/// Prometheus-exporter - a Rust binary crate to provide functional 
/// of the metrics Exporter.
/// 
/// It handles metrics list in it's own local `Registry`

mod endpoints;
mod metrics;
mod structs;

use axum::{
    routing::{get, post}, 
    Router};
use prometheus::Registry;
use std::{str::FromStr, sync::{Arc, Mutex}};
use endpoints::*;
use tokio::net::TcpListener;
use tracing::info;
use dotenv::dotenv;

/// Shared state of the Web-server 
/// 
/// Used to store and share state of the metrics `Registry`
/// 
struct AppState {
    registry: Mutex<Registry>,
}

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    dotenv().ok();

    let log_level = std::env::var("PROMETHEUS_EXPORTER_LOG_LEVEL")
    .unwrap_or_else(|_| "INFO".to_owned());
    
    tracing_subscriber::fmt()
    .with_max_level(tracing::Level::from_str(&log_level).unwrap_or_else(|_| tracing::Level::INFO))
    .with_writer(std::io::stdout)
    .with_span_events(tracing_subscriber::fmt::format::FmtSpan::NEW)
    .with_line_number(false)
    .with_target(false)
    .with_file(false)
    .compact()
    .init();
    info!("Logger was created and configurated, dotenv vars were loaded (if exist)");

    info!("Initializing local Prometehus metrics registry ...");
    let registry = Registry::new();

    info!("Initializing shared state for Prometheus Exporter web-server ...");
    let state = Arc::new(AppState {
        registry: Mutex::new(registry),
    });


    info!("Configurating internals of Prometheus Exporter web-server...");
    let app = Router::new()
        .route("/metrics", get(metrics_handler))
        .route("/update", post(update_metrics))
        .with_state(state.clone());

    let port = std::env::var("PROMETHEUS_EXPORTER_PORT")
    .unwrap_or_else(|_| "9100".to_owned());
    let bind_address = format!("0.0.0.0:{}", &port);
    let listener = TcpListener::bind(bind_address).await?;
    
    info!("Serving on ...:{}", &port);
    axum::serve(listener, app).await?;
    Ok(())
}