use chrono::{DateTime, Local};
use chrono::{Datelike, Month, NaiveDate, NaiveDateTime, NaiveTime, TimeZone};
use futures_util::FutureExt;
use futures_util::StreamExt;
use std::collections::HashSet;
use std::net::SocketAddr;
use std::str::FromStr;
use std::sync::Arc;
use structopt::StructOpt;
use tokio::net::{TcpListener, TcpStream};
use tokio_postgres::{Client, Config, NoTls, Statement};

type Error = Box<dyn std::error::Error>;

/// This application recieves logfiles in ubiquitis weird logfile format from the network,
/// splits each line into its fields and writes them to a sql database for further analysis.
///
/// The main required argument is an postgres connection string, passed in the environment
/// variable LOG2DB_PSQL
#[derive(StructOpt)]
struct Options {
    /// ip and (TCP) port to bind to
    #[structopt(short, long, default_value = "[::]:514")]
    addr: String,
    /// space separated list of daemon/service names to not write to the db
    #[structopt(default_value = "dnsmasq-dhcp")]
    blacklist: Vec<String>,
}

#[tokio::main(flavor = "current_thread")]
async fn main() -> Result<(), Error> {
    let options = Options::from_args();

    let postgresurl = std::env::var("LOG2DB_PSQL")
        .map_err(|_| "please supply the LOG2DB_PSQL environment variable, containting a postgress connection string")?;

    let mut cfg = Config::from_str(&postgresurl)?;
    cfg.application_name("log2db");
    let (client, connection) = cfg.connect(NoTls).await?;

    let connection = connection.map(|r| {
        if let Err(e) = r {
            eprintln!("could not connect to database: {}", e);
        }
    });
    tokio::spawn(connection);

    client
        .execute(
            "create table if not exists log(
                prio smallint,
                rcv_ip inet,
                rcv_date timestamptz,
                date timestamptz,
                daemon varchar,
                message varchar
            )
            ",
            &[],
        )
        .await?;

    let client = Arc::new(client);

    let insert_statement = client
        .prepare("insert into log(prio, rcv_ip, rcv_date, date, daemon, message) values ($1, $2, $3, $4, $5, $6)").await?;

    let listener = TcpListener::bind(&options.addr)
        .await
        .map_err(|e| format!("could not bind to {} with error {:?}", &options.addr, e))?;

    let blacklist: HashSet<_> = options.blacklist.into_iter().collect();
    let blacklist = Arc::new(blacklist);

    loop {
        match listener.accept().await {
            Ok((socket, peer)) => {
                tokio::spawn(handle_peer_and_error(
                    socket,
                    peer,
                    client.clone(),
                    insert_statement.clone(),
                    blacklist.clone(),
                ));
            }
            Err(e) => eprintln!("{:?}", e),
        }
    }
}

async fn handle_peer_and_error(
    stream: TcpStream,
    peer: SocketAddr,
    db: Arc<Client>,
    insert_statement: Statement,
    blacklist: Arc<HashSet<String>>,
) {
    if let Err(e) = handle_peer(stream, peer, db, insert_statement, blacklist).await {
        eprintln!("{}", e);
    }
}

async fn handle_peer(
    stream: TcpStream,
    peer: SocketAddr,
    db: Arc<Client>,
    insert_statement: Statement,
    blacklist: Arc<HashSet<String>>,
) -> Result<(), Error> {
    use tokio_util::codec::{FramedRead, LinesCodec};

    let ip = peer.ip();

    let mut lines = FramedRead::new(stream, LinesCodec::new());
    while let Some(line) = lines.next().await.transpose()? {
        let ParsedLine {
            prio,
            rcvtime,
            logtime,
            service,
            entry,
        } = parse_line(&line)?;
        if !blacklist.contains(service) {
            db.execute(
                &insert_statement,
                &[&prio, &ip, &rcvtime, &logtime, &service, &entry],
            )
            .await?;
        }
    }
    Ok(())
}

struct ParsedLine<'a> {
    prio: i16,
    rcvtime: DateTime<Local>,
    logtime: DateTime<Local>,
    // maybe this would be more correct, but i don't want to redo the database rn
    //logtime: NaiveDateTime,
    service: &'a str,
    entry: &'a str,
}
#[test]
fn tst_timeparse() {
    let input = "Jul  8 01:20:30";
    let year = 2022;
    let parsed = parse_log_date(year, input).unwrap();
    assert_eq!(
        parsed,
        NaiveDateTime::parse_from_str("2022-07-08 01:20:30", "%Y-%m-%d %H:%M:%S").unwrap()
    )
}

fn parse_log_date(year: i32, input: &'_ str) -> Result<NaiveDateTime, Error> {
    let mut parts = input.split(" ").map(|p| p.trim()).filter(|p| p.len() > 0);
    let month = Month::from_str(parts.next().ok_or("no month")?)
        .map_err(|e| format!("month parsing error: {:?}", e))?;
    let day: u32 = parts.next().ok_or("no day")?.parse()?;
    let date =
        NaiveDate::from_ymd_opt(year, month.number_from_month(), day).ok_or("invalid day+moth")?;
    let time = NaiveTime::parse_from_str(parts.next().ok_or("no time")?, "%H:%M:%S")?;
    Ok(NaiveDateTime::new(date, time))
}

fn parse_line(line: &'_ str) -> Result<ParsedLine<'_>, Error> {
    let mut prio_and_remainder = line.splitn(2, '>');
    let prio = prio_and_remainder
        .next()
        .ok_or("log did not contain priority")?;
    let prio = &prio[1..];
    let prio = prio
        .parse()
        .map_err(|e| format!("could not parse priority {}: {}", prio, e))?;

    let line = prio_and_remainder
        .next()
        .expect("splitn should always return a second part");
    let (date, line) = line.split_at(16);

    let rcvtime = chrono::Local::now();
    // we need to prepend the current year and add timezone, as that is not stated in the logfile
    let logtime = parse_log_date(rcvtime.date_naive().year(), date)
        .map_err(|e| format!("could not parse logtime {}{} {}", date, line, e))?;
    let logtime = TimeZone::from_local_datetime(&Local, &logtime).unwrap();

    let mut parts = line.splitn(2, ':');

    let service_and_pid = parts.next().ok_or("could not parse service")?;
    let mut service_parts = service_and_pid.splitn(2, '[');
    let service = service_parts
        .next()
        .ok_or("could not split pid from service")?
        .trim();

    let entry = parts.next().ok_or("could not parse logfile")?.trim();
    Ok(ParsedLine {
        prio,
        rcvtime,
        logtime,
        service,
        entry,
    })
}