using System;
using System.Collections.Generic;
using Microsoft.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Transactions;

namespace bnhtrade.Core.Data.Database.Stock
{
    public class JournalCrud : Connection
    {
        // only to be assessable via code, use stock relocate to move stock bewtween status'
        public int StockJournalInsert(int journalTypeId, int stockId, List<(int statusId, int quantity)> journalPosts,
            DateTime entryDate, bool isNewStock = false)
        {
            /* 
             * TODO: currently the consistancy check checks the journal after the  entry has been inserted to the db, if the check fails
             * the transaction scope is disposed, and the ne journal entries roll back. However, if this is done within a higher 
             * level transaction scope, this nested dispose() also rolls back the all transacopes scopes it is a child of.
             * 
             * Therefore, a consistancy check needs to be simulated in code to negate the need to rollback/dispose of a db transaction.
             * This would also have some slight performance benefits.
             * 
             * Once you've done this, fix the SkuTransactionReconcile class: Currently it's transactionscope only covers updates.
             * Need to set the scope to cover the intial table read (to lock the records). The issue above restricts this.
            */


            // balance and status IsCredit checks made by post insert function

            // create the journal entry
            int stockJournalId;
            using (TransactionScope scope = new TransactionScope())
            using (SqlConnection conn = new SqlConnection(SqlConnectionString))
            {
                conn.Open();

                //consitancy check is required?
                bool consistencyRequired = true;
                // get date of most recent debit for status' that I will be crediting
                if (isNewStock == false)
                {
                    // build sql string
                    string stringSql = @"
                        SELECT 
                            tblStockJournal.EntryDate
                        FROM 
                            tblStockJournal 
                            INNER JOIN tblStockJournalPost 
                            ON tblStockJournal.StockJournalID = tblStockJournalPost.StockJournalID
                        WHERE 
                            tblStockJournal.StockID=@stockId 
                            AND EntryDate>=@entryDate
                            AND tblStockJournalPost.Quantity>0 
                            AND (";

                    bool firstDone = false;
                    foreach (var item in journalPosts)
                    {
                        if (item.quantity < 0)
                        {
                            if (firstDone)
                            {
                                stringSql = stringSql + " OR ";
                            }
                            stringSql = stringSql + "tblStockJournalPost.StockStatusID=" + item.statusId;
                            firstDone = true;
                        }
                    }
                    stringSql = stringSql + ");";

                    using (SqlCommand cmd = new SqlCommand(stringSql, conn))
                    {
                        cmd.Parameters.AddWithValue("@stockId", stockId);
                        cmd.Parameters.AddWithValue("@entryDate", entryDate.ToUniversalTime());

                        using (var reader = cmd.ExecuteReader())
                        {
                            if (reader.HasRows)
                            {
                                consistencyRequired = true;
                            }
                            else
                            {
                                consistencyRequired = false;
                            }
                        }
                    }
                }

                // create journal entry
                using (SqlCommand cmd = new SqlCommand(@"
                        INSERT INTO tblStockJournal ( EntryDate, StockJournalTypeID, StockID, IsLocked ) 
                        OUTPUT INSERTED.StockJournalID 
                        VALUES ( @EntryDate, @journalTypeId, @stockID, @isLocked );
                        ", conn))
                {
                    // add parameters
                    cmd.Parameters.AddWithValue("@stockID", stockId);
                    cmd.Parameters.AddWithValue("@journalTypeId", journalTypeId);
                    cmd.Parameters.AddWithValue("@EntryDate", entryDate.ToUniversalTime());
                    cmd.Parameters.AddWithValue("@isLocked", isNewStock);

                    //execute
                    stockJournalId = (int)cmd.ExecuteScalar();
                }

                // insert journal posts into database
                StockJournalPostInsert(conn, stockId, stockJournalId, journalPosts, isNewStock);

                // consistency check
                bool consistencyResult = true;
                if (consistencyRequired)
                {
                    consistencyResult = false;
                    // build list of effected status'
                    var statusIdEffected = new List<int>();
                    foreach (var item in journalPosts)
                    {
                        if (item.quantity < 0)
                        {
                            statusIdEffected.Add(item.statusId);
                        }
                    }
                    // run check
                    consistencyResult = StockJournalConsistencyCheck(stockId, statusIdEffected);
                }

                if (consistencyResult)
                {
                    // commit
                    scope.Complete();
                    return stockJournalId;
                }
                else
                {
                    throw new Exception("Unable to insert stock journal entry, consistancy check failed.");
                }
            }
        }

        public void StockJournalDelete(int stockJournalId)
        {
            using (TransactionScope scope = new TransactionScope())
            using (SqlConnection conn = new SqlConnection(SqlConnectionString))
            {
                conn.Open();

