Exports POC

lib/exports.nix

@@ -0,0 +1,88 @@
+{ lib }:
+let
+  /**
+    Creates a scope string for global exports
+
+    At least one of serviceName or machineName must be set.
+
+    The scope string has the format:
+
+    "/SERVICE/INSTANCE/ROLE/MACHINE"
+
+    If the parameter is not set, the corresponding part is left empty.
+    Semantically this means "all".
+
+    Examples:
+    mkScope { serviceName = "A"; }
+    -> "/A///"
+
+    mkScope { machineName = "jon"; }
+    -> "///jon"
+
+    mkScope { serviceName = "A"; instanceName = "i1"; roleName = "peer"; machineName = "jon"; }
+    -> "/A/i1/peer/jon"
+  */
+  mkScope =
+    {
+      serviceName ? "",
+      instanceName ? "",
+      roleName ? "",
+      machineName ? "",
+    }:
+    let
+      parts = [
+        serviceName
+        instanceName
+        roleName
+        machineName
+      ];
+      checkedParts = lib.map (
+        part:
+        lib.throwIf (builtins.match ".?/.?" part != null) ''
+          clanLib.exports.mkScope: ${part} cannot contain the "/" character
+        ''
+      ) parts;
+    in
+    lib.throwIf ((serviceName == "" && machineName == "")) ''
+      clanLib.exports.mkScope requires at least 'serviceName' or 'machineName' to be set
+
+      In case your use case requires neither
+    '' (lib.join "/" checkedParts);
+
+  /**
+    Parses a scope string into its components
+
+    Returns an attribute set with the keys:
+    - serviceName
+    - instanceName
+    - roleName
+    - machineName
+
+    Example:
+    parseScope "A/i1/peer/jon"
+    ->
+    {
+      serviceName = "A";
+      instanceName = "i1";
+      roleName = "peer";
+      machineName = "jon";
+    }
+  */
+  parseScope =
+    scopeStr:
+    let
+      parts = lib.splitString "/" scopeStr;
+      checkedParts = lib.throwIf (lib.length parts != 4) ''
+        clanLib.exports.parseScope: invalid scope string format, expected 4 parts separated by 3 "/"
+      '' (parts);
+    in
+    {
+      serviceName = lib.elemAt 0 checkedParts;
+      instanceName = lib.elemAt 1 checkedParts;
+      roleName = lib.elemAt 2 checkedParts;
+      machineName = lib.elemAt 3 checkedParts;
+    };
+in
+{
+  inherit mkScope parseScope;
+}