Downloading anon circuits using webworkers

packages/react-providers/src/election/use-election-provider.ts

@@ -7,9 +7,13 @@ import {
   PublishedElection,
   Vote,
 } from '@vocdoni/sdk'
-import { ComponentType, useCallback, useEffect } from 'react'
+import { ComponentType, useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { useClient } from '../client'
 import { useElectionReducer } from './use-election-reducer'
+import { ChainAPI } from '@vocdoni/sdk'
+import { createWebWorker } from '../worker/webWorker'
+import { useWebWorker } from '../worker/useWebWorker'
+import worker, { ICircuit, ICircuitWorkerRequest } from '../worker/circuitWorkerScript'
 
 export type ElectionProviderProps = {
   id?: string
@@ -40,6 +44,9 @@ export const useElectionProvider = ({
     loaded,
     sik: { password, signature },
   } = state
+  const [anonCircuitsFetched, setAnonCircuitsFetched] = useState(false)
+
+  const isAnonCircuitsFetching = useRef(false)
 
   const fetchElection = useCallback(
     async (id: string) => {
@@ -87,7 +94,10 @@ export const useElectionProvider = ({
     }
   }, [actions, client, election, password, signature])
 
-  const fetchAnonCircuits = useCallback(() => {
+  const workerInstance = useMemo(() => createWebWorker(worker), [])
+  const { result: circuits, startProcessing } = useWebWorker<ICircuit, ICircuitWorkerRequest>(workerInstance)
+
+  const fetchAnonCircuits = useCallback(async () => {
     const hasOverwriteEnabled =
       typeof election !== 'undefined' &&
       typeof election.voteType.maxVoteOverwrites !== 'undefined' &&
@@ -96,16 +106,43 @@ export const useElectionProvider = ({
     const votable = state.isAbleToVote || (hasOverwriteEnabled && state.isInCensus && state.voted)
 
     if (votable && election?.census.type === CensusType.ANONYMOUS) {
-      client.anonymousService.fetchCircuits()
+      const chainCircuits = await ChainAPI.circuits(client.url)
+      const circuits = {
+        zKeyURI: chainCircuits.uri + '/' + chainCircuits.circuitPath + '/' + chainCircuits.zKeyFilename,
+        zKeyHash: chainCircuits.zKeyHash,
+        vKeyURI: chainCircuits.uri + '/' + chainCircuits.circuitPath + '/' + chainCircuits.vKeyFilename,
+        vKeyHash: chainCircuits.vKeyHash,
+        wasmURI: chainCircuits.uri + '/' + chainCircuits.circuitPath + '/' + chainCircuits.wasmFilename,
+        wasmHash: chainCircuits.wasmHash,
+      }
+      startProcessing({ circuits })
     }
   }, [election, state.isAbleToVote, state.isInCensus, state.voted, client.anonymousService])
 
   // pre-fetches circuits needed for voting in anonymous elections
   useEffect(() => {
-    if (!fetchCensus || !election || loading.census || !client.wallet) return
+    if (
+      !fetchCensus ||
+      !election ||
+      loading.census ||
+      !client.wallet ||
+      anonCircuitsFetched ||
+      isAnonCircuitsFetching.current
+    )
+      return
+    isAnonCircuitsFetching.current = true
     fetchAnonCircuits()
   }, [fetchAnonCircuits, client.wallet, election, loading.census, fetchCensus])
 
+  // sets circuits in the anonymous service
+  useEffect(() => {
+    ;(async () => {
+      if (!circuits) return
+      setAnonCircuitsFetched(true)
+      client.anonymousService.setCircuits(circuits)
+    })()
+  }, [circuits])
+
   // CSP OAuth flow
   // As vote setting and voting token are async, we need to wait for both to be set
   useEffect(() => {

