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

use matrix_sdk::config::SyncSettings;
use matrix_sdk::room::Room;
use matrix_sdk::Client;
use ruma::events::reaction::OriginalSyncReactionEvent;
use ruma::events::room::member::StrippedRoomMemberEvent;
use ruma::events::room::message::OriginalSyncRoomMessageEvent;
use ruma::events::room::redaction::OriginalSyncRoomRedactionEvent;
use tokio::sync::Mutex;
use tracing::{debug, error, info, warn};

use opensearch::OpenSearch;

use crate::archive::indexer::Indexer;
use crate::archive::schema::ArchiveDocument;
use crate::brain::conversation::{ContextMessage, ConversationManager};
use crate::brain::evaluator::{Engagement, Evaluator};
use crate::brain::responder::Responder;
use crate::config::Config;
use crate::context::{self, ResponseContext};
use crate::matrix_utils;
use crate::memory;

pub struct AppState {
    pub config: Arc<Config>,
    pub indexer: Arc<Indexer>,
    pub evaluator: Arc<Evaluator>,
    pub responder: Arc<Responder>,
    pub conversations: Arc<Mutex<ConversationManager>>,
    pub mistral: Arc<mistralai_client::v1::client::Client>,
    pub opensearch: OpenSearch,
    /// Tracks when Sol last responded in each room (for cooldown)
    pub last_response: Arc<Mutex<HashMap<String, Instant>>>,
    /// Tracks rooms where a response is currently being generated (in-flight guard)
    pub responding_in: Arc<Mutex<std::collections::HashSet<String>>>,
}

pub async fn start_sync(client: Client, state: Arc<AppState>) -> anyhow::Result<()> {
    // Register event handlers
    let s = state.clone();
    client.add_event_handler(
        move |event: OriginalSyncRoomMessageEvent, room: Room| {
            let state = s.clone();
            async move {
                if let Err(e) = handle_message(event, room, state).await {
                    error!("Error handling message: {e}");
                }
            }
        },
    );

    let s = state.clone();
    client.add_event_handler(
        move |event: OriginalSyncRoomRedactionEvent, _room: Room| {
            let state = s.clone();
            async move {
                handle_redaction(event, &state).await;
            }
        },
    );

    let s = state.clone();
    client.add_event_handler(
        move |event: OriginalSyncReactionEvent, _room: Room| {
            let state = s.clone();
            async move {
                handle_reaction(event, &state).await;
            }
        },
    );

    client.add_event_handler(
        move |event: StrippedRoomMemberEvent, room: Room| async move {
            handle_invite(event, room).await;
        },
    );

    info!("Starting Matrix sync loop");
    let settings = SyncSettings::default();
    client.sync(settings).await?;

    Ok(())
}

async fn handle_message(
    event: OriginalSyncRoomMessageEvent,
    room: Room,
    state: Arc<AppState>,
) -> anyhow::Result<()> {
    let sender = event.sender.to_string();
    let room_id = room.room_id().to_string();
    let event_id = event.event_id.to_string();
    let timestamp = event.origin_server_ts.0.into();

    // Check if this is an edit
    if let Some((original_id, new_body)) = matrix_utils::extract_edit(&event) {
        state
            .indexer
            .update_edit(&original_id.to_string(), &new_body)
            .await;
        return Ok(());
    }

    let Some(body) = matrix_utils::extract_body(&event) else {
        return Ok(());
    };

    let room_name = matrix_utils::room_display_name(&room);
    let sender_name = room
        .get_member_no_sync(&event.sender)
        .await
        .ok()
        .flatten()
        .and_then(|m| m.display_name().map(|s| s.to_string()));

    let reply_to = matrix_utils::extract_reply_to(&event).map(|id| id.to_string());
    let is_reply = reply_to.is_some();
    let thread_id = matrix_utils::extract_thread_id(&event).map(|id| id.to_string());

    // Archive the message
    let doc = ArchiveDocument {
        event_id: event_id.clone(),
        room_id: room_id.clone(),
        room_name: Some(room_name.clone()),
        sender: sender.clone(),
        sender_name: sender_name.clone(),
        timestamp,
        content: body.clone(),
        reply_to,
        thread_id,
        media_urls: Vec::new(),
        event_type: "m.room.message".into(),
        edited: false,
        redacted: false,
        reactions: Vec::new(),
    };
    state.indexer.add(doc).await;

    // Update conversation context
    let is_dm = room.is_direct().await.unwrap_or(false);

    let response_ctx = ResponseContext {
        matrix_user_id: sender.clone(),
        user_id: context::derive_user_id(&sender),
        display_name: sender_name.clone(),
        is_dm,
        is_reply,
        room_id: room_id.clone(),
    };

    {
        let mut convs = state.conversations.lock().await;
        convs.add_message(
            &room_id,
            is_dm,
            ContextMessage {
                sender: sender_name.clone().unwrap_or_else(|| sender.clone()),
                content: body.clone(),
                timestamp,
            },
        );
    }

