#!/usr/bin/env python3
# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved.
"""Guard against breaking npm dependency removals in studio/frontend.

Diffs the current package.json against a git base, finds every package
that was removed, and confirms each is no longer referenced anywhere
in the repo. If a removed package is still imported and is not
transitively resolvable through the new lockfile, exits non-zero with
file:line citations.

Usage:
  python scripts/check_frontend_dep_removal.py
  python scripts/check_frontend_dep_removal.py --base origin/main
  python scripts/check_frontend_dep_removal.py --base HEAD~1
  python scripts/check_frontend_dep_removal.py --base-pkg PATH --head-lock PATH

Exit codes:
  0  every removed dep is safe (no source refs or still resolvable)
  1  at least one removed dep is referenced and not resolvable
  2  invocation error (bad args, missing file, git error)
"""

from __future__ import annotations

import argparse
import json
import os
import re
import subprocess
import sys
from dataclasses import dataclass
from pathlib import Path

REPO_ROOT = Path(__file__).resolve().parent.parent
FRONTEND_PKG = "studio/frontend/package.json"
FRONTEND_LOCK = "studio/frontend/package-lock.json"

DEP_FIELDS = (
    "dependencies",
    "devDependencies",
    "peerDependencies",
    "optionalDependencies",
)

# Sources where seeing a package name does NOT count as usage.
EXPECTED_NOISE_FILES = {
    "studio/frontend/package.json",
    "studio/frontend/package-lock.json",
    "studio/backend/core/data_recipe/oxc-validator/package.json",
    "studio/backend/core/data_recipe/oxc-validator/package-lock.json",
}

# Only quoted-string occurrences in these file types can be module specifiers.
JS_LIKE_EXT = re.compile(
    r"\.(ts|tsx|js|jsx|mjs|cjs|html|htm|css|scss|sass|json|jsonc)$"
)
# Files where JS-syntactic import patterns (static/dynamic/require/re-export)
# could be a real module reference. Markdown gets a separate gate (.mdx is
# real ESM; .md code fences are not).
SCRIPT_LIKE_EXT = re.compile(r"\.(ts|tsx|js|jsx|mjs|cjs|mdx)$")
STYLE_EXT = re.compile(r"\.(css|scss|sass)$")
HTML_EXT = re.compile(r"\.(html|htm)$")
TS_LIKE_EXT = re.compile(r"\.(ts|tsx|mts|cts|mdx)$")
# Files where a removed package's CLI binary could be invoked (npx, bunx,
# yarn dlx, pnpm exec, or a bare `pkg --flag` shell call).
COMMAND_LIKE_EXT = re.compile(r"(\.(ya?ml|sh|ps1|bat)$|(^|/)Dockerfile[^/]*$)")

GREP_INCLUDES = [
    "--include=*.ts",
    "--include=*.tsx",
    "--include=*.js",
    "--include=*.jsx",
    "--include=*.mjs",
    "--include=*.cjs",
    "--include=*.html",
    "--include=*.htm",
    "--include=*.css",
    "--include=*.scss",
    "--include=*.sass",
    "--include=*.json",
    "--include=*.jsonc",
    "--include=*.md",
    "--include=*.mdx",
    "--include=*.py",
    "--include=*.rs",
    "--include=*.toml",
    "--include=*.yml",
    "--include=*.yaml",
    "--include=*.sh",
    "--include=*.ps1",
    "--include=*.bat",
    "--include=Dockerfile*",
]
GREP_EXCLUDES = [
    "--exclude-dir=node_modules",
    "--exclude-dir=dist",
    "--exclude-dir=.git",
    "--exclude-dir=__pycache__",
    "--exclude-dir=target",
    "--exclude-dir=.next",
    "--exclude-dir=build",
    "--exclude-dir=.venv",
    "--exclude-dir=venv",
]

# A pip-installed playwright reference is the PyPI package, not npm.
PIP_PLAYWRIGHT = re.compile(
    r"(pip\s+install\s+['\"]?playwright"
    r"|python\s+-m\s+playwright"
    r"|from\s+playwright"
    r"|^\s*import\s+playwright)"
)


@dataclass
class Hit:
    file: str
    line: int
    kind: str
    snippet: str


def run(cmd: list[str], cwd: Path | None = None) -> str:
    """Run a command, return stdout. On non-zero exit, return ''."""
    res = subprocess.run(
        cmd,
        cwd = cwd or REPO_ROOT,
        stdout = subprocess.PIPE,
        stderr = subprocess.PIPE,
        text = True,
    )
    return res.stdout if res.returncode == 0 else ""


def read_pkg_at(base: str, path: str) -> dict:
    """Read JSON at `base:path` via git show. Empty dict if missing."""
    out = run(["git", "show", f"{base}:{path}"])
    if not out.strip():
        return {}
    return json.loads(out)


def read_pkg_file(path: Path) -> dict:
    if not path.exists():
        return {}
    return json.loads(path.read_text(encoding = "utf-8"))


def all_decl_names(pkg: dict) -> set[str]:
    names: set[str] = set()
    for field in DEP_FIELDS:
        names.update((pkg.get(field) or {}).keys())
    return names


def _resolve_install_path(parent_path: str, name: str, pkgs: dict) -> str | None:
    """Walk up the nested node_modules chain from `parent_path` to find
    where `name` actually resolves. Mirrors Node module resolution.
    """
    parts = parent_path.split("/node_modules/")
    for i in range(len(parts), 0, -1):
        prefix = "/node_modules/".join(parts[:i])
        trial = (prefix + "/node_modules/" if prefix else "node_modules/") + name
        if trial in pkgs:
            return trial
    if f"node_modules/{name}" in pkgs:
        return f"node_modules/{name}"
    return None


