<?php
/*
 * AccountBalanceCalculator.php
 * Copyright (c) 2024 james@firefly-iii.org.
 *
 * This file is part of Firefly III (https://github.com/firefly-iii).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see https://www.gnu.org/licenses/.
 */

declare(strict_types=1);

namespace FireflyIII\Support\Models;

use Carbon\Carbon;
use FireflyIII\Models\Account;
use FireflyIII\Models\AccountBalance;
use FireflyIII\Models\Transaction;
use FireflyIII\Models\TransactionCurrency;
use FireflyIII\Models\TransactionJournal;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Log;

/**
 * Class AccountBalanceCalculator
 *
 * This class started as a piece of code to create and calculate "account balance" objects, but they
 * are at the moment unused. Instead, each transaction gets a before/after balance and an indicator if this
 * balance is up-to-date. This class now contains some methods to recalculate those amounts.
 */
class AccountBalanceCalculator
{
    private function __construct()
    {
        // no-op
    }

    /**
     * Recalculate all account and transaction balances.
     */
    public static function recalculateAll(bool $forced): void
    {
        if ($forced) {
            Transaction::whereNull('deleted_at')->update(['balance_dirty' => true]);
            // also delete account balances.
            AccountBalance::whereNotNull('created_at')->delete();
        }
        $object = new self();
        $object->optimizedCalculation(new Collection());
    }

    public static function recalculateForJournal(TransactionJournal $transactionJournal): void
    {
        Log::debug(__METHOD__);
        $object = new self();

        // recalculate the involved accounts:
        $accounts = new Collection();
        foreach ($transactionJournal->transactions as $transaction) {
            $accounts->push($transaction->account);
        }
        $object->optimizedCalculation($accounts, $transactionJournal->date);
    }

    private function getLatestBalance(int $accountId, int $currencyId, ?Carbon $notBefore): string
    {
        if (null === $notBefore) {
            return '0';
        }
        Log::debug(sprintf('getLatestBalance: notBefore date is "%s", calculating', $notBefore->format('Y-m-d')));
        $query = Transaction::leftJoin('transaction_journals', 'transaction_journals.id', '=', 'transactions.transaction_journal_id')
                            ->whereNull('transactions.deleted_at')
                            ->where('transaction_journals.transaction_currency_id', $currencyId)
                            ->whereNull('transaction_journals.deleted_at')
            // this order is the same as GroupCollector
                            ->orderBy('transaction_journals.date', 'DESC')
                            ->orderBy('transaction_journals.order', 'ASC')
                            ->orderBy('transaction_journals.id', 'DESC')
                            ->orderBy('transaction_journals.description', 'DESC')
                            ->orderBy('transactions.amount', 'DESC')
                            ->where('transactions.account_id', $accountId);
        $notBefore->startOfDay();
        $query->where('transaction_journals.date', '<', $notBefore);

        $first   = $query->first(['transactions.id', 'transactions.balance_dirty', 'transactions.transaction_currency_id', 'transaction_journals.date', 'transactions.account_id', 'transactions.amount', 'transactions.balance_after']);
        $balance = $first->balance_after ?? '0';
        Log::debug(sprintf('getLatestBalance: found balance: %s in transaction #%d', $balance, $first->id ?? 0));

        return $balance;
    }

    private function getAccountBalanceByAccount(int $account, int $currency): AccountBalance
    {
        $query = AccountBalance::where('title', 'balance')->where('account_id', $account)->where('transaction_currency_id', $currency);

