using System;
using System.Collections.Generic;
using System.Linq;
using System.Data;
using System.Collections.Concurrent;
using System.Reflection;
using System.Text;
using System.Data.Common;
using System.Reflection.Emit;

namespace Dapper
{
    /// <summary>
    /// Represents a database, assumes all the tables have an Id column named Id
    /// </summary>
    /// <typeparam name="TDatabase">The type of database this represents.</typeparam>
    public abstract partial class Database<TDatabase> : IDisposable where TDatabase : Database<TDatabase>, new()
    {
        /// <summary>
        /// A database table of type <typeparamref name="T"/> and primary key of type <typeparamref name="TId"/>.
        /// </summary>
        /// <typeparam name="T">The type of object in this table.</typeparam>
        /// <typeparam name="TId">The type of the primary key for this table.</typeparam>
        public partial class Table<T, TId>
        {
            internal Database<TDatabase> database;
            internal string tableName;
            internal string likelyTableName;

            /// <summary>
            /// Creates a table in the specified database with a given name.
            /// </summary>
            /// <param name="database">The database this table belongs in.</param>
            /// <param name="likelyTableName">The name for this table.</param>
            public Table(Database<TDatabase> database, string likelyTableName)
            {
                this.database = database;
                this.likelyTableName = likelyTableName;
            }

            /// <summary>
            /// The name for this table.
            /// </summary>
            public string TableName
            {
                get
                {
                    tableName ??= database.DetermineTableName<T>(likelyTableName);
                    return tableName;
                }
            }

            /// <summary>
            /// Insert a row into the db
            /// </summary>
            /// <param name="data">Either DynamicParameters or an anonymous type or concrete type</param>
            /// <returns></returns>
            public virtual int? Insert(dynamic data)
            {
                var o = (object)data;
                List<string> paramNames = GetParamNames(o);
                paramNames.Remove("Id");

                string cols = string.Join(",", paramNames);
                string colsParams = string.Join(",", paramNames.Select(p => "@" + p));
                var sql = "set nocount on insert " + TableName + " (" + cols + ") values (" + colsParams + ") select cast(scope_identity() as int)";

                return database.Query<int?>(sql, o).Single();
            }

            /// <summary>
            /// Update a record in the database.
            /// </summary>
            /// <param name="id">The primary key of the row to update.</param>
            /// <param name="data">The new object data.</param>
            /// <returns>The number of rows affected.</returns>
            public int Update(TId id, dynamic data)
            {
                List<string> paramNames = GetParamNames((object)data);

                var builder = new StringBuilder();
                builder.Append("update ").Append(TableName).Append(" set ");
                builder.AppendLine(string.Join(",", paramNames.Where(n => n != "Id").Select(p => p + "= @" + p)));
                builder.Append("where Id = @Id");

                DynamicParameters parameters = new DynamicParameters(data);
                parameters.Add("Id", id);

                return database.Execute(builder.ToString(), parameters);
            }

            /// <summary>
            /// Delete a record for the DB
            /// </summary>
            /// <param name="id"></param>
            /// <returns></returns>
            public bool Delete(TId id)
            {
                return database.Execute("delete from " + TableName + " where Id = @id", new { id }) > 0;
            }

            /// <summary>
            /// Gets a record with a particular Id from the DB 
            /// </summary>
            /// <param name="id">The primary key of the table to fetch.</param>
            /// <returns>The record with the specified Id.</returns>
            public T Get(TId id)
            {
                return database.QueryFirstOrDefault<T>("select * from " + TableName + " where Id = @id", new { id });
            }

            /// <summary>
            /// Gets the first row from this table (order determined by the database provider).
            /// </summary>
            /// <returns>Data from the first table row.</returns>
            public virtual T First()
            {
                return database.QueryFirstOrDefault<T>("select top 1 * from " + TableName);
            }

            /// <summary>
            /// Gets the all rows from this table.
            /// </summary>
            /// <returns>Data from all table rows.</returns>
            public IEnumerable<T> All()
            {
                return database.Query<T>("select * from " + TableName);
            }

            private static readonly ConcurrentDictionary<Type, List<string>> paramNameCache = new ConcurrentDictionary<Type, List<string>>();

            internal static List<string> GetParamNames(object o)
            {
                if (o is DynamicParameters parameters)
                {
                    return parameters.ParameterNames.ToList();
                }

                if (!paramNameCache.TryGetValue(o.GetType(), out List<string> paramNames))
                {
                    paramNames = new List<string>();
                    foreach (var prop in o.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public).Where(p => p.GetGetMethod(false) != null))
                    {
                        var attribs = prop.GetCustomAttributes(typeof(IgnorePropertyAttribute), true);
#pragma warning disable IDE0019 // Use pattern matching - complex enough here
                        var attr = attribs.FirstOrDefault() as IgnorePropertyAttribute;
#pragma warning restore IDE0019 // Use pattern matching
                        if (attr == null || (!attr.Value))
                        {
                            paramNames.Add(prop.Name);
                        }
                    }
                    paramNameCache[o.GetType()] = paramNames;
                }
                return paramNames;
            }
        }

