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const asyncQ = require('async-q')
class Migrator {
constructor (opts = {}) {
let migrations = opts.migrations || []
this.migrations = migrations.sort((a, b) => a.version - b.version)
let lastMigration = this.migrations.slice(-1)[0]
// use specified defaultVersion or highest migration version
this.defaultVersion = opts.defaultVersion || (lastMigration && lastMigration.version) || 0
}
// run all pending migrations on meta in place
migrateData (versionedData = this.generateInitialState()) {
let remaining = this.migrations.filter(migrationIsPending)
return (
asyncQ.eachSeries(remaining, (migration) => migration.migrate(versionedData))
.then(() => versionedData)
)
// migration is "pending" if hit has a higher
// version number than currentVersion
function migrationIsPending(migration) {
return migration.version > versionedData.meta.version
}
}
generateInitialState (initState) {
return {
meta: {
version: this.defaultVersion,
},
data: initState,
}
}
}
module.exports = Migrator
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