import { readdir, stat, open } from "node:fs/promises";
import { existsSync } from "node:fs";
import { join, relative } from "node:path";

/**
 * Marker chant writes at the top of files it generates (worker/workflow/activities
 * bootstrap for Temporal Ops, etc.). Discovery must not treat these as authored
 * infra source: they hold no Declarables, they self-execute on import (the worker
 * bootstrap calls `run()`), and they use runtime patterns the authored-source lint
 * rules forbid (dynamic `process.env[...]` access, spreads). Skipping them keeps
 * `chant lint`/`build` from importing or linting the tool's own output.
 */
export const GENERATED_MARKER = "Generated by chant — do not edit directly";

/** True when a file's header carries the {@link GENERATED_MARKER}. Reads only the head. */
async function isGeneratedFile(file: string): Promise<boolean> {
  let fh;
  try {
    fh = await open(file, "r");
    const { buffer, bytesRead } = await fh.read({ buffer: Buffer.alloc(256), position: 0 });
    return buffer.toString("utf8", 0, bytesRead).includes(GENERATED_MARKER);
  } catch {
    return false;
  } finally {
    await fh?.close();
  }
}

/**
 * Recursively find all TypeScript infrastructure files in a directory
 * @param path - The directory path to search
 * @returns Array of file paths to .ts files (excluding test files and chant-generated files)
 */
export async function findInfraFiles(path: string): Promise<string[]> {
  const files: string[] = [];
  let sourceRoot: string | null = null;

  async function scanDirectory(dir: string): Promise<void> {
    let entries;

    try {
      entries = await readdir(dir, { withFileTypes: true });
    } catch (error) {
      // Skip directories we can't read
      return;
    }

    for (const entry of entries) {
      const fullPath = join(dir, entry.name);

      // Skip node_modules
      if (entry.isDirectory() && entry.name === "node_modules") {
        continue;
      }

      if (entry.isDirectory()) {
        // Child project boundary — a directory with its own chant.config.ts
        // is a separate scope, but only if we've already found the project's
        // own source root. The first config directory is the source root, not
        // a child project.
        const configPath = join(fullPath, "chant.config.ts");
        if (existsSync(configPath)) {
          if (sourceRoot === null) {
            sourceRoot = fullPath;
          } else {
            continue;
          }
        }
        await scanDirectory(fullPath);
      } else if (entry.isFile()) {
        // Include only .ts files, exclude test files and chant-generated files
        if (
          entry.name.endsWith(".ts") &&
          !entry.name.endsWith(".test.ts") &&
          !entry.name.endsWith(".spec.ts") &&
          !(await isGeneratedFile(fullPath))
        ) {
          files.push(fullPath);
        }
      }
    }
  }

  await scanDirectory(path);
  return files;
}