Introduce Valid Response Codes setting (#36)

In this pull-request I wanted to introduce valid-response-codes settings, that returns failed result, when response code of webhook is not among the list of valid codes. For goals of backwards compatibility, if this slice of valid-response-codes is empty, check is not performed.

README.md

@@ -34,6 +34,7 @@ docker run --rm \
   -e PLUGIN_HEADERS="HEADER1=value1" \
   -e PLUGIN_USERNAME=drone \
   -e PLUGIN_PASSWORD=password \
+  -e PLUGIN_VALID_RESPONSE_CODES="200,202,404" \
   -e DRONE_REPO_OWNER=octocat \
   -e DRONE_REPO_NAME=hello-world \
   -e DRONE_COMMIT_SHA=7fd1a60b01f91b314f59955a4e4d4e80d8edf11d \

main.go

@@ -57,6 +57,11 @@ func main() {
 			Usage:  "list of urls to perform the action on",
 			EnvVar: "PLUGIN_URLS,WEBHOOK_URLS",
 		},
+		cli.IntSliceFlag{
+			Name:   "valid-response-codes",
+			Usage:  "list of valid http response codes",
+			EnvVar: "PLUGIN_VALID_RESPONSE_CODES",
+		},
 		cli.BoolFlag{
 			Name:   "debug",
 			Usage:  "enable debug information",
@@ -184,6 +189,7 @@ func run(c *cli.Context) error {
 			Template:    c.String("template"),
 			Headers:     c.StringSlice("headers"),
 			URLs:        c.StringSlice("urls"),
+			ValidCodes:  c.IntSlice("valid-response-codes"),
 			Debug:       c.Bool("debug"),
 			SkipVerify:  c.Bool("skip-verify"),
 		},

plugin.go

@@ -43,6 +43,7 @@ type (
 		Template    string
 		Headers     []string
 		URLs        []string
+		ValidCodes  []int
 		Debug       bool
 		SkipVerify  bool
 	}
@@ -169,7 +170,22 @@ func (p Plugin) Exec() error {
 				)
 			}
 		}
+
+		if len(p.Config.ValidCodes) > 0 && !intInSlice(p.Config.ValidCodes, resp.StatusCode) {
+			return fmt.Errorf("Error: Response code %d not found among valid response codes", resp.StatusCode)
+		}
+
 	}
 
 	return nil
 }
+
+// Function checks if int is in slice of ints
+func intInSlice(s []int, e int) bool {
+	for _, a := range s {
+		if a == e {
+			return true
+		}
+	}
+	return false
+}