initial commit

Author: Eder Lima

.gitignore

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+**/node_modules

database.json

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+{
+  "people": [
+    { "_id": "3288e873-3bf4-406a-99b3-c6b1cbd61665", "name": "Eder", "age": 20 }
+  ]
+}

package.json

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+{
+  "name": "fsdb",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "scripts": {
+    "dev": "ts-node-dev --transpile-only --ignore-watch node_modules src/index.ts"
+  },
+  "devDependencies": {
+    "@types/node": "^18.0.0",
+    "@types/uuid": "^8.3.4",
+    "ts-node-dev": "^2.0.0",
+    "typescript": "^4.7.4"
+  },
+  "dependencies": {
+    "uuid": "^8.3.2"
+  }
+}

src/index.ts

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+import FileSystemDatabase, { collection } from './lib/index'
+import type { DatabaseRecord } from './lib/index'
+
+type Person = {
+  name: string
+  age: number
+}
+
+type DatabaseType = {
+  people: Array<DatabaseRecord<Person>>
+}
+
+FileSystemDatabase.fromFile<DatabaseType>('database.json').then(async (db) => {
+  const peopleRef = collection(db, 'people')
+
+  peopleRef.createDoc({
+    name: 'Eder',
+    age: 20,
+  })
+
+  const people = peopleRef.getDocs()
+
+  console.log(people)
+})

src/lib/index.ts

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+import { v4 } from 'uuid'
+import fsl from 'fs'
+import fsp from 'fs/promises'
+
+export type GenericDatabaseType = {
+  [k: string]: any[]
+}
+
+export type DatabaseRecord<T> = { _id: string } & T
+
+type ArrayElement<T> = T extends readonly (infer ElementType)[]
+  ? ElementType
+  : never
+
+export default class FileSystemDatabase<T extends GenericDatabaseType> {
+  private data: T | null
+
+  private constructor(private filename: string) {
+    this.data = null
+  }
+
+  static fromRef<T extends GenericDatabaseType>(
+    filename: string,
+    ref: T
+  ): FileSystemDatabase<T> {
+    const database = new FileSystemDatabase<T>(filename)
+    database.data = ref
+    return database
+  }
+
+  static async fromFile<T extends GenericDatabaseType>(
+    filename: string
+  ): Promise<FileSystemDatabase<T>> {
+    const database = new FileSystemDatabase<T>(filename)
+    await database.load()
+    return database
+  }
+
+  public getData(): T {
+    return this.data!
+  }
+
+  public async load(): Promise<void> {
+    if (!fsl.existsSync(this.filename)) {
+      this.data = {} as T
+
+      await fsp.writeFile(this.filename, JSON.stringify(this.data))
+    }
+
+    this.data = JSON.parse(await fsp.readFile(this.filename, 'utf8'))
+  }
+
+  public async save(): Promise<void> {
+    await fsp.writeFile(this.filename, JSON.stringify(this.data))
+  }
+
+  public async sync(): Promise<void> {
+    await this.load()
+  }
+}
+
+export const collection = <T extends GenericDatabaseType, K extends keyof T>(
+  database: FileSystemDatabase<T>,
+  path: K
+) => {
+  let data: T[K]
+  const dbRef = database.getData()[path]
+
+  if (dbRef) {
+    data = dbRef
+  } else {
+    ;(database.getData()[path] as any) = []
+    data = database.getData()[path]
+  }
+
+  type DocDTO = Omit<ArrayElement<T[K]>, '_id'>
+
+  return {
+    createDoc(doc: DocDTO): void {
+      const docRecord = {
+        _id: v4(),
+        ...doc,
+      }
+
+      data.push(docRecord)
+    },
+    deleteDoc(id: string) {
+      data.splice(
+        data.findIndex((r) => r._id === id),
+        1
+      )
+    },
+    updateDoc(id: string, record: Partial<DocDTO>) {
+      const index = data.findIndex((item) => item._id === id)
+
+      if (index === -1) {
+        throw new Error('Record not found')
+      }
+
+      Object.assign(data[index], record)
+    },
+    getDoc(id: string): ArrayElement<T[K]> | null {
+      return data.find((record) => record.id === id) || null
+    },
+    getDocs(): T[K] {
+      return data
+    },
+  }
+}

tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "esnext",
+    "module": "CommonJS",
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "strict": true,
+    "skipLibCheck": true,
+    "baseUrl": ".",
+    "outDir": "./dist"
+  }
+}