
  let range = $from.blockRange($to), target = range && liftTarget(range)
  if (target == null) return false
  if (dispatch) dispatch(state.tr.lift(range!, target).scrollIntoView())
  return true
}

/// If the selection is in a node whose type has a truthy
/// [`code`](#model.NodeSpec.code) property in its spec, replace the
/// selection with a newline character.
export const newlineInCode: Command = (state, dispatch) => {
  let {$head, $anchor} = state.selection
  if (!$head.parent.type.spec.code || !$head.sameParent($anchor)) return false
  if (dispatch) dispatch(state.tr.insertText("\n").scrollIntoView())
  return true
}

function defaultBlockAt(match: ContentMatch) {
  for (let i = 0; i < match.edgeCount; i++) {
    let {type} = match.edge(i)
    if (type.isTextblock && !type.hasRequiredAttrs()) return type
  }
  return null
}

/// When the selection is in a node with a truthy
/// [`code`](#model.NodeSpec.code) property in its spec, create a
/// default block after the code block, and move the cursor there.
export const exitCode: Command = (state, dispatch) => {
  let {$head, $anchor} = state.selection
  if (!$head.parent.type.spec.code || !$head.sameParent($anchor)) return false
  let above = $head.node(-1), after = $head.indexAfter(-1), type = defaultBlockAt(above.contentMatchAt(after))
  if (!type || !above.canReplaceWith(after, after, type)) return false
  if (dispatch) {
    let pos = $head.after(), tr = state.tr.replaceWith(pos, pos, type.createAndFill()!)
    tr.setSelection(Selection.near(tr.doc.resolve(pos), 1))
    dispatch(tr.scrollIntoView())
  }
  return true
}

/// If a block node is selected, create an empty paragraph before (if
/// it is its parent's first child) or after it.
export const createParagraphNear: Command = (state, dispatch) => {
  let sel = state.selection, {$from, $to} = sel
  if (sel instanceof AllSelection || $from.parent.inlineContent || $to.parent.inlineContent) return false
  let type = defaultBlockAt($to.parent.contentMatchAt($to.indexAfter()))
  if (!type || !type.isTextblock) return false
  if (dispatch) {
    let side = (!$from.parentOffset && $to.index() < $to.parent.childCount ? $from : $to).pos
    let tr = state.tr.insert(side, type.createAndFill()!)
    tr.setSelection(TextSelection.create(tr.doc, side + 1))
    dispatch(tr.scrollIntoView())
  }
  return true
}

/// If the cursor is in an empty textblock that can be lifted, lift the
/// block.
export const liftEmptyBlock: Command = (state, dispatch) => {
  let {$cursor} = state.selection as TextSelection
  if (!$cursor || $cursor.parent.content.size) return false
  if ($cursor.depth > 1 && $cursor.after() != $cursor.end(-1)) {
    let before = $cursor.before()
    if (canSplit(state.doc, before)) {
      if (dispatch) dispatch(state.tr.split(before).scrollIntoView())
      return true
    }
  }
  let range = $cursor.blockRange(), target = range && liftTarget(range)
  if (target == null) return false
  if (dispatch) dispatch(state.tr.lift(range!, target).scrollIntoView())
  return true
}

/// Create a variant of [`splitBlock`](#commands.splitBlock) that uses
/// a custom function to determine the type of the newly split off block.
export function splitBlockAs(
  splitNode?: (node: Node, atEnd: boolean, $from: ResolvedPos) => {type: NodeType, attrs?: Attrs} | null
): Command {
  return (state, dispatch) => {
    let {$from, $to} = state.selection
    if (state.selection instanceof NodeSelection && state.selection.node.isBlock) {
      if (!$from.parentOffset || !canSplit(state.doc, $from.pos)) return false
      if (dispatch) dispatch(state.tr.split($from.pos).scrollIntoView())
      return true
    }

    if (!$from.depth) return false
    let types: (null | {type: NodeType, attrs?: Attrs | null})[] = []
    let splitDepth, deflt, atEnd = false, atStart = false
    for (let d = $from.depth;; d--) {
      let node = $from.node(d)
      if (node.isBlock) {
        atEnd = $from.end(d) == $from.pos + ($from.depth - d)
        atStart = $from.start(d) == $from.pos - ($from.depth - d)
        deflt = defaultBlockAt($from.node(d - 1).contentMatchAt($from.indexAfter(d - 1)))
        let splitType = splitNode && splitNode($to.parent, atEnd, $from)
        types.unshift(splitType || (atEnd && deflt ? {type: deflt} : null))
        splitDepth = d
        break
      } else {
        if (d == 1) return false
        types.unshift(null)
      }
    }

