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;
  }
}