/*
TShock, a server mod for Terraria
Copyright (C) 2011-2019 Pryaxis & TShock Contributors

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

using System;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics.CodeAnalysis;
using Microsoft.Data.Sqlite;
using MySql.Data.MySqlClient;
using Npgsql;
using TShockAPI.DB.Queries;

namespace TShockAPI.DB
{
	/// <summary>
	/// Database extensions
	/// </summary>
	public static class DbExt
	{
		/// <summary>
		/// Executes a query on a database.
		/// </summary>
		/// <param name="olddb">Database to query</param>
		/// <param name="query">Query string with parameters as @0, @1, etc.</param>
		/// <param name="args">Parameters to be put in the query</param>
		/// <returns>Rows affected by query</returns>
		[SuppressMessage("Microsoft.Security", "CA2100:Review SQL queries for security vulnerabilities")]
		public static int Query(this IDbConnection olddb, string query, params object[] args)
		{
			using (var db = olddb.CloneEx())
			{
				db.Open();
				using (var com = db.CreateCommand())
				{
					com.CommandText = query;
					for (int i = 0; i < args.Length; i++)
						com.AddParameter("@" + i, args[i] ?? DBNull.Value);
					return com.ExecuteNonQuery();
				}
			}
		}

		/// <summary>
		/// Executes a query on a database.
		/// </summary>
		/// <param name="olddb">Database to query</param>
		/// <param name="query">Query string with parameters as @0, @1, etc.</param>
		/// <param name="args">Parameters to be put in the query</param>
		/// <returns>Query result as IDataReader</returns>
		[SuppressMessage("Microsoft.Security", "CA2100:Review SQL queries for security vulnerabilities")]
		public static QueryResult QueryReader(this IDbConnection olddb, string query, params object[] args)
		{
			var db = olddb.CloneEx();
			try
			{
				db.Open();
				var com = db.CreateCommand(); // this will be disposed via the QueryResult instance
				{
					com.CommandText = query;
					for (int i = 0; i < args.Length; i++)
						com.AddParameter("@" + i, args[i]);

					return new QueryResult(db, com.ExecuteReader(), com);
				}
			}
			catch (Exception ex)
			{
				throw new Exception(GetString("Fatal TShock initialization exception: failed to connect to MySQL database. See inner exception for details."), ex);
			}
		}

		/// <summary>
		/// Executes a query on a database, returning the first column of the first row of the result set.
		/// </summary>
		/// <typeparam name="T"></typeparam>
		/// <param name="olddb">Database to query</param>
		/// <param name="query">Query string with parameters as @0, @1, etc.</param>
		/// <param name="args">Parameters to be put in the query</param>
		/// <returns></returns>
		public static T QueryScalar<T>(this IDbConnection olddb, string query, params object[] args)
		{
			using (var db = olddb.CloneEx())
			{
				db.Open();
				using (var com = db.CreateCommand())
				{
					com.CommandText = query;
					for (int i = 0; i < args.Length; i++)
						com.AddParameter("@" + i, args[i]);

					object output = com.ExecuteScalar();
					if (output.GetType() != typeof(T))
					{
						if (typeof(IConvertible).IsAssignableFrom(output.GetType()))
						{
							return (T)Convert.ChangeType(output, typeof(T));
						}
					}

					return (T)output;
				}
			}
		}

		public static QueryResult QueryReaderDict(this IDbConnection olddb, string query, Dictionary<string, object> values)
		{
			var db = olddb.CloneEx();
			db.Open();
			var com = db.CreateCommand(); // this will be disposed via the QueryResult instance
			{
				com.CommandText = query;
				foreach (var kv in values)
					com.AddParameter("@" + kv.Key, kv.Value);

				return new QueryResult(db, com.ExecuteReader(), com);
			}
		}

		public static IDbDataParameter AddParameter(this IDbCommand command, string name, object data)
		{
			var parm = command.CreateParameter();
			parm.ParameterName = name;
			parm.Value = data;
			command.Parameters.Add(parm);
			return parm;
		}

		public static IDbConnection CloneEx(this IDbConnection conn)
		{
			var clone = (IDbConnection)Activator.CreateInstance(conn.GetType());
			clone.ConnectionString = conn.ConnectionString;
			return clone;
		}

