use crate::database::EntityRepository;
use axum::{
    Router,
    extract::{Path, State},
    http::StatusCode,
    response::{IntoResponse, Response},
    routing::get,
};
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::RwLock;
use tracing::{debug, error, info};

mod backstage;

struct CachedResponse {
    data: String,
    cached_at: Instant,
}

/// State shared across YAML adapter handlers
#[derive(Clone)]
pub struct YamlAdapterState {
    pub repository: Arc<EntityRepository>,
    pub base_url: String,
    cache: Arc<RwLock<Option<CachedResponse>>>,
    cache_ttl: Duration,
}

impl YamlAdapterState {
    /// Invalidate the locations cache (for event-based invalidation on entity changes)
    pub async fn invalidate_cache(&self) {
        let mut cache = self.cache.write().await;
        *cache = None;
    }
}

/// Start the YAML adapter HTTP server
pub async fn start_yaml_adapter(
    host: String,
    port: u16,
    repository: Arc<EntityRepository>,
    base_url: String,
) -> Result<(), Box<dyn std::error::Error>> {
    let state = YamlAdapterState {
        repository,
        base_url,
        cache: Arc::new(RwLock::new(None)),
        cache_ttl: Duration::from_secs(30),
    };

    let app = Router::new()
        .route("/yaml/locations", get(get_locations))
        .route("/yaml/entities/:id", get(get_entity))
        .with_state(state);

    let addr = format!("{}:{}", host, port);
    info!("Starting YAML adapter HTTP server on {}", addr);

    let listener = tokio::net::TcpListener::bind(&addr).await?;
    axum::serve(listener, app).await?;

    Ok(())
}

/// GET /yaml/locations
/// Returns a Backstage Location entity listing all entities in Charybdis
async fn get_locations(State(state): State<YamlAdapterState>) -> Response {
    info!("Received GET /yaml/locations request");

    // Check cache first
    {
        let cache = state.cache.read().await;
        if let Some(ref cached) = *cache {
            if cached.cached_at.elapsed() < state.cache_ttl {
                debug!("Serving /yaml/locations from cache");
                return (
                    StatusCode::OK,
                    [("content-type", "text/yaml; charset=utf-8")],
                    cached.data.clone(),
                )
                    .into_response();
            }
        }
    }

    // Cache miss or expired — fetch from database
    match state.repository.list_all().await {
        Ok(entities) => {
            let location_yaml = backstage::create_location_yaml(&entities, &state.base_url);

            // Update cache
            {
                let mut cache = state.cache.write().await;
                *cache = Some(CachedResponse {
                    data: location_yaml.clone(),
                    cached_at: Instant::now(),
                });
            }

            (
                StatusCode::OK,
                [("content-type", "text/yaml; charset=utf-8")],
                location_yaml,
            )
                .into_response()
        }
        Err(e) => {
            error!(error = %e, "Failed to list entities for location");
            (
                StatusCode::INTERNAL_SERVER_ERROR,
                "Failed to retrieve entities",
            )
                .into_response()
        }
    }
}

/// GET /yaml/entities/:id
/// Returns a specific entity in Backstage YAML format
async fn get_entity(Path(id): Path<String>, State(state): State<YamlAdapterState>) -> Response {
    info!(entity_id = %id, "Received GET /yaml/entities/:id request");

    match state.repository.get_by_id(&id).await {
        Ok(Some(entity)) => match backstage::entity_to_yaml(&entity) {
            Ok(yaml) => (
                StatusCode::OK,
                [("content-type", "text/yaml; charset=utf-8")],
                yaml,
            )
                .into_response(),
            Err(e) => {
                error!(entity_id = %id, error = %e, "Failed to convert entity to YAML");
                (
                    StatusCode::INTERNAL_SERVER_ERROR,
                    "Failed to convert entity to YAML",
                )
                    .into_response()
            }
        },
        Ok(None) => {
            info!(entity_id = %id, "Entity not found");
            (StatusCode::NOT_FOUND, "Entity not found").into_response()
        }
        Err(e) => {
            error!(entity_id = %id, error = %e, "Failed to retrieve entity");
            (
                StatusCode::INTERNAL_SERVER_ERROR,
                "Failed to retrieve entity",
            )
                .into_response()
        }
    }
}