use std::collections::HashMap;
use std::sync::Arc;

use sqlx::PgPool;
use tokio::sync::{broadcast, mpsc, Mutex, RwLock};
use tokio::task::JoinHandle;

use crate::db;
use crate::irc::client::{ConnectOpts, IrcConnection};
use crate::irc::event::IrcEvent;
use crate::irc::parser::IrcMessage;
use crate::lua::api::{HttpApi, HttpRateLimiter, IrcApi, KvApi, LogApi, LogEntry, TimerApi, TimerEvent};
use crate::lua::dispatch::dispatch_event;
use crate::lua::sandbox::{create_sandbox, reset_instruction_counter};

struct BotHandle {
    stop_tx: mpsc::Sender<()>,
    msg_tx: mpsc::Sender<(String, String)>,
    task: JoinHandle<()>,
}

pub struct BotManager {
    bots: RwLock<HashMap<String, BotHandle>>,
    log_channels: RwLock<HashMap<String, broadcast::Sender<LogEntry>>>,
    db: PgPool,
    http_client: reqwest::Client,
}

impl BotManager {
    pub fn new(db: PgPool) -> Self {
        Self {
            bots: RwLock::new(HashMap::new()),
            log_channels: RwLock::new(HashMap::new()),
            db,
            http_client: reqwest::Client::new(),
        }
    }

    pub async fn subscribe_logs(&self, bot_id: &str) -> broadcast::Receiver<LogEntry> {
        let mut channels = self.log_channels.write().await;
        let tx = channels
            .entry(bot_id.to_string())
            .or_insert_with(|| broadcast::channel(256).0);
        tx.subscribe()
    }

    fn get_or_create_log_tx(
        channels: &mut HashMap<String, broadcast::Sender<LogEntry>>,
        bot_id: &str,
    ) -> broadcast::Sender<LogEntry> {
        channels
            .entry(bot_id.to_string())
            .or_insert_with(|| broadcast::channel(256).0)
            .clone()
    }

    pub async fn is_running(&self, bot_id: &str) -> bool {
        self.bots.read().await.contains_key(bot_id)
    }

    pub async fn start_bot(self: &Arc<Self>, bot_id: &str) -> Result<(), String> {
        {
            let bots = self.bots.read().await;
            if bots.contains_key(bot_id) {
                return Err("bot is already running".to_string());
            }
        }

        let bot = db::get_bot(&self.db, bot_id)
            .await
            .map_err(|e| format!("db error: {e}"))?
            .ok_or_else(|| "bot not found".to_string())?;

        let scripts = db::list_enabled_scripts(&self.db, bot_id)
            .await
            .map_err(|e| format!("db error: {e}"))?;

        let log_tx = {
            let mut channels = self.log_channels.write().await;
            Self::get_or_create_log_tx(&mut channels, bot_id)
        };

        let (stop_tx, mut stop_rx) = mpsc::channel::<()>(1);
        let (msg_tx, mut msg_rx) = mpsc::channel::<(String, String)>(64);

        let db = self.db.clone();
        let http_client = self.http_client.clone();
        let bot_id_owned = bot_id.to_string();

        db::set_bot_status(&self.db, bot_id, "connecting", None)
            .await
            .ok();

        let task = tokio::spawn(async move {
            let bot_id = bot_id_owned;

            let opts = ConnectOpts::from_addr(
                &bot.network_addr,
                &bot.nick,
                &bot.channels,
                bot.sasl_username.as_deref(),
                bot.sasl_password.as_deref(),
            );

            let mut backoff = 1u64;
            let mut attempt = 0u32;

            loop {
                if attempt > 0 {
                    let _ = db::set_bot_status(&db, &bot_id, "reconnecting", Some(&format!("attempt {attempt}, waiting {backoff}s"))).await;
                    let _ = crate::db::insert_log(&db, &bot_id, "info", &format!("reconnecting in {backoff}s (attempt {attempt})")).await;

