use crate::chat::util::{drain_complete_paragraphs, is_permission_approval};
use crate::http::context::PermissionDecision;
use crate::llm::providers::claude_code::{ClaudeCodeProvider, ClaudeCodeResult};
use crate::slog;
use matrix_sdk::{
    Client,
    event_handler::Ctx,
    room::Room,
    ruma::{
        OwnedRoomId,
        events::room::message::{MessageType, OriginalSyncRoomMessageEvent},
    },
};
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::time::Duration;
use tokio::sync::watch;

use super::context::BotContext;
use super::format::markdown_to_html;
use super::history::{ConversationEntry, ConversationRole, save_history};
use super::mentions::{is_reply_to_bot, mentions_bot};
use super::verification::check_sender_verified;

/// Build the user-facing prompt for a single turn.  In multi-user rooms the
/// sender is included so the LLM can distinguish participants.
pub(super) fn format_user_prompt(sender: &str, message: &str) -> String {
    format!("{sender}: {message}")
}

/// Matrix event handler for room messages. Each invocation spawns an
/// independent task so the sync loop is not blocked by LLM calls.
pub(super) async fn on_room_message(
    ev: OriginalSyncRoomMessageEvent,
    room: Room,
    client: Client,
    Ctx(ctx): Ctx<BotContext>,
) {
    let incoming_room_id = room.room_id().to_owned();

    slog!(
        "[matrix-bot] Event received: room={} sender={}",
        incoming_room_id,
        ev.sender,
    );

    // Only handle messages from rooms we are configured to listen in.
    if !ctx.target_room_ids.iter().any(|r| r == &incoming_room_id) {
        slog!("[matrix-bot] Ignoring message from unconfigured room {incoming_room_id}");
        return;
    }

    // Ignore the bot's own messages to prevent echo loops.
    if ev.sender == ctx.bot_user_id {
        return;
    }

    // Only respond to users on the allowlist (fail-closed).
    if !ctx.allowed_users.iter().any(|u| u == ev.sender.as_str()) {
        slog!(
            "[matrix-bot] Ignoring message from unauthorised user: {}",
            ev.sender
        );
        return;
    }

    // Only handle plain text messages.
    let (body, formatted_body) = match &ev.content.msgtype {
        MessageType::Text(t) => (t.body.clone(), t.formatted.as_ref().map(|f| f.body.clone())),
        _ => return,
    };

    // Only respond when the bot is directly addressed (mentioned by name/ID),
    // when the message is a reply to one of the bot's own messages, or when
    // ambient mode is enabled for this room.
    let is_addressed = mentions_bot(&body, formatted_body.as_deref(), &ctx.bot_user_id)
        || is_reply_to_bot(ev.content.relates_to.as_ref(), &ctx.bot_sent_event_ids).await;
    let room_id_str = incoming_room_id.to_string();
    let is_ambient = ctx.ambient_rooms.lock().unwrap().contains(&room_id_str);

    // Always let "ambient on" through — it is the one command that must work
    // even when the bot is not mentioned and ambient mode is off, otherwise
    // there is no way to re-enable ambient mode without an @-mention.
    let is_ambient_on = body
        .to_ascii_lowercase()
        .contains("ambient on");

    if !is_addressed && !is_ambient && !is_ambient_on {
        slog!(
            "[matrix-bot] Ignoring unaddressed message from {}",
            ev.sender
        );
        return;
    }

    // Reject commands from unencrypted rooms — E2EE is mandatory.
    if !room.encryption_state().is_encrypted() {
        slog!(
            "[matrix-bot] Rejecting message from {} — room {} is not encrypted. \
             Commands are only accepted from encrypted rooms.",
            ev.sender,
            incoming_room_id
        );
        return;
    }

    // Always verify that the sender has a cross-signing identity.
    // This check is unconditional and cannot be disabled via config.
    match check_sender_verified(&client, &ev.sender).await {
        Ok(true) => { /* sender has a cross-signing identity — proceed */ }
        Ok(false) => {
            slog!(
                "[matrix-bot] Rejecting message from {} — no cross-signing identity \
                 found in encrypted room {}",
                ev.sender,
                incoming_room_id
            );
            return;
        }
        Err(e) => {
            slog!(
                "[matrix-bot] Error checking verification for {}: {e} — \
                 rejecting message (fail-closed)",
                ev.sender
            );
            return;
        }
    }

