Database-Attribute_System/Database-Attribute_System/QueryBuilder.cs

using eu.railduction.netcore.dll.Database_Attribute_System.Attributes;
using System;
using System.Collections.Generic;
using System.Reflection;

namespace eu.railduction.netcore.dll.Database_Attribute_System
{
    public class QueryBuilder
    {
        /// <summary>
        /// Builds an SELECT-Sql-query based on an object<para/>
        /// Object needs to have at least 1 primary-key!
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="classObject">Given object (marked with Db-attributes)</param>
        /// <returns>SELECT-Sql-query</returns>
        public static string SelectByPrimaryKey<T>(T classObject)
        {
            Type classType = classObject.GetType();

            // Get db-table-name from class
            string tableName = Function.GetDbTableName(classType);

            // Get class db-fields
            Dictionary<string, object> dbPrimaryKeys = new Dictionary<string, object>() { };
            Dictionary<string, object> dbAttributes = new Dictionary<string, object>() { };
            Dictionary<string, object> dbForeignKeys = new Dictionary<string, object>() { };
            Function.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
            if (dbPrimaryKeys.Count == 0) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. No primary-key/s found!");

            // Build where statements with primaryKey/s
            object[] param = DbFunction.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
            // Add SQL-command part
            param[0] = $"SELECT * FROM {tableName} WHERE "+ param[0];
            
            // Build and return the query
            return BuildQuery(param);
        }

        /// <summary>
        /// Builds an UPDATE-Sql-query based on an object<para/>
        /// Object needs to have at least 1 primary-key!
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="classObject">Given object (marked with Db-attributes)</param>
        /// <returns>UPDATE-Sql-query</returns>
        public static string UpdateByPrimaryKey<T>(T classObject)
        {
            Type classType = classObject.GetType();

            // Get db-table-name from class
            string tableName = Function.GetDbTableName(classType);

            // Get class db-fields
            Dictionary<string, object> dbPrimaryKeys = new Dictionary<string, object>() { };
            Dictionary<string, object> dbAttributes = new Dictionary<string, object>() { };
            Dictionary<string, object> dbForeignKeys = new Dictionary<string, object>() { };
            Function.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
            if (dbPrimaryKeys.Count == 0) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. No primary-key/s found!");

            // Add foreign-keys to attributes
            foreach (KeyValuePair<string, object> dbForeignKey in dbForeignKeys)
            {
                dbAttributes.Add(dbForeignKey.Key, dbForeignKey.Value);
            }

            // Build set-parameters
            object[] paramSet = DbFunction.BuildKeyEqualQuery(dbAttributes, ", ");
            // Add SQL-command part
            paramSet[0] = $"UPDATE {tableName} SET "+ paramSet[0];

            // Build where-parameters
            object[] paramWhere = DbFunction.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
            // Add SQL-command part
            paramWhere[0] = " WHERE "+ paramWhere[0];

            // Build and return the query
            return BuildQuery(paramSet, paramWhere);
        }

        /// <summary>
        /// Builds an DELETE-Sql-query based on an object<para/>
        /// Object needs to have at least 1 primary-key!
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="classObject">Given object (marked with Db-attributes)</param>
        /// <returns>DELETE-Sql-query</returns>
        public static string DeleteByPrimaryKey<T>(T classObject)
        {
            Type classType = classObject.GetType();

            // Get db-table-name from class
            string tableName = Function.GetDbTableName(classType);

            // Get class db-fields
            Dictionary<string, object> dbPrimaryKeys = new Dictionary<string, object>() { };
            Dictionary<string, object> dbAttributes = new Dictionary<string, object>() { };
            Dictionary<string, object> dbForeignKeys = new Dictionary<string, object>() { };
            Function.ReadDbClassFields(classObject, ref dbPrimaryKeys, ref dbAttributes, ref dbForeignKeys);
            if (dbPrimaryKeys.Count == 0) throw new InvalidOperationException($"Cannot generate SQL-Query of '{classType.Name}'. No primary-key/s found!");

            // Build where-parameters
            object[] paramWhere = DbFunction.BuildKeyEqualQuery(dbPrimaryKeys, " AND ");
            // Add SQL-command part
            paramWhere[0] = $"DELETE FROM {tableName} WHERE "+ paramWhere[0];

            // Build and return the query
            return BuildQuery(paramWhere);
        }



        /// <summary>
        /// Build an SQL-query<para/>
        /// Will build the query-string based on the <paramref name="param"/>s including serialising and escaping for SQL.<para/>
        /// (Supported-Types: null, string, byte, int, float, double, DateTime, Guid)
        /// </summary>
        /// <param name="param">Params with alternating query-parts and objects beginning with a query-part
        /// <para/>Example: "SELECT * FROM table WHERE id=", id, " AND name=", name<para/>
        /// Info: Any object[] will be opened recursively and added as <paramref name="param"/> accordingly!
        /// </param>
        public static string BuildQuery(params object[] param)
        {
            // Convert array to list and add object[] to it recursively
            List<object> paramz = new List<object>() { };
            Function.RecursiveParameterCopying(ref paramz, (object[])param);

            string query = "";
            for (int i = 0; i < paramz.Count; i++)
            {
                if (i % 2 == 0) query += paramz[i];  // Every 'even' count will just add
                else       // Every 'uneven' count will handle param as passed variable    
                {
                    string paramString = Function.SqlSerialise(paramz[i]);
                    if(paramString == null)        // Unknown type in params
                        throw new Exception($"Error in query-builder. Type '{paramz[i].GetType().ToString()}' cannot be serialised!");

                    // Add formed param to query
                    query += paramString;
                }
            }

            // return built query
            return query;
        }
    }
}