//! Bot-level command registry for the Matrix bot.
//!
//! Commands registered here are handled directly by the bot without invoking
//! the LLM. The registry is the single source of truth — the `help` command
//! iterates it automatically so new commands appear in the help output as soon
//! as they are added.

mod ambient;
mod cost;
mod git;
mod help;
mod move_story;
mod overview;
mod show;
mod status;

use crate::agents::AgentPool;
use std::collections::HashSet;
use std::path::Path;
use std::sync::{Arc, Mutex};

/// A bot-level command that is handled without LLM invocation.
pub struct BotCommand {
    /// The command keyword (e.g., `"help"`). Always lowercase.
    pub name: &'static str,
    /// Short description shown in help output.
    pub description: &'static str,
    /// Handler that produces the response text (Markdown), or `None` to fall
    /// through to the LLM (e.g. when a command requires direct addressing but
    /// the message arrived via ambient mode).
    pub handler: fn(&CommandContext) -> Option<String>,
}

/// Dispatch parameters passed to `try_handle_command`.
///
/// Groups all the caller-supplied context needed to dispatch and execute bot
/// commands.  Construct one per incoming message and pass it alongside the raw
/// message body.
///
/// All identifiers are platform-agnostic strings so this struct works with
/// any [`ChatTransport`](crate::transport::ChatTransport) implementation.
pub struct CommandDispatch<'a> {
    /// The bot's display name (e.g., "Timmy").
    pub bot_name: &'a str,
    /// The bot's full user ID (e.g., `"@timmy:homeserver.local"` on Matrix).
    pub bot_user_id: &'a str,
    /// Project root directory (needed by status, ambient).
    pub project_root: &'a Path,
    /// Agent pool (needed by status).
    pub agents: &'a AgentPool,
    /// Set of room IDs with ambient mode enabled (needed by ambient).
    pub ambient_rooms: &'a Arc<Mutex<HashSet<String>>>,
    /// The room this message came from (needed by ambient).
    pub room_id: &'a str,
}

/// Context passed to individual command handlers.
pub struct CommandContext<'a> {
    /// The bot's display name (e.g., "Timmy").
    pub bot_name: &'a str,
    /// Any text after the command keyword, trimmed.
    pub args: &'a str,
    /// Project root directory (needed by status, ambient).
    pub project_root: &'a Path,
    /// Agent pool (needed by status).
    pub agents: &'a AgentPool,
    /// Set of room IDs with ambient mode enabled (needed by ambient).
    pub ambient_rooms: &'a Arc<Mutex<HashSet<String>>>,
    /// The room this message came from (needed by ambient).
    pub room_id: &'a str,
}

/// Returns the full list of registered bot commands.
///
/// Add new commands here — they will automatically appear in `help` output.
pub fn commands() -> &'static [BotCommand] {
    &[
        BotCommand {
            name: "help",
            description: "Show this list of available commands",
            handler: help::handle_help,
        },
        BotCommand {
            name: "status",
            description: "Show pipeline status and agent availability",
            handler: status::handle_status,
        },
        BotCommand {
            name: "ambient",
            description: "Toggle ambient mode for this room: `ambient on` or `ambient off`",
            handler: ambient::handle_ambient,
        },
        BotCommand {
            name: "git",
            description: "Show git status: branch, uncommitted changes, and ahead/behind remote",
            handler: git::handle_git,
        },
        BotCommand {
            name: "htop",
            description: "Show live system and agent process dashboard (`htop`, `htop 10m`, `htop stop`)",
            handler: handle_htop_fallback,
        },
        BotCommand {
            name: "cost",
            description: "Show token spend: 24h total, top stories, breakdown by agent type, and all-time total",
            handler: cost::handle_cost,
        },
        BotCommand {
            name: "move",
            description: "Move a work item to a pipeline stage: `move <number> <stage>` (stages: backlog, current, qa, merge, done)",
            handler: move_story::handle_move,
        },
        BotCommand {
            name: "show",
            description: "Display the full text of a work item: `show <number>`",
            handler: show::handle_show,
        },
        BotCommand {
            name: "overview",
            description: "Show implementation summary for a merged story: `overview <number>`",
            handler: overview::handle_overview,
        },
        BotCommand {
            name: "start",
            description: "Start a coder on a story: `start <number>` or `start <number> opus`",
            handler: handle_start_fallback,
        },
        BotCommand {
            name: "delete",
            description: "Remove a work item from the pipeline: `delete <number>`",
            handler: handle_delete_fallback,
        },
        BotCommand {
            name: "reset",
            description: "Clear the current Claude Code session and start fresh",
            handler: handle_reset_fallback,
        },
    ]
}

