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// external modules
var LZString = require('lz-string');
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 ms_start = (new Date()).getTime();
var diff = dmp.diff_main(lastDoc, currDoc);
dmp.diff_cleanupSemantic(diff);
var patch = dmp.patch_make(lastDoc, diff);
patch = dmp.patch_toText(patch);
var ms_end = (new Date()).getTime();
if (config.debug) {
logger.info(patch);
logger.info((ms_end - ms_start) + 'ms');
}
return patch;
}
function getRevision(revisions, count) {
var ms_start = (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 (var i = 0; i < count; i++) {
var revision = revisions[i];
if (i == 0) {
startContent = LZString.decompressFromBase64(revision.content || revision.lastContent);
}
if (i != count - 1) {
var patch = dmp.patch_fromText(LZString.decompressFromBase64(revision.patch));
applyPatches = applyPatches.concat(patch);
}
lastPatch = revision.patch;
authorship = revision.authorship;
}
// swap DIFF_INSERT and DIFF_DELETE to achieve unpatching
for (var i = 0, l = applyPatches.length; i < l; i++) {
for (var 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--) {
var revision = revisions[i];
if (i == l) {
startContent = LZString.decompressFromBase64(revision.lastContent);
authorship = revision.authorship;
}
if (revision.patch) {
var patch = dmp.patch_fromText(LZString.decompressFromBase64(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(LZString.decompressFromBase64(lastPatch)),
authorship: authorship ? JSON.parse(LZString.decompressFromBase64(authorship)) : null
};
var ms_end = (new Date()).getTime();
if (config.debug) {
logger.info((ms_end - ms_start) + '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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