//! `RealtimeAuthorityImpl` — the DB-backed SSE subscribe gate (v1.1.6).
//!
//! Backs the [`picloud_shared::RealtimeAuthority`] trait the SSE handler
//! in orchestrator-core calls. All `topics`-table reads and signing-key
//! material stay inside this impl so the data-plane crate never touches
//! the key.
//!
//! Verdict mapping (see [`SubscribeDenied`]):
//!   * topic missing OR not externally subscribable → `NotFound` (404).
//!     Both collapse to 404 so the endpoint can't probe internal topics.
//!   * `auth_mode = 'public'` → allow.
//!   * `auth_mode = 'token'` → verify the HMAC token (present, signed by
//!     this app's key, unexpired, scoped to this topic) → allow, else
//!     `Unauthorized` (401, generic — never says which check failed).
//!
//! Signing keys never change in v1.1.6 (no rotation API), so a small
//! in-memory cache avoids a per-subscribe DB read once an app's key has
//! been seen. The cache is purely an optimization — a cold miss reads
//! the row.

use std::collections::HashMap;
use std::sync::{Arc, Mutex};

use async_trait::async_trait;
use picloud_shared::{subscriber_token, AppId, RealtimeAuthority, SubscribeDenied};

use crate::app_secrets_repo::AppSecretsRepo;
use crate::topic_repo::{TopicAuthMode, TopicRepo};

pub struct RealtimeAuthorityImpl {
    topics: Arc<dyn TopicRepo>,
    secrets: Arc<dyn AppSecretsRepo>,
    key_cache: Mutex<HashMap<AppId, Vec<u8>>>,
}

impl RealtimeAuthorityImpl {
    #[must_use]
    pub fn new(topics: Arc<dyn TopicRepo>, secrets: Arc<dyn AppSecretsRepo>) -> Self {
        Self {
            topics,
            secrets,
            key_cache: Mutex::new(HashMap::new()),
        }
    }

    /// Fetch the app's signing key, consulting the cache first. Returns
    /// `None` when the app has no key (no token ever minted) — which the
    /// caller maps to `Unauthorized`.
    async fn signing_key(&self, app_id: AppId) -> Result<Option<Vec<u8>>, SubscribeDenied> {
        if let Ok(cache) = self.key_cache.lock() {
            if let Some(k) = cache.get(&app_id) {
                return Ok(Some(k.clone()));
            }
        }
        let key = self
            .secrets
            .signing_key(app_id)
            .await
            .map_err(|e| SubscribeDenied::Backend(e.to_string()))?;
        if let Some(ref k) = key {
            if let Ok(mut cache) = self.key_cache.lock() {
                cache.insert(app_id, k.clone());
            }
        }
        Ok(key)
    }
}

#[async_trait]
impl RealtimeAuthority for RealtimeAuthorityImpl {
    async fn authorize_subscribe(
        &self,
        app_id: AppId,
        topic: &str,
        token: Option<&str>,
    ) -> Result<(), SubscribeDenied> {
        let registered = self
            .topics
            .get(app_id, topic)
            .await
            .map_err(|e| SubscribeDenied::Backend(e.to_string()))?;

        // Missing topic AND internal-only topic both 404 — don't leak
        // which internal topics exist.
        let Some(t) = registered.filter(|t| t.external_subscribable) else {
            return Err(SubscribeDenied::NotFound);
        };

        match t.auth_mode {
            TopicAuthMode::Public => Ok(()),
            TopicAuthMode::Token => {
                let token = token.ok_or(SubscribeDenied::Unauthorized)?;
                let key = self
                    .signing_key(app_id)
                    .await?
                    .ok_or(SubscribeDenied::Unauthorized)?;
                let now = chrono::Utc::now().timestamp();
                let claims = subscriber_token::verify(&key, token, now)
                    .map_err(|_| SubscribeDenied::Unauthorized)?;
                // Per-app key already makes a cross-app token fail the
                // signature check; this is belt-and-suspenders.
                if claims.app_id != app_id || !claims.allows_topic(topic) {
                    return Err(SubscribeDenied::Unauthorized);
                }
                Ok(())
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::app_secrets_repo::AppSecretsRepoError;
    use crate::topic_repo::{Topic, TopicRepoError};
    use chrono::Utc;
    use picloud_shared::subscriber_token::{sign, TokenClaims};

    struct FakeTopics(Vec<(AppId, Topic)>);
    #[async_trait]
    impl TopicRepo for FakeTopics {
        async fn create(
            &self,
            _: AppId,
            _: &str,
            _: bool,
            _: TopicAuthMode,
        ) -> Result<Topic, TopicRepoError> {
            unimplemented!()
        }
        async fn list(&self, _: AppId) -> Result<Vec<Topic>, TopicRepoError> {
            unimplemented!()
        }
        async fn get(&self, app_id: AppId, name: &str) -> Result<Option<Topic>, TopicRepoError> {
            Ok(self
                .0
                .iter()
                .find(|(a, t)| *a == app_id && t.name == name)
                .map(|(_, t)| t.clone()))
        }
        async fn update(
            &self,
            _: AppId,
            _: &str,
            _: Option<bool>,
            _: Option<TopicAuthMode>,
        ) -> Result<Option<Topic>, TopicRepoError> {
            unimplemented!()
        }
        async fn delete(&self, _: AppId, _: &str) -> Result<bool, TopicRepoError> {
            unimplemented!()
        }
    }

