docs(cpp/core): registry .md for http_request + http_get_json (issue 0110)

Frontmatter + self-doc sections (Ejemplo, Cuando usarla, Gotchas) following
the contract in .claude/rules/function_growth_and_self_docs.md. Tags include
'http', 'client', 'curl', 'network', 'registry-gap', 'helper' so FTS surfaces
them when an agent asks for HTTP / fetch / GET / Bearer.

http_get_json declares uses_functions: [http_request_cpp_core] so the
dependency is auditable via mcp__registry__fn_uses.
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2026-05-18 18:14:56 +02:00
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---
name: http_get_json
kind: function
lang: cpp
domain: core
version: "1.0.0"
purity: impure
signature: "nlohmann::json fn_http::get_json(const std::string& url, const std::string& bearer_token = \"\", int timeout_ms = 5000)"
description: "Convenience wrapper over fn_http::request for the common case: GET <url> with optional Bearer auth, expect 2xx, parse body as JSON. Returns nlohmann::json. Throws std::runtime_error on transport failure, non-2xx status, or JSON parse error. For non-GET, custom headers, or status-aware control flow use http_request directly."
tags: [http, json, client, curl, network, registry-gap, core, helper]
uses_functions:
- http_request_cpp_core
uses_types: []
returns: []
returns_optional: false
error_type: "error_go_core"
imports:
- "core/http_get_json.h"
tested: true
tests:
- "get_json: parses 200 JSON body"
- "get_json: throws on 404"
- "get_json: bearer_token reaches server"
- "get_json: throws on invalid JSON"
test_file_path: "cpp/tests/test_http_get_json.cpp"
file_path: "cpp/functions/core/http_get_json.cpp"
params:
- name: url
desc: "Full URL incl. scheme (https://api.example.com/path?q=1)."
- name: bearer_token
desc: "Optional. If non-empty, sent as Authorization: Bearer <token>. Pass empty string for unauthenticated."
- name: timeout_ms
desc: "Hard timeout. Default 5000ms."
output: "nlohmann::json — the parsed body. Whatever shape the endpoint returns (object, array, scalar). Use json[\"key\"] / .at() / .get<T>() to traverse. Throws std::runtime_error on any failure."
---
## Ejemplo
```cpp
#include "core/http_get_json.h"
try {
auto data = fn_http::get_json("https://httpbin.org/get");
std::cout << "url echoed: " << data["url"].get<std::string>() << "\n";
} catch (const std::exception& e) {
std::cerr << "fetch failed: " << e.what() << "\n";
}
```
Con Bearer token + timeout corto (sqlite_api `/api/databases`):
```cpp
auto dbs = fn_http::get_json(
"http://localhost:8484/api/databases",
std::getenv("SQLITE_API_TOKEN"),
2000);
for (const auto& db : dbs) {
std::cout << db["name"].get<std::string>() << "\n";
}
```
## Cuando usarla
- Cuando una app C++ necesita GET a un endpoint JSON y prefiere fail-fast (throw) en vez de inspeccionar `Response.status` a mano.
- Para pollers / heartbeats / health checks contra APIs internas (sqlite_api, services_api, registry_api).
- NO usar cuando necesites POST, headers custom, o distinguir entre 404 y 500 sin try/catch — usa `http_request` directo.
## Gotchas
- **Throws**, no devuelve un Result. Si llamas en un loop tight, envuelve en try/catch o tu app peta al primer 5xx.
- **Hereda gotchas de `http_request`**: requiere `curl` en PATH, sin streaming, sin cookies, TLS verify activo por defecto.
- **No reusa `get_json` cuando un endpoint devuelve algo que NO es JSON** (HTML, texto plano). La excepcion sera `invalid JSON` y perderas el status real. Usa `http_request` para esos casos.
- **`bearer_token` vacio es valido** (no se manda header). No pasar el `Authorization: Bearer ` literal — eso ya lo construye `http_request`.
- **No se ofrece `post_json`** intencionalmente — la combinatoria de POST + JSON + auth + retry es lo suficientemente rica como para que `http_request` directo sea mas claro que un wrapper con N parametros opcionales.
