import { Injectable, OnModuleInit } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { createReadStream, promises as fs } from 'fs';
import * as path from 'path';
import type { Readable } from 'stream';

@Injectable()
export class LocalFileStorage implements OnModuleInit {
  private readonly root: string;

  constructor(private readonly config: ConfigService) {
    this.root =
      this.config.get<string>('UPLOAD_DIR')?.trim() ||
      path.join(process.cwd(), 'uploads');
  }

  async onModuleInit() {
    await fs.mkdir(this.root, { recursive: true });
  }

  absolutePath(storageKey: string): string {
    const resolved = path.resolve(this.root, storageKey);
    if (!resolved.startsWith(path.resolve(this.root))) {
      throw new Error('Invalid storage key');
    }
    return resolved;
  }

  async save(storageKey: string, buffer: Buffer): Promise<void> {
    const abs = this.absolutePath(storageKey);
    await fs.mkdir(path.dirname(abs), { recursive: true });
    await fs.writeFile(abs, buffer);
  }

  async remove(storageKey: string): Promise<void> {
    const abs = this.absolutePath(storageKey);
    try {
      await fs.unlink(abs);
    } catch (err) {
      const code = (err as NodeJS.ErrnoException).code;
      if (code !== 'ENOENT') throw err;
    }
  }

  openReadStream(storageKey: string): Readable {
    return createReadStream(this.absolutePath(storageKey));
  }
}