import fs from "fs-extra";
import path from "path";
import { diffLines } from "diff";

/**
 * Utility class used to detect schema changes between generations.
 */
export class TypeDiffer {
  /**
   * Determine if two JSON schema objects differ.
   */
  hasSchemaChanges(prev: any, next: any): boolean {
    return JSON.stringify(prev) !== JSON.stringify(next);
  }

  /**
   * Produce a diff of files between two directories.
   */
  async compareDirectories(dirA: string, dirB: string) {
    const diffs: { file: string; message: string }[] = [];
    const filesA = await fs.readdir(dirA);
    for (const file of filesA) {
      const aPath = path.join(dirA, file);
      const bPath = path.join(dirB, file);
      if (!fs.existsSync(bPath)) {
        diffs.push({ file, message: "missing in B" });
        continue;
      }
      const [aContent, bContent] = await Promise.all([
        fs.readFile(aPath, "utf-8"),
        fs.readFile(bPath, "utf-8"),
      ]);
      if (diffLines(aContent, bContent).some((d) => d.added || d.removed)) {
        diffs.push({ file, message: "content differs" });
      }
    }
    return diffs;
  }
}