use std::path::PathBuf;
use std::sync::Arc;
use std::time::Instant;

use anyhow::Result;
use arc_swap::ArcSwap;
use chrono::Utc;
use tokio::task::JoinHandle;
use tracing::{info, warn};

use rpki::rtr::cache::{RtrCache, SharedRtrCache, Snapshot};
use rpki::rtr::config::{AppConfig, log_startup_config};
use rpki::rtr::report::{ReportConfiguration, ReportContext, current_rss_mib};
use rpki::rtr::server::{RtrNotifier, RtrService, RtrServiceStats, RunningRtrService};
use rpki::rtr::store::RtrStore;
use rpki::source::pipeline::{
    PayloadLoadConfig, SourceFingerprint, latest_sources_fingerprint,
    load_payloads_from_latest_sources_with_report,
};

#[tokio::main]
async fn main() -> Result<()> {
    let config = AppConfig::from_env()?;
    init_tracing(config.timezone);
    log_startup_config(&config);

    let report_context = ReportContext::new(ReportConfiguration::new(
        config.source_refresh_interval.as_secs(),
        config.report_interval.as_secs(),
        config.max_delta,
        config.prune_delta_by_snapshot_size,
        config.strict_ccr_validation,
        config.timezone,
        (
            config.timing.refresh,
            config.timing.retry,
            config.timing.expire,
        ),
    ));
    let store = open_store(&config)?;
    let shared_cache = init_shared_cache(&config, &store, &report_context)?;

    let service = RtrService::with_config(shared_cache.clone(), config.service_config.clone());
    let notifier = service.notifier();
    let service_stats = service.stats();

    let running = start_servers(&config, &service);
    let refresh_task = spawn_refresh_task(
        &config,
        shared_cache.clone(),
        store.clone(),
        notifier,
        service_stats,
        report_context,
    );

    wait_for_shutdown().await?;

    running.shutdown();
    running.wait().await;

    refresh_task.abort();
    let _ = refresh_task.await;

    info!("RTR service stopped");
    Ok(())
}

fn open_store(config: &AppConfig) -> Result<RtrStore> {
    info!("opening RTR store: {}", config.db_path);
    RtrStore::open(&config.db_path)
}

fn init_shared_cache(
    config: &AppConfig,
    store: &RtrStore,
    report_context: &ReportContext,
) -> Result<SharedRtrCache> {
    let payload_load_config = PayloadLoadConfig {
        ccr_dir: config.ccr_dir.clone(),
        slurm_dir: config.slurm_dir.clone(),
        strict_ccr_validation: config.strict_ccr_validation,
    };
    let source_to_delta_started = Instant::now();
    let report_context_for_loader = report_context.clone();
    let initial_cache = RtrCache::default().init(
        store,
        config.max_delta,
        config.prune_delta_by_snapshot_size,
        config.timing,
        || {
            let load = load_payloads_from_latest_sources_with_report(&payload_load_config)?;
            info!(
                "RTR source-to-delta timing: phase=startup_load_complete, ccr_dir={}, payload_count={}, elapsed_ms={}",
                payload_load_config.ccr_dir,
                load.payloads.len(),
                source_to_delta_started.elapsed().as_millis()
            );
            report_context_for_loader.record_refresh_success(
                Utc::now(),
                source_to_delta_started.elapsed().as_millis(),
                true,
                load.source,
                load.quality,
            );
            Ok(load.payloads)
        },
    )?;
    info!(
        "RTR source-to-delta timing: phase=startup_cache_init_complete, ccr_dir={}, serials={:?}, elapsed_ms={}",
        payload_load_config.ccr_dir,
        initial_cache.serials(),
        source_to_delta_started.elapsed().as_millis()
    );

    let shared_cache: SharedRtrCache = Arc::new(ArcSwap::from_pointee(initial_cache));
    let cache = shared_cache.load_full();
    info!(
        "cache initialized: session_ids={:?}, serials={:?}",
        cache.session_ids(),
        cache.serials()
    );