    let tr = state.tr
    if (state.selection instanceof TextSelection || state.selection instanceof AllSelection) tr.deleteSelection()
    let splitPos = tr.mapping.map($from.pos)
    let can = canSplit(tr.doc, splitPos, types.length, types)
    if (!can) {
      types[0] = deflt ? {type: deflt} : null
      can = canSplit(tr.doc, splitPos, types.length, types)
    }
    tr.split(splitPos, types.length, types)
    if (!atEnd && atStart && $from.node(splitDepth).type != deflt) {
      let first = tr.mapping.map($from.before(splitDepth)), $first = tr.doc.resolve(first)
      if (deflt && $from.node(splitDepth - 1).canReplaceWith($first.index(), $first.index() + 1, deflt))
        tr.setNodeMarkup(tr.mapping.map($from.before(splitDepth)), deflt)
    }
    if (dispatch) dispatch(tr.scrollIntoView())
    return true
  }
}

/// Split the parent block of the selection. If the selection is a text
/// selection, also delete its content.
export const splitBlock: Command = splitBlockAs()

/// Acts like [`splitBlock`](#commands.splitBlock), but without
/// resetting the set of active marks at the cursor.
export const splitBlockKeepMarks: Command = (state, dispatch) => {
  return splitBlock(state, dispatch && (tr => {
    let marks = state.storedMarks || (state.selection.$to.parentOffset && state.selection.$from.marks())
    if (marks) tr.ensureMarks(marks)
    dispatch(tr)
  }))
}

/// Move the selection to the node wrapping the current selection, if
/// any. (Will not select the document node.)
export const selectParentNode: Command = (state, dispatch) => {
  let {$from, to} = state.selection, pos
  let same = $from.sharedDepth(to)
  if (same == 0) return false
  pos = $from.before(same)
  if (dispatch) dispatch(state.tr.setSelection(NodeSelection.create(state.doc, pos)))
  return true
}

/// Select the whole document.
export const selectAll: Command = (state, dispatch) => {
  if (dispatch) dispatch(state.tr.setSelection(new AllSelection(state.doc)))
  return true
}

function joinMaybeClear(state: EditorState, $pos: ResolvedPos, dispatch: ((tr: Transaction) => void) | undefined) {
  let before = $pos.nodeBefore, after = $pos.nodeAfter, index = $pos.index()
  if (!before || !after || !before.type.compatibleContent(after.type)) return false
  if (!before.content.size && $pos.parent.canReplace(index - 1, index)) {
    if (dispatch) dispatch(state.tr.delete($pos.pos - before.nodeSize, $pos.pos).scrollIntoView())
    return true
  }
  if (!$pos.parent.canReplace(index, index + 1) || !(after.isTextblock || canJoin(state.doc, $pos.pos)))
    return false
  if (dispatch)
    dispatch(state.tr.join($pos.pos).scrollIntoView())
  return true
}

function deleteBarrier(state: EditorState, $cut: ResolvedPos, dispatch: ((tr: Transaction) => void) | undefined, dir: number) {
  let before = $cut.nodeBefore!, after = $cut.nodeAfter!, conn, match
  let isolated = before.type.spec.isolating || after.type.spec.isolating
  if (!isolated && joinMaybeClear(state, $cut, dispatch)) return true

  let canDelAfter = !isolated && $cut.parent.canReplace($cut.index(), $cut.index() + 1)
  if (canDelAfter &&
      (conn = (match = before.contentMatchAt(before.childCount)).findWrapping(after.type)) &&
      match.matchType(conn[0] || after.type)!.validEnd) {
    if (dispatch) {
      let end = $cut.pos + after.nodeSize, wrap = Fragment.empty
      for (let i = conn.length - 1; i >= 0; i--)
        wrap = Fragment.from(conn[i].create(null, wrap))
      wrap = Fragment.from(before.copy(wrap))
      let tr = state.tr.step(new ReplaceAroundStep($cut.pos - 1, end, $cut.pos, end, new Slice(wrap, 1, 0), conn.length, true))
      let $joinAt = tr.doc.resolve(end + 2 * conn.length)
      if ($joinAt.nodeAfter && $joinAt.nodeAfter.type == before.type &&
          canJoin(tr.doc, $joinAt.pos)) tr.join($joinAt.pos)
      dispatch(tr.scrollIntoView())
    }
    return true
  }

