<?php

declare(strict_types=1);

namespace Budget;

use PDO;
use RuntimeException;

final class OnboardingService
{
    private const COLORS = [
        'Utilities' => '#49a8ff',
        'Housing' => '#8b5cf6',
        'Communications' => '#ff5b9d',
        'Subscriptions' => '#a98bff',
        'Insurance' => '#ffad5c',
        'Transportation' => '#ff6473',
        'Debt' => '#ff6473',
        'Food' => '#49e8a4',
        'Health' => '#ff5b9d',
        'Childcare' => '#ffad5c',
        'Education' => '#49a8ff',
        'TV' => '#ff5b9d',
        'Cellular' => '#49a8ff',
        'Internet' => '#49e8a4',
        'Disney+' => '#8b5cf6',
        'Netflix' => '#ff6473',
        'Luxury' => '#ffad5c',
    ];

    public function __construct(private PDO $pdo, private Settings $settings)
    {
    }

    public function hasFinancialData(): bool
    {
        $tables = [
            'monthly_plans',
            'income_entries',
            'categories',
            'budget_items',
            'transactions',
            'dead_account_entries',
        ];
        foreach ($tables as $table) {
            if ((int) $this->pdo->query('SELECT COUNT(*) FROM ' . $table)->fetchColumn() > 0) {
                return true;
            }
        }
        return false;
    }

    /**
     * @param list<array<string, mixed>> $bills
     * @param list<string> $extraCategories
     * @return array{bills:int, paid:int, categories:int, reserved:float}
     */
    public function complete(
        string $month,
        float $cash,
        array $bills,
        array $extraCategories,
        float $deadAmount
    ): array {
        if ((bool) $this->settings->get('onboarding.completed', false)) {
            throw new RuntimeException('Onboarding has already been completed.');
        }

        $month = Support::month($month);
        $cash = round($cash, 2);
        $deadAmount = round($deadAmount, 2);
        if ($cash < 0) {
            throw new RuntimeException('Current cash cannot be negative.');
        }
        if ($deadAmount < 0) {
            throw new RuntimeException('Dormant reserve cannot be negative.');
        }
        if (count($bills) > 50) {
            throw new RuntimeException('Onboarding supports up to 50 bills at a time.');
        }

        $normalizedBills = [];
        $paidTotal = 0.0;
        $deadPullTotal = 0.0;
        foreach ($bills as $index => $bill) {
            if (!is_array($bill)) {
                throw new RuntimeException('Bill ' . ($index + 1) . ' is not valid.');
            }
            $name = trim((string) ($bill['name'] ?? ''));
            $amount = round((float) ($bill['amount'] ?? 0), 2);
            $dueDate = trim((string) ($bill['due_date'] ?? ''));
            $recurrence = (string) ($bill['recurrence'] ?? 'monthly');
            $paidNow = !empty($bill['paid_now']);
            $category = trim((string) ($bill['category'] ?? ''));

            if ($name === '') {
                throw new RuntimeException('Bill ' . ($index + 1) . ' needs a name.');
            }
            if ($amount < 0) {
                throw new RuntimeException($name . ' cannot have a negative target.');
            }
            if ($paidNow && $amount <= 0) {
                throw new RuntimeException($name . ' needs an amount before it can be marked paid.');
            }
            if ($dueDate !== '' && !$this->dateIsInMonth($dueDate, $month)) {
                throw new RuntimeException($name . ' needs a due date within ' . date('F Y', strtotime($month . '-01')) . '.');
            }
            if (!in_array($recurrence, ['none', 'monthly', 'yearly'], true)) {
                $recurrence = 'monthly';
            }
            if ($category === '' || $category === '__bill__') {
                $category = $name;
            }
            if ($category === '__custom__') {
                $category = trim((string) ($bill['custom_category'] ?? ''));
            }
            if ($category === '') {
                throw new RuntimeException($name . ' needs a category.');
            }

