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* The coLAB project
* Copyright (C) 2021-2023 AlbaSim, MEI, HEIG-VD, HES-SO
*
* Licensed under the MIT License
*/
import { Change, MicroChange } from 'colab-rest-client';
import * as Diff from 'diff';
import { removeAllItems } from './helper';
import { getLogger } from './logger';
const logger = getLogger('LiveChanges');
//logger.setLevel(3);
//export const mapChangesByObject = (changes: Change[]): ChangeState => {
// return changes.reduce<ChangeState>(
// (acc, cur) => {
// if (cur.atClass != null && cur.atId != null) {
// acc[cur.atClass] = acc[cur.atClass] || {};
// const classState = acc[cur.atClass]!;
//
// classState[cur.atId] = classState[cur.atId] || {
// status: 'UNSET',
// changes: []
// }
// const chState = classState[cur.atId]!
//
// chState.changes.push(cur);
// }
// return acc;
// }, {});
//};
/**
* compute µchanges between previous and current.
* µChange indexes correspond to those of the previous version.
*/
export const getMicroChange = (previous: string, current: string): MicroChange[] => {
logger.trace('Previous:', previous);
logger.trace('New:', current);
const diff = Diff.diffChars(previous, current);
logger.trace('Diff: ', diff);
let currentOffset = 0;
const changes: MicroChange[] = [];
for (const current of diff) {
if (current.added) {
changes.push({
t: 'I',
o: currentOffset,
v: current.value,
});
//currentOffset += current.count || 0;
} else if (current.removed) {
changes.push({
t: 'D',
o: currentOffset,
l: current.count || 0,
});
currentOffset += current.count || 0;
} else {
currentOffset += current.count || 0;
}
}
logger.trace('Changeset: ', changes);
return changes;
};
export interface ChangesWithOffset {
changes: MicroChange[];
offset: number;
}
/**
* What is that ?
*/
export const getMicroChangeReduce = (previous: string, current: string): MicroChange[] => {
logger.trace('Previous:', previous);
logger.trace('New:', current);
const diff = Diff.diffChars(previous, current);
logger.trace('Diff: ', diff);
const reduction = diff.reduce<ChangesWithOffset>(
(acc, current) => {
logger.trace('Acc: ', acc);
logger.trace('Cur: ', current);
const newOffset = acc.offset + (current.count || 0);
logger.trace('NewOffset: ', newOffset);
if (current.added) {
const nAcc: ChangesWithOffset = {
changes: [
...acc.changes,
{
t: 'I',
o: acc.offset,
v: current.value,
},
],
offset: newOffset,
};
logger.trace('NewAcc: ', nAcc);
return nAcc;
} else Iif (current.removed) {
const nAcc: ChangesWithOffset = {
changes: [
...acc.changes,
{
t: 'D',
o: acc.offset,
l: current.count || 0,
},
],
offset: newOffset,
};
logger.trace('NewAcc: ', nAcc);
return nAcc;
}
const nAcc = {
...acc,
offset: newOffset,
};
logger.trace('NewAcc: ', nAcc);
return nAcc;
},
{ changes: [], offset: 0 },
);
logger.trace('Changeset: ', reduction);
return reduction.changes;
};
/**
* Apply one microchange to buffer
*/
function applyChange(buffer: string, mu: MicroChange): string {
if (mu.t === 'D' && mu.l != null) {
return buffer.substring(0, mu.o) + buffer.substring(mu.o + mu.l);
} else if (mu.t === 'I' && mu.v != null) {
return buffer.substring(0, mu.o) + mu.v + buffer.substring(mu.o);
} else E{
logger.error('Invalid change: ', mu);
return buffer;
}
}
export interface Offsets {
[index: number]: number;
}
function modifyOffsets(offsets: Offsets, index: number, value: number) {
logger.info('modifying offsets: ', offsets, 'index: ', index, 'value: ', value);
let currentOffset = offsets[index] || 0;
currentOffset += value;