    // If there is a pending permission prompt for this room, interpret the
    // message as a yes/no response instead of starting a new chat.
    {
        let mut pending = ctx.pending_perm_replies.lock().await;
        if let Some(tx) = pending.remove(&incoming_room_id) {
            let decision = if is_permission_approval(&body) {
                PermissionDecision::Approve
            } else {
                PermissionDecision::Deny
            };
            let _ = tx.send(decision);
            let confirmation = if decision == PermissionDecision::Approve {
                "Permission approved."
            } else {
                "Permission denied."
            };
            let html = markdown_to_html(confirmation);
            if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, confirmation, &html).await
                && let Ok(event_id) = msg_id.parse()
            {
                ctx.bot_sent_event_ids.lock().await.insert(event_id);
            }
            return;
        }
    }

    let sender = ev.sender.to_string();
    let user_message = body;
    slog!("[matrix-bot] Message from {sender}: {user_message}");

    // Check for bot-level commands (help, status, ambient, …) before invoking
    // the LLM.  All commands are registered in commands.rs — no special-casing
    // needed here.
    let dispatch = super::super::commands::CommandDispatch {
        bot_name: &ctx.bot_name,
        bot_user_id: ctx.bot_user_id.as_str(),
        project_root: &ctx.project_root,
        agents: &ctx.agents,
        ambient_rooms: &ctx.ambient_rooms,
        room_id: &room_id_str,
    };
    if let Some((response, response_html)) = super::super::commands::try_handle_command_with_html(&dispatch, &user_message) {
        slog!("[matrix-bot] Handled bot command from {sender}");
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &response_html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the assign command, which requires async agent ops (stop +
    // start) and cannot be handled by the sync command registry.
    if let Some(assign_cmd) = super::super::assign::extract_assign_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    ) {
        let response = match assign_cmd {
            super::super::assign::AssignCommand::Assign {
                story_number,
                model,
            } => {
                slog!(
                    "[matrix-bot] Handling assign command from {sender}: story {story_number} model={model}"
                );
                super::super::assign::handle_assign(
                    &ctx.bot_name,
                    &story_number,
                    &model,
                    &ctx.project_root,
                    &ctx.agents,
                )
                .await
            }
            super::super::assign::AssignCommand::BadArgs => {
                format!(
                    "Usage: `{} assign <number> <model>` (e.g. `assign 42 opus`)",
                    ctx.bot_name
                )
            }
        };
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the htop command, which requires async Matrix access (Room)
    // and cannot be handled by the sync command registry.
    if let Some(htop_cmd) = super::super::htop::extract_htop_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    ) {
        slog!("[matrix-bot] Handling htop command from {sender}: {htop_cmd:?}");
        match htop_cmd {
            super::super::htop::HtopCommand::Stop => {
                super::super::htop::handle_htop_stop(
                    &*ctx.transport,
                    &room_id_str,
                    &ctx.htop_sessions,
                )
                .await;
            }
            super::super::htop::HtopCommand::Start { duration_secs } => {
                super::super::htop::handle_htop_start(
                    &ctx.transport,
                    &room_id_str,
                    &ctx.htop_sessions,
                    Arc::clone(&ctx.agents),
                    duration_secs,
                )
                .await;
            }
        }
        return;
    }

