use crate::AppState;
use crate::auth::UserSession;

use std::collections::{HashMap, HashSet};
use std::convert::Infallible;
use std::fmt::Display;
use std::time::Duration;

use axum::{
    Json, Router,
    extract::{Path, State},
    http::StatusCode,
    response::{
        IntoResponse,
        sse::{Event, KeepAlive, Sse},
    },
    routing::{get, post},
};
use futures_util::StreamExt;
use serde::{Deserialize, Serialize};
use tokio::sync::broadcast;
use tokio_stream::wrappers::BroadcastStream;
use tokio_tungstenite::{connect_async, tungstenite::Message as TungsteniteMessage};
use tower_sessions::Session;

pub fn polls_router() -> Router<AppState> {
    Router::new()
        .route("/poll", post(create_poll))
        .route("/polls", get(find_polls))
        .route("/poll/{id}/events", get(subscribe_poll))
        .route("/poll/{id}/end", post(end_poll))
}

// -----Structs-----

#[derive(Debug, Clone, Deserialize)]
pub struct PollConfig {
    pub name: String,
    pub options: Vec<String>,
    pub duration: u32,
}

impl Display for PollConfig {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "Name: {}, Choices: {:?}, Duration: {}min(s)",
            self.name, self.options, self.duration
        )
    }
}

#[derive(Debug, Clone, Serialize)]
pub struct PollUpdate {
    pub event_type: String,
    pub votes: HashMap<String, u32>,
    pub total_voters: u32,
}

#[derive(Debug)]
pub struct ActivePoll {
    pub config: PollConfig,
    pub votes: HashMap<String, u32>,
    pub voters: HashSet<String>,
    pub tx: broadcast::Sender<PollUpdate>,
    pub shutdown_tx: Option<tokio::sync::oneshot::Sender<()>>,
}

#[derive(Debug, Serialize)]
struct CreatePollResponse {
    poll_id: String,
    config: PollConfigResponse,
}

#[derive(Debug, Serialize)]
struct PollConfigResponse {
    name: String,
    options: Vec<String>,
}

#[derive(Debug, Serialize)]
struct Poll {
    active: bool,
    name: String,
    options: Vec<String>,
    total_votes: i32,
}

#[derive(Debug, Serialize)]
struct FindPollsResponse {
    polls: Vec<Poll>,
}
// -----Handlers-----

async fn create_poll(
    State(state): State<AppState>,
    session: Session,
    Json(config): Json<PollConfig>,
) -> impl IntoResponse {
    // Get user session
    let user_session = match get_user_session(&session).await {
        Ok(s) => s,
        Err(response) => return response,
    };

    println!(
        "Creating poll '{}' for channel: {}",
        config.name, user_session.channel
    );

    // Generate poll ID
    let poll_id = nanoid::nanoid!(10);

    // Create broadcast channel for updates
    let (tx, _) = broadcast::channel::<PollUpdate>(100);
    let (shutdown_tx, shutdown_rx) = tokio::sync::oneshot::channel();

    // Initialize vote counts
    let mut votes = HashMap::new();
    for option in &config.options {
        votes.insert(option.clone(), 0);
    }

    // Store poll state
    let active_poll = ActivePoll {
        config: config.clone(),
        votes: votes.clone(),
        voters: HashSet::new(),
        tx: tx.clone(),
        shutdown_tx: Some(shutdown_tx),
    };

    state
        .active_polls
        .write()
        .await
        .insert(poll_id.clone(), active_poll);

    // Spawn EventSub listener task
    let poll_id_clone = poll_id.clone();
    let state_clone = state.clone();
    tokio::spawn(async move {
        if let Err(e) = eventsub_listener(
            state_clone,
            poll_id_clone.clone(),
            user_session,
            shutdown_rx,
        )
        .await
        {
            eprintln!("EventSub listener error for poll {}: {}", poll_id_clone, e);
        }
    });

    (
        StatusCode::CREATED,
        Json(CreatePollResponse {
            poll_id,
            config: PollConfigResponse {
                name: config.name,
                options: config.options,
            },
        }),
    )
        .into_response()
}

async fn find_polls() -> Json<FindPollsResponse> {
    let x = Poll {
        active: false,
        name: "Poll A".to_string(),
        options: vec!["Option A".to_string(), "Option B".to_string()],
        total_votes: 12,
    };
    Json(FindPollsResponse { polls: vec![x] })
}

async fn subscribe_poll(
    State(state): State<AppState>,
    Path(poll_id): Path<String>,
) -> impl IntoResponse {
    let polls = state.active_polls.read().await;

    let Some(poll) = polls.get(&poll_id) else {
        return (StatusCode::NOT_FOUND, "Poll not found").into_response();
    };

    let rx = poll.tx.subscribe();

    // Send initial state
    let initial_update = PollUpdate {
        event_type: "initial".to_string(),
        votes: poll.votes.clone(),
        total_voters: poll.voters.len() as u32,
    };

    drop(polls); // Release lock before streaming

    let stream = async_stream::stream! {
        // Send initial state
        yield Ok::<_, Infallible>(Event::default().json_data(&initial_update).unwrap());

