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// external modules
var DiffMatchPatch = require('diff-match-patch')
var dmp = new DiffMatchPatch()
// core
var config = require('../config.js')
var logger = require('../logger.js')
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 (!data.hasOwnProperty('lastDoc') || !data.hasOwnProperty('currDoc')) {
return logger.error('dmp worker error: not enough data on create patch')
}
try {
var 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 (!data.hasOwnProperty('revisions') || !data.hasOwnProperty('count')) {
return logger.error('dmp worker error: not enough data on get revision')
}
try {
var 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) {
var msStart = (new Date()).getTime()
var diff = dmp.diff_main(lastDoc, currDoc)
var patch = dmp.patch_make(lastDoc, diff)
patch = dmp.patch_toText(patch)
var msEnd = (new Date()).getTime()
if (config.debug) {
logger.info(patch)
logger.info((msEnd - msStart) + 'ms')
}
return patch
}
function getRevision (revisions, count) {
var msStart = (new Date()).getTime()
var startContent = null
var lastPatch = []
var applyPatches = []
var authorship = []
if (count <= Math.round(revisions.length / 2)) {
// start from top to target
for (let i = 0; i < count; i++) {
let revision = revisions[i]
if (i === 0) {
startContent = revision.content || revision.lastContent
}
if (i !== count - 1) {
let 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++) {
var 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
var l = revisions.length - 1
for (var i = l; i >= count - 1; i--) {
let revision = revisions[i]
if (i === l) {
startContent = revision.lastContent
authorship = revision.authorship
}
if (revision.patch) {
let patch = dmp.patch_fromText(revision.patch)
applyPatches = applyPatches.concat(patch)
}
lastPatch = revision.patch
authorship = revision.authorship
}
}
try {
var finalContent = dmp.patch_apply(applyPatches, startContent)[0]
} catch (err) {
throw new Error(err)
}
var data = {
content: finalContent,
patch: dmp.patch_fromText(lastPatch),
authorship: authorship
}
var msEnd = (new Date()).getTime()
if (config.debug) {
logger.info((msEnd - msStart) + 'ms')
}
return data
}
// 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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