package middleware

import (
	"compress/gzip"
	"io"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
)

func TestGzip_SkipsWhenNotAccepted(t *testing.T) {
	handler := Gzip(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("plain"))
	}))

	req := httptest.NewRequest(http.MethodGet, "/", nil)
	rec := httptest.NewRecorder()
	handler.ServeHTTP(rec, req)

	if got := rec.Header().Get("Content-Encoding"); got != "" {
		t.Errorf("expected no content encoding, got %q", got)
	}
	if rec.Body.String() != "plain" {
		t.Errorf("expected plain response, got %q", rec.Body.String())
	}
}

func TestGzip_CompressesWhenAccepted(t *testing.T) {
	handler := Gzip(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("compressed"))
	}))

	req := httptest.NewRequest(http.MethodGet, "/", nil)
	req.Header.Set("Accept-Encoding", "gzip")
	rec := httptest.NewRecorder()
	handler.ServeHTTP(rec, req)

	if got := rec.Header().Get("Content-Encoding"); got != "gzip" {
		t.Fatalf("expected gzip encoding, got %q", got)
	}
	if got := rec.Header().Get("Vary"); !strings.Contains(got, "Accept-Encoding") {
		t.Fatalf("expected Vary to include Accept-Encoding, got %q", got)
	}

	reader, err := gzip.NewReader(rec.Body)
	if err != nil {
		t.Fatalf("failed to create gzip reader: %v", err)
	}
	defer reader.Close()

	data, err := io.ReadAll(reader)
	if err != nil {
		t.Fatalf("failed to read gzip body: %v", err)
	}

	if string(data) != "compressed" {
		t.Errorf("expected decompressed body 'compressed', got %q", string(data))
	}
}