using Microsoft.Data.Sqlite;

namespace DataBase {
    
    public class DbDriver : IDisposable {
        
        static SqliteConnection? singletonConnector = null;

        public DbDriver() {
            // Load in the datastore if not already loaded
            if (singletonConnector == null) {
                singletonConnector = new SqliteConnection("Data Source=test.db");
                singletonConnector.Open();

                // Create the key value store if not exist
                using var command = singletonConnector.CreateCommand();
                command.CommandText = """
                    CREATE TABLE IF NOT EXISTS KeyValuePair (
                        key TEXT NOT NULL,
                        value TEXT,
                        PRIMARY KEY(key)
                    );
                """;
                command.ExecuteReader();
            }
        }

        // Return Values from keys
        public string Get(string Key) {
            if (singletonConnector != null) {
                using var command = singletonConnector.CreateCommand();
                command.CommandText = """
                    SELECT value
                    FROM KeyValuePair
                    Where key = $key;
                """;
                command.Parameters.AddWithValue("$key", Key);
                command.ExecuteReader();
                using var reader = command.ExecuteReader();
                if (reader.Read()) {
                    return reader.GetString(0);
                }
            }
            return "";
        }

        // Set a key value pair in the store
        public void Set(string Key, string Value) {
            if (singletonConnector != null) {
                using var command = singletonConnector.CreateCommand();
                command.CommandText = """
                    INSERT INTO KeyValuePair
                    (key,value)
                    VALUES
                    ($key, $value)
                    ON CONFLICT(key)
                    DO UPDATE
                    SET value = excluded.value;
                """;
                command.Parameters.AddWithValue("$key", Key);
                command.Parameters.AddWithValue("$value", Value);
                command.ExecuteReader();
            }
        }

        // Deconstructor
        ~DbDriver() {
            Dispose();
        }

        // Deconstructor
        public void Dispose() {
            if (singletonConnector != null) {
                singletonConnector.Close();
                singletonConnector = null;
            }
        }
    }

}