truelayer-interview/tests/app.rs

use axum::{
    body::{Body, to_bytes},
    http::{Request, StatusCode, header::HeaderName},
};
use pokedex_api::{
    http::{AppState, create_app},
    pokemon::PokeApiClient,
    rate_limit::RateLimiter,
    service::PokedexService,
    telemetry::Telemetry,
    translation::TranslationClient,
};
use serde_json::Value;
use std::time::Duration;
use tower::ServiceExt;
use wiremock::{Mock, MockServer, ResponseTemplate, matchers};

#[tokio::test]
async fn health_endpoint_reports_ok() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/health"))
        .await
        .expect("request should be handled");

    assert_eq!(response.status(), StatusCode::OK);
    assert_eq!(
        json_body(response).await,
        serde_json::json!({ "status": "ok" })
    );
}

#[tokio::test]
async fn pokemon_endpoint_returns_basic_pokemon_information() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    mount_species(&pokeapi, "mewtwo", true, "rare", "Created by science.").await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/pokemon/mewtwo"))
        .await
        .expect("request should be handled");

    assert_eq!(response.status(), StatusCode::OK);
    assert_eq!(
        json_body(response).await,
        serde_json::json!({
            "name": "mewtwo",
            "description": "Created by science.",
            "habitat": "rare",
            "isLegendary": true
        })
    );
}

#[tokio::test]
async fn pokemon_endpoint_rejects_invalid_names_before_calling_upstream() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/pokemon/foo%3Fbar=baz"))
        .await
        .expect("request should be handled");

    assert_eq!(response.status(), StatusCode::BAD_REQUEST);
    assert_eq!(
        json_body(response).await["error"],
        "pokemon name must contain only ASCII letters, digits, or hyphens"
    );
}

#[tokio::test]
async fn translated_endpoint_returns_translated_description() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    mount_species(&pokeapi, "pikachu", false, "forest", "Electric cheeks.").await;
    Mock::given(matchers::method("POST"))
        .and(matchers::path("/translate/shakespeare.json"))
        .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
            "contents": { "translated": "Electric cheeks, prithee." }
        })))
        .mount(&translations)
        .await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/pokemon/translated/pikachu"))
        .await
        .expect("request should be handled");

    assert_eq!(response.status(), StatusCode::OK);
    assert_eq!(
        json_body(response).await["description"],
        "Electric cheeks, prithee."
    );
}

#[tokio::test]
async fn translated_endpoint_falls_back_to_original_description_when_translation_fails() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    mount_species(&pokeapi, "zubat", false, "cave", "It has no eyes.").await;
    Mock::given(matchers::method("POST"))
        .and(matchers::path("/translate/yoda.json"))
        .respond_with(ResponseTemplate::new(500))
        .mount(&translations)
        .await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/pokemon/translated/zubat"))
        .await
        .expect("request should be handled");

    assert_eq!(response.status(), StatusCode::OK);
    assert_eq!(json_body(response).await["description"], "It has no eyes.");
}

#[tokio::test]
async fn every_response_has_a_request_id() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/health"))
        .await
        .expect("request should be handled");

    assert!(response.headers().contains_key("x-request-id"));
}

#[tokio::test]
async fn keeps_incoming_request_id_when_present() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    let app = create_app(state_for(&pokeapi, &translations));
    let request = Request::builder()
        .uri("/health")
        .header(HeaderName::from_static("x-request-id"), "external-id")
        .body(Body::empty())
        .expect("request should build");

    let response = app
        .oneshot(request)
        .await
        .expect("request should be handled");

    assert_eq!(response.headers()["x-request-id"], "external-id");
}

#[tokio::test]
async fn metrics_endpoint_exposes_http_and_upstream_otel_metrics() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    mount_species(&pokeapi, "mewtwo", true, "rare", "Created by science.").await;
    let app = create_app(state_for(&pokeapi, &translations));
    let response = app
        .clone()
        .oneshot(request("/pokemon/mewtwo"))
        .await
        .expect("request should be handled");
    assert_eq!(response.status(), StatusCode::OK);

    let response = app
        .oneshot(request("/metrics"))
        .await
        .expect("request should be handled");
    let body = text_body(response).await;

    assert!(body.contains("http_server_requests"));
    assert!(body.contains("upstream_client_requests"));
}

