use anyhow::Context;
use axum::{
    extract::{
        Path, State,
        ws::{Message, WebSocket, WebSocketUpgrade},
    },
    response::Response,
};
use futures::stream::StreamExt;
use log::{debug, info};
use serde::Deserialize;

use crate::{
    app_state::{
        AppState,
        database::models::VaultId,
        websocket::{
            models::{
                CursorPositionFromServer, WebSocketClientMessage, WebSocketServerMessage,
                WebSocketVaultUpdate,
            },
            utils::{
                get_authenticated_handshake, get_unseen_documents, send_update_over_websocket,
            },
        },
    },
    errors::{SyncServerError, client_error, server_error},
    utils::normalize::normalize,
};

#[derive(Deserialize)]
pub struct WebSocketPathParams {
    #[serde(deserialize_with = "normalize")]
    vault_id: VaultId,
}

pub async fn websocket_handler(
    ws: WebSocketUpgrade,
    Path(WebSocketPathParams { vault_id }): Path<WebSocketPathParams>,
    State(state): State<AppState>,
) -> Result<Response, SyncServerError> {
    Ok(ws.on_upgrade(move |socket| websocket_wrapped(state, socket, vault_id)))
}

async fn websocket_wrapped(state: AppState, stream: WebSocket, vault_id: VaultId) {
    info!("WebSocket connection opened on vault '{vault_id}'");

    let result = websocket(state, stream, vault_id.clone()).await;

    if let Err(err) = result {
        debug!("WebSocket connection error on vault '{vault_id}': {err}");
    }
}

#[allow(clippy::too_many_lines)]
async fn websocket(
    state: AppState,
    stream: WebSocket,
    vault_id: VaultId,
) -> Result<(), SyncServerError> {
    let (mut sender, mut websocket_receiver) = stream.split();

    let authed_handshake = get_authenticated_handshake(
        &state,
        &vault_id,
        websocket_receiver
            .next()
            .await
            .transpose()
            .unwrap_or_default(),
    )?;

    info!(
        "WebSocket handshake successful for vault '{vault_id}' for '{}'",
        authed_handshake.handshake.device_id
    );

    let mut broadcast_receiver = state.broadcasts.get_receiver(vault_id.clone()).await;

    send_update_over_websocket(
        &WebSocketServerMessage::VaultUpdate(WebSocketVaultUpdate {
            documents: get_unseen_documents(
                &state,
                &vault_id,
                authed_handshake.handshake.last_seen_vault_update_id,
            )
            .await?,
            is_initial_sync: true,
        }),
        &mut sender,
    )
    .await?;

    send_update_over_websocket(
        &WebSocketServerMessage::CursorPositions(CursorPositionFromServer {
            clients: state.cursors.get_cursors(&vault_id).await,
        }),
        &mut sender,
    )
    .await?;

    let device_id = authed_handshake.handshake.device_id.clone();
    let mut send_task = tokio::spawn(async move {
        while let Ok(update) = broadcast_receiver.recv().await {
            if Some(&device_id) == update.origin_device_id.as_ref() {
                continue;
            }

            send_update_over_websocket(&update.message, &mut sender).await?;
        }

        Ok::<(), SyncServerError>(())
    });

    let device_id = authed_handshake.handshake.device_id.clone();
    let vault_id_clone = vault_id.clone();
    let cursor_manager = state.cursors.clone();
    let mut receive_task = tokio::spawn(async move {
        while let Some(Ok(Message::Text(message))) = websocket_receiver.next().await {
            let message: WebSocketClientMessage = serde_json::from_str(&message)
                .context("Failed to parse WebSocket message from client")
                .map_err(server_error)?;

            match message {
                WebSocketClientMessage::Handshake(_) => {
                    return Err(client_error(anyhow::anyhow!(
                        "Unexpected handshake message"
                    )));
                }
                WebSocketClientMessage::CursorPositions(cursors) => {
                    cursor_manager
                        .update_cursors(
                            vault_id_clone.clone(),
                            authed_handshake.user.name.clone(),
                            &device_id,
                            cursors.documents_with_cursors,
                        )
                        .await;
                }
            }
        }

        Ok::<(), SyncServerError>(())
    });

    tokio::select! {
        _ = &mut send_task => receive_task.abort(),
        _ = &mut receive_task => send_task.abort(),
    };

    let result: Result<(), SyncServerError> = (async {
        send_task
            .await
            .context("WebSocket send task failed")
            .map_err(client_error)
            .and_then(|err| err)?;

        receive_task
            .await
            .context("WebSocket receive task failed")
            .map_err(client_error)
            .and_then(|err| err)?;

        Ok(())
    })
    .await;

    state
        .cursors
        .remove_cursors_of_device(&vault_id, &authed_handshake.handshake.device_id)
        .await;

    if result.is_err() {
        info!(
            "WebSocket disconnected on vault '{vault_id}' for '{}'",
            authed_handshake.handshake.device_id
        );
    }

    result
}