  let selAfter = after.type.spec.isolating || (dir > 0 && isolated) ? null : Selection.findFrom($cut, 1)
  let range = selAfter && selAfter.$from.blockRange(selAfter.$to), target = range && liftTarget(range)
  if (target != null && target >= $cut.depth) {
    if (dispatch) dispatch(state.tr.lift(range!, target).scrollIntoView())
    return true
  }

  if (canDelAfter && textblockAt(after, "start", true) && textblockAt(before, "end")) {
    let at = before, wrap = []
    for (;;) {
      wrap.push(at)
      if (at.isTextblock) break
      at = at.lastChild!
    }
    let afterText = after, afterDepth = 1
    for (; !afterText.isTextblock; afterText = afterText.firstChild!) afterDepth++
    if (at.canReplace(at.childCount, at.childCount, afterText.content)) {
      if (dispatch) {
        let end = Fragment.empty
        for (let i = wrap.length - 1; i >= 0; i--) end = Fragment.from(wrap[i].copy(end))
        let tr = state.tr.step(new ReplaceAroundStep($cut.pos - wrap.length, $cut.pos + after.nodeSize,
                                                     $cut.pos + afterDepth, $cut.pos + after.nodeSize - afterDepth,
                                                     new Slice(end, wrap.length, 0), 0, true))
        dispatch(tr.scrollIntoView())
      }
      return true
    }
  }

  return false
}

function selectTextblockSide(side: number): Command {
  return function(state, dispatch) {
    let sel = state.selection, $pos = side < 0 ? sel.$from : sel.$to
    let depth = $pos.depth
    while ($pos.node(depth).isInline) {
      if (!depth) return false
      depth--
    }
    if (!$pos.node(depth).isTextblock) return false
    if (dispatch)
      dispatch(state.tr.setSelection(TextSelection.create(
        state.doc, side < 0 ? $pos.start(depth) : $pos.end(depth))))
    return true
  }
}

/// Moves the cursor to the start of current text block.
export const selectTextblockStart = selectTextblockSide(-1)

/// Moves the cursor to the end of current text block.
export const selectTextblockEnd = selectTextblockSide(1)

// Parameterized commands

/// Wrap the selection in a node of the given type with the given
/// attributes.
export function wrapIn(nodeType: NodeType, attrs: Attrs | null = null): Command {
  return function(state, dispatch) {
    let {$from, $to} = state.selection
    let range = $from.blockRange($to), wrapping = range && findWrapping(range, nodeType, attrs)
    if (!wrapping) return false
    if (dispatch) dispatch(state.tr.wrap(range!, wrapping).scrollIntoView())
    return true
  }
}

/// Returns a command that tries to set the selected textblocks to the
/// given node type with the given attributes.
export function setBlockType(nodeType: NodeType, attrs: Attrs | null = null): Command {
  return function(state, dispatch) {
    let applicable = false
    for (let i = 0; i < state.selection.ranges.length && !applicable; i++) {
      let {$from: {pos: from}, $to: {pos: to}} = state.selection.ranges[i]
      state.doc.nodesBetween(from, to, (node, pos) => {
        if (applicable) return false
        if (!node.isTextblock || node.hasMarkup(nodeType, attrs)) return
        if (node.type == nodeType) {
          applicable = true
        } else {
          let $pos = state.doc.resolve(pos), index = $pos.index()
          applicable = $pos.parent.canReplaceWith(index, index + 1, nodeType)
        }
      })
    }
    if (!applicable) return false
    if (dispatch) {
      let tr = state.tr
      for (let i = 0; i < state.selection.ranges.length; i++) {
        let {$from: {pos: from}, $to: {pos: to}} = state.selection.ranges[i]
        tr.setBlockType(from, to, nodeType, attrs)
      }
      dispatch(tr.scrollIntoView())
    }
    return true
  }
}

function markApplies(doc: Node, ranges: readonly SelectionRange[], type: MarkType, enterAtoms: boolean) {
  for (let i = 0; i < ranges.length; i++) {
    let {$from, $to} = ranges[i]
    let can = $from.depth == 0 ? doc.inlineContent && doc.type.allowsMarkType(type) : false
    doc.nodesBetween($from.pos, $to.pos, (node, pos) => {
      if (can || !enterAtoms && node.isAtom && node.isInline && pos >= $from.pos && pos + node.nodeSize <= $to.pos)
        return false
      can = node.inlineContent && node.type.allowsMarkType(type)
    })
    if (can) return true
  }
  return false
}

function removeInlineAtoms(ranges: readonly SelectionRange[]): readonly SelectionRange[] {
  let result = []
  for (let i = 0; i < ranges.length; i++) {
    let {$from, $to} = ranges[i]
    $from.doc.nodesBetween($from.pos, $to.pos, (node, pos) => {
      if (node.isAtom && node.content.size && node.isInline && pos >= $from.pos && pos + node.nodeSize <= $to.pos) {
        if (pos + 1 > $from.pos) result.push(new SelectionRange($from, $from.doc.resolve(pos + 1)))
        $from = $from.doc.resolve(pos + 1 + node.content.size)
        return false
      }
    })
    if ($from.pos < $to.pos) result.push(new SelectionRange($from, $to))
  }
  return result
}

