pub mod publisher;
pub mod subscriber;

use std::sync::Arc;
use std::time::Duration;

use async_nats::jetstream::Context;
use async_nats::jetstream::stream::{Config as StreamConfig, RetentionPolicy};

use crate::config::AppConfig;
use crate::error::{AppError, AppResult};

#[derive(Clone)]
pub struct NatsQueue {
    inner: Arc<NatsQueueInner>,
}

struct NatsQueueInner {
    js: Context,
    client: async_nats::Client,
    stream_prefix: String,
    ack_wait: Duration,
    max_deliver: i64,
}

pub struct StreamHandle {
    pub name: String,
    pub subjects: Vec<String>,
}

impl NatsQueue {
    pub async fn connect(config: &AppConfig) -> AppResult<Self> {
        let url = config.nats_url()?;
        let timeout = config.nats_connection_timeout_secs()?;
        let ping_interval = config.nats_ping_interval_secs()?;
        let reconnect_delay = config.nats_reconnect_delay_secs()?;
        let max_reconnects = config.nats_max_reconnects()?;

        let mut opts = async_nats::ConnectOptions::new()
            .connection_timeout(Duration::from_secs(timeout))
            .ping_interval(Duration::from_secs(ping_interval))
            .retry_on_initial_connect()
            .max_reconnects(Some(max_reconnects))
            .reconnect_delay_callback(move |_| Duration::from_secs(reconnect_delay))
            .event_callback(|event| async move {
                match event {
                    async_nats::Event::Disconnected => {
                        tracing::warn!("nats disconnected");
                    }
                    async_nats::Event::Connected => {
                        tracing::info!("nats connected");
                    }
                    async_nats::Event::LameDuckMode => {
                        tracing::warn!("nats server entering lame duck mode");
                    }
                    _ => {}
                }
            });

        if let (Some(user), Some(pass)) = (config.nats_username()?, config.nats_password()?) {
            opts = opts.user_and_password(user, pass);
        } else if let Some(token) = config.nats_token()? {
            opts = opts.token(token);
        }

        let client = async_nats::connect_with_options(&url, opts)
            .await
            .map_err(|e| AppError::Config(format!("nats connect failed: {e}")))?;

        let js = async_nats::jetstream::new(client.clone());
        let stream_prefix = config.nats_stream_prefix()?;
        let ack_wait = config.nats_default_ack_wait_secs()?;
        let max_deliver = config.nats_default_max_deliver()?;

        tracing::info!(url = %url, "nats connected");

        Ok(Self {
            inner: Arc::new(NatsQueueInner {
                js,
                client,
                stream_prefix,
                ack_wait: Duration::from_secs(ack_wait),
                max_deliver,
            }),
        })
    }

    pub fn client(&self) -> &async_nats::Client {
        &self.inner.client
    }

    pub fn js(&self) -> &Context {
        &self.inner.js
    }

    pub fn stream_name(&self, name: &str) -> String {
        format!("{}_{}", self.inner.stream_prefix, name)
    }

    pub async fn ensure_stream(
        &self,
        name: &str,
        subjects: Vec<String>,
    ) -> AppResult<StreamHandle> {
        let stream_name = self.stream_name(name);
        let config = StreamConfig {
            name: stream_name.clone(),
            subjects,
            retention: RetentionPolicy::Limits,
            max_messages: 100_000,
            max_age: Duration::from_secs(7 * 24 * 3600),
            duplicate_window: Duration::from_secs(120),
            storage: async_nats::jetstream::stream::StorageType::File,
            ..Default::default()
        };

        self.inner
            .js
            .get_or_create_stream(config)
            .await
            .map_err(|e| AppError::Config(format!("ensure stream {stream_name} failed: {e}")))?;

        let subjects = self
            .inner
            .js
            .get_stream(&stream_name)
            .await
            .map_err(|e| AppError::Config(format!("get stream {stream_name} failed: {e}")))?
            .info()
            .await
            .map_err(|e| AppError::Config(format!("stream info {stream_name} failed: {e}")))?
            .config
            .subjects
            .clone();

        tracing::info!(stream = %stream_name, subjects = ?subjects, "stream ready");

        Ok(StreamHandle {
            name: stream_name,
            subjects,
        })
    }

    pub async fn ensure_ephemeral_stream(
        &self,
        name: &str,
        subjects: Vec<String>,
        max_age_secs: u64,
    ) -> AppResult<StreamHandle> {
        let stream_name = self.stream_name(name);
        let config = StreamConfig {
            name: stream_name.clone(),
            subjects,
            retention: RetentionPolicy::Limits,
            max_messages: 10_000,
            max_age: Duration::from_secs(max_age_secs),
            duplicate_window: Duration::from_secs(60),
            storage: async_nats::jetstream::stream::StorageType::Memory,
            ..Default::default()
        };

        self.inner
            .js
            .get_or_create_stream(config)
            .await
            .map_err(|e| AppError::Config(format!("ensure stream {stream_name} failed: {e}")))?;

        Ok(StreamHandle {
            name: stream_name,
            subjects: vec![],
        })
    }

    pub async fn delete_stream(&self, name: &str) -> AppResult<()> {
        let stream_name = self.stream_name(name);
        self.inner
            .js
            .delete_stream(&stream_name)
            .await
            .map_err(|e| AppError::Config(format!("delete stream {stream_name} failed: {e}")))?;
        Ok(())
    }
}