packages/react-providers/src/worker/circuitWorkerScript.ts

@@ -0,0 +1,95 @@
+/* eslint-disable no-restricted-globals */
+/* eslint-disable import/no-anonymous-default-export */
+
+import { IBaseWorkerResponse } from './useWebWorker'
+
+export interface ICircuit {
+  zKeyData: Uint8Array
+  zKeyHash: string
+  zKeyURI: string
+  vKeyData: Uint8Array
+  vKeyHash: string
+  vKeyURI: string
+  wasmData: Uint8Array
+  wasmHash: string
+  wasmURI: string
+}
+
+export interface ICircuitWorkerRequest {
+  circuits: {
+    zKeyURI: string
+    zKeyHash: string
+    vKeyURI: string
+    vKeyHash: string
+    wasmURI: string
+    wasmHash: string
+  }
+}
+
+export interface IWorkerResponse extends IBaseWorkerResponse<ICircuit> {}
+
+export const fetchDataInChunks = async (url: string) => {
+  return fetch(url)
+    .then((res) => res.arrayBuffer())
+    .then((res) => new Uint8Array(res))
+}
+
+export default () => {
+  self.addEventListener('message', async (e: MessageEvent<ICircuitWorkerRequest>) => {
+    try {
+      const { circuits } = e.data
+
+      async function fetchDataInChunks(uri: string) {
+        const response = await fetch(uri)
+        const reader = response.body?.getReader() as ReadableStreamDefaultReader
+        const contentLength = +(response.headers?.get('Content-Length') ?? 0)
+
+        const chunks = []
+        let receivedLength = 0
+
+        while (true) {
+          const { done, value } = await reader.read()
+
+          if (done) break
+
+          chunks.push(value)
+          receivedLength += value.length
+
+          // Check for content length, break if all content received
+          if (contentLength && receivedLength >= contentLength) break
+        }
+
+        const concatenatedArray = new Uint8Array(receivedLength)
+        let offset = 0
+
+        for (const chunk of chunks) {
+          concatenatedArray.set(chunk, offset)
+          offset += chunk.length
+        }
+
+        return concatenatedArray
+      }
+
+      const [zKeyData, vKeyData, wasmData] = await Promise.all([
+        fetchDataInChunks(circuits.zKeyURI),
+        fetchDataInChunks(circuits.vKeyURI),
+        fetchDataInChunks(circuits.wasmURI),
+      ])
+
+      const circuitsData: ICircuit = {
+        zKeyData,
+        zKeyURI: circuits.zKeyURI,
+        zKeyHash: circuits.zKeyHash,
+        vKeyData,
+        vKeyURI: circuits.vKeyURI,
+        vKeyHash: circuits.vKeyHash,
+        wasmData,
+        wasmURI: circuits.wasmURI,
+        wasmHash: circuits.wasmHash,
+      }
+      return postMessage({ result: circuitsData } as IWorkerResponse)
+    } catch (error) {
+      return postMessage({ error } as IWorkerResponse)
+    }
+  })
+}

packages/react-providers/src/worker/useWebWorker.ts

@@ -0,0 +1,37 @@
+import { useCallback, useEffect, useState } from 'react'
+
+export interface IBaseWorkerResponse<T> {
+  result: T
+  error?: any
+}
+
+export const useWebWorker = <TResult, TWorkerPayload>(worker: Worker) => {
+  const [running, setRunning] = useState(false)
+  const [error, setError] = useState<any>()
+  const [result, setResult] = useState<TResult>()
+
+  const startProcessing = useCallback(
+    (data: TWorkerPayload) => {
+      setRunning(true)
+      worker.postMessage(data)
+    },
+    [worker]
+  )
+
+  useEffect(() => {
+    const onMessage = (event: MessageEvent<IBaseWorkerResponse<TResult>>) => {
+      setRunning(false)
+      setError(event.data.error)
+      setResult(event.data.result)
+    }
+    worker.addEventListener('message', onMessage)
+    return () => worker.removeEventListener('message', onMessage)
+  }, [worker])
+
+  return {
+    startProcessing,
+    running,
+    error,
+    result,
+  }
+}

packages/react-providers/src/worker/webWorker.ts

@@ -0,0 +1,7 @@
+export const createWebWorker = (worker: any) => {
+  const code = worker.toString()
+  const blob = new Blob(['(' + code + ')()'])
+  const workerURL = (window as any).MockedWindowURL || window.URL || window.webkitURL
+  const blobURL = workerURL.createObjectURL(blob)
+  return new Worker(blobURL)
+}

setup-tests.ts

@@ -25,10 +25,18 @@ class Worker {
   postMessage(msg) {
     this.onmessage(msg)
   }
+  addEventListener() {}
+  removeEventListener() {}
 }
 
 // required due to SDK dependency
-Object.defineProperty(window, 'Worker', Worker)
+Object.defineProperty(window, 'Worker', { value: Worker })
+Object.defineProperty(window, 'MockedWindowURL', {
+  value: {
+    createObjectURL: () => 'blob:mocked',
+    revokeObjectURL: () => {},
+  },
+})
 
 // required by any react component (almost all of them)
 global.React = React