JSON Stream Golang

http.go

package jsonstream

import (
        "encoding/json"
        "fmt"
        "io"
        "net/http"
        "sync"
)

func FromHTTP[T any](client *http.Client, req *http.Request) *Stream[T] {
        c := make(chan Result[T])
        f := func() { runReq(client, req, c) }
        return &Stream[T]{
                c:      c,
                openFn: f,
        }
}

type Result[T any] struct {
        Val T
        Err error
}

type Stream[T any] struct {
        c      <-chan Result[T]
        mux    sync.Mutex
        openFn func()
        isOpen bool
}

func (s *Stream[T]) Chan() <-chan Result[T] {
        s.mux.Lock()
        defer s.mux.Unlock()
        if !s.isOpen {
                go s.openFn()
                s.isOpen = true
        }
        return s.c
}

func runReq[T any](h *http.Client, r *http.Request, c chan<- Result[T]) {
        defer close(c)
        res, err := h.Do(r)
        if err != nil {
                c <- Result[T]{Err: err}
                return
        }
        defer res.Body.Close()
        if res.StatusCode != http.StatusOK {
                c <- Result[T]{Err: fmt.Errorf("unexpected status: %s", res.Status)}
                return
        }
        d := json.NewDecoder(res.Body)
        for d.More() {
                var val T
                if err := d.Decode(&val); err != nil {
                        c <- Result[T]{Err: err}
                        return
                }
                c <- Result[T]{Val: val}
        }
        if d.Decode(nil) == io.ErrUnexpectedEOF {
                c <- Result[T]{Err: io.ErrUnexpectedEOF}
        }
}