app: model: Add Hub.js

app/model/Hub.js

+/*
+ * Tugas Besar 3 WBD - AMEN
+ */
+
+'use strict'
+
+// Utilities.
+
+let index = function (id, locations) {
+  for (let location of locations) {
+    let ids = this.locations[location]
+
+    if (!ids) {
+      ids = new Set()
+      this.locations[location] = ids
+    }
+
+    ids.add(id)
+  }
+}
+
+let unindex = function (id, locations) {
+  for (let location of locations) {
+    let ids = this.locations[location]
+
+    if (ids) {
+      ids.delete(id)
+    }
+  }
+}
+
+// Main routine.
+
+class Hub {
+  constructor () {
+    this.drivers = {}
+    this.locations = {}
+
+    let indexLambda = index.bind(this)
+    let unindexLambda = unindex.bind(this)
+
+    this.wait = (id, locations) => {
+      let rejectCallback = null
+
+      let promise = (async () => {
+        let promise = new Promise((resolve, reject) => {
+          this.drivers[id] = {
+            resolve: resolve,
+            reject: reject
+          }
+
+          // Keep reject callback.
+          rejectCallback = reject
+
+          // Index locations.
+          indexLambda(id, locations)
+        })
+
+        try {
+          let userId = await promise
+          return userId
+        } finally {
+          // Remove indexed locations.
+          unindexLambda(id, locations)
+        }
+      })()
+
+      return {
+        promise: promise,
+
+        reject (err) {
+          rejectCallback(err)
+        }
+      }
+    }
+  }
+
+  filter (location) {
+    return this.locations[location]
+  }
+
+  pick (id, userId) {
+    this.drivers[id].resolve(userId)
+  }
+}
+
+module.exports = Hub