# Changelog

All notable changes to this module will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this module adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [0.9.0] - 2026-03-18

### Added

- `Handle[Req, Res any](v valid.Validator, fn func(ctx context.Context, req Req) (Res, error)) http.HandlerFunc` — decodes the JSON request body into `Req`, validates it with the injected `Validator`, calls `fn`, and encodes the result as JSON with HTTP 200; invalid JSON returns 400
- `HandleNoBody[Res any](fn func(ctx context.Context) (Res, error)) http.HandlerFunc` — no body decode or validation; calls `fn` and encodes the result as JSON with HTTP 200; intended for GET and DELETE endpoints
- `HandleEmpty[Req any](v valid.Validator, fn func(ctx context.Context, req Req) error) http.HandlerFunc` — decodes and validates the JSON request body, calls `fn`, returns HTTP 204 on success; intended for write endpoints with no response body
- `HandlerFunc` type — `func(w http.ResponseWriter, r *http.Request) error`; implements `http.Handler`; on non-nil return, routes the error through `Error(w, err)` for automatic status mapping
- `JSON(w http.ResponseWriter, status int, v any)` — encodes `v` as JSON and writes it with the given status code; sets `Content-Type: application/json`
- `NoContent(w http.ResponseWriter)` — writes HTTP 204 No Content
- `Error(w http.ResponseWriter, err error)` — maps `*xerrors.Err` codes to HTTP status codes and writes a `{"code": "...", "message": "..."}` JSON body; includes any extra fields from the error; falls back to 500 for unknown errors
- `xerrors.Code` to HTTP status mapping (12 codes): `ErrInvalidInput` → 400, `ErrUnauthorized` → 401, `ErrPermissionDenied` → 403, `ErrNotFound` → 404, `ErrAlreadyExists` → 409, `ErrGone` → 410, `ErrPreconditionFailed` → 412, `ErrRateLimited` → 429, `ErrInternal` → 500, `ErrNotImplemented` → 501, `ErrUnavailable` → 503, `ErrDeadlineExceeded` → 504

### Design Notes

- Business functions wrapped by `Handle`, `HandleNoBody`, and `HandleEmpty` have no `http.ResponseWriter` or `*http.Request` in their signatures, making them callable directly in unit tests with `context.Background()` and a typed request value.
- `Error` is the single translation point from `xerrors.Code` to HTTP status; all handler adapters route through it, preventing fragmented status code contracts across the codebase.
- Validation is injected via `valid.Validator` and runs before the business function is called; an invalid request never reaches business logic.

[0.9.0]: https://code.nochebuena.dev/go/httputil/releases/tag/v0.9.0