    // Check for the delete command, which requires async agent/worktree ops
    // and cannot be handled by the sync command registry.
    if let Some(del_cmd) = super::super::delete::extract_delete_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    ) {
        let response = match del_cmd {
            super::super::delete::DeleteCommand::Delete { story_number } => {
                slog!(
                    "[matrix-bot] Handling delete command from {sender}: story {story_number}"
                );
                super::super::delete::handle_delete(
                    &ctx.bot_name,
                    &story_number,
                    &ctx.project_root,
                    &ctx.agents,
                )
                .await
            }
            super::super::delete::DeleteCommand::BadArgs => {
                format!("Usage: `{} delete <number>`", ctx.bot_name)
            }
        };
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the rmtree command, which requires async agent/worktree ops
    // and cannot be handled by the sync command registry.
    if let Some(rmtree_cmd) = super::super::rmtree::extract_rmtree_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    ) {
        let response = match rmtree_cmd {
            super::super::rmtree::RmtreeCommand::Rmtree { story_number } => {
                slog!(
                    "[matrix-bot] Handling rmtree command from {sender}: story {story_number}"
                );
                super::super::rmtree::handle_rmtree(
                    &ctx.bot_name,
                    &story_number,
                    &ctx.project_root,
                    &ctx.agents,
                )
                .await
            }
            super::super::rmtree::RmtreeCommand::BadArgs => {
                format!("Usage: `{} rmtree <number>`", ctx.bot_name)
            }
        };
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the start command, which requires async agent ops and cannot
    // be handled by the sync command registry.
    if let Some(start_cmd) = super::super::start::extract_start_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    ) {
        let response = match start_cmd {
            super::super::start::StartCommand::Start {
                story_number,
                agent_hint,
            } => {
                slog!(
                    "[matrix-bot] Handling start command from {sender}: story {story_number} agent={agent_hint:?}"
                );
                super::super::start::handle_start(
                    &ctx.bot_name,
                    &story_number,
                    agent_hint.as_deref(),
                    &ctx.project_root,
                    &ctx.agents,
                )
                .await
            }
            super::super::start::StartCommand::BadArgs => {
                format!(
                    "Usage: `{} start <number>` or `{} start <number> opus`",
                    ctx.bot_name, ctx.bot_name
                )
            }
        };
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the reset command, which requires async access to the shared
    // conversation history and cannot be handled by the sync command registry.
    if super::super::reset::extract_reset_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    )
    .is_some()
    {
        slog!("[matrix-bot] Handling reset command from {sender}");
        let response = super::super::reset::handle_reset(
            &ctx.bot_name,
            &incoming_room_id,
            &ctx.history,
            &ctx.project_root,
        )
        .await;
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the rebuild command, which requires async agent and process ops
    // and cannot be handled by the sync command registry.
    if super::super::rebuild::extract_rebuild_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    )
    .is_some()
    {
        slog!("[matrix-bot] Handling rebuild command from {sender}");
        // Acknowledge immediately — the rebuild may take a while or re-exec.
        let ack = "Rebuilding server… this may take a moment.";
        let ack_html = markdown_to_html(ack);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, ack, &ack_html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        let response = super::super::rebuild::handle_rebuild(
            &ctx.bot_name,
            &ctx.project_root,
            &ctx.agents,
        )
        .await;
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Check for the timer command, which requires async file I/O and cannot
    // be handled by the sync command registry.
    if let Some(timer_cmd) = crate::chat::timer::extract_timer_command(
        &user_message,
        &ctx.bot_name,
        ctx.bot_user_id.as_str(),
    ) {
        slog!("[matrix-bot] Handling timer command from {sender}: {timer_cmd:?}");
        let response = crate::chat::timer::handle_timer_command(
            timer_cmd,
            &ctx.timer_store,
            &ctx.project_root,
        )
        .await;
        let html = markdown_to_html(&response);
        if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &response, &html).await
            && let Ok(event_id) = msg_id.parse()
        {
            ctx.bot_sent_event_ids.lock().await.insert(event_id);
        }
        return;
    }

    // Spawn a separate task so the Matrix sync loop is not blocked while we
    // wait for the LLM response (which can take several seconds).
    tokio::spawn(async move {
        handle_message(room_id_str, incoming_room_id, ctx, sender, user_message).await;
    });
}

pub(super) async fn handle_message(
    room_id_str: String,
    room_id: OwnedRoomId,
    ctx: BotContext,
    sender: String,
    user_message: String,
) {
    // Look up the room's existing Claude Code session ID (if any) so we can
    // resume the conversation with structured API messages instead of
    // flattening history into a text prefix.
    let resume_session_id: Option<String> = {
        let guard = ctx.history.lock().await;
        guard
            .get(&room_id)
            .and_then(|conv| conv.session_id.clone())
    };

    // The prompt is just the current message with sender attribution.
    // Prior conversation context is carried by the Claude Code session.
    let bot_name = &ctx.bot_name;
    let prompt = format!(
        "[Your name is {bot_name}. Refer to yourself as {bot_name}, not Claude.]\n\n{}",
        format_user_prompt(&sender, &user_message)
    );

    let provider = ClaudeCodeProvider::new();
    let (cancel_tx, mut cancel_rx) = watch::channel(false);
    // Keep the sender alive for the duration of the call.
    let _cancel_tx = cancel_tx;

    // Channel for sending complete paragraphs to the Matrix posting task.
    let (msg_tx, mut msg_rx) = tokio::sync::mpsc::unbounded_channel::<String>();
    let msg_tx_for_callback = msg_tx.clone();

