initial commit

database.ts

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+import { Entry, Table } from "./table.ts";
+
+type Tables = Record<string, Table<Entry>>;
+
+export class Database {
+  private constructor(private filePath: string, private tables: Tables) {}
+
+  static async load(
+    filePath: string,
+    ifEmpty: (database: Database) => Promise<void>,
+  ): Promise<Database> {
+    const database = new Database(filePath, {});
+
+    try {
+      const data = await Deno.readTextFile(filePath);
+      const parsedData = JSON.parse(data);
+      for (const tableName in parsedData) {
+        const table = new Table(() => database.saveDatabase());
+        table.entries = parsedData[tableName].entries;
+        table.autoIncrementId = parsedData[tableName].autoIncrementId;
+        database.tables[tableName] = table;
+      }
+    } catch (_) {
+      // File doesn't exists already
+      await ifEmpty(database);
+    }
+
+    return database;
+  }
+
+  private async saveDatabase() {
+    const dataToSave: {
+      [name: string]: { entries: Entry[]; autoIncrementId: number };
+    } = {};
+    for (const tableName in this.tables) {
+      dataToSave[tableName] = {
+        entries: this.tables[tableName].entries,
+        autoIncrementId: this.tables[tableName].autoIncrementId,
+      };
+    }
+    await Deno.writeTextFile(
+      this.filePath,
+      JSON.stringify(dataToSave),
+    );
+  }
+
+  async createTable(name: string) {
+    if (this.tables[name]) {
+      throw new Error(`Table ${name} already exists.`);
+    }
+    this.tables[name] = new Table(this.saveDatabase.bind(this));
+    await this.saveDatabase();
+  }
+
+  getTable(name: string): Table<Entry> {
+    const table = this.tables[name];
+    if (!table) {
+      throw new Error(`Table ${name} does not exist.`);
+    }
+    return table;
+  }
+}

mod.ts

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+export * from "./database.ts";
+export * from "./table.ts";

readme.md

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+# Simplistic JSON database
+
+- Save / load all data from one JSON file
+- Automatically saves data after any modifications (create / update / delete)
+- Autoincremented ids
+
+## Usage
+
+```typescript
+import { Database } from "./database.ts";
+import { Table } from "./table.ts";
+
+const database = await Database.load("./data.json", async (emptyDatabase) => {
+  await emptyDatabase.createTable("foo");
+  await emptyDatabase.createTable("bar");
+  await emptyDatabase.createTable("baz");
+});
+
+const fooTable = await database.getTable("foo") as Table<{
+  id: number;
+  name: string;
+}>;
+
+const insertedEntry = await fooTable.insert({ name: "Hello world" });
+const updatedEntries = await fooTable.update(
+  (candidat) => candidat.id === insertedEntry.id,
+  (entry) => entry.name = "Goodbye",
+);
+const deletedEntries = await fooTable.delete(() => true);
+```

table.ts

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+export type Entry = { id: number };
+
+export class Table<TableEntry extends Entry> {
+  entries: TableEntry[] = [];
+  autoIncrementId: number = 1;
+
+  constructor(private saveCallback: () => Promise<void>) {}
+
+  private generateId(): number {
+    return this.autoIncrementId++;
+  }
+
+  async insert(record: Omit<TableEntry, "id">) {
+    const recordWithId = { ...record, id: this.generateId() } as TableEntry;
+    this.entries.push(recordWithId);
+    await this.saveCallback();
+    return recordWithId;
+  }
+
+  select(predicate: (entry: TableEntry) => boolean): TableEntry[] {
+    return this.entries.filter(predicate);
+  }
+
+  async update(
+    predicate: (entry: TableEntry) => boolean,
+    updateFn: (entry: TableEntry) => void,
+  ) {
+    const updated: TableEntry[] = [];
+    this.entries.forEach((record) => {
+      if (predicate(record)) {
+        updateFn(record);
+        updated.push(record);
+      }
+    });
+    await this.saveCallback();
+    return updated;
+  }
+
+  async delete(predicate: (entry: TableEntry) => boolean) {
+    const deletedEntries = this.entries.filter(predicate);
+    this.entries = this.entries.filter((record) => !predicate(record));
+    await this.saveCallback();
+    return deletedEntries;
+  }
+}