        /// <summary>
        /// A database table of type <typeparamref name="T"/> and primary key of type <see cref="int"/>.
        /// </summary>
        /// <typeparam name="T">The type of object in this table.</typeparam>
        public class Table<T> : Table<T, int>
        {
            /// <summary>
            /// Creates a table in the specified database with a given name.
            /// </summary>
            /// <param name="database">The database this table belongs in.</param>
            /// <param name="likelyTableName">The name for this table.</param>
			public Table(Database<TDatabase> database, string likelyTableName)
                : base(database, likelyTableName)
            {
            }
        }

        private DbConnection _connection;
        private int _commandTimeout;

        /// <summary>
        /// Get access to the underlying transaction
        /// </summary>
        public DbTransaction Transaction { get; private set; }

        /// <summary>
        /// Get underlying database connection.
        /// </summary>
        public DbConnection Connection => _connection;

        /// <summary>
        /// Initializes the database.
        /// </summary>
        /// <param name="connection">The connection to use.</param>
        /// <param name="commandTimeout">The timeout to use (in seconds).</param>
        /// <returns></returns>
        public static TDatabase Init(DbConnection connection, int commandTimeout)
        {
            TDatabase db = new TDatabase();
            db.InitDatabase(connection, commandTimeout);
            return db;
        }

        internal static Action<TDatabase> tableConstructor;

        internal void InitDatabase(DbConnection connection, int commandTimeout)
        {
            _connection = connection;
            _commandTimeout = commandTimeout;
            tableConstructor ??= CreateTableConstructorForTable();

            tableConstructor(this as TDatabase);
        }

        internal virtual Action<TDatabase> CreateTableConstructorForTable()
        {
            return CreateTableConstructor(typeof(Table<>), typeof(Table<,>));
        }

        /// <summary>
        /// Begins a transaction in this database.
        /// </summary>
        /// <param name="isolation">The isolation level to use.</param>
        /// <returns>The transaction created</returns>
        public DbTransaction BeginTransaction(IsolationLevel isolation = IsolationLevel.ReadCommitted)
        {
            Transaction = _connection.BeginTransaction(isolation);
            return Transaction;
        }

        /// <summary>
        /// Commits the current transaction in this database.
        /// </summary>
        public void CommitTransaction()
        {
            Transaction.Commit();
            Transaction = null;
        }

        /// <summary>
        /// Rolls back the current transaction in this database.
        /// </summary>
        public void RollbackTransaction()
        {
            Transaction.Rollback();
            Transaction = null;
        }

        /// <summary>
        /// Gets a table creation function for the specified type.
        /// </summary>
        /// <param name="tableType">The object type to create a table for.</param>
        /// <returns>The function to create the <paramref name="tableType"/> table.</returns>
        protected Action<TDatabase> CreateTableConstructor(Type tableType)
        {
            return CreateTableConstructor(new[] { tableType });
        }

        /// <summary>
        /// Gets a table creation function for the specified types.
        /// </summary>
        /// <param name="tableTypes">The object types to create a table for.</param>
        /// <returns>The function to create the <paramref name="tableTypes"/> tables.</returns>
        protected Action<TDatabase> CreateTableConstructor(params Type[] tableTypes)
        {
            var dm = new DynamicMethod("ConstructInstances", null, new[] { typeof(TDatabase) }, true);
            var il = dm.GetILGenerator();

            var setters = GetType().GetProperties()
                .Where(p => p.PropertyType.IsGenericType && tableTypes.Contains(p.PropertyType.GetGenericTypeDefinition()))
                .Select(p => Tuple.Create(
                        p.GetSetMethod(true),
                        p.PropertyType.GetConstructor(new[] { typeof(TDatabase), typeof(string) }),
                        p.Name,
                        p.DeclaringType
                 ));

            foreach (var setter in setters)
            {
                il.Emit(OpCodes.Ldarg_0);
                // [db]

                il.Emit(OpCodes.Ldstr, setter.Item3);
                // [db, likelyname]

                il.Emit(OpCodes.Newobj, setter.Item2);
                // [table]

                var table = il.DeclareLocal(setter.Item2.DeclaringType);
                il.Emit(OpCodes.Stloc, table);
                // []

                il.Emit(OpCodes.Ldarg_0);
                // [db]

