import { KeyValueStorage } from "./basic";

/**
 * Key-value store, using local file-system
 */
export class NodeDirectoryStorage implements KeyValueStorage {
  readonly directory: string
  private checked = false

  constructor(appname: string) {
    if (typeof require === "undefined") {
      throw new Error("Storage only available in nodejs");
    }
    const path = require("path");
    this.directory = path.join(NodeDirectoryStorage.findUserData(), "tk-storage", appname);
  }

  /**
   * Find the writable user data directory
   */
  static findUserData(): string {
    const result = process.env.APPDATA || (process.platform == 'darwin' ? process.env.HOME + '/Library/Preferences' : process.env.HOME + "/.local/share");
    if (!result) {
      throw new Error("Cannot locate user data directory");
    }
    return result;
  }

  /**
   * Get the file path for a key
   */
  getPath(key: string): string {
    const path = require("path");
    return path.join(this.directory, key);
  }

  async get(key: string): Promise<string | null> {
    const fs = require("fs");
    return new Promise((resolve, reject) => {
      fs.readFile(this.getPath(key), { encoding: 'utf8' }, (err: any, data: string) => {
        resolve(err ? null : data);
      });
    });
  }

  async set(key: string, value: string | null): Promise<void> {
    const fs = require("fs");

    if (!this.checked) {
      await new Promise((resolve, reject) => {
        fs.mkdir(this.directory, { recursive: true }, (err: any) => {
          if (err && err.code !== 'EEXIST') {
            reject(err);
          } else {
            resolve();
          }
        });
      });
      this.checked = true;
    }

    return new Promise((resolve, reject) => {
      if (value === null) {
        fs.unlink(this.getPath(key), (err: any) => {
          if (err) {
            reject(err);
          } else {
            resolve();
          }
        });
      } else {
        fs.writeFile(this.getPath(key), value, { encoding: 'utf8' }, (err: any) => {
          if (err) {
            reject(err);
          } else {
            resolve();
          }
        });
      }
    });
  }
}