//! # services/amqp/mod.rs — AMQP Transport Module
//!
//! RabbitMQ transport layer. Provides IPL reachability validation and the
//! `AmqpConnection` struct for authenticated broker sessions.
//!
//! ## Public Surface
//! - `validate()` — TCP reachability check (IPL step 3)
//! - `AmqpConnection` — authenticated connection + channel (IPL step 3b)
//! - `EXCHANGE_NAME` — the canonical `beds.events` exchange name constant
//!
//! **Author:** mks
//! **Version:** 1.0
//!
//! ## History
//! * `2026-04-02` - mks - original coding (flat amqp.rs)
//! * `2026-04-04` - mks - promoted to services/amqp/, added AmqpConnection struct

pub mod connection;
pub mod error;

pub use connection::{AmqpConnection, EXCHANGE_NAME};
pub use error::AmqpError; // will be used by broker pool error handling

use std::net::TcpStream;
use std::time::Duration;

use crate::config::BrokerServicesConfig;

/// Validates that the RabbitMQ broker is reachable via TCP.
///
/// Opens a TCP connection to the configured broker host and port. Does not
/// authenticate or open an AMQP channel — reachability only. The connection
/// is closed immediately after a successful connect.
///
/// Called at IPL step 3 as a fast pre-flight check before the more expensive
/// `AmqpConnection::connect()` authentication step.
///
/// # Arguments
///
/// * `cfg` — broker services configuration block from `BedsConfig`
///
/// # Returns
///
/// `Ok(())` if the TCP handshake succeeds within 5 seconds.
/// `Err(String)` with a descriptive message if the broker cannot be reached.
///
/// # History
///
/// * `2026-04-02` - mks - original coding
pub fn validate(cfg: &BrokerServicesConfig) -> Result<(), String> {
    let addr_str = format!("{}:{}", cfg.app_server.host, cfg.app_server.port);

    let addr: std::net::SocketAddr = addr_str
        .parse()
        .map_err(|e| format!("Invalid broker address {}: {}", addr_str, e))?;

    TcpStream::connect_timeout(&addr, Duration::from_secs(5))
        .map_err(|e| format!("RabbitMQ unreachable at {}: {}", addr_str, e))?;

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::config::load_from;

    fn test_cfg() -> crate::config::BedsConfig {
        load_from("tests/fixtures/beds_test.toml", "")
            .expect("test fixture beds_test.toml failed to load")
    }

    #[test]
    fn validate_err_on_closed_port() {
        let mut cfg = test_cfg();
        cfg.broker_services.app_server.port = 1;
        assert!(validate(&cfg.broker_services).is_err());
    }

    #[test]
    fn validate_err_on_bad_address() {
        let mut cfg = test_cfg();
        cfg.broker_services.app_server.host = "not_a_valid_host!!!".to_string();
        assert!(validate(&cfg.broker_services).is_err());
    }
}