        $entry = $query->first();
        if (null !== $entry) {
            // Log::debug(sprintf('Found account balance "balance" for account #%d and currency #%d: %s', $account, $currency, $entry->balance));

            return $entry;
        }
        $entry                          = new AccountBalance();
        $entry->title                   = 'balance';
        $entry->account_id              = $account;
        $entry->transaction_currency_id = $currency;
        $entry->balance                 = '0';
        $entry->save();
        // Log::debug(sprintf('Created new account balance for account #%d and currency #%d: %s', $account, $currency, $entry->balance));

        return $entry;
    }

    private function optimizedCalculation(Collection $accounts, ?Carbon $notBefore = null): void
    {
        Log::debug('start of optimizedCalculation');
        if ($accounts->count() > 0) {
            Log::debug(sprintf('Limited to %d account(s)', $accounts->count()));
        }
        // collect all transactions and the change they make.
        $balances = [];
        $count    = 0;
        $query    = Transaction::leftJoin('transaction_journals', 'transaction_journals.id', '=', 'transactions.transaction_journal_id')
                               ->whereNull('transactions.deleted_at')
                               ->whereNull('transaction_journals.deleted_at')
            // this order is the same as GroupCollector, but in the exact reverse.
                               ->orderBy('transaction_journals.date', 'asc')
                               ->orderBy('transaction_journals.order', 'desc')
                               ->orderBy('transaction_journals.id', 'asc')
                               ->orderBy('transaction_journals.description', 'asc')
                               ->orderBy('transactions.amount', 'asc');
        if ($accounts->count() > 0) {
            $query->whereIn('transactions.account_id', $accounts->pluck('id')->toArray());
        }
        if (null !== $notBefore) {
            $notBefore->startOfDay();
            $query->where('transaction_journals.date', '>=', $notBefore);
        }

        $set = $query->get(['transactions.id', 'transactions.balance_dirty', 'transactions.transaction_currency_id', 'transaction_journals.date', 'transactions.account_id', 'transactions.amount']);

        // the balance value is an array.
        // first entry is the balance, second is the date.

        /** @var Transaction $entry */
        foreach ($set as $entry) {
            // start with empty array:
            $balances[$entry->account_id]                                  ??= [];
            $balances[$entry->account_id][$entry->transaction_currency_id] ??= [$this->getLatestBalance($entry->account_id, $entry->transaction_currency_id, $notBefore), null];

            // before and after are easy:
            $before = $balances[$entry->account_id][$entry->transaction_currency_id][0];
            $after  = bcadd($before, $entry->amount);
            if (true === $entry->balance_dirty || $accounts->count() > 0) {
                // update the transaction:
                $entry->balance_before = $before;
                $entry->balance_after  = $after;
                $entry->balance_dirty  = false;
                $entry->saveQuietly(); // do not observe this change, or we get stuck in a loop.
                ++$count;
            }

            // then update the array:
            $balances[$entry->account_id][$entry->transaction_currency_id] = [$after, $entry->date];
        }
        Log::debug(sprintf('end of optimizedCalculation, corrected %d balance(s)', $count));
        // then update all transactions.

        // save all collected balances in their respective account objects.
        $this->storeAccountBalances($balances);
    }

    private function getAccountBalanceByJournal(string $title, int $account, int $journal, int $currency): AccountBalance
    {
        $query = AccountBalance::where('title', $title)->where('account_id', $account)->where('transaction_journal_id', $journal)->where('transaction_currency_id', $currency);

        $entry = $query->first();
        if (null !== $entry) {
            return $entry;
        }
        $entry                          = new AccountBalance();
        $entry->title                   = $title;
        $entry->account_id              = $account;
        $entry->transaction_journal_id  = $journal;
        $entry->transaction_currency_id = $currency;
        $entry->balance                 = '0';
        $entry->save();

