mod app;
mod config;
mod data;
mod ui;

use std::fs;
use std::io::{self, Stdout};
use std::path::{Path, PathBuf};
use std::sync::{
    atomic::{AtomicBool, Ordering},
    Arc, OnceLock,
};
use std::time::Duration;

use crate::data::metrics::{BackupMetrics, ServiceMetrics, SmartMetrics};
use anyhow::{anyhow, Context, Result};
use chrono::{TimeZone, Utc};
use clap::{ArgAction, Parser, Subcommand};
use cm_dashboard_shared::envelope::{AgentType, MetricsEnvelope};
use crossterm::event::{self, Event};
use crossterm::terminal::{disable_raw_mode, enable_raw_mode};
use crossterm::{execute, terminal};
use ratatui::backend::CrosstermBackend;
use ratatui::Terminal;
use serde_json::Value;
use tokio::sync::mpsc::{
    error::TryRecvError, unbounded_channel, UnboundedReceiver, UnboundedSender,
};
use tokio::task::{spawn_blocking, JoinHandle};
use tracing::{debug, warn};
use tracing_appender::non_blocking::WorkerGuard;
use tracing_subscriber::EnvFilter;
use zmq::{Context as NativeZmqContext, Message as NativeZmqMessage};

use crate::app::{App, AppEvent, AppOptions, ZmqContext};

static LOG_GUARD: OnceLock<WorkerGuard> = OnceLock::new();

#[derive(Parser, Debug)]
#[command(
    name = "cm-dashboard",
    version,
    about = "Infrastructure monitoring TUI for CMTEC"
)]
struct Cli {
    #[command(subcommand)]
    command: Option<Command>,
    /// Optional path to configuration TOML file
    #[arg(long, value_name = "FILE")]
    config: Option<PathBuf>,

    /// Limit dashboard to a single host
    #[arg(short = 'H', long, value_name = "HOST")]
    host: Option<String>,

    /// Interval (ms) to refresh dashboard when idle
    #[arg(long, default_value_t = 250)]
    tick_rate: u64,

    /// Increase logging verbosity (-v, -vv)
    #[arg(short, long, action = ArgAction::Count)]
    verbose: u8,

    /// Override ZMQ endpoints (comma-separated)
    #[arg(long, value_delimiter = ',', value_name = "ENDPOINT")]
    zmq_endpoint: Vec<String>,
}

#[derive(Subcommand, Debug)]
enum Command {
    /// Generate default configuration files
    InitConfig {
        #[arg(long, value_name = "DIR", default_value = "config")]
        dir: PathBuf,
        /// Overwrite existing files if they already exist
        #[arg(long, action = ArgAction::SetTrue)]
        force: bool,
    },
}

#[tokio::main]
async fn main() -> Result<()> {
    let cli = Cli::parse();

    if let Some(Command::InitConfig { dir, force }) = cli.command.as_ref() {
        init_tracing(cli.verbose)?;
        generate_config_templates(dir, *force)?;
        return Ok(());
    }

    ensure_default_config(&cli)?;

    let options = AppOptions {
        config: cli.config,
        host: cli.host,
        tick_rate: Duration::from_millis(cli.tick_rate.max(16)),
        verbosity: cli.verbose,
        zmq_endpoints_override: cli.zmq_endpoint,
    };

    init_tracing(options.verbosity)?;

    let mut app = App::new(options)?;
    let (event_tx, mut event_rx) = unbounded_channel();

    let shutdown_flag = Arc::new(AtomicBool::new(false));

    let zmq_task = if let Some(context) = app.zmq_context() {
        Some(spawn_metrics_task(
            context,
            event_tx.clone(),
            shutdown_flag.clone(),
        ))
    } else {
        None
    };

    let mut terminal = setup_terminal()?;
    let result = run_app(&mut terminal, &mut app, &mut event_rx);
    teardown_terminal(terminal)?;
    shutdown_flag.store(true, Ordering::Relaxed);
    let _ = event_tx.send(AppEvent::Shutdown);
    if let Some(handle) = zmq_task {
        if let Err(join_error) = handle.await {
            warn!(%join_error, "ZMQ metrics task ended unexpectedly");
        }
    }
    result
}

fn setup_terminal() -> Result<Terminal<CrosstermBackend<Stdout>>> {
    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, terminal::EnterAlternateScreen)?;
    let backend = CrosstermBackend::new(stdout);
    let terminal = Terminal::new(backend)?;
    Ok(terminal)
}

fn teardown_terminal(mut terminal: Terminal<CrosstermBackend<Stdout>>) -> Result<()> {
    disable_raw_mode()?;
    execute!(terminal.backend_mut(), terminal::LeaveAlternateScreen)?;
    terminal.show_cursor()?;
    Ok(())
}

fn run_app(
    terminal: &mut Terminal<CrosstermBackend<Stdout>>,
    app: &mut App,
    event_rx: &mut UnboundedReceiver<AppEvent>,
) -> Result<()> {
    let tick_rate = app.tick_rate();

    while !app.should_quit() {
        drain_app_events(app, event_rx);
        terminal.draw(|frame| ui::render(frame, app))?;

        if event::poll(tick_rate)? {
            if let Event::Key(key) = event::read()? {
                app.handle_key_event(key);
            }
        } else {
            app.on_tick();
        }
    }

