//! Copyright (c) 2022-2026 GitDataAi All rights reserved.

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

use gitks::disk_cache::DiskCache;
use gitks::hooks::HookManager;
use gitks::metrics;
use gitks::server::{GitksService, serve_with_shutdown};

use etcd_client::{Client, PutOptions};
use tokio::sync::Mutex;

use tracing_subscriber::EnvFilter;
use tracing_subscriber::fmt;
use tracing_subscriber::prelude::*;

const DEFAULT_HOST: &str = "0.0.0.0";
const DEFAULT_PORT: &str = "50051";
const DEFAULT_STORAGE_NAME: &str = "default";

/// etcd-backed config reader. Priority: etcd > env > default.
struct EtcdConfig {
    client: Arc<Mutex<Client>>,
    prefix: String,
}

impl EtcdConfig {
    async fn connect(endpoints: Vec<String>, prefix: &str) -> Result<Self, String> {
        let client = Client::connect(endpoints, None)
            .await
            .map_err(|e| format!("etcd connect: {e}"))?;
        Ok(Self {
            client: Arc::new(Mutex::new(client)),
            prefix: prefix.to_string(),
        })
    }

    /// Get config: etcd first, env second, default last.
    async fn get(&self, key: &str, default: &str) -> String {
        let etcd_key = format!("{}config/{}", self.prefix, key);
        if let Ok(mut c) = self.client.try_lock()
            && let Ok(resp) = c.get(etcd_key.as_str(), None).await
            && let Some(kv) = resp.kvs().first()
            && let Ok(v) = kv.value_str()
            && !v.is_empty()
        {
            return v.to_string();
        }
        std::env::var(key).unwrap_or_else(|_| default.to_string())
    }

    /// Register this service under the common prefix for discovery by other services.
    async fn register(&self, service_name: &str, addr: &str) -> Result<(), String> {
        let instance_id = uuid::Uuid::now_v7().to_string();
        let addr = addr.to_string();
        let key = format!("{}services/{}/{}", self.prefix, service_name, instance_id);
        let instance =
            serde_json::json!({"addr": &addr, "port": 0, "version": env!("CARGO_PKG_VERSION")});
        let value = serde_json::to_string(&instance).map_err(|e| format!("json: {e}"))?;

        let lease = {
            let mut c = self.client.lock().await;
            c.lease_grant(15, None)
                .await
                .map_err(|e| format!("lease: {e}"))?
        };
        {
            let mut c = self.client.lock().await;
            let opts = PutOptions::new().with_lease(lease.id());
            c.put(key.clone(), value, Some(opts))
                .await
                .map_err(|e| format!("put: {e}"))?;
        }
        tracing::info!(service = service_name, addr = %addr, "registered in etcd");

        let c = self.client.clone();
        tokio::spawn(async move {
            loop {
                let r = {
                    let mut cl = c.lock().await;
                    cl.lease_keep_alive(lease.id()).await
                };
                drop(r);
                tokio::time::sleep(std::time::Duration::from_secs(5)).await;
                if let Ok(lr) = {
                    let mut cl = c.lock().await;
                    cl.lease_grant(15, None).await
                } {
                    let inst = serde_json::json!({"addr": &addr, "port": 0, "version": env!("CARGO_PKG_VERSION")});
                    if let Ok(v) = serde_json::to_string(&inst) {
                        let mut cl = c.lock().await;
                        let _ = cl
                            .put(key.clone(), v, Some(PutOptions::new().with_lease(lr.id())))
                            .await;
                    }
                }
            }
        });
        Ok(())
    }
}

fn env_or(key: &str, default: &str) -> String {
    std::env::var(key).unwrap_or_else(|_| default.into())
}

fn env_bool(key: &str, default: bool) -> bool {
    match std::env::var(key).as_deref() {
        Ok("true" | "1" | "yes") => true,
        Ok("false" | "0" | "no") => false,
        _ => default,
    }
}

fn env_u64(key: &str, default: u64) -> u64 {
    std::env::var(key)
        .ok()
        .and_then(|v| v.parse().ok())
        .unwrap_or(default)
}

fn init_tracing() -> Option<tracing_appender::non_blocking::WorkerGuard> {
    let env_filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info"));

    let log_format = env_or("GITKS_LOG_FORMAT", "pretty");

