textutil

var FuncHelp = []string{
	"indent <size>: add spaces to beginning of each line",
	"missing <message>: return message if the text is empty",
}

var TemplateFuncMap = template.FuncMap{
	"json": func(v interface{}) string {
		var b bytes.Buffer
		enc := json.NewEncoder(&b)
		enc.SetEscapeHTML(false)
		if err := enc.Encode(v); err != nil {
			panic(fmt.Errorf("failed to marshal as JSON: %+v: %w", v, err))
		}
		return strings.TrimSuffix(b.String(), "\n")
	},
	"yaml": func(v interface{}) string {
		var b bytes.Buffer
		enc := yaml.NewEncoder(&b)
		if err := enc.Encode(v); err != nil {
			panic(fmt.Errorf("failed to marshal as YAML: %+v: %w", v, err))
		}
		return "---\n" + strings.TrimSuffix(b.String(), "\n")
	},
	"indent": func(a ...interface{}) (string, error) {
		if len(a) == 0 {
			return "", errors.New("function takes at least one string argument")
		}
		if len(a) > 2 {
			return "", errors.New("function takes at most 2 arguments")
		}
		var ok bool
		size := 2
		if len(a) > 1 {
			if size, ok = a[0].(int); !ok {
				return "", errors.New("optional first argument must be an integer")
			}
		}
		text := ""
		if text, ok = a[len(a)-1].(string); !ok {
			return "", errors.New("last argument must be a string")
		}
		return IndentString(size, text), nil
	},
	"missing": func(a ...interface{}) (string, error) {
		if len(a) == 0 {
			return "", errors.New("function takes at least one string argument")
		}
		if len(a) > 2 {
			return "", errors.New("function takes at most 2 arguments")
		}
		var ok bool
		message := "<missing>"
		if len(a) > 1 {
			if message, ok = a[0].(string); !ok {
				return "", errors.New("optional first argument must be a string")
			}
		}
		text := ""
		if text, ok = a[len(a)-1].(string); !ok {
			return "", errors.New("last argument must be a string")
		}
		return MissingString(message, text), nil
	},
}