    // Spawn a task to post messages via the transport as they arrive so we
    // don't block the LLM stream while waiting for send round-trips.
    let post_transport = Arc::clone(&ctx.transport);
    let post_room_id = room_id_str.clone();
    let sent_ids = Arc::clone(&ctx.bot_sent_event_ids);
    let sent_ids_for_post = Arc::clone(&sent_ids);
    let post_task = tokio::spawn(async move {
        while let Some(chunk) = msg_rx.recv().await {
            let html = markdown_to_html(&chunk);
            if let Ok(msg_id) = post_transport.send_message(&post_room_id, &chunk, &html).await
                && let Ok(event_id) = msg_id.parse()
            {
                sent_ids_for_post.lock().await.insert(event_id);
            }
        }
    });

    // Shared state between the sync token callback and the async outer scope.
    let buffer = Arc::new(std::sync::Mutex::new(String::new()));
    let buffer_for_callback = Arc::clone(&buffer);
    let sent_any_chunk = Arc::new(AtomicBool::new(false));
    let sent_any_chunk_for_callback = Arc::clone(&sent_any_chunk);

    let project_root_str = ctx.project_root.to_string_lossy().to_string();
    let chat_fut = provider.chat_stream(
        &prompt,
        &project_root_str,
        resume_session_id.as_deref(),
        None,
        &mut cancel_rx,
        move |token| {
            let mut buf = buffer_for_callback.lock().unwrap();
            buf.push_str(token);
            // Flush complete paragraphs as they arrive.
            let paragraphs = drain_complete_paragraphs(&mut buf);
            for chunk in paragraphs {
                sent_any_chunk_for_callback.store(true, Ordering::Relaxed);
                let _ = msg_tx_for_callback.send(chunk);
            }
        },
        |_thinking| {}, // Discard thinking tokens
        |_activity| {}, // Discard activity signals
    );
    tokio::pin!(chat_fut);

    // Lock the permission receiver for the duration of this chat session.
    // Permission requests from the MCP `prompt_permission` tool arrive here.
    let mut perm_rx_guard = ctx.perm_rx.lock().await;

    let result = loop {
        tokio::select! {
            r = &mut chat_fut => break r,

            Some(perm_fwd) = perm_rx_guard.recv() => {
                // Post the permission prompt to the room via the transport.
                let prompt_msg = format!(
                    "**Permission Request**\n\n\
                     Tool: `{}`\n```json\n{}\n```\n\n\
                     Reply **yes** to approve or **no** to deny.",
                    perm_fwd.tool_name,
                    serde_json::to_string_pretty(&perm_fwd.tool_input)
                        .unwrap_or_else(|_| perm_fwd.tool_input.to_string()),
                );
                let html = markdown_to_html(&prompt_msg);
                if let Ok(msg_id) = ctx.transport.send_message(&room_id_str, &prompt_msg, &html).await
                    && let Ok(event_id) = msg_id.parse()
                {
                    sent_ids.lock().await.insert(event_id);
                }

                // Store the MCP oneshot sender so the event handler can
                // resolve it when the user replies yes/no.
                ctx.pending_perm_replies
                    .lock()
                    .await
                    .insert(room_id.clone(), perm_fwd.response_tx);

                // Spawn a timeout task: auto-deny if the user does not respond.
                let pending = Arc::clone(&ctx.pending_perm_replies);
                let timeout_room_id = room_id.clone();
                let timeout_transport = Arc::clone(&ctx.transport);
                let timeout_room_id_str = room_id_str.clone();
                let timeout_sent_ids = Arc::clone(&ctx.bot_sent_event_ids);
                let timeout_secs = ctx.permission_timeout_secs;
                tokio::spawn(async move {
                    tokio::time::sleep(Duration::from_secs(timeout_secs)).await;
                    if let Some(tx) = pending.lock().await.remove(&timeout_room_id) {
                        let _ = tx.send(PermissionDecision::Deny);
                        let msg = "Permission request timed out — denied (fail-closed).";
                        let html = markdown_to_html(msg);
                        if let Ok(msg_id) = timeout_transport
                            .send_message(&timeout_room_id_str, msg, &html)
                            .await
                            && let Ok(event_id) = msg_id.parse()
                        {
                            timeout_sent_ids.lock().await.insert(event_id);
                        }
                    }
                });
            }
        }
    };
    drop(perm_rx_guard);

