Additional functions in template

README.md

@@ -166,6 +166,9 @@ variables within a template with `.Env`.
 There are a few built in functions as well:
 
   * `default $var $default` - Returns a default value for one that does not exist. `{{ default .Env.VERSION "0.1.2" }}`
+  * `defaultEmpty $var $default` - Returns a default value for one that does not exist or is empty in case of string. `{{ default .Env.VERSION "0.1.2" }}`
+  * `required $val` Returns a value passed as argument or error if value does not exist. `{{ required .Env.VERSION }}` 
+  * `requiredEmpty $val` Returns a value passed as argument or error if value does not exist or is empty in case of string. `{{ requiredEmpty .Env.VERSION }}` 
   * `contains $map $key` - Returns true if a string is within another string
   * `exists $path` - Determines if a file path exists or not. `{{ exists "/etc/default/myapp" }}`
   * `split $string $sep` - Splits a string into an array using a separator string. Alias for [`strings.Split`][go.string.Split]. `{{ split .Env.PATH ":" }}`
@@ -178,6 +181,7 @@ There are a few built in functions as well:
   * `upper $value` - Uppercase a string.
   * `jsonQuery $json $query` - Returns the result of a selection query against a json document.
   * `loop` - Create for loops.
+  * `envSlice` - Returns the array filled with maps of environment variables passed as collection (variables that contains numeric suffix) and matched to $prefix `{{ envSlice "VARIABLE_NAME" }}`
 
