mod appointment;
mod bot;
mod db;
mod error;
mod schema;

use std::time::Duration;
use std::{env, fs::File, io::BufReader, sync::Arc};

use anyhow::Result;
use async_mutex::Mutex;
use bot::fetch_and_announce_appointment;
use chrono::{DateTime, NaiveDateTime, NaiveTime, TimeZone, Utc};
use chrono_tz::Europe;
use db::ChatInfo;
use diesel::result::Error::NotFound;
use diesel::{Connection, RunQueryDsl, SqliteConnection};
use diesel::{ExpressionMethods, QueryDsl};
use diesel_migrations::{embed_migrations, EmbeddedMigrations, MigrationHarness};
use error::ConfigLoadError;
use log::*;
use serde::{de::Error, Deserialize, Deserializer};
use teloxide::adaptors::Throttle;
use teloxide::prelude::RequesterExt;
use teloxide::requests::Requester;
use teloxide::types::ChatId;
use teloxide::{adaptors::throttle::Limits, Bot};
use tokio::time::sleep;

use crate::db::DbChat;

#[macro_use]
extern crate rust_i18n;

i18n!("locales");

#[derive(Deserialize, Debug)]
pub struct Config {
	token: String,
	data_path: String,
	poll_interval: u64,
	#[serde(deserialize_with = "deserialize_time")]
	reminder_time: NaiveTime,
}

fn deserialize_time<'de, D: Deserializer<'de>>(deserializer: D) -> Result<NaiveTime, D::Error> {
	let s: String = Deserialize::deserialize(deserializer)?;
	NaiveTime::parse_from_str(&s, "%H:%M").map_err(D::Error::custom)
}

impl Config {
	fn load() -> Result<Self, ConfigLoadError> {
		let env_var_name = "CALENDAR_BOT_CONFIG_FILE";
		let default_filename = "./config.yaml";
		let path = env::var(env_var_name).unwrap_or_else(|_| {
			warn!(
				"Cannot read env var '{}', assuming '{}'",
				env_var_name, default_filename
			);
			default_filename.to_owned()
		});
		info!("Reading configuration from {}", path);
		let file = File::open(path).map_err(ConfigLoadError::OpenFailed)?;
		let reader = BufReader::new(file);
		serde_yaml::from_reader(reader).map_err(ConfigLoadError::ReadError)
	}
}

const MIGRATIONS: EmbeddedMigrations = embed_migrations!();

pub type Database = Arc<Mutex<SqliteConnection>>;

#[tokio::main(flavor = "current_thread")]
async fn main() {
	pretty_env_logger::init();
	let config = Config::load().unwrap();
	info!("Connecting to database {}", config.data_path);
	let mut db = SqliteConnection::establish(&config.data_path).unwrap();
	db.run_pending_migrations(MIGRATIONS).unwrap();
	let db = Arc::new(Mutex::new(db));

	let bot = Bot::new(config.token).throttle(Limits::default());

	{
		let db = db.clone();
		let bot = bot.clone();
		let poll_duration = Duration::from_secs(config.poll_interval);
		tokio::task::spawn(async move {
			loop {
				let now = Utc::now();

				let next_appointment = db.lock().await.transaction(|db| {
					use schema::chat::dsl::*;
					chat.select(next_appointment_start)
						.filter(next_appointment_start.is_not_null())
						.filter(next_appointment_start.gt(now.timestamp()))
						.order(next_appointment_start.asc())
						.first::<Option<i64>>(db)
				});

				let next_appointment = match next_appointment {
					Err(NotFound) => None,
					Ok(appointment) => appointment,
					Err(e) => Err(e).unwrap(),
				};

				let sleep_duration = next_appointment
					.map(|timestamp| NaiveDateTime::from_timestamp(timestamp, 0))
					.map(|naive_date_time| DateTime::<Utc>::from_utc(naive_date_time, Utc))
					.map(|date_time| date_time - now)
					.map(|duration| duration.to_std().unwrap())
					.filter(|duration| *duration < poll_duration)
					.unwrap_or(poll_duration);

				sleep(sleep_duration).await;

				// TODO Log the error and continue instead
				check_task(&bot, config.reminder_time, &db).await.unwrap();
			}
		});
	}

	tokio::time::sleep(Duration::from_secs(10)).await;

	bot::spawn(bot, db).await;
}

struct Reminder<Tz: TimeZone> {
	time: DateTime<Tz>,
	text: String,
}

async fn check_task(bot: &Throttle<Bot>, reminder_time: NaiveTime, db: &Database) -> Result<()> {
	let chats = db.lock().await.transaction(|db| {
		use schema::chat::dsl::*;
		chat.load::<DbChat>(db)
	})?;

	let now = Utc::now().with_timezone(&Europe::Berlin);
	let today = now.date_naive();

	for chat in chats {
		let mut chat_info = ChatInfo::from(chat);
		fetch_and_announce_appointment(bot, &mut chat_info, db).await?;

		let appointment = match chat_info.next_appointment {
			Some(appointment) => appointment,
			None => continue,
		};
		let appointment = appointment.with_timezone(&Europe::Berlin);

		if appointment.start.date_naive() != today {
			continue;
		}

		let mut reminder = None;
		if now >= appointment.start {
			reminder = Some(Reminder {
				time: appointment.start,
				text: t!("messages.starting_now", locale = &chat_info.locale),
			});
		} else {
			let reminder_date_time = now.date().and_time(reminder_time).unwrap();
			if now >= reminder_date_time {
				reminder = Some(Reminder {
					time: reminder_date_time,
					text: t!(
						"messages.appointment_today",
						locale = &chat_info.locale,
						start_time = &appointment.start.format("%H:%M").to_string()
					),
				})
			}
		}

		if let Some(reminder) = reminder {
			if chat_info.last_reminder.is_some()
				&& chat_info.last_reminder.unwrap() >= reminder.time
			{
				continue;
			}

			bot.send_message(ChatId(chat_info.id), reminder.text)
				.await?;

			db.lock().await.transaction(|db| {
				use schema::chat::dsl::*;
				diesel::update(chat.filter(telegram_id.eq(chat_info.id)))
					.set((last_reminder.eq(now.timestamp()),))
					.execute(db)
			})?;
		}
	}

	Ok(())
}