//! Bot behavior: the [`Bot`] state, registration, and the event loop.
//!
//! Behaviour is split across sibling modules: capability negotiation and SASL
//! live in [`caps`], and message routing in [`commands`]. Features live behind
//! the [`Module`] plugin trait ([`module`]) and are registered in [`modules`],
//! so adding a command is a new file in `bot/modules/` plus one line in
//! [`modules::all`] — no changes to the core dispatch.

use std::collections::{HashMap, HashSet};
use std::io;

use crate::config::Config;
use crate::irc::{Connection, Message};

mod caps;
mod commands;
pub mod module;
pub mod modules;

pub use module::{Action, Command, CommandSpec, Module};

/// The bot: owns its configuration, connection, and feature modules, and runs
/// one session.
pub struct Bot {
    config: Config,
    conn: Connection,
    /// The nick we are currently trying to use (may drift from `config.nick`
    /// if the server reports a collision).
    current_nick: String,
    registered: bool,
    /// Capabilities the server advertised in `CAP LS`.
    available_caps: HashSet<String>,
    /// Capabilities we successfully negotiated (`CAP ACK`).
    enabled_caps: HashSet<String>,
    /// Open IRCv3 batches: reference -> batch type (e.g. `chathistory`).
    batches: HashMap<String, String>,
    /// Whether the SASL exchange has begun this session.
    sasl_started: bool,
    /// Registered feature modules (a fresh set per network/session).
    modules: Vec<Box<dyn Module>>,
    /// Command word -> index into `modules`, built from each module's specs.
    routes: HashMap<&'static str, usize>,
}

impl Bot {
    pub fn new(config: Config, conn: Connection) -> Bot {
        let current_nick = config.nick.clone();

        // Build the module set and the command -> module route table.
        let mods = modules::all();
        let mut routes: HashMap<&'static str, usize> = HashMap::new();
        for (i, m) in mods.iter().enumerate() {
            for spec in m.commands() {
                if routes.insert(spec.name, i).is_some() {
                    crate::log(&format!(
                        "module '{}' overrides command '{}'",
                        m.name(),
                        spec.name
                    ));
                }
            }
        }

        Bot {
            config,
            conn,
            current_nick,
            registered: false,
            available_caps: HashSet::new(),
            enabled_caps: HashSet::new(),
            batches: HashMap::new(),
            sasl_started: false,
            modules: mods,
            routes,
        }
    }

    /// Register with the server, then process messages until disconnect.
    ///
    /// Returns `Ok(())` when the server closes the connection cleanly; the
    /// caller (the supervisor) decides whether to reconnect.
    pub fn run(&mut self) -> io::Result<()> {
        self.register()?;
        while let Some(msg) = self.conn.read_message()? {
            self.handle(&msg)?;
        }
        Ok(())
    }

    /// Begin registration: open IRCv3 capability negotiation, then send
    /// NICK/USER. The server withholds `001` until we send `CAP END`, which
    /// happens once caps (and optional SASL) are settled — see [`Bot::handle`].
    fn register(&mut self) -> io::Result<()> {
        if let Some(password) = self.config.password.clone() {
            self.conn.pass(&password)?;
        }
        self.conn.cap_ls()?;
        let nick = self.current_nick.clone();
        self.conn.nick(&nick)?;
        let (user, realname) = (self.config.user.clone(), self.config.realname.clone());
        self.conn.user(&user, &realname)?;
        Ok(())
    }

    /// Dispatch a single incoming message.
    fn handle(&mut self, msg: &Message) -> io::Result<()> {
        match msg.command.as_str() {
            // Keep-alive: reply immediately or the server will time us out.
            "PING" => {
                let token = msg.trailing().unwrap_or("").to_string();
                self.conn.pong(&token)?;
            }
            // IRCv3 capability negotiation and SASL (see `caps`).
            "CAP" => self.handle_cap(msg)?,
            "AUTHENTICATE" => self.handle_authenticate(msg)?,
            "903" => self.conn.cap_end()?, // RPL_SASLSUCCESS
            // SASL failed/aborted/locked/too-long/already-authed — proceed anyway.
            "902" | "904" | "905" | "906" | "907" => self.conn.cap_end()?,
            // Track open/closed batches so we can recognise replayed history.
            "BATCH" => self.handle_batch(msg),
            // RPL_WELCOME: registration succeeded — now it's safe to join.
            "001" => {
                self.registered = true;
                for channel in self.config.channels.clone() {
                    self.conn.join(&channel)?;
                }
            }
            // ERR_NICKNAMEINUSE: append an underscore and try again.
            "433" => {
                self.current_nick.push('_');
                let nick = self.current_nick.clone();
                self.conn.nick(&nick)?;
            }
            "PRIVMSG" => self.handle_privmsg(msg)?,
            _ => {}
        }
        Ok(())
    }
}