    let fmt_layer = match log_format.as_str() {
        "json" => fmt::layer()
            .json()
            .with_target(true)
            .with_file(true)
            .with_line_number(true)
            .with_thread_ids(true)
            .with_span_events(fmt::format::FmtSpan::NEW | fmt::format::FmtSpan::CLOSE)
            .boxed(),
        _ => fmt::layer()
            .pretty()
            .with_target(true)
            .with_file(true)
            .with_line_number(true)
            .boxed(),
    };

    if let Ok(log_dir) = std::env::var("GITKS_LOG_DIR") {
        let rotation = match env_or("GITKS_LOG_ROTATION", "daily").as_str() {
            "hourly" => tracing_appender::rolling::Rotation::HOURLY,
            "never" => tracing_appender::rolling::Rotation::NEVER,
            _ => tracing_appender::rolling::Rotation::DAILY,
        };
        let retention = env_u64("GITKS_LOG_RETENTION", 7) as usize;

        let mut builder = tracing_appender::rolling::Builder::new()
            .rotation(rotation)
            .filename_prefix("gitks")
            .filename_suffix("log");

        if retention > 0 {
            builder = builder.max_log_files(retention);
        }

        let file_appender = match builder.build(&log_dir) {
            Ok(file_appender) => file_appender,
            Err(err) => {
                eprintln!("failed to create log directory '{log_dir}': {err}");
                tracing_subscriber::registry()
                    .with(env_filter)
                    .with(fmt_layer)
                    .init();
                return None;
            }
        };
        let (non_blocking, guard) = tracing_appender::non_blocking(file_appender);

        let file_layer = fmt::layer()
            .json()
            .with_target(true)
            .with_file(true)
            .with_line_number(true)
            .with_writer(non_blocking)
            .with_filter(EnvFilter::new("info"))
            .boxed();

        tracing_subscriber::registry()
            .with(env_filter)
            .with(fmt_layer)
            .with(file_layer)
            .init();

        Some(guard)
    } else {
        tracing_subscriber::registry()
            .with(env_filter)
            .with(fmt_layer)
            .init();
        None
    }
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    dotenvy::dotenv().ok();
    let _log_guard = init_tracing();

    tracing::info!(
        version = env!("CARGO_PKG_VERSION"),
        log_format = %env_or("GITKS_LOG_FORMAT", "pretty"),
        "gitks starting up"
    );

    let host = env_or("GITKS_HOST", DEFAULT_HOST);
    let port = env_or("GITKS_PORT", DEFAULT_PORT);
    let storage_name = env_or("STORAGE_NAME", DEFAULT_STORAGE_NAME);

    let etcd_endpoints: Vec<String> = std::env::var("GITKS_ETCD_ENDPOINTS")
        .ok()
        .filter(|s| !s.is_empty())
        .map(|s| s.split(',').map(str::trim).map(String::from).collect())
        .unwrap_or_else(|| vec!["http://localhost:2379".to_string()]);
    let etcd_prefix = std::env::var("ETCD_KEY_PREFIX").unwrap_or_else(|_| "/appks/".to_string());

    let etcd = EtcdConfig::connect(etcd_endpoints, &etcd_prefix).await.ok();
    let host = if let Some(ref e) = etcd {
        e.get("GITKS_HOST", &host).await
    } else {
        host
    };
    let port = if let Some(ref e) = etcd {
        e.get("GITKS_PORT", &port).await
    } else {
        port
    };
    let storage_name = if let Some(ref e) = etcd {
        e.get("GITKS_STORAGE_NAME", &storage_name).await
    } else {
        storage_name
    };
    let grpc_addr =
        std::env::var("GITKS_ADVERTISE_ADDR").unwrap_or_else(|_| format!("http://{host}:{port}"));

    if let Some(ref e) = etcd {
        let addr_str = format!("{host}:{port}");
        e.register("gitks", &addr_str).await.ok();
    }

    let repo_prefix = std::env::var("REPO_PREFIX_PATH")
        .map_err(|_| "REPO_PREFIX_PATH environment variable is required (e.g. /data/repos)")?;
    let repo_prefix = PathBuf::from(&repo_prefix);
    if !repo_prefix.is_absolute() {
        return Err("REPO_PREFIX_PATH must be an absolute path".into());
    }
    if !repo_prefix.exists() {
        tracing::info!(path = %repo_prefix.display(), "creating repo prefix directory");
        std::fs::create_dir_all(&repo_prefix)?;
    }

    let disk_cache_enabled = env_bool("GITKS_DISK_CACHE_ENABLED", false);
    let disk_cache_max_age = env_u64("GITKS_DISK_CACHE_MAX_AGE", 300);

