use std::{
	net::{IpAddr, SocketAddr},
	pin::Pin,
	process::Stdio,
	time::Instant,
};

use confindent::{Confindent, Value, ValueParseError};
use http_body_util::{BodyExt, Full};
use hyper::{
	HeaderMap, Request, Response, StatusCode,
	body::{Bytes, Incoming},
	header::{self, HeaderValue},
	server::conn::http1,
	service::Service,
};
use hyper_util::rt::TokioIo;
use regex_lite::Regex;
use tokio::{
	io::{AsyncWriteExt, BufWriter},
	net::TcpListener,
	process::Command,
	runtime::Runtime,
};

#[derive(Clone, Debug)]
pub struct Settings {
	port: u16,
	scripts: Vec<Script>,
}

#[derive(Clone, Debug)]
pub struct Script {
	name: String,
	regex: Option<Regex>,
	filename: String,
	env: Vec<(String, String)>,
}

const CONF_DEFAULT: &str = "/etc/corgi.conf";

fn main() {
	let conf_path = std::env::args().nth(1).unwrap_or(String::from(CONF_DEFAULT));
	let conf = Confindent::from_file(conf_path).expect("failed to open conf");

	let mut settings = Settings {
		port: 26744,
		scripts: conf.children("Script").into_iter().map(parse_script_conf).collect(),
	};

	if let Some(server) = conf.child("Server") {
		match server.child_parse("Port") {
			Err(ValueParseError::NoValue) => (),
			Err(err) => {
				eprintln!("Server.Port is malformed: {err}");
				std::process::exit(1);
			}
			Ok(port) => settings.port = port,
		}
	}

	let rt = Runtime::new().unwrap();
	rt.block_on(async { run(settings).await });
}

fn parse_script_conf(conf: &Value) -> Script {
	let name = conf.value_owned().expect("Missing value for 'Script' key");
	let filename = conf.child_owned("Path").expect("Missing 'Path' key");
	let environment = conf.child("Environment");
	let env = environment
		.map(|e| e.values().map(|v| (v.key_owned(), v.value_owned().unwrap())).collect());

	let regex = match conf.get("Match/Regex") {
		None => None,
		Some(restr) => match Regex::new(restr) {
			Err(err) => {
				eprintln!("Failed to compile regex: {restr}\nerror: {err}");
				std::process::exit(1);
			}
			Ok(re) => Some(re),
		},
	};

	Script {
		name,
		regex,
		filename,
		env: env.unwrap_or_default(),
	}
}

// We have tokio::main at home :)
async fn run(settings: Settings) {
	let addr = SocketAddr::from(([0, 0, 0, 0], settings.port));
	let listen = TcpListener::bind(addr).await.unwrap();

	let svc = Svc {
		settings,
		client_addr: addr,
	};

	loop {
		let (stream, caddr) = listen.accept().await.unwrap();
		let io = TokioIo::new(stream);
		let mut svc_clone = svc.clone();
		svc_clone.client_addr = caddr;
		tokio::task::spawn(
			async move { http1::Builder::new().serve_connection(io, svc_clone).await },
		);
	}
}

#[derive(Clone, Debug)]
struct Svc {
	settings: Settings,
	client_addr: SocketAddr,
}

impl Service<Request<Incoming>> for Svc {
	type Response = Response<Full<Bytes>>;
	type Error = hyper::Error;
	type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;

	fn call(&self, req: Request<Incoming>) -> Self::Future {
		let settings = self.settings.clone();
		let caddr = self.client_addr;

		Box::pin(async move { Ok(Self::handle(settings, caddr, req).await) })
	}
}

impl Svc {
	async fn handle(
		settings: Settings,
		caddr: SocketAddr,
		req: Request<Incoming>,
	) -> Response<Full<Bytes>> {
		let start = Instant::now();

