import fs from "node:fs";
import path from "node:path";
import buildDebug from "debug";
import convertSourceMap from "convert-source-map";
import type { SourceMapConverter } from "convert-source-map";

const debug = buildDebug("babel:transform:file");

// Revised from https://github.com/sindresorhus/find-up-simple/blob/f10133c55dcbf36f84a246c6f1bbfed178dcb774/index.js#L36
// for Node.js 6 compatibility
function findUpSync(
  name: string,
  {
    cwd,
    stopAt,
  }: {
    cwd?: string;
    stopAt?: string;
  } = {},
) {
  let directory = path.resolve(cwd || "");
  const { root } = path.parse(directory);
  stopAt = path.resolve(directory, stopAt || root);
  const isAbsoluteName = path.isAbsolute(name);

  while (directory) {
    const filePath = isAbsoluteName ? name : path.join(directory, name);

    try {
      const stats = fs.statSync(filePath);
      if (stats.isFile()) {
        return filePath;
      }
    } catch (_) {}

    if (directory === stopAt || directory === root) {
      break;
    }

    directory = path.dirname(directory);
  }
}

function getInputMapPath(
  filename: string,
  root: string,
  inputMapURL: string,
): string | null {
  const inputFileDir = path.dirname(filename);
  const inputMapPath = path.resolve(inputFileDir, inputMapURL);
  const relativeToInputFileDir = path.relative(inputFileDir, inputMapPath);

  if (
    relativeToInputFileDir.startsWith("..") ||
    path.isAbsolute(relativeToInputFileDir)
  ) {
    const inputPackageJSONPath = findUpSync("package.json", {
      cwd: inputFileDir,
      stopAt: root,
    });
    const inputFileRoot = inputPackageJSONPath
      ? path.dirname(inputPackageJSONPath)
      : root;
    const relativeInputMapPath = path.relative(inputFileRoot, inputMapPath);
    if (
      relativeInputMapPath.startsWith("..") ||
      path.isAbsolute(relativeInputMapPath)
    ) {
      debug(
        `discarding input sourcemap "${inputMapPath}" outside of package root "${inputFileRoot}"`,
      );
      return null;
    }
  }
  return inputMapPath;
}

export default function readInputSourceMapFile(
  filename: string,
  root: string,
  inputMapURL: string,
): SourceMapConverter | null {
  const inputMapPath = getInputMapPath(filename, root, inputMapURL);
  if (inputMapPath) {
    const inputMapContent = fs.readFileSync(inputMapPath, "utf8");
    return convertSourceMap.fromJSON(inputMapContent);
  }
  return null;
}