use crate::command;

use std::{
	borrow::Cow,
	collections::{
		BTreeMap,
		HashSet,
	},
	num::TryFromIntError,
	sync::{
		Arc,
		Mutex
	},
};

use anyhow::{
	anyhow,
	bail,
	Result,
};
use async_std::task;
use chrono::DateTime;
use frankenstein::{
	client_reqwest::Bot,
	methods::{
		GetUpdatesParams,
		SendMessageParams
	},
	types::{
		AllowedUpdate,
		MessageEntityType,
		User,
	},
	updates::UpdateContent,
	AsyncTelegramApi,
	ParseMode,
};
use sqlx::postgres::PgPoolOptions;
use thiserror::Error;

#[derive(Error, Debug)]
pub enum RssError {
	// #[error(transparent)]
	// Tg(#[from] TgError),
	#[error(transparent)]
	Int(#[from] TryFromIntError),
}

#[derive(Clone)]
pub struct Core {
	owner_chat: i64,
	pub tg: Bot,
	pub me: User,
	pool: sqlx::Pool<sqlx::Postgres>,
	sources: Arc<Mutex<HashSet<Arc<i32>>>>,
	http_client: reqwest::Client,
}

impl Core {
	pub async fn new(settings: config::Config) -> Result<Arc<Core>> {
		let owner_chat = settings.get_int("owner")?;
		let api_key = settings.get_string("api_key")?;
		let tg = Bot::new(&api_key);

		let mut client = reqwest::Client::builder();
		if let Ok(proxy) = settings.get_string("proxy") {
			let proxy = reqwest::Proxy::all(proxy)?;
			client = client.proxy(proxy);
		}
		let http_client = client.build()?;
		let me = tg.get_me().await?;
		let me = me.result;
		let core = Arc::new(Core {
			tg,
			me,
			owner_chat,
			pool: PgPoolOptions::new()
				.max_connections(5)
				.acquire_timeout(std::time::Duration::new(300, 0))
				.idle_timeout(std::time::Duration::new(60, 0))
				.connect_lazy(&settings.get_string("pg")?)?,
			sources: Arc::new(Mutex::new(HashSet::new())),
			http_client,
		});
		let clone = core.clone();
		task::spawn(async move {
			loop {
				let delay = match &clone.autofetch().await {
					Err(err) => {
						if let Err(err) = clone.send(format!("🛑 {err:?}"), None, None).await {
							eprintln!("Autofetch error: {err:?}");
						};
						std::time::Duration::from_secs(60)
					},
					Ok(time) => *time,
				};
				task::sleep(delay).await;
			}
		});
		Ok(core)
	}

	pub async fn stream(&self) -> Result<()> {
		let mut offset: i64 = 0;
		let mut params = GetUpdatesParams {
			offset: None,
			limit: Some(100),
			timeout: Some(300),
			allowed_updates: Some(vec![AllowedUpdate::Message]),
		};
		loop {
			let updates = self.tg.get_updates(&params).await?.result;
			if updates.is_empty() {
				offset = 0;
				params.offset = None;
				continue;
			}
			for update in updates {
				if i64::from(update.update_id) >= offset {
					offset = i64::from(update.update_id) + 1;
					params.offset = Some(offset);
				}
				if let UpdateContent::Message(msg) = update.content {
					if let Some(text) = msg.text {
						if let Some(entities) = msg.entities {
							let chars: Vec<u16> = text.encode_utf16().collect();
							for entity in entities {
								if entity.type_field == MessageEntityType::BotCommand && entity.offset != 0 {
									bail!("commands should be at message start");
								};
								let cmd = String::from_utf16_lossy(&chars[entity.offset as usize..entity.length as usize]);
								let words: Vec<&str> = text.split_whitespace().collect();
								match cmd.as_ref() {
									"/check" | "/clean" | "/enable" | "/delete" | "/disable" => { command::command(self, msg.chat.id, words).await? },
									"/start" => { command::start(self, msg.chat.id).await?; },
									"/list" => { command::list(self, msg.chat.id).await?; },
									"/add" | "/update" => { command::update(self, msg.chat.id, words).await?; },
									any => {
										self.send(format!("\\#error\n```\nUnknown command: {any}\n```"),
											Some(msg.chat.id),
											Some(ParseMode::MarkdownV2)
										).await?;
									},
								};
							};
						};
					};
				};
			}
		}
	}

	pub async fn send <S>(&self, msg: S, target: Option<i64>, mode: Option<ParseMode>) -> Result<()>
	where S: Into<String> {
		let msg = msg.into();

