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'use strict'
// external modules
const DiffMatchPatch = require('diff-match-patch')
const dmp = new DiffMatchPatch()
// core
const logger = require('../logger')
process.on('message', function (data) {
if (!data || !data.msg || !data.cacheKey) {
return logger.error('dmp worker error: not enough data')
}
switch (data.msg) {
case 'create patch':
if (
!Object.prototype.hasOwnProperty.call(data, 'lastDoc') ||
!Object.prototype.hasOwnProperty.call(data, 'currDoc')
) {
return logger.error(
'dmp worker error: not enough data on create patch'
)
}
try {
const patch = createPatch(data.lastDoc, data.currDoc)
process.send({
msg: 'check',
result: patch,
cacheKey: data.cacheKey
})
} catch (err) {
logger.error('dmp worker error', err)
process.send({
msg: 'error',
error: err,
cacheKey: data.cacheKey
})
}
break
case 'get revision':
if (
!Object.prototype.hasOwnProperty.call(data, 'revisions') ||
!Object.prototype.hasOwnProperty.call(data, 'count')
) {
return logger.error(
'dmp worker error: not enough data on get revision'
)
}
try {
const result = getRevision(data.revisions, data.count)
process.send({
msg: 'check',
result: result,
cacheKey: data.cacheKey
})
} catch (err) {
logger.error('dmp worker error', err)
process.send({
msg: 'error',
error: err,
cacheKey: data.cacheKey
})
}
break
}
})
function createPatch (lastDoc, currDoc) {
const msStart = new Date().getTime()
const diff = dmp.diff_main(lastDoc, currDoc)
let patch = dmp.patch_make(lastDoc, diff)
patch = dmp.patch_toText(patch)
const msEnd = new Date().getTime()
logger.debug(patch)
logger.debug(msEnd - msStart + 'ms')
return patch
}
function getRevision (revisions, count) {
const msStart = new Date().getTime()
let startContent = null
let lastPatch = []
let applyPatches = []
let authorship = []
if (count <= Math.round(revisions.length / 2)) {
// start from top to target
for (let i = 0; i < count; i++) {
const revision = revisions[i]
if (i === 0) {
startContent = revision.content || revision.lastContent
}
if (i !== count - 1) {
const patch = dmp.patch_fromText(revision.patch)
applyPatches = applyPatches.concat(patch)
}
lastPatch = revision.patch
authorship = revision.authorship
}
// swap DIFF_INSERT and DIFF_DELETE to achieve unpatching
for (let i = 0, l = applyPatches.length; i < l; i++) {
for (let j = 0, m = applyPatches[i].diffs.length; j < m; j++) {
const diff = applyPatches[i].diffs[j]
if (diff[0] === DiffMatchPatch.DIFF_INSERT) {
diff[0] = DiffMatchPatch.DIFF_DELETE
} else if (diff[0] === DiffMatchPatch.DIFF_DELETE) {
diff[0] = DiffMatchPatch.DIFF_INSERT
}
}
}
} else {
// start from bottom to target
const l = revisions.length - 1
for (let i = l; i >= count - 1; i--) {
const revision = revisions[i]
if (i === l) {
startContent = revision.lastContent
authorship = revision.authorship
}
if (revision.patch) {
const patch = dmp.patch_fromText(revision.patch)
applyPatches = applyPatches.concat(patch)
}
lastPatch = revision.patch
authorship = revision.authorship
}
}
try {
const finalContent = dmp.patch_apply(applyPatches, startContent)[0]
const data = {
content: finalContent,
patch: dmp.patch_fromText(lastPatch),
authorship: authorship
}
const msEnd = new Date().getTime()
logger.debug(msEnd - msStart + 'ms')
return data
} catch (err) {
throw new Error(err)
}
}
// log uncaught exception
process.on('uncaughtException', function (err) {
logger.error('An uncaught exception has occured.')
logger.error(err)
logger.error('Process will exit now.')
process.exit(1)
})
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