save state in FilePersistence

src/Persistences/FilePersistence.mjs

@@ -1 +1,67 @@
+import fs from 'fs'
+import path from 'path'
+import BinaryDecoder from '../Util/Binary/Decoder.mjs'
+import BinaryEncoder from '../Util/Binary/Encoder.mjs'
+import { createMutualExclude } from '../Util/mutualExclude.mjs'
+import { encodeUpdate, encodeStructsDS, decodePersisted } from './decodePersisted.mjs'
 
+function createFilePath (persistence, roomName) {
+  return path.join(persistence.dir, roomName)
+}
+
+export default class FilePersistence {
+  constructor (dir) {
+    this.dir = dir
+    this._mutex = createMutualExclude()
+  }
+  saveUpdate (room, y, encodedStructs) {
+    return new Promise((resolve, reject) => {
+      this._mutex(() => {
+        const filePath = createFilePath(this, room)
+        const updateMessage = new BinaryEncoder()
+        encodeUpdate(y, encodedStructs, updateMessage)
+        fs.appendFile(filePath, Buffer.from(updateMessage.createBuffer()), (err) => {
+          if (err !== null) {
+            reject(err)
+          } else {
+            resolve()
+          }
+        })
+      }, resolve)
+    })
+  }
+  saveState (roomName, y) {
+    return new Promise((resolve, reject) => {
+      const encoder = new BinaryEncoder()
+      encodeStructsDS(y, encoder)
+      const filePath = createFilePath(this, roomName)
+      fs.writeFile(filePath, Buffer.from(encoder.createBuffer()), (err) => {
+        if (err !== null) {
+          reject(err)
+        } else {
+          resolve()
+        }
+      })
+    })
+  }
+  readState (roomName, y) {
+    // Check if the file exists in the current directory.
+    return new Promise((resolve, reject) => {
+      const filePath = path.join(this.dir, roomName)
+      fs.readFile(filePath, (err, data) => {
+        if (err !== null) {
+          resolve()
+          // reject(err)
+        } else {
+          this._mutex(() => {
+            console.info(`unpacking data (${data.length})`)
+            console.time('unpacking')
+            decodePersisted(y, new BinaryDecoder(data))
+            console.timeEnd('unpacking')
+          })
+          resolve()
+        }
+      })
+    })
+  }
+}