        // Stream updates
        let mut stream = BroadcastStream::new(rx);
        while let Some(result) = stream.next().await {
            match result {
                Ok(update) => {
                    yield Ok(Event::default().json_data(&update).unwrap());
                    if update.event_type == "ended" {
                        break;
                    }
                }
                Err(_) => break, // Channel closed
            }
        }
    };

    Sse::new(stream)
        .keep_alive(KeepAlive::default().interval(Duration::from_secs(15)))
        .into_response()
}

async fn end_poll(
    State(state): State<AppState>,
    Path(poll_id): Path<String>,
    session: Session,
) -> impl IntoResponse {
    // Verify user is authenticated
    if get_user_session(&session).await.is_err() {
        return (StatusCode::UNAUTHORIZED, "Not authenticated").into_response();
    }

    let mut polls = state.active_polls.write().await;

    let Some(poll) = polls.remove(&poll_id) else {
        return (StatusCode::NOT_FOUND, "Poll not found").into_response();
    };

    // Send final update
    let final_update = PollUpdate {
        event_type: "ended".to_string(),
        votes: poll.votes.clone(),
        total_voters: poll.voters.len() as u32,
    };
    let _ = poll.tx.send(final_update);

    // Signal shutdown to EventSub task
    if let Some(shutdown_tx) = poll.shutdown_tx {
        let _ = shutdown_tx.send(());
    }

    (StatusCode::OK, "Poll ended").into_response()
}

// -----Helper Functions-----

async fn get_user_session(session: &Session) -> Result<UserSession, axum::response::Response> {
    match session.get_value("user_session").await {
        Ok(Some(user_session_json)) => serde_json::from_value::<UserSession>(user_session_json)
            .map_err(|e| {
                (
                    StatusCode::INTERNAL_SERVER_ERROR,
                    format!("Error deserializing user session: {}", e),
                )
                    .into_response()
            }),
        Ok(None) => Err((StatusCode::UNAUTHORIZED, "Not authenticated").into_response()),
        Err(e) => Err((
            StatusCode::INTERNAL_SERVER_ERROR,
            format!("Error retrieving session: {}", e),
        )
            .into_response()),
    }
}

// -----EventSub Integration-----

#[derive(Debug, Deserialize)]
struct EventSubMessage {
    metadata: EventSubMetadata,
    payload: serde_json::Value,
}

#[derive(Debug, Deserialize)]
struct EventSubMetadata {
    message_type: String,
    #[serde(default)]
    subscription_type: Option<String>,
}

#[derive(Debug, Deserialize)]
struct WelcomePayload {
    session: EventSubSession,
}

#[derive(Debug, Deserialize)]
struct EventSubSession {
    id: String,
}

#[derive(Debug, Deserialize)]
struct ChatMessageEvent {
    chatter_user_id: String,
    message: ChatMessage,
}

#[derive(Debug, Deserialize)]
struct ChatMessage {
    text: String,
}

async fn eventsub_listener(
    state: AppState,
    poll_id: String,
    user_session: UserSession,
    mut shutdown_rx: tokio::sync::oneshot::Receiver<()>,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    println!("Starting EventSub listener for poll: {}", poll_id);

    // Connect to Twitch EventSub WebSocket
    let twitch_ws_url = "wss://eventsub.wss.twitch.tv/ws";
    let (ws_stream, _) = connect_async(twitch_ws_url).await?;
    println!("Connected to Twitch EventSub WebSocket");

    let (mut write, mut read) = ws_stream.split();
    use futures_util::{SinkExt, StreamExt};

    // Wait for welcome message and get session_id
    let session_id = loop {
        tokio::select! {
            _ = &mut shutdown_rx => {
                println!("Shutdown signal received before welcome");
                return Ok(());
            }
            msg = read.next() => {
                match msg {
                    Some(Ok(TungsteniteMessage::Text(text))) => {
                        let message: EventSubMessage = serde_json::from_str(&text)?;
                        if message.metadata.message_type == "session_welcome" {
                            let payload: WelcomePayload = serde_json::from_value(message.payload)?;
                            println!("Received session_id: {}", payload.session.id);
                            break payload.session.id;
                        }
                    }
                    Some(Ok(TungsteniteMessage::Ping(data))) => {
                        write.send(TungsteniteMessage::Pong(data)).await?;
                    }
                    Some(Err(e)) => return Err(e.into()),
                    None => return Err("WebSocket closed before welcome".into()),
                    _ => {}
                }
            }
        }
    };

    // Subscribe to channel.chat.message
    subscribe_to_chat_messages(
        &state.client_id,
        &user_session.access_token,
        &user_session.user_id,
        &session_id,
    )
    .await?;

    println!(
        "Subscribed to chat messages for channel: {}",
        user_session.channel
    );