		// Collect things we need from the request before we eat it's body
		let method = req.method().as_str().to_ascii_uppercase();
		let version = req.version();
		let path = req.uri().path().to_owned();
		let query = req.uri().query().unwrap_or_default().to_owned();
		let headers = req.headers().clone();
		let body = req.into_body().collect().await.unwrap().to_bytes();
		let content_length = body.len();

		let mut script = settings.scripts[0].clone();

		for set_script in settings.scripts {
			if let Some(regex) = set_script.regex.as_ref() {
				if regex.is_match(&path) {
					script = set_script;
					break;
				}
			} else {
				script = set_script;
			}
		}

		let content_type = headers
			.get("content-type")
			.map(|s| s.to_str().ok())
			.flatten()
			.unwrap_or_default()
			.to_owned();

		println!("!!! new request. type {content_type} // {method}");
		println!("!!! {path}?{query}");

		let uagent = headers
			.get("user-agent")
			.map(|s| s.to_str().ok())
			.flatten()
			.unwrap_or_default()
			.to_owned();

		// Find the client address
		let client_addr = {
			let x_forward = Self::parse_addr_from_header(headers.get("x-forwarded-for"));
			let forward = Self::parse_addr_from_header(headers.get("forwarded-for"));

			forward.unwrap_or(x_forward.unwrap_or(caddr.ip()))
		};

		let server_name = headers
			.get("Host")
			.expect("no http host header set")
			.to_str()
			.expect("failed to decode http host as string");

		let mut cmd = Command::new(&script.filename);
		cmd.env("CONTENT_TYPE", content_type)
			.env("GATEWAY_INTERFACE", "CGI/1.1")
			.env("PATH_INFO", &path)
			.env("QUERY_STRING", query)
			.env("REMOTE_ADDR", client_addr.to_string())
			.env("REQUEST_METHOD", method)
			.env("SCRIPT_NAME", script.filename)
			.env("SERVER_NAME", server_name)
			.env("SERVER_PORT", settings.port.to_string())
			.env("SERVER_PROTOCOL", format!("{:?}", version))
			.env("SERVER_SOFTWARE", Self::SERVER_SOFTWARE);

		if content_length > 0 {
			cmd.env("CONTENT_LENGTH", content_length.to_string());
		}

		// Set env associated with the HTTP request headers
		Self::set_http_env(headers, &mut cmd);

		// Set env specified in the conf. Be sure we do this after we
		// set the HTTP headers as to overwrite any we might want
		for (key, value) in &script.env {
			cmd.env(key.to_ascii_uppercase(), value);
		}

		let debugcgi = script.name == "git-backend";

		let cgibody = if content_length > 0 {
			Some(&body)
		} else {
			None
		};

		let start_cgi = Instant::now();
		let cgi_response =
			Self::call_and_parse_cgi(cmd, cgibody, caddr.ip(), debugcgi, &path).await;
		let cgi_time = start_cgi.elapsed();

		let status = StatusCode::from_u16(cgi_response.status).unwrap();
		let mut response = Response::builder().status(status);

		for (key, value) in cgi_response.headers {
			response = response.header(key, value);
		}

		println!(
			"served to [{client_addr}]\n\tscript: {}\n\tpath: {path}\n\tcgi took {}ms. total time {}ms\n\tUA: {uagent}",
			&script.name,
			cgi_time.as_millis(),
			start.elapsed().as_millis()
		);

		let response_body = cgi_response.body.map(|v| Bytes::from(v)).unwrap_or(Bytes::new());
		response.body(Full::new(response_body)).unwrap()
	}

	fn parse_addr_from_header(maybe_hval: Option<&HeaderValue>) -> Option<IpAddr> {
		maybe_hval.map(|h| h.to_str().ok()).flatten().map(|s| s.parse().ok()).flatten()
	}

	const SERVER_SOFTWARE: &'static str =
		concat!(env!("CARGO_PKG_NAME"), '/', env!("CARGO_PKG_VERSION"));

	fn set_http_env(headers: HeaderMap, cmd: &mut Command) {
		for (key, value) in headers.iter() {
			let key_str = key.as_str();

