Skill: builder-payload-smith

Use this skill when work touches:

• src/Discord/Builders/*
• src/Discord/Builders/Components/*
• outbound payload construction paths in parts or interaction responses

This is outbound-shape skill. Load it when a change affects how callers build data to send to Discord.

Goal

Keep builders as the repo's safe way to author complex outbound payloads:

• fluent and ergonomic for callers
• validated before hitting REST
• cleanly separated from in-memory parts
• serializable into Discord API payloads

Read in this order

1. src/Discord/Builders/Builder.php
2. src/Discord/Helpers/DynamicPropertyMutatorTrait.php
3. src/Discord/Builders/ComponentsTrait.php
4. Representative builders:
   • src/Discord/Builders/MessageBuilder.php
   • src/Discord/Builders/ChannelBuilder.php
   • src/Discord/Builders/CommandBuilder.php
   • src/Discord/Builders/ModalBuilder.php
5. Component base types:
   • src/Discord/Builders/Components/Component.php
   • src/Discord/Builders/Components/ComponentObject.php
6. Matching part or repository family that consumes builder output

Core contract

Builders are not parts. Builders:

• extend Builder
• often implement JsonSerializable
• keep mutable fluent state for outbound payloads
• validate limits and allowed values in setters or adders
• serialize to request-ready arrays
• sometimes provide create($repository) helpers for smoother public API

If a builder starts acting like cached domain object or repository, wrong layer.

Base patterns to preserve

Builder::fromPart(Part $part)

This is bridge from stored part data into editable payload state. Preserve it when adding new builder properties or part fields. Edit flows depend on this symmetry.

DynamicPropertyMutatorTrait

Builder property access uses property-level mutators like:

• setContent()
• getContent()

Not part-style getContentAttribute(). Keep that distinction.

From outside the builder, $builder->content, isset($builder->content) and ?? all go through getContent(): a property is set when its getter returns non-null, and a property with no getter is never set. Declare every property a builder stores. An undeclared one makes $this->x = ... inside setX() re-enter __set() and create a deprecated dynamic property, and makes isset($this->x) go through __isset().

new() factory

Most builders expose new() for userland ergonomics. Preserve pattern when adding new top-level builders.

create($repository) helper

Newer builders often let callers hand the builder to a repository directly. Prefer keeping that path because it nudges users away from raw arrays.

Validation rules

Validation should live as close as possible to setter/add method that introduces invalid state.

Good examples already in repo:

• message content length limits
• modal title and custom id length limits
• max embeds/components counts
• valid channel type enums
• valid video quality modes

Do not rely on far-away repository methods to catch simple builder invariants.

Serialization rules

jsonSerialize() is canonical outbound shape

This is where builder translates fluent internal state into Discord payload array. Keep it:

• explicit
• ordered enough to read
• faithful to API docs
• selective about optionals

Omit unset optionals when possible

Many Discord APIs treat missing field differently from explicit null. Builders should usually omit properties that were never set unless API specifically wants null.

Normalize nested builder or part inputs

If builder accepts nested objects:

• serialize nested builders
• convert parts to raw attributes or IDs where appropriate
• keep final payload JSON-friendly

Boundaries with parts and repositories

Builder vs part

• part = canonical resource model received from Discord or stored in memory
• builder = request payload authoring tool

Do not move outbound validation rules into parts if there is already a builder abstraction.

Builder vs repository

• builder prepares payload
• repository performs REST call

Repositories should not become payload authoring zones full of hand-built nested arrays if builder exists.

Component-specific rules

Component system exists in both builder and part worlds:

• builder components under src/Discord/Builders/Components/*
• inbound message component parts under src/Discord/Parts/Channel/Message/*

Keep these worlds aligned conceptually, but do not collapse them into one class family. Outbound builders and inbound parts solve different problems.

ComponentObject::TYPES

If new outbound component subtype appears:

1. add constant
2. add map entry
3. add class
4. check matching inbound component family if relevant
5. update builders using components

Usage contexts

Component usage constraints matter:

• message
• modal
• interaction contexts

Where repo already encodes allowed contexts, keep validation there instead of free-form component insertion.

Builder selection guide

Add or extend a builder when:

• payload has multiple related fields
• Discord API has length/count/value limits
• nested structures are easy to get wrong by hand
• same shape is authored from several call sites

Raw array may be enough when:

• payload is tiny
• shape is stable and local
• repo does not already have builder convention for that family

But if users will author it directly or repeatedly, bias toward builder.

Existing patterns worth copying

Message builder

Best example for:

• content validation
• embeds/files/stickers/components combination
• fluent helpers
• repository create() bridge

Channel builder

Best example for:

• type-specific optional fields
• enum validation
• payload fields that differ by channel subtype

Command builder

Best example for:

• optional field omission
• payload shape depending on command type

Modal builder

Best example for:

• strict component usage constraints
• response payload shape nested under type + data

Smells

Stop if you see:

• raw arrays duplicated across many callers when builder exists
• validation postponed until after HTTP call
• builder storing cache/domain state
• repository assembling complicated payload shape that should live in builder
• mismatch between builder and part edit flow because fromPart() path no longer reflects real fields
• new component type added only on one side of builder/part system

Builder change checklist

• new property has setter/getter if public
• validation lives near write path
• jsonSerialize() includes it only when appropriate
• fromPart() behavior still makes sense
• any create($repository) helper remains correct
• component/type maps updated if subtype introduced
• tests cover invalid and valid boundary cases
• docs/examples updated if preferred public usage changed

Bottom line

Builders in this repo exist to keep outbound payload rules from leaking everywhere. If a caller has to memorize Discord payload trivia instead of relying on builder methods, builder design is unfinished.