Add additional template functions

closest, coalesce, first, groupByKeys and dir

README.md

@@ -105,9 +105,14 @@ Within those templates, the object emitted by docker-gen will have [this structu
 
 #### Functions
 
+* *`closest $array $value`: Returns the longest matching substring in `$array` that matches `$value`
+* *`coalesce ...`*: Returns the first non-nil argument.
 * *`contains $map $key`*: Returns `true` if `$map` contains `$key`. Takes maps from `string` to `string`.
+* *`dir $path`: Returns an array of filenames in the specified `$path`.
 * *`exists $path`*: Returns `true` if `$path` refers to an existing file or directory. Takes a string.
+* *`first $array`*: Returns the first value of an array or nil if the arry is nil or empty.
 * *`groupBy $containers $fieldPath`*: Groups an array of `RuntimeContainer` instances based on the values of a field path expression `$fieldPath`. A field path expression is a dot-delimited list of map keys or struct member names specifying the path from container to a nested value, which must be a string. Returns a map from the value of the field path expression to an array of containers having that value. Containers that do not have a value for the field path in question are omitted.
+* *`groupByKeys $containers $fieldPath`*: Returns the same as `groupBy` but only returns the keys of the map.
 * *`groupByMulti $containers $fieldPath $sep`*: Like `groupBy`, but the string value specified by `$fieldPath` is first split by `$sep` into a list of strings. A container whose `$fieldPath` value contains a list of strings will show up in the map output under each of those strings.
 * *`split $string $sep`*: Splits `$string` into a slice of substrings delimited by `$sep`. Alias for [`strings.Split`](http://golang.org/pkg/strings/#Split)
 * *`replace $string $old $new $count`*: Replaces up to `$count` occurences of `$old` with `$new` in `$string`. Alias for [`strings.Replace`](http://golang.org/pkg/strings/#Replace)

docker-gen.go

@@ -93,7 +93,6 @@ func (c *Context) Env() map[string]string {
 		env[parts[0]] = parts[1]
 	}
 	return env
-
 }
 
 func (c *ConfigFile) filterWatches() ConfigFile {

template.go

@@ -43,6 +43,7 @@ func groupByMulti(entries []*RuntimeContainer, key, sep string) map[string][]*Ru
 	return groups
 }
 
+// groupBy groups a list of *RuntimeContainers by the path property key
 func groupBy(entries []*RuntimeContainer, key string) map[string][]*RuntimeContainer {
 	groups := make(map[string][]*RuntimeContainer)
 	for _, v := range entries {
@@ -54,6 +55,16 @@ func groupBy(entries []*RuntimeContainer, key string) map[string][]*RuntimeConta
 	return groups
 }
 
+// groupByKeys is the same as groupBy but only returns a list of keys
+func groupByKeys(entries []*RuntimeContainer, key string) []string {
+	groups := groupBy(entries, key)
+	ret := []string{}
+	for k, _ := range groups {
+		ret = append(ret, k)
+	}
+	return ret
+}
+
 func contains(item map[string]string, key string) bool {
 	if _, ok := item[key]; ok {
 		return true
@@ -91,24 +102,81 @@ func marshalJson(input interface{}) (string, error) {
 	return strings.TrimSuffix(buf.String(), "\n"), nil
 }
 
+// arrayFirst returns first item in the array or nil if the
+// input is nil or empty
+func arrayFirst(input interface{}) interface{} {
+	if input == nil {
+		return nil
+	}
+
+	arr := reflect.ValueOf(input)
+
+	if arr.Len() == 0 {
+		return nil
+	}
+
+	return arr.Index(0).Interface()
+}
+
+// arrayLast returns last item in the array
 func arrayLast(input interface{}) interface{} {
 	arr := reflect.ValueOf(input)
 	return arr.Index(arr.Len() - 1).Interface()
 }
 
+// arrayClosest find the longest matching substring in values
+// that matches input
+func arrayClosest(values []string, input string) string {
+	best := ""
+	for _, v := range values {
+		if strings.Contains(input, v) && len(v) > len(best) {
+			best = v
+		}
+	}
+	return best
+}
+
+// dirList returns a list of files in the specified path
+func dirList(path string) ([]string, error) {
+	names := []string{}
+	files, err := ioutil.ReadDir(path)
+	if err != nil {
+		return names, err
+	}
+	for _, f := range files {
+		names = append(names, f.Name())
+	}
+	return names, nil
+}
+
+// coalesce returns the first non nil argument
+func coalesce(input ...interface{}) interface{} {
+	for _, v := range input {
+		if v != nil {
+			return v
+		}
+	}
+	return nil
+}
+
 func generateFile(config Config, containers Context) bool {
 	templatePath := config.Template
 	tmpl, err := template.New(filepath.Base(templatePath)).Funcs(template.FuncMap{
+		"closest":      arrayClosest,
+		"coalesce":     coalesce,
 		"contains":     contains,
 		"exists":       exists,
+		"first":        arrayFirst,
 		"groupBy":      groupBy,
 		"groupByMulti": groupByMulti,
+		"groupByKeys":  groupByKeys,
 		"split":        strings.Split,
 		"replace":      strings.Replace,
 		"dict":         dict,
 		"sha1":         hashSha1,
 		"json":         marshalJson,
 		"last":         arrayLast,
+		"dir":          dirList,
 	}).ParseFiles(templatePath)
 	if err != nil {
 		log.Fatalf("unable to parse template: %s", err)

template_test.go

@@ -183,3 +183,21 @@ func TestJson(t *testing.T) {
 		t.Fatal("Incorrect unmarshaled container count. Expected %d, got %d.", len(containers), len(decoded))
 	}
 }
+
+func TestArrayClosestExact(t *testing.T) {
+	if arrayClosest([]string{"foo.bar.com", "bar.com"}, "foo.bar.com") != "foo.bar.com" {
+		t.Fatal("Expected foo.bar.com")
+	}
+}
+
+func TestArrayClosestSubstring(t *testing.T) {
+	if arrayClosest([]string{"foo.fo.com", "bar.com"}, "foo.bar.com") != "bar.com" {
+		t.Fatal("Expected bar.com")
+	}
+}
+
+func TestArrayClosestNoMatch(t *testing.T) {
+	if arrayClosest([]string{"foo.fo.com", "bip.com"}, "foo.bar.com") != "" {
+		t.Fatal("Expected ''")
+	}
+}