        return $entry;
    }

//    private function recalculateLatest(?Account $account): void
//    {
//        $query  = Transaction::groupBy(['transactions.account_id', 'transactions.transaction_currency_id', 'transactions.foreign_currency_id']);
//
//        if (null !== $account) {
//            $query->where('transactions.account_id', $account->id);
//        }
//        $result = $query->get(['transactions.account_id', 'transactions.transaction_currency_id', 'transactions.foreign_currency_id', \DB::raw('SUM(transactions.amount) as sum_amount'), \DB::raw('SUM(transactions.foreign_amount) as sum_foreign_amount')]);
//
//        // reset account balances:
//        $this->resetAccountBalancesByAccount('balance', $account);
//
//        /** @var \stdClass $row */
//        foreach ($result as $row) {
//            $account             = (int) $row->account_id;
//            $transactionCurrency = (int) $row->transaction_currency_id;
//            $foreignCurrency     = (int) $row->foreign_currency_id;
//            $sumAmount           = (string) $row->sum_amount;
//            $sumForeignAmount    = (string) $row->sum_foreign_amount;
//            $sumAmount           = '' === $sumAmount ? '0' : $sumAmount;
//            $sumForeignAmount    = '' === $sumForeignAmount ? '0' : $sumForeignAmount;
//
//            // at this point SQLite may return scientific notation because why not. Terrible.
//            $sumAmount           = app('steam')->floatalize($sumAmount);
//            $sumForeignAmount    = app('steam')->floatalize($sumForeignAmount);
//
//            // first create for normal currency:
//            $entry               = $this->getAccountBalanceByAccount($account, $transactionCurrency);
//
//            try {
//                $entry->balance = bcadd((string) $entry->balance, $sumAmount);
//            } catch (\ValueError $e) {
//                $message = sprintf('[a] Could not add "%s" to "%s": %s', $entry->balance, $sumAmount, $e->getMessage());
//                Log::error($message);
//
//                throw new FireflyException($message, 0, $e);
//            }
//            $entry->save();
//
//            // then do foreign amount, if present:
//            if ($foreignCurrency > 0) {
//                $entry = $this->getAccountBalanceByAccount($account, $foreignCurrency);
//
//                try {
//                    $entry->balance = bcadd((string) $entry->balance, $sumForeignAmount);
//                } catch (\ValueError $e) {
//                    $message = sprintf('[b] Could not add "%s" to "%s": %s', $entry->balance, $sumForeignAmount, $e->getMessage());
//                    Log::error($message);
//
//                    throw new FireflyException($message, 0, $e);
//                }
//                $entry->save();
//            }
//        }
//        Log::debug(sprintf('Recalculated %d account balance(s)', $result->count()));
//    }

//    private function resetAccountBalancesByAccount(string $title, ?Account $account): void
//    {
//        if (null === $account) {
//            $count = AccountBalance::whereNotNull('updated_at')->where('title', $title)->update(['balance' => '0']);
//            Log::debug(sprintf('Set %d account balance(s) to zero.', $count));
//
//            return;
//        }
//        $count = AccountBalance::where('account_id', $account->id)->where('title', $title)->update(['balance' => '0']);
//        Log::debug(sprintf('Set %d account balance(s) of account #%d to zero.', $count, $account->id));
//    }

