use std::sync::Arc;

use axum::extract::DefaultBodyLimit;
use axum::http::{HeaderName, HeaderValue, Method};
use axum::Router;
use sqlx::postgres::PgPoolOptions;
use sqlx::PgPool;
use tower_http::cors::{AllowOrigin, CorsLayer};
use tower_http::trace::TraceLayer;

use crate::config::{AuthConfig, Config, UploadConfig};
use crate::storage::{LocalStorage, Storage};

#[derive(Clone)]
pub struct AppState {
    pub db: PgPool,
    pub storage: Arc<dyn Storage>,
    pub auth: AuthConfig,
    pub upload: UploadConfig,
}

pub async fn build(config: Config) -> anyhow::Result<Router> {
    let db = PgPoolOptions::new()
        .max_connections(10)
        .connect(&config.database_url)
        .await?;
    sqlx::migrate!("./migrations").run(&db).await?;

    let storage: Arc<dyn Storage> = Arc::new(LocalStorage::new(config.storage_dir.clone()));

    let state = AppState {
        db,
        storage,
        auth: config.auth.clone(),
        upload: config.upload.clone(),
    };
    Ok(router(state).layer(cors_layer(&config.cors_allowed_origins)))
}

/// Build a router from a pre-assembled state. Used by integration tests
/// so they can swap in a test DB pool and a `tempfile`-backed storage.
pub fn router(state: AppState) -> Router {
    let max_request_bytes = state.upload.max_request_bytes;
    Router::new()
        .nest("/api/v1", crate::api::routes())
        .layer(DefaultBodyLimit::max(max_request_bytes))
        .with_state(state)
        .layer(TraceLayer::new_for_http())
}

pub(crate) fn cors_layer(allowed_origins: &[String]) -> CorsLayer {
    if allowed_origins.is_empty() {
        // Same-origin only — no CORS headers emitted.
        return CorsLayer::new();
    }
    let origins: Vec<HeaderValue> = allowed_origins
        .iter()
        .filter_map(|o| HeaderValue::from_str(o).ok())
        .collect();
    CorsLayer::new()
        .allow_origin(AllowOrigin::list(origins))
        .allow_credentials(true)
        .allow_methods([Method::GET, Method::POST, Method::PUT, Method::DELETE])
        .allow_headers([
            HeaderName::from_static("content-type"),
            HeaderName::from_static("authorization"),
        ])
}

#[cfg(test)]
mod tests {
    use super::*;
    use axum::body::Body;
    use axum::http::Request;
    use axum::routing::get;
    use tower::ServiceExt;

    fn test_router() -> Router {
        Router::new().route("/", get(|| async { "ok" }))
    }

    #[tokio::test]
    async fn allowlist_preflight_emits_credentialed_headers() {
        let app = test_router().layer(cors_layer(&["https://app.example.com".to_string()]));
        let resp = app
            .oneshot(
                Request::builder()
                    .method(Method::OPTIONS)
                    .uri("/")
                    .header("origin", "https://app.example.com")
                    .header("access-control-request-method", "POST")
                    .body(Body::empty())
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(
            resp.headers().get("access-control-allow-origin").unwrap(),
            "https://app.example.com"
        );
        assert_eq!(
            resp.headers().get("access-control-allow-credentials").unwrap(),
            "true"
        );
    }

    #[tokio::test]
    async fn allowlist_rejects_unlisted_origin() {
        let app = test_router().layer(cors_layer(&["https://app.example.com".to_string()]));
        let resp = app
            .oneshot(
                Request::builder()
                    .method(Method::OPTIONS)
                    .uri("/")
                    .header("origin", "https://evil.example.org")
                    .header("access-control-request-method", "POST")
                    .body(Body::empty())
                    .unwrap(),
            )
            .await
            .unwrap();
        // Browsers will refuse the response when the allow-origin header
        // is absent (or doesn't echo the requesting origin).
        assert!(resp.headers().get("access-control-allow-origin").is_none());
    }

    #[tokio::test]
    async fn empty_allowlist_is_same_origin_only() {
        let app = test_router().layer(cors_layer(&[]));
        let resp = app
            .oneshot(
                Request::builder()
                    .method(Method::OPTIONS)
                    .uri("/")
                    .header("origin", "https://app.example.com")
                    .header("access-control-request-method", "POST")
                    .body(Body::empty())
                    .unwrap(),
            )
            .await
            .unwrap();
        assert!(resp.headers().get("access-control-allow-origin").is_none());
        assert!(resp.headers().get("access-control-allow-credentials").is_none());
    }
}