97 lines
3.0 KiB
JavaScript
97 lines
3.0 KiB
JavaScript
import EventEmitter from 'events';
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/**
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* @typedef {object} Migration
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* @property {number} version - The migration version
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* @property {Function} migrate - Returns a promise of the migrated data
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*/
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/**
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* @typedef {object} MigratorOptions
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* @property {Array<Migration>} [migrations] - The list of migrations to apply
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* @property {number} [defaultVersion] - The version to use in the initial state
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*/
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export default class Migrator extends EventEmitter {
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/**
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* @param {MigratorOptions} opts
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*/
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constructor(opts = {}) {
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super();
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const migrations = opts.migrations || [];
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// sort migrations by version
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this.migrations = migrations.sort((a, b) => a.version - b.version);
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// grab migration with highest version
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const lastMigration = this.migrations.slice(-1)[0];
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// use specified defaultVersion or highest migration version
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this.defaultVersion =
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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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async migrateData(versionedData = this.generateInitialState()) {
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// get all migrations that have not yet been run
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const pendingMigrations = this.migrations.filter(migrationIsPending);
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// perform each migration
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for (const migration of pendingMigrations) {
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try {
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// attempt migration and validate
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const migratedData = await migration.migrate(versionedData);
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if (!migratedData.data) {
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throw new Error('Migrator - migration returned empty data');
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}
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if (
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migratedData.version !== undefined &&
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migratedData.meta.version !== migration.version
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) {
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throw new Error(
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'Migrator - Migration did not update version number correctly',
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);
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}
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// accept the migration as good
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// eslint-disable-next-line no-param-reassign
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versionedData = migratedData;
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} catch (err) {
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// rewrite error message to add context without clobbering stack
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const originalErrorMessage = err.message;
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err.message = `MetaMask Migration Error #${migration.version}: ${originalErrorMessage}`;
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// emit error instead of throw so as to not break the run (gracefully fail)
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this.emit('error', err);
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// stop migrating and use state as is
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return versionedData;
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}
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}
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return versionedData;
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/**
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* Returns whether or not the migration is pending
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*
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* A migration is considered "pending" if it has a higher
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* version number than the current version.
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*
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* @param {Migration} migration
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* @returns {boolean}
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*/
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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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/**
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* Returns the initial state for the migrator
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*
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* @param {object} [data] - The data for the initial state
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* @returns {{meta: {version: number}, data: any}}
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*/
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generateInitialState(data) {
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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,
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};
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}
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}
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