353 lines
9.7 KiB
JavaScript
353 lines
9.7 KiB
JavaScript
/* @flow */
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'use strict'
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/*
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An operation also defines the structure of a type. This is why operation and
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structure are used interchangeably here.
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It must be of the type Object. I hope to achieve some performance
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improvements when working on databases that support the json format.
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An operation must have the following properties:
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* encode
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- Encode the structure in a readable format (preferably string- todo)
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* decode (todo)
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- decode structure to json
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* execute
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- Execute the semantics of an operation.
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* requiredOps
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- Operations that are required to execute this operation.
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*/
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module.exports = function (Y/* :any */) {
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var Struct = {
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/* This is the only operation that is actually not a structure, because
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it is not stored in the OS. This is why it _does not_ have an id
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op = {
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target: Id
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}
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*/
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Delete: {
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encode: function (op) {
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return op
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},
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requiredOps: function (op) {
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return [] // [op.target]
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},
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execute: function * (op) {
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return yield* this.deleteOperation(op.target)
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}
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},
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Insert: {
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/* {
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content: any,
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id: Id,
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left: Id,
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origin: Id,
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right: Id,
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parent: Id,
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parentSub: string (optional), // child of Map type
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}
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*/
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encode: function (op/* :Insertion */) /* :Insertion */ {
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// TODO: you could not send the "left" property, then you also have to
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// "op.left = null" in $execute or $decode
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var e/* :any */ = {
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id: op.id,
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left: op.left,
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right: op.right,
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origin: op.origin,
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parent: op.parent,
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struct: op.struct
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}
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if (op.parentSub != null) {
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e.parentSub = op.parentSub
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}
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if (op.opContent != null) {
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e.opContent = op.opContent
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} else {
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e.content = op.content
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}
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return e
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},
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requiredOps: function (op) {
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var ids = []
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if (op.left != null) {
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ids.push(op.left)
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}
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if (op.right != null) {
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ids.push(op.right)
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}
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if (op.origin != null && !Y.utils.compareIds(op.left, op.origin)) {
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ids.push(op.origin)
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}
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// if (op.right == null && op.left == null) {
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ids.push(op.parent)
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if (op.opContent != null) {
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ids.push(op.opContent)
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}
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return ids
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},
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getDistanceToOrigin: function * (op) {
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if (op.left == null) {
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return 0
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} else {
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var d = 0
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var o = yield* this.getOperation(op.left)
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while (!Y.utils.compareIds(op.origin, (o ? o.id : null))) {
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d++
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if (o.left == null) {
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break
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} else {
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o = yield* this.getOperation(o.left)
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}
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}
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return d
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}
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},
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/*
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# $this has to find a unique position between origin and the next known character
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# case 1: $origin equals $o.origin: the $creator parameter decides if left or right
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# let $OL= [o1,o2,o3,o4], whereby $this is to be inserted between o1 and o4
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# o2,o3 and o4 origin is 1 (the position of o2)
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# there is the case that $this.creator < o2.creator, but o3.creator < $this.creator
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# then o2 knows o3. Since on another client $OL could be [o1,o3,o4] the problem is complex
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# therefore $this would be always to the right of o3
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# case 2: $origin < $o.origin
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# if current $this insert_position > $o origin: $this ins
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# else $insert_position will not change
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# (maybe we encounter case 1 later, then this will be to the right of $o)
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# case 3: $origin > $o.origin
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# $this insert_position is to the left of $o (forever!)
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*/
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execute: function *(op) {
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var i // loop counter
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var distanceToOrigin = i = yield* Struct.Insert.getDistanceToOrigin.call(this, op) // most cases: 0 (starts from 0)
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var o
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var parent
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var start
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// find o. o is the first conflicting operation
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if (op.left != null) {
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o = yield* this.getOperation(op.left)
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o = (o.right == null) ? null : yield* this.getOperation(o.right)
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} else { // left == null
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parent = yield* this.getOperation(op.parent)
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let startId = op.parentSub ? parent.map[op.parentSub] : parent.start
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start = startId == null ? null : yield* this.getOperation(startId)
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o = start
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}
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// handle conflicts
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while (true) {
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if (o != null && !Y.utils.compareIds(o.id, op.right)) {
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var oOriginDistance = yield* Struct.Insert.getDistanceToOrigin.call(this, o)
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if (oOriginDistance === i) {
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// case 1
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if (o.id[0] < op.id[0]) {
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op.left = o.id
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distanceToOrigin = i + 1
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}
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} else if (oOriginDistance < i) {
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// case 2
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if (i - distanceToOrigin <= oOriginDistance) {
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op.left = o.id
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distanceToOrigin = i + 1
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}
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} else {
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break
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}
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i++
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if (o.right != null) {
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o = yield* this.getOperation(o.right)
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} else {
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o = null
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}
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} else {
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break
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}
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}
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// reconnect..
