use crate::errors::Error;
use rocket::data::{Data, FromData, Outcome, ToByteUnit};
use rocket::request::Request;
use std::default::Default;
use std::ops::Deref;

pub mod cofd;

const CRATE_NAME: &'static str = env!("CARGO_BIN_NAME");

/// Convert an incoming protobuf content-type to the equivalent type
/// name produced by std::any::type_name(). Currently does NOT work
/// with nested types due to how prost generates the module names.
fn convert_to_rust_name(proto_type: &str) -> String {
    format!("{}::{}", CRATE_NAME, proto_type.replace(".", "::"))
}

/// A struct wrapping a protobuf that allows it to be used as binary
/// data submitted via POST using fetch API. Can automatically be
/// dereferenced into its wrapped type.
#[derive(Debug)]
pub(crate) struct Proto<T>(T)
where
    T: prost::Message + Default;

/// Converts the body of a POST request containing encoded protobuf
/// data into the wrapped type.
#[rocket::async_trait]
impl<T> FromData for Proto<T>
where
    T: prost::Message + Default,
{
    type Error = crate::errors::Error;

    async fn from_data(req: &Request<'_>, data: Data) -> Outcome<Self, Error> {
        use rocket::http::Status;
        let content_type = req.content_type();

        let is_protobuf = content_type
            .map(|ct| ct.top() == "application" && ct.sub() == "x-protobuf")
            .unwrap_or(false);

        let message_type: Option<String> = content_type.and_then(|ct| {
            ct.params()
                .find(|&(name, _)| name == "messageType")
                .map(|(_, message_type)| convert_to_rust_name(message_type))
        });

        if !is_protobuf {
            return Outcome::Failure((Status::new(422, "invalid protobuf"), Error::InvalidInput));
        }

        if message_type.as_ref().map(String::as_str) != Some(std::any::type_name::<T>()) {
            return Outcome::Forward(data);
        }

        let bytes: Vec<u8> = match data.open(2.mebibytes()).stream_to_vec().await {
            Ok(read_bytes) => read_bytes,
            Err(e) => return Outcome::Failure((Status::new(422, "invalid protobuf"), e.into())),
        };

        match T::decode(bytes.as_ref()) {
            Ok(decoded) => Outcome::Success(Proto(decoded)),
            Err(e) => Outcome::Failure((Status::new(422, "invalid protobuf"), e.into())),
        }
    }
}

/// Enable automatically calling methods on a decoded Proto instance.
impl<T> Deref for Proto<T>
where
    T: prost::Message + Default,
{
    type Target = T;

    fn deref(&self) -> &T {
        &self.0
    }
}