109 lines
3.0 KiB
TypeScript
109 lines
3.0 KiB
TypeScript
/**
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* Configuration loader
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*
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* Copyright (C) 2010-2019 R-T Specialty, LLC.
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*
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* This file is part of the Liza Data Collection Framework.
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*
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* liza is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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import { readFile } from "fs";
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import { Store } from "../store/Store";
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/**
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* Load system configuration from JSON
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*
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* @example
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* ConfLoader( require( 'fs' ), SomeStore )
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* .fromFile( 'conf/vanilla-server.json' )
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* .then( conf => conf.get( 'foo' ) );
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*
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* TODO: Merging multiple configuration files would be convenient for
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* modular configuration.
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*/
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export class ConfLoader
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{
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/**
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* Initialize with provided filesystem module and Store constructor
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*
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* The module should implement `#readFile` compatible with
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* Node.js'. The Store constructor `store_ctor` is used to instantiate
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* new stores to be populated with configuration data.
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*
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* @param fs - filesystem module
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* @param store_ctor - Store object constructor
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*/
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constructor(
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private _fs: { readFile: typeof readFile },
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private _storeCtor: () => Store,
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) {}
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/**
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* Produce configuration from file
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*
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* A Store will be produced, populated with the configuration data.
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*
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* @param filename - path to configuration JSON
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*
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* @return a promise of a populated Store
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*/
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fromFile( filename: string ): Promise<Store>
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{
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return new Promise( ( resolve, reject ) =>
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{
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this._fs.readFile( filename, 'utf8', ( err, data ) =>
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{
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if ( err )
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{
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reject( err );
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return;
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}
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try
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{
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const store = this._storeCtor();
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resolve(
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this.parseConfData( data )
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.then( parsed => store.populate( parsed ) )
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.then( _ => store )
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);
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}
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catch ( e )
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{
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reject( e );
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}
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} );
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} );
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}
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/**
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* Parse raw configuration string
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*
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* Parses configuration string as JSON.
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*
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* @param data raw configuration data
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*
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* @return `data` parsed as JSON
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*/
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protected parseConfData( data: string ): Promise<any>
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{
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return Promise.resolve( JSON.parse( data ) );
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}
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}
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