import session from 'express-session';
import fs from 'fs';
import path from 'path';

interface SessionFile
{
  session: session.SessionData;
  expires: number;
}

export class JsonSessionStore extends session.Store
{
  _dir: string;

  constructor( dir: string )
  {
    super();
    this._dir = dir;
    if ( ! fs.existsSync( dir ) ) fs.mkdirSync( dir, { recursive: true } );
  }

  _filePath( sid: string ): string
  {
    const safe = sid.replace( /[^a-zA-Z0-9_-]/g, '_' );
    return path.join( this._dir, safe + '.json' );
  }

  get( sid: string, callback: ( err: any, session?: session.SessionData ) => void ): void
  {
    try
    {
      const fp = this._filePath( sid );
      if ( ! fs.existsSync( fp ) ) { callback( null, null ); return; }
      const data: SessionFile = JSON.parse( fs.readFileSync( fp, 'utf8' ) );
      if ( Date.now() > data.expires ) { fs.unlinkSync( fp ); callback( null, null ); return; }
      callback( null, data.session );
    }
    catch ( e ) { callback( e ); }
  }

  set( sid: string, sessionData: session.SessionData, callback?: ( err?: any ) => void ): void
  {
    try
    {
      const fp = this._filePath( sid );
      const expires = sessionData.cookie?.expires
        ? new Date( sessionData.cookie.expires ).getTime()
        : Date.now() + 7 * 24 * 60 * 60 * 1000;
      const file: SessionFile = { session: sessionData, expires };
      fs.writeFileSync( fp, JSON.stringify( file ), 'utf8' );
      callback?.();
    }
    catch ( e ) { callback?.( e ); }
  }

  destroy( sid: string, callback?: ( err?: any ) => void ): void
  {
    try
    {
      const fp = this._filePath( sid );
      if ( fs.existsSync( fp ) ) fs.unlinkSync( fp );
      callback?.();
    }
    catch ( e ) { callback?.( e ); }
  }
}