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/create_mr.go

@@ -0,0 +1,99 @@
+package app
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/xanzy/go-gitlab"
+)
+
+type CreateMrRequest struct {
+	Title           string `json:"title"`
+	Description     string `json:"description"`
+	TargetBranch    string `json:"target_branch"`
+	DeleteBranch    bool   `json:"delete_branch"`
+	Squash          bool   `json:"squash"`
+	TargetProjectID int    `json:"forked_project_id,omitempty"`
+}
+
+type MergeRequestCreator interface {
+	CreateMergeRequest(pid interface{}, opt *gitlab.CreateMergeRequestOptions, options ...gitlab.RequestOptionFunc) (*gitlab.MergeRequest, *gitlab.Response, error)
+}
+
+type mergeRequestCreatorService struct {
+	data
+	client MergeRequestCreator
+}
+
+/* createMr creates a merge request */
+func (a mergeRequestCreatorService) handler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Set("Access-Control-Allow-Methods", http.MethodGet)
+	if r.Method != 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
+	}
+
+	var createMrRequest CreateMrRequest
+	err = json.Unmarshal(body, &createMrRequest)
+	if err != nil {
+		handleError(w, err, "Could not unmarshal request body", http.StatusBadRequest)
+		return
+	}
+
+	if createMrRequest.Title == "" {
+		handleError(w, errors.New("Title cannot be empty"), "Could not create MR", http.StatusBadRequest)
+		return
+	}
+
+	if createMrRequest.TargetBranch == "" {
+		handleError(w, errors.New("Target branch cannot be empty"), "Could not create MR", http.StatusBadRequest)
+		return
+	}
+
+	opts := gitlab.CreateMergeRequestOptions{
+		Title:              &createMrRequest.Title,
+		Description:        &createMrRequest.Description,
+		TargetBranch:       &createMrRequest.TargetBranch,
+		SourceBranch:       &a.gitInfo.BranchName,
+		RemoveSourceBranch: &createMrRequest.DeleteBranch,
+		Squash:             &createMrRequest.Squash,
+	}
+
+	if createMrRequest.TargetProjectID != 0 {
+		opts.TargetProjectID = gitlab.Ptr(createMrRequest.TargetProjectID)
+	}
+
+	_, res, err := a.client.CreateMergeRequest(a.projectInfo.ProjectId, &opts)
+
+	if err != nil {
+		handleError(w, err, "Could not create MR", http.StatusInternalServerError)
+		return
+	}
+
+	if res.StatusCode >= 300 {
+		handleError(w, GenericError{endpoint: "/create_mr"}, "Could not create MR", res.StatusCode)
+		return
+	}
+
+	response := SuccessResponse{
+		Status:  http.StatusOK,
+		Message: fmt.Sprintf("MR '%s' created", createMrRequest.Title),
+	}
+
+	w.WriteHeader(http.StatusOK)
+
+	err = json.NewEncoder(w).Encode(response)
+	if err != nil {
+		handleError(w, err, "Could not encode response", http.StatusInternalServerError)
+	}
+}