def _deps_of(meta: dict) -> dict:
    """Deps npm actually installs. Optional peers are skipped: npm only
    installs them when another package declares the same dep, so for the
    purpose of "is this package still reachable" they cannot keep a
    removed top-level dep alive on their own.
    """
    out = {}
    for field in ("dependencies", "optionalDependencies"):
        out.update(meta.get(field) or {})
    peer_meta = meta.get("peerDependenciesMeta") or {}
    for name, spec in (meta.get("peerDependencies") or {}).items():
        if (peer_meta.get(name) or {}).get("optional"):
            continue
        out[name] = spec
    return out


def reachable_from_head(head_pkg: dict, lock: dict) -> set[str]:
    """BFS the lockfile dep graph starting from `head_pkg`'s top-level
    declared deps. Returns the set of lockfile install paths that survive.
    Stale lockfile entries (orphaned by the new package.json) are excluded.
    """
    pkgs = lock.get("packages", {})
    if not pkgs:
        return set()
    roots = all_decl_names(head_pkg)
    seen: set[str] = set()
    frontier: list[str] = []
    for name in roots:
        p = _resolve_install_path("", name, pkgs)
        if p:
            frontier.append(p)
    while frontier:
        path = frontier.pop()
        if path in seen:
            continue
        seen.add(path)
        meta = pkgs.get(path, {})
        for dep_name in _deps_of(meta):
            p = _resolve_install_path(path, dep_name, pkgs)
            if p and p not in seen:
                frontier.append(p)
    return seen


def classify(pkg: str, file: str, content: str) -> str | None:
    """Return why `content` references `pkg`, or None.

    `content` may span multiple lines (for multi-line imports/exports);
    each pattern uses re.DOTALL where it matters. The bare-spec
    regexes use a word-boundary check on the package name so that
    `foobar` does not match `foo`.

    File-type gating: JS-syntactic patterns only fire on .ts/.tsx/.js/.jsx/
    .mjs/.cjs/.mdx files, so an `import x from "pkg"` snippet inside a
    Python test fixture or a Markdown code block is not mistaken for a
    real npm usage. CSS patterns only fire on .css/.scss/.sass. HTML
    patterns only fire on .html/.htm.
    """
    if file in EXPECTED_NOISE_FILES:
        return None

    esc = re.escape(pkg)
    # Subpath gate: after the package name, the next char must be either
    # the closing quote, `/`, or end-of-string. Prevents foo matching foobar.
    sub = r"(?:/[^'\"`]*)?"

    flags_dotall = re.DOTALL | re.MULTILINE

    is_script = bool(SCRIPT_LIKE_EXT.search(file))
    is_style = bool(STYLE_EXT.search(file))
    is_html = bool(HTML_EXT.search(file))
    is_ts = bool(TS_LIKE_EXT.search(file))

    # If the file is none of script / style / html / json (which is the
    # quoted-string fallback surface) and is not an mdx file, no classify
    # rule applies. This is what gates out Python fixtures, Markdown code
    # blocks, shell snippets, etc.
    is_json = file.endswith(".json") or file.endswith(".jsonc")
    if not (is_script or is_style or is_html or is_json):
        return None

    # CSS @import is checked first so it does not collide with the
    # side-effect-import regex below.
    if is_style and re.search(rf"@import\s+['\"]{esc}{sub}['\"]", content):
        return "css_import"
    # Static imports: handle multi-line `import { ... } from "pkg"` by
    # allowing arbitrary content (newlines included) between `import`
    # and `from`. The non-greedy match plus the required `from` keeps
    # this scoped to a single statement.
    if is_script and re.search(
        rf"(?<!@)\bimport\b[^;'\"]*?\bfrom\s+['\"]{esc}{sub}['\"]",
        content,
        flags_dotall,
    ):
        return "static_import"
    # Side-effect import: `import "pkg"` (no `from`). The negative
    # lookbehind rules out CSS `@import` lines.
    if is_script and re.search(rf"(?<!@)\bimport\s+['\"]{esc}{sub}['\"]", content):
        return "side_effect_import"
    # Dynamic import: `import("pkg")` and `await import("pkg")`.
    if is_script and re.search(rf"\bimport\(\s*['\"]{esc}{sub}['\"]\s*\)", content):
        return "dynamic_import"
    # require / require.resolve
    if is_script and re.search(
        rf"\brequire(?:\.resolve)?\(\s*['\"]{esc}{sub}['\"]\s*\)", content
    ):
        return "require"
    # Re-exports: `export * from "pkg"`, `export { x } from "pkg"`,
    # `export type { Foo } from "pkg"`. Multi-line supported.
    if is_script and re.search(
        rf"\bexport\b[^;'\"]*?\bfrom\s+['\"]{esc}{sub}['\"]",
        content,
        flags_dotall,
    ):
        return "re_export"
    # HTML script / link. Match the package name as a complete path
    # segment bounded by a quote / `#` / `?` or a subpath `/`, so
    # `/node_modules/foo-extra/...` is NOT treated as usage of `foo`.
    html_pkg = rf"{esc}(?:/[^'\"#?]*)?(?=['\"#?])"
    if is_html and re.search(
        rf"<script[^>]*src\s*=\s*['\"][^'\"]*/{html_pkg}", content
    ):
        return "html_script"
    if is_html and re.search(rf"<link[^>]*href\s*=\s*['\"][^'\"]*/{html_pkg}", content):
        return "html_link"
    # TypeScript triple-slash
    if is_ts and re.search(
        rf"///\s*<reference\s+types\s*=\s*['\"]{esc}{sub}['\"]", content
    ):
        return "tsc_triple_slash"
    # new URL("pkg/...", import.meta.url)
    if is_script and re.search(rf"\bnew\s+URL\(\s*['\"]{esc}{sub}['\"]", content):
        return "new_url"
    # CSS url(...). Accept quoted ("pkg/x") AND unquoted (pkg/x) variants,
    # bounded by a path-segment lookahead so `pkg-extra` does not match.
    if is_style and re.search(
        rf"\burl\(\s*['\"]?(?:[^)'\"\s]+/)?{esc}(?:/[^)'\"`]*)?['\"]?\s*\)",
        content,
    ):
        return "css_url"
    # Template literal containing the package as the leading specifier
    if is_script and re.search(rf"`{esc}{sub}`", content):
        return "template_literal"
    # JSDoc / TS @import comment: `@import("pkg")`
    if is_script and re.search(rf"@import\(\s*['\"]{esc}{sub}['\"]\s*\)", content):
        return "jsdoc_import"
    # Bare quoted-string fallback (config plugin lists, vite aliases,
    # tsconfig paths, biome config plugin arrays, shadcn registries).
    if not JS_LIKE_EXT.search(file):
        return None
    # Boundary: pkg must be followed by `'`, `"`, or `/` to avoid
    # matching `foo` inside `foobar`.
    if re.search(rf"['\"]{esc}(?:['\"]|/)", content):
        return "string_literal"
    return None