#[tokio::test]
async fn rate_limit_rejects_requests_over_the_configured_burst() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    let telemetry = Telemetry::new("test-service");
    let app = create_app(AppState::new(
        PokedexService::new(
            PokeApiClient::new(pokeapi.uri(), Duration::from_secs(1)).expect("client should build"),
            TranslationClient::new(translations.uri(), Duration::from_secs(1))
                .expect("client should build"),
            telemetry.metrics(),
        ),
        telemetry,
        RateLimiter::new(0.01, 1).expect("rate limiter should build"),
    ));

    let first = app
        .clone()
        .oneshot(request("/health"))
        .await
        .expect("request should be handled");
    let second = app
        .oneshot(request("/health"))
        .await
        .expect("request should be handled");

    assert_eq!(first.status(), StatusCode::OK);
    assert_eq!(second.status(), StatusCode::TOO_MANY_REQUESTS);
    assert_eq!(json_body(second).await["error"], "rate limit exceeded");
}

#[tokio::test]
async fn pokemon_endpoint_maps_missing_pokemon_to_404() {
    let pokeapi = MockServer::start().await;
    let translations = MockServer::start().await;
    Mock::given(matchers::method("GET"))
        .and(matchers::path("/pokemon-species/nope"))
        .respond_with(ResponseTemplate::new(404))
        .mount(&pokeapi)
        .await;
    let app = create_app(state_for(&pokeapi, &translations));

    let response = app
        .oneshot(request("/pokemon/nope"))
        .await
        .expect("request should be handled");

    assert_eq!(response.status(), StatusCode::NOT_FOUND);
    assert_eq!(json_body(response).await["error"], "pokemon not found");
}

async fn mount_species(
    server: &MockServer,
    name: &str,
    is_legendary: bool,
    habitat: &str,
    description: &str,
) {
    Mock::given(matchers::method("GET"))
        .and(matchers::path(format!("/pokemon-species/{name}")))
        .respond_with(ResponseTemplate::new(200).set_body_json(serde_json::json!({
            "name": name,
            "is_legendary": is_legendary,
            "habitat": { "name": habitat },
            "flavor_text_entries": [
                { "flavor_text": description, "language": { "name": "en" } }
            ]
        })))
        .mount(server)
        .await;
}

fn state_for(pokeapi: &MockServer, translations: &MockServer) -> AppState {
    let telemetry = Telemetry::new("test-service");
    AppState::new(
        PokedexService::new(
            PokeApiClient::new(pokeapi.uri(), Duration::from_secs(1)).expect("client should build"),
            TranslationClient::new(translations.uri(), Duration::from_secs(1))
                .expect("client should build"),
            telemetry.metrics(),
        ),
        telemetry,
        RateLimiter::new(100.0, 100).expect("rate limiter should build"),
    )
}

fn request(path: &str) -> Request<Body> {
    Request::builder()
        .uri(path)
        .body(Body::empty())
        .expect("request should build")
}

async fn json_body(response: axum::response::Response) -> Value {
    let bytes = body_bytes(response).await;
    serde_json::from_slice(&bytes).expect("body should be valid JSON")
}

async fn text_body(response: axum::response::Response) -> String {
    String::from_utf8(body_bytes(response).await.to_vec()).expect("body should be valid UTF-8")
}

async fn body_bytes(response: axum::response::Response) -> axum::body::Bytes {
    to_bytes(response.into_body(), 1024 * 1024)
        .await
        .expect("body should be readable")
}