    struct FakeSecrets(AppId, Vec<u8>);
    #[async_trait]
    impl AppSecretsRepo for FakeSecrets {
        async fn get_or_create_signing_key(
            &self,
            _: AppId,
        ) -> Result<Vec<u8>, AppSecretsRepoError> {
            Ok(self.1.clone())
        }
        async fn signing_key(&self, app_id: AppId) -> Result<Option<Vec<u8>>, AppSecretsRepoError> {
            Ok((app_id == self.0).then(|| self.1.clone()))
        }
    }

    fn topic(name: &str, external: bool, mode: TopicAuthMode) -> Topic {
        Topic {
            name: name.to_string(),
            external_subscribable: external,
            auth_mode: mode,
            created_at: Utc::now(),
            updated_at: Utc::now(),
        }
    }

    fn authority(
        topics: Vec<(AppId, Topic)>,
        key_app: AppId,
        key: Vec<u8>,
    ) -> RealtimeAuthorityImpl {
        RealtimeAuthorityImpl::new(
            Arc::new(FakeTopics(topics)),
            Arc::new(FakeSecrets(key_app, key)),
        )
    }

    #[tokio::test]
    async fn missing_topic_is_not_found() {
        let app = AppId::new();
        let a = authority(vec![], app, vec![0u8; 32]);
        assert_eq!(
            a.authorize_subscribe(app, "ghost", None).await,
            Err(SubscribeDenied::NotFound)
        );
    }

    #[tokio::test]
    async fn internal_only_topic_is_not_found() {
        let app = AppId::new();
        let a = authority(
            vec![(app, topic("internal", false, TopicAuthMode::Public))],
            app,
            vec![0u8; 32],
        );
        assert_eq!(
            a.authorize_subscribe(app, "internal", None).await,
            Err(SubscribeDenied::NotFound)
        );
    }

    #[tokio::test]
    async fn public_topic_allows_without_token() {
        let app = AppId::new();
        let a = authority(
            vec![(app, topic("news", true, TopicAuthMode::Public))],
            app,
            vec![0u8; 32],
        );
        assert!(a.authorize_subscribe(app, "news", None).await.is_ok());
    }

    #[tokio::test]
    async fn token_topic_without_token_is_unauthorized() {
        let app = AppId::new();
        let a = authority(
            vec![(app, topic("chat", true, TopicAuthMode::Token))],
            app,
            vec![7u8; 32],
        );
        assert_eq!(
            a.authorize_subscribe(app, "chat", None).await,
            Err(SubscribeDenied::Unauthorized)
        );
    }

    #[tokio::test]
    async fn token_topic_with_valid_token_allows() {
        let app = AppId::new();
        let key = vec![9u8; 32];
        let a = authority(
            vec![(app, topic("chat", true, TopicAuthMode::Token))],
            app,
            key.clone(),
        );
        let token = sign(
            &key,
            &TokenClaims {
                app_id: app,
                topics: vec!["chat".into()],
                iat: Utc::now().timestamp(),
                exp: Utc::now().timestamp() + 60,
            },
        );
        assert!(a
            .authorize_subscribe(app, "chat", Some(&token))
            .await
            .is_ok());
    }

    #[tokio::test]
    async fn token_for_other_topic_is_unauthorized() {
        let app = AppId::new();
        let key = vec![9u8; 32];
        let a = authority(
            vec![(app, topic("chat", true, TopicAuthMode::Token))],
            app,
            key.clone(),
        );
        let token = sign(
            &key,
            &TokenClaims {
                app_id: app,
                topics: vec!["other".into()],
                iat: Utc::now().timestamp(),
                exp: Utc::now().timestamp() + 60,
            },
        );
        assert_eq!(
            a.authorize_subscribe(app, "chat", Some(&token)).await,
            Err(SubscribeDenied::Unauthorized)
        );
    }

    #[tokio::test]
    async fn expired_token_is_unauthorized() {
        let app = AppId::new();
        let key = vec![9u8; 32];
        let a = authority(
            vec![(app, topic("chat", true, TopicAuthMode::Token))],
            app,
            key.clone(),
        );
        let token = sign(
            &key,
            &TokenClaims {
                app_id: app,
                topics: vec!["chat".into()],
                iat: Utc::now().timestamp() - 120,
                exp: Utc::now().timestamp() - 60,
            },
        );
        assert_eq!(
            a.authorize_subscribe(app, "chat", Some(&token)).await,
            Err(SubscribeDenied::Unauthorized)
        );
    }

    #[tokio::test]
    async fn token_signed_by_other_app_key_is_unauthorized() {
        let app_a = AppId::new();
        let app_b = AppId::new();
        let key_a = vec![1u8; 32];
        let key_b = vec![2u8; 32];
        // Authority for app B; its key is key_b.
        let a = authority(
            vec![(app_b, topic("chat", true, TopicAuthMode::Token))],
            app_b,
            key_b,
        );
        // Token signed by app A's key, claiming app A.
        let token = sign(
            &key_a,
            &TokenClaims {
                app_id: app_a,
                topics: vec!["chat".into()],
                iat: Utc::now().timestamp(),
                exp: Utc::now().timestamp() + 60,
            },
        );
        assert_eq!(
            a.authorize_subscribe(app_b, "chat", Some(&token)).await,
            Err(SubscribeDenied::Unauthorized)
        );
    }
}