import path from "node:path";
import fs from "node:fs/promises";

/**
 * A Vite plugin that resolves file content based on the first line.
 * This is a common case in repositories created on MacOS or Linux using symlinks.
 * When those get checked out under Windows, these symlinks are checked out as regular
 * files, just containig the target path of the original symlink. This plugin checks each import
 * if it contains a valid path on the first line load that instead transparently.
 * Otherwise, it loads the content of the original file.
 */
export function gitSymlinkResolverPlugin() {
  const supportedExtensions = [".js", ".jsx", ".ts", ".tsx", ".css", ".scss", ".less"];

  return {
    name: "vite-plugin-git-symlink-resolver",
    enforce: "pre",

    async resolveId(source, importer, options) {
      if (!importer || source.startsWith("\0") || source.includes("node_modules")) {
        return null;
      }
      const importedFilePath = path.resolve(path.dirname(importer), source);
      const ext = path.extname(importedFilePath);
      if (!supportedExtensions.includes(ext)) {
        return null;
      }
      return `\0git-symlink-resolver:${importedFilePath}`;
    },

    async load(id) {
      if (id.startsWith("\0git-symlink-resolver:")) {
        const originalFilePath = id.replace("\0git-symlink-resolver:", "");

        try {
          const originalFileContent = await fs.readFile(originalFilePath, "utf-8");
          const firstLine = originalFileContent.split("\n")[0]?.trim();

          if (firstLine) {
            const potentialRedirectPath = path.resolve(path.dirname(originalFilePath), firstLine);

            try {
              const stats = await fs.stat(potentialRedirectPath);
              if (stats.isFile()) {
                console.log(
                  `[GitSymlinkResolver] Redirecting ${path.relative(process.cwd(), originalFilePath)} to ${path.relative(process.cwd(), potentialRedirectPath)}`
                );
                return await fs.readFile(potentialRedirectPath, "utf-8");
              }
            } catch (e) {
              console.log(`[GitSymlinkResolver] File ${originalFilePath} isn't a redirect`, e);
            }
          }
          return originalFileContent;
        } catch (error) {
          console.error(`[GitSymlinkResolver] Error reading original file ${path.relative(process.cwd(), originalFilePath)}:`, error);
          return null;
        }
      }

      return null;
    }
  };
}