use std::{collections::BTreeSet, fs, path::PathBuf};

use anyhow::Context;

use futures_util::{SinkExt, StreamExt};
use tokio::io::AsyncWriteExt;
use tokio::net::{UnixListener, UnixStream};

use sqlx::prelude::*;
use sqlx::MySqlConnection;

use crate::{
    core::{
        bootstrap::authenticated_unix_socket,
        common::{UnixUser, DEFAULT_SOCKET_PATH},
        protocol::request_response::{
            create_server_to_client_message_stream, Request, Response, ServerToClientMessageStream,
        },
    },
    server::{
        config::{create_mysql_connection_from_config, ServerConfig},
        sql::{
            database_operations::{create_databases, drop_databases, list_databases_for_user},
            database_privilege_operations::{
                apply_privilege_diffs, get_all_database_privileges, get_databases_privilege_data,
            },
            user_operations::{
                create_database_users, drop_database_users, list_all_database_users_for_unix_user,
                list_database_users, lock_database_users, set_password_for_database_user,
                unlock_database_users,
            },
        },
    },
};

// TODO: consider using a connection pool

// TODO: use tracing for login, so we can scope the log messages per incoming connection

pub async fn listen_for_incoming_connections(
    socket_path: Option<PathBuf>,
    config: ServerConfig,
    // db_connection: &mut MySqlConnection,
) -> anyhow::Result<()> {
    let socket_path = socket_path.unwrap_or(PathBuf::from(DEFAULT_SOCKET_PATH));

    let parent_directory = socket_path.parent().unwrap();
    if !parent_directory.exists() {
        println!("Creating directory {:?}", parent_directory);
        fs::create_dir_all(parent_directory)?;
    }

    println!("Listening on {:?}", socket_path);
    match fs::remove_file(socket_path.as_path()) {
        Ok(_) => {}
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {}
        Err(e) => return Err(e.into()),
    }

    let listener = UnixListener::bind(socket_path)?;

    while let Ok((mut conn, _addr)) = listener.accept().await {
        let uid = match authenticated_unix_socket::server_authenticate(&mut conn).await {
            Ok(uid) => uid,
            Err(e) => {
                eprintln!("Failed to authenticate client: {}", e);
                conn.shutdown().await?;
                continue;
            }
        };
        let unix_user = match UnixUser::from_uid(uid.into()) {
            Ok(user) => user,
            Err(e) => {
                eprintln!("Failed to get UnixUser from uid: {}", e);
                conn.shutdown().await?;
                continue;
            }
        };
        match handle_requests_for_single_session(conn, &unix_user, &config).await {
            Ok(_) => {}
            Err(e) => {
                eprintln!("Failed to run server: {}", e);
            }
        }
    }

    Ok(())
}

pub async fn handle_requests_for_single_session(
    socket: UnixStream,
    unix_user: &UnixUser,
    config: &ServerConfig,
) -> anyhow::Result<()> {
    let message_stream = create_server_to_client_message_stream(socket);
    let mut db_connection = create_mysql_connection_from_config(&config.mysql).await?;

    let result = handle_requests_for_single_session_with_db_connection(
        message_stream,
        unix_user,
        &mut db_connection,
    )
    .await;

    if let Err(e) = db_connection
        .close()
        .await
        .context("Failed to close connection properly")
    {
        eprintln!("{}", e);
        eprintln!("Ignoring...");
    }

    result
}

// TODO: ensure proper db_connection hygiene for functions that invoke
//       this function

pub async fn handle_requests_for_single_session_with_db_connection(
    mut stream: ServerToClientMessageStream,
    unix_user: &UnixUser,
    db_connection: &mut MySqlConnection,
) -> anyhow::Result<()> {
    loop {
        // TODO: better error handling
        let request = match stream.next().await {
            Some(Ok(request)) => request,
            Some(Err(e)) => return Err(e.into()),
            None => {
                log::warn!("Client disconnected without sending an exit message");
                break;
            }
        };

        match request {
            Request::CreateDatabases(databases_names) => {
                let result = create_databases(databases_names, unix_user, db_connection).await;
                stream.send(Response::CreateDatabases(result)).await?;
                stream.flush().await?;
            }
            Request::DropDatabases(databases_names) => {
                let result = drop_databases(databases_names, unix_user, db_connection).await;
                stream.send(Response::DropDatabases(result)).await?;
                stream.flush().await?;
            }
            Request::ListDatabases => {
                let result = list_databases_for_user(unix_user, db_connection).await;
                stream.send(Response::ListAllDatabases(result)).await?;
                stream.flush().await?;
            }
            Request::ListPrivileges(database_names) => {
                let response = match database_names {
                    Some(database_names) => {
                        let privilege_data =
                            get_databases_privilege_data(database_names, unix_user, db_connection)
                                .await;
                        Response::ListPrivileges(privilege_data)
                    }
                    None => {
                        let privilege_data =
                            get_all_database_privileges(unix_user, db_connection).await;
                        Response::ListAllPrivileges(privilege_data)
                    }
                };

                stream.send(response).await?;
                stream.flush().await?;
            }
            Request::ModifyPrivileges(database_privilege_diffs) => {
                let result = apply_privilege_diffs(
                    BTreeSet::from_iter(database_privilege_diffs),
                    unix_user,
                    db_connection,
                )
                .await;
                stream.send(Response::ModifyPrivileges(result)).await?;
                stream.flush().await?;
            }
            Request::CreateUsers(db_users) => {
                let result = create_database_users(db_users, unix_user, db_connection).await;
                stream.send(Response::CreateUsers(result)).await?;
                stream.flush().await?;
            }
            Request::DropUsers(db_users) => {
                let result = drop_database_users(db_users, unix_user, db_connection).await;
                stream.send(Response::DropUsers(result)).await?;
                stream.flush().await?;
            }
            Request::PasswdUser(db_user, password) => {
                let result =
                    set_password_for_database_user(&db_user, &password, unix_user, db_connection)
                        .await;
                stream.send(Response::PasswdUser(result)).await?;
                stream.flush().await?;
            }
            Request::ListUsers(db_users) => {
                let response = match db_users {
                    Some(db_users) => {
                        let result = list_database_users(db_users, unix_user, db_connection).await;
                        Response::ListUsers(result)
                    }
                    None => {
                        let result =
                            list_all_database_users_for_unix_user(unix_user, db_connection).await;
                        Response::ListAllUsers(result)
                    }
                };
                stream.send(response).await?;
                stream.flush().await?;
            }
            Request::LockUsers(db_users) => {
                let result = lock_database_users(db_users, unix_user, db_connection).await;
                stream.send(Response::LockUsers(result)).await?;
                stream.flush().await?;
            }
            Request::UnlockUsers(db_users) => {
                let result = unlock_database_users(db_users, unix_user, db_connection).await;
                stream.send(Response::UnlockUsers(result)).await?;
                stream.flush().await?;
            }
            Request::Exit => {
                break;
            }
        }
    }

    Ok(())
}