use std::sync::Arc;

use fabro_interview::WebInterviewer;
use futures_util::{SinkExt, StreamExt};
use tokio::time::sleep;
use tokio_tungstenite::tungstenite::Message;
use tracing::{debug, error, info, warn};

use crate::client::{SlackApiError, SlackClient, parse_wss_url};
use crate::dispatch::{DispatchAction, dispatch};
use crate::socket::{SocketAck, SocketEnvelope};
use crate::threads::ThreadRegistry;

#[derive(Debug, thiserror::Error)]
pub enum ConnectionError {
    #[error("WebSocket error: {0}")]
    WebSocket(String),
    #[error("Protocol error: {0}")]
    Protocol(String),
    #[error("API error: {0}")]
    Api(#[from] SlackApiError),
}

#[derive(Debug, PartialEq, Eq)]
pub enum ProcessOutcome {
    Continue,
    Reconnect,
    Closed,
}

/// Process a single raw WebSocket text message: parse, ack, dispatch.
pub fn process_message(
    text: &str,
    thread_registry: &ThreadRegistry,
) -> (Option<String>, ProcessOutcome, DispatchAction) {
    let envelope: SocketEnvelope = if let Ok(e) = serde_json::from_str(text) {
        e
    } else {
        warn!("Failed to parse WebSocket message as envelope");
        return (None, ProcessOutcome::Continue, DispatchAction::Ignored);
    };

    let ack_json = envelope
        .envelope_id
        .as_deref()
        .map(|id| serde_json::to_string(&SocketAck::new(id)).expect("ack serialization"));

    let action = dispatch(&envelope, thread_registry);

    let outcome = match &action {
        DispatchAction::Reconnect => ProcessOutcome::Reconnect,
        _ => ProcessOutcome::Continue,
    };

    (ack_json, outcome, action)
}

/// Fetch a WebSocket URL from Slack's `apps.connections.open` endpoint.
pub async fn open_socket_url(
    http: &reqwest::Client,
    app_token: &str,
) -> Result<String, ConnectionError> {
    let resp = http
        .post("https://slack.com/api/apps.connections.open")
        .bearer_auth(app_token)
        .header("Content-Type", "application/x-www-form-urlencoded")
        .send()
        .await
        .map_err(|e| ConnectionError::WebSocket(e.to_string()))?;

    let json: serde_json::Value = resp
        .json()
        .await
        .map_err(|e| ConnectionError::WebSocket(e.to_string()))?;

    parse_wss_url(&json).map_err(ConnectionError::Api)
}

/// Run the Socket Mode event loop. Connects, reads messages, acks, dispatches.
/// On disconnect, returns so the caller can reconnect.
pub async fn run_event_loop(
    wss_url: &str,
    interviewer: &Arc<WebInterviewer>,
    thread_registry: &ThreadRegistry,
) -> Result<(), ConnectionError> {
    let (ws_stream, _) = tokio_tungstenite::connect_async(wss_url)
        .await
        .map_err(|e| ConnectionError::WebSocket(e.to_string()))?;

    let (mut write, mut read) = ws_stream.split();
    info!("Socket Mode WebSocket connected");

    while let Some(msg) = read.next().await {
        let msg = match msg {
            Ok(m) => m,
            Err(e) => {
                error!("WebSocket read error: {e}");
                return Err(ConnectionError::WebSocket(e.to_string()));
            }
        };

        let text = match msg {
            Message::Text(t) => t,
            Message::Close(_) => {
                info!("WebSocket closed by server");
                return Ok(());
            }
            Message::Ping(data) => {
                let _ = write.send(Message::Pong(data)).await;
                continue;
            }
            _ => continue,
        };

        let (ack_json, outcome, action) = process_message(&text, thread_registry);

        // Send ack immediately (Slack requires within 3 seconds)
        if let Some(ack) = ack_json {
            if let Err(e) = write.send(Message::Text(ack.into())).await {
                error!("Failed to send ack: {e}");
            }
        }

        // Handle dispatch action
        match action {
            DispatchAction::SubmitAnswer {
                question_id,
                answer,
            } => {
                debug!(question_id, "Submitting answer from Slack");
                let _ = interviewer.submit_answer(&question_id, answer);
            }
            DispatchAction::Connected => {
                info!("Socket Mode handshake complete");
            }
            DispatchAction::Reconnect | DispatchAction::Ignored => {}
        }

        if outcome == ProcessOutcome::Reconnect {
            info!("Server requested disconnect, will reconnect");
            return Ok(());
        }
    }

    info!("WebSocket stream ended");
    Ok(())
}

/// Top-level runner: connects, runs the event loop, and reconnects on disconnect.
pub async fn run(
    slack_client: &SlackClient,
    app_token: &str,
    interviewer: Arc<WebInterviewer>,
    thread_registry: &ThreadRegistry,
) {
    let mut backoff = std::time::Duration::from_secs(1);
    let max_backoff = std::time::Duration::from_secs(30);

    loop {
        let wss_url = match open_socket_url(slack_client.http(), app_token).await {
            Ok(url) => {
                backoff = std::time::Duration::from_secs(1);
                url
            }
            Err(e) => {
                error!("Failed to open Socket Mode connection: {e}");
                sleep(backoff).await;
                backoff = (backoff * 2).min(max_backoff);
                continue;
            }
        };

        match run_event_loop(&wss_url, &interviewer, thread_registry).await {
            Ok(()) => {
                info!("Event loop ended, reconnecting...");
                backoff = std::time::Duration::from_secs(1);
            }
            Err(e) => {
                error!("Event loop error: {e}, reconnecting...");
                sleep(backoff).await;
                backoff = (backoff * 2).min(max_backoff);
            }
        }
    }
}

