Fix MR Selection, Go Code Refactor (#358)

refactor: Refactors the Go codebase into a more modular and idiomatic approach
fix: require selection of specific MR when there are multiple targets for a given source branch
feat: Allows for the passing of Gitlab's filter options when choosing an MR, improves MR selection
feat: API to choose an MR from a list based on the provided username's involvement as an assignee/reviewer/author

This is a #MINOR release

cmd/app/reply.go

@@ -0,0 +1,87 @@
+package app
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/xanzy/go-gitlab"
+)
+
+type ReplyRequest struct {
+	DiscussionId string `json:"discussion_id"`
+	Reply        string `json:"reply"`
+	IsDraft      bool   `json:"is_draft"`
+}
+
+type ReplyResponse struct {
+	SuccessResponse
+	Note *gitlab.Note `json:"note"`
+}
+
+type ReplyManager interface {
+	AddMergeRequestDiscussionNote(interface{}, int, string, *gitlab.AddMergeRequestDiscussionNoteOptions, ...gitlab.RequestOptionFunc) (*gitlab.Note, *gitlab.Response, error)
+}
+
+type replyService struct {
+	data
+	client ReplyManager
+}
+
+/* replyHandler sends a reply to a note or comment */
+func (a replyService) handler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	if r.Method != http.MethodPost {
+		w.Header().Set("Access-Control-Allow-Methods", http.MethodPost)
+		handleError(w, InvalidRequestError{}, "Expected POST", http.StatusMethodNotAllowed)
+		return
+	}
+
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		handleError(w, err, "Could not read request body", http.StatusBadRequest)
+		return
+	}
+
+	defer r.Body.Close()
+	var replyRequest ReplyRequest
+	err = json.Unmarshal(body, &replyRequest)
+
+	if err != nil {
+		handleError(w, err, "Could not read JSON from request", http.StatusBadRequest)
+		return
+	}
+
+	now := time.Now()
+	options := gitlab.AddMergeRequestDiscussionNoteOptions{
+		Body:      gitlab.Ptr(replyRequest.Reply),
+		CreatedAt: &now,
+	}
+
+	note, res, err := a.client.AddMergeRequestDiscussionNote(a.projectInfo.ProjectId, a.projectInfo.MergeId, replyRequest.DiscussionId, &options)
+
+	if err != nil {
+		handleError(w, err, "Could not leave reply", http.StatusInternalServerError)
+		return
+	}
+
+	if res.StatusCode >= 300 {
+		handleError(w, GenericError{endpoint: "/mr/reply"}, "Could not leave reply", res.StatusCode)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	response := ReplyResponse{
+		SuccessResponse: SuccessResponse{
+			Message: "Replied to comment",
+			Status:  http.StatusOK,
+		},
+		Note: note,
+	}
+
+	err = json.NewEncoder(w).Encode(response)
+	if err != nil {
+		handleError(w, err, "Could not encode response", http.StatusInternalServerError)
+	}
+}