    Ok(())
}

fn drain_app_events(app: &mut App, receiver: &mut UnboundedReceiver<AppEvent>) {
    loop {
        match receiver.try_recv() {
            Ok(event) => app.handle_app_event(event),
            Err(TryRecvError::Empty) => break,
            Err(TryRecvError::Disconnected) => break,
        }
    }
}

fn init_tracing(verbosity: u8) -> Result<()> {
    let level = match verbosity {
        0 => "warn",
        1 => "info",
        2 => "debug",
        _ => "trace",
    };

    let env_filter = std::env::var("RUST_LOG")
        .ok()
        .and_then(|value| EnvFilter::try_new(value).ok())
        .unwrap_or_else(|| EnvFilter::new(level));

    let writer = prepare_log_writer()?;

    tracing_subscriber::fmt()
        .with_env_filter(env_filter)
        .with_target(false)
        .with_ansi(false)
        .with_writer(writer)
        .compact()
        .try_init()
        .map_err(|err| anyhow!(err))?;

    Ok(())
}

fn prepare_log_writer() -> Result<tracing_appender::non_blocking::NonBlocking> {
    let logs_dir = Path::new("logs");
    if !logs_dir.exists() {
        fs::create_dir_all(logs_dir).with_context(|| {
            format!("failed to create logs directory at {}", logs_dir.display())
        })?;
    }

    let file_appender = tracing_appender::rolling::never(logs_dir, "cm-dashboard.log");
    let (non_blocking, guard) = tracing_appender::non_blocking(file_appender);
    LOG_GUARD.get_or_init(|| guard);
    Ok(non_blocking)
}

fn spawn_metrics_task(
    context: ZmqContext,
    sender: UnboundedSender<AppEvent>,
    shutdown: Arc<AtomicBool>,
) -> JoinHandle<()> {
    tokio::spawn(async move {
        match spawn_blocking(move || metrics_blocking_loop(context, sender, shutdown)).await {
            Ok(Ok(())) => {}
            Ok(Err(error)) => warn!(%error, "ZMQ metrics worker exited with error"),
            Err(join_error) => warn!(%join_error, "ZMQ metrics worker panicked"),
        }
    })
}

fn metrics_blocking_loop(
    context: ZmqContext,
    sender: UnboundedSender<AppEvent>,
    shutdown: Arc<AtomicBool>,
) -> Result<()> {
    let zmq_context = NativeZmqContext::new();
    let socket = zmq_context
        .socket(zmq::SUB)
        .context("failed to create ZMQ SUB socket")?;

    socket
        .set_linger(0)
        .context("failed to configure ZMQ linger")?;
    socket
        .set_rcvtimeo(1_000)
        .context("failed to configure ZMQ receive timeout")?;

    for endpoint in context.endpoints() {
        debug!(%endpoint, "connecting to ZMQ endpoint");
        socket
            .connect(endpoint)
            .with_context(|| format!("failed to connect to {endpoint}"))?;
    }

    if let Some(prefix) = context.subscription() {
        socket
            .set_subscribe(prefix.as_bytes())
            .context("failed to set ZMQ subscription")?;
    } else {
        socket
            .set_subscribe(b"")
            .context("failed to subscribe to all ZMQ topics")?;
    }

    while !shutdown.load(Ordering::Relaxed) {
        match socket.recv_msg(0) {
            Ok(message) => {
                if let Err(error) = handle_zmq_message(&message, &sender) {
                    warn!(%error, "failed to handle ZMQ message");
                }
            }
            Err(error) => {
                if error == zmq::Error::EAGAIN {
                    continue;
                }
                warn!(%error, "ZMQ receive error");
                std::thread::sleep(Duration::from_millis(250));
            }
        }
    }

    debug!("ZMQ metrics worker shutting down");

    Ok(())
}

fn handle_zmq_message(
    message: &NativeZmqMessage,
    sender: &UnboundedSender<AppEvent>,
) -> Result<()> {
    let bytes = message.to_vec();

    let envelope: MetricsEnvelope =
        serde_json::from_slice(&bytes).with_context(|| "failed to deserialize metrics envelope")?;
    let timestamp = Utc
        .timestamp_opt(envelope.timestamp as i64, 0)
        .single()
        .unwrap_or_else(|| Utc::now());

    let host = envelope.hostname.clone();

    let mut payload = envelope.metrics;
    if let Some(obj) = payload.as_object_mut() {
        obj.entry("timestamp")
            .or_insert_with(|| Value::String(timestamp.to_rfc3339()));
    }

