//! Matrix handle_message — runs the LLM turn for a verified incoming message and
//! streams the assistant reply back to the room.

use crate::chat::util::drain_complete_paragraphs;
use crate::http::context::PermissionDecision;
use crate::llm::providers::claude_code::{ClaudeCodeProvider, ClaudeCodeResult};
use crate::slog;
use matrix_sdk::ruma::OwnedRoomId;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::time::Duration;
use tokio::sync::watch;

use super::super::context::BotContext;
use super::super::format::markdown_to_html;
use super::super::history::{ConversationEntry, ConversationRole, save_history};

use super::format_user_prompt;

pub(in crate::chat::transport::matrix::bot) 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.services.bot_name;
    let active_project_ctx = if let Some(ref ap) = ctx.gateway_active_project {
        let name = ap.read().await.clone();
        format!("[Active project: {name}]\n")
    } else {
        String::new()
    };
    let prompt = format!(
        "[Your name is {bot_name}. Refer to yourself as {bot_name}, not Claude.]\n{active_project_ctx}\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);

    // In gateway mode, run Claude Code in the gateway config directory so it
    // picks up the `.mcp.json` that points to the gateway's MCP proxy endpoint.
    // The gateway proxies tool calls to the active project automatically.
    // In standalone mode, use the project root directly.
    let project_root_str = if ctx.is_gateway() {
        ctx.services.project_root.to_string_lossy().to_string()
    } else {
        ctx.effective_project_root()
            .await
            .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.services.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.services.pending_perm_replies
                    .lock()
                    .await
                    .insert(room_id.to_string(), perm_fwd.response_tx);

                // Spawn a timeout task: auto-deny if the user does not respond.
                let pending = Arc::clone(&ctx.services.pending_perm_replies);
                let timeout_room_id = room_id.to_string();
                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.services.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.services.project_root, &guard);
    }
}

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