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51 lines
1.6 KiB
51 lines
1.6 KiB
const asyncQ = require('async-q')
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class Migrator {
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constructor (opts = {}) {
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let migrations = opts.migrations || []
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this.migrations = migrations.sort((a, b) => a.version - b.version)
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let lastMigration = this.migrations.slice(-1)[0]
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// use specified defaultVersion or highest migration version
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this.defaultVersion = opts.defaultVersion || (lastMigration && lastMigration.version) || 0
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}
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// run all pending migrations on meta in place
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migrateData (versionedData = this.generateInitialState()) {
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let remaining = this.migrations.filter(migrationIsPending)
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return (
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asyncQ.eachSeries(remaining, (migration) => this.runMigration(versionedData, migration))
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.then(() => versionedData)
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)
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// migration is "pending" if hit has a higher
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// version number than currentVersion
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function migrationIsPending(migration) {
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return migration.version > versionedData.meta.version
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}
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}
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runMigration(versionedData, migration) {
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return (
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migration.migrate(versionedData)
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.then((versionedData) => {
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if (!versionedData.data) return Promise.reject(new Error('Migrator - Migration returned empty data'))
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if (migration.version !== undefined && versionedData.meta.version !== migration.version) return Promise.reject(new Error('Migrator - Migration did not update version number correctly'))
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return Promise.resolve(versionedData)
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})
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)
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}
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generateInitialState (initState) {
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return {
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meta: {
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version: this.defaultVersion,
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},
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data: initState,
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}
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}
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}
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module.exports = Migrator
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