[#1013] Implement the Database Adapter

src/BUILD

@@ -44,6 +44,7 @@ cc_shared_library(
         "//atomdb:atomdb_lib",
         "//attention_broker:attention_broker_lib",
         "//commons:commons_lib",
+        "//db_adapter:db_adapter_lib",
         "//distributed_algorithm_node:distributed_algorithm_node_lib",
         "//hasher:hasher_lib",
         "//metta:metta_lib",

src/commons/HandleTrie.cc

@@ -3,6 +3,7 @@
 #include <iostream>
 #include <stack>
 
+#include "Logger.h"
 #include "Utils.h"
 #include "expression_hasher.h"
 
@@ -26,7 +27,10 @@ HandleTrie::TrieNode::~TrieNode() {
         delete children[i];
     }
     delete[] children;
-    delete value;
+    if (value != NULL) {
+        delete value;
+        value = NULL;
+    }
 }
 
 string HandleTrie::TrieValue::to_string() { return ""; }
@@ -264,3 +268,8 @@ void HandleTrie::traverse(bool keep_root_locked,
         root->trie_node_mutex.unlock();
     }
 }
+
+bool HandleTrie::exists(const string& key) {
+    TrieNode* node = lookup_node(key);
+    return node != NULL ? true : false;
+}

src/commons/HandleTrie.h

@@ -74,6 +74,8 @@ class HandleTrie {
      */
     TrieValue* lookup(const string& key);
 
+    bool exists(const string& key);
+
     /**
      * Remove a key from this HandleTrie and its associated value.
      *

src/db_adapter/BUILD

@@ -0,0 +1,46 @@
+load("@rules_cc//cc:cc_library.bzl", "cc_library")
+
+package(default_visibility = ["//visibility:public"])
+
+cc_library(
+    name = "db_adapter_lib",
+    includes = ["."],
+    deps = [
+        ":data_mapper",
+        ":data_types",
+        ":db_wrapper",
+        "//db_adapter/postgres:postgres_lib",
+    ],
+)
+
+cc_library(
+    name = "data_mapper",
+    srcs = ["DataMapper.cc"],
+    hdrs = ["DataMapper.h"],
+    includes = ["."],
+    deps = [
+        "//commons:commons_lib",
+        "//commons/atoms:atoms_lib",
+    ],
+)
+
+cc_library(
+    name = "data_types",
+    hdrs = ["DataTypes.h"],
+    includes = ["."],
+    deps = [
+        "//commons:commons_lib",
+        "//commons/atoms:atoms_lib",
+    ],
+)
+
+cc_library(
+    name = "db_wrapper",
+    hdrs = ["DBWrapper.h"],
+    includes = ["."],
+    deps = [
+        ":data_types",
+        "//commons:commons_lib",
+        "//commons/atoms:atoms_lib",
+    ],
+)

src/db_adapter/DBWrapper.h

@@ -0,0 +1,98 @@
+#pragma once
+
+#include <memory>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+#include "DataMapper.h"
+
+using namespace std;
+using namespace db_adapter;
+
+namespace db_adapter {
+
+/**
+ * @class DatabaseWrapper
+ * @brief Generic interface for a database connection wrapper.
+ *
+ * @tparam ConnT The underlying connection object type (e.g., pqxx::connection).
+ */
+template <typename ConnT>
+class DatabaseWrapper {
+   public:
+    explicit DatabaseWrapper(shared_ptr<Mapper> mapper, MAPPER_TYPE mapper_type)
+        : mapper(move(mapper)), mapper_type(mapper_type) {}
+    virtual ~DatabaseWrapper() = default;
+
+    /**
+     * @brief Closes the connection.
+     */
+    virtual void disconnect() = 0;
+
+    unsigned int mapper_handle_trie_size() { return mapper->handle_trie_size(); }
+
+   protected:
+    /**
+     * @brief Establishes connection to the database.
+     */
+    virtual unique_ptr<ConnT> connect() = 0;
+
+    unique_ptr<ConnT> db_client;
+    shared_ptr<Mapper> mapper;
+    MAPPER_TYPE mapper_type;
+};
+
+/**
+ * @class SQLWrapper
+ * @brief Specialization of DatabaseWrapper for SQL-based databases.
+ */
+template <typename ConnT>
+class SQLWrapper : public DatabaseWrapper<ConnT> {
+   public:
+    explicit SQLWrapper(MAPPER_TYPE mapper_type)
+        : DatabaseWrapper<ConnT>(create_mapper(mapper_type), mapper_type) {}
+    virtual ~SQLWrapper() = default;
+
+    /**
+     * @brief Retrieves schema information for a specific table.
+     */
+    virtual Table get_table(const string& name) = 0;
+
+    /**
+     * @brief Lists all tables in the database.
+     */
+    virtual vector<Table> list_tables() = 0;
+
+    /**
+     * @brief Maps a table's data to the target format.
+     *
+     * @param table The table metadata.
+     * @param clauses Additional SQL WHERE clauses.
+     * @param skip_columns Columns to exclude from mapping.
+     * @param second_level Boolean flag for recursive/depth mapping logic.
+     */
+    virtual void map_table(const Table& table,
+                           const vector<string>& clauses,
+                           const vector<string>& skip_columns,
+                           bool second_level) = 0;
+
+    /**
+     * @brief Executes a raw SQL query and maps the result.
+     */
+    virtual void map_sql_query(const string& virtual_name, const string& raw_query) = 0;
+
+   private:
+    // Factory method for creating the specific mapper strategy
+    static shared_ptr<Mapper> create_mapper(MAPPER_TYPE mapper_type) {
+        switch (mapper_type) {
+            case MAPPER_TYPE::SQL2METTA:
+                return make_shared<SQL2MettaMapper>();
+            case MAPPER_TYPE::SQL2ATOMS:
+                return make_shared<SQL2AtomsMapper>();
+            default:
+                throw invalid_argument("Unknown mapper type");
+        }
+    }
+};
+}  // namespace db_adapter