                // get date for journal entry
                DateTime entryDate;
                int stockId;
                using (SqlCommand cmd = new SqlCommand(@"
                        SELECT tblStockJournal.EntryDate, StockID
                        FROM tblStockJournal
                        WHERE (((tblStockJournal.StockJournalID)=@stockJournalId));
                        ", conn))
                {
                    // add parameters
                    cmd.Parameters.AddWithValue("@stockJournalId", stockJournalId);

                    using (var reader = cmd.ExecuteReader())
                    {
                        if (reader.Read())
                        {
                            entryDate = DateTime.SpecifyKind(reader.GetDateTime(0), DateTimeKind.Utc);
                            stockId = reader.GetInt32(1);
                        }
                        else
                        {
                            throw new Exception("StockJournalID=" + stockJournalId + " does not exist!");
                        }
                    }

                }

                // is consistancy check required
                bool consistancyCheck;
                // build list of debits that are to be deleted
                var debitList = new List<int>();
                using (SqlCommand cmd = new SqlCommand(@"
                        SELECT tblStockJournalPost.StockStatusID
                        FROM tblStockJournalPost
                        WHERE (((tblStockJournalPost.StockJournalID)=@stockJournalId) AND ((tblStockJournalPost.Quantity)>0));
                        ", conn))
                {
                    // add parameters
                    cmd.Parameters.AddWithValue("@stockJournalId", stockJournalId);

                    using (var reader = cmd.ExecuteReader())
                    {
                        if (reader.HasRows)
                        {
                            while (reader.Read())
                            {
                                debitList.Add(reader.GetInt32(0));
                            }
                        }
                        else
                        {
                            throw new Exception("StockJournalID=" + stockJournalId + " has no debits with quantity greater than zero!");
                        }
                    }
                }

                // check no credits for stockId & debit combination have been made since delete entry
                string stringSql = @"
                        SELECT 
                            tblStockJournal.EntryDate
                        FROM 
                            tblStockJournal 
                            INNER JOIN tblStockJournalPost 
                            ON tblStockJournal.StockJournalID = tblStockJournalPost.StockJournalID
                        WHERE 
                            tblStockJournal.StockID=@stockId 
                            AND tblStockJournalPost.Quantity<0 
                            AND EntryDate>=@entryDate 
                            AND (";

                bool firstDone = false;
                foreach (var item in debitList)
                {
                    if (firstDone)
                    {
                        stringSql = stringSql + " OR ";
                    }
                    stringSql = stringSql + "tblStockJournalPost.StockStatusID=" + item;
                    firstDone = true;
                }
                stringSql = stringSql + ");";

                using (SqlCommand cmd = new SqlCommand(stringSql, conn))
                {
                    cmd.Parameters.AddWithValue("@stockId", stockId);
                    cmd.Parameters.AddWithValue("@entryDate", entryDate.ToUniversalTime());

                    using (var reader = cmd.ExecuteReader())
                    {
                        if (reader.HasRows)
                        {
                            consistancyCheck = true;
                        }
                        else
                        {
                            consistancyCheck = false;
                        }
                    }
                }

                // delete the posts
                StockJournalPostDelete(conn, stockJournalId);

                // delete journal entry
                using (SqlCommand cmd = new SqlCommand(@"
                        DELETE FROM tblStockJournal
                        WHERE StockJournalID=@stockJournalId;
                        ", conn))
                {
                    // add parameters
                    cmd.Parameters.AddWithValue("@stockJournalId", stockJournalId);

                    int count = cmd.ExecuteNonQuery();

                    if (count != 1)
                    {
                        throw new Exception("Failed to delete stock journal header.");
                    }
                }

                // consistanct check
                bool consistencyResult = true;
                if (consistancyCheck)
                {
                    // run check
                    consistencyResult = StockJournalConsistencyCheck(stockId, debitList);
                }

                if (consistencyResult)
                {
                    // commit
                    scope.Complete();
                }
                else
                {
                    throw new Exception("Unable to delete stock journal entry, consistancy check failed.");
                }
            }
        }

        private void StockJournalPostInsert(SqlConnection conn, int stockId, int stockJournalId,
            List<(int statusId, int quantity)> journalPosts, bool isNewStock = false)
        {
            //checks
            if (journalPosts.Count > 2)
            {
                // I have purposely made the code to accept split transaction incase of future requirements, however, db design is simpler this way.
                throw new Exception("Stock journal does not currently support split transactions (greater than two posts)." + journalPosts.Count + " number posts attempted.");
            }
            else if (journalPosts.Count < 2)
            {
                // list not long enough
                throw new Exception("Stock journal entry requires minium of two posts, entry of " + journalPosts.Count + " number posts attempted.");
            }

            if (journalPosts.Sum(item => item.quantity) != 0)
            {
                // credits and debits do not match
                throw new Exception("Sum of credits and debits do not resolve to zero.");
            }