    // Flush any remaining text that didn't end with a paragraph boundary.
    let remaining = buffer.lock().unwrap().trim().to_string();
    let did_send_any = sent_any_chunk.load(Ordering::Relaxed);

    let (assistant_reply, new_session_id) = match result {
        Ok(ClaudeCodeResult {
            messages,
            session_id,
        }) => {
            let reply = if !remaining.is_empty() {
                let _ = msg_tx.send(remaining.clone());
                remaining
            } else if !did_send_any {
                // Nothing was streamed at all (e.g. only tool calls with no
                // final text) — fall back to the last assistant message from
                // the structured result.
                let last_text = messages
                    .iter()
                    .rev()
                    .find(|m| m.role == crate::llm::types::Role::Assistant && !m.content.is_empty())
                    .map(|m| m.content.clone())
                    .unwrap_or_default();
                if !last_text.is_empty() {
                    let _ = msg_tx.send(last_text.clone());
                }
                last_text
            } else {
                remaining
            };
            slog!("[matrix-bot] session_id from chat_stream: {:?}", session_id);
            (reply, session_id)
        }
        Err(e) => {
            slog!("[matrix-bot] LLM error: {e}");
            let err_msg = if let Some(url) = crate::llm::oauth::extract_login_url_from_error(&e) {
                format!(
                    "Authentication required. [Click here to log in to Claude]({url})"
                )
            } else {
                format!("Error processing your request: {e}")
            };
            let _ = msg_tx.send(err_msg.clone());
            (err_msg, None)
        }
    };

    // Drop the sender to signal the posting task that no more messages will
    // arrive, then wait for all pending Matrix sends to complete.
    drop(msg_tx);
    let _ = post_task.await;

    // Record this exchange in the per-room conversation history and persist
    // the session ID so the next turn resumes with structured API messages.
    if !assistant_reply.starts_with("Error processing") {
        let mut guard = ctx.history.lock().await;
        let conv = guard.entry(room_id).or_default();

        // Store the session ID so the next turn uses --resume.
        slog!("[matrix-bot] storing session_id: {:?} (was: {:?})", new_session_id, conv.session_id);
        if new_session_id.is_some() {
            conv.session_id = new_session_id;
        }

        conv.entries.push(ConversationEntry {
            role: ConversationRole::User,
            sender: sender.clone(),
            content: user_message,
        });
        conv.entries.push(ConversationEntry {
            role: ConversationRole::Assistant,
            sender: String::new(),
            content: assistant_reply,
        });

        // Trim to the configured maximum, dropping the oldest entries first.
        // The session_id is preserved: Claude Code's --resume loads the full
        // conversation from its own session transcript on disk, so trimming
        // our local tracking doesn't affect the LLM's context.
        if conv.entries.len() > ctx.history_size {
            let excess = conv.entries.len() - ctx.history_size;
            conv.entries.drain(..excess);
        }

        // Persist to disk so history survives server restarts.
        save_history(&ctx.project_root, &guard);
    }
}

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

#[cfg(test)]
mod tests {
    use super::*;

    // -- format_user_prompt -------------------------------------------------

    #[test]
    fn format_user_prompt_includes_sender_and_message() {
        let prompt = format_user_prompt("@alice:example.com", "Hello!");
        assert_eq!(prompt, "@alice:example.com: Hello!");
    }

    #[test]
    fn format_user_prompt_different_users() {
        let prompt = format_user_prompt("@bob:example.com", "What's up?");
        assert_eq!(prompt, "@bob:example.com: What's up?");
    }

    // -- OAuth login link formatting ----------------------------------------

    #[test]
    fn oauth_error_produces_login_link() {
        let err = "OAuth session expired or credentials missing. Please log in: http://localhost:3001/oauth/authorize";
        let url = crate::llm::oauth::extract_login_url_from_error(err);
        assert!(url.is_some(), "should extract URL from OAuth error");
        let msg = format!("Authentication required. [Click here to log in to Claude]({})", url.unwrap());
        assert!(msg.contains("http://localhost:3001/oauth/authorize"));
        assert!(msg.contains("[Click here to log in to Claude]"));
    }

    #[test]
    fn non_oauth_error_not_formatted_as_link() {
        let err = "Some unrelated error";
        assert!(crate::llm::oauth::extract_login_url_from_error(err).is_none());
    }

    // -- bot_name / system prompt -------------------------------------------

    #[test]
    fn bot_name_system_prompt_format() {
        let bot_name = "Timmy";
        let system_prompt =
            format!("Your name is {bot_name}. Refer to yourself as {bot_name}, not Claude.");
        assert_eq!(
            system_prompt,
            "Your name is Timmy. Refer to yourself as Timmy, not Claude."
        );
    }
}