/// Try to match a user message against a registered bot command.
///
/// The message is expected to be the raw body text from Matrix (e.g.,
/// `"@timmy help"`). The bot mention prefix is stripped before matching.
///
/// Returns `Some(response)` if a command matched and was handled, `None`
/// otherwise (the caller should fall through to the LLM).
pub fn try_handle_command(dispatch: &CommandDispatch<'_>, message: &str) -> Option<String> {
    let command_text = strip_bot_mention(message, dispatch.bot_name, dispatch.bot_user_id);
    let trimmed = command_text.trim();
    if trimmed.is_empty() {
        return None;
    }

    let (cmd_name, args) = match trimmed.split_once(char::is_whitespace) {
        Some((c, a)) => (c, a.trim()),
        None => (trimmed, ""),
    };
    let cmd_lower = cmd_name.to_ascii_lowercase();

    let ctx = CommandContext {
        bot_name: dispatch.bot_name,
        args,
        project_root: dispatch.project_root,
        agents: dispatch.agents,
        ambient_rooms: dispatch.ambient_rooms,
        room_id: dispatch.room_id,
    };

    commands()
        .iter()
        .find(|c| c.name == cmd_lower)
        .and_then(|c| (c.handler)(&ctx))
}

/// Strip the bot mention prefix from a raw message body.
///
/// Handles these forms (case-insensitive where applicable):
/// - `@bot_localpart:server.com rest` → `rest`
/// - `@bot_localpart rest` → `rest`
/// - `DisplayName rest` → `rest`
fn strip_bot_mention<'a>(message: &'a str, bot_name: &str, bot_user_id: &str) -> &'a str {
    let trimmed = message.trim();

    // Try full Matrix user ID (e.g. "@timmy:homeserver.local")
    if let Some(rest) = strip_prefix_ci(trimmed, bot_user_id) {
        return rest;
    }

    // Try @localpart (e.g. "@timmy")
    if let Some(localpart) = bot_user_id.split(':').next()
        && let Some(rest) = strip_prefix_ci(trimmed, localpart)
    {
        return rest;
    }

    // Try display name (e.g. "Timmy")
    if let Some(rest) = strip_prefix_ci(trimmed, bot_name) {
        return rest;
    }

    trimmed
}

/// Case-insensitive prefix strip that also requires the match to end at a
/// word boundary (whitespace, punctuation, or end-of-string).
fn strip_prefix_ci<'a>(text: &'a str, prefix: &str) -> Option<&'a str> {
    if text.len() < prefix.len() {
        return None;
    }
    if !text[..prefix.len()].eq_ignore_ascii_case(prefix) {
        return None;
    }
    let rest = &text[prefix.len()..];
    // Must be at end or followed by non-alphanumeric
    match rest.chars().next() {
        None => Some(rest), // exact match, empty remainder
        Some(c) if c.is_alphanumeric() || c == '-' || c == '_' => None, // not a word boundary
        _ => Some(rest),
    }
}

/// Fallback handler for the `htop` command when it is not intercepted by the
/// async handler in `on_room_message`.  In practice this is never called —
/// htop is detected and handled before `try_handle_command` is invoked.
/// The entry exists in the registry only so `help` lists it.
///
/// Returns `None` to prevent the LLM from receiving "htop" as a prompt.
fn handle_htop_fallback(_ctx: &CommandContext) -> Option<String> {
    None
}

/// Fallback handler for the `start` command when it is not intercepted by
/// the async handler in `on_room_message`.  In practice this is never called —
/// start is detected and handled before `try_handle_command` is invoked.
/// The entry exists in the registry only so `help` lists it.
///
/// Returns `None` to prevent the LLM from receiving "start" as a prompt.
fn handle_start_fallback(_ctx: &CommandContext) -> Option<String> {
    None
}

/// Fallback handler for the `delete` command when it is not intercepted by
/// the async handler in `on_room_message`.  In practice this is never called —
/// delete is detected and handled before `try_handle_command` is invoked.
/// The entry exists in the registry only so `help` lists it.
///
/// Returns `None` to prevent the LLM from receiving "delete" as a prompt.
fn handle_delete_fallback(_ctx: &CommandContext) -> Option<String> {
    None
}

/// Fallback handler for the `reset` command when it is not intercepted by
/// the async handler in `on_room_message`.  In practice this is never called —
/// reset is detected and handled before `try_handle_command` is invoked.
/// The entry exists in the registry only so `help` lists it.
///
/// Returns `None` to prevent the LLM from receiving "reset" as a prompt.
fn handle_reset_fallback(_ctx: &CommandContext) -> Option<String> {
    None
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[cfg(test)]
pub(crate) mod tests {
    use super::*;
    use crate::agents::AgentPool;