            // group credits and debits by status
            var dicStatusQty = new Dictionary<int, int>();
            foreach (var post in journalPosts)
            {
                if (dicStatusQty.ContainsKey(post.statusId) == false)
                {
                    dicStatusQty.Add(post.statusId, post.quantity);
                }
                else
                {
                    dicStatusQty[post.statusId] = dicStatusQty[post.statusId] + post.quantity;
                }
            }

            // get isCreditOnly for each status
            var dicStatusIsCreditOnly = new Dictionary<int, bool>();
            foreach (var item in dicStatusQty)
            {
                using (SqlCommand cmd = new SqlCommand(@"
                        SELECT IsCreditOnly FROM tblStockStatus WHERE StockStatusID=@statusId;
                    ", conn))
                {
                    cmd.Parameters.AddWithValue("@statusId", item.Key);

                    dicStatusIsCreditOnly.Add(item.Key, (bool)cmd.ExecuteScalar());
                }
            }

            // check there is only one IsCreditOnly in list and it is allowed in this instance
            int isCreditOnlyCount = 0;
            foreach (var item in dicStatusIsCreditOnly)
            {
                if (item.Value)
                {
                    isCreditOnlyCount = isCreditOnlyCount + 1;
                }
            }
            if (isNewStock == false && isCreditOnlyCount > 0)
            {
                throw new Exception("Attempted credit or debit to 'Is Credit Only' status not allowed, in this instance.");
            }
            if (isNewStock == true && isCreditOnlyCount != 1)
            {
                throw new Exception("StockID=" + stockId + ", each stock line must have only have one IsCreditOnly=True status assigned to it.");
            }

            // ensure debit (or zero credit) isn't made to credit only status
            // need to do this check via original post list (i.e. journalPosts)
            foreach (var post in journalPosts)
            {
                // debit check
                if (post.quantity >= 0)
                {
                    if (dicStatusIsCreditOnly[post.statusId] == true)
                    {
                        throw new Exception("Cannot make debit, or zero quantity credit, to credit only status. StatusID=" + post.statusId);
                    }
                }
            }

            // balance check for any credits (that are not isCreditOnly=true)
            foreach (var item in dicStatusQty)
            {
                if (item.Value < 0 && dicStatusIsCreditOnly[item.Key] == false)
                {
                    int quantity = new Data.Database.Stock.ReadStatusBalance().ByStockId(stockId, item.Key);

                    if (quantity + item.Value < 0)
                    {
                        throw new Exception("Credit status balance check failed. Available balance " + quantity + ", attempted credit " + item.Value * -1 + ".");
                    }
                }
            }

            // get this far...
            // insert journal posts into database
            foreach (var post in journalPosts)
            {
                using (SqlCommand cmd = new SqlCommand(@"
                        INSERT INTO tblStockJournalPost ( StockJournalID, StockStatusID, Quantity ) 
                        VALUES ( @StockJournalId, @stockStatudId, @quantity );
                        ", conn))
                {
                    cmd.Parameters.AddWithValue("@StockJournalId", stockJournalId);
                    cmd.Parameters.AddWithValue("@stockStatudId", post.statusId);
                    cmd.Parameters.AddWithValue("@quantity", post.quantity);

                    // execute
                    cmd.ExecuteNonQuery();
                }
            }
        }

        private void StockJournalPostDelete(SqlConnection conn, int stockJournalId)
        {
            using (SqlCommand cmd = new SqlCommand(@"
                    DELETE FROM tblStockJournalPost 
                    WHERE StockJournalID=@stockJournalId
                    ", conn))
            {
                cmd.Parameters.AddWithValue("@StockJournalId", stockJournalId);

                // execute
                cmd.ExecuteNonQuery();

                // the calling method must compete any transaction-scope on the connection
            }
        }

        // can be used before commiting an sql insert, update or delete to the stock journal to ensure a status does not fall below 0 
        // (unless the status is enabled to do so)
        // set empty list or statusIdEffected to null to check entier stock entries for consistency
        public bool StockJournalConsistencyCheck(int stockId, List<int> statusIdEffected = null)
        {
            if (statusIdEffected == null)
            {
                statusIdEffected = new List<int>();
            }


            using (SqlConnection conn = new SqlConnection(SqlConnectionString))
            {
                conn.Open();

                // if no list supplied, build list of all used status' for stockId
                if (statusIdEffected.Count == 0)
                {
                    using (SqlCommand cmd = new SqlCommand(@"
                        SELECT 
                            tblStockJournalPost.StockStatusID
                        FROM 
                            tblStockJournal 
                            INNER JOIN tblStockJournalPost 
                            ON tblStockJournal.StockJournalID = tblStockJournalPost.StockJournalID
                        WHERE 
                            tblStockJournal.StockID=@stockId
                        GROUP BY 
                            tblStockJournalPost.StockStatusID;
                        ", conn))
                    {
                        cmd.Parameters.AddWithValue("@stockId", stockId);

