using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SQLite;
using System.Windows.Forms;
using System.Data;

namespace UI_study
{
    
    public class sqlHelper
    {
        /// <summary>
        /// 数据库连接定义
        /// </summary>

        public SQLiteConnection dbConnection;

        /// <summary>
        /// SQL命令定义
        /// </summary>
        private SQLiteCommand dbCommand;

        /// <summary>
        /// 数据读取定义
        /// </summary>
        private SQLiteDataReader dataReader;

        /// <summary>
        /// 数据库连接字符串定义
        /// </summary>
        private SQLiteConnectionStringBuilder dbConnectionstr;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="connectionString">连接SQLite库字符串</param>
        public sqlHelper(string connectionString)
        {
            try
            {
                dbConnection = new SQLiteConnection();

                dbConnectionstr = new SQLiteConnectionStringBuilder();
                dbConnectionstr.DataSource = connectionString;
                dbConnectionstr.Password = "admin";      //设置密码，SQLite ADO.NET实现了数据库密码保护
                dbConnection.ConnectionString = dbConnectionstr.ToString();
                dbConnection.Open();
            }
            catch (Exception e)
            {
                Log(e.ToString());
            }
        }

        /// <summary>
        /// 执行SQL命令
        /// </summary>
        /// <returns>The query.</returns>
        /// <param name="queryString">SQL命令字符串</param>
        public SQLiteDataReader ExecuteQuery(string queryString)
        {
            try
            {
                dbCommand = new SQLiteCommand(queryString, dbConnection);
                //dbCommand.CommandText = queryString;       //设置SQL语句
                dataReader = dbCommand.ExecuteReader();
            }
            catch (Exception e)
            {
                Log(e.Message);
            }

            return dataReader;
        }

        /// <summary>
        /// 关闭数据库连接
        /// </summary>
        public void CloseConnection()
        {
            //销毁Command
            if (dbCommand != null)
            {
                dbCommand.Cancel();
            }
            dbCommand = null;
            //销毁Reader
            if (dataReader != null)
            {
                dataReader.Close();
            }
            dataReader = null;
            //销毁Connection
            if (dbConnection != null)
            {
                dbConnection.Close();
            }
            dbConnection = null;

        }

        /// <summary>
        /// 读取整张数据表
        /// </summary>
        /// <returns>The full table.</returns>
        /// <param name="tableName">数据表名称</param>
        public SQLiteDataReader ReadFullTable(string tableName)
        {
            string queryString = "SELECT * FROM " + tableName;  //获取所有可用的字段
            return ExecuteQuery(queryString);
        }

        /// <summary>
        /// 向指定数据表中插入数据
        /// </summary>
        /// <returns>The values.</returns>
        /// <param name="tableName">数据表名称</param>
        /// <param name="values">插入的数值</param>
        public SQLiteDataReader InsertValues(string tableName, string[] values)
        {
            //获取数据表中字段数目
            //int fieldCount = ReadFullTable(tableName).FieldCount;
            //当插入的数据长度不等于字段数目时引发异常
            //if (values.Length != fieldCount)
            //{
            //    throw new SQLiteException("values.Length!=fieldCount");
            //}
            string queryString = "INSERT INTO " + tableName + " VALUES (" + "'" + values[0] + "'";
            for (int i = 1; i < values.Length; i++)
            {
                queryString += ", " + "'" + values[i] + "'";
            }
            queryString += " )";
            return ExecuteQuery(queryString);
        }

        /// <summary>
        /// 更新指定数据表内的数据
        /// </summary>
        /// <returns>The values.</returns>
        /// <param name="tableName">数据表名称</param>
        /// <param name="colNames">字段名</param>
        /// <param name="colValues">字段名对应的数据</param>
        /// <param name="key">关键字</param>
        /// <param name="value">关键字对应的值</param>
        /// <param name="operation">运算符：=,<,>,...，默认“=”</param>
        public SQLiteDataReader UpdateValues(string tableName, string[] colNames, string[] colValues, string key, string value, string operation)
        {
            // operation="=";  //默认
            //当字段名称和字段数值不对应时引发异常
            if (colNames.Length != colValues.Length)
            {
                throw new SQLiteException("colNames.Length!=colValues.Length");
            }
            string queryString = "UPDATE " + tableName + " SET " + colNames[0] + "=" + "'" + colValues[0] + "'";

            for (int i = 1; i < colValues.Length; i++)
            {
                queryString += ", " + colNames[i] + "=" + "'" + colValues[i] + "'";
            }
            queryString += " WHERE " + key + operation + "'" + value + "'";

