---
name: helpers-and-infra-keeper
description: >-
  Work with DiscordPHP's infrastructure utilities — CacheWrapper, CacheConfig,
  BigInt, Multipart, Endpoint::bind URL templates, Collection base class, and
  domain Exceptions. Use when changing cache behavior, REST endpoint routing,
  file uploads, big-integer ID math, or adding/modifying exceptions.
---

# Skill: helpers-and-infra-keeper

Use this skill when work touches `src/Discord/Helpers/*`, `src/Discord/Exceptions/*`, `Endpoint::bind()` patterns, or the external `Collection` / `discord-php/http` packages.

These are cross-cutting infrastructure utilities. They have no domain logic, but nearly every other layer depends on them.

## Read in this order

1. `src/Discord/Helpers/CacheWrapper.php` — PSR-16 + React cache bridge
2. `src/Discord/Helpers/CacheConfig.php` — cache options (compression, sweep, TTL)
3. `src/Discord/Helpers/LegacyCacheWrapper.php` — fallback for older cache implementations
4. `src/Discord/Helpers/BigInt.php` — 32-bit PHP GMP polyfill for snowflake IDs and permission bitfields
5. `src/Discord/Helpers/Multipart.php` — multipart/form-data builder for file uploads
6. `src/Discord/Repository/AbstractRepository.php` — how repositories consume `CacheWrapper` and `$endpoints`
7. `src/Discord/Discord.php` — `options['cache']` wiring to `CacheWrapper`/`CacheConfig`

## Cache infrastructure

### Three-class hierarchy

| Class | Role |
| --- | --- |
| `CacheConfig` | Value object holding cache options passed in `Discord::__construct()` `options['cache']` |
| `CacheWrapper` | Main wrapper: bridges React's async cache (PSR-16 + react/cache) to repository storage. Handles compression if configured. |
| `LegacyCacheWrapper` | Default when no external cache is configured. Wraps an in-memory store. Used by default. |

**Rule:** repositories do not interact with cache stores directly. They always go through `CacheWrapper`. Do not bypass it.

### When to use CacheConfig

If a feature needs configurable cache behavior (TTL, compression, sweep interval), add it as a property on `CacheConfig`. Do not scatter cache tuning across individual repositories.

### Cache coherence rule

When a REST write succeeds, the cache write must happen in the same promise chain — not after a refetch. This is enforced by convention, not framework. Break the chain and you get stale cache.

## Endpoint::bind() — URL template pattern

All REST endpoints are defined as `Endpoint` constants in the external `discord-php/http` package:

```php
use Discord\Http\Endpoint;

protected $endpoints = [
    'get'    => Endpoint::CHANNEL,
    'update' => Endpoint::CHANNEL,
    'delete' => Endpoint::CHANNEL,
];
```

Routes with parameters use `:param` placeholders. Binding happens via `Endpoint::bind($endpoint, $params)` where `$params` is a key-value map matching the placeholders.

**Rule:** never build URL strings by hand. Always use `Endpoint::bind()` or assign a named `Endpoint` constant. Raw string concatenation bypasses rate-limit bucket identification.

### Finding endpoint constants

Browse `vendor/discord-php/http/src/Endpoint.php` for available constants. If a Discord API endpoint is missing, add it to the external package — do not define it inline in DiscordPHP source.

### Checking against Discord's OpenAPI description

`composer openapi` (`scripts/openapi-check.php`) compares the library with the live preview of Discord's OpenAPI description. It lists the operations DiscordPHP never sends a request for, and routes with no `Endpoint` constant. It also lists what Discord has changed since the commit recorded in `scripts/openapi-baseline.json`: endpoints added or removed, parameters and responses, schema properties and enum values. It reads the library's source to see which request each constant is sent with. It recognises a repository's `$endpoints` table (`all`/`get` send GET, `create` POST, `update` PATCH, `delete` DELETE, and other keys whatever method sends `$this->endpoints['key']`), a direct call like `->post(Endpoint::bind(Endpoint::X, …))`, or a variable assigned the endpoint and sent later in the same method. Keep new request code in one of those shapes, or the check will report the operation as unsent.

After implementing an operation, or deciding not to, run `composer openapi:update` and commit the baseline. Record the reason for every gap that remains in its `unimplemented` map. A daily workflow (`.github/workflows/openapi.yml`) runs the same check and opens an issue labelled `openapi` when it finds something new.