    Ok(shared_cache)
}

fn start_servers(config: &AppConfig, service: &RtrService) -> RunningRtrService {
    if config.enable_tls && config.enable_ssh {
        info!("starting TCP, TLS and SSH RTR servers");
        service.spawn_tcp_tls_and_ssh_from_pem_and_openssh(
            config.tcp_addr,
            config.tls_addr,
            config.ssh_addr,
            &config.tls_cert_path,
            &config.tls_key_path,
            &config.tls_client_ca_path,
            &config.ssh_host_key_path,
            &config.ssh_authorized_keys_path,
            &config.ssh_username,
            &config.ssh_subsystem_name,
            config.ssh_auth_mode,
            config.ssh_password.as_deref(),
        )
    } else if config.enable_tls {
        info!("starting TCP and TLS RTR servers");
        service.spawn_tcp_and_tls_from_pem(
            config.tcp_addr,
            config.tls_addr,
            &config.tls_cert_path,
            &config.tls_key_path,
            &config.tls_client_ca_path,
        )
    } else if config.enable_ssh {
        info!("starting TCP and SSH RTR servers");
        service.spawn_tcp_and_ssh_from_openssh(
            config.tcp_addr,
            config.ssh_addr,
            &config.ssh_host_key_path,
            &config.ssh_authorized_keys_path,
            &config.ssh_username,
            &config.ssh_subsystem_name,
            config.ssh_auth_mode,
            config.ssh_password.as_deref(),
        )
    } else {
        info!("starting TCP RTR server");
        service.spawn_tcp_only(config.tcp_addr)
    }
}

fn spawn_refresh_task(
    config: &AppConfig,
    shared_cache: SharedRtrCache,
    store: RtrStore,
    notifier: RtrNotifier,
    service_stats: RtrServiceStats,
    report_context: ReportContext,
) -> JoinHandle<()> {
    let refresh_interval = config.source_refresh_interval;
    let report_interval = config.report_interval;
    let report_dir = PathBuf::from(&config.report_dir);
    let payload_load_config = PayloadLoadConfig {
        ccr_dir: config.ccr_dir.clone(),
        slurm_dir: config.slurm_dir.clone(),
        strict_ccr_validation: config.strict_ccr_validation,
    };

    tokio::spawn(async move {
        let mut interval = tokio::time::interval(refresh_interval);
        let mut last_fingerprint: Option<SourceFingerprint> = None;
        report_context.write_or_warn(
            &report_dir,
            "startup",
            &shared_cache,
            &notifier,
            &service_stats,
        );
        let mut stats_interval = tokio::time::interval_at(
            tokio::time::Instant::now() + report_interval,
            report_interval,
        );
        stats_interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);

        loop {
            tokio::select! {
                _ = stats_interval.tick() => {
                    log_cache_memory_stats("periodic_observe", &shared_cache, &notifier);
                    report_context.write_or_warn(&report_dir, "periodic", &shared_cache, &notifier, &service_stats);
                    continue;
                }
                _ = interval.tick() => {}
            }
            let source_to_delta_started = Instant::now();
            let attempted_at = Utc::now();

            let current_fingerprint = match latest_sources_fingerprint(&payload_load_config) {
                Ok(fp) => fp,
                Err(err) => {
                    report_context.record_refresh_failure(
                        attempted_at,
                        source_to_delta_started.elapsed().as_millis(),
                        &err,
                    );
                    warn!(
                        "failed to fingerprint CCR/SLURM sources from {}: {:?} (source_to_delta_elapsed_ms={})",
                        payload_load_config.ccr_dir,
                        err,
                        source_to_delta_started.elapsed().as_millis()
                    );
                    report_context.write_or_warn(
                        &report_dir,
                        "refresh_failed",
                        &shared_cache,
                        &notifier,
                        &service_stats,
                    );
                    continue;
                }
            };

            if last_fingerprint.as_ref() == Some(&current_fingerprint) {
                report_context.record_refresh_unchanged(
                    attempted_at,
                    source_to_delta_started.elapsed().as_millis(),
                );
                info!(
                    "RTR source refresh skipped: source files unchanged (ccr_path={}, slurm_file_count={}, elapsed_ms={})",
                    current_fingerprint.ccr.path,
                    current_fingerprint.slurm_files.len(),
                    source_to_delta_started.elapsed().as_millis()
                );
                log_cache_memory_stats("refresh_skipped_unchanged", &shared_cache, &notifier);
                report_context.write_or_warn(
                    &report_dir,
                    "refresh_skipped_unchanged",
                    &shared_cache,
                    &notifier,
                    &service_stats,
                );
                continue;
            }

            match load_payloads_from_latest_sources_with_report(&payload_load_config) {
                Ok(load) => {
                    let source = load.source;
                    let quality = load.quality;
                    let payloads = load.payloads;
                    let (payload_count, updated) = {
                        let payload_count = payloads.len();
                        let source_snapshot = Snapshot::from_payloads(payloads);
                        let old_cache = shared_cache.load_full();
                        let old_serial = old_cache.serial_for_version(2);
                        let mut next_cache = old_cache.as_ref().clone();