    // Main event loop
    loop {
        tokio::select! {
            _ = &mut shutdown_rx => {
                println!("Shutdown signal received for poll: {}", poll_id);
                break;
            }
            msg = read.next() => {
                match msg {
                    Some(Ok(TungsteniteMessage::Text(text))) => {
                        if let Err(e) = handle_eventsub_message(&state, &poll_id, &text).await {
                            eprintln!("Error handling EventSub message: {}", e);
                        }
                    }
                    Some(Ok(TungsteniteMessage::Ping(data))) => {
                        if write.send(TungsteniteMessage::Pong(data)).await.is_err() {
                            break;
                        }
                    }
                    Some(Ok(TungsteniteMessage::Close(_))) => {
                        println!("EventSub connection closed");
                        break;
                    }
                    Some(Err(e)) => {
                        eprintln!("EventSub WebSocket error: {}", e);
                        break;
                    }
                    None => break,
                    _ => {}
                }
            }
        }
    }

    // Cleanup eventsub connection
    let _ = write.send(TungsteniteMessage::Close(None)).await;
    println!("EventSub listener ended for poll: {}", poll_id);

    Ok(())
}

async fn subscribe_to_chat_messages(
    client_id: &str,
    access_token: &str,
    user_id: &str,
    session_id: &str,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let client = reqwest::Client::new();

    let body = serde_json::json!({
        "type": "channel.chat.message",
        "version": "1",
        "condition": {
            "broadcaster_user_id": user_id,
            "user_id": user_id
        },
        "transport": {
            "method": "websocket",
            "session_id": session_id
        }
    });

    let response = client
        .post("https://api.twitch.tv/helix/eventsub/subscriptions")
        .header("Authorization", format!("Bearer {}", access_token))
        .header("Client-Id", client_id)
        .header("Content-Type", "application/json")
        .json(&body)
        .send()
        .await?;

    let status = response.status();
    let response_text = response.text().await?;
    println!("Subscription response ({status}): {response_text}");

    if !status.is_success() {
        return Err(format!(
            "Failed to subscribe to chat messages for user {}: {}",
            user_id, response_text
        )
        .into());
    }

    Ok(())
}

async fn handle_eventsub_message(
    state: &AppState,
    poll_id: &str,
    text: &str,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let message: EventSubMessage = serde_json::from_str(text)?;

    match message.metadata.message_type.as_str() {
        "notification" => {
            if message.metadata.subscription_type.as_deref() == Some("channel.chat.message") {
                let event: ChatMessageEvent = serde_json::from_value(
                    message.payload.get("event").cloned().unwrap_or_default(),
                )?;

                process_chat_vote(state, poll_id, &event).await;
            }
        }
        "session_keepalive" => {
            // Keepalive, nothing to do
        }
        "session_reconnect" => {
            // TODO: Handle reconnect by connecting to new URL
            println!("Received reconnect request - not yet implemented");
        }
        _ => {
            println!("Received some message: {}", text);
        }
    }

    Ok(())
}

async fn process_chat_vote(state: &AppState, poll_id: &str, event: &ChatMessageEvent) {
    println!(
        "Chat message received: '{}' from user {}",
        event.message.text, event.chatter_user_id
    );
    let vote_text = event.message.text.trim().to_lowercase();

    let mut polls = state.active_polls.write().await;
    let Some(poll) = polls.get_mut(poll_id) else {
        return;
    };

    // Check if user already voted
    if poll.voters.contains(&event.chatter_user_id) {
        println!("User has already voted in this poll");
        return;
    }

    // Try to match vote to an option
    // Support formats: "1", "!vote 1", "!vote option_name", or exact option name
    let matched_option = parse_vote(&vote_text, &poll.config.options);
    println!("Matched option: {:?}", matched_option);
    if let Some(option) = matched_option {
        // Update set of voters and the vote entry count
        poll.voters.insert(event.chatter_user_id.clone());
        *poll.votes.entry(option.clone()).or_insert(0) += 1;

        // Broadcast update
        let update = PollUpdate {
            event_type: "vote".to_string(),
            votes: poll.votes.clone(),
            total_voters: poll.voters.len() as u32,
        };
        let _ = poll.tx.send(update);

        println!("Vote recorded: {} -> {}", event.chatter_user_id, option);
    }
}

fn parse_vote(text: &str, options: &[String]) -> Option<String> {
    let text = text.trim().to_lowercase();

    // Try exact match (case-insensitive)
    for option in options {
        if option.to_lowercase() == text {
            return Some(option.clone());
        }
    }

    // Try "!vote X" format
    let vote_content = text
        .strip_prefix("!vote ")
        .or_else(|| text.strip_prefix("!v "))
        .unwrap_or(&text);

    // Try numeric vote (1-indexed)
    if let Ok(num) = vote_content.parse::<usize>() {
        if num >= 1 && num <= options.len() {
            return Some(options[num - 1].clone());
        }
    }

    // Try partial match at start
    for option in options {
        if option.to_lowercase().starts_with(vote_content) {
            return Some(option.clone());
        }
    }

    None
}