feat: add interceptor pkg

pkg/interceptor/interceptor.go

@@ -0,0 +1,75 @@
+package interceptor
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+// Can be use this
+// c := &http.Client{
+// 	Transport: Interceptor{http.DefaultTransport},
+//   }
+
+type Interceptor struct {
+	core http.RoundTripper
+}
+
+func (Interceptor) ModifyRequest(r *http.Request) *http.Request {
+	reqBody := MustHumanize(r.Body)
+
+	// this is the request modification
+	modReqBody := []byte(fmt.Sprintf(`{"req": %s}`, reqBody))
+	ModReqBodyLen := len(modReqBody)
+
+	req := r.Clone(context.Background())
+	req.Body = io.NopCloser(bytes.NewReader(modReqBody))
+	req.ContentLength = int64(ModReqBodyLen)
+	req.Header.Set("Content-Length", fmt.Sprintf("%d", ModReqBodyLen))
+
+	return req
+}
+
+func (Interceptor) ModifyResponse(r *http.Response) *http.Response {
+	respBody := MustHumanize(r.Body)
+
+	// this is the response modification
+	modRespBody := []byte(fmt.Sprintf(`{"resp": %s}`, respBody))
+	ModRespBodyLen := len(modRespBody)
+
+	r.Body = io.NopCloser(bytes.NewReader(modRespBody))
+	r.ContentLength = int64(ModRespBodyLen)
+	r.Header.Set("Content-Length", fmt.Sprintf("%d", ModRespBodyLen))
+
+	return r
+}
+
+func (i Interceptor) RoundTrip(r *http.Request) (*http.Response, error) {
+	defer func() {
+		_ = r.Body.Close()
+	}()
+
+	// modify before the request is sent
+	newReq := i.ModifyRequest(r)
+
+	// send the request using the DefaultTransport
+	resp, _ := i.core.RoundTrip(newReq)
+	defer func() {
+		_ = resp.Body.Close()
+	}()
+
+	// modify after the response is received
+	newResp := i.ModifyResponse(resp)
+
+	return newResp, nil
+}
+
+func MustHumanize(r io.Reader) string {
+	var m map[string]interface{}
+	_ = json.NewDecoder(r).Decode(&m)
+	b, _ := json.MarshalIndent(m, "", "  ")
+	return string(b)
+}