using System;
using System.Collections.Generic;
using System.Linq;
using Schaad.Accounting.Datasets;
using Schaad.Accounting.Datasets.Reports;
using Schaad.Accounting.Interfaces;
using Schaad.Accounting.Models;
using Schaad.Finance.Api.Datasets;

namespace Schaad.Accounting.Services
{
    public class ViewService : IViewService
    {
        private readonly IAccountRepository accountRepository;
        private readonly IBankTransactionRepository bankTransactionRepository;
        private readonly IBookingRuleRepository bookingRuleRepository;
        private readonly ISubclassRepository subclassRepository;
        private readonly ITransactionRepository transactionRepository;
        private readonly IFxConverter fxConverter;

        public ViewService(
            IAccountRepository accountRepository,
            IBankTransactionRepository bankTransactionRepository,
            ITransactionRepository transactionRepository,
            ISubclassRepository subclassRepository,
            IBookingRuleRepository bookingRuleRepository,
            IFxConverter fxConverter)
        {
            this.accountRepository = accountRepository;
            this.bankTransactionRepository = bankTransactionRepository;
            this.transactionRepository = transactionRepository;
            this.subclassRepository = subclassRepository;
            this.bookingRuleRepository = bookingRuleRepository;
            this.fxConverter = fxConverter;
        }

        /// <summary>
        /// Load accounts
        /// </summary>
        public AccountDataset GetAccountView(string id)
        {
            var accounts = GetAccountViewList();
            return accounts.Single(t => t.Id == id);
        }

        /// <summary>
        /// Load accounts and calculates their balances
        /// </summary>
        public List<AccountDataset> GetAccountViewList()
        {
            var accounts = accountRepository.GetAccountList();
            var transactionList = GetTransactionViewList();
            var subClassNameByNumber = subclassRepository.GetSubClassList().ToDictionary(s => s.Number, s => s.Name);

            // Group transactions by account so per-account balance is O(k) instead of O(M).
            var creditsByAccount = transactionList.GroupBy(t => t.TargetAccountId).ToDictionary(g => g.Key, g => g.ToList());
            var debitsByAccount = transactionList.GroupBy(t => t.OriginAccountId).ToDictionary(g => g.Key, g => g.ToList());

            var accountList = accounts.Select(a =>
                {
                    var balance = ComputeBalance(a, creditsByAccount, debitsByAccount);
                    return new AccountDataset(
                        account: a,
                        balance: balance,
                        balanceCHF: fxConverter.ConvertToChf(balance, a.Currency),
                        startBalanceCHF: fxConverter.ConvertToChf(a.StartBalance, a.Currency),
                        className: subclassRepository.GetClass(a.Class),
                        subClassName: subClassNameByNumber[a.SubClass]);
                })
                .ToList();

            return accountList.OrderBy(a => a.Number).ToList();
        }

        private static decimal ComputeBalance(
            Account account,
            Dictionary<string, List<TransactionDataset>> creditsByAccount,
            Dictionary<string, List<TransactionDataset>> debitsByAccount)
        {
            var balance = account.StartBalance;
            if (creditsByAccount.TryGetValue(account.Id, out var credits))
            {
                balance += credits.Sum(t => t.GetValue(account.IsFxAccount));
            }
            if (debitsByAccount.TryGetValue(account.Id, out var debits))
            {
                balance -= debits.Sum(t => t.GetValue(account.IsFxAccount));
            }
            return balance;
        }

        public BalanceDataset GetBalanceView()
        {
            var accountList = GetAccountViewList();
            var balanceView = new BalanceDataset(
                    activaAccountList: accountList.Where(m => m.Class == ClassIds.Activa).ToList(),
                    passivaAccountList: accountList.Where(m => m.Class == ClassIds.Passiva).ToList(),
                    totalActivaCHF: Math.Abs(accountList.Where(m => m.Class == ClassIds.Activa).Sum(m => m.BalanceCHF)),
                    totalPassivaCHF: Math.Abs(accountList.Where(m => m.Class == ClassIds.Passiva).Sum(m => m.BalanceCHF))
                );

            return balanceView;
        }

        public BalanceSheetDataset GetBalanceSheetView(int year)
        {
            var accountList = GetAccountViewList();

            var profit = Math.Abs(accountList.Where(m => m.Class == ClassIds.Income).Sum(m => m.BalanceCHF));
            profit += Math.Abs(accountList.Where(m => m.Class == ClassIds.Activa).Sum(m => fxConverter.ConvertToChf(m.StartBalance, m.Currency)));
            var loss = Math.Abs(accountList.Where(m => m.Class == ClassIds.Expenses).Sum(m => m.BalanceCHF));

