// Types re-exported from crate root

use futures::{
    future::BoxFuture,
    stream::{Stream, StreamExt},
};

mod typed;
pub use typed::{MatchDispatch, MatchDispatchFrom, TypeNotification};

/// Cast from `N` to `M` by serializing/deserialization to/from JSON.
pub fn json_cast<N, M>(params: N) -> Result<M, crate::Error>
where
    N: serde::Serialize,
    M: serde::de::DeserializeOwned,
{
    let json = serde_json::to_value(params).map_err(|e| {
        crate::Error::parse_error().data(serde_json::json!({
            "error": e.to_string(),
            "phase": "serialization"
        }))
    })?;
    let m = serde_json::from_value(json.clone()).map_err(|e| {
        crate::Error::parse_error().data(serde_json::json!({
            "error": e.to_string(),
            "json": json,
            "phase": "deserialization"
        }))
    })?;
    Ok(m)
}

/// Cast incoming request/notification params into a typed payload.
///
/// Like [`json_cast`], but deserialization failures become
/// [`Error::invalid_params`](`crate::Error::invalid_params`) (`-32602`)
/// instead of a parse error, which is the correct JSON-RPC error code for
/// malformed method parameters.
pub fn json_cast_params<N, M>(params: N) -> Result<M, crate::Error>
where
    N: serde::Serialize,
    M: serde::de::DeserializeOwned,
{
    let json = serde_json::to_value(params).map_err(|e| {
        crate::Error::internal_error().data(serde_json::json!({
            "error": e.to_string(),
            "phase": "serialization"
        }))
    })?;
    let m = serde_json::from_value(json.clone()).map_err(|e| {
        crate::Error::invalid_params().data(serde_json::json!({
            "error": e.to_string(),
            "json": json,
            "phase": "deserialization"
        }))
    })?;
    Ok(m)
}

/// Creates an internal error with the given message
pub fn internal_error(message: impl ToString) -> crate::Error {
    crate::Error::internal_error().data(message.to_string())
}

/// Creates a parse error with the given message
pub fn parse_error(message: impl ToString) -> crate::Error {
    crate::Error::parse_error().data(message.to_string())
}

/// Convert a JSON-RPC id to a serde_json::Value.
pub(crate) fn id_to_json(id: &jsonrpcmsg::Id) -> serde_json::Value {
    match id {
        jsonrpcmsg::Id::Number(n) => serde_json::Value::Number((*n).into()),
        jsonrpcmsg::Id::String(s) => serde_json::Value::String(s.clone()),
        jsonrpcmsg::Id::Null => serde_json::Value::Null,
    }
}

pub(crate) fn instrumented_with_connection_name<F>(
    name: String,
    task: F,
) -> tracing::instrument::Instrumented<F> {
    use tracing::Instrument;

    task.instrument(tracing::info_span!("connection", name = name))
}

pub(crate) async fn instrument_with_connection_name<R>(
    name: Option<String>,
    task: impl Future<Output = R>,
) -> R {
    if let Some(name) = name {
        instrumented_with_connection_name(name.clone(), task).await
    } else {
        task.await
    }
}

/// Convert a `crate::Error` into a `crate::jsonrpcmsg::Error`
#[must_use]
pub fn into_jsonrpc_error(err: crate::Error) -> crate::jsonrpcmsg::Error {
    crate::jsonrpcmsg::Error {
        code: err.code.into(),
        message: err.message,
        data: err.data,
    }
}

/// Run two fallible futures concurrently, returning when both complete successfully
/// or when either fails.
pub async fn both<E>(
    a: impl Future<Output = Result<(), E>>,
    b: impl Future<Output = Result<(), E>>,
) -> Result<(), E> {
    let ((), ()) = futures::future::try_join(a, b).await?;
    Ok(())
}

/// Run `background` until `foreground` completes.
///
/// Returns the result of `foreground`. If `background` errors before
/// `foreground` completes, the error is propagated. If `background`
/// completes with `Ok(())`, we continue waiting for `foreground`.
pub async fn run_until<T, E>(
    background: impl Future<Output = Result<(), E>>,
    foreground: impl Future<Output = Result<T, E>>,
) -> Result<T, E> {
    use futures::future::{Either, select};
    use std::pin::pin;

    match select(pin!(background), pin!(foreground)).await {
        Either::Left((bg_result, fg_future)) => {
            // Background finished first
            bg_result?; // propagate error, or if Ok(()), keep waiting
            fg_future.await
        }
        Either::Right((fg_result, _bg_future)) => {
            // Foreground finished first, drop background
            fg_result
        }
    }
}

/// Process items from a stream concurrently.
///
/// For each item received from `stream`, calls `process_fn` to create a future,
/// then runs all futures concurrently. If any future returns an error,
/// stops processing and returns that error.
///
/// This is useful for patterns where you receive work items from a channel
/// and want to process them concurrently while respecting backpressure.
pub async fn process_stream_concurrently<T, F>(
    stream: impl Stream<Item = T>,
    process_fn: F,
    process_fn_hack: impl for<'a> Fn(&'a F, T) -> BoxFuture<'a, Result<(), crate::Error>>,
) -> Result<(), crate::Error>
where
    F: AsyncFn(T) -> Result<(), crate::Error>,
{
    use std::pin::pin;

    use futures::stream::{FusedStream, FuturesUnordered};
    use futures_concurrency::future::Race;

    enum Event<T> {
        NewItem(Option<T>),
        FutureCompleted(Option<Result<(), crate::Error>>),
    }

    let mut stream = pin!(stream.fuse());
    let mut futures: FuturesUnordered<_> = FuturesUnordered::new();

    loop {
        // If we have no futures to run, wait until we do.
        if futures.is_empty() {
            match stream.next().await {
                Some(item) => futures.push(process_fn_hack(&process_fn, item)),
                None => return Ok(()),
            }
            continue;
        }

        // If there are no more items coming in, just drain our queue and return.
        if stream.is_terminated() {
            while let Some(result) = futures.next().await {
                result?;
            }
            return Ok(());
        }

        // Otherwise, race between getting a new item and completing a future.
        let event = (async { Event::NewItem(stream.next().await) }, async {
            Event::FutureCompleted(futures.next().await)
        })
            .race()
            .await;

        match event {
            Event::NewItem(Some(item)) => {
                futures.push(process_fn_hack(&process_fn, item));
            }
            Event::FutureCompleted(Some(result)) => {
                result?;
            }
            Event::NewItem(None) | Event::FutureCompleted(None) => {
                // Stream closed, loop will catch is_terminated
                // No futures were pending, shouldn't happen since we checked is_empty
            }
        }
    }
}