                il.Emit(OpCodes.Castclass, setter.Item4);
                // [db cast to container]

                il.Emit(OpCodes.Ldloc, table);
                // [db cast to container, table]

                il.Emit(OpCodes.Callvirt, setter.Item1);
                // []
            }

            il.Emit(OpCodes.Ret);
            return (Action<TDatabase>)dm.CreateDelegate(typeof(Action<TDatabase>));
        }

        private static readonly ConcurrentDictionary<Type, string> tableNameMap = new ConcurrentDictionary<Type, string>();
        private string DetermineTableName<T>(string likelyTableName)
        {
            if (!tableNameMap.TryGetValue(typeof(T), out string name))
            {
                name = likelyTableName;
                if (!TableExists(name))
                {
                    name = "[" + typeof(T).Name + "]";
                }

                tableNameMap[typeof(T)] = name;
            }
            return name;
        }

        private bool TableExists(string name)
        {
            string schemaName = null;

            name = name.Replace("[", "");
            name = name.Replace("]", "");

            if (name.IndexOf('.') > 0)
            {
                var parts = name.Split('.');
                if (parts.Length == 2)
                {
                    schemaName = parts[0];
                    name = parts[1];
                }
            }

            var builder = new StringBuilder("select 1 from INFORMATION_SCHEMA.TABLES where ");
            if (!string.IsNullOrEmpty(schemaName)) builder.Append("TABLE_SCHEMA = @schemaName AND ");
            builder.Append("TABLE_NAME = @name");

            return _connection.Query(builder.ToString(), new { schemaName, name }, Transaction).Count() == 1;
        }

        /// <summary>
        /// Executes SQL against the current database.
        /// </summary>
        /// <param name="sql">The SQL to execute.</param>
        /// <param name="param">The parameters to use.</param>
        /// <returns>The number of rows affected.</returns>
        public int Execute(string sql, dynamic param = null) =>
            _connection.Execute(sql, param as object, Transaction, _commandTimeout);

        /// <summary>
        /// Queries the current database.
        /// </summary>
        /// <typeparam name="T">The type to return.</typeparam>
        /// <param name="sql">The SQL to execute.</param>
        /// <param name="param">The parameters to use.</param>
        /// <param name="buffered">Whether to buffer the results.</param>
        /// <returns>An enumerable of <typeparamref name="T"/> for the rows fetched.</returns>
        public IEnumerable<T> Query<T>(string sql, dynamic param = null, bool buffered = true) =>
            _connection.Query<T>(sql, param as object, Transaction, buffered, _commandTimeout);

        /// <summary>
        /// Queries the current database for a single record.
        /// </summary>
        /// <typeparam name="T">The type to return.</typeparam>
        /// <param name="sql">The SQL to execute.</param>
        /// <param name="param">The parameters to use.</param>
        /// <returns>An enumerable of <typeparamref name="T"/> for the rows fetched.</returns>
        public T QueryFirstOrDefault<T>(string sql, dynamic param = null) =>
            _connection.QueryFirstOrDefault<T>(sql, param as object, Transaction, _commandTimeout);

        /// <summary>
        /// Perform a multi-mapping query with 2 input types. 
        /// This returns a single type, combined from the raw types via <paramref name="map"/>.
        /// </summary>
        /// <typeparam name="TFirst">The first type in the recordset.</typeparam>
        /// <typeparam name="TSecond">The second type in the recordset.</typeparam>
        /// <typeparam name="TReturn">The combined type to return.</typeparam>
        /// <param name="sql">The SQL to execute for this query.</param>
        /// <param name="map">The function to map row types to the return type.</param>
        /// <param name="param">The parameters to use for this query.</param>
        /// <param name="transaction">The transaction to use for this query.</param>
        /// <param name="buffered">Whether to buffer the results in memory.</param>
        /// <param name="splitOn">The field we should split and read the second object from (default: "Id").</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout.</param>
        /// <returns>An enumerable of <typeparamref name="TReturn"/>.</returns>
        public IEnumerable<TReturn> Query<TFirst, TSecond, TReturn>(string sql, Func<TFirst, TSecond, TReturn> map, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null) =>
            _connection.Query(sql, map, param as object, transaction, buffered, splitOn, commandTimeout);

