import { createHash } from 'node:crypto';
import { mkdir, readFile, rename, writeFile } from 'node:fs/promises';
import { dirname, join } from 'node:path';
import { DeploymentError } from './git-service.mjs';

export class UploadStore {
  constructor(config) {
    this.root = config.uploadRoot;
    this.statePath = config.uploadStatePath;
    this.queue = Promise.resolve();
    this.uploads = [];
  }

  async initialize() {
    await mkdir(this.root, { recursive: true });
    await mkdir(dirname(this.statePath), { recursive: true });
    try {
      const saved = JSON.parse(await readFile(this.statePath, 'utf8'));
      this.uploads = Array.isArray(saved.uploads) ? saved.uploads : [];
    } catch (error) {
      if (error.code !== 'ENOENT') throw error;
    }
  }

  store({ requestKey, client, filename, body }) {
    const operation = this.queue.then(async () => {
      if (!/^[a-z0-9][a-z0-9_-]{1,31}$/.test(client)
        || !/^[a-f0-9]{32}\.(?:avif|webp|jpg|png|gif)$/.test(filename)) {
        throw new DeploymentError('Invalid upload path', 400);
      }
      const relativePath = `${client}/${filename}`;
      const path = `icons/users/${relativePath}`;
      const digest = createHash('sha256').update(body).digest('hex');
      const previous = this.uploads.find((upload) => upload.key === requestKey);
      if (previous) {
        if (previous.path !== path || previous.digest !== digest) {
          throw new DeploymentError('Upload request ID was already used', 409);
        }
        return { duplicate: true, path: previous.path };
      }
      const destination = join(this.root, relativePath);
      await mkdir(dirname(destination), { recursive: true });
      try {
        await writeFile(destination, body, { flag: 'wx', mode: 0o644 });
      } catch (error) {
        if (error.code !== 'EEXIST' || !(await readFile(destination)).equals(body)) {
          throw new DeploymentError('Upload path already exists', 409);
        }
      }
      this.uploads = [...this.uploads.slice(-999), { key: requestKey, path, digest }];
      await this.#save();
      return { duplicate: false, path };
    });
    this.queue = operation.catch(() => undefined);
    return operation;
  }

  async #save() {
    const temporary = `${this.statePath}.tmp-${process.pid}`;
    await writeFile(temporary, JSON.stringify({ uploads: this.uploads }, null, 2), { mode: 0o600 });
    await rename(temporary, this.statePath);
  }
}