kojiapi: Check job type when retrieving from queue

When a job's arguments are retrieved (for the /manifests API endpoint),
the incoming ID should correspond to a Finalize Job.  The new
worker.Job() method helps us verify the type and produce an error if the
wrong type is found.
Similarly, the dependencies of a Finalize Job should be in order (Init
Job first followed by Build Jobs).  The types are validated while
iterating the dependency list.

Added convenience functions that check the retrieved job type and return
the initialised struct or an error if the ID is not found or does not
match the type.

Currently the getInitJob() function isn't used but it will be useful
later.

internal/kojiapi/server.go

@@ -384,6 +384,53 @@ func (h *apiHandlers) GetComposeIdLogs(ctx echo.Context, idstr string) error {
 	return ctx.JSON(http.StatusOK, response)
 }
 
+// getFinalizeJob retrieves a KojiFinalizeJob and the IDs of its dependencies
+// from the job queue given its ID.  It returns an error if the ID matches a
+// job of a different type.
+func (h *apiHandlers) getFinalizeJob(id uuid.UUID) (*worker.KojiFinalizeJob, []uuid.UUID, error) {
+	job := new(worker.KojiFinalizeJob)
+	jobType, _, deps, err := h.server.workers.Job(id, job)
+	if err != nil {
+		return nil, nil, err
+	}
+	expType := "koji-finalize"
+	if jobType != expType {
+		return nil, nil, fmt.Errorf("expected %q, found %q job instead", expType, jobType)
+	}
+	return job, deps, err
+}
+
+// getInitJob retrieves a KojiInitJob from the job queue given its ID.
+// It returns an error if the ID matches a job of a different type.
+func (h *apiHandlers) getInitJob(id uuid.UUID) (*worker.KojiInitJob, error) {
+	job := new(worker.KojiInitJob)
+	jobType, _, _, err := h.server.workers.Job(id, job)
+	if err != nil {
+		return nil, err
+	}
+	expType := "koji-init"
+	if jobType != expType {
+		return nil, fmt.Errorf("expected %q, found %q job instead", expType, jobType)
+	}
+	return job, err
+}
+
+// getBuildJob retrieves a OSBuildKojiJob and the IDs of its dependencies from
+// the job queue given its ID.  It returns an error if the ID matches a job of
+// a different type.
+func (h *apiHandlers) getBuildJob(id uuid.UUID) (*worker.OSBuildKojiJob, []uuid.UUID, error) {
+	job := new(worker.OSBuildKojiJob)
+	jobType, _, deps, err := h.server.workers.Job(id, job)
+	if err != nil {
+		return nil, nil, err
+	}
+	expType := "osbuild-koji"
+	if !strings.HasPrefix(jobType, expType) { // Build jobs get automatic arch suffix: Check prefix
+		return nil, nil, fmt.Errorf("expected %q, found %q job instead", expType, jobType)
+	}
+	return job, deps, nil
+}
+
 // GetComposeIdManifests returns the Manifests for a given Compose (one for each image).
 func (h *apiHandlers) GetComposeIdManifests(ctx echo.Context, idstr string) error {
 	id, err := uuid.Parse(idstr)
@@ -391,21 +438,15 @@ func (h *apiHandlers) GetComposeIdManifests(ctx echo.Context, idstr string) erro
 		return echo.NewHTTPError(http.StatusBadRequest, fmt.Sprintf("Invalid format for parameter id: %s", err))
 	}
 
-	var finalizeResult worker.KojiFinalizeJobResult
-	_, deps, err := h.server.workers.JobStatus(id, &finalizeResult)
+	_, deps, err := h.getFinalizeJob(id)
 	if err != nil {
 		return echo.NewHTTPError(http.StatusNotFound, fmt.Sprintf("Job %s not found: %s", idstr, err))
 	}
 
-	if len(deps) <= 1 {
-		// ID matched a job ID that's not a Finalize job. Treat it as "not found".
-		return echo.NewHTTPError(http.StatusNotFound, fmt.Sprintf("Job %s not found: job does not exist", idstr))
-	}
-
 	manifests := make([]distro.Manifest, len(deps)-1)
 	for i, id := range deps[1:] {
-		var buildJob worker.OSBuildKojiJob
-		if _, _, _, err := h.server.workers.Job(id, &buildJob); err != nil {
+		buildJob, _, err := h.getBuildJob(id)
+		if err != nil {
 			// This is a programming error.
 			panic(err)
 		}