Stub for merge request hook handling.

GitLab merge request hook payload doesn't provide
any information regarding source commits.

And since Drone currently doesn't support manual fetch from another
remote upstream, merge request hook only supported for maerge request
fro within the same repository.

pkg/handler/gitlab.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	"strconv"
 	"strings"
 	"time"
 
@@ -156,7 +157,8 @@ func (g *GitlabHandler) Hook(w http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 	if parsed.ObjectKind == "merge_request" {
-		return g.PullRequestHook(w, parsed)
+		fmt.Println(string(payload))
+		return g.PullRequestHook(w, r)
 	}
 
 	if len(parsed.After) == 0 {
@@ -243,7 +245,96 @@ func (g *GitlabHandler) Hook(w http.ResponseWriter, r *http.Request) error {
 
 }
 
-func (g *GitlabHandler) PullRequestHook(w http.ResponseWriter, p *gogitlab.HookPayload) error {
+func (g *GitlabHandler) PullRequestHook(w http.ResponseWriter, r *http.Request) error {
+	payload, _ := ioutil.ReadAll(r.Body)
+	p, err := gogitlab.ParseHook(payload)
+	if err != nil {
+		return err
+	}
+
+	obj := p.ObjectAttributes
+
+	// Gitlab may trigger multiple hooks upon updating merge requests status
+	// only build when it was just opened and the merge hasn't been checked yet.
+	if !(obj.State == "opened" && obj.MergeStatus == "unchecked") {
+		fmt.Printf("Ignore GitLab Merge Requests")
+		return RenderText(w, http.StatusText(http.StatusOK), http.StatusOK)
+	}
+
+	repo, err := database.GetRepoSlug(r.FormValue("id"))
+	if err != nil {
+		return RenderText(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
+	}
+
+	user, err := database.GetUser(repo.UserID)
+	if err != nil {
+		return RenderText(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
+	}
+
+	settings := database.SettingsMust()
+
+	client := gogitlab.NewGitlab(settings.GitlabApiUrl, g.apiPath, user.GitlabToken)
+
+	// GitLab merge-requests hook doesn't include repository data.
+	// Have to fetch it manually
+	src, err := client.RepoBranch(strconv.Itoa(obj.SourceProjectId), obj.SourceBranch)
+	if err != nil {
+		return err
+	}
+
+	_, err = database.GetCommitHash(src.Commit.Id, repo.ID)
+	if err != nil && err != sql.ErrNoRows {
+		println("commit already exists")
+		return RenderText(w, http.StatusText(http.StatusBadGateway), http.StatusBadGateway)
+	}
+
+	commit := &Commit{}
+	commit.RepoID = repo.ID
+	commit.Branch = src.Name
+	commit.Hash = src.Commit.Id
+	commit.Status = "Pending"
+	commit.Created = time.Now().UTC()
+
+	commit.Message = src.Commit.Message
+	commit.Timestamp = src.Commit.AuthoredDateRaw
+	commit.SetAuthor(src.Commit.Author.Email)
+
+	content, err := client.RepoRawFile(strconv.Itoa(obj.SourceProjectId), commit.Hash, ".drone.yml")
+	if err != nil {
+		msg := "No .drone.yml was found in this repository.  You need to add one.\n"
+		if err := saveFailedBuild(commit, msg); err != nil {
+			return RenderText(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+		}
+		return RenderText(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
+	}
+
+	// parse the build script
+	buildscript, err := script.ParseBuild(content, repo.Params)
+	if err != nil {
+		msg := "Could not parse your .drone.yml file.  It needs to be a valid drone yaml file.\n\n" + err.Error() + "\n"
+		if err := saveFailedBuild(commit, msg); err != nil {
+			return RenderText(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+		}
+		return RenderText(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
+	}
+
+	// save the commit to the database
+	if err := database.SaveCommit(commit); err != nil {
+		return RenderText(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+	}
+
+	// save the build to the database
+	build := &Build{}
+	build.Slug = "1" // TODO
+	build.CommitID = commit.ID
+	build.Created = time.Now().UTC()
+	build.Status = "Pending"
+	if err := database.SaveBuild(build); err != nil {
+		return RenderText(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+	}
+
+	g.queue.Add(&queue.BuildTask{Repo: repo, Commit: commit, Build: build, Script: buildscript})
+
 	return RenderText(w, http.StatusText(http.StatusOK), http.StatusOK)
 }