use std::io;
use std::io::Write;

use conduit::Handler;

use log::error;

use snafu::{ResultExt, Snafu};

use crate::request;


const HTTP_VERSION: &'static str = "HTTP/1.1";


#[derive(Debug, Snafu)]
pub enum Error {
    #[snafu(context(false))]
    Write { source: io::Error },

    #[snafu(display("Couldn't build request: {}", source))]
    RequestBuilder { source: request::Error },

    #[snafu(display("Couldn't parse response: {}", source))]
    ConduitResponse { source: conduit::BoxError },
}


pub struct Server;

impl Server {
    pub fn start<H: Handler + 'static + Sync>(handler: H) -> io::Result<Server> {
        fastcgi::run(move |mut raw_request| {
            match handle_request(&mut raw_request, &handler) {
                Ok(_) => (),
                Err(e) => match e {
                    // Ignore write errors as clients will have closed the
                    // connection by this point.
                    Error::Write { .. } => error!("Write error: {}", e),

                    Error::RequestBuilder { .. } => {
                        error!("Unable to build request: {}", e);

                        internal_server_error(&mut raw_request.stdout())
                    },
                    Error::ConduitResponse { .. } => {
                        error!("Error getting response: {}", e);

                        internal_server_error(&mut raw_request.stdout())
                    },
                }
            }
        });

        Ok(Server{})
    }
}

fn handle_request<H>(
    mut raw_request: &mut fastcgi::Request,
    handler: &H,
) -> Result<(), Error>
where H: Handler + 'static + Sync
{
    let mut request = request::FastCgiRequest::new(&mut raw_request)
        .context(RequestBuilder)?;
    let response = handler.call(&mut request);

    let mut stdout = raw_request.stdout();

    let (head, body) = response
        .context(ConduitResponse)?
        .into_parts();

    write!(
        &mut stdout,
        "{} {} {}\r\n",
        HTTP_VERSION,
        head.status.as_str(),
        head.status.canonical_reason().unwrap_or("UNKNOWN"),
    )?;

    for (name, value) in head.headers.iter() {
        write!(&mut stdout, "{}: ", name)?;
        stdout.write(value.as_bytes())?;
        stdout.write(b"\r\n")?;
    }

    stdout.write(b"\r\n")?;

    match body {
        conduit::Body::Static(slice) =>
            stdout.write(slice).map(|_| ())?,
        conduit::Body::Owned(vec) =>
            stdout.write(&vec).map(|_| ())?,
        conduit::Body::File(mut file) =>
            io::copy(&mut file, &mut stdout).map(|_| ())?,
    };

    Ok(())
}

fn internal_server_error<W: Write>(mut w: W) {
    let code = conduit::StatusCode::INTERNAL_SERVER_ERROR;

    match write!(
        w,
        "{} {} {}\r\n{}\r\n\r\n",
        HTTP_VERSION,
        code,
        code.canonical_reason().unwrap_or_default(),
        "Content-Length: 0",
    ) {
        Ok(_) => (),
        Err(e) => error!("Write error: {}", e),
    }
}