            $deadPull = $paidNow ? $this->automaticTransactionPull($amount) : 0.0;
            if ($paidNow) {
                $paidTotal += $amount;
                $deadPullTotal += $deadPull;
            }
            $normalizedBills[] = [
                'name' => $this->truncate($name, 255),
                'amount' => $amount,
                'due_date' => $dueDate ?: null,
                'recurrence' => $recurrence,
                'paid_now' => $paidNow,
                'category' => $this->truncate($category, 191),
                'dead_pull' => $deadPull,
            ];
        }

        $availableAfterPayments = $cash - $paidTotal - $deadPullTotal;
        if ($availableAfterPayments < -0.0001) {
            throw new RuntimeException('Bills marked paid exceed the cash available right now.');
        }
        if ($deadAmount > $availableAfterPayments + 0.0001) {
            throw new RuntimeException('The dormant reserve is larger than the cash left after onboarding payments.');
        }

        $extraCategories = array_values(array_unique(array_filter(array_map(
            static fn (mixed $name): string => trim((string) $name),
            $extraCategories
        ))));

        $createdCategories = [];
        $paidCount = 0;
        $this->pdo->beginTransaction();
        try {
            $planId = $this->upsertPlan($month, $cash);

            foreach ($extraCategories as $categoryName) {
                $categoryName = $this->truncate($categoryName, 191);
                $categoryId = $this->findOrCreateCategory($categoryName);
                $createdCategories[$categoryId] = true;
            }

            foreach ($normalizedBills as $bill) {
                $categoryId = $this->findOrCreateCategory((string) $bill['category']);
                $createdCategories[$categoryId] = true;
                $seriesKey = $bill['recurrence'] === 'none' ? null : bin2hex(random_bytes(12));
                $statement = $this->pdo->prepare(
                    'INSERT INTO budget_items
                        (month, category_id, name, planned_amount, due_date, recurrence, series_key, notes)
                     VALUES
                        (:month, :category_id, :name, :planned_amount, :due_date, :recurrence, :series_key, :notes)'
                );
                $statement->execute([
                    'month' => $month,
                    'category_id' => $categoryId,
                    'name' => $bill['name'],
                    'planned_amount' => $bill['amount'],
                    'due_date' => $bill['due_date'],
                    'recurrence' => $bill['recurrence'],
                    'series_key' => $seriesKey,
                    'notes' => 'Created during onboarding',
                ]);
                $itemId = (int) $this->pdo->lastInsertId();

                if (!$bill['paid_now']) {
                    continue;
                }
                $statement = $this->pdo->prepare(
                    'INSERT INTO transactions
                        (month, budget_item_id, category_id, merchant, amount, transacted_on, dead_pull_amount, notes)
                     VALUES
                        (:month, :budget_item_id, :category_id, :merchant, :amount, :transacted_on, :dead_pull, :notes)'
                );
                $statement->execute([
                    'month' => $month,
                    'budget_item_id' => $itemId,
                    'category_id' => $categoryId,
                    'merchant' => $bill['name'],
                    'amount' => $bill['amount'],
                    'transacted_on' => date('Y-m-d'),
                    'dead_pull' => $bill['dead_pull'],
                    'notes' => 'onboarding',
                ]);
                $transactionId = (int) $this->pdo->lastInsertId();
                $paidCount++;

                if ((float) $bill['dead_pull'] > 0) {
                    $this->insertDeadEntry(
                        $month,
                        'transaction_pull',
                        (float) $bill['dead_pull'],
                        'transaction',
                        $transactionId,
                        'Automatic dormant transfer for ' . $bill['name']
                    );
                }
            }

            if ($deadAmount > 0) {
                $this->insertDeadEntry(
                    $month,
                    'manual_deposit',
                    $deadAmount,
                    'onboarding',
                    $planId,
                    'Dormant reserve created during onboarding'
                );
            }