/// Create a command function that toggles the given mark with the
/// given attributes. Will return `false` when the current selection
/// doesn't support that mark. This will remove the mark if any marks
/// of that type exist in the selection, or add it otherwise. If the
/// selection is empty, this applies to the [stored
/// marks](#state.EditorState.storedMarks) instead of a range of the
/// document.
export function toggleMark(markType: MarkType, attrs: Attrs | null = null, options?: {
  /// Controls whether, when part of the selected range has the mark
  /// already and part doesn't, the mark is removed (`true`, the
  /// default) or added (`false`).
  removeWhenPresent?: boolean
  /// When set to false, this will prevent the command from acting on
  /// the content of inline nodes marked as
  /// [atoms](#model.NodeSpec.atom) that are completely covered by a
  /// selection range.
  enterInlineAtoms?: boolean
  /// By default, this command doesn't apply to leading and trailing
  /// whitespace in the selection. Set this to `true` to change that.
  includeWhitespace?: boolean
}): Command {
  let removeWhenPresent = (options && options.removeWhenPresent) !== false
  let enterAtoms = (options && options.enterInlineAtoms) !== false
  let dropSpace = !(options && options.includeWhitespace)
  return function(state, dispatch) {
    let {empty, $cursor, ranges} = state.selection as TextSelection
    if ((empty && !$cursor) || !markApplies(state.doc, ranges, markType, enterAtoms)) return false
    if (dispatch) {
      if ($cursor) {
        if (markType.isInSet(state.storedMarks || $cursor.marks()))
          dispatch(state.tr.removeStoredMark(markType))
        else
          dispatch(state.tr.addStoredMark(markType.create(attrs)))
      } else {
        let add, tr = state.tr
        if (!enterAtoms) ranges = removeInlineAtoms(ranges)
        if (removeWhenPresent) {
          add = !ranges.some(r => state.doc.rangeHasMark(r.$from.pos, r.$to.pos, markType))
        } else {
          add = !ranges.every(r => {
            let missing = false
            tr.doc.nodesBetween(r.$from.pos, r.$to.pos, (node, pos, parent) => {
              if (missing) return false
              missing = !markType.isInSet(node.marks) && !!parent && parent.type.allowsMarkType(markType) &&
                !(node.isText && /^\s*$/.test(node.textBetween(Math.max(0, r.$from.pos - pos),
                                                               Math.min(node.nodeSize, r.$to.pos - pos))))
            })
            return !missing
          })
        }
        for (let i = 0; i < ranges.length; i++) {
          let {$from, $to} = ranges[i]
          if (!add) {
            tr.removeMark($from.pos, $to.pos, markType)
          } else {
            let from = $from.pos, to = $to.pos, start = $from.nodeAfter, end = $to.nodeBefore
            let spaceStart = dropSpace && start && start.isText ? /^\s*/.exec(start.text!)![0].length : 0
            let spaceEnd = dropSpace && end && end.isText ? /\s*$/.exec(end.text!)![0].length : 0
            if (from + spaceStart < to) { from += spaceStart; to -= spaceEnd }
            tr.addMark(from, to, markType.create(attrs))
          }
        }
        dispatch(tr.scrollIntoView())
      }
    }
    return true
  }
}

function wrapDispatchForJoin(dispatch: (tr: Transaction) => void, isJoinable: (a: Node, b: Node) => boolean) {
  return (tr: Transaction) => {
    if (!tr.isGeneric) return dispatch(tr)

    let ranges: number[] = []
    for (let i = 0; i < tr.mapping.maps.length; i++) {
      let map = tr.mapping.maps[i]
      for (let j = 0; j < ranges.length; j++)
        ranges[j] = map.map(ranges[j])
      map.forEach((_s, _e, from, to) => ranges.push(from, to))
    }