    // Evaluate whether to respond
    let recent: Vec<String> = {
        let convs = state.conversations.lock().await;
        convs
            .get_context(&room_id)
            .iter()
            .map(|m| format!("{}: {}", m.sender, m.content))
            .collect()
    };

    let engagement = state
        .evaluator
        .evaluate(&sender, &body, is_dm, &recent, &state.mistral)
        .await;

    let (should_respond, is_spontaneous) = match engagement {
        Engagement::MustRespond { reason } => {
            info!(room = room_id.as_str(), ?reason, "Must respond");
            (true, false)
        }
        Engagement::MaybeRespond { relevance, hook } => {
            info!(room = room_id.as_str(), relevance, hook = hook.as_str(), "Maybe respond (spontaneous)");
            (true, true)
        }
        Engagement::React { emoji, relevance } => {
            info!(room = room_id.as_str(), relevance, emoji = emoji.as_str(), "Reacting with emoji");
            if let Err(e) = matrix_utils::send_reaction(&room, event.event_id.clone().into(), &emoji).await {
                error!("Failed to send reaction: {e}");
            }
            (false, false)
        }
        Engagement::Ignore => (false, false),
    };

    if !should_respond {
        return Ok(());
    }

    // In-flight guard: skip if we're already generating a response for this room
    {
        let responding = state.responding_in.lock().await;
        if responding.contains(&room_id) {
            debug!(room = room_id.as_str(), "Skipping — response already in flight for this room");
            return Ok(());
        }
    }

    // Cooldown check: skip spontaneous if we responded recently
    if is_spontaneous {
        let last = state.last_response.lock().await;
        if let Some(ts) = last.get(&room_id) {
            let elapsed = ts.elapsed().as_millis() as u64;
            let cooldown = state.config.behavior.cooldown_after_response_ms;
            if elapsed < cooldown {
                debug!(
                    room = room_id.as_str(),
                    elapsed_ms = elapsed,
                    cooldown_ms = cooldown,
                    "Skipping spontaneous — within cooldown period"
                );
                return Ok(());
            }
        }
    }

    // Mark room as in-flight
    {
        let mut responding = state.responding_in.lock().await;
        responding.insert(room_id.clone());
    }

    let context = {
        let convs = state.conversations.lock().await;
        convs.get_context(&room_id)
    };
    let members = matrix_utils::room_member_names(&room).await;
    let display_sender = sender_name.as_deref().unwrap_or(&sender);

    let response = state
        .responder
        .generate_response(
            &context,
            &body,
            display_sender,
            &room_name,
            &members,
            is_spontaneous,
            &state.mistral,
            &room,
            &response_ctx,
        )
        .await;

    if let Some(text) = response {
        // Reply with reference only when directly addressed. Spontaneous
        // and DM messages are sent as plain content — feels more natural.
        let content = if !is_spontaneous && !is_dm {
            matrix_utils::make_reply_content(&text, event.event_id.to_owned())
        } else {
            ruma::events::room::message::RoomMessageEventContent::text_markdown(&text)
        };
        if let Err(e) = room.send(content).await {
            error!("Failed to send response: {e}");
        } else {
            info!(room = room_id.as_str(), len = text.len(), is_dm, "Response sent");
        }
        // Post-response memory extraction (fire-and-forget)
        if state.config.behavior.memory_extraction_enabled {
            let ctx = response_ctx.clone();
            let mistral = state.mistral.clone();
            let os = state.opensearch.clone();
            let config = state.config.clone();
            let user_msg = body.clone();
            let sol_response = text.clone();

            tokio::spawn(async move {
                if let Err(e) = memory::extractor::extract_and_store(
                    &mistral, &os, &config, &ctx, &user_msg, &sol_response,
                )
                .await
                {
                    warn!("Memory extraction failed (non-fatal): {e}");
                }
            });
        }

        // Update last response timestamp
        let mut last = state.last_response.lock().await;
        last.insert(room_id.clone(), Instant::now());
    }

    // Clear in-flight flag
    {
        let mut responding = state.responding_in.lock().await;
        responding.remove(&room_id);
    }

    Ok(())
}

async fn handle_reaction(event: OriginalSyncReactionEvent, state: &AppState) {
    let target_event_id = event.content.relates_to.event_id.to_string();
    let sender = event.sender.to_string();
    let emoji = &event.content.relates_to.key;
    let timestamp: i64 = event.origin_server_ts.0.into();

    info!(
        target = target_event_id.as_str(),
        sender = sender.as_str(),
        emoji = emoji.as_str(),
        "Indexing reaction"
    );

    state.indexer.add_reaction(&target_event_id, &sender, emoji, timestamp).await;
}

async fn handle_redaction(event: OriginalSyncRoomRedactionEvent, state: &AppState) {
    if let Some(redacted_id) = &event.redacts {
        state.indexer.update_redaction(&redacted_id.to_string()).await;
    }
}

async fn handle_invite(event: StrippedRoomMemberEvent, room: Room) {
    // Only handle our own invites
    if event.state_key != room.own_user_id() {
        return;
    }

    info!(room_id = %room.room_id(), "Received invite, auto-joining");
    tokio::spawn(async move {
        for attempt in 0..3u32 {
            match room.join().await {
                Ok(_) => {
                    info!(room_id = %room.room_id(), "Joined room");
                    return;
                }
                Err(e) => {
                    warn!(room_id = %room.room_id(), attempt, "Failed to join: {e}");
                    tokio::time::sleep(std::time::Duration::from_secs(2u64.pow(attempt))).await;
                }
            }
        }
        error!(room_id = %room.room_id(), "Failed to join after retries");
    });
}