package serverinterceptors

import (
	"context"
	"sync"
	"time"

	"google.golang.org/grpc"
)

// UnaryTimeoutInterceptor returns a func that sets timeout to incoming unary requests.
func UnaryTimeoutInterceptor(timeout time.Duration) grpc.UnaryServerInterceptor {
	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo,
		handler grpc.UnaryHandler) (interface{}, error) {
		ctx, cancel := context.WithTimeout(ctx, timeout)
		defer cancel()

		var resp interface{}
		var err error
		var lock sync.Mutex
		done := make(chan struct{})
		// create channel with buffer size 1 to avoid goroutine leak
		panicChan := make(chan interface{}, 1)
		go func() {
			defer func() {
				if p := recover(); p != nil {
					panicChan <- p
				}
			}()

			lock.Lock()
			defer lock.Unlock()
			resp, err = handler(ctx, req)
			close(done)
		}()

		select {
		case p := <-panicChan:
			panic(p)
		case <-done:
			lock.Lock()
			defer lock.Unlock()
			return resp, err
		case <-ctx.Done():
			return nil, ctx.Err()
		}
	}
}