#!/usr/bin/env node

/**
 * OmniRoute — Co-locate the LLMLingua-2 optional dependency closure into the standalone bundle.
 *
 * The compression "ultra" SLM tier (PR #4257) runs `@atjsh/llmlingua-2` +
 * `@huggingface/transformers` + `@tensorflow/tfjs` + `js-tiktoken` inside a worker thread
 * (`open-sse/services/compression/engines/llmlingua/onnxWorker.js`, shipped under `dist/`). These
 * are `optionalDependencies`: npm installs them into the ROOT `node_modules` on
 * `--include=optional`, but the Next.js standalone trace bundles ONLY `@huggingface/transformers`
 * (3.5.2, pinned) into `dist/node_modules` — it does NOT trace the optional, dynamically-imported
 * SLM packages.
 *
 * ## Why this matters (the instance-split bug)
 *
 * The worker lives under `dist/`, so its `import("@huggingface/transformers")` resolves
 * `dist/node_modules/@huggingface/transformers` (3.5.2) and the worker sets the model `cacheDir`
 * on THAT instance's `env`. But its `import("@atjsh/llmlingua-2")` walks past `dist/node_modules`
 * (no `@atjsh` there) up to the ROOT `node_modules`, and llmlingua-2's own
 * `import("@huggingface/transformers")` then resolves the ROOT transformers — a DIFFERENT instance.
 * The `cacheDir`/`localModelPath` config the worker set never reaches the instance llmlingua-2
 * actually uses, so the local model under `DATA_DIR/models/llmlingua` is never found and the SLM
 * tier silently fails-open (no compression). Worse, if the root transformers is a 4.x line,
 * llmlingua-2 throws on a tokenizer-API change (`decoder.decode` is undefined).
 *
 * ## The fix
 *
 * Co-locate the SLM optional dependency CLOSURE from the root `node_modules` into
 * `dist/node_modules` (NO-CLOBBER, so the pinned `dist` transformers 3.5.2 / onnxruntime / sharp
 * stay). Then the worker resolves `@atjsh/llmlingua-2` AND `@huggingface/transformers` from the
 * SAME `dist/node_modules` — a single 3.5.2 instance — so the env config applies and the local
 * model loads.
 *
 * `@huggingface/transformers` is intentionally NOT a closure seed: it is a PEER of
 * `@atjsh/llmlingua-2` (not a regular dependency) and is already bundled in `dist/node_modules`,
 * so the closure walk never reaches it and the no-clobber guard would skip it anyway.
 *
 * ## Validation (Hard Rule #18)
 *
 * Manual co-location of this exact closure on the production VPS produced real 54.8% compression
 * (11520 → 5203 chars) via real ONNX inference — both the default and the `modelPath` (PR #4257)
 * code paths. See the unit test for the closure-walk + no-clobber contract.
 *
 * Idempotent + fail-soft: skips when the optionals are absent (the common case — they are OPTIONAL)
 * or already co-located; a per-package copy failure only disables the SLM tier, which is itself
 * fail-open, so this never throws into the install.
 */

import { cpSync, existsSync, mkdirSync, readFileSync } from "node:fs";
import { createRequire } from "node:module";
import { dirname, join, sep } from "node:path";

/**
 * Entry packages of the SLM optional stack (the closure roots). `@huggingface/transformers` is
 * deliberately absent — it is the pinned instance already present in `dist/node_modules`.
 */
export const SEED_PACKAGES = ["@atjsh/llmlingua-2", "@tensorflow/tfjs", "js-tiktoken"];

/**
 * Compute the transitive dependency closure of `seeds` by walking each package's `dependencies` +
 * `optionalDependencies` from a `node_modules` directory. Packages that are not present in that
 * tree (e.g. peers provided elsewhere, like `@huggingface/transformers` in `dist`) are skipped —
 * the closure only contains packages that actually exist in `nodeModulesDir`.
 *
 * @param {string} nodeModulesDir absolute path to the source `node_modules`
 * @param {string[]} [seeds] closure roots (defaults to {@link SEED_PACKAGES})
 * @returns {string[]} package names in discovery order, seeds first
 */
export function computeDependencyClosure(nodeModulesDir, seeds = SEED_PACKAGES) {
  const closure = [];
  const seen = new Set();
  const stack = [...seeds];

  while (stack.length) {
    const name = stack.shift();
    if (seen.has(name)) continue;
    seen.add(name);

