using System.Data;
using Microsoft.Data.SqlClient;

namespace ConsoleApp25
{
    class Program
    {
        static void Main(string[] args)
        {
            using var sqlConnection =
                new SqlConnection("Server=localhost;Initial Catalog=SqlGraph;Integrated Security=true;");
            sqlConnection.Open();
            var setup = @"DROP TABLE IF EXISTS Nodes;" +
                        "DROP TABLE IF EXISTS Edges;" +
                        "CREATE TABLE Nodes (Id INT PRIMARY KEY Identity(1,1), [Name] NVARCHAR(100)) AS Node;" +
                        "CREATE TABLE Edges AS Edge;";
            using (var command = new SqlCommand(setup, sqlConnection))
            {
                command.ExecuteNonQuery();
            }

            var nodes = new DataTable("Nodes");
            nodes.Columns.Add("Name", typeof(string));
            for (int i = 0; i < 100; i++)
            {
                nodes.Rows.Add($"Hello World {i}");
            }

            using (var sqlBulkCopy = new SqlBulkCopy(sqlConnection)
            {
                BatchSize = 5000,
                DestinationTableName = "Nodes",
                EnableStreaming = true
            })

            {
                sqlBulkCopy.ColumnMappings.Add("Name", "Name");
                sqlBulkCopy.WriteToServer(nodes);
            }

            // we need to obtain the real column names
            string fromId = null;
            string toId = null;
            using (var command =
                new SqlCommand("SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'Edges'",
                    sqlConnection))
            {
                using var output = command.ExecuteReader();
                while (output.Read())
                {
                    var columnName = output.GetString(0);
                    if (columnName.StartsWith("$from_id"))
                    {
                        fromId = columnName;
                    }
                    else if(columnName.StartsWith("$to_id"))
                    {
                        toId = columnName;
                    }
                }
            }

            var edges = new DataTable("Edges");
            edges.Columns.Add("From", typeof(string));
            edges.Columns.Add("To", typeof(string));
            using (var command = new SqlCommand("SELECT Id, $node_id AS NodeId FROM Nodes", sqlConnection))
            {
                string lastNodeId = null;
                using var output = command.ExecuteReader();
                while (output.Read())
                {
                    var nodeId = output.GetString("NodeId");
                    if (lastNodeId != null)
                    {
                        edges.Rows.Add(lastNodeId, nodeId);
                    }

                    lastNodeId = nodeId;
                }
            }


            using (var sqlBulkCopy = new SqlBulkCopy(sqlConnection)
            {
                BatchSize = 5000,
                DestinationTableName = "Edges",
                EnableStreaming = true
            })

            {
                // 'The given ColumnMapping does not match up with any column in the source or destination.'
                sqlBulkCopy.ColumnMappings.Add("From", "$from_id");  // fromId needs to be the hex $from_id_ABCDEF from the db not the $from_id pseudo-column names
                sqlBulkCopy.ColumnMappings.Add("To", "$to_id"); // toId needs to be the hex $to_id_ABCDEF from the db not the $to_id pseudo-column names
                //sqlBulkCopy.ColumnMappings.Add("From", fromId); <-- this works
                //sqlBulkCopy.ColumnMappings.Add("To", toId);
                sqlBulkCopy.WriteToServer(edges);
            }
            sqlConnection.Close();
        }
    }
}