                        using (var reader = cmd.ExecuteReader())
                        {
                            if (reader.HasRows)
                            {
                                while (reader.Read())
                                {
                                    statusIdEffected.Add(reader.GetInt32(0));
                                }
                            }
                            else
                            {
                                throw new Exception("No stock journal entries exist for StockID=" + stockId);
                            }
                        }
                    }
                }

                // build the sql string to build creditCreate bool
                var dicStatusCreditOnly = new Dictionary<int, bool>();
                string sqlString = @"
                        SELECT 
                            tblStockStatus.StockStatusID, tblStockStatus.IsCreditOnly
                        FROM 
                            tblStockStatus ";

                for (var i = 0; i < statusIdEffected.Count; i++)
                {
                    if (i == 0)
                    {
                        sqlString = sqlString + " WHERE tblStockStatus.StockStatusID=" + statusIdEffected[i];
                    }
                    else
                    {
                        sqlString = sqlString + " OR tblStockStatus.StockStatusID=" + statusIdEffected[i];
                    }

                    //if (i == (statusIdEffected.Count - 1))
                    //{
                    //    sqlString = sqlString + ";";
                    //}
                }
                sqlString = sqlString + " GROUP BY tblStockStatus.StockStatusID, tblStockStatus.IsCreditOnly;";

                // run query & build dictionaries
                using (SqlCommand cmd = new SqlCommand(sqlString, conn))
                {
                    cmd.Parameters.AddWithValue("@stockId", stockId);

                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        if (reader.Read())
                        {
                            dicStatusCreditOnly.Add(reader.GetInt32(0), reader.GetBoolean(1));

                            while (reader.Read())
                            {
                                dicStatusCreditOnly.Add(reader.GetInt32(0), reader.GetBoolean(1));
                            }
                        }
                        else
                        {
                            throw new Exception("Error, no journal entries found for StockID=" + stockId);
                        }
                    }
                }

                // check integrity of supplied statusIds
                foreach (int statusId in statusIdEffected)
                {
                    if (!dicStatusCreditOnly.ContainsKey(statusId))
                    {
                        throw new Exception("Supplied StatusId (" + statusId + ") doesn't exist for StockId=" + stockId);
                    }
                }

                // loop through each statudId and check integrity, if createdEnabled=false
                foreach (int statudId in statusIdEffected)
                {
                    if (dicStatusCreditOnly[statudId] == false)
                    {
                        using (SqlCommand cmd = new SqlCommand(@"
                                SELECT 
                                    tblStockJournal.EntryDate, tblStockJournalPost.Quantity
                                FROM 
                                    tblStockJournal 
                                    INNER JOIN tblStockJournalPost 
                                    ON tblStockJournal.StockJournalID = tblStockJournalPost.StockJournalID
                                WHERE 
                                    tblStockJournal.StockID=@stockId 
                                    AND tblStockJournalPost.StockStatusID=@statudId 
                                ORDER BY 
                                    tblStockJournal.EntryDate;
                                ", conn))
                        {
                            cmd.Parameters.AddWithValue("@stockId", stockId);
                            cmd.Parameters.AddWithValue("@statudId", statudId);

                            using (SqlDataReader reader = cmd.ExecuteReader())
                            {
                                // read first line into variables
                                reader.Read();
                                int quantity = reader.GetInt32(1);
                                DateTime entryDate = DateTime.SpecifyKind(reader.GetDateTime(0), DateTimeKind.Utc);

                                while (true)
                                {
                                    // compare to next values
                                    if (reader.Read())
                                    {
                                        DateTime nextEntryDate = DateTime.SpecifyKind(reader.GetDateTime(0), DateTimeKind.Utc);
                                        // don't check quantites for transactions on same date
                                        if (entryDate == nextEntryDate)
                                        {
                                            entryDate = nextEntryDate;
                                            quantity = quantity + reader.GetInt32(1);
                                        }
                                        // check if dates are different
                                        else
                                        {
                                            if (quantity < 0)
                                            {
                                                return false;
                                            }
                                            else
                                            {
                                                entryDate = nextEntryDate;
                                                quantity = quantity + reader.GetInt32(1);
                                            }
                                        }
                                    }
                                    // end if no records, check quantity
                                    else
                                    {
                                        if (quantity < 0)
                                        {
                                            return false;
                                        }
                                        break;
                                    }
                                }
                            }
                        }
                    }
                }
            }
            // get this far, all good
            return true;
        }
    }
}