def lockfile_root_sync(head_pkg: dict, head_lock: dict) -> list[str]:
    """Return a list of warnings if package-lock.json's <root> dep map
    disagrees with package.json (i.e., npm install was not re-run).
    """
    warnings = []
    if not head_lock:
        return warnings
    root = head_lock.get("packages", {}).get("", {})
    lock_decl = {
        **(root.get("dependencies") or {}),
        **(root.get("devDependencies") or {}),
        **(root.get("peerDependencies") or {}),
        **(root.get("optionalDependencies") or {}),
    }
    pkg_decl = {}
    for f in DEP_FIELDS:
        pkg_decl.update(head_pkg.get(f) or {})
    only_in_lock = set(lock_decl) - set(pkg_decl)
    only_in_pkg = set(pkg_decl) - set(lock_decl)
    if only_in_lock:
        warnings.append(
            f"lockfile <root> lists deps not in package.json (lockfile stale): {sorted(only_in_lock)}"
        )
    if only_in_pkg:
        warnings.append(
            f"package.json declares deps not in lockfile <root> (run npm install): {sorted(only_in_pkg)}"
        )
    return warnings


def types_orphan_warnings(head_pkg: dict) -> list[str]:
    """Flag @types/<X> deps where <X> is no longer declared anywhere
    in package.json. Removing X without also dropping @types/X leaves
    dangling type packages.
    """
    decl = set()
    for f in DEP_FIELDS:
        decl.update((head_pkg.get(f) or {}).keys())
    warnings = []
    for name in decl:
        if not name.startswith("@types/"):
            continue
        # @types/foo provides types for `foo`
        # @types/foo-bar provides types for `foo-bar`
        # @types/scope__pkg provides types for `@scope/pkg`
        target = name[len("@types/") :]
        if "__" in target:
            scope, sub = target.split("__", 1)
            target = f"@{scope}/{sub}"
        if target == "node":
            continue  # Node.js types are always implicit
        if target not in decl:
            warnings.append(
                f"@types/{target.replace('@', '').replace('/', '__')} present but '{target}' is not declared"
            )
    return warnings


_PKG_JSON_SKIP_KEYS = {
    "dependencies",
    "devDependencies",
    "peerDependencies",
    "optionalDependencies",
    "bundleDependencies",
    "bundledDependencies",
}

# Top-level fields whose contents are never package references. We walk
# everything else recursively.
_PKG_JSON_OPAQUE_KEYS = {
    "browserslist",  # browser queries
    "keywords",  # free-form strings
    "engines",  # node/npm version constraints
    "engineStrict",  # bool
    "packageManager",  # `pnpm@9.0.0` -- the package manager binary
    "volta",  # version pins for node/npm/yarn
    "files",  # paths included in publish
    "directories",  # paths
    "publishConfig",  # registry / access config
    "config",  # generic npm config values
    "main",
    "module",
    "browser",
    "types",
    "typings",
    "type",
    "exports",
    "imports",
    "bin",
    "man",  # author-side fields (not consumer refs)
    "scripts",  # handled separately via scripts_bin_refs()
    "repository",
    "bugs",
    "homepage",
    "funding",
    "author",
    "contributors",
    "maintainers",
    "license",
    "licenses",
    "name",
    "version",
    "description",
    "private",
    "sideEffects",
    "workspaces",  # paths/globs, NOT pkg names
}


def package_json_extra_refs(pkg: dict, target: str) -> list[str]:
    """Walk every key/value in package.json EXCEPT the dep declaration
    blocks, and return citations for string values or dict keys that
    equal `target` (or `target/subpath`).