The check also reads Discord's stable description (`specs/openapi.json`) at the same commit. Operations, parameters, properties and enum values that only the preview has are marked `[preview only]`; the issue then carries a caution and the `openapi-preview` label. Discord may change or remove them at any time. Anything implemented from them gets `@since X.Y.Z OpenAPI Preview` in its docblock and a sentence saying it is only in Discord's OpenAPI preview and may change or be removed at any time, so users do not rely on it. `composer openapi -- --all` lists everything only in the preview. When the check reports something as now in the stable edition too, remove its preview flag.

## Collection base class

All repositories extend `Collection` from `discord-php-helpers/collection`. Key behaviors inherited:

- discriminator-keyed storage (`$discrim` — defaults to `'id'`)
- typed item enforcement (`$class`)
- `get($key)`, `has($key)`, `first()`, `find(callable)`, `filter(callable)`
- JSON serialization

`AbstractRepository` adds REST/cache behavior on top. Do not re-implement collection operations in repositories — use the inherited helpers.

## BigInt

`BigInt` provides GMP-based arithmetic for environments where PHP is compiled as 32-bit, where Discord snowflake IDs and 64-bit permission bitfields overflow native integers.

Usage pattern:
```php
use Discord\Helpers\BigInt;

$perms = BigInt::bitAnd($memberPerms, $requiredPerm);
```

**Rule:** use `BigInt` for any permission flag arithmetic or snowflake comparison that could run on 32-bit PHP. Do not assume `PHP_INT_SIZE === 8`.

## Multipart

`Multipart` builds `multipart/form-data` request bodies for file attachment uploads. It is used by `MessageBuilder` and similar builders when attachments are present.

It has no cache or domain logic — treat it as a serialization helper.

## Exception hierarchy

`src/Discord/Exceptions/` contains domain-specific exceptions. Do not use generic `\RuntimeException` or `\InvalidArgumentException` when a typed exception already exists:

| Exception | When to throw |
| --- | --- |
| `IntentException` | Invalid or missing gateway intents at startup |
| `PartRequestFailedException` | A part fetch or REST operation failed |
| `InvalidOverwriteException` | A permission overwrite is malformed |
| `AttachmentSizeException` | Attachment exceeds size limit |
| `FileNotFoundException` | File path not found for upload |
| `BufferTimedOutException` | Audio buffer read timed out |
| `LibSodiumNotFoundException` | `ext-sodium` not available (voice) |
| `OpusNotFoundException` | Opus codec binary not available |
| `FFmpegNotFoundException` | FFmpeg binary not found |
| `DCANotFoundException` | DCA tool not found |

When adding a new typed exception: extend `\Exception` or the nearest domain parent, keep the name `*Exception`, and put it in `src/Discord/Exceptions/`.

## Companion surfaces

| Touching | Also inspect |
| --- | --- |
| `CacheWrapper` or `CacheConfig` | `Discord.php` `options['cache']` wiring, `AbstractRepository` cache usage, `LegacyCacheWrapper` fallback |
| `Endpoint` constants | `$endpoints` arrays in all affected repositories, rate-limit bucket behavior |
| `BigInt` | Permission parts (`Permission`, `RolePermission`, `ChannelPermission`), snowflake comparison sites |
| `Multipart` | `MessageBuilder` attachment handling, HTTP client request formation |
| An exception class | Callers that catch the specific type, docs/guide if it's user-facing |

## Design tripwires

- Building REST URL strings by hand instead of using `Endpoint::bind()`
- Writing to a cache store directly inside a repository, bypassing `CacheWrapper`
- Re-implementing collection iteration helpers that `Collection` already provides
- Using `PHP_INT_SIZE === 8` as a safe assumption for permission arithmetic — use `BigInt`
- Throwing `\RuntimeException` when a typed domain exception already exists
- Adding domain logic (Discord resource rules) to any class in `Helpers/` or `Exceptions/`
- Putting new audio stream or voice crypto helpers in `Helpers/` — those belong in `Voice/*` or the external voice package

## Reference files

- `src/Discord/Helpers/CacheWrapper.php` — main cache bridge
- `src/Discord/Helpers/CacheConfig.php` — cache options value object
- `src/Discord/Helpers/LegacyCacheWrapper.php` — default in-memory cache
- `src/Discord/Helpers/BigInt.php` — 32-bit PHP GMP polyfill
- `src/Discord/Helpers/Multipart.php` — file upload form builder
- `src/Discord/Repository/AbstractRepository.php` — how CacheWrapper and Endpoint are consumed
- `src/Discord/Exceptions/IntentException.php` — representative typed exception
- `src/Discord/Exceptions/PartRequestFailedException.php` — REST failure exception
- `vendor/discord-php/http/src/Endpoint.php` — all REST endpoint constants