                        let updated = match next_cache.update_with_snapshot(source_snapshot, &store)
                        {
                            Ok(()) => {
                                let new_serial = next_cache.serial_for_version(2);
                                shared_cache.store(std::sync::Arc::new(next_cache));
                                if new_serial != old_serial {
                                    info!(
                                        "RTR cache refresh applied: ccr_dir={}, payload_count={}, old_serial={}, new_serial={}",
                                        payload_load_config.ccr_dir,
                                        payload_count,
                                        old_serial,
                                        new_serial
                                    );
                                    true
                                } else {
                                    info!(
                                        "RTR cache refresh found no change: ccr_dir={}, payload_count={}, serial={}",
                                        payload_load_config.ccr_dir, payload_count, old_serial
                                    );
                                    false
                                }
                            }
                            Err(err) => {
                                report_context.record_refresh_failure(
                                    attempted_at,
                                    source_to_delta_started.elapsed().as_millis(),
                                    &err,
                                );
                                warn!("RTR cache update failed: {:?}", err);
                                report_context.write_or_warn(
                                    &report_dir,
                                    "refresh_failed",
                                    &shared_cache,
                                    &notifier,
                                    &service_stats,
                                );
                                continue;
                            }
                        };
                        (payload_count, updated)
                    };
                    report_context.record_refresh_success(
                        attempted_at,
                        source_to_delta_started.elapsed().as_millis(),
                        updated,
                        source,
                        quality,
                    );
                    info!(
                        "RTR source-to-delta timing: phase=refresh_cache_update_complete, ccr_dir={}, payload_count={}, changed={}, elapsed_ms={}",
                        payload_load_config.ccr_dir,
                        payload_count,
                        updated,
                        source_to_delta_started.elapsed().as_millis()
                    );

                    if updated {
                        let listener_count = notifier.notify_cache_updated();
                        info!(
                            "RTR cache updated, notify signal emitted to session listeners: listener_count={}",
                            listener_count
                        );
                    }
                    log_cache_memory_stats("refresh_complete", &shared_cache, &notifier);
                    report_context.write_or_warn(
                        &report_dir,
                        "refresh_complete",
                        &shared_cache,
                        &notifier,
                        &service_stats,
                    );
                    last_fingerprint = Some(current_fingerprint);
                }
                Err(err) => {
                    report_context.record_refresh_failure(
                        attempted_at,
                        source_to_delta_started.elapsed().as_millis(),
                        &err,
                    );
                    warn!(
                        "failed to reload CCR/SLURM payloads from {}: {:?} (source_to_delta_elapsed_ms={})",
                        payload_load_config.ccr_dir,
                        err,
                        source_to_delta_started.elapsed().as_millis()
                    );
                    report_context.write_or_warn(
                        &report_dir,
                        "refresh_failed",
                        &shared_cache,
                        &notifier,
                        &service_stats,
                    );
                }
            }
        }
    })
}

fn log_cache_memory_stats(phase: &str, shared_cache: &SharedRtrCache, notifier: &RtrNotifier) {
    let cache = shared_cache.load_full();
    let stats = cache.memory_stats();
    let rss_mib = current_rss_mib();

    info!(
        "RTR memory observe: phase={}, listener_count={}, serials={:?}, snapshot_payload_counts={:?}, delta_lengths={:?}, delta_payload_counts={:?}, snapshot_arc_strong_counts={:?}, rtr_payloads_arc_strong_counts={:?}, rss_mib={:?}",
        phase,
        notifier.listener_count(),
        stats.serials,
        stats.snapshot_payload_counts,
        stats.delta_lengths,
        stats.delta_payload_counts,
        stats.snapshot_arc_strong_counts,
        stats.rtr_payloads_arc_strong_counts,
        rss_mib
    );
}

async fn wait_for_shutdown() -> Result<()> {
    tokio::signal::ctrl_c().await?;
    info!("shutdown signal received");
    Ok(())
}

fn init_tracing(timezone: chrono_tz::Tz) {
    let filter = tracing_subscriber::EnvFilter::try_from_default_env()
        .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("warn"));

    struct LocalTimer {
        timezone: chrono_tz::Tz,
    }

    impl tracing_subscriber::fmt::time::FormatTime for LocalTimer {
        fn format_time(
            &self,
            w: &mut tracing_subscriber::fmt::format::Writer<'_>,
        ) -> std::fmt::Result {
            let now = Utc::now().with_timezone(&self.timezone);
            write!(w, "{}", now.format("%Y-%m-%d %H:%M:%S%.3f %:z"))
        }
    }

    if let Err(err) = tracing_subscriber::fmt()
        .with_timer(LocalTimer { timezone })
        .with_env_filter(filter)
        .with_target(true)
        .with_thread_ids(true)
        .with_level(true)
        .try_init()
    {
        eprintln!("failed to initialize tracing subscriber: {err}");
    }
}