    // -- test helpers (shared with submodule tests) -------------------------

    pub fn test_ambient_rooms() -> Arc<Mutex<HashSet<String>>> {
        Arc::new(Mutex::new(HashSet::new()))
    }

    pub fn test_agents() -> Arc<AgentPool> {
        Arc::new(AgentPool::new_test(3000))
    }

    pub fn try_cmd(
        bot_name: &str,
        bot_user_id: &str,
        message: &str,
        ambient_rooms: &Arc<Mutex<HashSet<String>>>,
    ) -> Option<String> {
        let agents = test_agents();
        let room_id = "!test:example.com".to_string();
        let dispatch = CommandDispatch {
            bot_name,
            bot_user_id,
            project_root: std::path::Path::new("/tmp"),
            agents: &agents,
            ambient_rooms,
            room_id: &room_id,
        };
        try_handle_command(&dispatch, message)
    }

    pub fn try_cmd_addressed(bot_name: &str, bot_user_id: &str, message: &str) -> Option<String> {
        try_cmd(bot_name, bot_user_id, message, &test_ambient_rooms())
    }

    // Re-export commands() for submodule tests
    pub use super::commands;

    // -- strip_bot_mention --------------------------------------------------

    #[test]
    fn strip_mention_full_user_id() {
        let rest = strip_bot_mention(
            "@timmy:homeserver.local help",
            "Timmy",
            "@timmy:homeserver.local",
        );
        assert_eq!(rest.trim(), "help");
    }

    #[test]
    fn strip_mention_localpart() {
        let rest = strip_bot_mention("@timmy help me", "Timmy", "@timmy:homeserver.local");
        assert_eq!(rest.trim(), "help me");
    }

    #[test]
    fn strip_mention_display_name() {
        let rest = strip_bot_mention("Timmy help", "Timmy", "@timmy:homeserver.local");
        assert_eq!(rest.trim(), "help");
    }

    #[test]
    fn strip_mention_display_name_case_insensitive() {
        let rest = strip_bot_mention("timmy help", "Timmy", "@timmy:homeserver.local");
        assert_eq!(rest.trim(), "help");
    }

    #[test]
    fn strip_mention_no_match_returns_original() {
        let rest = strip_bot_mention("hello world", "Timmy", "@timmy:homeserver.local");
        assert_eq!(rest, "hello world");
    }

    #[test]
    fn strip_mention_does_not_match_longer_name() {
        // "@timmybot" should NOT match "@timmy"
        let rest = strip_bot_mention("@timmybot help", "Timmy", "@timmy:homeserver.local");
        assert_eq!(rest, "@timmybot help");
    }

    #[test]
    fn strip_mention_comma_after_name() {
        let rest = strip_bot_mention("@timmy, help", "Timmy", "@timmy:homeserver.local");
        assert_eq!(rest.trim().trim_start_matches(',').trim(), "help");
    }

    // -- try_handle_command -------------------------------------------------

    #[test]
    fn unknown_command_returns_none() {
        let result = try_cmd_addressed(
            "Timmy",
            "@timmy:homeserver.local",
            "@timmy what is the weather?",
        );
        assert!(result.is_none(), "non-command should return None");
    }

    #[test]
    fn empty_message_after_mention_returns_none() {
        let result = try_cmd_addressed("Timmy", "@timmy:homeserver.local", "@timmy");
        assert!(
            result.is_none(),
            "bare mention with no command should fall through to LLM"
        );
    }

    #[test]
    fn htop_command_falls_through_to_none() {
        // The htop handler returns None so the message is handled asynchronously
        // in on_room_message, not here.  try_handle_command must return None.
        let result = try_cmd_addressed("Timmy", "@timmy:homeserver.local", "@timmy htop");
        assert!(
            result.is_none(),
            "htop should not produce a sync response (handled async): {result:?}"
        );
    }

    // -- strip_prefix_ci ----------------------------------------------------

    #[test]
    fn strip_prefix_ci_basic() {
        assert_eq!(strip_prefix_ci("Hello world", "hello"), Some(" world"));
    }

    #[test]
    fn strip_prefix_ci_no_match() {
        assert_eq!(strip_prefix_ci("goodbye", "hello"), None);
    }

    #[test]
    fn strip_prefix_ci_word_boundary_required() {
        assert_eq!(strip_prefix_ci("helloworld", "hello"), None);
    }

    #[test]
    fn strip_prefix_ci_exact_match() {
        assert_eq!(strip_prefix_ci("hello", "hello"), Some(""));
    }

    // -- commands registry --------------------------------------------------

    #[test]
    fn commands_registry_is_not_empty() {
        assert!(
            !commands().is_empty(),
            "command registry must contain at least one command"
        );
    }

    #[test]
    fn all_command_names_are_lowercase() {
        for cmd in commands() {
            assert_eq!(
                cmd.name,
                cmd.name.to_ascii_lowercase(),
                "command name '{}' must be lowercase",
                cmd.name
            );
        }
    }

    #[test]
    fn all_commands_have_descriptions() {
        for cmd in commands() {
            assert!(
                !cmd.description.is_empty(),
                "command '{}' must have a description",
                cmd.name
            );
        }
    }
}