		public static SqlType GetSqlType(this IDbConnection conn) => conn switch
		{
			SqliteConnection => SqlType.Sqlite,
			MySqlConnection => SqlType.Mysql,
			NpgsqlConnection => SqlType.Postgres,
			_ => SqlType.Unknown
		};

		public static IQueryBuilder GetSqlQueryBuilder(this IDbConnection db) => db.GetSqlType() switch
		{
			SqlType.Sqlite => new SqliteQueryCreator(),
			SqlType.Mysql => new MysqlQueryCreator(),
			SqlType.Postgres => new PostgresQueryCreator(),
			_ => throw new NotSupportedException("Database type not supported.")
		};

		private static readonly Dictionary<Type, Func<IDataReader, int, object>> ReadFuncs = new Dictionary
			<Type, Func<IDataReader, int, object>>
		{
			{
				typeof (bool),
				(s, i) => s.GetBoolean(i)
			},
			{
				typeof (bool?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetBoolean(i)
			},
			{
				typeof (byte),
				(s, i) => s.GetByte(i)
			},
			{
				typeof (byte?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetByte(i)
			},
			{
				typeof (Int16),
				(s, i) => s.GetInt16(i)
			},
			{
				typeof (Int16?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetInt16(i)
			},
			{
				typeof (Int32),
				(s, i) => s.GetInt32(i)
			},
			{
				typeof (Int32?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetInt32(i)
			},
			{
				typeof (Int64),
				(s, i) => s.GetInt64(i)
			},
			{
				typeof (Int64?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetInt64(i)
			},
			{
				typeof (string),
				(s, i) => s.GetString(i)
			},
			{
				typeof (decimal),
				(s, i) => s.GetDecimal(i)
			},
			{
				typeof (decimal?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetDecimal(i)
			},
			{
				typeof (float),
				(s, i) => s.GetFloat(i)
			},
			{
				typeof (float?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetFloat(i)
			},
			{
				typeof (double),
				(s, i) => s.GetDouble(i)
			},
			{
				typeof (double?),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetDouble(i)
			},
			{
				typeof (DateTime),
				(s, i) => s.IsDBNull(i) ? null : (object)s.GetDateTime(i)
			},
			{
				typeof (object),
				(s, i) => s.GetValue(i)
			},
		};

		public static T Get<T>(this IDataReader reader, string column)
		{
			return reader.Get<T>(reader.GetOrdinal(column));
		}

		public static T Get<T>(this IDataReader reader, int column)
		{
			if (reader.IsDBNull(column))
				return default;

			if (ReadFuncs.ContainsKey(typeof(T)))
				return (T)ReadFuncs[typeof(T)](reader, column);

			Type t;
			if (typeof(T) != (t = reader.GetFieldType(column)))
			{
				string columnName = reader.GetName(column);
				throw new InvalidCastException(GetString($"Received type '{typeof(T).Name}', however column '{columnName}' expects type '{t.Name}'"));
			}

			if (reader.IsDBNull(column))
			{
				return default;
			}

			return (T)reader.GetValue(column);
		}
	}

	public enum SqlType
	{
		Unknown,
		Sqlite,
		Mysql,
		Postgres
	}

	public class QueryResult : IDisposable
	{
		public IDbConnection Connection { get; protected set; }
		public IDataReader Reader { get; protected set; }
		public IDbCommand Command { get; protected set; }

		public QueryResult(IDbConnection conn, IDataReader reader, IDbCommand command)
		{
			Connection = conn;
			Reader = reader;
			Command = command;
		}

		~QueryResult()
		{
			Dispose(false);
		}

		public void Dispose()
		{
			Dispose(true);
			GC.SuppressFinalize(this);
		}

		protected virtual void Dispose(bool disposing)
		{
			if (disposing)
			{
				if (Reader != null)
				{
					Reader.Dispose();
					Reader = null;
				}
				if (Command != null)
				{
					Command.Dispose();
					Command = null;
				}
				if (Connection != null)
				{
					Connection.Dispose();
					Connection = null;
				}
			}
		}

		public bool Read()
		{
			if (Reader == null)
				return false;
			return Reader.Read();
		}

		public T Get<T>(string column)
		{
			if (Reader == null)
				return default(T);
			return Reader.Get<T>(Reader.GetOrdinal(column));
		}
	}
}