daton/lib/src/http/system_middleware/StaticServer.ts

import Middleware from '../Middleware.ts'
import {Request} from '../Request.ts'
import {Injectable} from '../../../../di/src/decorator/Injection.ts'
import {file, http} from '../response/helpers.ts'
import {HTTPStatus} from '../../const/http.ts'
import {Logging} from '../../service/logging/Logging.ts'
import {UniversalPath} from "../../support/UniversalPath.ts";

/**
 * Daton-provided middleware that serves files from a static directory.
 * @extends Middleware
 */
@Injectable()
export default class StaticServer extends Middleware {

    constructor(
        protected readonly logger: Logging,
    ) { super() }

    /**
     * Handle an incoming request. Get the path to the file from the route params, and
     * resolve it using the asset_dir argument. If the file exists, serve it.
     * @param {Request} request
     * @param {string} asset_dir
     */
    public async handleRequest(request: Request, asset_dir?: string) {
        if ( !asset_dir ) {
            throw new Error(`This static server is mis-configured. You must provide, as an argument in the route definition, the relative path to the base directory of the static files to be served.`)
        }

        const params = request.route.params
        const rel_file = params.$1

        if ( !rel_file || !rel_file.trim() || rel_file.trim().startsWith('/') || rel_file.trim().startsWith('.') ) {
            this.logger.info(`Blocked attempt to access invalid static file path: "${rel_file}"`)
            return http(HTTPStatus.NOT_FOUND)
        }

        const abs_file = this.resolve(asset_dir, rel_file)
        if ( !(await this.fileExists(abs_file)) ) {
            this.logger.debug(`File does not exist: ${abs_file}`)
            return http(HTTPStatus.NOT_FOUND)
        }

        return file(abs_file)
    }

    /**
     * Given the asset base dir and a relative path, resolve the fully-qualified
     * path to the file.
     * @param {string} asset_dir
     * @param {string} rel_file
     * @return string
     */
    protected resolve(asset_dir: string, rel_file: string): UniversalPath {
        return this.app.app_path(asset_dir, rel_file)
    }

    /**
     * Resolves true if the given path exists, and is a file.
     * @param {string} path
     * @return Promise<boolean>
     */
    protected async fileExists(path: UniversalPath): Promise<boolean> {
        try {
            const stat = await Deno.lstat(path.to_local)
            return stat && stat.isFile
        } catch (e) {
            if ( e && e instanceof Deno.errors.NotFound ) {
                return false
            } else {
                throw e
            }
        }
    }
}