fs-zoo/lib/overlay/OverlayCrud.js

File system abstractions and implementations

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.OverlayCrud = void 0;
const util_1 = require("../crud/util");
const RouterCrud_1 = require("../router/RouterCrud");
class OverlayRouter {
    constructor(layers) {
        this.layers = layers;
    }
    resolve(path) {
        const parts = (0, util_1.parseParts)(path);
        const normalized = parts.join('/');
        const normalizedLength = normalized.length;
        let matchedFs;
        let rest = '';
        for (const [key, fs] of Object.entries(this.layers)) {
            if (!key) {
                if (!matchedFs) {
                    matchedFs = fs;
                    rest = normalized;
                }
                continue;
            }
            if (!normalized.startsWith(key))
                continue;
            if (normalizedLength - key.length < rest.length) {
                matchedFs = fs;
                rest = normalized.slice(key.length);
            }
        }
        if (!matchedFs)
            throw new Error('NO_OVERLAY');
        return [rest, matchedFs];
    }
    nested(path) {
        const entries = Object.entries(this.layers);
        if (!path)
            return entries;
        const matches = [];
        for (const [key, fs] of entries) {
            if (key.startsWith(path)) {
                matches.push([key.slice(path.length + 1), fs]);
            }
        }
        return matches;
    }
}
/**
 * An "overlay" file system, which can combine multiple CRUD-fs file systems
 * into one. Accepts one default file system and any number of additional
 * file systems to overlay on top at specific paths.
 *
 * A layer mounted at `''` (or `[]`) will be the default file system, it will
 * receive all requests that do not match any other layer.
 *
 * Example:
 *
 * ```
 * const fs = new OverlayCrud();
 * fs.overlay([], root);
 * fs.overlay(['usr', 'virtual'], userHome);
 * ```
 */
class OverlayCrud extends RouterCrud_1.RouterCrud {
    constructor(layers = {}) {
        const router = new OverlayRouter(layers);
        super(router);
        this._router = router;
    }
    mount(path, fs) {
        const collection = (0, util_1.parseParts)(path);
        const isRoot = collection.length === 0 || (collection.length === 1 && collection[0] === '');
        if (!isRoot)
            (0, util_1.assertType)(collection, 'overlay', 'crudfs');
        const key = isRoot ? '' : collection.join('/');
        const layers = this._router.layers;
        if (key in layers)
            throw new Error(`Layer already exists: /${key}`);
        this._router.layers[key] = fs;
    }
    unmount(path) {
        const collection = (0, util_1.parseParts)(path);
        const isRoot = collection.length === 0 || (collection.length === 1 && collection[0] === '');
        const key = isRoot ? '' : collection.join('/');
        const layers = this._router.layers;
        const exists = key in layers;
        delete layers[key];
        return exists;
    }
}
exports.OverlayCrud = OverlayCrud;