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---
name: http_request
kind: function
lang: cpp
domain: core
version: "1.0.0"
purity: impure
signature: "fn_http::Response fn_http::request(const fn_http::Request& req)"
description: "Generic HTTP client via cURL CLI (popen). Supports GET/POST/PUT/DELETE/PATCH, custom headers, raw body, Bearer/Basic auth shortcuts, timeout, optional TLS-verify skip. Portable across Linux / WSL / MinGW — requires only `curl` in PATH at runtime, no link-time libcurl. Returns status, body, response headers, error, duration_ms. Replaces inline curl-popen patterns in apps/services_monitor, dag_engine_ui, data_factory."
tags: [http, client, curl, network, registry-gap, core, helper]
uses_functions: []
uses_types: []
returns: []
returns_optional: false
error_type: "error_go_core"
imports:
- "core/http_request.h"
tested: true
tests:
- "request: GET 200 status + body"
- "request: GET 404 status (HTTP error not transport)"
- "request: POST with body + content-type header"
- "request: bearer_token shortcut adds Authorization header"
- "request: basic_user/basic_pass shortcut authenticates"
- "request: invalid URL surfaces transport error"
- "request: timeout_ms honored"
test_file_path: "cpp/tests/test_http_request.cpp"
file_path: "cpp/functions/core/http_request.cpp"
params:
- name: req
desc: "Request struct: method (GET/POST/PUT/DELETE/PATCH, empty defaults to GET), url (full URL incl. scheme), headers (vector of {key,value}), body (raw request body bytes), timeout_ms (hard timeout, default 5000), bearer_token (shortcut for Authorization: Bearer), basic_user + basic_pass (shortcut for HTTP Basic, curl --user), insecure (bool — skip TLS verify, TESTING ONLY)."
output: "Response struct: status (HTTP code; 0 = transport error), body (response bytes), headers (vector of {key,value} as returned by server), error (empty on success, populated on transport failure / non-zero curl exit), duration_ms (wall clock of the call)."
---
## Ejemplo
```cpp
#include "core/http_request.h"
fn_http::Request req;
req.method = "GET";
req.url = "https://httpbin.org/get";
req.headers = {{"Accept", "application/json"}};
req.timeout_ms = 3000;
fn_http::Response res = fn_http::request(req);
if (!res.error.empty()) {
fprintf(stderr, "transport error: %s\n", res.error.c_str());
} else if (res.status / 100 != 2) {
fprintf(stderr, "http %d: %s\n", res.status, res.body.c_str());
} else {
printf("OK %d (%lld ms): %.200s\n", res.status,
(long long)res.duration_ms, res.body.c_str());
}
```
POST con JSON + Bearer auth:
```cpp
fn_http::Request req;
req.method = "POST";
req.url = "https://api.example.com/items";
req.headers = {{"Content-Type", "application/json"}};
req.body = R"({"name":"hello"})";
req.bearer_token = std::getenv("API_TOKEN");
auto res = fn_http::request(req);
```
## Cuando usarla
- Cuando una app C++ necesita hablar HTTP con un endpoint (REST API local, servicio en VPS, webhook).
- Antes de copiar otra vez el patron `popen("curl -s ...")` desde `apps/services_monitor/http_client.cpp` o `apps/dag_engine_ui/main.cpp` — esto es exactamente la promocion que hace falta (issue 0110).
- Como base para wrappers JSON especificos (`http_get_json` ya existe; los siguientes deberian apilarse encima de `request`, no de curl directo).
## Gotchas
- **Requiere `curl` en `PATH`** en runtime. No hay fallback; si falta, `Response.error` lo dice y `status==0`.
- **Sin streaming**: la respuesta entera entra en memoria. No usar para downloads grandes (>50 MB).
- **`insecure=true` desactiva TLS verify** — solo para tests contra mocks self-signed. NUNCA en produccion.
- **Status `0` significa transport error** (DNS, conexion rechazada, timeout, curl ausente). Status `>=400` es respuesta HTTP normal — el caller decide si es fallo.
- **Headers son case-insensitive en HTTP**; aqui los devolvemos tal como los manda el servidor. Si necesitas lookup case-insensitive, normaliza en el caller.
- **Body multipart / form-encoded**: no implementado como shortcut. Construye el body a mano y setea `Content-Type` apropiado en `headers`.
- **Cookies**: no se mantienen sesion. Cada llamada es independiente. Si necesitas cookie jar, pasala via header `Cookie` explicito.
- **Shell injection**: los argumentos pasan via `popen` con quoting POSIX (single-quote escape). URLs y headers con comillas raras se manejan bien, pero NO pases input no confiable como `url` si el binario corre con privilegios.