overleaf/libraries/overleaf-editor-core/lib/operation/index.js

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'use strict'
const _ = require('lodash')
const assert = require('check-types').assert
const EditOperationTransformer = require('./edit_operation_transformer')
// Dependencies are loaded at the bottom of the file to mitigate circular
// dependency
let NoOperation = null
let AddFileOperation = null
let MoveFileOperation = null
let EditFileOperation = null
let SetFileMetadataOperation = null
/**
* @typedef {import("../types").BlobStore} BlobStore
* @typedef {import("../snapshot")} Snapshot
*/
/**
* An `Operation` changes a `Snapshot` when it is applied. See the
* {@tutorial OT} tutorial for background.
*/
class Operation {
/**
* Deserialize an Operation.
*
* @param {Object} raw
* @return {Operation} one of the subclasses
*/
static fromRaw(raw) {
if ('file' in raw) {
return AddFileOperation.fromRaw(raw)
}
if ('textOperation' in raw || 'commentId' in raw) {
return EditFileOperation.fromRaw(raw)
}
if ('newPathname' in raw) {
return new MoveFileOperation(raw.pathname, raw.newPathname)
}
if ('metadata' in raw) {
return new SetFileMetadataOperation(raw.pathname, raw.metadata)
}
if (_.isEmpty(raw)) {
return new NoOperation()
}
throw new Error('invalid raw operation ' + JSON.stringify(raw))
}
/**
* Serialize an Operation.
*
* @return {Object}
*/
toRaw() {
return {}
}
/**
* Whether this operation does nothing when applied.
*
* @return {Boolean}
*/
isNoOp() {
return false
}
/**
* If this Operation references blob hashes, add them to the given Set.
*
* @param {Set.<String>} blobHashes
*/
findBlobHashes(blobHashes) {}
/**
* If this operation references any files, load the files.
*
* @param {string} kind see {File#load}
* @param {BlobStore} blobStore
* @return {Promise<void>}
*/
async loadFiles(kind, blobStore) {}
/**
* Return a version of this operation that is suitable for long term storage.
* In most cases, we just need to convert the operation to raw form, but if
* the operation involves File objects, we may need to store their content.
*
* @param {BlobStore} blobStore
* @return {Promise.<Object>}
*/
async store(blobStore) {
return this.toRaw()
}
/**
* Apply this Operation to a snapshot.
*
* The snapshot is modified in place.
*
* @param {Snapshot} snapshot
*/
applyTo(snapshot) {
assert.object(snapshot, 'bad snapshot')
}
/**
* Whether this operation can be composed with another operation to produce a
* single operation of the same type as this one, while keeping the composed
* operation small and logical enough to be used in the undo stack.
*
* @param {Operation} other
* @return {Boolean}
*/
canBeComposedWithForUndo(other) {
return false
}
/**
* Whether this operation can be composed with another operation to produce a
* single operation of the same type as this one.
*
* TODO Moves can be composed. For example, if you rename a to b and then decide
* shortly after that actually you want to call it c, we could compose the two
* to get a -> c). Edits can also be composed --- see rules in TextOperation.
* We also need to consider the Change --- we will need to consider both time
* and author(s) when composing changes. I guess that AddFile can also be
* composed in some cases --- if you upload a file and then decide it was the
* wrong one and upload a new one, we could drop the one in the middle, but
* that seems like a pretty rare case.
*
* @param {Operation} other
* @return {Boolean}
*/
canBeComposedWith(other) {
return false
}
/**
* Compose this operation with another operation to produce a single operation
* of the same type as this one.
*
* @param {Operation} other
* @return {Operation}
*/
compose(other) {
throw new Error('not implemented')
}
/**
* Transform takes two operations A and B that happened concurrently and
* produces two operations A' and B' (in an array) such that
* `apply(apply(S, A), B') = apply(apply(S, B), A')`.
*
* That is, if one client applies A and then B', they get the same result as
* another client who applies B and then A'.