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var left = null
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var right = null
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if (parent == null) {
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parent = yield* this.getOperation(op.parent)
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}
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// reconnect left and set right of op
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if (op.left != null) {
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left = yield* this.getOperation(op.left)
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op.right = left.right
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left.right = op.id
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yield* this.setOperation(left)
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} else {
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op.right = op.parentSub ? parent.map[op.parentSub] || null : parent.start
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}
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// reconnect right
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if (op.right != null) {
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right = yield* this.getOperation(op.right)
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right.left = op.id
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// if right exists, and it is supposed to be gc'd. Remove it from the gc
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if (right.gc != null) {
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this.store.removeFromGarbageCollector(right)
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}
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yield* this.setOperation(right)
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}
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// update parents .map/start/end properties
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if (op.parentSub != null) {
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if (left == null) {
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parent.map[op.parentSub] = op.id
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yield* this.setOperation(parent)
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}
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// is a child of a map struct.
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// Then also make sure that only the most left element is not deleted
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if (op.right != null) {
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yield* this.deleteOperation(op.right, true)
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}
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if (op.left != null) {
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yield* this.deleteOperation(op.id, true)
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}
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} else {
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if (right == null || left == null) {
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if (right == null) {
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parent.end = op.id
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}
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if (left == null) {
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parent.start = op.id
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}
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yield* this.setOperation(parent)
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}
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}
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}
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},
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List: {
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/*
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{
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start: null,
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end: null,
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struct: "List",
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type: "",
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id: this.os.getNextOpId()
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}
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*/
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create: function (id) {
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return {
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start: null,
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end: null,
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struct: 'List',
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id: id
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}
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},
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encode: function (op) {
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return {
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struct: 'List',
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id: op.id,
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type: op.type
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}
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},
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requiredOps: function () {
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/*
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var ids = []
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if (op.start != null) {
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ids.push(op.start)
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}
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if (op.end != null){
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ids.push(op.end)
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}
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return ids
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*/
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return []
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},
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execute: function * (op) {
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op.start = null
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op.end = null
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},
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ref: function * (op, pos) {
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if (op.start == null) {
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return null
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}
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var res = null
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var o = yield* this.getOperation(op.start)
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while (true) {
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if (!o.deleted) {
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res = o
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pos--
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}
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if (pos >= 0 && o.right != null) {
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o = yield* this.getOperation(o.right)
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} else {
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break
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}
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}
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return res
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},
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map: function * (o, f) {
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o = o.start
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var res = []
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while (o != null) { // TODO: change to != (at least some convention)
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var operation = yield* this.getOperation(o)
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if (!operation.deleted) {
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res.push(f(operation))
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}
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o = operation.right
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}
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return res
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}
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},
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Map: {
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/*
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{
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map: {},
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struct: "Map",
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type: "",
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id: this.os.getNextOpId()
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}
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*/
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create: function (id) {
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return {
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id: id,
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map: {},
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struct: 'Map'
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}
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},
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encode: function (op) {
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return {
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struct: 'Map',
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type: op.type,
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id: op.id,
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map: {} // overwrite map!!
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}
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},
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requiredOps: function () {
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return []
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},
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execute: function * () {},
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/*
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Get a property by name
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*/
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get: function * (op, name) {
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var oid = op.map[name]
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if (oid != null) {
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var res = yield* this.getOperation(oid)
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if (res == null || res.deleted) {
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return void 0
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} else if (res.opContent == null) {
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return res.content
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} else {
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return yield* this.getType(res.opContent)
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}
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}
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}
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}
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}
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Y.Struct = Struct
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}
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