//! The router: every route of SPEC §7 and the layers of SPEC §14.3.1 and §8.6. The handlers are in `api/*.rs`.

use std::time::Instant;

use axum::Router;
use axum::extract::{DefaultBodyLimit, MatchedPath, Path, RawQuery, Request, State};
use axum::http::{HeaderMap, HeaderValue};
use axum::middleware::{self, Next};
use axum::response::{IntoResponse, Response};
use axum::routing::{get, post, put};

use crate::api::{
    accounts, apk, categories, devices, health, invites, landing, me, pictures, proposal,
    rate_limit, recurring, setup, sync,
};
use crate::error::{AppError, LoggedErrorCode};
use crate::{AppState, SERVER_VERSION, auth};

/// Request body limit (SPEC §8.6).
pub const BODY_LIMIT_BYTES: usize = 1024 * 1024;
/// Request body limit of `PUT /me/picture` (SPEC §8.6).
pub const PICTURE_BODY_LIMIT_BYTES: usize = 5 * 1024 * 1024;
/// Response header carrying the crate version (SPEC §14.3.1).
pub const SERVER_VERSION_HEADER: &str = "x-kvitt-server-version";

/// Builds the application.
pub fn router(state: AppState) -> Router {
    // E-1 to E-6: no authentication, no protocol check.
    let public = Router::new()
        .route("/health", get(health::get_health))
        .route("/setup/status", get(setup::get_setup_status))
        .route("/invites/accept", post(invites::accept_invite))
        .route("/i/{code}", get(landing::get_invite_landing))
        // `/i/` with an empty code: the landing page's HTML 404, not the JSON fallback.
        .route("/i/", get(empty_invite_code))
        .route("/apk/latest", get(apk::get_apk_latest))
        .route("/apk/files/{file_name}", get(apk::get_apk_file));

    // E-7 to E-33: device token (the handlers' `AuthDevice` / `AdminDevice` extractors) and `X-Kvitt-Protocol: 1`.
    let authenticated = Router::new()
        .route("/me", get(me::get_me).patch(me::patch_me))
        .route(
            "/me/picture",
            put(pictures::put_me_picture)
                .layer(DefaultBodyLimit::max(PICTURE_BODY_LIMIT_BYTES))
                .delete(pictures::delete_me_picture),
        )
        .route("/users/{user_id}/picture", get(pictures::get_user_picture))
        .route(
            "/invites",
            post(invites::create_invite).get(invites::list_invites),
        )
        .route(
            "/invites/{invite_id}",
            axum::routing::delete(invites::cancel_invite),
        )
        .route("/devices", get(devices::list_devices))
        .route(
            "/devices/{device_id}",
            axum::routing::delete(devices::revoke_device),
        )
        .route("/devices/current/push-token", put(devices::put_push_token))
        .route("/accounts", post(accounts::create_account))
        .route(
            "/accounts/{account_id}",
            axum::routing::patch(accounts::patch_account).delete(accounts::delete_account),
        )
        .route(
            "/accounts/{account_id}/archive",
            post(accounts::archive_account),
        )
        .route(
            "/accounts/{account_id}/unarchive",
            post(accounts::unarchive_account),
        )
        .route("/categories", post(categories::create_category))
        .route(
            "/categories/{category_id}",
            axum::routing::patch(categories::patch_category).delete(categories::delete_category),
        )
        .route(
            "/categories/{category_id}/archive",
            post(categories::archive_category),
        )
        .route(
            "/categories/{category_id}/unarchive",
            post(categories::unarchive_category),
        )
        .route(
            "/recurring-templates",
            post(recurring::create_recurring_template),
        )
        .route(
            "/recurring-templates/{template_id}",
            axum::routing::patch(recurring::patch_recurring_template)
                .delete(recurring::delete_recurring_template),
        )
        .route("/sync", get(sync::sync_pull).post(sync::sync_push))
        .route("/settlements/proposal", post(proposal::propose_settlement))
        .route_layer(middleware::from_fn(auth::require_protocol));

    Router::new()
        .merge(public)
        .merge(authenticated)
        .fallback(fallback)
        .layer(DefaultBodyLimit::max(BODY_LIMIT_BYTES))
        .layer(rate_limit::layer(&state))
        .layer(middleware::from_fn(log_request))
        .layer(middleware::map_response(add_server_version))
        .with_state(state)
}

/// `GET /i/`: E-4 with an empty code, which the landing handler answers with its HTML 404 page.
async fn empty_invite_code(state: State<AppState>, headers: HeaderMap) -> Response {
    landing::get_invite_landing(state, headers, Path(String::new()), RawQuery(None)).await
}

/// Unknown paths: 404 `not_found` in the error shape.
async fn fallback() -> AppError {
    AppError::not_found()
}

/// Every response carries `X-Kvitt-Server-Version` (SPEC §14.3.1).
async fn add_server_version(mut response: Response) -> Response {
    response.headers_mut().insert(
        SERVER_VERSION_HEADER,
        HeaderValue::from_static(SERVER_VERSION),
    );
    response
}

/// One log line per request with the fields SPEC §8.7 allows: method, route template (never the raw path, which can
/// hold invite codes), status, latency, device id (recorded by the auth extractor) and error code.
async fn log_request(request: Request, next: Next) -> Response {
    let method = request.method().to_string();
    let route = request
        .extensions()
        .get::<MatchedPath>()
        .map_or_else(|| "<unmatched>".to_owned(), |p| p.as_str().to_owned());
    let span = tracing::info_span!(
        "request",
        method = %method,
        route = %route,
        device_id = tracing::field::Empty
    );
    let started = Instant::now();
    let response = tracing::Instrument::instrument(next.run(request), span.clone()).await;
    let latency_ms = started.elapsed().as_secs_f64() * 1000.0;
    let status = response.status().as_u16();
    let error_code = response
        .extensions()
        .get::<LoggedErrorCode>()
        .map_or("", |c| c.0.as_str());
    span.in_scope(|| {
        tracing::info!(status, latency_ms, error_code, "request");
    });
    response.into_response()
}