//    /**
//     * Als je alles opnieuw doet, verzamel je alle transactions en het bedrag en zet je dat neer als "balance after
//     * journal". Dat betekent, netjes op volgorde van datum en doorrekenen.
//     *
//     * Zodra je een transaction journal verplaatst (datum) moet je dat journal en alle latere journals opnieuw doen.
//     * Maar dan moet je van de account wel een beginnetje hebben, namelijk de balance tot en met dat moment.
//     *
//     *  1. Dus dan search je eerst naar die SUM, som alle transactions eerder dan (niet inclusief) de journal.
//     *  2. En vanaf daar pak je alle journals op of na de journal (dus ook de journal zelf) en begin je door te tellen.
//     *  3. Elke voorbij gaande journal entry "balance_after_journal" geef je een update of voeg je toe.
//     */
//    private function recalculateJournals(?Account $account, ?TransactionJournal $transactionJournal): void
//    {
//        $query   = Transaction::groupBy(['transactions.account_id', 'transaction_journals.id', 'transactions.transaction_currency_id', 'transactions.foreign_currency_id']);
//        $query->leftJoin('transaction_journals', 'transaction_journals.id', '=', 'transactions.transaction_journal_id');
//        $query->orderBy('transaction_journals.date', 'asc');
//        $amounts = [];
//        if (null !== $account) {
//            $query->where('transactions.account_id', $account->id);
//        }
//        if (null !== $account && null !== $transactionJournal) {
//            $query->where('transaction_journals.date', '>=', $transactionJournal->date);
//            $amounts = $this->getStartAmounts($account, $transactionJournal);
//        }
//        $result  = $query->get(['transactions.account_id', 'transaction_journals.id', 'transactions.transaction_currency_id', 'transactions.foreign_currency_id', \DB::raw('SUM(transactions.amount) as sum_amount'), \DB::raw('SUM(transactions.foreign_amount) as sum_foreign_amount')]);
//
//        /** @var \stdClass $row */
//        foreach ($result as $row) {
//            $account                                 = (int) $row->account_id;
//            $transactionCurrency                     = (int) $row->transaction_currency_id;
//            $foreignCurrency                         = (int) $row->foreign_currency_id;
//            $sumAmount                               = (string) $row->sum_amount;
//            $sumForeignAmount                        = (string) $row->sum_foreign_amount;
//            $journalId                               = (int) $row->id;
//
//            // check for empty strings
//            $sumAmount                               = '' === $sumAmount ? '0' : $sumAmount;
//            $sumForeignAmount                        = '' === $sumForeignAmount ? '0' : $sumForeignAmount;
//
//            // new amounts:
//            $amounts[$account][$transactionCurrency] = bcadd($amounts[$account][$transactionCurrency] ?? '0', $sumAmount);
//            $amounts[$account][$foreignCurrency]     = bcadd($amounts[$account][$foreignCurrency] ?? '0', $sumForeignAmount);
//
//            // first create for normal currency:
//            $entry                                   = self::getAccountBalanceByJournal('balance_after_journal', $account, $journalId, $transactionCurrency);
//            $entry->balance                          = $amounts[$account][$transactionCurrency];
//            $entry->save();
//
//            // then do foreign amount, if present:
//            if ($foreignCurrency > 0) {
//                $entry          = self::getAccountBalanceByJournal('balance_after_journal', $account, $journalId, $foreignCurrency);
//                $entry->balance = $amounts[$account][$foreignCurrency];
//                $entry->save();
//            }
//        }
//
//        // select transactions.account_id, transaction_journals.id, transactions.transaction_currency_id, transactions.foreign_currency_id, sum(transactions.amount), sum(transactions.foreign_amount)
//        //
//        // from transactions
//        //
//        // left join transaction_journals ON transaction_journals.id = transactions.transaction_journal_id
//        //
//        // group by account_id, transaction_journals.id, transaction_currency_id, foreign_currency_id
//        // order by transaction_journals.date desc
//    }

//    private function getStartAmounts(Account $account, TransactionJournal $journal): array
//    {
//        exit('here we are 1');
//
//        return [];
//    }


    private function storeAccountBalances(array $balances): void
    {
        /**
         * @var int   $accountId
         * @var array $currencies
         */
        foreach ($balances as $accountId => $currencies) {
            /** @var Account $account */
            $account = Account::find($accountId);
            if (null === $account) {
                Log::error(sprintf('Could not find account #%d, will not save account balance.', $accountId));
                continue;
            }

            /**
             * @var int   $currencyId
             * @var array $balance
             */
            foreach ($currencies as $currencyId => $balance) {
                /** @var TransactionCurrency $currency */
                $currency = TransactionCurrency::find($currencyId);
                if (null === $currency) {
                    Log::error(sprintf('Could not find currency #%d, will not save account balance.', $currencyId));
                    continue;
                }
                /** @var AccountBalance $object */
                $object          = $account->accountBalances()->firstOrCreate(['title' => 'running_balance', 'balance' => '0', 'transaction_currency_id' => $currencyId, 'date' => $balance[1]]);
                $object->balance = $balance[0];
                $object->date    = $balance[1];
                $object->save();
            }
        }
    }
}