package proxy_test

import (
	"fmt"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"

	"git.wntrmute.dev/kyle/crossbar/internal/config"
	"git.wntrmute.dev/kyle/crossbar/internal/health"
	"git.wntrmute.dev/kyle/crossbar/internal/proxy"
)

// noFlush is a ResponseWriter that does not implement http.Flusher. Middleware and test
// recorders like this exist in the wild; the proxy must degrade to buffering, never panic.
type noFlush struct{ w http.ResponseWriter }

func (n noFlush) Header() http.Header         { return n.w.Header() }
func (n noFlush) Write(b []byte) (int, error) { return n.w.Write(b) }
func (n noFlush) WriteHeader(code int)        { n.w.WriteHeader(code) }

func TestStreamingWriterWithoutFlusherDoesNotPanic(t *testing.T) {
	up := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/event-stream")
		w.WriteHeader(200)
		for i := 0; i < 3; i++ {
			fmt.Fprintf(w, "data: chunk %d\n\n", i)
			w.(http.Flusher).Flush()
		}
	}))
	t.Cleanup(up.Close)
	cfg, err := config.Parse(strings.NewReader(fmt.Sprintf(`
listen = "127.0.0.1:1"
[hosts.alpha]
base_url = %q
models = { "m" = { } }
[routes.r]
hosts = ["alpha"]
`, up.URL)))
	if err != nil {
		t.Fatal(err)
	}
	h := &fakeHealth{st: map[string]health.Status{"alpha": {Healthy: true, Loaded: []string{"m"}}}}
	p := proxy.New(cfg, h, nil, nil, nil, nil)

	rec := httptest.NewRecorder()
	req := httptest.NewRequest(http.MethodPost, "/r/v1/chat/completions", strings.NewReader(`{"model":"m","stream":true}`))
	func() {
		defer func() {
			if r := recover(); r != nil {
				t.Fatalf("ServeHTTP panicked on a writer without Flush: %v", r)
			}
		}()
		p.ServeHTTP(noFlush{rec}, req)
	}()
	if rec.Code != 200 {
		t.Fatalf("status %d", rec.Code)
	}
	if got := rec.Body.String(); !strings.Contains(got, "chunk 0") || !strings.Contains(got, "chunk 2") {
		t.Errorf("body = %q, want all three chunks", got)
	}
	if rec.Header().Get(proxy.HostHeader) != "alpha" {
		t.Errorf("host header %q", rec.Header().Get(proxy.HostHeader))
	}
}