use std::{
	net::{IpAddr, SocketAddr},
	pin::Pin,
};

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

#[derive(Clone, Debug)]
pub struct Settings {
	port: u16,
	script_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 script = conf.child("Script").expect("no 'Script' key in conf");
	let environment = script.child("Environment");
	let env = environment
		.map(|e| e.values().map(|v| (v.key_owned(), v.value_owned().unwrap())).collect());

	let settings = Settings {
		port: 26744,
		script_filename: script.value_owned().expect("'Script' key has no value'"),
		env: env.unwrap_or_default(),
	};

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

// 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>> {
		// 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();

		// 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(&settings.script_filename);
		cmd.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", settings.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 &settings.env {
			cmd.env(key.to_ascii_uppercase(), value);
		}

		let cgi_response = Self::call_and_parse_cgi(cmd).await;
		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);
		}

		response.body(Full::new(Bytes::from(body.to_vec()))).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) -> CgiResponse {
		let mut response = CgiResponse {
			// Default status code is 200 per RFC
			status: 200,
			headers: vec![],
			body: None,
		};

		let output = cmd.output().await.unwrap();
		let response_raw = output.stdout;

		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 value = &line[colon + 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?
			if curr[nl + 1] == b'\n' || (curr[nl + 1] == b'\r' && curr[nl + 2] == b'\n') {
				let body = &curr[nl + 2..];
				if body.len() > 0 {
					response.body = Some(body.to_vec());
				}

				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>>,
}