                    tokio::select! {
                        _ = tokio::time::sleep(std::time::Duration::from_secs(backoff)) => {}
                        _ = stop_rx.recv() => {
                            let _ = db::set_bot_status(&db, &bot_id, "stopped", None).await;
                            return;
                        }
                    }

                    backoff = (backoff * 2).min(60);
                }

                attempt += 1;

                let mut conn = match IrcConnection::connect(&opts).await {
                    Ok(c) => {
                        backoff = 1;
                        c
                    }
                    Err(e) => {
                        tracing::error!("bot {bot_id} connect failed: {e}");
                        let _ = db::set_bot_status(&db, &bot_id, "error", Some(&e.to_string())).await;
                        continue;
                    }
                };

                if let Err(e) = conn.register(&opts).await {
                    tracing::error!("bot {bot_id} registration failed: {e}");
                    let _ = db::set_bot_status(&db, &bot_id, "error", Some(&e.to_string())).await;
                    continue;
                }

                backoff = 1;
                attempt = 0;

                let (write_tx, mut write_rx) = mpsc::channel::<IrcMessage>(256);
                let (timer_tx, mut timer_rx) = mpsc::channel::<TimerEvent>(64);

                let lua = match create_sandbox() {
                    Ok(l) => l,
                    Err(e) => {
                        tracing::error!("bot {bot_id} lua sandbox creation failed: {e}");
                        let _ = db::set_bot_status(&db, &bot_id, "error", Some(&e.to_string())).await;
                        return;
                    }
                };

                let irc_api = IrcApi { write_tx: write_tx.clone() };
                let kv_api = KvApi { db: db.clone(), bot_id: bot_id.clone() };
                let log_api = LogApi { db: db.clone(), bot_id: bot_id.clone(), log_tx: log_tx.clone() };
                let http_api = HttpApi {
                    client: http_client.clone(),
                    rate_limiter: Arc::new(Mutex::new(HttpRateLimiter::new(10))),
                };
                let timer_api = TimerApi { timer_tx: timer_tx.clone() };

                if let Err(e) = crate::lua::api::register_apis(&lua, irc_api, kv_api, log_api, http_api, timer_api) {
                    tracing::error!("bot {bot_id} api registration failed: {e}");
                    return;
                }

                for script in &scripts {
                    if let Err(e) = lua.load(&script.source).set_name(&script.name).exec() {
                        tracing::warn!("bot {bot_id} script {} load error: {e}", script.name);
                        let _ = crate::db::insert_log(&db, &bot_id, "error", &format!("script {} error: {e}", script.name)).await;
                        metrics::counter!("irc_now_bot_script_load_errors_total").increment(1);
                    }
                }

                let _ = db::set_bot_status(&db, &bot_id, "running", None).await;
                let _ = crate::db::insert_log(&db, &bot_id, "info", "connected").await;
                let entry = LogEntry {
                    bot_id: bot_id.clone(),
                    level: "info".to_string(),
                    message: "connected".to_string(),
                    timestamp: time::OffsetDateTime::now_utc().to_string(),
                };
                let _ = log_tx.send(entry);

                let (mut reader, mut writer) = conn.into_parts();

                let write_task = tokio::spawn(async move {
                    while let Some(msg) = write_rx.recv().await {
                        let data = format!("{}\r\n", msg);
                        if writer.write_all(data.as_bytes()).await.is_err() {
                            break;
                        }
                    }
                });