    let disk_cache = DiskCache::new(
        repo_prefix.clone(),
        env!("CARGO_PKG_VERSION").to_string(),
        disk_cache_max_age,
        disk_cache_enabled,
    );

    if disk_cache_enabled {
        tracing::info!(max_age_secs = disk_cache_max_age, "disk cache enabled");
        disk_cache.cleanup_on_startup()?;
        gitks::disk_cache::start_cache_cleanup_task(disk_cache.clone(), Duration::from_secs(300));
    } else {
        tracing::info!("disk cache disabled");
    }

    let pack_cache_enabled = env_bool("GITKS_PACK_CACHE_ENABLED", false);
    let pack_backpressure = env_bool("GITKS_PACK_CACHE_BACKPRESSURE", true);

    let pack_cache = if disk_cache_enabled {
        tracing::info!(
            pack_objects_cache = pack_cache_enabled,
            backpressure = pack_backpressure,
            "pack cache wrapper enabled"
        );
        Some(gitks::pack_cache::PackCache::new(
            disk_cache.clone(),
            pack_backpressure,
        ))
    } else {
        None
    };

    let hooks_enabled = env_bool("GITKS_HOOKS_ENABLED", true);
    let server_hooks_dir = std::env::var("GITKS_SERVER_HOOKS_DIR")
        .ok()
        .map(PathBuf::from);
    let hook_callback_addr = std::env::var("GITKS_HOOK_CALLBACK_ADDR").ok();
    let hook_timeout = env_u64("GITKS_HOOK_TIMEOUT", 30);
    let allow_custom_hooks = env_bool("GITKS_ALLOW_CUSTOM_HOOKS", true);

    let hook_manager = if hooks_enabled {
        tracing::info!(
            timeout_secs = hook_timeout,
            custom_hooks = allow_custom_hooks,
            "hooks enabled"
        );
        Some(HookManager::new(
            repo_prefix.clone(),
            server_hooks_dir,
            hook_callback_addr,
            Duration::from_secs(hook_timeout),
            allow_custom_hooks,
        ))
    } else {
        tracing::info!("hooks disabled");
        None
    };

    let metrics_port = env_u64("GITKS_METRICS_PORT", 9100) as u16;
    let http_cancel = tokio_util::sync::CancellationToken::new();
    metrics::set_http_cancel_token(http_cancel.clone());
    let _metrics_handle = metrics::start_metrics_server(metrics_port);
    tracing::info!(port = metrics_port, "metrics server started");

    let _semaphore_cleanup = gitks::rate_limit::start_semaphore_cleanup_task();

    let slow_request_threshold = env_u64("GITKS_SLOW_REQUEST_THRESHOLD_MS", 5000);
    metrics::set_slow_request_threshold(slow_request_threshold);
    tracing::info!(
        threshold_ms = slow_request_threshold,
        "slow request detection configured"
    );

    let addr: std::net::SocketAddr = format!("{host}:{port}").parse()?;
    let mut svc = GitksService::new(repo_prefix.clone());

    if disk_cache_enabled {
        svc = svc.with_disk_cache(disk_cache);
    }
    if let Some(pc) = pack_cache {
        svc = svc.with_pack_cache(pc);
    }
    if let Some(hm) = hook_manager {
        svc = svc.with_hook_manager(hm);
    }

    let svc = svc.with_grpc_addr(grpc_addr.clone());

    tracing::info!(
        addr = %addr,
        repo_prefix = %repo_prefix.display(),
        storage = %storage_name,
        advertise = %grpc_addr,
        "starting gitks gRPC server"
    );

    metrics::set_ready(true);

    serve_with_shutdown(addr, svc, shutdown_signal()).await?;

    metrics::set_ready(false);

    http_cancel.cancel();

    tracing::info!("gitks shut down complete");
    Ok(())
}

/// Resolves when the process receives SIGTERM or SIGINT (Ctrl+C).
async fn shutdown_signal() {
    let ctrl_c = async {
        tokio::signal::ctrl_c()
            .await
            .expect("failed to install Ctrl+C handler");
    };

    #[cfg(unix)]
    let terminate = async {
        tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate())
            .expect("failed to install SIGTERM handler")
            .recv()
            .await;
    };

    #[cfg(not(unix))]
    let terminate = std::future::pending::<()>();

    tokio::select! {
        _ = ctrl_c => {
            tracing::info!("received Ctrl+C, starting graceful shutdown");
        }
        _ = terminate => {
            tracing::info!("received SIGTERM, starting graceful shutdown");
        }
    }
}