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73 lines
2.0 KiB
73 lines
2.0 KiB
const jsonDiffer = require('fast-json-patch')
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const clone = require('clone')
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/** @module*/
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module.exports = {
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generateHistoryEntry,
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replayHistory,
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snapshotFromTxMeta,
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migrateFromSnapshotsToDiffs,
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}
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/**
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converts non-initial history entries into diffs
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@param longHistory {array}
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@returns {array}
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*/
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function migrateFromSnapshotsToDiffs (longHistory) {
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return (
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longHistory
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// convert non-initial history entries into diffs
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.map((entry, index) => {
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if (index === 0) {
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return entry
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}
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return generateHistoryEntry(longHistory[index - 1], entry)
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})
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)
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}
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/**
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Generates an array of history objects sense the previous state.
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The object has the keys
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op (the operation performed),
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path (the key and if a nested object then each key will be seperated with a `/`)
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value
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with the first entry having the note and a timestamp when the change took place
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@param previousState {object} - the previous state of the object
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@param newState {object} - the update object
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@param note {string} - a optional note for the state change
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@returns {array}
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*/
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function generateHistoryEntry (previousState, newState, note) {
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const entry = jsonDiffer.compare(previousState, newState)
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// Add a note to the first op, since it breaks if we append it to the entry
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if (entry[0]) {
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if (note) {
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entry[0].note = note
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}
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entry[0].timestamp = Date.now()
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}
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return entry
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}
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/**
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Recovers previous txMeta state obj
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@returns {object}
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*/
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function replayHistory (_shortHistory) {
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const shortHistory = clone(_shortHistory)
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return shortHistory.reduce((val, entry) => jsonDiffer.applyPatch(val, entry).newDocument)
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}
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/**
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@param txMeta {Object}
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@returns {object} a clone object of the txMeta with out history
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*/
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function snapshotFromTxMeta (txMeta) {
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// create txMeta snapshot for history
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const snapshot = clone(txMeta)
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// dont include previous history in this snapshot
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delete snapshot.history
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return snapshot
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}
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