closes issue #8

src/lib/File.class.ts

@@ -1,10 +1,11 @@
-import { type WriteStream, createWriteStream, existsSync, statSync } from 'fs'
+import { type WriteStream, createWriteStream, existsSync, statSync, mkdirSync } from 'fs'
 import { isFile, isFilePathString } from '../utils/guards.js'
+import { dirname } from 'path'
 
 export default class File {
   public static $id = 'File'
   private readonly $isValid?: boolean
-  public constructor(private $path: string) {}
+  public constructor(private $path: string, private readonly skipExistsCheck: boolean = false) {}
 
   public validate(): File {
     if (this.$isValid !== undefined) return this
@@ -13,7 +14,7 @@ export default class File {
       throw new Error(`The filename \`${wrongFilePath}\` should start with \`file://\``)
     }
     this.$path = this.$path.replace(/^file:\/\//, '')
-    if (!existsSync(this.$path) || !statSync(this.$path).isFile()) {
+    if (!this.skipExistsCheck && (!existsSync(this.$path) || !statSync(this.$path).isFile())) {
       throw new Error(`File not found: \`${this.$path}\``)
     }
     return this
@@ -23,11 +24,14 @@ export default class File {
     return this.$path
   }
 
-  public getStream(): WriteStream {
+  public getStream(append: boolean = false): WriteStream {
     if (existsSync(this.$path)) {
       // throw new Error(`File already exists: \`${this.$path}\``)
     }
-    return createWriteStream(this.$path)
+    if (!existsSync(dirname(this.$path))) {
+      mkdirSync(dirname(this.$path), { recursive: true})
+    }
+    return createWriteStream(this.$path, append ? {flags: 'a'} : {})
   }
 
   public toString(): string {

src/lib/LDWorkbenchConfiguration.d.ts

@@ -21,7 +21,7 @@ export interface LDWorkbenchConfiguration {
   /**
    * The file where the final result of your pipeline is saved.
    */
-  destination: string;
+  destination?: string;
   /**
    * This is where you define the individual iterator/generator for each step.
    *

src/lib/Pipeline.class.ts

@@ -4,22 +4,33 @@ import type { LDWorkbenchConfiguration } from "./LDWorkbenchConfiguration.js";
 import chalk from "chalk";
 import Stage from "./Stage.class.js";
 import duration from "../utils/duration.js";
+import File from './File.class.js'
 import path from "node:path";
 import * as fs from "node:fs";
+import { isFilePathString } from '../utils/guards.js';
 
 class Pipeline {
   public readonly stages = new Map<string, Stage>();
   public dataDir: string;
   private $isValidated: boolean = false;
   private stageNames: string[] = [];
   private now = new Date();
+  private readonly destination: File
 
   public constructor(
     private readonly $configuration: LDWorkbenchConfiguration
   ) {
     //  create data folder:
     this.dataDir = path.join("data", kebabcase(this.$configuration.name));
     fs.mkdirSync(this.dataDir, { recursive: true });
+    const destinationFile = this.configuration.destination ?? `file://${path.join(this.dataDir, 'statements.nt')}`
+    if (!isFilePathString(destinationFile)) {
+      throw new Error('We currently only allow publishing data to local files.')
+    }
+    if(!destinationFile.endsWith('.nt')) {
+      throw new Error('We currently only writing results in N-Triples format,\nmake sure your destination filename ends with \'.nt\'.')
+    }
+    this.destination = new File(destinationFile, true)
   }
 
   private error(e: Error, stage?: string): void {
@@ -142,7 +153,7 @@ class Pipeline {
       if (this.stageNames.length !== 0) {
         this.runRecursive();
       } else {
-        this.concat()
+        this.writeResult()
           console.info(
             chalk.green(
               `✔ your pipeline "${chalk.bold(
@@ -159,10 +170,14 @@ class Pipeline {
     }
   }
 
-  private concat(): void {
+  private writeResult(): void {
     const spinner = ora("Combining statements from all stages:").start();
-    const destinationPath = path.join(this.dataDir, 'statements.nt')
-    const destinationStream = fs.createWriteStream(destinationPath, {flags:'a'})
+
+    const destinationPathNew = this.configuration.destination
+    if (!isFilePathString(destinationPathNew)) {
+      throw new Error('We currently only allow publishing data to local files.')
+    }
+    const destinationStream = this.destination.getStream()
     const stageNames = Array.from(this.stages.keys())
     for (const stageName of stageNames) {
       spinner.suffixText = chalk.bold(stageName)
@@ -171,7 +186,7 @@ class Pipeline {
         destinationStream.write(buffer)
       })
     }
-    spinner.suffixText = chalk.bold(destinationPath)
+    spinner.suffixText = chalk.bold(this.destination.toString())
     spinner.succeed()
   }
 

static/example/config.yml

@@ -1,14 +1,13 @@
 # Metadata for your pipeline:
 name: Example Pipeline
-destination: file://data/example/example.ttl
 description: >
   This is an example pipeline. It uses files that are available in this repository 
   and SPARQL endpoints that should work.
 
 # The individual stages for your pipeline
 stages:
   - name: "Stage 1"
-    iterator: 
+    iterator:
       query: file://static/example/iterator-stage-1.rq
       endpoint: https://api.triplydb.com/datasets/Triply/iris/services/demo-service/sparql
     generator: 

static/ld-workbench.schema.json

@@ -77,5 +77,5 @@
       }
     }
   },
-  "required": ["name", "destination", "stages"]
+  "required": ["name", "stages"]
 }