			let mut key_upper = String::with_capacity(key_str.len() + 5);
			key_upper.push_str("HTTP_");

			for ch in key_str.chars() {
				match ch {
					_ if ch as u8 > 0x60 && ch as u8 <= 0x7A => {
						key_upper.push((ch as u8 - 0x20) as char);
					}
					'-' => key_upper.push('_'),
					ch => key_upper.push(ch),
				}
			}

			match value.to_str() {
				Ok(val_str) => {
					cmd.env(key_upper, val_str);
				}
				Err(err) => {
					eprintln!("value for header {key_str} is not a string: {err}")
				}
			}
		}
	}

	async fn call_and_parse_cgi(
		mut cmd: Command,
		body: Option<&Bytes>,
		caddr: IpAddr,
		debug: bool,
		path: &str,
	) -> CgiResponse {
		let mut response = CgiResponse {
			// Default status code is 200 per RFC
			status: 200,
			headers: vec![],
			body: None,
		};

		println!("!!! before spawn: {path}");
		let cmd = cmd.stdout(Stdio::piped()).stderr(Stdio::piped());
		let output = if let Some(bytes) = body {
			println!("!!! has body len={}", bytes.len());
			let mut child = cmd.stdin(Stdio::piped()).spawn().unwrap();

			let cmd_stdin = child.stdin.take().unwrap();
			let mut bufwrite = BufWriter::new(cmd_stdin);
			bufwrite.write_all(bytes).await.unwrap();

			drop(bufwrite);
			println!("!!! after drop ({path})");

			child.wait_with_output().await.unwrap()
		} else {
			cmd.spawn().unwrap().wait_with_output().await.unwrap()
		};
		println!("!!! after spawn ({path})");

		let response_raw = output.stdout;

		if debug {
			std::fs::write(
				format!("/tmp/{caddr}-gitbackend-{}", path_to_name(path)),
				&response_raw,
			)
			.unwrap();
		}

		let mut curr = response_raw.as_slice();
		loop {
			// Find the newline to know where this header ends
			let nl = curr.iter().position(|b| *b == b'\n').expect("no nl in header");
			let line = &curr[..nl];

			// Find the colon to separate the key from the value
			let colon = line.iter().position(|b| *b == b':').expect("no colon in header");
			let key = &line[..colon];
			let mut value = &line[colon + 1..];

			if value[0] == b' ' {
				value = &value[1..];
			}
			if value[value.len().saturating_sub(1)] == b'\r' {
				value = &value[..value.len().saturating_sub(1)];
			}

			response.headers.push((key.to_vec(), value.to_vec()));

			// Is this header a status line?
			let key_string = String::from_utf8_lossy(key);
			if key_string == "Status" {
				let value_string = String::from_utf8_lossy(value);
				if let Some((raw_code, _raw_msg)) = value_string.trim().split_once(' ') {
					let code: u16 = raw_code.parse().unwrap();
					response.status = code;
				}
			}

			// Body next?
			let next_nl = curr[nl + 1] == b'\n';
			let next_crlf = curr[nl + 1] == b'\r' && curr[nl + 2] == b'\n';
			if next_nl || next_crlf {
				let offset = if next_nl { 2 } else { 3 };
				let body = &curr[nl + offset..];
				if body.len() > 0 {
					response.body = Some(body.to_vec());
				}

				println!("!!! before call_and_parse return ({path})");
				return response;
			}

			// Move past the newline
			curr = &curr[nl + 1..];
		}
	}
}

struct CgiResponse {
	/// The Status header of the CGI response
	status: u16,
	/// Headers except "Status"
	headers: Vec<(Vec<u8>, Vec<u8>)>,
	/// CGI response body
	body: Option<Vec<u8>>,
}

fn path_to_name(path: &str) -> String {
	let mut ret = String::with_capacity(path.len());
	for ch in path.chars() {
		match ch {
			'/' => ret.push('-'),
			ch => ret.push(ch),
		}
	}
	ret
}