    Catches the patterns the public dep-checker tools commonly miss:
      - `overrides` / `resolutions` / `pnpm.overrides` keys
      - `pnpm.patchedDependencies` keys
      - `peerDependenciesMeta` keys
      - `prettier`: "@my/prettier-config"
      - `eslintConfig.extends`: ["..."] / "..."
      - `stylelint.extends` / `stylelint.plugins`
      - `babel.presets` / `babel.plugins`
      - `jest.preset` / `jest.setupFiles` / `jest.transform`
      - `commitlint.extends`, `renovate.extends`, `remarkConfig.plugins`
    """
    target_sub = target + "/"
    cites: list[str] = []

    def matches(s: object) -> bool:
        return isinstance(s, str) and (s == target or s.startswith(target_sub))

    def walk(obj: object, path: str) -> None:
        if isinstance(obj, dict):
            for k, v in obj.items():
                # Skip top-level dep declaration fields entirely.
                if path == "" and k in _PKG_JSON_SKIP_KEYS:
                    continue
                # Top-level fields whose contents are never package refs.
                if path == "" and k in _PKG_JSON_OPAQUE_KEYS:
                    continue
                # Inside `overrides` / `resolutions` / etc., the KEY itself
                # is a package reference.
                if matches(k):
                    cites.append(f"{path}.{k}" if path else k)
                walk(v, f"{path}.{k}" if path else k)
        elif isinstance(obj, list):
            for i, v in enumerate(obj):
                walk(v, f"{path}[{i}]")
        elif isinstance(obj, str):
            if matches(obj):
                cites.append(f"{path}: {obj}")

    walk(pkg, "")
    return cites


def build_bin_to_pkg(head_lock: dict) -> dict[str, str]:
    """Map a binary name (e.g. 'vite', 'tsc', 'eslint') to the package
    that provides it. Built from each lockfile entry's `bin` field.
    """
    out: dict[str, str] = {}
    if not head_lock:
        return out
    for path, meta in head_lock.get("packages", {}).items():
        if not path:
            continue
        name = path.split("node_modules/")[-1]
        bins = meta.get("bin")
        if isinstance(bins, dict):
            for binname in bins:
                out.setdefault(binname, name)
        elif isinstance(bins, str):
            out.setdefault(name.split("/")[-1], name)
    return out


_SCRIPT_TOKENIZE = re.compile(r"\s*(?:&&|\|\||;|\|(?!\|))\s*")

# Wrappers that delegate to a real CLI in the same shell word list.
# After stripping env prefixes and (optionally) `npx`/`pnpm exec`/`yarn dlx`/
# `bunx`, if the leading token is one of these we advance past the
# wrapper's own flags and any further env-prefix tokens, then re-check.
# `cross-env` is the common one; `dotenv-cli` / `dotenvx` use `--` as a
# separator. Wrappers that operate on named npm-scripts (concurrently,
# npm-run-all, run-s, run-p, wireit, turbo, nx) intentionally aren't
# here -- they reference script names, not bin names, so the real bin
# is in the *target* script's chunk which we already tokenize.
_SCRIPT_WRAPPERS = {"cross-env", "dotenv", "dotenvx", "env-cmd"}
_ENV_PREFIX_RE = re.compile(r"^[A-Za-z_][A-Za-z0-9_]*=")


def _next_real_bin(words: list[str], idx: int) -> str | None:
    """Walk `words` from `idx`, peeling env-prefix tokens, the leading
    package-manager runner (`npx`, `pnpm exec`, etc.), and the known
    wrapper bins. Return the next token that looks like the real CLI
    binary, or None if the chunk has nothing to look up.

    Recursion depth is bounded by the chunk's word count, so the loop
    cannot run away on a pathological wrapper chain.
    """
    seen_wrappers: set[str] = set()
    while idx < len(words):
        # 1. env-prefix run: `FOO=bar BAZ="a b" cmd ...`. shlex has
        # already collapsed quoted values into one word, so this
        # tokenizer is safe for them.
        while idx < len(words) and _ENV_PREFIX_RE.match(words[idx]):
            idx += 1
        if idx >= len(words):
            return None

        first = words[idx]
        # 2. Package-manager runner: `npx <pkg> args`, `pnpm exec <pkg>`,
        # `yarn dlx <pkg>`, `bunx <pkg>`. Strip and continue (so the
        # wrapped command goes through the same unwrap loop).
        if first in {"npx", "pnpx", "bunx"} and idx + 1 < len(words):
            idx += 1
            continue
        if (
            first in {"pnpm", "yarn"}
            and idx + 2 < len(words)
            and words[idx + 1] in {"exec", "dlx"}
        ):
            idx += 2
            continue

        # 3. Wrapper bin (cross-env, dotenv, etc.). Skip the wrapper's
        # own flags and any subsequent env-prefix tokens, then re-loop.
        bin_token = first.removeprefix("./node_modules/.bin/").removeprefix(
            "node_modules/.bin/"
        )
        if bin_token in _SCRIPT_WRAPPERS and bin_token not in seen_wrappers:
            seen_wrappers.add(bin_token)
            idx += 1
            # cross-env / env-cmd: no flags; just more env-prefix tokens.
            # dotenv / dotenvx: skip `-e <file>` style flags and the
            # optional `--` separator before the wrapped command.
            while idx < len(words):
                tok = words[idx]
                if tok.startswith("-") and tok != "--":
                    idx += 1
                    # `-e .env` style: also skip the flag's argument
                    # when it does not look like another flag.
                    if (
                        idx < len(words)
                        and not words[idx].startswith("-")
                        and not _ENV_PREFIX_RE.match(words[idx])
                    ):
                        idx += 1
                    continue
                if tok == "--":
                    idx += 1
                    break
                break
            continue
        return bin_token
    return None


def scripts_bin_refs(
    head_pkg: dict, bin_to_pkg: dict[str, str]
) -> dict[str, list[str]]:
    """Return `{package_name: ['scripts.X: cmd', ...]}` listing every
    package referenced via its bin name in package.json scripts.