            var balanceView = new BalanceSheetDataset(
                    activaAccountList: accountList.Where(m => m.Class == ClassIds.Activa).ToList(),
                    incomeAccountList: accountList.Where(m => m.Class == ClassIds.Income).ToList(),
                    expensesAccountList: accountList.Where(m => m.Class == ClassIds.Expenses).ToList(),
                    profitCHF: profit,
                    lossCHF: loss,
                    year: year
                );

            return balanceView;
        }

        /// <summary>
        /// Get transaction list with the origin and target account for each transaction
        /// </summary>
        public List<TransactionDataset> GetTransactionViewList()
        {
            var accountsById = accountRepository.GetAccountList().ToDictionary(a => a.Id);
            var transactionList = transactionRepository.GetTransactionList();

            return transactionList.Select(t =>
                    new TransactionDataset(
                        t,
                        accountsById[t.OriginAccountId],
                        accountsById[t.TargetAccountId]))
                .ToList();
        }

        /// <summary>
        /// Get transaction list with the origin and target account for each transaction
        /// </summary>
        public List<TransactionDataset> GetTransactionViewList(string accountId)
        {
            var accountsById = accountRepository.GetAccountList().ToDictionary(a => a.Id);
            var transactionList = transactionRepository.GetTransactionList()
                .Where(t => t.OriginAccountId == accountId || t.TargetAccountId == accountId);

            return transactionList.Select(t =>
                    new TransactionDataset(
                        WithDisplaySign(t),
                        accountsById[t.OriginAccountId],
                        accountsById[t.TargetAccountId]))
                .ToList();

            Transaction WithDisplaySign(Transaction t)
            {
                var originAccount = accountsById[t.OriginAccountId];
                if (originAccount.Class == ClassIds.Activa && accountId == t.OriginAccountId)
                {
                    var copy = new Transaction();
                    t.Copy(copy);
                    copy.Value *= -1;
                    return copy;
                }
                return t;
            }
        }

        /// <summary>
        /// Get booking rules with their account
        /// </summary>
        public List<BookingRuleDataset> GetBookingRuleViewList()
        {
            var accountsById = accountRepository.GetAccountList().ToDictionary(a => a.Id);
            var bookingRules = bookingRuleRepository.GetBookingRuleList();

            return bookingRules.Select(t =>
                    new BookingRuleDataset(t, accountsById[t.AccountId].Name))
                .ToList();
        }

        /// <summary>
        /// Load open bank transactions
        /// </summary>
        public List<BankTransaction> GetOpenBankTransactionList()
        {
            var transactions = transactionRepository
                .GetTransactionList()
                .Where(t => string.IsNullOrEmpty(t.BankTransactionId) == false)
                .Select(t => t.BankTransactionId);

            var bankTransactions = bankTransactionRepository
                .GetBankTransactionList()
                .Where(b => b.Ignore == false && transactions.Contains(b.Id) == false)
                .ToList();

            return bankTransactions;
        }

        public List<Transaction> MatchOpenBankTransactions()
        {
            var newTransactionList = new List<Transaction>();
            var transactions = transactionRepository.GetTransactionList();
            var accounts = accountRepository.GetAccountList();
            var bookingRules = bookingRuleRepository.GetBookingRuleList();
            var bankTransactions = GetOpenBankTransactionList().OrderBy(t => t.ValueDate);
            foreach (var bankTransaction in bankTransactions)
            {
                var trx = new Transaction(bankTransaction, accounts);
                MatchBankTransactionByBookingRule(bankTransaction.Text, trx, bookingRules);
                MatchBankTransactionBySameAccountsLastMonth(bankTransaction, trx, transactions);
                MatchBankTransactionBySameValueLastMonth(bankTransaction, trx, transactions);
                newTransactionList.Add(trx);
            }
            return newTransactionList;
        }

        public List<Transaction> MatchCreditCardTransactions(string bankTransactionId, IReadOnlyList<CreditCardTransaction> creditCardTransactions)
        {
            var accounts = accountRepository.GetAccountList();
            var bankTrx = bankTransactionRepository.GetBankTransaction(bankTransactionId);
            var bookingRules = bookingRuleRepository.GetBookingRuleList();

            var trxList = new List<Transaction>();
            foreach (var creditCardTransaction in creditCardTransactions)
            {
                var trx = new Transaction(bankTrx, accounts);
                trx.Value = -1 * creditCardTransaction.Amount;
                trx.BookingDate = bankTrx.BookingDate;
                trx.ValueDate = creditCardTransaction.TransactionDate;