    match envelope.agent_type {
        AgentType::Smart => match serde_json::from_value::<SmartMetrics>(payload.clone()) {
            Ok(metrics) => {
                let _ = sender.send(AppEvent::MetricsUpdated {
                    host,
                    smart: Some(metrics),
                    services: None,
                    backup: None,
                    timestamp,
                });
            }
            Err(error) => {
                warn!(%error, "failed to parse smart metrics");
                let _ = sender.send(AppEvent::MetricsFailed {
                    host,
                    error: format!("smart metrics parse error: {error:#}"),
                    timestamp,
                });
            }
        },
        AgentType::Service => match serde_json::from_value::<ServiceMetrics>(payload.clone()) {
            Ok(metrics) => {
                let _ = sender.send(AppEvent::MetricsUpdated {
                    host,
                    smart: None,
                    services: Some(metrics),
                    backup: None,
                    timestamp,
                });
            }
            Err(error) => {
                warn!(%error, "failed to parse service metrics");
                let _ = sender.send(AppEvent::MetricsFailed {
                    host,
                    error: format!("service metrics parse error: {error:#}"),
                    timestamp,
                });
            }
        },
        AgentType::Backup => match serde_json::from_value::<BackupMetrics>(payload.clone()) {
            Ok(metrics) => {
                let _ = sender.send(AppEvent::MetricsUpdated {
                    host,
                    smart: None,
                    services: None,
                    backup: Some(metrics),
                    timestamp,
                });
            }
            Err(error) => {
                warn!(%error, "failed to parse backup metrics");
                let _ = sender.send(AppEvent::MetricsFailed {
                    host,
                    error: format!("backup metrics parse error: {error:#}"),
                    timestamp,
                });
            }
        },
    }

    Ok(())
}

fn ensure_default_config(cli: &Cli) -> Result<()> {
    if let Some(path) = cli.config.as_ref() {
        ensure_config_at(path, false)?;
    } else {
        let default_path = Path::new("config/dashboard.toml");
        if !default_path.exists() {
            generate_config_templates(Path::new("config"), false)?;
            println!("Created default configuration in ./config");
        }
    }

    Ok(())
}

fn ensure_config_at(path: &Path, force: bool) -> Result<()> {
    if path.exists() && !force {
        return Ok(());
    }

    if let Some(parent) = path.parent() {
        if !parent.exists() {
            fs::create_dir_all(parent)
                .with_context(|| format!("failed to create directory {}", parent.display()))?;
        }

        write_template(path.to_path_buf(), DASHBOARD_TEMPLATE, force, "dashboard")?;

        let hosts_path = parent.join("hosts.toml");
        if !hosts_path.exists() || force {
            write_template(hosts_path, HOSTS_TEMPLATE, force, "hosts")?;
        }
        println!(
            "Created configuration templates in {} (dashboard: {})",
            parent.display(),
            path.display()
        );
    } else {
        return Err(anyhow!("invalid configuration path {}", path.display()));
    }

    Ok(())
}

fn generate_config_templates(target_dir: &Path, force: bool) -> Result<()> {
    if !target_dir.exists() {
        fs::create_dir_all(target_dir)
            .with_context(|| format!("failed to create directory {}", target_dir.display()))?;
    }

    write_template(
        target_dir.join("dashboard.toml"),
        DASHBOARD_TEMPLATE,
        force,
        "dashboard",
    )?;
    write_template(
        target_dir.join("hosts.toml"),
        HOSTS_TEMPLATE,
        force,
        "hosts",
    )?;

    println!(
        "Configuration templates written to {}",
        target_dir.display()
    );

    Ok(())
}

fn write_template(path: PathBuf, contents: &str, force: bool, name: &str) -> Result<()> {
    if path.exists() && !force {
        return Err(anyhow!(
            "{} template already exists at {} (use --force to overwrite)",
            name,
            path.display()
        ));
    }

    fs::write(&path, contents)
        .with_context(|| format!("failed to write {} template to {}", name, path.display()))?;

    Ok(())
}

const DASHBOARD_TEMPLATE: &str = r#"# CM Dashboard configuration

[hosts]
# default_host = "srv01"

[[hosts.hosts]]
name = "srv01"
enabled = true
# metadata = { rack = "R1" }

[[hosts.hosts]]
name = "labbox"
enabled = true

[dashboard]
tick_rate_ms = 250
history_duration_minutes = 60

[[dashboard.widgets]]
id = "storage"
enabled = true

[[dashboard.widgets]]
id = "services"
enabled = true

[[dashboard.widgets]]
id = "backup"
enabled = true

[[dashboard.widgets]]
id = "alerts"
enabled = true

[filesystem]
# cache_dir = "/var/lib/cm-dashboard/cache"
# history_dir = "/var/lib/cm-dashboard/history"
"#;

const HOSTS_TEMPLATE: &str = r#"# Optional separate hosts configuration

[hosts]
# default_host = "srv01"

[[hosts.hosts]]
name = "srv01"
enabled = true

[[hosts.hosts]]
name = "labbox"
enabled = true
"#;