    Each script value is split on shell separators (`&&`, `||`, `;`,
    `|`). Within each chunk, `_next_real_bin()` unwraps env prefixes,
    package-manager runners (`npx` / `pnpm exec` / `yarn dlx` / `bunx`),
    and wrapper bins like `cross-env` / `dotenv` so that
    `cross-env CI=1 biome check` correctly credits `biome` to its
    declaring package.

    Tokenization uses shlex.split so quoted env values
    (`FOO="a b" biome`) survive unbroken.
    """
    import shlex

    scripts = head_pkg.get("scripts", {}) or {}
    refs: dict[str, list[str]] = {}
    for script_name, raw_cmd in scripts.items():
        if not isinstance(raw_cmd, str):
            continue
        for chunk in _SCRIPT_TOKENIZE.split(raw_cmd):
            chunk = chunk.strip()
            if not chunk:
                continue
            try:
                words = shlex.split(chunk, posix = True)
            except ValueError:
                # Unbalanced quotes -- fall back to plain split.
                words = chunk.split()
            if not words:
                continue
            bin_name = _next_real_bin(words, 0)
            if bin_name is None:
                continue
            pkg = bin_to_pkg.get(bin_name)
            if pkg:
                refs.setdefault(pkg, []).append(f"scripts.{script_name}: {raw_cmd}")
    return refs


def tsconfig_compiler_types_refs() -> set[str]:
    """Read studio/frontend/tsconfig*.json and return the set of
    package names referenced in compilerOptions.types arrays. These are
    implicitly loaded by tsc and count as a real use even though they
    have no explicit import.
    """
    out: set[str] = set()
    base = REPO_ROOT / "studio/frontend"
    for name in ("tsconfig.json", "tsconfig.app.json", "tsconfig.node.json"):
        path = base / name
        if not path.exists():
            continue
        try:
            text = path.read_text()
            # tsconfig allows comments; strip simple line comments.
            text = re.sub(r"//[^\n]*", "", text)
            data = json.loads(text)
        except (OSError, json.JSONDecodeError):
            continue
        types = (data.get("compilerOptions", {}) or {}).get("types", []) or []
        for t in types:
            if not isinstance(t, str):
                continue
            # `vite/client` resolves to `vite` package.
            pkg = (
                t.split("/", 1)[0]
                if not t.startswith("@")
                else "/".join(t.split("/", 2)[:2])
            )
            out.add(pkg)
    return out


def enumerate_dep_usage(head_pkg: dict, head_lock: dict) -> dict[str, list]:
    """For every declared dep, classify whether it appears used. Returns
    a dict with these categories:
      - used:                 has at least one detected usage in src/,
                              config files, scripts.bin, package.json
                              field refs, or tsconfig types
      - unused:               no detected usage anywhere
      - type_pkg_kept:        @types/X where X is still declared
      - type_pkg_orphan:      @types/X where X is no longer declared
                              (or X is removed) -- candidate for removal

    Each entry is the package name. The categorisation is opinionated;
    `unused` is a CANDIDATE list, not a guarantee. The caller should
    verify before deletion.
    """
    decl = all_decl_names(head_pkg)
    bin_to_pkg = build_bin_to_pkg(head_lock) if head_lock else {}
    script_refs = scripts_bin_refs(head_pkg, bin_to_pkg)
    tsc_types = tsconfig_compiler_types_refs()

    results: dict[str, list] = {
        "used": [],
        "unused": [],
        "type_pkg_kept": [],
        "type_pkg_orphan": [],
    }
    for name in sorted(decl):
        if name.startswith("@types/"):
            target = name[len("@types/") :]
            if "__" in target:
                scope, sub = target.split("__", 1)
                target = f"@{scope}/{sub}"
            if target == "node":
                results["type_pkg_kept"].append(name)
            elif target in decl:
                results["type_pkg_kept"].append(name)
            else:
                results["type_pkg_orphan"].append(name)
            continue
        # Real-source-usage check
        hits = find_usage(name)
        used = bool(hits)
        # CLI usage in shell / workflow / Dockerfile surfaces. Skip for
        # `@types/*` packages because they never expose a CLI binary and
        # the unscoped-tail bin name candidate would scan workflow files
        # for the bare runtime name (a removed `@types/foo` would look
        # for invocations of `foo`).
        if not used and not name.startswith("@types/") and find_command_usage(name):
            used = True
        # Bin scripts
        if not used and name in script_refs:
            used = True
        # package.json non-dep field references
        if not used and package_json_extra_refs(head_pkg, name):
            used = True
        # tsconfig compilerOptions.types implicit usage
        if not used and name in tsc_types:
            used = True
        if used:
            results["used"].append(name)
        else:
            results["unused"].append(name)
    return results


def find_imports_without_decl(head_pkg: dict) -> list[tuple[str, int, str]]:
    """Reverse check: find bare-specifier imports in studio/frontend/src
    that don't correspond to any declared package.json dep. Catches the
    case where someone adds an import but forgets the dep declaration.
    Returns (file, line, spec) tuples.