    const pkgDir = join(nodeModulesDir, name);
    if (!existsSync(pkgDir)) continue; // absent in this tree (peer provided elsewhere) — skip

    closure.push(name);

    let manifest;
    try {
      manifest = JSON.parse(readFileSync(join(pkgDir, "package.json"), "utf8"));
    } catch {
      continue; // unreadable/absent manifest — copy the dir but do not recurse
    }

    const deps = { ...manifest.dependencies, ...manifest.optionalDependencies };
    for (const dep of Object.keys(deps)) {
      if (!seen.has(dep)) stack.push(dep);
    }
  }

  return closure;
}

/**
 * A package in the target tree counts as PRESENT only when its entrypoint
 * resolves from inside that tree — the same contract the Dockerfile's
 * post-build guard enforces. Next's file tracing can materialize a package
 * PARTIALLY (the package.json lands, the files its `main` points at do not),
 * and a directory-level `existsSync` check then skips the package forever
 * while the runtime dies with "Cannot find module <pkg>/dist/index.js".
 *
 * @param {string} targetNodeModulesDir
 * @param {string} name
 * @returns {boolean}
 */
function isPackageIntact(targetNodeModulesDir, name) {
  if (!existsSync(join(targetNodeModulesDir, name))) return false;
  try {
    const probe = createRequire(
      join(targetNodeModulesDir, "__colocate_probe__.js")
    );
    const resolved = probe.resolve(name);
    // A resolution that walked past the target into an ancestor tree does not
    // prove the target copy is usable.
    return resolved.startsWith(targetNodeModulesDir + sep);
  } catch {
    return false;
  }
}

/**
 * Co-locate the SLM optional dependency closure from `<rootDir>/node_modules`
 * into a standalone bundle's `node_modules`.
 *
 * The default destination remains `<rootDir>/dist/node_modules` for the npm
 * postinstall path. Standalone builders, including Docker, may provide
 * `targetNodeModulesDir`.
 *
 * Packages already present in the destination are never overwritten. This
 * preserves the standalone bundle's pinned dependency instances while filling
 * dynamically imported packages that Next.js did not trace.
 *
 * @param {{
 *   rootDir: string,
 *   targetNodeModulesDir?: string,
 *   seeds?: string[],
 *   log?: (message: string) => void
 * }} opts
 * @returns {{ skipped: true, reason: string }
 *   | { skipped: false, copied: number, closure: number }}
 */
export function colocateLlmlinguaOptionals({
  rootDir,
  targetNodeModulesDir,
  seeds = SEED_PACKAGES,
  log = () => {},
}) {
  const rootNm = join(rootDir, "node_modules");
  const targetNm = targetNodeModulesDir ?? join(rootDir, "dist", "node_modules");

  if (!existsSync(targetNm)) {
    return {
      skipped: true,
      reason: targetNodeModulesDir
        ? "no target node_modules"
        : "no standalone dist/node_modules",
    };
  }

  // Only run when every requested closure root was installed.
  if (!seeds.every((seed) => existsSync(join(rootNm, seed)))) {
    return { skipped: true, reason: "SLM optionals not installed at root" };
  }

  const closure = computeDependencyClosure(rootNm, seeds);

  // Check the complete closure rather than only the entry package, and judge
  // presence by entrypoint integrity — a partially traced directory (see
  // isPackageIntact) must still receive its missing files.
  if (
    closure.length > 0 &&
    closure.every((name) => isPackageIntact(targetNm, name))
  ) {
    return { skipped: true, reason: "already co-located" };
  }

  let copied = 0;

  for (const name of closure) {
    const dest = join(targetNm, name);
    if (isPackageIntact(targetNm, name)) continue;

    try {
      mkdirSync(dirname(dest), { recursive: true });
      // force:false merges into a partially traced directory: files the trace
      // already materialized are kept, missing ones (the package payload) are
      // filled in from the root tree.
      cpSync(join(rootNm, name), dest, {
        recursive: true,
        force: false,
        errorOnExist: false,
      });
      copied++;
    } catch (err) {
      log(
        `  ⚠️  LLMLingua optional co-location failed for ${name}: ${err.message}`
      );
    }
  }

  if (copied > 0) {
    log(
      `  ✅ Co-located ${copied} LLMLingua SLM optional package(s) into standalone node_modules.\n`
    );
  }

  return { skipped: false, copied, closure: closure.length };
}