using System;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Common;
using System.Data.Entity;
using System.Data.SqlClient;
using System.Text.RegularExpressions;

namespace ChangkeTec.Utils
{
    public class DbDescriptionUpdater<TContext>
   where TContext : System.Data.Entity.DbContext
    {
        public DbDescriptionUpdater(TContext context)
        {
            this.context = context;
        }

        Type contextType;
        TContext context;
        DbTransaction transaction;
        public void UpdateDatabaseDescriptions()
        {
            contextType = typeof(TContext);
            this.context = context;
            var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
            transaction = null;
            try
            {
                context.Database.Connection.Open();
                transaction = context.Database.Connection.BeginTransaction();
                foreach (var prop in props)
                {
                    if (!prop.PropertyType.InheritsOrImplements((typeof(DbSet<>)))) continue;
                    if(!prop.CanWrite)continue;
                    var tableType = prop.PropertyType.GetGenericArguments()[0];
                    SetTableDescriptions(tableType);
                }
                transaction.Commit();
            }
            catch
            {
                transaction?.Rollback();
                throw;
            }
            finally
            {
                if (context.Database.Connection.State == System.Data.ConnectionState.Open)
                    context.Database.Connection.Close();
            }
        }

        private void SetTableDescriptions(Type tableType)
        {
            string fullTableName = context.GetTableName(tableType);
            Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
            Match match = regex.Match(fullTableName);
            string tableName;
            if (match.Success)
                tableName = match.Groups["table"].Value;
            else
                tableName = fullTableName;

            var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
            if (tableAttrs.Length > 0)
                tableName = ((TableAttribute)tableAttrs[0]).Name;
            var table_attrs = tableType.GetCustomAttributes(typeof(DescriptionAttribute), false);
            if (table_attrs != null && table_attrs.Length > 0)
                SetTableDescription(tableName, ((DescriptionAttribute)table_attrs[0]).Description);
            foreach (var prop in tableType.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
            {
                if (prop.PropertyType.IsClass && prop.PropertyType != typeof(string))continue;
                var attrs = prop.GetCustomAttributes(typeof(NotMappedAttribute), false);
                if (attrs.Length > 0) continue;
                 attrs = prop.GetCustomAttributes(typeof(DescriptionAttribute), false);
                if (attrs != null && attrs.Length > 0)
                    SetColumnDescription(tableName, prop.Name, ((DescriptionAttribute)attrs[0]).Description);
            }
        }

        private void SetColumnDescription(string tableName, string columnName, string description)
        {

            string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
            var prevDesc = RunSqlScalar(strGetDesc);
            if (prevDesc == null)
            {
                RunSql(@"EXEC sp_addextendedproperty 
                @name = N'MS_Description', @value = @desc,
                @level0type = N'Schema', @level0name = 'dbo',
                @level1type = N'Table',  @level1name = @table,
                @level2type = N'Column', @level2name = @column;",
                                                       new SqlParameter("@table", tableName),
                                                       new SqlParameter("@column", columnName),
                                                       new SqlParameter("@desc", description));
            }
            else
            {
                RunSql(@"EXEC sp_updateextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table,
                    @level2type = N'Column', @level2name = @column;",
                                                       new SqlParameter("@table", tableName),
                                                       new SqlParameter("@column", columnName),
                                                       new SqlParameter("@desc", description));
            }
        }
        private void SetTableDescription(string tableName, string description)
        {

            string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "',null,null);";
            var prevDesc = RunSqlScalar(strGetDesc);
            if (prevDesc == null)
            {
                RunSql(@"EXEC sp_addextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table;",
                                                       new SqlParameter("@table", tableName),
                                                       new SqlParameter("@desc", description));
            }
            else
            {
                RunSql(@"EXEC sp_updateextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table;",
                                                       new SqlParameter("@table", tableName),
                                                       new SqlParameter("@desc", description));
            }
        }
        DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
        {
            var cmd = context.Database.Connection.CreateCommand();
            cmd.CommandText = cmdText;
            cmd.Transaction = transaction;
            foreach (var p in parameters)
                cmd.Parameters.Add(p);
            return cmd;
        }
        void RunSql(string cmdText, params SqlParameter[] parameters)
        {
            var cmd = CreateCommand(cmdText, parameters);
            cmd.ExecuteNonQuery();
        }
        object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
        {
            var cmd = CreateCommand(cmdText, parameters);
            return cmd.ExecuteScalar();
        }

    }
}