Add simple backend

backend.js

@@ -0,0 +1,113 @@
+const http = require('node:http')
+
+function generateDataSeriesResponse () {
+  let t0 = 1701385200000
+  let N = 501 
+  let dt = 3600000
+  let dataPoints = 
+    (new Array(N))
+    .fill(0)
+    .reduce(({data, i}, x) => ({data:data.concat(i), i:i+1}), {data:[],i:0})
+    .data
+    .reduce(({c1,c2,c3,c4, data}, x) => {
+      let elm = {
+      	t: new Date(t0 + x*dt), 
+      	v1: Math.max(0, c1 - 25 + Math.round(Math.random() * 50)),
+      	v2: Math.max(0, c2 - 100 + Math.round(Math.random() * 200)),
+      	v3: Math.max(0, c3 - 250 + Math.round(Math.random() * 500)),
+      	v4: Math.max(0, c4 - 500 + Math.round(Math.random() * 1000))
+      }
+
+      return {
+        data: data.concat(elm),
+        c1: elm.v1,
+        c2: elm.v2,
+        c3: elm.v3,
+        c4: elm.v4
+      }
+    }, {c1: 50, c2: 200, c3: 500, c4: 1000, data: []})
+    .data
+
+  return {statusCode: 200, body: JSON.stringify(dataPoints), contentType: 'application/json'}
+}
+
+function generateBracketsResponse () {
+  function generateChunk () {
+    let rnd = Math.random()
+    let type = '['
+    if (rnd < 0.25) {
+      type = '{'
+    }
+    else if (rnd < 0.5) {
+      type = '('
+    }
+    else if (rnd < 0.75) {
+      type = '<'
+    }
+    return {
+      type,
+      innerChunks: []
+    }
+  }
+
+  function generateBrackets (n, chunks) {
+    if (n >= 200) {
+      return chunks
+    }
+
+    let rnd = Math.random()
+    if (rnd < 0.5) {
+      // add beside last chunk
+      chunks[chunks.length-1].innerChunks = chunks[chunks.length-1].innerChunks.concat(generateChunk())
+
+    } else {
+      chunks = chunks.concat(generateChunk())
+      // add inside last chunk
+    }
+    return generateBrackets(n+1, chunks)
+  }
+
+  function chunkToString(chunk) {
+    const bracketTypes = {
+      '{': '}',
+      '[': ']',
+      '(': ')',
+      '<': '>'
+    }
+
+    let inner = chunk.innerChunks.map(chunkToString).join('')
+
+    return chunk.type + inner + bracketTypes[chunk.type]
+  }
+  let brackets = 
+    (new Array(8).fill(0)).map(() => generateBrackets(0,[generateChunk()]).map(chunkToString).join(''))
+
+  let corruptSequences = brackets.map(x => {
+    let i = Math.random() * x.length/2
+    return x.substring(0,i) + x.substring(i+1)
+  })
+
+  return {statusCode: 200, body: JSON.stringify(corruptSequences), contentType: 'application/json'}
+}
+
+function notFoundResponse () {
+  return {statusCode: 404, body: '<h1>404: File not found</h1>', contentType: 'text/html'}
+}
+
+const endpoints = {
+  '/brackets': generateBracketsResponse,
+  '/data-series': generateDataSeriesResponse,
+}
+
+const server = http.createServer((req, res) => {
+  console.log(`${req.method} ${req.url}`)
+  let endpoint = endpoints[req.url] ?? notFoundResponse
+  let responseData = endpoint()
+
+  res.writeHead(responseData.statusCode, {'Content-Type': responseData.contentType})
+  res.end(responseData.body)
+})
+
+server.listen(8000, '0.0.0.0', () => {
+  console.log('server has started on 0.0.0.0:8000')
+})