*
* @param {Operation} a
* @param {Operation} b
* @return {Operation[]} operations `[a', b']`
*/
static transform(a, b) {
if (a.isNoOp() || b.isNoOp()) return [a, b]
function transpose(transformer) {
return transformer(b, a).reverse()
}
const bIsAddFile = b instanceof AddFileOperation
const bIsEditFile = b instanceof EditFileOperation
const bIsMoveFile = b instanceof MoveFileOperation
const bIsSetFileMetadata = b instanceof SetFileMetadataOperation
if (a instanceof AddFileOperation) {
if (bIsAddFile) return transformAddFileAddFile(a, b)
if (bIsMoveFile) return transformAddFileMoveFile(a, b)
if (bIsEditFile) return transformAddFileEditFile(a, b)
if (bIsSetFileMetadata) return transformAddFileSetFileMetadata(a, b)
throw new Error('bad op b')
}
if (a instanceof MoveFileOperation) {
if (bIsAddFile) return transpose(transformAddFileMoveFile)
if (bIsMoveFile) return transformMoveFileMoveFile(a, b)
if (bIsEditFile) return transformMoveFileEditFile(a, b)
if (bIsSetFileMetadata) return transformMoveFileSetFileMetadata(a, b)
throw new Error('bad op b')
}
if (a instanceof EditFileOperation) {
if (bIsAddFile) return transpose(transformAddFileEditFile)
if (bIsMoveFile) return transpose(transformMoveFileEditFile)
if (bIsEditFile) return transformEditFileEditFile(a, b)
if (bIsSetFileMetadata) return transformEditFileSetFileMetadata(a, b)
throw new Error('bad op b')
}
if (a instanceof SetFileMetadataOperation) {
if (bIsAddFile) return transpose(transformAddFileSetFileMetadata)
if (bIsMoveFile) return transpose(transformMoveFileSetFileMetadata)
if (bIsEditFile) return transpose(transformEditFileSetFileMetadata)
if (bIsSetFileMetadata) return transformSetFileMetadatas(a, b)
throw new Error('bad op b')
}
throw new Error('bad op a')
}
/**
* Transform each operation in `a` by each operation in `b` and save the primed
* operations in place.
*
* @param {Array.<Operation>} as - modified in place
* @param {Array.<Operation>} bs - modified in place
*/
static transformMultiple(as, bs) {
for (let i = 0; i < as.length; ++i) {
for (let j = 0; j < bs.length; ++j) {
const primes = Operation.transform(as[i], bs[j])
as[i] = primes[0]
bs[j] = primes[1]
}
}
}
static addFile(pathname, file) {
return new AddFileOperation(pathname, file)
}
static editFile(pathname, editOperation) {
return new EditFileOperation(pathname, editOperation)
}
static moveFile(pathname, newPathname) {
return new MoveFileOperation(pathname, newPathname)
}
static removeFile(pathname) {
return new MoveFileOperation(pathname, '')
}
static setFileMetadata(pathname, metadata) {
return new SetFileMetadataOperation(pathname, metadata)
}
}
//
// Transform
//
// The way to read these transform functions is that
// 1. return_value[0] is the op to be applied after arguments[1], and
// 2. return_value[1] is the op to be applied after arguments[0],
// in order to arrive at the same project state.
//
function transformAddFileAddFile(add1, add2) {
if (add1.getPathname() === add2.getPathname()) {
return [Operation.NO_OP, add2] // add2 wins
}
return [add1, add2]
}
function transformAddFileMoveFile(add, move) {
function relocateAddFile() {
return new AddFileOperation(move.getNewPathname(), add.getFile().clone())
}
if (add.getPathname() === move.getPathname()) {
if (move.isRemoveFile()) {
return [add, Operation.NO_OP]
}
return [
relocateAddFile(),
new MoveFileOperation(add.getPathname(), move.getNewPathname()),
]
}
if (add.getPathname() === move.getNewPathname()) {
return [relocateAddFile(), new MoveFileOperation(move.getPathname(), '')]
}
return [add, move]
}
function transformAddFileEditFile(add, edit) {
if (add.getPathname() === edit.getPathname()) {
return [add, Operation.NO_OP] // the add wins
}
return [add, edit]
}
function transformAddFileSetFileMetadata(add, set) {
if (add.getPathname() === set.getPathname()) {
const newFile = add.getFile().clone()
newFile.setMetadata(set.getMetadata())
return [new AddFileOperation(add.getPathname(), newFile), set]
}
return [add, set]
}
//
// This is one of the trickier ones. There are 15 possible equivalence
// relationships between our four variables:
//
// path1, newPath1, path2, newPath2 --- "same move" (all equal)
//
// path1, newPath1, path2 | newPath2 --- "no-ops" (1)
