Prefer autoscaling based on jobs rather than workflows if available (#114)

Adds the ability to autoscale on jobs in addition to workflows. We fall back to using workflow metrics if job details are not present.

Resolves #89

github/fake/fake.go

@@ -4,7 +4,10 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"strconv"
+	"strings"
 	"time"
+	"unicode"
 )
 
 const (
@@ -31,6 +34,24 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	fmt.Fprintf(w, h.Body)
 }
 
+type MapHandler struct {
+	Status int
+	Bodies map[int]string
+}
+
+func (h *MapHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	// Parse out int key from URL path
+	key, err := strconv.Atoi(strings.TrimFunc(req.URL.Path, func(r rune) bool { return !unicode.IsNumber(r) }))
+	if err != nil {
+		w.WriteHeader(400)
+	} else if body := h.Bodies[key]; len(body) == 0 {
+		w.WriteHeader(404)
+	} else {
+		w.WriteHeader(h.Status)
+		fmt.Fprintf(w, body)
+	}
+}
+
 type ServerConfig struct {
 	*FixedResponses
 }
@@ -45,7 +66,7 @@ func NewServer(opts ...Option) *httptest.Server {
 		o(&config)
 	}
 
-	routes := map[string]*Handler{
+	routes := map[string]http.Handler{
 		// For CreateRegistrationToken
 		"/repos/test/valid/actions/runners/registration-token": &Handler{
 			Status: http.StatusCreated,
@@ -126,6 +147,9 @@ func NewServer(opts ...Option) *httptest.Server {
 
 		// For auto-scaling based on the number of queued(pending) workflow runs
 		"/repos/test/valid/actions/runs": config.FixedResponses.ListRepositoryWorkflowRuns,
+
+		// For auto-scaling based on the number of queued(pending) workflow jobs
+		"/repos/test/valid/actions/runs/": config.FixedResponses.ListWorkflowJobs,
 	}
 
 	mux := http.NewServeMux()

github/fake/options.go

@@ -2,6 +2,7 @@ package fake
 
 type FixedResponses struct {
 	ListRepositoryWorkflowRuns *Handler
+	ListWorkflowJobs           *MapHandler
 }
 
 type Option func(*ServerConfig)
@@ -15,6 +16,15 @@ func WithListRepositoryWorkflowRunsResponse(status int, body string) Option {
 	}
 }
 
+func WithListWorkflowJobsResponse(status int, bodies map[int]string) Option {
+	return func(c *ServerConfig) {
+		c.FixedResponses.ListWorkflowJobs = &MapHandler{
+			Status: status,
+			Bodies: bodies,
+		}
+	}
+}
+
 func WithFixedResponses(responses *FixedResponses) Option {
 	return func(c *ServerConfig) {
 		c.FixedResponses = responses