            return ExecuteQuery(queryString);
        }
        /// <summary>
        /// 更新指定数据表内的数据
        /// </summary>
        /// <returns>The values.</returns>
        /// <param name="tableName">数据表名称</param>
        /// <param name="colNames">字段名</param>
        /// <param name="colValues">字段名对应的数据</param>
        /// <param name="key">关键字</param>
        /// <param name="value">关键字对应的值</param>
        /// <param name="operation">运算符：=,<,>,...，默认“=”</param>
        public SQLiteDataReader UpdateValues(string tableName, string[] colNames, string[] colValues, string key1, string value1, string operation, string key2, string value2)
        {
            // operation="=";  //默认
            //当字段名称和字段数值不对应时引发异常
            if (colNames.Length != colValues.Length)
            {
                throw new SQLiteException("colNames.Length!=colValues.Length");
            }
            string queryString = "UPDATE " + tableName + " SET " + colNames[0] + "=" + "'" + colValues[0] + "'";

            for (int i = 1; i < colValues.Length; i++)
            {
                queryString += ", " + colNames[i] + "=" + "'" + colValues[i] + "'";
            }
            //表中已经设置成int类型的不需要再次添加‘单引号’，而字符串类型的数据需要进行添加‘单引号’
            queryString += " WHERE " + key1 + operation + "'" + value1 + "'" + "OR " + key2 + operation + "'" + value2 + "'";

            return ExecuteQuery(queryString);
        }


        /// <summary>
        /// 删除指定数据表内的数据
        /// </summary>
        /// <returns>The values.</returns>
        /// <param name="tableName">数据表名称</param>
        /// <param name="colNames">字段名</param>
        /// <param name="colValues">字段名对应的数据</param>
        public SQLiteDataReader DeleteValuesOR(string tableName, string[] colNames, string[] colValues, string[] operations)
        {
            //当字段名称和字段数值不对应时引发异常
            if (colNames.Length != colValues.Length || operations.Length != colNames.Length || operations.Length != colValues.Length)
            {
                throw new SQLiteException("colNames.Length!=colValues.Length || operations.Length!=colNames.Length || operations.Length!=colValues.Length");
            }

            string queryString = "DELETE FROM " + tableName + " WHERE " + colNames[0] + operations[0] + "'" + colValues[0] + "'";
            for (int i = 1; i < colValues.Length; i++)
            {
                queryString += "OR " + colNames[i] + operations[0] + "'" + colValues[i] + "'";
            }
            return ExecuteQuery(queryString);
        }

        /// <summary>
        /// 删除指定数据表内的数据
        /// </summary>
        /// <returns>The values.</returns>
        /// <param name="tableName">数据表名称</param>
        /// <param name="colNames">字段名</param>
        /// <param name="colValues">字段名对应的数据</param>
        public SQLiteDataReader DeleteValuesAND(string tableName, string[] colNames, string[] colValues, string[] operations)
        {
            //当字段名称和字段数值不对应时引发异常
            if (colNames.Length != colValues.Length || operations.Length != colNames.Length || operations.Length != colValues.Length)
            {
                throw new SQLiteException("colNames.Length!=colValues.Length || operations.Length!=colNames.Length || operations.Length!=colValues.Length");
            }

            string queryString = "DELETE FROM " + tableName + " WHERE " + colNames[0] + operations[0] + "'" + colValues[0] + "'";

            for (int i = 1; i < colValues.Length; i++)
            {
                queryString += " AND " + colNames[i] + operations[i] + "'" + colValues[i] + "'";
            }
            return ExecuteQuery(queryString);
        }


        /// <summary>
        /// 创建数据表
        /// </summary> +
        /// <returns>The table.</returns>
        /// <param name="tableName">数据表名</param>
        /// <param name="colNames">字段名</param>
        /// <param name="colTypes">字段名类型</param>
        public SQLiteDataReader CreateTable(string tableName, string[] colNames, string[] colTypes)
        {
            string queryString = "CREATE TABLE IF NOT EXISTS " + tableName + "( " + colNames[0] + " " + colTypes[0];
            for (int i = 1; i < colNames.Length; i++)
            {
                queryString += ", " + colNames[i] + " " + colTypes[i];
            }
            queryString += "  ) ";
            return ExecuteQuery(queryString);
        }

        /// <summary>
        /// Reads the table.
        /// </summary>
        /// <returns>The table.</returns>
        /// <param name="tableName">Table name.</param>
        /// <param name="items">Items.</param>
        /// <param name="colNames">Col names.</param>
        /// <param name="operations">Operations.</param>
        /// <param name="colValues">Col values.</param>
        public SQLiteDataReader ReadTable(string tableName, string[] items, string[] colNames, string[] operations, string[] colValues)
        {
            string queryString = "SELECT " + items[0];
            for (int i = 1; i < items.Length; i++)
            {
                queryString += ", " + items[i];
            }
            queryString += " FROM " + tableName + " WHERE " + colNames[0] + " " + operations[0] + " " + colValues[0];
            for (int i = 0; i < colNames.Length; i++)
            {
                queryString += " AND " + colNames[i] + " " + operations[i] + " " + colValues[0] + " ";
            }
            return ExecuteQuery(queryString);
        }

        /// <summary>
        /// 本类log
        /// </summary>
        /// <param name="s"></param>
        static void Log(string s)
        {
            Console.WriteLine("class SqLiteHelper:::" + s);
        }


    }
}