                const MAX_IRC_LINE: usize = 8192;
                let disconnected = loop {
                    let mut line = String::new();
                    tokio::select! {
                        result = reader.read_line(&mut line) => {
                            match result {
                                Ok(0) | Err(_) => break true,
                                Ok(_) if line.len() > MAX_IRC_LINE => {
                                    tracing::warn!("bot {bot_id} received oversize IRC line ({} bytes), disconnecting", line.len());
                                    break true;
                                }
                                Ok(_) => {
                                    if let Some(msg) = IrcMessage::parse(&line) {
                                        if msg.command == "PING" {
                                            let token = msg.params.first().map(|s| s.as_str()).unwrap_or("");
                                            let _ = write_tx.send(IrcMessage::pong(token)).await;
                                        } else if let Some(event) = IrcEvent::from_message(&msg) {
                                            if let Err(e) = dispatch_event(&lua, &event) {
                                                tracing::warn!("bot {bot_id} lua error: {e}");
                                                let _ = crate::db::insert_log(
                                                    &db, &bot_id, "error",
                                                    &format!("lua error in {}: {e}", event.handler_name()),
                                                ).await;
                                            }
                                        }
                                    }
                                    line.clear();
                                }
                            }
                        }
                        Some(timer_event) = timer_rx.recv() => {
                            let func: mlua::Function = match lua.registry_value(&timer_event.registry_key) {
                                Ok(f) => f,
                                Err(_) => continue,
                            };
                            let _ = reset_instruction_counter(&lua);
                            if let Err(e) = func.call::<()>(()) {
                                tracing::warn!("bot {bot_id} timer error: {e}");
                                let _ = crate::db::insert_log(&db, &bot_id, "error", &format!("timer error: {e}")).await;
                            }
                            if timer_event.repeating {
                                let tx = timer_tx.clone();
                                let secs = timer_event.interval_secs;
                                let key = lua.create_registry_value(func).ok();
                                if let Some(key) = key {
                                    tokio::spawn(async move {
                                        tokio::time::sleep(std::time::Duration::from_secs_f64(secs)).await;
                                        let _ = tx.send(TimerEvent {
                                            registry_key: key,
                                            repeating: true,
                                            interval_secs: secs,
                                        }).await;
                                    });
                                }
                            } else {
                                lua.remove_registry_value(timer_event.registry_key).ok();
                            }
                        }
                        Some((target, text)) = msg_rx.recv() => {
                            let _ = write_tx.send(IrcMessage::privmsg(&target, &text)).await;
                        }
                        _ = stop_rx.recv() => {
                            break false;
                        }
                    }
                };

                write_task.abort();

                if !disconnected {
                    let _ = db::set_bot_status(&db, &bot_id, "stopped", None).await;
                    let _ = crate::db::insert_log(&db, &bot_id, "info", "stopped").await;
                    return;
                }

                let _ = crate::db::insert_log(&db, &bot_id, "warn", "disconnected, will reconnect").await;
            }
        });

        {
            let mut bots = self.bots.write().await;
            bots.insert(bot_id.to_string(), BotHandle { stop_tx, msg_tx, task });
        }

        Ok(())
    }

    pub async fn send_message(&self, bot_id: &str, target: &str, text: &str) -> Result<(), String> {
        let bots = self.bots.read().await;
        let handle = bots.get(bot_id).ok_or("bot not running")?;
        handle
            .msg_tx
            .send((target.to_string(), text.to_string()))
            .await
            .map_err(|_| "send failed".to_string())
    }

    pub async fn stop_bot(&self, bot_id: &str) -> Result<(), String> {
        let handle = {
            let mut bots = self.bots.write().await;
            bots.remove(bot_id)
        };

        match handle {
            Some(h) => {
                let _ = h.stop_tx.send(()).await;
                h.task.abort();
                db::set_bot_status(&self.db, bot_id, "stopped", None)
                    .await
                    .ok();
                Ok(())
            }
            None => Err("bot is not running".to_string()),
        }
    }

    pub async fn start_all_enabled(self: Arc<Self>) {
        let bots = match db::list_enabled_bots(&self.db).await {
            Ok(b) => b,
            Err(e) => {
                tracing::error!("failed to list enabled bots: {e}");
                return;
            }
        };

        for bot in bots {
            let jitter = rand::random::<u64>() % 30_000;
            let bot_id = bot.id.clone();
            let mgr = self.clone();

            tokio::spawn(async move {
                tokio::time::sleep(std::time::Duration::from_millis(jitter)).await;
                if let Err(e) = mgr.start_bot(&bot_id).await {
                    tracing::error!("failed to auto-start bot {bot_id}: {e}");
                }
            });
        }
    }
}
