split() and substr() functions

CHANGELOG.md

@@ -10,6 +10,7 @@ Unreleased changes are available as `avenga/couper:edge` container.
   * Log file descriptor limit at startup ([#383](https://github.com/avenga/couper/pull/383))
   * [`error_handler`](/docs/ERRORS.md) block support for `api` and `endpoint` blocks ([#317](https://github.com/avenga/couper/pull/317))
     * Enables reacting to additional [error types](/docs/ERRORS.md#error-types): `beta_scope`, `beta_insufficient_scope` and `beta_operation_denied`
+  * `split()` and `substr()`[./docs/REFERENCE.md#functions] ([#390](https://github.com/avenga/couper/pull/390))
 
 * **Changed**
   * [`server` block](./docs/REFERENCE.md#server-block) label is now optional, [`api` block](./docs/REFERENCE.md#api-block) may be labelled ([#358](https://github.com/avenga/couper/pull/358))

docs/REFERENCE.md

@@ -673,6 +673,8 @@ To access the HTTP status code of the `default` response use `backend_responses.
 | `beta_oauth_verifier`          | string          | Creates a cryptographically random key as specified in RFC 7636, applicable for all verifier methods; e.g. to be set as a cookie and read into `verifier_value`. Multiple calls of this function in the same client request context return the same value.                                           |                                     | `beta_oauth_verifier()`                         |
 | `relative_url`                 | string          | Returns a relative URL by retaining `path`, `query` and `fragment` components.  The input URL `s` must begin with `/<path>`, `//<authority>`, `http://` or `https://`, otherwise an error is thrown. | s (string) | `relative_url("https://httpbin.org/anything?query#fragment") // returns "/anything?query#fragment"` |
 | `saml_sso_url`                 | string          | Creates a SAML SingleSignOn URL (including the `SAMLRequest` parameter) from a referenced [SAML Block](#saml-block).                                                                                                                                                                                 | `label` (string)                    | `saml_sso_url("mySAML")`                             |
+| `split`                        | tuple           | Divides a given string by a given separator, returning a list of strings containing the characters between the separator sequences.                                                                                                                                                                  | `sep` (string), `str` (string)      | `split(" ", "foo bar qux")`                          |
+| `substr`                       | string          | Extracts a sequence of characters from another string and creates a new string. The "`offset`" index may be negative, in which case it is relative to the end of the given string. The "`length`" may be `-1`, in which case the remainder of the string after the given offset will be returned.    | `str` (string), `offset` (integer), `length` (integer) | `substr("abcdef", 3, -1)`         |
 | `to_lower`                     | string          | Converts a given string to lowercase.                                                                                                                                                                                                                                                                | `s` (string)                        | `to_lower(request.cookies.name)`                     |
 | `to_upper`                     | string          | Converts a given string to uppercase.                                                                                                                                                                                                                                                                | `s` (string)                        | `to_upper("CamelCase")`                              |
 | `unixtime`                     | integer         | Retrieves the current UNIX timestamp in seconds.                                                                                                                                                                                                                                                     |                                     | `unixtime()`                                         |

eval/context.go

@@ -499,6 +499,8 @@ func newFunctionsMap() map[string]function.Function {
 		"json_encode":   stdlib.JSONEncodeFunc,
 		"merge":         lib.MergeFunc,
 		"relative_url":  lib.RelativeUrlFunc,
+		"split":         stdlib.SplitFunc,
+		"substr":        stdlib.SubstrFunc,
 		"to_lower":      stdlib.LowerFunc,
 		"to_upper":      stdlib.UpperFunc,
 		"unixtime":      lib.UnixtimeFunc,