// path1, newPath1, newPath2 | path2 --- "no-ops" (1)
// path1, path2, newPath2 | newPath1 --- "no-ops" (2)
// newPath1, path2, newPath2 | path1 --- "no-ops" (2)
//
// path1, newPath1 | path2, newPath2 --- "no-ops" (1 and 2)
// path1, path2 | newPath1, newPath2 --- "same move"
// path1, newPath2 | newPath1, path2 --- "opposite moves"
//
// path1, newPath1 | path2 | newPath2 --- "no-ops" (1)
// path1, path2 | newPath1 | newPath2 --- "divergent moves"
// path1, newPath2 | newPath1 | path2 --- "transitive move"
// newPath1, path2 | path1 | newPath2 --- "transitive move"
// newPath1, newPath2 | path1 | path2 --- "convergent move"
// path2, newPath2 | path1 | newPath1 --- "no-ops" (2)
//
// path1 | newPath1 | path2 | newPath2 --- "no conflict"
//
function transformMoveFileMoveFile(move1, move2) {
const path1 = move1.getPathname()
const path2 = move2.getPathname()
const newPath1 = move1.getNewPathname()
const newPath2 = move2.getNewPathname()
// the same move
if (path1 === path2 && newPath1 === newPath2) {
return [Operation.NO_OP, Operation.NO_OP]
}
// no-ops
if (path1 === newPath1 && path2 === newPath2) {
return [Operation.NO_OP, Operation.NO_OP]
}
if (path1 === newPath1) {
return [Operation.NO_OP, move2]
}
if (path2 === newPath2) {
return [move1, Operation.NO_OP]
}
// opposite moves (foo -> bar, bar -> foo)
if (path1 === newPath2 && path2 === newPath1) {
// We can't handle this very well: if we wanted move2 (say) to win, move2'
// would have to be addFile(foo) with the content of bar, but we don't have
// the content of bar available here. So, we just destroy both files.
return [Operation.removeFile(path1), Operation.removeFile(path2)]
}
// divergent moves (foo -> bar, foo -> baz); convention: move2 wins
if (path1 === path2 && newPath1 !== newPath2) {
return [Operation.NO_OP, Operation.moveFile(newPath1, newPath2)]
}
// convergent move (foo -> baz, bar -> baz); convention: move2 wins
if (newPath1 === newPath2 && path1 !== path2) {
return [Operation.removeFile(path1), move2]
}
// transitive move:
// 1: foo -> baz, 2: bar -> foo (result: bar -> baz) or
// 1: foo -> bar, 2: bar -> baz (result: foo -> baz)
if (path1 === newPath2 && newPath1 !== path2) {
return [
Operation.moveFile(newPath2, newPath1),
Operation.moveFile(path2, newPath1),
]
}
if (newPath1 === path2 && path1 !== newPath2) {
return [
Operation.moveFile(path1, newPath2),
Operation.moveFile(newPath1, newPath2),
]
}
// no conflict
return [move1, move2]
}
function transformMoveFileEditFile(move, edit) {
if (move.getPathname() === edit.getPathname()) {
if (move.isRemoveFile()) {
// let the remove win
return [move, Operation.NO_OP]
}
return [
move,
Operation.editFile(move.getNewPathname(), edit.getOperation()),
]
}
if (move.getNewPathname() === edit.getPathname()) {
// let the move win
return [move, Operation.NO_OP]
}
return [move, edit]
}
function transformMoveFileSetFileMetadata(move, set) {
if (move.getPathname() === set.getPathname()) {
return [
move,
Operation.setFileMetadata(move.getNewPathname(), set.getMetadata()),
]
}
// A: mv foo -> bar
// B: set bar.x
//
// A': mv foo -> bar
// B': nothing
if (move.getNewPathname() === set.getPathname()) {
return [move, Operation.NO_OP] // let the move win
}
return [move, set]
}
function transformEditFileEditFile(edit1, edit2) {
if (edit1.getPathname() === edit2.getPathname()) {
const primeOps = EditOperationTransformer.transform(
edit1.getOperation(),
edit2.getOperation()
)
return [
Operation.editFile(edit1.getPathname(), primeOps[0]),
Operation.editFile(edit2.getPathname(), primeOps[1]),
]
}
return [edit1, edit2]
}
function transformEditFileSetFileMetadata(edit, set) {
// There is no conflict.
return [edit, set]
}
function transformSetFileMetadatas(set1, set2) {
if (set1.getPathname() === set2.getPathname()) {
return [Operation.NO_OP, set2] // set2 wins
}
return [set1, set2]
}
module.exports = Operation
// Work around circular import
NoOperation = require('./no_operation')
AddFileOperation = require('./add_file_operation')
MoveFileOperation = require('./move_file_operation')
EditFileOperation = require('./edit_file_operation')
SetFileMetadataOperation = require('./set_file_metadata_operation')
Operation.NO_OP = new NoOperation()