offsets[index] = currentOffset;
/*const modified: Offsets = {};
for (const sKey in offsets) {
const key = +sKey;
if (key > index && key < index + value) {
logger.error('Conflict modifying offsets: ', offsets, 'index: ', index, 'value: ', value);
}
if (key > index) {
// current offset is after the new offset
// should be moved
const oValue = offsets[key];
if (oValue != null) {
const newKey = key + value;
let newValue = oValue;
const newOffset = offsets[newKey];
if (newOffset) {
newValue = newOffset + newValue;
}
modified[key] = 0;
delete modified[key];
modified[newKey] = newValue;
}
}
}
for (const sKey in modified) {
const key = +sKey;
const current = modified[key];
if (current != null) {
offsets[key] = current;
}
}*/
}
export function computeOffsets(microchanges: MicroChange[]): Offsets {
const offsets: Offsets = {};
for (let i = microchanges.length - 1; i >= 0; i--) {
const mu = microchanges[i]!;
if (mu.t === 'D') {
if (mu.l != null) {
modifyOffsets(offsets, mu.o + mu.l, -mu.l);
}
} else {
if (mu.v != null) {
modifyOffsets(offsets, mu.o, mu.v.length);
}
}
}
return offsets;
}
export function shiftOffsets(offsets: Offsets, change: Change): Offsets {
const shifted: Offsets = {};
const microchanges = change.microchanges;
for (const offsetStringIndex in offsets) {
let offsetIndex = +offsetStringIndex;
const offsetValue = offsets[offsetIndex] || 0;
logger.trace('Shift O ', offsetIndex, '=', offsetValue);
for (let i = microchanges.length - 1; i >= 0; i--) {
const mu = microchanges[i]!;
if (mu.o <= offsetIndex) {
if (mu.t === 'D') {
if (mu.l != null) {
offsetIndex -= mu.l;
}
} else if (mu.v != null) {
offsetIndex += mu.v.length;
}
}
}
shifted[offsetIndex] = offsetValue;
}
logger.info('ShiftOffsets ', offsets, ' according to ', change, ' gives ', shifted);
return shifted;
}
function shift(change: Change, offsets: Offsets, _forward: boolean) {
//const way = forward ? 1 : -1; //TODO
logger.trace('Shift ', change, ' with offsets: ', offsets);
for (let i = 0; i < change.microchanges.length; i++) {
const mu = change.microchanges[i]!;
for (const key in offsets) {
const offsetIndex = +key;
const offsetValue = offsets[offsetIndex]!;
const muStart = mu.o;
if (offsetValue > 0 && mu.t === 'I') {
if (mu.o >= offsetIndex) {
mu.o += offsetValue;
}
} else if (offsetValue < 0 && mu.t === 'D') {
const deleteFromIndex = offsetIndex + offsetValue;
const deleteToIndex = offsetIndex;
const muEnd = muStart + mu.l!;
// tree major cases
if (muEnd < deleteFromIndex) {
// nothind to do
} else if (muStart > deleteToIndex) {
mu.o += offsetValue;
} else {
// deletions overlap
if (muStart <= deleteFromIndex && muEnd >= deleteToIndex) {
// mu wraps offset
// off |---|
// mu |---------|
// new mu |--- -|
mu.l! += offsetValue;
} else if (muStart >= deleteFromIndex && muEnd <= deleteToIndex) {
// offset wraps mu => mu is useless
// off |---------|
// mu |---|
// new mu canceled
change.microchanges.splice(i, 1);
i--;
} else if (muStart <= deleteFromIndex && muEnd <= deleteToIndex) {
// partial overlap
// off |-----|
// mu |-----|
// new mu |--|
mu.l = deleteFromIndex - muStart;
} else if (muStart >= deleteFromIndex && muEnd >= deleteToIndex) {
// partial overlap
// off |-----|
// mu |-----|
// new mu |--| shifted at offsetStart
mu.l = muEnd - deleteToIndex;
mu.o = deleteFromIndex;
} else E{
logger.error('Unhandled case offset{}:{}, mu:{}', offsetIndex, offsetValue, mu);
}
}
} else if (offsetValue < 0 && mu.t === 'I') {
// offset is deletion, mu is addition
