workspaces: add default workspace and validate user workspace choice

Add default workspace as an environmental variable coming from the cluster deployment choice.
The validation is done centralized in the validate_workspace function

Closes reanahub/reana-client#546

reana_commons/config.py

@@ -336,6 +336,20 @@ def kubernetes_node_label_to_dict(node_label):
 SHARED_VOLUME_PATH = os.getenv("SHARED_VOLUME_PATH", "/var/reana")
 """Default shared volume path."""
 
+DEFAULT_WORKSPACE_PATH = os.getenv("DEFAULT_WORKSPACE_PATH", SHARED_VOLUME_PATH)
+"""Default workspace path defined by the admin."""
+
+
+def workspaces(workspaces_list):
+    """Load the available workspaces as list."""
+    workspaces_list = workspaces_list.split(",") if workspaces_list else []
+    workspaces_list.append(SHARED_VOLUME_PATH)
+    return workspaces_list
+
+
+WORKSPACE_PATHS = workspaces(os.getenv("WORKSPACE_PATHS"))
+"""List of allowed workspace paths."""
+
 K8S_CERN_EOS_MOUNT_CONFIGURATION = {
     "volume": {"name": "eos", "hostPath": {"path": "/var/eos"}},
     "volumeMounts": {

reana_commons/openapi_specifications/reana_server.json

@@ -272,6 +272,52 @@
         "summary": "Ping the server (healthcheck)"
       }
     },
+    "/api/workspaces": {
+      "get":{
+        "consumes": [
+          "application/json"
+        ],
+        "description": "Get the list of available workspaces.",
+        "operationId": "workspaces",
+        "produces": [
+          "application/json"
+        ],
+        "responses": {
+          "200": {
+            "description": "This resource reports the available workspaces in the cluster.",
+            "examples": {
+              "application/json": {
+                "workspaces_available": ["/usr/share","/eos/home","/var/reana"],
+                "default": "/usr/share"
+              }
+            },
+            "schema": {
+              "properties": {
+                "workspaces_available": {
+                  "type": "array",
+                  "items": {
+                    "type":"string"
+                  }
+                },
+                "default": {
+                  "type": "string"
+                }
+              },
+              "type": "object"
+            }
+          },
+          "500": {
+            "description": "Request failed. Internal server error.",
+            "examples": {
+              "application/json": {
+                "message": "Internal server error."
+              }
+            }
+          }
+        },
+        "summary": "Get the list of available workspaces."
+      }
+    },
     "/api/secrets": {
       "get": {
         "description": "Get user secrets.",

reana_commons/workspaces.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+#
+# This file is part of REANA.
+# Copyright (C) 2021 CERN.
+#
+# REANA is free software; you can redistribute it and/or modify it
+# under the terms of the MIT License; see LICENSE file for more details.
+"""REANA-Commons workspaces util."""
+
+from reana_commons.errors import REANAValidationError
+from reana_commons.config import WORKSPACE_PATHS
+import os
+
+
+def validate_workspace(workspace_option, available_paths=WORKSPACE_PATHS):
+    """Validate and return workspace.
+
+    :param workspace_option: A string of the workspace.
+    :returns: A string of the validated workspace.
+    """
+    if workspace_option:
+        available = any(
+            os.path.abspath(workspace_option).startswith(os.path.abspath(path))
+            for path in available_paths
+        )
+        if not available:
+            raise REANAValidationError(
+                '==> ERROR: Workspace "{0}" not valid.'.format(workspace_option)
+            )
+    return workspace_option