    // Figure out which joinable points exist inside those ranges,
    // by checking all node boundaries in their parent nodes.
    let joinable = []
    for (let i = 0; i < ranges.length; i += 2) {
      let from = ranges[i], to = ranges[i + 1]
      let $from = tr.doc.resolve(from), depth = $from.sharedDepth(to), parent = $from.node(depth)
      for (let index = $from.indexAfter(depth), pos = $from.after(depth + 1); pos <= to; ++index) {
        let after = parent.maybeChild(index)
        if (!after) break
        if (index && joinable.indexOf(pos) == -1) {
          let before = parent.child(index - 1)
          if (before.type == after.type && isJoinable(before, after))
            joinable.push(pos)
        }
        pos += after.nodeSize
      }
    }
    // Join the joinable points
    joinable.sort((a, b) => a - b)
    for (let i = joinable.length - 1; i >= 0; i--) {
      if (canJoin(tr.doc, joinable[i])) tr.join(joinable[i])
    }
    dispatch(tr)
  }
}

/// Wrap a command so that, when it produces a transform that causes
/// two joinable nodes to end up next to each other, those are joined.
/// Nodes are considered joinable when they are of the same type and
/// when the `isJoinable` predicate returns true for them or, if an
/// array of strings was passed, if their node type name is in that
/// array.
export function autoJoin(
  command: Command,
  isJoinable: ((before: Node, after: Node) => boolean) | readonly string[]
): Command {
  let canJoin = Array.isArray(isJoinable) ? (node: Node) => isJoinable.indexOf(node.type.name) > -1
    : isJoinable as (a: Node, b: Node) => boolean
  return (state, dispatch, view) => command(state, dispatch && wrapDispatchForJoin(dispatch, canJoin), view)
}

/// Combine a number of command functions into a single function (which
/// calls them one by one until one returns true).
export function chainCommands(...commands: readonly Command[]): Command {
  return function(state, dispatch, view) {
    for (let i = 0; i < commands.length; i++)
      if (commands[i](state, dispatch, view)) return true
    return false
  }
}

let backspace = chainCommands(deleteSelection, joinBackward, selectNodeBackward)
let del = chainCommands(deleteSelection, joinForward, selectNodeForward)

/// A basic keymap containing bindings not specific to any schema.
/// Binds the following keys (when multiple commands are listed, they
/// are chained with [`chainCommands`](#commands.chainCommands)):
///
/// * **Enter** to `newlineInCode`, `createParagraphNear`, `liftEmptyBlock`, `splitBlock`
/// * **Mod-Enter** to `exitCode`
/// * **Backspace** and **Mod-Backspace** to `deleteSelection`, `joinBackward`, `selectNodeBackward`
/// * **Delete** and **Mod-Delete** to `deleteSelection`, `joinForward`, `selectNodeForward`
/// * **Mod-Delete** to `deleteSelection`, `joinForward`, `selectNodeForward`
/// * **Mod-a** to `selectAll`
export const pcBaseKeymap: {[key: string]: Command} = {
  "Enter": chainCommands(newlineInCode, createParagraphNear, liftEmptyBlock, splitBlock),
  "Mod-Enter": exitCode,
  "Backspace": backspace,
  "Mod-Backspace": backspace,
  "Shift-Backspace": backspace,
  "Delete": del,
  "Mod-Delete": del,
  "Mod-a": selectAll
}

/// A copy of `pcBaseKeymap` that also binds **Ctrl-h** like Backspace,
/// **Ctrl-d** like Delete, **Alt-Backspace** like Ctrl-Backspace, and
/// **Ctrl-Alt-Backspace**, **Alt-Delete**, and **Alt-d** like
/// Ctrl-Delete.
export const macBaseKeymap: {[key: string]: Command} = {
  "Ctrl-h": pcBaseKeymap["Backspace"],
  "Alt-Backspace": pcBaseKeymap["Mod-Backspace"],
  "Ctrl-d": pcBaseKeymap["Delete"],
  "Ctrl-Alt-Backspace": pcBaseKeymap["Mod-Delete"],
  "Alt-Delete": pcBaseKeymap["Mod-Delete"],
  "Alt-d": pcBaseKeymap["Mod-Delete"],
  "Ctrl-a": selectTextblockStart,
  "Ctrl-e": selectTextblockEnd
}
for (let key in pcBaseKeymap) (macBaseKeymap as any)[key] = pcBaseKeymap[key]

const mac = typeof navigator != "undefined" ? /Mac|iP(hone|[oa]d)/.test(navigator.platform)
          // @ts-ignore
          : typeof os != "undefined" && os.platform ? os.platform() == "darwin" : false

/// Depending on the detected platform, this will hold
/// [`pcBasekeymap`](#commands.pcBaseKeymap) or
/// [`macBaseKeymap`](#commands.macBaseKeymap).
export const baseKeymap: {[key: string]: Command} = mac ? macBaseKeymap : pcBaseKeymap