const deleteFromIndex = offsetIndex + offsetValue;
const deleteToIndex = offsetIndex;
if (muStart >= deleteToIndex) {
// off |-----|
// mu |+++++|
// just shift to the left
mu.o += offsetValue;
} else if (muStart > deleteFromIndex) {
// off |-----|
// mu |+|
// mu var1 |+|
mu.o = deleteFromIndex;
} else {
// off |-----|
// mu |+|
// nothing to do
}
} else if (offsetValue > 0 && mu.t === 'D') {
// offset is addition, mu is deletion
const muEnd = muStart + mu.l!;
if (muEnd < offsetIndex) {
// off |+|
// mus |---|
// nothing to do
} else if (muStart > offsetIndex) {
// off |+|
// mu |---|
// new mu : shift
mu.o += offsetValue;
} else {
// off |+|
// mu |--------|
// new v1 |--| |--|
const totalLength = mu.l!;
mu.l = offsetIndex - muStart;
const newMu: MicroChange = {
t: 'D',
o: offsetIndex + offsetValue,
l: totalLength - mu.l,
};
change.microchanges.splice(i + 1, 0, newMu);
i++;
}
}
}
}
logger.trace('Shifted ', change);
}
function propagateOffsets(
changes: Change[],
parent: Change,
offsets: Offsets,
forward: boolean,
offsetFromRev: string,
) {
const children = changes.filter(ch => ch.basedOn.indexOf(parent.revision) >= 0);
logger.debug('Propagate offsets to ', children.length, ' children #');
for (const child of children) {
const childDep = getAllDependencies(changes, child);
if (childDep.indexOf(offsetFromRev) < 0) {
logger.debug('PropagateOffset ', offsets, '@', offsetFromRev, ' to ', child);
shift(child, offsets, forward);
logger.debug('PropagateOffsetAfterShift ', offsets);
const shiftedOffets = shiftOffsets(offsets, child);
logger.debug('Shifted Offsets: ', shiftedOffets);
propagateOffsets(changes, child, shiftedOffets, forward, offsetFromRev);
} else {
// merge has been done
logger.info('Do not go deeper than ', child);
const index = child.basedOn.indexOf(offsetFromRev);
if (index >= 0) {
child.basedOn.splice(index, 1);
}
}
}
}
function getByRevision(changes: Change[], revision: string) {
return changes.find(ch => ch.revision === revision);
}
function getAllDependencies(changes: Change[], change: Change): string[] {
const deps: { [key: string]: boolean } = {};
const queue: Change[] = [];
queue.push(change);
while (queue.length > 0) {
const ch = queue.shift();
if (ch != null) {
ch.basedOn.forEach(dep => {
if (!deps[dep]) {
deps[dep] = true;
const parent = getByRevision(changes, dep);
if (parent != null && queue.indexOf(parent) < 0) {
queue.push(parent);
}
}
});
}
}
return Object.keys(deps);
}
function containsAll(list: unknown[], sublist: unknown[]): boolean {
for (const item of sublist) {
Iif (list.indexOf(item) < 0) {
return false;
}
}
return true;
}
function setsEqual(a: string[], b: string[]) {
Iif (a.length != b.length) {
return false;
}
return containsAll(a, b);
}
function rebase(allChanges: Change[], newBase: Change, change: Change) {
const baseDeps = getAllDependencies(allChanges, newBase);
const changeDeps = getAllDependencies(allChanges, change);
if (setsEqual(baseDeps, changeDeps)) {
// exact same set of dependencies: changes are sieblings
const offsets = computeOffsets(newBase.microchanges);
const newBaseRev = newBase.revision;
logger.info('Rebase Sieblings: ', change, ' on ', newBase, ' with offset ', offsets);
shift(change, offsets, true);
logger.info('Rebase done: ', change, ' on ', newBase, ' with offset ', offsets);
propagateOffsets(allChanges, change, offsets, true, newBaseRev);
change.basedOn = [newBaseRev];
} else Eif (setsEqual([change.revision], newBase.basedOn)) {
logger.info('Inverse hierarchy : ', change, ' on ', newBase);
