From c9449f4088f8b2403dbddde4d48aab5772a66d56 Mon Sep 17 00:00:00 2001
From: Matthew Richards <matthew.richards@stfc.ac.uk>
Date: Thu, 19 Sep 2024 15:02:08 +0000
Subject: [PATCH] Add class to handle queries which should be done by reader
 account

---
 .../icat/reader_query_handler.py              | 84 +++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 datagateway_api/src/datagateway_api/icat/reader_query_handler.py

diff --git a/datagateway_api/src/datagateway_api/icat/reader_query_handler.py b/datagateway_api/src/datagateway_api/icat/reader_query_handler.py
new file mode 100644
index 00000000..24f0703e
--- /dev/null
+++ b/datagateway_api/src/datagateway_api/icat/reader_query_handler.py
@@ -0,0 +1,84 @@
+import logging
+
+from datagateway_api.src.common.config import Config
+from datagateway_api.src.common.filter_order_handler import FilterOrderHandler
+from datagateway_api.src.datagateway_api.icat.filters import PythonICATWhereFilter
+from datagateway_api.src.datagateway_api.icat.query import ICATQuery
+
+log = logging.getLogger()
+
+
+class ReaderQueryHandler:
+    # TODO - better names and comments on dicts to explain what they're for
+    # TODO - add docstrings
+    entity_filter_check = {"Datafile": "dataset.id", "Dataset": "investigation.id"}
+    entity_type_check = {"Datafile": "Dataset", "Dataset": "Investigation"}
+
+    def __init__(self, entity_type, filters):
+        self.entity_type = entity_type
+        self.filters = filters
+        log.debug(
+            "Instance of ReaderQueryHandler created for a '%s' request",
+            self.entity_type,
+        )
+        self.reader_query_eligible = self.check_eligibility()
+
+    def check_eligibility(self):
+        if not Config.config.datagateway_api.use_reader_for_performance.enabled:
+            return False
+
+        log.info("Checking whether query is eligible to go via reader account")
+        if self.entity_type in ReaderQueryHandler.entity_filter_check.keys():
+            if self.get_where_filter_for_entity_id_check():
+                return True
+
+        return False
+
+    def is_query_eligible_for_reader_performance(self):
+        return self.reader_query_eligible
+
+    def get_where_filter_for_entity_id_check(self):
+        for query_filter in self.filters:
+            if (
+                isinstance(query_filter, PythonICATWhereFilter)
+                and query_filter.field
+                == ReaderQueryHandler.entity_filter_check[self.entity_type]
+                and query_filter.operation == "eq"
+            ):
+                log.debug(
+                    "WHERE filter relevant for reader query checking: %s", query_filter,
+                )
+                self.where_filter_entity_id = query_filter.value
+                return query_filter
+
+        return None
+
+    def is_user_authorised_to_see_entity_id(self, client):
+        log.info(
+            "Checking to see if user '%s' can see '%s' = %s",
+            client.getUserName(),
+            ReaderQueryHandler.entity_filter_check[self.entity_type],
+            self.where_filter_entity_id,
+        )
+        access_query = ICATQuery(client, self.entity_type)
+        id_check = PythonICATWhereFilter("id", self.where_filter_entity_id, "eq")
+        access_filter_handler = FilterOrderHandler()
+        access_filter_handler.manage_icat_filters([id_check], access_query.query)
+        results = access_query.execute_query(client)
+
+        if results:
+            log.debug(
+                "User is authorised to see '%s' '%s'",
+                ReaderQueryHandler.entity_filter_check[self.entity_type],
+                self.where_filter_entity_id,
+            )
+            user_authorised = True
+        else:
+            log.debug(
+                "User is NOT authorised to see '%s' '%s'",
+                ReaderQueryHandler.entity_filter_check[self.entity_type],
+                self.where_filter_entity_id,
+            )
+            user_authorised = False
+
+        return user_authorised