 ### jsonQuery
 
@@ -224,6 +228,34 @@ i = {{ $i }}
 {{ end }}
 ```
 
+### envSlice
+
+`envSlice` can be useful if we want to pass multiple values of the same property by environment variables. It can be also used to pass different values with same index
+
+For variables:
+```
+EXAMPLEVAR_SUBVAR_1
+EXAMPLEVAR_SUBVAR_2
+EXAMPLEVAR_ANOTHERSUBVAR_1
+EXAMPLEVAR_ANOTHERSUBVAR_2
+```
+Let's assume that we call envSlice with $prefix = "EXAMPLEVAR". Function return an array. Each entry will have a map of variables that starts with `EXAMPLEVAR` and having same index
+Returned collection can be used in loop. For example:
+
+```
+{{ range $i := envSlice ("EXAMPLEVAR") }}
+
+subvar value: {{ $i.EXAMPLEVAR_SUBVAR }}
+anotherSubvar value: {{ $i.EXAMPLEVAR_ANOTHERSUBVAR }}
+
+---
+
+```
+
+##### Limitations
+Note that the last index of array will be highest index found in variables matched by prefix. So if we define EXAMPLEVAR_1 and EXAMPLEVAR_100 the loop will be iterate 100 times with filled values only in first and last index
+
+
 ## License
 
 MIT

template.go

@@ -33,30 +33,70 @@ func contains(item map[string]string, key string) bool {
 	return false
 }
 
+func _checkDefaultValueArgs(args interface{}) error {
+	vargs, _ := args.([]interface{})
+
+	if len(vargs) == 0 {
+		return fmt.Errorf("default called with no values!")
+	}
+
+	if len(vargs) < 2 {
+		return fmt.Errorf("default called with no default value")
+	}
+
+	if vargs[1] == nil {
+		return fmt.Errorf("default called with nil default value!")
+	}
+
+	if _, ok := vargs[1].(string); !ok {
+		return fmt.Errorf("default is not a string value. hint: surround it w/ double quotes.")
+	}
+
+	return nil
+}
+
 func defaultValue(args ...interface{}) (string, error) {
-	if len(args) == 0 {
-		return "", fmt.Errorf("default called with no values!")
+	if err := _checkDefaultValueArgs(args); err != nil {
+		return "", err
 	}
 
-	if len(args) > 0 {
-		if args[0] != nil {
-			return args[0].(string), nil
-		}
+	if args[0] != nil {
+		return args[0].(string), nil
 	}
 
-	if len(args) > 1 {
-		if args[1] == nil {
-			return "", fmt.Errorf("default called with nil default value!")
-		}
+	return args[1].(string), nil
+}
 
-		if _, ok := args[1].(string); !ok {
-			return "", fmt.Errorf("default is not a string value. hint: surround it w/ double quotes.")
-		}
+func defaultValueEmpty(args ...interface{}) (string, error) {
+	if err := _checkDefaultValueArgs(args); err != nil {
+		return "", err
+	}
 
+	if args[0] == nil || len(args[0].(string)) == 0 {
 		return args[1].(string), nil
 	}
 
-	return "", fmt.Errorf("default called with no default value")
+	return args[0].(string), nil
+}
+
+func requiredValue(val interface{}) (interface{}, error) {
+	if val != nil {
+		return val, nil
+	}
+
+	return nil, fmt.Errorf("Required value is nil")
+}
+
+func requiredValueEmpty(val interface{}) (interface{}, error) {
+	if _, err := requiredValue(val); err != nil {
+		return nil, err
+	}
+
+	if val, ok := val.(string); ok && len(val) == 0 {
+		return nil, fmt.Errorf("Required value is empty")
+	}
+
+	return val, nil
 }
 
 func parseUrl(rawurl string) *url.URL {
@@ -101,7 +141,7 @@ func loop(args ...int) (<-chan int, error) {
 	case 3:
 		start, stop, step = args[0], args[1], args[2]
 	default:
-		return nil, fmt.Errorf("wrong number of arguments, expected 1-3"+
+		return nil, fmt.Errorf("wrong number of arguments, expected 1-3" +
 			", but got %d", len(args))
 	}
 
@@ -115,21 +155,70 @@ func loop(args ...int) (<-chan int, error) {
 	return c, nil
 }
 
+func envSlice(envParamPrefix string) ([]map[string]interface{}, error) {
+	variables := make(map[string]interface{})
+
+	biggestIndex := 0
+
+	for _, i := range os.Environ() {
+		sep := strings.Index(i, "=")
+		key := i[0:sep]
+		val := i[sep + 1:]
+
+		if strings.HasPrefix(key, envParamPrefix) {
+			suffix := key[strings.LastIndex(key, "_") + 1:]
+			if num, ok := strconv.Atoi(suffix); ok == nil {
+				if biggestIndex < num {
+					biggestIndex = num
+				}
+				variables[key] = val
+			}
+		}
+	}
+
+	var result []map[string]interface{}
+	if biggestIndex > 0 {
+		result = make([]map[string]interface{}, biggestIndex)
+
+		for i := 0; i < biggestIndex; i++ {
+			result[i] = make(map[string]interface{})
+		}
+
+		for key, value := range variables {
+			indexStr := key[strings.LastIndex(key, "_") + 1:]
+			resultIndex, _ := strconv.Atoi(indexStr)
+			resultIndex -= 1
+			resultKey := key[0:strings.LastIndex(key, "_")]
+
+			result[resultIndex][resultKey] = value
+		}
+
+	} else {
+		result = make([]map[string]interface{}, 0)
+	}
+
+	return result, nil
+}
+
 func generateFile(templatePath, destPath string) bool {
 	tmpl := template.New(filepath.Base(templatePath)).Funcs(template.FuncMap{
-		"contains":  contains,
-		"exists":    exists,
-		"split":     strings.Split,
-		"replace":   strings.Replace,
-		"default":   defaultValue,
-		"parseUrl":  parseUrl,
-		"atoi":      strconv.Atoi,
-		"add":       add,
-		"isTrue":    isTrue,
-		"lower":     strings.ToLower,
-		"upper":     strings.ToUpper,
-		"jsonQuery": jsonQuery,
-		"loop":      loop,
+		"contains":      contains,
+		"exists":        exists,
+		"split":         strings.Split,
+		"replace":       strings.Replace,
+		"default":       defaultValue,
+		"defaultEmpty":  defaultValueEmpty,
+		"required":      requiredValue,
+		"requiredEmpty": requiredValueEmpty,
+		"parseUrl":      parseUrl,
+		"atoi":          strconv.Atoi,
+		"add":           add,
+		"isTrue":        isTrue,
+		"lower":         strings.ToLower,
+		"upper":         strings.ToUpper,
+		"jsonQuery":     jsonQuery,
+		"loop":          loop,
+		"envSlice":      envSlice,
 	})
 
 	if len(delims) > 0 {