//! HTTP API: router, OpenAPI document and shared response helpers.

pub(crate) mod auth;
mod debug;
mod document;
mod log;
mod peers;
mod stats;
mod store;

use axum::{
    Json, Router,
    extract::State,
    http::{
        HeaderValue, StatusCode,
        header::{CONTENT_TYPE, ETAG},
    },
    response::{IntoResponse, Response},
    routing::{delete, get, put},
};
use serde_json::Value as JsonValue;
use sha2::{Digest, Sha256};
use tracing::{error, warn};
use utoipa::OpenApi;
use utoipa_swagger_ui::SwaggerUi;

use crate::api::auth::{AuthState, AuthenticatedUser, basic_auth};
use crate::document::store::StoreError;
use crate::state::AppState;

/// Builds the complete HTTP router. Everything except Swagger is authenticated.
pub(crate) fn router(state: AppState, auth_state: AuthState, debug_api: bool) -> Router {
    let mut api: Router<AppState> = Router::new()
        .route("/store", get(store::get_store_root))
        .route(
            "/store/{*key}",
            get(store::get_store_entry)
                .put(store::put_store_entry)
                .delete(store::delete_store_entry),
        )
        .route("/stream/{*key}", get(store::stream_store_entry))
        .route("/peers", get(peers::list_peers))
        .route("/peers/{peer}", delete(peers::delete_peer))
        .route(
            "/admin/log",
            get(log::get_log_filter).put(log::put_log_filter),
        )
        .route("/admin/stats", get(stats::get_stats))
        .route("/admin/document", get(document::get_document))
        .route("/admin/config", get(get_config))
        .merge(crate::remake::router::<AppState>());

    if debug_api {
        warn!("Debug API enabled");
        api = api
            .route(
                "/debug/firewall",
                get(debug::get_debug_firewall).put(debug::put_debug_firewall),
            )
            .route("/debug/blacklist", put(debug::put_debug_blacklist));
    }

    api.layer(axum::middleware::from_fn_with_state(auth_state, basic_auth))
        .merge(SwaggerUi::new("/swagger-ui").url("/openapi.json", ApiDoc::openapi()))
        .with_state(state)
}

/// `GET /admin/config`: the effective configuration with each value's source;
/// imported values are left out.
async fn get_config(State(state): State<AppState>) -> Json<JsonValue> {
    Json((*state.config).clone())
}

// --- shared helpers ----------------------------------------------------------

pub(crate) fn store_status(error: StoreError, context: &str) -> StatusCode {
    match error {
        StoreError::Conflict => StatusCode::CONFLICT,
        StoreError::NotFound => StatusCode::NOT_FOUND,
        other => {
            error!(error = %format!("{other:#}"), "{context}");
            StatusCode::INTERNAL_SERVER_ERROR
        }
    }
}

fn etag_for(bytes: &[u8]) -> String {
    let digest = Sha256::digest(bytes);
    let hex = digest
        .iter()
        .map(|byte| format!("{byte:02x}"))
        .collect::<String>();

    format!("\"{hex}\"")
}

fn parse_key_path(key: &str) -> Result<Vec<String>, StatusCode> {
    let segments: Vec<String> = key.split('/').map(str::to_owned).collect();

    if segments.is_empty() || segments.iter().any(|segment| segment.is_empty()) {
        return Err(StatusCode::BAD_REQUEST);
    }

    Ok(segments)
}

/// A path for a write. Protocol data (`_continuum`: remake records, members, forget
/// records, epoch metadata) is what every node acts on, so a write there acts on the
/// whole swarm: only users listed in `--protocol-writers` may, and each such write is
/// logged. Epoch metadata (and `_continuum` as a whole, which contains it) is never
/// writable: the protocol reads it at the snapshot change, so an edit only misleads
/// whoever reads it later. `403` otherwise.
fn parse_write_path(
    state: &AppState,
    user: &AuthenticatedUser,
    key: &str,
    method: &str,
) -> Result<Vec<String>, StatusCode> {
    let path = parse_key_path(key)?;
    if path.first().map(String::as_str) != Some(crate::remake::snapshot::META_ROOT) {
        return Ok(path);
    }
    let epochs = path.len() < 2 || path[1] == crate::remake::snapshot::EPOCHS;
    if epochs || !state.protocol_writers.contains(&user.0) {
        warn!(user = %user.0, method, path = %key, "Refused a write to protocol data");
        return Err(StatusCode::FORBIDDEN);
    }
    warn!(user = %user.0, method, path = %key, "Protocol data written through the store API; this acts on the whole swarm");
    Ok(path)
}

fn response_for_value(
    value: &JsonValue,
    accept: Option<&HeaderValue>,
) -> Result<Response, StatusCode> {
    let wants_text = accept
        .and_then(|value| value.to_str().ok())
        .is_some_and(|value| {
            value
                .split(',')
                .any(|item| item.trim().starts_with("text/plain"))
        });

    let (content_type, body) = if wants_text {
        let body = match value {
            JsonValue::String(value) => value.clone(),
            other => serde_json::to_string(other).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
        };

        ("text/plain; charset=utf-8", body)
    } else {
        (
            "application/json",
            serde_json::to_string(value).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
        )
    };

    let etag = etag_for(body.as_bytes());

    let mut response = body.into_response();

    response
        .headers_mut()
        .insert(CONTENT_TYPE, HeaderValue::from_static(content_type));

    response.headers_mut().insert(
        ETAG,
        HeaderValue::from_str(&etag).map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?,
    );

    Ok(response)
}

// --- openapi spec ------------------------------------------------------------
// TODO spec is mostly out of sync

#[derive(OpenApi)]
#[openapi(
    paths(
        store::get_store_root,
        store::get_store_entry,
        store::put_store_entry,
        store::delete_store_entry,
        peers::list_peers,
        peers::delete_peer,
    ),
    components(
        schemas(
            peers::PeerStatus,
            peers::PeerListResponse,
            peers::PeerLivenessStatus,
            peers::EpochInfo,
            crate::transport::traffic::PeerTraffic,
            crate::transport::traffic::ByKind,
            crate::transport::traffic::Counter,
            crate::state::Incidents,
            peers::ThroughputInfo,
        )
    ),
    tags(
        (name = "Store", description = "Key-value store operations"),
        (name = "Peers", description = "Peer discovery and retirement")
    ),
    info(
        title = "Automerge Replication API",
        version = "1.0.0",
        description = "HTTP API for a replicated Automerge key-value store"
    )
)]
struct ApiDoc;