From c579e2dd70736c693cf694438ed5981e1d83f051 Mon Sep 17 00:00:00 2001
From: Harpreet Sangar <happy_san@protonmail.com>
Date: Fri, 18 Aug 2023 12:07:54 +0530
Subject: [PATCH] Support `id` field for reference.

---
 src/collection.cpp            | 23 ++++++++++++++++++-----
 test/collection_join_test.cpp | 29 +++++++++++++++++++++++++++--
 2 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/src/collection.cpp b/src/collection.cpp
index 6d259e01..792ee826 100644
--- a/src/collection.cpp
+++ b/src/collection.cpp
@@ -126,18 +126,31 @@ Option<doc_seq_id_t> Collection::to_doc(const std::string & json_str, nlohmann::
             auto reference_collection_name = reference_pair.collection;
             auto reference_field_name = reference_pair.field;
             auto& cm = CollectionManager::get_instance();
-            auto collection = cm.get_collection(reference_collection_name);
-            if (collection == nullptr) {
+            auto ref_collection = cm.get_collection(reference_collection_name);
+            if (ref_collection == nullptr) {
                 return Option<doc_seq_id_t>(400, "Referenced collection `" + reference_collection_name
                                                                 + "` not found.");
             }
 
-            if (collection->get_schema().count(reference_field_name) == 0) {
+            if (reference_field_name == "id") {
+                auto value = document[field_name].get<std::string>();
+                auto ref_doc_id_op = ref_collection->doc_id_to_seq_id(value);
+                if (!ref_doc_id_op.ok()) {
+                    return Option<doc_seq_id_t>(400, "Referenced document having `id: " + value +
+                                                        "` not found in the collection `" +
+                                                        reference_collection_name + "`." );
+                }
+
+                document[field_name + REFERENCE_HELPER_FIELD_SUFFIX] = ref_doc_id_op.get();
+                continue;
+            }
+
+            if (ref_collection->get_schema().count(reference_field_name) == 0) {
                 return Option<doc_seq_id_t>(400, "Referenced field `" + reference_field_name +
                                                     "` not found in the collection `" + reference_collection_name + "`.");
             }
 
-            if (!collection->get_schema().at(reference_field_name).index) {
+            if (!ref_collection->get_schema().at(reference_field_name).index) {
                 return Option<doc_seq_id_t>(400, "Referenced field `" + reference_field_name +
                                                     "` in the collection `" + reference_collection_name + "` must be indexed.");
             }
@@ -145,7 +158,7 @@ Option<doc_seq_id_t> Collection::to_doc(const std::string & json_str, nlohmann::
             // Get the doc id of the referenced document.
             auto value = document[field_name].get<std::string>();
             filter_result_t filter_result;
-            collection->get_filter_ids(reference_field_name + ":=" + value, filter_result);
+            ref_collection->get_filter_ids(reference_field_name + ":=" + value, filter_result);
 
             if (filter_result.count != 1) {
                 auto match = " `" + reference_field_name + ": " + value + "` ";
diff --git a/test/collection_join_test.cpp b/test/collection_join_test.cpp
index 7ae07ce7..40c607ca 100644
--- a/test/collection_join_test.cpp
+++ b/test/collection_join_test.cpp
@@ -162,7 +162,7 @@ TEST_F(CollectionJoinTest, IndexDocumentHavingReferenceField) {
                     {"name": "customer_id", "type": "string"},
                     {"name": "customer_name", "type": "string"},
                     {"name": "product_price", "type": "float"},
-                    {"name": "reference_id", "type": "string", "reference": "Products.id"}
+                    {"name": "reference_id", "type": "string", "reference": "Products.foo"}
                 ]
             })"_json;
     collection_create_op = collectionManager.create_collection(customers_schema_json);
@@ -183,7 +183,7 @@ TEST_F(CollectionJoinTest, IndexDocumentHavingReferenceField) {
 
     add_doc_op = customer_collection->add(customer_json.dump());
     ASSERT_FALSE(add_doc_op.ok());
-    ASSERT_EQ("Referenced field `id` not found in the collection `Products`.", add_doc_op.error());
+    ASSERT_EQ("Referenced field `foo` not found in the collection `Products`.", add_doc_op.error());
     collectionManager.drop_collection("Customers");
 
     customers_schema_json =
@@ -294,8 +294,33 @@ TEST_F(CollectionJoinTest, IndexDocumentHavingReferenceField) {
     ASSERT_EQ(document["product_id"], "product_a");
     ASSERT_EQ(document["product_name"], "shampoo");
 
+    auto id_ref_schema_json =
+            R"({
+                "name": "id_ref",
+                "fields": [
+                    {"name": "reference", "type": "string", "reference": "Products.id"}
+                ]
+            })"_json;
+    collection_create_op = collectionManager.create_collection(id_ref_schema_json);
+    ASSERT_TRUE(collection_create_op.ok());
+
+    auto id_ref_collection = collection_create_op.get();
+    auto id_ref_json = R"({
+                            "reference": "foo"
+                        })"_json;
+    add_doc_op = id_ref_collection->add(id_ref_json.dump());
+    ASSERT_FALSE(add_doc_op.ok());
+    ASSERT_EQ("Referenced document having `id: foo` not found in the collection `Products`.", add_doc_op.error());
+
+    id_ref_json = R"({
+                        "reference": "1"
+                    })"_json;
+    add_doc_op = id_ref_collection->add(id_ref_json.dump());
+    ASSERT_TRUE(add_doc_op.ok());
+
     collectionManager.drop_collection("Customers");
     collectionManager.drop_collection("Products");
+    collectionManager.drop_collection("id_ref");
 }
 
 TEST_F(CollectionJoinTest, FilterByReference_SingleMatch) {