    Match shapes covered:
      import "pkg"
      import Foo from "pkg"
      import { Foo } from "pkg"
      import type { Foo } from "pkg"
      const x = require("pkg")
      const x = await import("pkg")
    """
    decl = set()
    for f in DEP_FIELDS:
        decl.update((head_pkg.get(f) or {}).keys())
    # Also: anything tsconfig path-aliases (just '@/...' here) is internal.
    # The capture group is the specifier; the leading alternation accepts
    # any of: `from "..."`, bare side-effect `import "..."`,
    # `import("..."), or `require("...")`. We exclude relative paths and
    # the `@/` alias prefix by requiring the first char of the specifier
    # to be neither `.` nor `/`.
    pattern = (
        r"(?:\bfrom\s+|"
        r"\bimport\s+(?:\(\s*)?|"
        r"\brequire(?:\.resolve)?\(\s*)"
        r"['\"]([^'\"./][^'\"]*)['\"]"
    )
    args = [
        "grep",
        "-rnE",
        pattern,
        "--include=*.ts",
        "--include=*.tsx",
        "--include=*.js",
        "--include=*.jsx",
        "studio/frontend/src",
    ]
    out = run(args)
    missing = []
    for line in out.splitlines():
        m = re.match(r"^(?:\./)?([^:]+):(\d+):(.*)$", line)
        if not m:
            continue
        file, ln, content = m.group(1), int(m.group(2)), m.group(3)
        for spec_match in re.finditer(pattern, content):
            spec = spec_match.group(1)
            # Resolve to package name (strip subpath)
            if spec.startswith("@"):
                parts = spec.split("/", 2)
                pkg_name = "/".join(parts[:2]) if len(parts) >= 2 else spec
            else:
                pkg_name = spec.split("/", 1)[0]
            if pkg_name in decl:
                continue
            # Internal aliases like '@/foo' or starts with builtin names
            if pkg_name == "@":
                continue
            if pkg_name in {
                "node:fs",
                "node:path",
                "fs",
                "path",
                "url",
                "stream",
                "crypto",
                "buffer",
                "util",
                "events",
                "child_process",
            }:
                continue
            missing.append((file, ln, spec))
    return missing


def grep_repo(pat: str) -> list[tuple[str, int, str]]:
    args = ["grep", "-rnE", pat] + GREP_INCLUDES + GREP_EXCLUDES + ["."]
    out = run(args)
    rows = []
    for line in out.splitlines():
        m = re.match(r"^(\./)?([^:]+):(\d+):(.*)$", line)
        if m:
            rows.append((m.group(2), int(m.group(3)), m.group(4)))
    return rows


_file_lines_cache: dict[str, list[str]] = {}


def _read_file(path: str) -> list[str]:
    if path not in _file_lines_cache:
        try:
            _file_lines_cache[path] = (
                Path(path).read_text(errors = "replace").splitlines()
            )
        except (OSError, UnicodeDecodeError):
            _file_lines_cache[path] = []
    return _file_lines_cache[path]


def find_usage(pkg: str) -> list[Hit]:
    """Return real usages of `pkg`. Filters pip-playwright separately.

    For each filename returned by grep, also feed a multi-line window
    around the matching line into classify() so multi-line imports
    (`import {\n a\n} from "pkg"`) get picked up.
    """
    rows = grep_repo(re.escape(pkg))
    hits = []
    seen_keys: set[tuple[str, str]] = set()
    for file, lineno, content in rows:
        if pkg == "playwright" and PIP_PLAYWRIGHT.search(content):
            continue
        # Try the single-line classify first.
        kind = classify(pkg, file, content)
        if not kind:
            # Multi-line window: a generous 25 lines above + the line +
            # 25 below so Prettier's one-import-per-line formatting for
            # 12-20+ named imports still includes the `import` keyword
            # in the same window as the `from "pkg"` clause.
            lines = _read_file(file)
            lo = max(0, lineno - 26)
            hi = min(len(lines), lineno + 25)
            window = "\n".join(lines[lo:hi])
            kind = classify(pkg, file, window)
        if kind:
            key = (file, kind)
            if key in seen_keys:
                continue
            seen_keys.add(key)
            hits.append(Hit(file, lineno, kind, content[:160]))
    return hits


def _candidate_bin_names(pkg: str) -> set[str]:
    """Names a removed package's CLI could be invoked under in shell
    scripts and workflow files. Most npm CLIs use the package name
    (`vite`, `eslint`, `playwright`); scoped CLI packages commonly
    expose an unscoped binary name (`@biomejs/biome` -> `biome`).
    """
    return {pkg, pkg.rsplit("/", 1)[-1]}


def find_command_usage(pkg: str) -> list[Hit]:
    """Find package CLI invocations in shell / workflow / Dockerfile
    surfaces: `npx pkg`, `bunx pkg`, `pnpm exec pkg`, `yarn dlx pkg`,
    or a bare `pkg --flag`. Returns Hit("command_bin").

