import fs from "node:fs/promises";
import path from "node:path";
import { RELATIVE_ASSETS_DIR } from "../../constants/media";
import { listExportUserMediaAssets } from "./build-data";

type ExportFileAsset = {
  storageKey: string;
};

export type BuildExportFilesResult = {
  files: Array<{ file: string; bytes: number }>;
  missingCount: number;
};

function resolveAssetsBaseDir(): string {
  return path.resolve(process.cwd(), RELATIVE_ASSETS_DIR);
}

export async function buildExportMediaFiles(params: {
  userId: number;
  cutoffAt: Date;
  outputFilesDir: string;
}): Promise<BuildExportFilesResult> {
  await fs.mkdir(params.outputFilesDir, { recursive: true });

  const mediaAssets: ExportFileAsset[] = await listExportUserMediaAssets({
    userId: params.userId,
    cutoffAt: params.cutoffAt,
  });
  const assetsBaseDir = resolveAssetsBaseDir();
  let missingCount = 0;
  const files: Array<{ file: string; bytes: number }> = [];

  for (const asset of mediaAssets) {
    const key = asset.storageKey;
    if (!key || key.includes("..") || path.isAbsolute(key)) {
      missingCount += 1;
      continue;
    }

    const fromPath = path.resolve(assetsBaseDir, key);
    const toPath = path.resolve(params.outputFilesDir, key);
    const relativeOutputPath = `files/${key}`;
    await fs.mkdir(path.dirname(toPath), { recursive: true });

    try {
      await fs.copyFile(fromPath, toPath);
      const stat = await fs.stat(toPath);
      files.push({ file: relativeOutputPath, bytes: stat.size });
    } catch (error) {
      if ((error as NodeJS.ErrnoException).code === "ENOENT") {
        missingCount += 1;
        continue;
      }
      throw error;
    }
  }

  return {
    files,
    missingCount,
  };
}