use std::{
	cmp::{min, max},
	collections::*,
	convert::{Infallible, TryInto},
	error::Error,
	io::SeekFrom,
	path::PathBuf,
	sync::Arc,
	time::Duration,
};

use hyper::{
	StatusCode,
	Uri,
};
use lazy_static::*;
use regex::Regex;
use reqwest::{
	Body,
	Client,
};
use tokio::{
	fs::File,
	io::AsyncReadExt,
	sync::mpsc::{
		channel,
	},
	time::delay_for,
};

use ptth::http_serde;

fn parse_range_header (range_str: &str) -> (Option <u64>, Option <u64>) {
	lazy_static! {
		static ref RE: Regex = Regex::new (r"^bytes=(\d*)-(\d*)$").expect ("Couldn't compile regex for Range header");
	}
	
	println! ("{}", range_str);
	
	let caps = match RE.captures (range_str) {
		Some (x) => x,
		_ => return (None, None),
	};
	let start = caps.get (1).map (|x| x.as_str ());
	let end = caps.get (2).map (|x| x.as_str ());
	
	let start = start.map (|x| u64::from_str_radix (x, 10).ok ()).flatten ();
	let end = end.map (|x| u64::from_str_radix (x, 10).ok ()).flatten ();
	
	(start, end)
}

async fn serve_file (
	client: Arc <Client>, 
	mut f: File,
	req_id: String,
	should_send_body: bool,
	range_start: Option <u64>,
	range_end: Option <u64>
) {
	let (tx, rx) = channel (2);
	let body = if should_send_body {
		Some (Body::wrap_stream (rx))
	}
	else {
		None
	};
	
	let file_md = f.metadata ().await.unwrap ();
	let file_len = file_md.len ();
	
	let start = range_start.unwrap_or (0);
	let end = range_end.unwrap_or (file_len);
	
	let start = max (0, min (start, file_len));
	let end = max (0, min (end, file_len));
	
	f.seek (SeekFrom::Start (start)).await.unwrap ();
	
	println! ("Serving range {}-{}", start, end);
	
	if should_send_body {
	tokio::spawn (async move {
		//println! ("Opening file {:?}", path);
		
		let mut tx = tx;
		//let mut bytes_sent = 0;
		let mut bytes_left = end - start;
		
		loop {
			let mut buffer = vec! [0u8; 65_536];
			let bytes_read: u64 = f.read (&mut buffer).await.unwrap ().try_into ().unwrap ();
			
			let bytes_read = min (bytes_left, bytes_read);
			
			buffer.truncate (bytes_read.try_into ().unwrap ());
			
			if bytes_read == 0 {
				break;
			}
			
			if tx.send (Ok::<_, Infallible> (buffer)).await.is_err () {
				break;
			}
			
			bytes_left -= bytes_read;
			if bytes_left == 0 {
				break;
			}
			
			//bytes_sent += bytes_read;
			//println! ("Sent {} bytes", bytes_sent);
			
			delay_for (Duration::from_millis (50)).await;
		}
	});
	}
	
	let mut headers: HashMap <String, Vec <u8>> = Default::default ();
	headers.insert (String::from ("accept-ranges"), b"bytes".to_vec ());
	
	let status_code;
	
	if range_start.is_none () && range_end.is_none () {
		headers.insert (String::from ("content-length"), end.to_string ().into_bytes ());
		status_code = http_serde::StatusCode::Ok;
	}
	else {
		headers.insert (String::from ("content-range"), format! ("bytes {}-{}/{}", start, end - 1, end).into_bytes ());
		status_code = http_serde::StatusCode::PartialContent;
	}
	
	let resp_parts = http_serde::ResponseParts {
		status_code,
		headers,
	};
	
	let mut resp_req = client
	.post (&format! ("http://127.0.0.1:4000/http_response/{}", req_id))
	.header ("X-PTTH-2LJYXWC4", base64::encode (rmp_serde::to_vec (&resp_parts).unwrap ()));
	
	if let Some (body) = body {
		resp_req = resp_req.body (body);
	}
	
	//println! ("Step 6");
	if let Err (e) = resp_req.send ().await {
		println! ("Err: {:?}", e);
	}
}

#[tokio::main]
async fn main () -> Result <(), Box <dyn Error>> {
	let client = Arc::new (Client::new ());
	
	let mut backoff_delay = 0;
	
	loop {
		if backoff_delay > 0 {
			delay_for (Duration::from_millis (backoff_delay)).await;
		}
		
		let _uri = Uri::builder ()
			.scheme ("http")
			.authority ("127.0.0.1:4000")
			.path_and_query ("/http_listen/alien_wildlands")
		.build ().unwrap ();
		
		let req_req = client.get ("http://127.0.0.1:4000/http_listen/alien_wildlands");
		
		//println! ("Step 1");
		let req_resp = match req_req.send ().await {
			Err (e) => {
				println! ("Err: {:?}", e);
				backoff_delay = backoff_delay * 2 + 500;
				continue;
			},
			Ok (r) => {
				backoff_delay = 0;
				r
			},
		};
		
		if req_resp.status () != StatusCode::OK {
			continue;
		}
		
		println! ("Step 3");
		
		let body = req_resp.bytes ().await?;
		let parts: http_serde::RequestParts = match rmp_serde::from_read_ref (&body)
		{
			Ok (x) => x,
			_ => continue,
		};
		
		let (req_id, uri) = (parts.id, parts.uri);
		
		println! ("Client requested {}", uri);
		let mut range_start = None;
		let mut range_end = None;
		
		for (k, v) in parts.headers.iter () {
			let v = std::str::from_utf8 (v).unwrap ();
			//println! ("{}: {}", k, v);
			
			if k == "range" {
				let (start, end) = parse_range_header (v);
				range_start = start;
				range_end = end;
			}
		}
		
		let should_send_body = match &parts.method {
			http_serde::Method::Get => true,
			_ => false,
		};
		
		//println! ("Step 6");
		let client = client.clone ();
		tokio::spawn (async move {
			let mut path = PathBuf::from ("/home/user");
			path.push (&uri [1..]);
			let f = File::open (path).await.unwrap ();
			
			serve_file (
				client,
				f,
				req_id,
				should_send_body,
				range_start,
				range_end
			).await;
		});
	}
}