    Detection is bounded to COMMAND_LIKE_EXT files so a JS string that
    happens to contain `npx foo` inside a TS test fixture is not
    mistaken for a real invocation.
    """
    bins = sorted(_candidate_bin_names(pkg), key = len, reverse = True)
    esc_bins = "|".join(re.escape(b) for b in bins)
    # grep ERE pattern (POSIX classes for whitespace/word boundaries).
    # Build without f-strings to avoid f-string-vs-{} confusion with the
    # POSIX `[[:space:]]` literals and trailing `})}` boundary class.
    grep_pat = (
        r"(^|[[:space:]:;&|(\[])"
        r"(npx[[:space:]]+|pnpm[[:space:]]+exec[[:space:]]+"
        r"|yarn[[:space:]]+(dlx[[:space:]]+)?|bunx[[:space:]]+)?"
        r"(" + esc_bins + r")"
        r"([[:space:])};|\]]|$)"
    )
    py_pat = re.compile(
        r"(^|[\s:;&|(\[])"
        r"(?:npx\s+|pnpm\s+exec\s+|yarn\s+(?:dlx\s+)?|bunx\s+)?"
        r"(" + esc_bins + r")"
        r"([\s)};|\]]|$)"
    )
    hits: list[Hit] = []
    seen: set[tuple[str, int]] = set()
    for file, lineno, content in grep_repo(grep_pat):
        if not COMMAND_LIKE_EXT.search(file):
            continue
        if pkg == "playwright" and PIP_PLAYWRIGHT.search(content):
            continue
        if not py_pat.search(content):
            continue
        key = (file, lineno)
        if key in seen:
            continue
        seen.add(key)
        hits.append(Hit(file, lineno, "command_bin", content[:160]))
    return hits


def types_target_name(pkg: str) -> str | None:
    """Strip `@types/` prefix and decode the npm scope-encoding so the
    return value matches the runtime package name. `@types/foo` -> `foo`,
    `@types/foo__bar` -> `@foo/bar`. Returns None for non-@types packages.
    """
    if not pkg.startswith("@types/"):
        return None
    target = pkg[len("@types/") :]
    if "__" in target:
        scope, sub = target.split("__", 1)
        return f"@{scope}/{sub}"
    return target


def find_types_runtime_usage(pkg: str, tsc_types: set[str]) -> list[Hit]:
    """For a removed `@types/X`, find usages of `X` itself: explicit
    `/// <reference types="X" />`, `tsconfig.compilerOptions.types: ["X"]`,
    and runtime `import "X"` shapes. The whole point of `@types/X` is to
    type one of those; if any are present, the type package must stay.
    """
    target = types_target_name(pkg)
    if target is None:
        return []
    hits = find_usage(target)
    if target in tsc_types:
        hits.append(
            Hit(
                "studio/frontend/tsconfig*.json",
                0,
                "tsconfig_types",
                f'compilerOptions.types includes "{target}"',
            )
        )
    return hits


def main() -> int:
    p = argparse.ArgumentParser(
        description = __doc__, formatter_class = argparse.RawTextHelpFormatter
    )
    p.add_argument(
        "--base",
        default = "origin/main",
        help = "git ref to diff against (default: origin/main). "
        "Examples: HEAD~1, main, a-tag, a-sha.",
    )
    p.add_argument(
        "--base-pkg", help = "optional override: read base package.json from this path"
    )
    p.add_argument(
        "--base-lock",
        help = "optional override: read base package-lock.json from this path. "
        "Used to recover the bin -> package mapping for removed packages so "
        "scripts.foo still flags as a usage even after the PR drops node_modules/foo.",
    )
    p.add_argument(
        "--head-pkg",
        default = str(REPO_ROOT / FRONTEND_PKG),
        help = "head package.json path (default: working tree)",
    )
    p.add_argument(
        "--head-lock",
        default = str(REPO_ROOT / FRONTEND_LOCK),
        help = "head lockfile path (default: working tree). "
        "Reachability analysis runs against this lockfile.",
    )
    p.add_argument("--verbose", action = "store_true")
    p.add_argument(
        "--strict",
        action = "store_true",
        help = "Also fail on hygiene warnings (lockfile sync, "
        "@types orphans, imports without declared dep, unused deps).",
    )
    p.add_argument(
        "--enumerate-dead",
        action = "store_true",
        help = "Print every declared dep that appears unused anywhere "
        "in the repo. Informational; does not fail unless --strict.",
    )
    args = p.parse_args()

    if args.base_pkg:
        base_pkg = read_pkg_file(Path(args.base_pkg))
    else:
        base_pkg = read_pkg_at(args.base, FRONTEND_PKG)
    head_pkg = read_pkg_file(Path(args.head_pkg))
    if not base_pkg:
        print(
            f"ERROR: could not read base package.json at {args.base}:{FRONTEND_PKG}",
            file = sys.stderr,
        )
        return 2
    if not head_pkg:
        print(
            f"ERROR: could not read head package.json at {args.head_pkg}",
            file = sys.stderr,
        )
        return 2

    head_lock_path = Path(args.head_lock)
    if not head_lock_path.exists():
        print(
            f"ERROR: head lockfile not found at {head_lock_path}",
            file = sys.stderr,
        )
        return 2
    head_lock = read_pkg_file(head_lock_path)

    # Base lockfile is best-effort. We use it only to recover the
    # bin -> package mapping for packages the PR is removing -- so a
    # `scripts.biome:check` cite still fires when `@biomejs/biome` is
    # being dropped and the head lockfile no longer has it.
    if args.base_lock:
        base_lock_path = Path(args.base_lock)
        base_lock = read_pkg_file(base_lock_path) if base_lock_path.exists() else {}
    else:
        base_lock = read_pkg_at(args.base, FRONTEND_LOCK)

    base_names = all_decl_names(base_pkg)
    head_names = all_decl_names(head_pkg)
    removed = sorted(base_names - head_names)

