import { existsSync, readdirSync, statSync } from "node:fs";
import { join } from "node:path";

const IGNORED_DIRS = new Set([
  "node_modules",
  ".git",
  "dist",
  "out",
  ".next",
  "__pycache__",
  ".cache",
  ".turbo",
  "coverage",
  ".vscode",
  ".idea",
  "target",
  "build",
  ".gradle",
  "vendor",
]);

export async function collectProjectContext(repoRoot: string): Promise<{
  readme: string | null;
  packageDescription: string | null;
  structure: string | null;
}> {
  let readme: string | null = null;
  let packageDescription: string | null = null;
  let structure: string | null = null;

  for (const name of ["README.md", "README.txt", "README.rst", "README"]) {
    const filePath = join(repoRoot, name);
    if (existsSync(filePath)) {
      try {
        const content = await Bun.file(filePath).text();
        readme =
          content.length > 1500
            ? content.substring(0, 1500) + "\n... (truncated)"
            : content;
      } catch {}
      break;
    }
  }

  const pkgPath = join(repoRoot, "package.json");
  if (existsSync(pkgPath)) {
    try {
      const pkg = (await Bun.file(pkgPath).json()) as { description?: string };
      if (pkg.description) {
        packageDescription = pkg.description;
      }
    } catch {}
  }

  try {
    const entries = readdirSync(repoRoot)
      .filter((name) => !IGNORED_DIRS.has(name) && !name.startsWith("."))
      .map((name) => {
        try {
          return statSync(join(repoRoot, name)).isDirectory()
            ? `${name}/`
            : name;
        } catch {
          return name;
        }
      });
    if (entries.length > 0) {
      structure = entries.join(", ");
    }
  } catch {}

  return { readme, packageDescription, structure };
}