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/label.go

@@ -0,0 +1,140 @@
+package app
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/xanzy/go-gitlab"
+)
+
+type LabelUpdateRequest struct {
+	Labels []string `json:"labels"`
+}
+
+type Label struct {
+	Name  string
+	Color string
+}
+
+type LabelUpdateResponse struct {
+	SuccessResponse
+	Labels gitlab.Labels `json:"labels"`
+}
+
+type LabelsRequestResponse struct {
+	SuccessResponse
+	Labels []Label `json:"labels"`
+}
+
+type LabelManager interface {
+	UpdateMergeRequest(interface{}, int, *gitlab.UpdateMergeRequestOptions, ...gitlab.RequestOptionFunc) (*gitlab.MergeRequest, *gitlab.Response, error)
+	ListLabels(interface{}, *gitlab.ListLabelsOptions, ...gitlab.RequestOptionFunc) ([]*gitlab.Label, *gitlab.Response, error)
+}
+
+type labelService struct {
+	data
+	client LabelManager
+}
+
+/* labelsHandler adds or removes labels from a merge request, and returns all labels for the current project */
+func (a labelService) handler(w http.ResponseWriter, r *http.Request) {
+	switch r.Method {
+	case http.MethodGet:
+		a.getLabels(w, r)
+	case http.MethodPut:
+		a.updateLabels(w, r)
+	default:
+		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set("Access-Control-Allow-Methods", fmt.Sprintf("%s, %s", http.MethodPut, http.MethodGet))
+		handleError(w, InvalidRequestError{}, "Expected GET or PUT", http.StatusMethodNotAllowed)
+	}
+}
+
+func (a labelService) getLabels(w http.ResponseWriter, _ *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+
+	labels, res, err := a.client.ListLabels(a.projectInfo.ProjectId, &gitlab.ListLabelsOptions{})
+
+	if err != nil {
+		handleError(w, err, "Could not modify merge request labels", http.StatusInternalServerError)
+		return
+	}
+
+	if res.StatusCode >= 300 {
+		handleError(w, GenericError{endpoint: "/mr/label"}, "Could not modify merge request labels", res.StatusCode)
+		return
+	}
+
+	/* Hacky, but convert them to the correct response */
+	convertedLabels := make([]Label, len(labels))
+	for i, labelPtr := range labels {
+		convertedLabels[i] = Label{
+			Name:  labelPtr.Name,
+			Color: labelPtr.Color,
+		}
+	}
+
+	w.WriteHeader(http.StatusOK)
+	response := LabelsRequestResponse{
+		SuccessResponse: SuccessResponse{
+			Message: "Labels updated",
+			Status:  http.StatusOK,
+		},
+		Labels: convertedLabels,
+	}
+
+	err = json.NewEncoder(w).Encode(response)
+	if err != nil {
+		handleError(w, err, "Could not encode response", http.StatusInternalServerError)
+	}
+
+}
+
+func (a labelService) updateLabels(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	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 labelUpdateRequest LabelUpdateRequest
+	err = json.Unmarshal(body, &labelUpdateRequest)
+
+	if err != nil {
+		handleError(w, err, "Could not read JSON from request", http.StatusBadRequest)
+		return
+	}
+
+	var labels = gitlab.LabelOptions(labelUpdateRequest.Labels)
+	mr, res, err := a.client.UpdateMergeRequest(a.projectInfo.ProjectId, a.projectInfo.MergeId, &gitlab.UpdateMergeRequestOptions{
+		Labels: &labels,
+	})
+
+	if err != nil {
+		handleError(w, err, "Could not modify merge request labels", http.StatusInternalServerError)
+		return
+	}
+
+	if res.StatusCode >= 300 {
+		handleError(w, GenericError{endpoint: "/mr/label"}, "Could not modify merge request labels", res.StatusCode)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	response := LabelUpdateResponse{
+		SuccessResponse: SuccessResponse{
+			Message: "Labels updated",
+			Status:  http.StatusOK,
+		},
+		Labels: mr.Labels,
+	}
+
+	err = json.NewEncoder(w).Encode(response)
+	if err != nil {
+		handleError(w, err, "Could not encode response", http.StatusInternalServerError)
+	}
+}