                MatchBankTransactionByBookingRule(creditCardTransaction.Transaction, trx, bookingRules);

                if (string.IsNullOrEmpty(trx.Text))
                {
                    trx.Text = creditCardTransaction.Transaction;
                }
                trxList.Add(trx);
            }

            return trxList;
        }

        private void MatchBankTransactionByBookingRule(string transactionText, Transaction trx, List<BookingRule> bookingRules)
        {
            if (string.IsNullOrEmpty(trx.Text) == false)
                return;

            // all booking rules that match the text
            var matchedRules = bookingRules.Where(r => transactionText.ToLowerInvariant().Contains(r.LookupText.ToLowerInvariant())).ToList();

            // then match by value
            var matchedRule = matchedRules.FirstOrDefault(r => r.LookupValue == Math.Abs(trx.Value));

            // if no found, take match without a value
            if (matchedRule == null)
            {
                matchedRule = matchedRules.FirstOrDefault(r => r.LookupValue == 0);
            }
            if (matchedRule != null)
            {
                if (string.IsNullOrEmpty(trx.OriginAccountId))
                {
                    trx.OriginAccountId = matchedRule.AccountId;
                }
                else
                {
                    trx.TargetAccountId = matchedRule.AccountId;
                }

                trx.Text = matchedRule.BookingText;
            }
        }

        private void MatchBankTransactionBySameAccountsLastMonth(BankTransaction bankTransaction, Transaction trx, List<Transaction> transactions)
        {
            if (string.IsNullOrEmpty(trx.Text) == false)
                return;

            var lastMonth = trx.ValueDate.AddMonths(-1);
            var lastMonthStart = new DateTime(lastMonth.Year, lastMonth.Month, 1);
            var lastMonthEnd = lastMonthStart.AddMonths(1).AddMinutes(-1);

            // Find all bookings for the same accounts of the last month
            var lastMonthTransactions = transactions.Where(
                    t =>
                        t.OriginAccountId == trx.OriginAccountId &&
                        t.TargetAccountId == trx.TargetAccountId &&
                        Math.Abs(t.Value) == Math.Abs(trx.Value) &&
                        t.ValueDate >= lastMonthStart &&
                        t.ValueDate <= lastMonthEnd)
                .ToList();

            MatchSameOrOtherDay(trx, lastMonthTransactions);
        }

        private void MatchBankTransactionBySameValueLastMonth(BankTransaction bankTransaction, Transaction trx, List<Transaction> transactions)
        {
            if (string.IsNullOrEmpty(trx.Text) == false)
                return;

            var lastMonth = trx.ValueDate.AddMonths(-1);
            var lastMonthStart = new DateTime(lastMonth.Year, lastMonth.Month, 1);
            var lastMonthEnd = lastMonthStart.AddMonths(1).AddMinutes(-1);

            // Find all bookings for the same amount of the last month
            var lastMonthTransactions = transactions.Where(
                    t =>
                        Math.Abs(t.Value) == Math.Abs(trx.Value) &&
                        t.ValueDate >= lastMonthStart &&
                        t.ValueDate <= lastMonthEnd)
                .ToList();

            MatchSameOrOtherDay(trx, lastMonthTransactions);
        }

        private void MatchSameOrOtherDay(Transaction trx, List<Transaction> lastMonthTransactions)
        {
            if (lastMonthTransactions.Any())
            {
                var lastMonthTransaction = lastMonthTransactions.Where(
                        t =>
                            t.ValueDate.Day == trx.ValueDate.Day)
                    .FirstOrDefault();

                if (lastMonthTransaction == null)
                {
                    lastMonthTransaction = lastMonthTransactions.Where(
                            t =>
                                t.ValueDate.Day >= trx.ValueDate.AddDays(-1).Day &&
                                t.ValueDate.Day <= trx.ValueDate.AddDays(1).Day)
                        .FirstOrDefault();
                }

                if (lastMonthTransaction != null)
                {
                    trx.Text = lastMonthTransaction.Text;
                    if (string.IsNullOrEmpty(trx.OriginAccountId))
                    {
                        trx.OriginAccountId = lastMonthTransaction.OriginAccountId;
                    }
                    else
                    {
                        trx.TargetAccountId = lastMonthTransaction.TargetAccountId;
                    }
                }
            }
        }
    }
}