    # All hygiene checks compute up front so they can run on both the
    # removal-present and removal-empty paths (so `--strict` actually
    # fails when only hygiene issues exist).
    sync_warns = lockfile_root_sync(head_pkg, head_lock)
    types_warns = types_orphan_warnings(head_pkg)
    missing_imports = find_imports_without_decl(head_pkg)
    enum = enumerate_dep_usage(head_pkg, head_lock) if args.enumerate_dead else None

    def _print_hygiene() -> None:
        if sync_warns:
            print("Lockfile sync warnings:")
            for w in sync_warns:
                print(f"  - {w}")
            print()
        if types_warns:
            print("@types orphan warnings:")
            for w in types_warns:
                print(f"  - {w}")
            print()
        if missing_imports:
            print(
                f"Imports without a matching package.json dep ({len(missing_imports)}):"
            )
            for file, ln, spec in missing_imports[:20]:
                print(f"  - {file}:{ln}  imports '{spec}'")
            print()
        if enum is not None:
            print("Dead-dep enumeration:")
            if enum["unused"]:
                print(f"  unused ({len(enum['unused'])}):")
                for n in enum["unused"]:
                    print(f"    - {n}")
            else:
                print("  unused: none")
            if enum["type_pkg_orphan"]:
                print(f"  type_pkg_orphan ({len(enum['type_pkg_orphan'])}):")
                for n in enum["type_pkg_orphan"]:
                    print(f"    - {n}")
            if args.verbose:
                print(f"  used: {len(enum['used'])}")
                print(f"  type_pkg_kept: {len(enum['type_pkg_kept'])}")
            print()

    hygiene_strict_fail = args.strict and (
        sync_warns
        or types_warns
        or missing_imports
        or (enum is not None and (enum["unused"] or enum["type_pkg_orphan"]))
    )

    if not removed:
        print("[OK] no dependencies removed from studio/frontend/package.json")
        if args.enumerate_dead or sync_warns or types_warns or missing_imports:
            print()
            _print_hygiene()
        if hygiene_strict_fail:
            print("FAIL (--strict): one or more hygiene warnings present")
            return 1
        return 0

    print(
        f"Checking {len(removed)} removed package(s) from studio/frontend/package.json"
    )
    print(f"Base: {args.base}    Head: working tree")
    print()

    reachable_paths = reachable_from_head(head_pkg, head_lock) if head_lock else set()
    # bin -> package map: start from the head lockfile, then layer the
    # base lockfile's entries on top for packages this PR is removing.
    # A correct removal updates the head lockfile to drop node_modules/foo,
    # so build_bin_to_pkg(head_lock) loses the mapping; we recover it
    # from the base lockfile so `scripts.biome:check` still flags as a
    # usage when `@biomejs/biome` is being dropped.
    bin_to_pkg = build_bin_to_pkg(head_lock) if head_lock else {}
    base_bin_to_pkg = build_bin_to_pkg(base_lock) if base_lock else {}
    removed_set = set(removed)
    for bin_name, pkg_name in base_bin_to_pkg.items():
        if pkg_name in removed_set:
            bin_to_pkg.setdefault(bin_name, pkg_name)
    script_refs = scripts_bin_refs(head_pkg, bin_to_pkg)
    tsc_types = tsconfig_compiler_types_refs()

    def reachable_install_paths(name: str) -> tuple[str | None, list[str]]:
        """Return (top_level_path, nested_paths). top_level is what bare
        `import "name"` from src/ actually resolves to; nested copies are
        only visible inside the parent package that nested them.
        """
        top = f"node_modules/{name}"
        top_path = top if top in reachable_paths else None
        nested = sorted(
            p
            for p in reachable_paths
            if p != top and p.endswith(f"/node_modules/{name}")
        )
        return top_path, nested

    failures: list[tuple[str, list[Hit]]] = []
    for name in removed:
        hits = find_usage(name)
        # CLI invocations in shell scripts / workflows / Dockerfiles.
        hits.extend(find_command_usage(name))
        # @types/X is "used" if X is referenced as a type or as a
        # runtime import elsewhere in the repo.
        hits.extend(find_types_runtime_usage(name, tsc_types))
        for cite in script_refs.get(name, []):
            hits.append(Hit("studio/frontend/package.json", 0, "script_bin", cite))
        for cite in package_json_extra_refs(head_pkg, name):
            hits.append(Hit("studio/frontend/package.json", 0, "pkg_json_field", cite))
        top, nested = reachable_install_paths(name)
        importable_top_level = top is not None
        # Source imports of bare specifier `name` resolve ONLY to top-level
        # node_modules/<name>. Nested copies under another package are
        # invisible to src/ files.
        if hits and not importable_top_level:
            status = "FAIL"
        elif hits and importable_top_level:
            status = "OK-via-transitive"
        else:
            status = "OK"
        print(f"  [{status}] {name}")
        if top:
            print(f"    reachable (top-level): {top}")
        if nested:
            print(
                f"    reachable (nested, NOT importable from src/): {nested[0]}"
                + (f" (+{len(nested)-1} more)" if len(nested) > 1 else "")
            )
        if hits:
            for h in hits[:5]:
                print(f"    [{h.kind}] {h.file}:{h.line}  {h.snippet}")
        if status == "FAIL":
            failures.append((name, hits))
        if args.verbose and not hits and not (top or nested):
            print("    no references, not reachable -- clean removal")

    print()

    _print_hygiene()

    if failures:
        print(
            f"FAIL: {len(failures)} removed package(s) still referenced and not resolvable"
        )
        for name, _ in failures:
            print(f"  - {name}")
        return 1
    if hygiene_strict_fail:
        print("FAIL (--strict): one or more hygiene warnings present")
        return 1

    print("PASS: all removed packages are safe to drop")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())