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

    fn registry() -> ThreadRegistry {
        ThreadRegistry::new()
    }

    #[test]
    fn process_hello_message() {
        let text = r#"{"type":"hello","num_connections":1}"#;
        let (ack, outcome, action) = process_message(text, &registry());
        assert!(ack.is_none());
        assert_eq!(outcome, ProcessOutcome::Continue);
        assert!(matches!(action, DispatchAction::Connected));
    }

    #[test]
    fn process_interactive_message_acks_and_dispatches() {
        let text = r#"{
            "type": "interactive",
            "envelope_id": "env-1",
            "payload": {
                "type": "block_actions",
                "actions": [{
                    "action_id": "q-1:yes",
                    "type": "button",
                    "value": "yes"
                }]
            }
        }"#;
        let (ack, outcome, action) = process_message(text, &registry());
        assert!(ack.is_some());
        assert!(ack.unwrap().contains("env-1"));
        assert_eq!(outcome, ProcessOutcome::Continue);
        match action {
            DispatchAction::SubmitAnswer {
                question_id,
                answer,
            } => {
                assert_eq!(question_id, "q-1");
                assert_eq!(answer.value, AnswerValue::Yes);
            }
            other => panic!("expected SubmitAnswer, got {other:?}"),
        }
    }

    #[test]
    fn process_disconnect_signals_reconnect() {
        let text = r#"{"type":"disconnect","reason":"link_disabled"}"#;
        let (ack, outcome, action) = process_message(text, &registry());
        assert!(ack.is_none());
        assert_eq!(outcome, ProcessOutcome::Reconnect);
        assert!(matches!(action, DispatchAction::Reconnect));
    }

    #[test]
    fn process_invalid_json_is_ignored() {
        let text = "not valid json {{{";
        let (ack, outcome, action) = process_message(text, &registry());
        assert!(ack.is_none());
        assert_eq!(outcome, ProcessOutcome::Continue);
        assert!(matches!(action, DispatchAction::Ignored));
    }

    #[test]
    fn process_events_api_acks_but_ignores() {
        let text = r#"{
            "type": "events_api",
            "envelope_id": "env-99",
            "payload": {
                "event": { "type": "app_mention", "text": "hi" }
            }
        }"#;
        let (ack, outcome, action) = process_message(text, &registry());
        assert!(ack.is_some());
        assert!(ack.unwrap().contains("env-99"));
        assert_eq!(outcome, ProcessOutcome::Continue);
        assert!(matches!(action, DispatchAction::Ignored));
    }

    #[test]
    fn process_thread_reply_with_registered_question() {
        let reg = registry();
        reg.register("1234.5678", "q-10");
        let text = serde_json::json!({
            "type": "events_api",
            "envelope_id": "env-50",
            "payload": {
                "event": {
                    "type": "message",
                    "text": "my answer",
                    "thread_ts": "1234.5678",
                    "user": "U123"
                }
            }
        })
        .to_string();
        let (ack, outcome, action) = process_message(&text, &reg);
        assert!(ack.is_some());
        assert_eq!(outcome, ProcessOutcome::Continue);
        match action {
            DispatchAction::SubmitAnswer {
                question_id,
                answer,
            } => {
                assert_eq!(question_id, "q-10");
                assert_eq!(answer.value, AnswerValue::Text("my answer".to_string()));
            }
            other => panic!("expected SubmitAnswer, got {other:?}"),
        }
    }

    #[tokio::test]
    async fn submit_answer_reaches_web_interviewer() {
        let interviewer = Arc::new(WebInterviewer::new());
        let i_clone = Arc::clone(&interviewer);

        let handle = tokio::spawn(async move {
            use fabro_interview::{Interviewer, Question, QuestionType};
            let q = Question::new("approve?", QuestionType::YesNo);
            i_clone.ask(q).await
        });

        tokio::time::sleep(std::time::Duration::from_millis(50)).await;

        let pending = interviewer.pending_questions();
        assert_eq!(pending.len(), 1);

        let question_id = pending[0].id.clone();
        let text = serde_json::json!({
            "type": "interactive",
            "envelope_id": "e1",
            "payload": {
                "type": "block_actions",
                "actions": [{
                    "action_id": format!("{question_id}:yes"),
                    "type": "button",
                    "value": "yes"
                }]
            }
        })
        .to_string();
        let (_, _, action) = process_message(&text, &registry());
        match action {
            DispatchAction::SubmitAnswer {
                question_id: qid,
                answer,
            } => {
                assert!(interviewer.submit_answer(&qid, answer));
            }
            other => panic!("expected SubmitAnswer, got {other:?}"),
        }

        let answer = handle.await.unwrap();
        assert_eq!(answer.value, AnswerValue::Yes);
    }
}