        /// <summary>
        /// Perform a multi-mapping query with 3 input types. 
        /// This returns a single type, combined from the raw types via <paramref name="map"/>.
        /// </summary>
        /// <typeparam name="TFirst">The first type in the recordset.</typeparam>
        /// <typeparam name="TSecond">The second type in the recordset.</typeparam>
        /// <typeparam name="TThird">The third type in the recordset.</typeparam>
        /// <typeparam name="TReturn">The combined type to return.</typeparam>
        /// <param name="sql">The SQL to execute for this query.</param>
        /// <param name="map">The function to map row types to the return type.</param>
        /// <param name="param">The parameters to use for this query.</param>
        /// <param name="transaction">The transaction to use for this query.</param>
        /// <param name="buffered">Whether to buffer the results in memory.</param>
        /// <param name="splitOn">The field we should split and read the second object from (default: "Id").</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout.</param>
        /// <returns>An enumerable of <typeparamref name="TReturn"/>.</returns>
        public IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TReturn>(string sql, Func<TFirst, TSecond, TThird, TReturn> map, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null) =>
            _connection.Query(sql, map, param as object, transaction, buffered, splitOn, commandTimeout);

        /// <summary>
        /// Perform a multi-mapping query with 4 input types. 
        /// This returns a single type, combined from the raw types via <paramref name="map"/>.
        /// </summary>
        /// <typeparam name="TFirst">The first type in the recordset.</typeparam>
        /// <typeparam name="TSecond">The second type in the recordset.</typeparam>
        /// <typeparam name="TThird">The third type in the recordset.</typeparam>
        /// <typeparam name="TFourth">The fourth type in the recordset.</typeparam>
        /// <typeparam name="TReturn">The combined type to return.</typeparam>
        /// <param name="sql">The SQL to execute for this query.</param>
        /// <param name="map">The function to map row types to the return type.</param>
        /// <param name="param">The parameters to use for this query.</param>
        /// <param name="transaction">The transaction to use for this query.</param>
        /// <param name="buffered">Whether to buffer the results in memory.</param>
        /// <param name="splitOn">The field we should split and read the second object from (default: "Id").</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout.</param>
        /// <returns>An enumerable of <typeparamref name="TReturn"/>.</returns>
        public IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TReturn>(string sql, Func<TFirst, TSecond, TThird, TFourth, TReturn> map, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null) =>
            _connection.Query(sql, map, param as object, transaction, buffered, splitOn, commandTimeout);

        /// <summary>
        /// Perform a multi-mapping query with 5 input types. 
        /// This returns a single type, combined from the raw types via <paramref name="map"/>.
        /// </summary>
        /// <typeparam name="TFirst">The first type in the recordset.</typeparam>
        /// <typeparam name="TSecond">The second type in the recordset.</typeparam>
        /// <typeparam name="TThird">The third type in the recordset.</typeparam>
        /// <typeparam name="TFourth">The fourth type in the recordset.</typeparam>
        /// <typeparam name="TFifth">The fifth type in the recordset.</typeparam>
        /// <typeparam name="TReturn">The combined type to return.</typeparam>
        /// <param name="sql">The SQL to execute for this query.</param>
        /// <param name="map">The function to map row types to the return type.</param>
        /// <param name="param">The parameters to use for this query.</param>
        /// <param name="transaction">The transaction to use for this query.</param>
        /// <param name="buffered">Whether to buffer the results in memory.</param>
        /// <param name="splitOn">The field we should split and read the second object from (default: "Id").</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout.</param>
        /// <returns>An enumerable of <typeparamref name="TReturn"/>.</returns>
        public IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TReturn>(string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TReturn> map, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null) =>
            _connection.Query(sql, map, param as object, transaction, buffered, splitOn, commandTimeout);

        /// <summary>
        /// Return a sequence of dynamic objects with properties matching the columns
        /// </summary>
        /// <param name="sql">The SQL to execute.</param>
        /// <param name="param">The parameters to use.</param>
        /// <param name="buffered">Whether the results should be buffered in memory.</param>
        /// <remarks>Note: each row can be accessed via "dynamic", or by casting to an IDictionary&lt;string,object&gt;</remarks>
        public IEnumerable<dynamic> Query(string sql, dynamic param = null, bool buffered = true) =>
            _connection.Query(sql, param as object, Transaction, buffered);

        /// <summary>
        /// Execute a command that returns multiple result sets, and access each in turn.
        /// </summary>
        /// <param name="sql">The SQL to execute for this query.</param>
        /// <param name="param">The parameters to use for this query.</param>
        /// <param name="transaction">The transaction to use for this query.</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout.</param>
        /// <param name="commandType">Is it a stored proc or a batch?</param>
        public SqlMapper.GridReader QueryMultiple(string sql, dynamic param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null) =>
            SqlMapper.QueryMultiple(_connection, sql, param, transaction, commandTimeout, commandType);

        /// <summary>
        /// Disposes the current database, rolling back current transactions.
        /// </summary>
        public virtual void Dispose()
        {
            var connection = _connection;
            if (connection.State != ConnectionState.Closed)
            {
                _connection = null;
                Transaction = null;
                connection?.Close();
            }
            GC.SuppressFinalize(this);
        }
    }
}