		let mode = mode.unwrap_or(ParseMode::Html);
		let target = target.unwrap_or(self.owner_chat);
		let send = SendMessageParams::builder()
			.chat_id(target)
			.text(msg)
			.parse_mode(mode)
			.build();
		self.tg.send_message(&send).await?;
		Ok(())
	}

	pub async fn check (&self, id: &i32, owner: i64, real: bool) -> Result<Cow<'_, str>> {
		let mut posted: i32 = 0;
		let mut conn = self.pool.acquire().await?;

		let id = {
			let mut set = self.sources.lock().unwrap();
			match set.get(id) {
				Some(id) => id.clone(),
				None => {
					let id = Arc::new(*id);
					set.insert(id.clone());
					id.clone()
				},
			}
		};
		let count = Arc::strong_count(&id);
		if count == 2 {
			let source = sqlx::query!("select source_id, channel_id, url, iv_hash, owner, url_re from rsstg_source where source_id = $1 and owner = $2",
				*id, owner).fetch_one(&mut *conn).await?;
			let destination = match real {
				true => source.channel_id,
				false => source.owner,
			};
			let mut this_fetch: Option<DateTime<chrono::FixedOffset>> = None;
			let mut posts: BTreeMap<DateTime<chrono::FixedOffset>, String> = BTreeMap::new();

			let response = self.http_client.get(&source.url).send().await?;
			let status = response.status();
			let content = response.bytes().await?;
			match rss::Channel::read_from(&content[..]) {
				Ok(feed) => {
					for item in feed.items() {
						if let Some(link) = item.link() {
							let date = match item.pub_date() {
								Some(feed_date) => DateTime::parse_from_rfc2822(feed_date),
								None => DateTime::parse_from_rfc3339(&item.dublin_core_ext().unwrap().dates()[0]),
							}?;
							let url = link;
							posts.insert(date, url.to_string());
						}
					};
				},
				Err(err) => match err {
					rss::Error::InvalidStartTag => {
						match atom_syndication::Feed::read_from(&content[..]) {
							Ok(feed) => {
								for item in feed.entries() {
									let date = item.published().unwrap();
									let url = item.links()[0].href();
									posts.insert(*date, url.to_string());
								};
							},
							Err(err) => {
								bail!("Unsupported or mangled content:\n{:?}\n{err:#?}\n{status:#?}\n", &source.url)
							},
						}
					},
					rss::Error::Eof => (),
					_ => bail!("Unsupported or mangled content:\n{:?}\n{err:#?}\n{status:#?}\n", &source.url)
				}
			};
			for (date, url) in posts.iter() {
				let post_url: Cow<str> = match source.url_re {
					Some(ref x) => sedregex::ReplaceCommand::new(x)?.execute(url),
					None => url.into(),
				};
				if let Some(exists) = sqlx::query!("select exists(select true from rsstg_post where url = $1 and source_id = $2) as exists;",
					&post_url, *id).fetch_one(&mut *conn).await?.exists {
					if ! exists {
						if this_fetch.is_none() || *date > this_fetch.unwrap() {
							this_fetch = Some(*date);
						};
						self.send( match &source.iv_hash {
							Some(hash) => format!("<a href=\"https://t.me/iv?url={post_url}&rhash={hash}\"> </a>{post_url}"),
							None => format!("{post_url}"),
						}, Some(destination), Some(ParseMode::Html)).await?;
						sqlx::query!("insert into rsstg_post (source_id, posted, url) values ($1, $2, $3);",
							*id, date, &post_url).execute(&mut *conn).await?;
					};
				};
				posted += 1;
			};
			posts.clear();
		};
		sqlx::query!("update rsstg_source set last_scrape = now() where source_id = $1;",
			*id).execute(&mut *conn).await?;
		Ok(format!("Posted: {posted}").into())
	}

	pub async fn delete (&self, source_id: &i32, owner: i64) -> Result<Cow<'_, str>> {
		match sqlx::query!("delete from rsstg_source where source_id = $1 and owner = $2;",
			source_id, owner).execute(&mut *self.pool.acquire().await?).await?.rows_affected() {
			0 => { Ok("No data found found.".into()) },
			x => { Ok(format!("{} sources removed.", x).into()) },
		}
	}

	pub async fn clean (&self, source_id: &i32, owner: i64) -> Result<Cow<'_, str>> {
		match sqlx::query!("delete from rsstg_post p using rsstg_source s where p.source_id = $1 and owner = $2 and p.source_id = s.source_id;",
			source_id, owner).execute(&mut *self.pool.acquire().await?).await?.rows_affected() {
			0 => { Ok("No data found found.".into()) },
			x => { Ok(format!("{x} posts purged.").into()) },
		}
	}