const offsets = computeOffsets(newBase.microchanges);
newBase.basedOn = change.basedOn;
change.basedOn = [newBase.revision];
shift(newBase, offsets, false);
const newBaseOffsets = computeOffsets(newBase.microchanges);
shift(change, newBaseOffsets, true);
} else if (containsAll(changeDeps, baseDeps)) {
logger.info('Nothing to do: change includes all base parents');
} else {
logger.error('Changes must be sieblings or newBase must be a child of change');
}
}
/**
* Apply all µchanges to content
*/
export const process = (
content: string,
revision: string,
changeset: Change[],
): {
value: string;
revision: string[];
mergedChanges: Change[];
} => {
let buffer = content;
let currentRevision: string = revision;
// clone changset so they are mutable
const changes = changeset.map(c => ({
...c,
microchanges: c.microchanges.map(mu => ({ ...mu })),
basedOn: [...c.basedOn],
}));
const appliedChanges: string[] = [];
const mergedChanges: Change[] = [];
const deps: string[] = [currentRevision];
logger.debug('Process: ', ...changes, ' to ', content);
while (changes.length > 0) {
appliedChanges.push(currentRevision);
// fetch all changes based on the current revision
const children = changes.filter(change => change.basedOn.indexOf(currentRevision) >= 0);
if (children.length > 0) {
logger.debug('All @', currentRevision, ' children: ', children);
// find a child which depends only only already applied changes
// This may be the case when changes order is quite messed up due to network asyncness
const change = children.filter(ch => containsAll(appliedChanges, ch.basedOn))[0];
if (change != null) {
const originalChange = getByRevision(changeset, change.revision);
if (originalChange != null) {
deps.push(change.revision);
removeAllItems(deps, originalChange.basedOn);
}
changes.splice(changes.indexOf(change), 1);
children.splice(children.indexOf(change), 1);
const muChanges = [...change.microchanges];
muChanges.reverse();
logger.debug('Process: ', change);
for (const mu of muChanges) {
buffer = applyChange(buffer, mu);
}
logger.debug(' -> ', buffer);
mergedChanges.push(change);
// rebase sieblings
children.reverse();
for (const child of children) {
changes.splice(changes.indexOf(child), 1);
rebase(changes, change, child);
changes.unshift(child);
}
currentRevision = change.revision;
} else E{
logger.error('Inconsistent changes: all children have unapplied parent ', children);
throw new Error('Inconsistent changset: unapplied parent ' + children);
}
} else E{
logger.error('Inconsistent changes: no children for @', currentRevision, ' in ', changes);
//throw new Error('Inconsistent changset: missing ' + currentRevision + ' children');
break;
}
logger.trace('Processed revision is ', currentRevision);
}
return {
value: buffer,
revision: deps,
mergedChanges: mergedChanges,
};
};
/**
* merge ch1 within ch2
* returns changes which contains set of unique changes
* and set of duplicates, which contains ch2 changes which
* previously exists in ch1
*
*/
export const merge = (
ch1: Change[],
ch2: Change[],
): { changes: Change[]; duplicates: Change[] } => {
return ch2.reduce<{
changes: Change[];
duplicates: Change[];
}>(
(acc, cur) => {
if (acc.changes.find(c => c.revision === cur.revision)) {
return {
changes: acc.changes,
duplicates: [...acc.duplicates, cur],
};
} else {
return {
changes: [...acc.changes, cur],
duplicates: acc.duplicates,
};
}
},
{ changes: [...ch1], duplicates: [] },
);
};
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