fix: SCA-151 improve gzippedBody Read logic and add test coverage

- Fixed handling of empty input and buffer availability in `gzippedBody.Read`.
- Added panic to ensure non-zero bytes read when expected.
- Introduced `gzipped_body_test.go` for comprehensive test coverage of `gzippedBody`.

Author: iseki0

api/gzipped_body.go

@@ -36,10 +36,13 @@ func (g *gzippedBody) GetBody() (io.ReadCloser, error) {
 }
 
 func (g *gzippedBody) Read(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return 0, nil
+	}
 	if g.gzipWriter == nil {
 		g.gzipWriter = gzip.NewWriter(&g.buf)
 	}
-	for g.buf.Available() == 0 {
+	for g.buf.Len() == 0 {
 		if g.end {
 			return 0, io.EOF
 		}
@@ -55,8 +58,11 @@ func (g *gzippedBody) Read(p []byte) (n int, err error) {
 			return 0, e
 		}
 	}
-
-	return g.reader.Read(p)
+	n, _ = g.buf.Read(p)
+	if n == 0 {
+		panic("n == 0")
+	}
+	return
 }
 
 func (g *gzippedBody) Close() error {

api/gzipped_body_test.go

@@ -0,0 +1,23 @@
+package api
+
+import (
+	"compress/gzip"
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGzippedBody_Read(t *testing.T) {
+	var data = map[string]any{}
+	for i := 0; i < 10000; i++ {
+		data[fmt.Sprint(i)] = fmt.Sprint(i)
+	}
+	var body = NewGzippedBody(NewJsonRequestBody(data))
+	gr, _ := gzip.NewReader(body)
+	var dec = json.NewDecoder(gr)
+	var data2 map[string]any
+	assert.NoError(t, dec.Decode(&data2))
+	assert.EqualValues(t, data, data2)
+}