	pub async fn enable (&self, source_id: &i32, owner: i64) -> Result<&str> {
		match sqlx::query!("update rsstg_source set enabled = true where source_id = $1 and owner = $2",
			source_id, owner).execute(&mut *self.pool.acquire().await?).await?.rows_affected() {
			1 => { Ok("Source enabled.") },
			0 => { Ok("Source not found.") },
			_ => { Err(anyhow!("Database error.")) },
		}
	}

	pub async fn disable (&self, source_id: &i32, owner: i64) -> Result<&str> {
		match sqlx::query!("update rsstg_source set enabled = false where source_id = $1 and owner = $2",
			source_id, owner).execute(&mut *self.pool.acquire().await?).await?.rows_affected() {
			1 => { Ok("Source disabled.") },
			0 => { Ok("Source not found.") },
			_ => { Err(anyhow!("Database error.")) },
		}
	}

	pub async fn update (&self, update: Option<i32>, channel: &str, channel_id: i64, url: &str, iv_hash: Option<&str>, url_re: Option<&str>, owner: i64) -> Result<&str> {
		let mut conn = self.pool.acquire().await?;

		match match update {
				Some(id) => {
					sqlx::query!("update rsstg_source set channel_id = $2, url = $3, iv_hash = $4, owner = $5, channel = $6, url_re = $7 where source_id = $1",
						id, channel_id, url, iv_hash, owner, channel, url_re).execute(&mut *conn).await
				},
				None => {
					sqlx::query!("insert into rsstg_source (channel_id, url, iv_hash, owner, channel, url_re) values ($1, $2, $3, $4, $5, $6)",
						channel_id, url, iv_hash, owner, channel, url_re).execute(&mut *conn).await
				},
			} {
			Ok(_) => Ok(match update {
				Some(_) => "Channel updated.",
				None => "Channel added.",
			}),
			Err(sqlx::Error::Database(err)) => {
				match err.downcast::<sqlx::postgres::PgDatabaseError>().routine() {
					Some("_bt_check_unique", ) => {
						Ok("Duplicate key.")
					},
					Some(_) => {
						Ok("Database error.")
					},
					None => {
						Ok("No database error extracted.")
					},
				}
			},
			Err(err) => {
				bail!("Sorry, unknown error:\n{err:#?}\n");
			},
		}
	}

	async fn autofetch(&self) -> Result<std::time::Duration> {
		let mut delay = chrono::Duration::minutes(1);
		let now = chrono::Local::now();
		let mut queue = sqlx::query!(r#"select source_id, next_fetch as "next_fetch: DateTime<chrono::Local>", owner from rsstg_order natural left join rsstg_source where next_fetch < now() + interval '1 minute';"#)
			.fetch_all(&mut *self.pool.acquire().await?).await?;
		for row in queue.iter() {
			if let Some(next_fetch) = row.next_fetch {
				if next_fetch < now {
					if let (Some(owner), Some(source_id)) = (row.owner, row.source_id) {
						let clone = Core {
							owner_chat: owner,
							..self.clone()
						};
						task::spawn(async move {
							if let Err(err) = clone.check(&source_id, owner, true).await {
								if let Err(err) = clone.send(&format!("🛑 {err:?}"), None, None).await {
									eprintln!("Check error: {err:?}");
									// clone.disable(&source_id, owner).await.unwrap();
								};
							};
						});
					}
				} else if next_fetch - now < delay {
					delay = next_fetch - now;
				}
			}
		};
		queue.clear();
		Ok(delay.to_std()?)
	}

	pub async fn list (&self, owner: i64) -> Result<String> {
		let mut reply: Vec<Cow<str>> = vec![];
		reply.push("Channels:".into());
		let rows = sqlx::query!("select source_id, channel, enabled, url, iv_hash, url_re from rsstg_source where owner = $1 order by source_id",
			owner).fetch_all(&mut *self.pool.acquire().await?).await?;
		for row in rows.iter() {
			reply.push(format!("\n\\#️⃣ {} \\*️⃣ `{}` {}\n🔗 `{}`", row.source_id, row.channel,
				match row.enabled {
					true  => "🔄 enabled",
					false => "⛔ disabled",
				}, row.url).into());
			if let Some(hash) = &row.iv_hash {
				reply.push(format!("IV: `{hash}`").into());
			}
			if let Some(re) = &row.url_re {
				reply.push(format!("RE: `{re}`").into());
			}
		};
		Ok(reply.join("\n"))
	}
}
