feat: Added Node execution engine/delegator

engine/executa.ts

@@ -0,0 +1,101 @@
+import * as childProcess from 'child_process'
+import { getLogger } from '@stencila/logga'
+const lps = require('length-prefixed-stream')
+
+const { spawn } = require('child_process')
+
+const log = getLogger('engine:serve')
+
+interface ExecutorBackend {
+  setup(): void
+
+  execute(o: any): Promise<any>
+}
+
+class StencilaPythonBackend implements ExecutorBackend {
+  private process?: childProcess.ChildProcess
+
+  private stdin: any
+
+  private executionRequests: { [key: number]: any } = {}
+
+  private executionRequestCount: number = 0
+
+  setup(): void {
+    this.process = spawn('python3', ['-m', 'stencila.schema', 'listen'])
+    if (!this.process) throw new Error('Spawning python3 failed')
+    if (
+      this.process.stdout === null ||
+      this.process.stdin === null ||
+      this.process.stderr === null
+    )
+      throw new Error('STDIO is not set up right')
+
+    this.process.stderr.on('data', (data: Buffer) => {
+      log.error(data.toString())
+      process.exit(1)
+    })
+
+    const decoder = lps.decode()
+    this.process.stdout.pipe(decoder)
+    decoder.on('data', (response: Buffer) => this.receive(response))
+
+    this.stdin = lps.encode()
+    this.stdin.pipe(this.process.stdin)
+  }
+
+  receive(json: Buffer, raw: boolean = false) {
+    const response = JSON.parse(json.toString())
+    const resolve = this.executionRequests[response.id]
+    resolve(response.body)
+    delete this.executionRequests[response.id]
+  }
+
+  async execute(o: any): Promise<any> {
+    if (!this.process) {
+      throw new Error('Can not execute before setup')
+    }
+
+    const id = ++this.executionRequestCount
+
+    const req = {
+      id,
+      body: o
+    }
+
+    const promise = new Promise<any>((resolve, reject) => {
+      this.executionRequests[id] = (response: any) => {
+        resolve(response)
+      }
+    })
+
+    this.stdin.write(JSON.stringify(req))
+
+    return promise
+  }
+}
+
+export default class Executa {
+  backends: { [key: string]: ExecutorBackend } = {}
+
+  getBackend(name: string): ExecutorBackend {
+    if (this.backends[name] === undefined) {
+      switch (name) {
+        case 'python':
+          this.backends[name] = new StencilaPythonBackend()
+          break
+        default:
+          throw new Error(`Unknown backend '${name}'`)
+      }
+      this.backends[name].setup()
+    }
+
+    return this.backends[name]
+  }
+
+  async execute(code: any): Promise<any> {
+    const backend = this.getBackend(code.programmingLanguage)
+
+    return await backend.execute(code)
+  }
+}