/**
 * @file Node.js project detection and `.ccam/profile/` scaffolding (A3).
 * `detectNode` reads a repository's filesystem (package.json layout,
 * docker-compose.yml) without executing anything; `scaffoldProfile` turns
 * those facts into a working profile; `checkProfile` validates one. Only a
 * single preset (Node.js, single-service or a flat backend/+frontend/
 * monorepo) is detected — anything else is refused rather than guessed, per
 * `docs/superpowers/specs/2026-08-03-lane-profile-scaffolding-design.md`.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const path = require("node:path");

/**
 * A name safe to embed as literal text inside a generated shell script (an
 * npm script name, a docker-compose service name). Deliberately NOT applied
 * to profile.env `KEY=VALUE` values — those are parsed, never sourced, and
 * already safe by construction (see `lane-profile.js:parseEnvFile`). This
 * guard is only for names that get spliced into `.sh` file TEXT.
 */
const IDENTIFIER_RE = /^[\w.:-]+$/;

/** Read and parse a package.json, or null if it doesn't exist or is invalid JSON. */
function readPackageJson(dir) {
  try {
    return JSON.parse(fs.readFileSync(path.join(dir, "package.json"), "utf8"));
  } catch {
    return null;
  }
}

/**
 * First candidate script name present in `pkg.scripts` AND safe to embed in
 * shell text. Returns null (never a guess) when no candidate qualifies.
 *
 * @param {object|null} pkg - Parsed package.json.
 * @param {string[]} candidates - Script names in preference order.
 * @returns {string|null}
 */
function pickScript(pkg, candidates) {
  if (!pkg || typeof pkg.scripts !== "object" || !pkg.scripts) return null;
  for (const name of candidates) {
    if (typeof pkg.scripts[name] === "string" && IDENTIFIER_RE.test(name)) return name;
  }
  return null;
}

/**
 * Detect a Node.js project's layout and, for each service, which npm script
 * to run. Returns null when neither supported layout matches — the caller
 * must refuse rather than guess.
 *
 * @param {string} repoPath - Absolute path to the repository root.
 * @returns {object|null}
 */
function detectNode(repoPath) {
  const backendPkg = readPackageJson(path.join(repoPath, "backend"));
  const frontendPkg = readPackageJson(path.join(repoPath, "frontend"));

  if (backendPkg && frontendPkg) {
    return {
      layout: "monorepo",
      services: {
        backend: { dir: "backend", script: pickScript(backendPkg, ["start", "dev"]) },
        frontend: { dir: "frontend", script: pickScript(frontendPkg, ["preview", "dev"]) },
      },
      database: null,
      env: null,
    };
  }

  const rootPkg = readPackageJson(repoPath);
  if (rootPkg) {
    return {
      layout: "single-service",
      services: { app: { dir: ".", script: pickScript(rootPkg, ["start", "dev"]) } },
      database: null,
      env: null,
    };
  }

  return null;
}

module.exports = { IDENTIFIER_RE, readPackageJson, pickScript, detectNode };