#!/usr/bin/env node

/**
 * Rebuilds the bundle-owned config directory inside the Pi agent directory.
 *
 * Every piece of bundle-owned, rebuildable state lives under
 * `<agentDir>/my-pi/` (policy files, Tool Search config, the system prompt
 * cover, permission logs). `config/bundle-manifest.json` is the authoritative
 * source→target list: this helper builds the full tree in a sibling temp
 * directory, deletes any existing `my-pi/` wholesale — no backup — and renames
 * the fresh tree into place, so a rebuild can never half-apply.
 *
 * Nothing outside `my-pi/` is read or removed; leftovers at the old locations
 * are ignored rather than migrated.
 */

import { realpathSync } from "node:fs";
import { chmod, copyFile, lstat, mkdir, readFile, rename, rm, unlink } from "node:fs/promises";
import { dirname, isAbsolute, join, resolve, sep } from "node:path";
import { fileURLToPath } from "node:url";

const scriptPath = fileURLToPath(import.meta.url);
const bundleRoot = dirname(dirname(scriptPath));
export const BUNDLE_ROOT = bundleRoot;
export const MANIFEST_PATH = join(bundleRoot, "config", "bundle-manifest.json");

/** Thrown for an unusable agentDir argument; maps to CLI exit code 2. */
export class RebuildUsageError extends Error {}

function isObject(value) {
  return value !== null && typeof value === "object" && !Array.isArray(value);
}

/**
 * Load and validate the manifest.
 *
 * Every source must be a readable repo-relative file and every target a
 * relative path that stays inside the bundle directory — a `..` or absolute
 * target would escape `my-pi/` during the rebuild, so it is rejected before
 * anything is touched.
 *
 * @param {string} manifestPath
 * @returns {Promise<{ directory: string, files: Array<{ source: string, target: string }> }>}
 */
export async function loadManifest(manifestPath) {
  let manifest;
  try {
    manifest = JSON.parse(await readFile(manifestPath, "utf8"));
  } catch (error) {
    throw new Error(
      `cannot read bundle manifest at ${manifestPath}: ${
        error instanceof Error ? error.message : String(error)
      }`,
    );
  }
  if (!isObject(manifest) || manifest.directory !== "my-pi" || !Array.isArray(manifest.files)) {
    throw new Error(`bundle manifest at ${manifestPath} is malformed`);
  }

  const files = manifest.files.map((entry, index) => {
    if (!isObject(entry) || typeof entry.source !== "string" || typeof entry.target !== "string") {
      throw new Error(`bundle manifest entry ${index} lacks source/target strings`);
    }
    const directoryBase = resolve(manifest.directory);
    const resolved = resolve(directoryBase, entry.target);
    if (
      isAbsolute(entry.target) ||
      resolved === directoryBase ||
      !resolved.startsWith(directoryBase + sep)
    ) {
      throw new Error(
        `bundle manifest target ${entry.target} escapes the ${manifest.directory}/ directory`,
      );
    }
    const sourcePath = join(bundleRoot, entry.source);
    return { source: entry.source, sourcePath, target: entry.target };
  });

  // Fail before deleting anything: a missing source must not wipe the live tree.
  for (const file of files) {
    try {
      await readFile(file.sourcePath);
    } catch (error) {
      throw new Error(
        `cannot read manifest source ${file.source}: ${
          error instanceof Error ? error.message : String(error)
        }`,
      );
    }
  }
  return { directory: manifest.directory, files };
}

/**
 * Rebuild `<agentDir>/my-pi` from the bundle manifest.
 *
 * The tree is staged in `<agentDir>/.my-pi.rebuild-<pid>-<rand>` (dirs 0700,
 * files 0600), then the existing `my-pi` is removed — a symlink is unlinked,
 * never followed — and the stage is renamed into place. Any failure removes
 * the stage and throws.
 *
 * @param {string} agentDir - Absolute Pi agent directory.
 * @param {{ manifestPath?: string }} [options]
 * @returns {Promise<{ targetDir: string }>}
 */
export async function rebuildBundleConfig(agentDir, { manifestPath = MANIFEST_PATH } = {}) {
  if (typeof agentDir !== "string" || agentDir.length === 0 || !isAbsolute(agentDir)) {
    throw new RebuildUsageError("rebuild-bundle-config requires an absolute agentDir argument");
  }
  const manifest = await loadManifest(manifestPath);

  const targetDir = join(agentDir, manifest.directory);
  const stageDir = join(
    agentDir,
    `.${manifest.directory}.rebuild-${process.pid}-${Math.random().toString(16).slice(2)}`,
  );

  try {
    await mkdir(agentDir, { recursive: true, mode: 0o700 });
    await mkdir(stageDir, { mode: 0o700 });
    for (const file of manifest.files) {
      const destination = join(stageDir, file.target);
      await mkdir(dirname(destination), { recursive: true, mode: 0o700 });
      // copyFile keeps the source mode on some platforms; pin owner-only.
      await copyFile(file.sourcePath, destination);
      await chmod(destination, 0o600);
    }

    // Never follow a symlink: unlink the link itself, never its target.
    try {
      const stats = await lstat(targetDir);
      if (stats.isSymbolicLink()) {
        await unlink(targetDir);
      } else {
        await rm(targetDir, { recursive: true, force: true });
      }
    } catch (error) {
      if (error?.code !== "ENOENT") throw error;
    }

    await rename(stageDir, targetDir);
    return { targetDir };
  } catch (error) {
    await rm(stageDir, { recursive: true, force: true }).catch(() => {});
    throw error;
  }
}

function isMainModule() {
  if (!process.argv[1]) return false;
  try {
    return fileURLToPath(import.meta.url) === realpathSync(process.argv[1]);
  } catch {
    return false;
  }
}

async function main() {
  const agentDir = process.argv[2] ?? "";
  if (agentDir.length === 0 || !isAbsolute(agentDir)) {
    console.error("usage: rebuild-bundle-config.mjs <absolute-agent-dir>");
    process.exitCode = 2;
    return;
  }
  const { targetDir } = await rebuildBundleConfig(agentDir);
  process.stdout.write(`rebuilt:${targetDir}\n`);
}

if (isMainModule()) {
  main().catch((error) => {
    console.error(error instanceof Error ? error.message : String(error));
    process.exitCode = error instanceof RebuildUsageError ? 2 : 1;
  });
}