            $this->settings->set('onboarding.completed', true);
            $this->settings->set('onboarding.completed_at', date(DATE_ATOM));
            $this->pdo->commit();
        } catch (\Throwable $exception) {
            if ($this->pdo->inTransaction()) {
                $this->pdo->rollBack();
            }
            throw $exception;
        }

        return [
            'bills' => count($normalizedBills),
            'paid' => $paidCount,
            'categories' => count($createdCategories),
            'reserved' => $deadAmount,
        ];
    }

    private function upsertPlan(string $month, float $cash): int
    {
        $statement = $this->pdo->prepare('SELECT id FROM monthly_plans WHERE month = :month');
        $statement->execute(['month' => $month]);
        $planId = $statement->fetchColumn();
        if ($planId !== false) {
            $statement = $this->pdo->prepare(
                'UPDATE monthly_plans
                 SET starting_income = :cash, rollover_in = 0, rolling_enabled = 1,
                     rollover_source_month = NULL, notes = :notes, updated_at = CURRENT_TIMESTAMP
                 WHERE id = :id'
            );
            $statement->execute([
                'cash' => $cash,
                'notes' => 'Initial balance captured during onboarding',
                'id' => $planId,
            ]);
            return (int) $planId;
        }

        $statement = $this->pdo->prepare(
            'INSERT INTO monthly_plans
                (month, starting_income, rollover_in, rolling_enabled, rollover_source_month, notes)
             VALUES
                (:month, :cash, 0, 1, NULL, :notes)'
        );
        $statement->execute([
            'month' => $month,
            'cash' => $cash,
            'notes' => 'Initial balance captured during onboarding',
        ]);
        return (int) $this->pdo->lastInsertId();
    }

    private function findOrCreateCategory(string $name): int
    {
        $statement = $this->pdo->prepare('SELECT id FROM categories WHERE LOWER(name) = LOWER(:name) LIMIT 1');
        $statement->execute(['name' => $name]);
        $id = $statement->fetchColumn();
        if ($id !== false) {
            $reactivate = $this->pdo->prepare('UPDATE categories SET active = 1 WHERE id = :id');
            $reactivate->execute(['id' => $id]);
            return (int) $id;
        }

        $statement = $this->pdo->prepare(
            'INSERT INTO categories (name, color, monthly_limit, active) VALUES (:name, :color, 0, 1)'
        );
        $statement->execute([
            'name' => $name,
            'color' => $this->categoryColor($name),
        ]);
        return (int) $this->pdo->lastInsertId();
    }

    private function categoryColor(string $name): string
    {
        if (isset(self::COLORS[$name])) {
            return self::COLORS[$name];
        }
        $palette = ['#8b5cf6', '#49a8ff', '#ff5b9d', '#49e8a4', '#ffad5c', '#ff6473'];
        return $palette[abs((int) crc32(strtolower($name))) % count($palette)];
    }

    private function automaticTransactionPull(float $amount): float
    {
        $mode = (string) $this->settings->get('dead.transaction_mode', 'fixed');
        $value = max(0, (float) $this->settings->get('dead.transaction_value', 0));
        $pull = $mode === 'percent' ? $amount * $value / 100 : $value;
        return round(min($amount, max(0, $pull)), 2);
    }

    private function insertDeadEntry(
        string $month,
        string $kind,
        float $amount,
        ?string $sourceType,
        ?int $sourceId,
        string $notes
    ): void {
        $statement = $this->pdo->prepare(
            'INSERT INTO dead_account_entries (month, kind, amount, source_type, source_id, notes)
             VALUES (:month, :kind, :amount, :source_type, :source_id, :notes)'
        );
        $statement->execute([
            'month' => $month,
            'kind' => $kind,
            'amount' => round($amount, 2),
            'source_type' => $sourceType,
            'source_id' => $sourceId,
            'notes' => $notes,
        ]);
    }

    private function dateIsInMonth(string $date, string $month): bool
    {
        if (!preg_match('/^(\d{4})-(\d{2})-(\d{2})$/', $date, $matches)) {
            return false;
        }
        return checkdate((int) $matches[2], (int) $matches[3], (int) $matches[1])
            && substr($date, 0, 7) === $month;
    }

    private function truncate(string $value, int $length): string
    {
        return function_exists('mb_substr') ? mb_substr($value, 0, $length) : substr($value, 0, $length);
    }
}